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Nuclear Physics NewsVolume 18/No. 3

Vol. 18, No. 3, 2008, Nuclear Physics News 1

Nuclear Physics News is published on behalf of the Nuclear Physics European Collaboration Committee (NuPECC), an Expert Committee of the EuropeanScience Foundation, with colleagues from Europe, America, and Asia.

Editor: Gabriele-Elisabeth Körner

Editorial BoardT. Bressani, Torino S. Nagamiya, TsukubaR. F. Casten, Yale A. Shotter, VancouverP.-H. Heenen, Brussels (Chairman) H. Ströher, Jülich, JülichJ. Kvasil, Prague T. J. Symons, BerkeleyM. Lewitowicz, Ganil Caen C. Trautmann, Darmstadt

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CorrespondentsArgentina: O. Civitaresse, La Plata; Australia: A. W. Thomas, Adelaide; Austria: H. Leeb, Vienna; Belgium:G. Neyens, Leuven; Brasil: M. Hussein, São Paulo; Bulgaria: D. Balabanski, Sofia; Canada: J.-M. Poutissou,TRIUMF; K, Sharma, Manitoba; C. Svensson, Guelph: China: W. Zhan, Lanzhou; Croatia: R. Caplar, Zagreb; CzechRepublic: J. Kvasil, Prague; Slovak Republic: P. Povinec, Bratislava; Denmark: K. Riisager, Århus; Finland: M. Leino,Jyväskylä; France: G. De France, GANIL Caen; M. MacCormick, IPN Orsay; Germany: K. Langanke, GSI Darmstadt;U. Wiedner, Bochum; Greece: E. Mavromatis, Athens; Hungary: B. M. Nyakó, Debrecen; India: D. K. Avasthi, NewDelhi; Israel: N. Auerbach, Tel Aviv; Italy: M. Ripani, Genova; L. Corradi, Legnaro; Japan: T. Motobayashi, RIKEN;Mexico: J. Hirsch, Mexico DF; Netherlands: G. Onderwater, KVI Groningen; T. Peitzmann, Utrecht; Norway: J. Vaagen,Bergen; Poland: B. Fornal, Cracow; Portugal: M. Fernanda Silva, Sacavém; Romania: V. Zamfir, Bucharest;Russia: Yu. Novikov, St. Petersburg; Serbia: S. Jokic, Belgrade; South Africa: S. Mullins, Capa Town Spain:B. Rubio, Valencia; Sweden: J. Nyberg, Uppsala; Switzerland: K. Kirch, PSI Villigen; United Kingdom: P. Regan,Surrey; USA: D. Geesaman, Argonne; D. W. Higinbotham, Jefferson Lab; M. Thoenessen, Michigan State Univ.; H. G. Ritter,Lawrence Berkeley Laboratory; G. Miller, Seattle.

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NuclearPhysics

News

2 Nuclear Physics News, Vol. 18, No. 3, 2008

Cover illustration: The PRISMA CLARA setup at Legnaro-see article on page 5.

Volume 18/No. 3

Contents

Editorial .............................................................................................................................................................. 3

Laboratory PortraitThe Legnaro National Laboratories of INFN

by Giacomo de Angelis .................................................................................................................................... 5

Feature ArticleWhat Can Neutrinos Tell Us about the Earth?

by Nikolai R. Tolich ....................................................................................................................................... 14

Facilities and MethodsEURISOL High Power Targets

by Yacine Kadi, Jacques Lettry, Mats Lindroos, Danas Ridikas, Thierry Stora, and Luigi Tecchio............ 19

A New 6MV Accelerator Mass Spectrometer for the University of Cologneby Alfred Dewald, Jan Jolie, and Andreas Zilges ......................................................................................... 26

Impact and ApplicationsMasses of Short-Lived Nuclides: Precision Measurement Techniques and Applications

by Klaus Blaum, Yuri A. Litvinov, and Lutz Schweikhard.............................................................................. 29

Meeting Reports

The First Workshop on the “State of the Art in Nuclear Cluster Physics”by Christian Beck, Marianne Dufour, and Peter Schuck ............................................................................... 35

The Halo 08 Workshop, Held at TRIUMF, Vancouver, Canadaby G. W. F. Drake, H. Geissel, W. Mittig, A. Richter, and I. Tanihata .......................................................... 36

N=52: A New Magic Number?by Ulli Köster and Gary Simpson................................................................................................................... 38

Prof. Yuri Oganessian (on His Seventy-Fifth Birthday)by Sergey Sidorchuk ....................................................................................................................................... 39

News and Views ................................................................................................................................................ 40

News from NuPECC ........................................................................................................................................ 41

Obituary ............................................................................................................................................................ 43

Calendar ............................................................................................................................................................ 44

editorial


The views expressed here do not represent the views and policies of NuPECC except where explicitly identified.

Editorial

Advances in precision cosmol-ogy, neutrino physics, and atomicand condensed matter physics havegrabbed the headlines over the pastcouple of decades. A less publicizedadvance over the same period, whichis nonetheless astonishing, has beenthe reinvention of nuclear theory.When I was a graduate student in theearly 1980s, nuclear physics seemedto be lacking in the theoretical toolsrequired to go beyond a qualitativedescription of the complexities ofstrongly interacting many-body phys-ics. Too much was being asked ofthe Nambu Jona-Lasinio model, thequark model, the bag model, and soon. Solving the Schrödinger equa-tion for light nuclei, or the shellmodel for heavier nuclei was beyondthe reach of existing computationalresources. The previous decade hadwitnessed the precise formulation ofQuantum Chromodynamics (QCD),and the disconnect between nucleartheory and the underlying theory ofthe strong interactions was striking.Furthermore, rather than borrowingfreely from related fields of research,nuclear physics drifted in the dol-drums of a tedious preoccupation withthe sociological boundaries of thefield: whether, for example, the prop-erties of a single nucleon could becalled nuclear physics or not, and wor-thy of support.

Being director of the Institute forNuclear Theory (INT) has given mea front row seat to witness to whatextent nuclear theory has changedsince then. Last summer the INThosted a summer school on lattice

QCD, where students could calcu-late hadron masses on their laptopsand heard about ongoing researchinto nucleon–hyperon interactionson the lattice; this summer nuclearand atomic physicists are meetingwith chemists to discuss clusteralgorithms in computational many-body theory; we recently organizeda program on applications of stringtheory to QCD, such as models forjet quenching in heavy ion colli-sions. In a typical year at the INTone can hear seminars on suchamazingly diverse topics as theimplications of observed seismicmodes in neutron stars, how spectro-scopic regularity arises from under-lying chaotic dynamics, or theresults of a high precision effectivefield theory calculation for neu-trino–matter interactions.

There has been a wholesalereplacement of the old heuristicmodels by precision calculations,while on the advancing frontiers ofthe field completely new modelshave been developed to describephenomena for which there is yetlittle theory. In place of the NJL andquark models there are sophisticatedcalculations in perturbative QCD,lattice QCD, and chiral perturbationtheory. In areas of physics wherepreviously theory had no traction,the new models include AdS/QCD,currently a cutting edge model forrelativistic plasma physics; colorsuperconductivity, which has changedthe paradigm for dense quark mat-ter; and the color glass condensate,which has redefined how one thinks

about the initial state in relativisticheavy ion collisions.

While nuclear physics used tocomprise of theory and experiment,a third sub-discipline has emerged:computational nuclear physics. Rad-ical change in nuclear theory isbeing brought about by the inexora-ble improvements of computersunder the thrall of Moore’s law. Wehave entered the age of the petaflopscomputer and it is suddenly possibleto investigate numerically from firstprinciples a host of complex phe-nomena. Lattice QCD is currentlyable to compute meson properties atthe 1% accuracy level, while multi-nucleon calculations are beginningto be pursued. In nuclear structure,ab initio calculations up to carbonare possible, and shell model anddensity functional techniques arebeing calibrated and applied withgrowing accuracy across the entireperiodic table. Computationalnuclear physics is similar to experi-mental physics in that it involvescollaborations using large expen-sive facilities, and entails rigorousdata analysis; yet at the same time itrequires intensive theoretical andalgorithmic developments to be ofuse, such as effective field theoryfor lattice physics, or the no-coreshell model and density functionaltheory developments for nuclearstructure calculations.

Nuclear theorists are now hap-pily disregarding artificial intellectualboundaries and are appropriating whatthey need to get the job done, findinginspiration and intersections with

editorial


research in fields as far flung asneutrino physics, quantum dots, solarphysics, extra dimensions, graphene,cosmic rays, and trapped atoms.

In the United States the nuclearphysics community recently deviseda long-range plan to map out the

future of the field; although such aplan is a useful budgeting tool,nuclear theorists are aiming to ren-der that document obsolete at theearliest possible moment—as youwould expect in a vibrant anddynamic field.

DAVID B. KAPLAN

Institute for Nuclear Theory

laboratory portrait


The Legnaro National Laboratories of INFN

Overview The Legnaro National Laboratories

(LNL) are a research center that housesa system of ion sources, accelerators,and target stations dedicated to basicand applied research. LNL is one of thefour national user facilities provided bythe Istituto Nazionale di Fisica Nuclearein Italy, committed to support a highquality research program developed byoutside users as well as by staff mem-bers. It is a European research infra-structure providing access to outsideusers within the EC contract EURONSRII3-CT-2004-506065.

The research program involvesmore then 400 scientists from all overthe world, technical staff, and stu-dents. The primary research empha-sis is on nuclear physics, usingaccelerated heavy-ion beams, and onapplication of the nuclear physicstechnologies. Moreover, the labora-tory supports research in basic interac-tions, gravitational waves, acceleratorphysics, energetics, material science,biology, medicine, and radiationeffects on materials. It also partici-pates with different contributions tonumerous projects hosted in other lab-oratories all over the world. The his-tory and previous results of LNL canbe found in a previous issue ofNuclear Physics News [1]. Thepresent laboratory portrait describesthe more recent achievements.

The Accelerator Complex The LNL accelerator complex

consists of a Tandem XTU, a super-conductive linac called ALPI, a super-conductive radiofrequency quadrupole(RFQ) called PIAVE, and two electro-static accelerators. The maximum

voltage of the Tandem is 16MV even ifroutine operation is carried on with avoltage not exceeding 15MV. TheTandem can operate in stand alonemode or as an injector of the supercon-ductive linac ALPI. It has so far deliv-ered beams to the experimental areasfor about 5,000 hours per year. A largefraction (50%) of this beam time hasbeen used for injection into the linac.

ALPI is a linac for heavy ionsoperating at LNL since 1994. It con-sists of an array of 70 superconductivequarter wave resonators (QWRs)accelerating beams from C to U atenergies around the Coulomb barrier.The low b section is equipped withbulk Nb cavities whereas sputtered Nbon Cu QWRs are installed in the highand medium b sections. The use of Nbfor these resonators allows operationat an average accelerating field higherthan 4.4 MV/m. The total ALPIequivalent voltage is about 50 MV. Alarge variety of beams has been accel-erated to and above the Coulomb bar-rier, the heaviest so far being 136Xe.

To overcome the limitationsimposed by the use of the Tandem asan injector for the linac both for the ionmass (A≤ 100) and for the beam cur-rent (I≤10–20 pnA) a positive ioninjector (PIAVE) was commissioned in2005 and became operational in 2006.

PIAVE consists of an ECR ionsource on a 350 kV platform, twosuperconductive RFQs (with a massover charge state ratio A/q = 8.5), andeight superconducting QWRs. Pres-ently beams of 20Ne, 40Ar, and 136Xehave been accelerated by the newinjector. The combined operation ofthe PIAVE positive ion injector andALPI can provide beams up to100 pnA for most ions even though the

present available current on target isconstrained by authorization limits(30 pnA and 20 MV/m for ions heavierthan Si and 2 pnA and 26 MV/m forlight ions (from C to Al)).

The other two electrostatic acceler-ators routinely in operation are VanDer Graaff of 2 and 7 MV, mainlyused for nuclear physics and interdis-ciplinary applications as well as a neu-tron source.

The Physics of Nuclei—Background and Current Research

Since 1982, the research activity atLNL, developed in close collaborationwith other universities and researchcenters at an international level, wasfocused on the 15 MV XTU Tandem.Nuclear reaction studies as well asnuclear structure studies based on highresolution gamma-ray spectroscopywere strongly boosted by the construc-tion of several dedicated instruments.Forefront instrumentation has beendeveloped at LNL as the 4p chargedparticle detectors for reaction studies(8∏LP and GARFIELD), the recoilmass spectrometers (RMS andPRISMA) and the g-ray detectorarrays (GASP, EUROBALL, andCLARA). Most of those devices havebeen described in Ref. [1]. A recentachievement has been the constructionof the PRISMA-CLARA set-up.PRISMA [2] is a magnetic spectrome-ter of large angular (~80 msr) andenergy (±20%) acceptance, consistingof a quadrupole singlet followed by adipole magnet. The measurement ofthe positions of the incoming ions atthe entrance and at the focal plane ofthe spectrometer, of the time of flightand of the energy loss and total energy

laboratory portrait


allows the identification of the atomicnumber Z, of the mass A and of thevelocity vector. Gamma rays in coin-cidence with the reaction products aredetected by the CLARA Ge detectorarray [3], composed of 25 cloverdetectors and covering a solid angle ofalmost 1p.

Current research areas include thestudy of the structure of nuclei at

medium and large angular momenta,the existence of cluster structure innuclei and other aspects of correlatedstates, hyperfine interaction and fieldsand related application to nuclear struc-ture, studies of fusion and fusion fis-sion of heavy nuclei, as well asfragmentation and multi-nucleon trans-fer studies. Applications of nuclearmethods are routinely performed

mainly at the small accelerators such aselement analysis using light and heavyions. Some aspects of these will bediscussed later in the article. Most ofthese projects are to some extent col-laborative, linking in to experimentalstudies on other facilities. They involvecolleagues from other Italian universi-ties and institutions as well as frommany other countries.

Nuclear Structure at High-Angular Momentum

Through the response of thenucleus to the rotational stress one caninvestigate a wide variety of nuclearstructure phenomena showing the dif-ferent facets of a finite fermionic sys-tem. The stabilization of very exoticshapes at high angular momentum notonly provides unique information onthe detailed structure of the nuclearpotential but also allows one to inferthe underlying symmetries characteriz-ing the dynamical system. A number ofsymmetry realizations characterize thenuclear–many body problem, going allthe way from the initial isospin classifi-cation scheme of nucleons in 1932 byHeisenberg, to recent discussions oncritical-point symmetries in studyingnuclear-physics transitions. Breakingof the rotational symmetry can berelated to asymmetries in charge (likein macroscopic objects) or in current(only quantal) distributions.

For particular choices of the nuclearpotential energy surface in the collec-tive (b,g)-plane, exact solutions to theBohr-Mottelson model have beenobtained (called X(5) and E(5) critical-point symmetries). The electromag-netic transition matrix elements, astrong signature of the presence of suchsymmetries, have been studied at LNLusing the GASP array and the ColognePlunger device [4]. The high sensitivity

Figure 1. Electromagnetic transition matrix elements can probe chiralsymmetry. Experimentally determined (upper panels) and theoreticallycalculated (middle panels: Two Quasiparticle Triaxial Rotor Model (TQPTR),bottom panels: Interacting Boson Fermion Fermion Model (IBFFM)) B(E2) andB(M1) values for the inband gamma transitions in 134Pr. The different behaviorobserved between the experimental results and the prediction of the TQPTRmodel has brought the concept of dynamical chirality in nuclear systems. Datahave been collected in several experiments at IRES (Strasbourg) and LNL.

laboratory portrait


of the GASP and EUROBALL detec-tor array allowed the study of themechanism causing the abrupt transi-tion from a superdeformed potentialminimum to an almost spherical one inthe A~130 mass region. Very elon-gated shapes have been investigated inlight nuclei. The most exotic examplesinvolve chains of several alpha parti-cles [5]. Their existence is deducedmainly from the observation of reso-nance’s in binary reaction channels.

An important field of research atLNL has been related to the discoveryof rotational-like structure in spheri-cal nuclei (shears bands). Here mostof the angular momentum of thenucleus is generated by just a few ofthe protons and neutrons, whose cou-pling is governed by the overlap ofthe wavefunctions that represent thedistribution of nucleon density in thenucleus. Their configuration can bethought of as an anisotropic arrange-ment of crossed “current” loopsembedded in the spherical mass distri-bution of the nucleus. A related topicis the spontaneous chiral symmetrybreaking, which has been discoveredin odd-odd nuclei having triaxialshapes. It is induced by configura-tions where the angular momenta ofthe valence proton, the valence neu-tron, and the core rotation are mutu-ally perpendicular. Such angularmomenta can form a left- and a right-handed system, related by the chiraloperator, which combines time reversaland rotation by 180°. Spontaneouschiral symmetry breaking in thebody-fixed frame is manifested inthe laboratory-frame as degeneratedoublet of �I = 1 bands. Recentexperiments at LNL and IRESStrasbourg have shown that chiralityin nuclear systems is mainly adynamical effect where fluctuationsin the shape of the nucleus play a

crucial role [6]. Figure 1 shows thetransition matrix elements (B(E2) andB(M1)) for electromagnetic transi-tions de-exciting states in the chiralbands of 134Pr. The comparison of theresults with the prediction of theoreti-cal models indicates the dynamicalnature of such quantum fluctuations.

Nuclear Structure at the Limits of the Isotopic Spin

The most critical ingredients indetermining the predicted properties of

a nucleus from a given effective interac-tion is the overall number of nucleonsand the ratio N/Z of neutrons to protons.It is the extremes in these quantities thatdefine the limits of existence for nuclearmatter that will be opened up for studyby the second generation radioactivebeam accelerators as well as by the useof high intensity stable beams. At LNLthe study of the role of the proton-neu-tron pairing has been actively pursuedin N = Z nuclei providing new insightinto the properties of the mean field of

Figure 2. Left panel: Identification of the excited states in 54Ni in a 2nevaporation channel. a) The gamma ray spectrum in coincidence with twoneutrons and in anticoincidence with charged particles (dashed line) issuperimposed on that in coincidence with two neutrons and any chargedparticles. It shows clearly the characteristic γ-transitions of the 54Ni nucleus. b)Gamma coincidence spectrum and c) asymmetry ratios for the gammatransitions in 54Ni. Right panel: Mirror energy difference for A = 54 nucleimeasured and calculated (shell model). Such comparison shows the importanceof the nuclear isospin breaking component of the interaction. Data from theEuroball spectrometer are taken at IRES Strasbourg and LNL.

laboratory portrait


nuclear systems far from stability. Alsothe degree of validity of the isospinsymmetry is a subject widely investi-gated at LNL. Although the symmetryis already broken, to some extent, at thelevel of strong interaction and, to amuch larger extent, by electromagneticforces, the isospin formalism remains avery powerful tool to relate the proper-ties of corresponding levels in differentnuclei, from which complementaryinformation can be derived on the struc-ture of the nuclear wave function. Theenergy differences of analog statesalong rotational bands in mirror nuclei(mirror energy differences (MED))have been investigated in the last fewyears in the f7/2 shell and for heaviernuclei. By resorting to large scale shellmodel calculations, that reproduce verywell the experimental findings, themechanism of the backbending in rotat-ing mirror nuclei has been inferred fromMED and explained in terms of the

alignment of like-nucleon pairs (Figure2; [7]). It has been also shown recentlythat MED give information on the evo-lution of nuclear radii along the yrastbands, providing direct evidence forcharge symmetry breaking of thenuclear field and making visible otherelectromagnetic components of theinteraction as, for example, the electro-magnetic spin orbit term [8–10].

Also, the size of the isospin mixingin low energy nuclear states has beenrecently determined in the mass A~60region through the precise measure-ment of the strength of isospin forbid-den E1 transitions in the N =Z = 32nucleus. An interesting possibilitypresently under study is the measure-ment of the E1 rates in mirror nuclei.Here, unlike the N = Z case, the isovec-tor amplitude is different from zero andthe difference between the mirror E1strengths comes out from the interfer-ence between the induced isoscalarterm and the isovector term.

Magic numbers are fundamentalquantities in nuclear structure; they

have been determined on the basis ofexperimental information of nuclei onor near the valley of b-stability. Thequestion has been recently raised abouttheir validity far from the stability line.For large neutron excess the softeningof the Woods-Saxon shape of theneutron potential is expected to cause areduction of the spin-orbit interactionand therefore a migration of the high-lorbitals with a large impact on the shellstructure of nuclei far from stability. Adifferent scenario has been recentlysuggested where the evolution of theshell structure, in going from stable toexotic nuclei, can be related to theeffect of the tensor part of the nucleon–nucleon interaction. To probe sucheffects neutron-rich nuclei have beenpopulated at LNL by means of deep-inelastic and multi-nucleon transferreactions [11–13]. The characteristic gdecay has been studied by thePRISMA-CLARA set-up. Figure 3shows the mass distribution obtainedfor every Z after selection in PRISMA.Large data sets have been recently

Figure 3. Mass distribution obtainedafter Z selection at the PRISMAspectrometer for the 82Se+ 238Ureaction at 505 MeV.

Figure 4. Differential Plunger Method applied to the excited states of 46Ca.Partial γ-ray spectra in coincidence with the 46Ca reaction product for threetarget-degrader distances. One notices the two components of the 2+ ® 0+ γtransition of 46Ca corresponding to the γ emission at two different velocitiesof the source.

laboratory portrait


collected for nuclei close to the N = 28,32, 34, 40, 50, and 82 shell closures.New experimental information hasbeen obtained on the exited levels of awide range of nuclei. The excited statesof the N = 50 isotones, extended downto Z= 31, and of the Z= 29 isotopes,extended up to N= 45, have been usedto test the predictions of the shell evo-lution based on the effects of the tensorinteraction as well as of the differenteffective interactions [11]. Importantexperimental information is providedby the determination of the electromag-netic transition matrix elements. Theirbehavior is a direct probe of the evolu-tion of the shell structure far fromstability. A new method to measurelifetimes based on the DifferentialPlunger technique applied to multi-nucleon transfer and deep-inelasticreactions has been recently pioneeredat LNL. It consists in measuring the gde-excitation of an excited level at twodifferent recoil velocities obtainedinserting a degrader on the trajectory ofthe recoiling ions before entering thespectrometer. Very promising results

have been recently obtained for neutronrich nuclei in the A= 50 mass region(see Figure 4; [14]).

Heavy-Ion Sub-Barrier Fusion The study of heavy-ion fusion

near the Coulomb barrier is a relevantresearch topics at LNL. Sub-barrier

fusion cross sections are generallydominated by strong couplings tonuclear shape vibrations, deforma-tions and, possibly, nucleon transferdegrees of freedom. The method ofextracting fusion barrier distributionsfrom the second energy derivative ofthe fusion excitation function hasbeen a major breakthrough inunderstanding the kind of couplingsinvolved in the various cases, thusclarifying the intimate links betweennuclear structure and reaction dynam-ics. In a series of experiments per-formed at LNL the effects of thedifferent excitation modes of the pro-jectile and target were revealed for anumber of systems. Recent examplesare shown in Figure 5, reporting, onthe left, the fusion excitation func-tions for several Ca + Zr systems and,on the right, the deduced fusion bar-rier distributions. The differentbehaviors are nice examples of thedominant influence of the coupling tolow-lying inelastic excitations and tonucleon transfers [15]. One maynotice that these results have interest-ing implications on the optimization

Figure 5. Fusion excitation functions (left) and fusion barrier distributions(right) as a function of the energy for the indicated systems.

Figure 6. Total cross-sections for pure neutron pick-up channels in the90Zr+ 208Pb reaction (left panel). Total cross-sections for pure neutron pick-up(right panel) and one-proton stripping (central panel) channels in the40Ca+ 96Zr reaction. The points are the experimental data and the histogramsare the calculation performed with the code GRAZING.

laboratory portrait


of fusion processes leading to specificcompound nuclei. The particularchoice of target and projectile withspecific structures can determinesmall shifts in the barriers with orderof magnitude effects on the cross-sections in sub-barrier fusion.

Multi-Nucleon Transfer Reactions As already discussed multi-nucleon

transfer reactions at Coulomb barrierenergies is an important field ofresearch in low-energy heavy-ion phys-ics, which has been extensively studiedat LNL (see Ref. [16] for recentreviews) with the time-of-flight spec-trometer PISOLO [1] and, morerecently, with the magnetic spectrome-ter PRISMA [2]. Open questions con-cern the relevant degrees of freedomacting in the transfer process, that is,single nucleon, pair, or even clustertransfer modes. For a quantitativeunderstanding of these processes, A,Z, and Q-value distributions, and dif-ferential and total cross-sections forthe binary reaction products of many

systems have been measured and com-pared with state-of-the-art calculations,including surface degrees of freedomand single and multiple transfer of bothneutrons and protons. As an example ofthe reached quality of agreement ininclusive data, the total yields for thepure neutron transfer channels areshown in Figure 6 for the reactions40Ca+ 96Zr and 90Zr+ 208Pb systems[17], together with the yield of the one-proton stripping channel for the40Ca+ 96Zr. The data are compared witha semi-classical calculation using thecode GRAZING. The additional g-decay information obtained with thePRISMA + CLARA array has madepossible to extract the populationstrength to specific final states of trans-fer products. The comparison of theexperimental strengths with calcula-tions has provided information on pair-ing correlations.

Fission and Fusion Fission New insights into the role played by

dynamics in the evolution of the com-posite system along the fission pathhave been achieved with the availabilityof large experimental data sets comingfrom the 4p charged particle and fissionfragments detector 8∏LP [18]. Thearray is equipped with trigger detectorsfor fission fragments and evaporationresidues with which the simultaneousmeasurement of the multiplicity of lightcharged particles (LCP) in the fissionand evaporation residue channels ispossible. The combined study of bothchannels in systems of intermediatefissility has revealed interesting aspectsof the fission dynamics, which haveproduced sensible feedback on the sta-tistical and dynamical description of thefission process. For instance, it has beenshown that the statistical model is notable to reproduce simultaneously the

LCP multiplicities in the evaporationresidues channel and the fission channelwith a unique set of parameters. Thisunexpected result has triggered a newstudy on the dynamical model of fis-sion. By using a 3D-Langevinapproach, it has been shown that abetter agreement can be obtained withthe experimental multiplicities in boththe evaporation and the fission channelif the nuclear viscosity is treated explic-itly with a reduced one-body dissipationmodel. Work is in progress to allow themodel to sample other observables,besides LCP multiplicities, like the pre-scission LCP angular distributions.

Multifragmentation Another research line that is pres-

ently ongoing at LNL, with relevantimplications concerning basic researchand applications, is the study of thephase transitions in nuclear matter.

The study of the low energy (liq-uid-gas) phase transition in nuclei canbe directly compared with phase tran-sitions in finite systems from otherfields. At LNL the low energy rangeof the caloric curve has been investi-gated, approaching the onset of themultifragmentation phenomenon. Anexperimental investigation of this pro-cess at low excitation energies isimportant to understand the basicproperties of the equation of state ofthe nuclear matter, complementing thedata collected around the Fermienergy. Moreover, one can obtainother physical information such as theenergy, the mass, and the isospindependence of the multifragmentationprocess, the temperature of the transi-tion, the limiting temperature, and ingeneral all information one can obtainon nuclear EOS for hot and excitedsystems formed in central nuclearreactions. Another subject that hasbeen systematically investigated is the

Figure 7. Comparison between calcu-lated and measured (solid circles) GDRwidths. The thin continuous line showsthe thermal shape fluctuation simulationwhereas the thick continuous lineincludes also the compound nucleuslifetime. The dashed line shows theaverage calculated <β> deformation.

laboratory portrait


dynamics involved in peripheral andsemi-peripheral reactions, where theformation of a neck region has beenfound in the intermediate energyregime. Again, one has investigatedthe low-energy side of these non-equilibrium processes measuring theemitted particles as a function of prop-erties of the interacting nuclei such asmass and charge asymmetry, isospin,and impact parameter. These measure-ments have been performed with theGARFIELD detector [1]. TheGARFIELD apparatus has also beenused together with the HECTOR g-rayBaF2 scintillators of the University ofMilano to study the properties of thegiant dipole resonance (GDR) at hightemperature and angular momentum.A coincidence measurement betweenthe high energy g-rays, the evapora-tion residues and the light chargedparticles was performed to study theproperties of the Ce nucleus. In Figure7 the measured increase of the GDRwidth with temperature for Ce nucleiis reported. Deformation effects andthe intrinsic lifetime of the compoundnucleus are the two combined mecha-nisms that explain such findings [19].

Reactions with Exotic Proton Rich Nuclei

The study of the properties of lightnuclei with exotic proton to neutronratio is the objective of the EXOTICexperiment at LNL. The study of thecross-section of reactions such as elas-tic scattering, Coulomb and nuclearbreak-up, sub-barrier fusion providesuseful information about the existenceof nucleon halo or skin and about theexcitation of exotic modes (exoticgiant resonances, low energy dipolestrength). Exotic nuclei are hereproduced by inverse kinematics fusionevaporation reactions of stable beamson a gas target. The recoiling nuclei,

after electromagnetic separation, areanalyzed and used for subsequentreactions. Presently two exotic beamsare operational: a 17F beam with inten-sity of 106 pps and a 8B beam withintensity of 104 pps [20]. As an exam-ple of such research activity the 17Fscattering on 208Pb has been studied atenergies around the Coulomb barrier.The 17F angular distribution was mea-sured and analyzed using opticalmodel calculations in order to get thebest fit potential parameters. Contraryto the results obtained using 19F, thestrong absorption radii of the imagi-nary potential are systematically about10% larger than those of the realpotential, an effect that might be dueto the very small 17F binding energy.The 17F cross-sections are similar tothose of the strongly bound nuclei16,17O, whereas the 19F reaction cross-section is a factor three larger. Suchoutcomes are interpreted as an indica-tion of a larger probability to excitecollective modes in 19F than tobreakup 17F. Aims of such investiga-tion are the study of proton radioactiv-ity of very neutron deficient nuclei,the determination of structure anddeformation of drip-line nuclei, animportant ingredient for modeling theelement nucleo-synthesis in the r-pchain in stars, and the exotic clusterradioactivity from trans-lead nuclei.

The Physics of Trapped Exotic Nuclei Trapping of radioactive nuclei is

presently considered a very promisingtool for precision measurements innuclear and atomic physics. Peculiarcharacteristics of nuclei stored in atrap are in fact their very small phasespace and the possibility to work in aclean environment with a negligiblesource thickness. Particularly relevantare studies on fundamental interac-tions, like parity non conservation

(PNC) in atoms and nuclear b decay,because one might get indications onphysics beyond the standard model ofelectroweak and strong interactions.PNC effects arise from mixing of elec-tronic states with opposite parity, giv-ing rise for instance to forbiddenelectric dipole transitions betweenstates of the same parity. Fr is consid-ered one of the best candidates as PNCeffects depends on Z3. Its is an alkalyatom, therefore ideally suited for bothlaser trapping techniques and preci-sion calculations. At LNL a set-up forfrancium production and trapping ispresently in operation. Francium ionsare produced at LNL via the197Au(18O,X) fusion evaporation reac-tions. The ions are then extracted andtransported through a secondary beamline to a laser area where they are firstneutralized and then released into amagneto-optical trap (MOT) [21].Recently, using an average primary18O beam current of 200 pnA, 210Frisotopes reached the MOT with anintensity of ~5 × 105 ions/s, and aMOT signal has been seen corre-sponding to about 10,000 trapped Fratoms. Work is in progress to furtherimprove the trapping efficiency and toperform atomic spectroscopy mea-surements on a level interesting forfuture PNC studies [21].

Application of Nuclear Methods

Element Analysis Using Light and Heavy Ions

Two electrostatic accelerators, theAN2000 and the CN, are dedicated tostudies based on application of nuclearmethods. Moreover a fraction close to15% of the Tandem-ALPI-PIAVEbeam time is dedicated to such interdis-ciplinary studies. The methods includePIXE (particle Induced X-ray Emis-sion), PIGE (Particle Induced g-ray

laboratory portrait


Emission), RBS (Rutherford Back-Scattering), NRBS (Non-RutherfordBack-Scattering), ERDA (ElasticRecoil Detection Analysis), allowinghigh precision analysis and character-ization of materials. The PIXE analysishas been used in different researchareas ranging from archeometricalresearches to air pollution measure-ments. PIXE methods has been usedfor trace element analysis to helparchaeologists in authenticating ancientgold artefacts (jewellery and coins)from the Carpathian gold mines.

Radiobiological Applications and Hadroterapy

Light and heavy ions in the energyrange available at the LNL are veryuseful to get insight into the basicmechanisms involved in the interac-tion of ionizing radiations with livingmatter also in view of tumor treatmentand radiation protection applications.Research on radio-biological effects(RBE) play in such a context a veryimportant role in determining thebasic protocol of application and instudying the cellular and molecularresponses to radiations. At LNL cul-tured/in-vitro mammalian cells areused as an experimental model and areirradiated in air using acceleratedcharged particles (light and heavy ions)provided by the LNL accelerators [22].Accelerator-based irradiation appara-tuses dedicated to radiobiology studieswith broad-beams, as a function of ionspecies, energy and dose, have beendeveloped and are routinely in use. Tostudy the cell response to low radia-tion doses (up to one ion per cell) anion beam of the dimension of fewmicrons has been developed. The cellresponse to radiation is evaluatedthrough different effects as cell killing(clonogenic cell inactivation), pro-grammed cell death (apoptosis), gene

mutation, chromosome aberrations,and expression of specific proteins. Inorder to tag such induced effects a lab-oratory dedicated to cell biology hasbeen created at LNL.

There is also an increasing interestfor tumor radiation therapy using neu-trons, protons, and light ions, becausesuch therapeutic beams have some fea-tures (well-defined distal and lateraldepth-dose profiles, high Relative Bio-logical Effectiveness) that are absent inphoton beams. Several tumors that donot respond positively to photon treat-ments are therefore expected to besuccessfully controlled by hadrons.Moreover, the better depth-dose profileof charged hadrons is expected to betterspare healthy tissue: a very importantfeature in treating tumours close to crit-ical organs and in paediatric tumors.However, the clinical RBE of hadronsis poorly known. The main reason ofthat is the lack of detectors able to mea-sure RBE in the clinical praxis. At LNLmini counters of a couple of millime-tres of size have been developed, whichare able to measure RBE in a real thera-peutic beam [23]. Studies are inprogress to develop mini detectors thatencapsulate two proportional counters,the main aim being the measurement ofthe RBE of the Boron Neutron CaptureTherapy radiation field.

Future Perspectives at LNL and the SPES Project

Improvements of the LNL acceler-ator complex are foreseen, both in ionenergies and intensities. A new ionsource, providing beams with highercharge states and currents, has beenrecently acquired and its installation isplanned in 2008. An increase of theavailable beam energy presently undertest can be obtained by beam strippingin proximity of the ALPI U bend:~30% energy increase is expected, at

the expense of a current drop of arounda factor 5. Further energy and intensityupgrade could be achieved by adding8 new cryostats, increasing the ALPIequivalent voltage by about 25%.

A new mid-term radioactive nuclearbeam facility (named SPES) dedicatedto the production of neutron rich beamsis now under study at LNL [24]. SPESis an INFN project to develop a Radio-active Beam facility as an intermediatestep toward EURISOL, LNL being thesite for the facility construction. Theproject is optimized for the productionof neutron-rich radioactive nuclei withmasses in the range of 80 – 160amuproduced by proton induced fission of a238U target. The designed fission rate isof 1013 fission/s induced by a 40MeVproton beam impinging onto a uraniumcarbide target. The most critical ele-ment of the SPES project is the uraniumcarbide target, which represents aninnovation in terms of capability to sus-tain the primary beam power. Thedesign is carefully oriented to optimizethe radiative cooling, taking advantageof the high operating temperature of2000°C. The radioactive isotopes willbe extracted and ionized at charge +1using a source directly connected to theproduction target. Different kinds ofsources will be used depending on thebeam of interest. A laser ion source forbeam purification is presently understudy in collaboration with INFN-Pavia. Selection and transport of theexotic beam at low energy and lowintensity is another challenging task.Techniques applied for the EXCYTradioactive beam facility (LNS) will beof reference for the beam diagnosticsand an on-line identification station willbe part of the diagnostic system. Acharge breeder will be needed beforeinjecting the exotic beams into thebunching RFQ and into the existingPIAVE superconducting RFQs, which

laboratory portrait


represent the first re-acceleration stagebefore injection into ALPI. The second-ary beams are expected to have rates ontarget of ~108–109 pps for 132Sn, 90Kr,94Kr and 107–108 pps for 134Sn, 95Krwith energies of 9–13MeV/amu. Suchfacility is also expected to deliver a5MeV proton beam to a 9Be target toproduce neutrons for medical applica-tions, such as the Boron Induced Cap-ture Therapy (BNCT), for astrophysicsand for material science.

Concerning new instrumentationrecent advances in crystal segmenta-tion technology and digital signal pro-cessing has opened the possibility tooperate Ge detectors in a position sen-sitive mode. This enables to build acompact array solely out of Ge detec-tors allowing g-ray tracking (theAGATA project). A g-ray trackingsystem involves measuring the posi-tion and the energy of every g rayinteracting in the detector so that thescattering path and the sequentialenergy loss can be deduced. The full4p AGATA array will consist of 18036-fold segmented individually encap-sulated Ge crystals, closely packedtogether in groups of three in a com-mon cryostat. As it is expected fromsimulations the AGATA detector canhave unprecedented features: an effi-ciency of up to 40% while maintaininga P/T-ratio of 60%. The commission-ing of the first sub-array of AGATA,called the Demonstrator, is foreseen atLNL in the year 2008. Such a device,composed of 5 triple cluster detectors,

will operate in conjunction with thePRISMA spectrometer. The firstphysics campaign of the Demonstratoris scheduled for 2009.

For more information and for sub-mitting proposals to use the LNLfacility, consult the LNL home page atwww.lnl.infn.it.

References 1. A. M. Stefanini et al., Nuclear Physics

News 5(2), 9–22 (1995). 2. A. M. Stefanini et al., Nucl. Phys. A

701 (2002) 217c; G. Montagnoli et al.,Nucl. Instrum. Methods Phys. Res. A547, 455 (2005); S. Beghini et al.,Nucl. Instrum. Methods Phys. Res.A551, 364 (2005).

3. A. Gadea et al., J. Phys. G 31, S1443(2005).

4. O. Moller et al., Phys Rev. C 74,024313 (2006).

5. Tz. Kokalova et al., Eur. Phys. J. A 23,19 (2005).

6. D. Tonev et al., Phys. Rev. Lett. 96,052501 (2006).

7. A. Gadea et al., Phys. Rev. Lett. 97,152501 (2006).

8. R. Du Rietz et al., Phys. Rev. Lett. 93,222501 (2004).

9. J. Ekman et al., Phys. Rev. Lett. 92,132502 (2004).

10. J. J. Valiente-Dobon et al., Phys. Rev.Lett. 95, 232501 (2005).

11. G. de Angelis, Prog. Part. Nucl. Phys.59, 409 (2007).

12. N. Marginean et al., Phys. Lett. B 633,696 (2006).

13. S. Lunardi et al., Phys. Rev. C 76,034303 (2007).

14. J. Valiente Dobon and D. Mengoni,priv. comm.

15. A. M. Stefanini et al., Phys. Rev. C 76014610 (2007).

16. L. Corradi, Nucl. Phys. A787, 160 (2007). 17. S. Szilner et al., Phys. Rev. C 76,

024604 (2007). 18. E. Vardaci et al., Nucl. Phys. A 734,

241 (2004). 19. O. Wieland et al., Phys. Rev. Lett. 97,

012501 (2006). 20. M. Mazzocco et al., Eur. Phys. J. A 28,

295 (2006). 21. G. Stancari et al., Eur. Phys. J. 150,

389 (2007). 22. A. Sgura et al., Radiation Protection

Dosimetry 122, 176 (2006). 23. L. De Nardo et al., Physica Medica

XX, 71 (2004). 24. SPES INFN-LNL-220 (2007). http://

www.lnl.infn.it/~spes/tech_design_2007/tech_design_index.htm

GIACOMO DE ANGELIS

INPN, Laboratori Nazionali deLegnaro, Legnaro, Italy

feature article


What Can Neutrinos Tell Us about the Earth?

NIKOLAI R. TOLICH Center for Experimental Nuclear Physics and Astrophysics, and Department of Physics, University of Washington, Seattle, Washington, USA

Introduction Thanks in part to a series of experiments measuring

neutrinos from the Sun, more is now known about the inte-rior workings of the Sun than the Earth. 238U, 232Th, and 40Kdecays within the Earth are believed to be responsible forthe majority of the current radiogenic heat production,which is the driving force for the Earth’s mantle convec-tion, the process that causes plate tectonics and earth-quakes. Currently, the only estimate of the total radiogenicheat produced by these elements comes from indirect esti-mates. If we are to understand the dynamics of the Earth, itis vital to obtain an accurate measurement of this radio-genic heat production. As well as producing heat, b-decaysin the decay chains of 238U, 232Th, and 40K also produceelectron anti-neutrinos, ves, or so called geoneutrinos. If wecan measure the geoneutrino flux near the surface of theEarth, we could finally measure the radiogenic heat produc-tion and constrain models for the Earth’s dynamics.

Our current understanding of the Earth is introduced inthe second section, which leads to estimates of the geo-neutrino flux, discussed in the third section. Geoneutrinodetection techniques are introduced in the fourth section. TheKamLAND collaboration recently investigated geoneutrinos[1,2]; however, the sensitivity achieved, was limited by alarge background of ves from surrounding nuclear powerreactors. These results are discussed in the fifth section.Finally, future experiments are discussed in the final section.

The Earth

Structure and Composition Earth models based on seismic data divide the Earth into

three basic concentric regions from the inside outward: thecore, mantle, and crust [3]. The core is composed mostly ofFe and is further subdivided into a liquid outer core and asolid inner core. The mantle is composed mostly of silica andis further subdivided into a lower mantle, transition zone, andupper mantle. Two very different types of crust, continentaland oceanic, cover ~40% and ~60% of the Earth’s surface,respectively. Plate tectonics, or the movement of the

continental crust, is caused by convection of the mantle withthe oceanic crust renewing at mid-ocean ridges and returningto the mantle at subduction zones. This makes the oceaniccrust remarkably homogenous and relatively young, on aver-age only ~80 Myr old. By contrast, the continental crust isvariable and much older, on average ~2,000Myr old [3].

To determine the chemical composition of the Earth, wecan compare physical properties determined from seismicdata to laboratory measurements. However, this does notprovide us with much information on chemical elementswith relatively low concentrations, such as U, Th, and K.Lava flows bring xenoliths, foreign crystals in igneousrock, from the upper mantle to the surface, allowing an esti-mate of their chemical compositions. By digging holes wehave directly probed the chemical composition down toapproximately 10 km depth, a relatively small fraction ofthe Earth’s radius, ~6300 km. Unfortunately, the regionprobed directly is believed to be enriched in U, Th, and Kcompared with the mantle.

The total chemical composition of the “Bulk SilicateEarth” (BSE), the component of the ancient Earth includingthe current mantle and crust before they separated, is esti-mated based on the belief that the Earth formed from thesame cloud of rotating gas and dust as the Sun. The chemi-cal abundance of the solar photosphere is compared to thecompositions of primitive undifferentiated meteorites. TheU, Th, and K concentrations in these meteorites are thenconverted into BSE concentrations based on the volatilitiesof the different elements, and the fractions that are believedto have entered the Earth’s core. Table 1 gives the expectedU, Th, and K concentrations for various recent BSE models.

It is commonly believed that there is no U in theEarth’s core. However, there is an alternative hypothesissuggesting that some U entered the core forming a naturalnuclear reactor at the center of the Earth [7]. This couldproduce up to 6 TW of heat, powering the Earth’sdynamo, and could explain anomalous 3He/4He ratios inlava gas. There is another hypothesis suggesting that Ucould have formed a natural nuclear reactor at the Earth’scoremantle boundary [8].

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Heat Generation and Dissipation Based on the total mass of the BSE, the concentrations

given in Table 1, and the heat production from 238U, 232Th,and 40K decays, the ranges of the total power generated fromthese decays are estimated to be 5.6–9.9 TW, 5.5–10.2 TW,and 2.1–4.2 TW, respectively. This is believed to be to themost significant heat generating source in the Earth with atotal less than 24.3 TW, which can be compared to the esti-mated 44 ± 1 TW total heat dissipation rate.

The total heat dissipation rate is estimated based on the tem-perature as a function of depth measured at 20,201 sites aroundthe globe [9]. As shown in Figure 1, the majority of this heat isdissipated through the oceans, despite the fact that the continen-tal crust contains the majority of the radiogenic heat producingelements. Based on a different model for heat dissipation fromthe oceanic crust, where there are not many measurements, andwhere the temperature profile with depth could be affect bywater circulation within the oceanic crust, an alternative totalheat dissipation of 31±1 TW has recently been estimated [10].

Models of mantle convection [11–13] suggest that the radio-genic heat generated within the mantle should be a larger frac-tion of the heat dissipated from the mantle than those obtainedwith even the lowest heat dissipation estimate of 33 TW andhighest radiogenic heat generation estimate of 24 TW. A direct;measurement of the terrestrial radiogenic heat production ratewould help our understanding of this apparent inconsistency. Toconstruct mantle convection models it is most important toknow the U and Th contents in the mantle. However, it wouldalso be useful to measure the U and Th contents in the continen-tal crust using geoneutrinos because there are still uncertaintiesin the properties below the first few kilometers [14].

Geoneutrino Signal The expected geoneutrino energy spectra, shown in Figure

2, are determined based on the decay chains of 238U, 232Th, and40K. Because the U geoneutrino signal extends to higher energythan that of Th geoneutrinos, the measured energy distributioncan be used to distinguish geoneutrinos from U and Th decays.

For geoneutrinos from U and Th decays the flux as afunction of energy is given by [15]:

where A is decay rate per unit mass of the parent isotope,

(En) is the expected ve energy spectrum, L is the position

relative to the detector, a(L) is the parent isotope mass perunit rock mass, r(L) is the rock density, and the integral isover the volume of the Earth. �(En) is an energy dependent

correction due to neutrino oscillations. Due to the distributedsource of neutrinos within the Earth, the oscillation signatureis washed out with �(En) approximated within 2% by

�(En) ≈ 1 − 0.5 sin2 2q12, (2)

where degrees [16]. Based on a detailed simulation, including seismic mod-

els of crustal thickness and type, Table 2 gives the calcu-lated geoneutrino detection rates at various possible detectorlocations [17]. Figure 3 shows that for detectors in the conti-nental crust, the majority of the geoneutrinos come from thecontinental crust with ~20% coming from the mantle.

Excluding neutrino oscillation, a natural reactor at theEarth’s core or the core-mantle boundary would produce avery similar energy spectrum of detected ves to that fromcommercial nuclear power reactors, which is peaked at~4 MeV and extends up to ~9 MeV.

Table 1. Concentrations of U, Th, and K in various BSE models.

Ref. [4] Ref. [5] Ref. [6]

U [ppb] 20.3 ± 4.1 21.8 ± 3.3 17.3 ± 3.0

Th [ppb] 79.5 ± 11.9 83.4 ± 12.5 62.6 ± 10.7

K [ppm] 240 ± 48 260 ± 39 190 ± 40

d

dE

dn

dE

Φ

n n

n)=A n) n)r

p( ( (

( ) ( ),E E E d

a� L

⊕∫L L

L42

(1)

dn

dEn

q12 1.3+1.4 = 33.8−

0 40 60 85 120 180 240 350

mWm -2

Figure 1. Map of conductive heat dissipation rate [9].Black lines represent land masses, white lines representcontinental plate margins.

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Experimental Techniques The most common reaction used to detect ves is neutron

inverse b decay reaction

ve + p ⇒ e+ + n, (3)

where the positron, e+, almost immediately deposits its kineticenergy, then annihilates with an electron producing two g-rays;this is referred to as the “prompt event.” The neutron, n, firstthermalizes, and then is captured by another nucleus in thedetector releasing a fixed amount of energy; this is referred toas the “delayed event.” The fixed total g-ray energy of the n-capture, and the spatial and temporal correlation between theprompt and delayed events result in a signature clearly distin-guishable from most backgrounds. Another advantage of thisreaction is that kinetic energy of the e+ is approximately equalto the ve energy minus 1.8MeV. However, this also means thatthe minimum ve energy for the neutron inverse b decay reactionto occur is 1.8MeV, making the reaction insensitive to ves from40K decays, which occur below 1.3MeV, as shown in Figure 2.

To estimate the number of geoneutrinos from the mantlein the presence of a significant number of geoneutrinos fromthe continents, it is necessary to determine the direction ofthe incoming geoneutrino. Given enough geoneutrinos, neu-tron inverse beta decay allows a statistical determination ofthe geoneutrino source distribution because the neutron pre-serves some forward momentum from the incoming ve. Someof the difficulties in performing this measurement include:accurate detector vertex resolution, the random walk the neu-tron undergoes before being captured, and determining theneutron creation point from the reconstructed positron

position. Using a liquid scintillator containing a small amountof Gd, which has a very high neutron capture cross-sectionreducing the neutron random walk, the CHOOZ experimentshowed a statistical excess of neutrons captured in the direc-tion pointing away from the nuclear reactor that was theirsource of detected ves [18]. Studies show that loading liquidscintillator with Li at 1.5wt% improves the ability to recon-struct the geoneutrino source distribution [19]. A simulationfor such a detector with a fiducial mass of 50kton operatingfor 5 years shows modest ability to distinguish geoneutrinoscoming from the Earth’s mantle and continental crust.

Recent Results The first experimental hint for the existence of geoneutri-

nos, at the 95% confidence level, came in 2005 when theKamLAND experiment, located in Kamioka, Japan, pub-lished the low energy ve energy spectrum shown in Figure 4.Based on more statistics and improved analysis the Kam-LAND experiment report a total geoneutrino flux of4.4±1.6×106 cm−2s−1 [2], which agrees with the central valuepredicted by Earth models, but it is not yet precise enough toseriously constrain those models. Based on the location ofKamLAND, surrounded by nuclear power plants at a meandistance of approximately 200km, the ultimate geoneutrinosensitivity is limited due to ve backgrounds from the nuclearpower plants. However, there is some sensitivity to be gainedafter the scintillator purification currently underway, whichshould reduce the 13C(a,n)16O background reactions [20].

Planned Experiments The Borexino experiment, located in LNGS, is similar to

KamLAND except it has about one third the fiducial mass and

Table 2. Expected number and maximum range of geoneutrinos per 1032 target protons per year at various possible detector locations assuming sin2 2q12 = 0.855.

Location Expectation Maximum range

Baksan 52 ± 8 29–75

Hawaii 13 ± 4 6–28

Himalaya 64 ± 9 36–88

Homestake 52 ± 8 29–74

Kamioka 35 ± 6 19–55

LNGS 41 ± 7 22–61

Sudbury 50 ± 8 27–72

Neutrino energy [keV]0 500 1000 1500 2000 2500 3000 3500 4000 4500

Inte

nsity

[1/

keV

/dec

ay]

10–8

10–6

10–4

10–2

Figure 2. The xe energy spectra for the 238U(solid),232Th(dash), and 40K(dot-dash) decay chains. The verticalline represents the xe detection threshold for neutroninverse β decay, Eq. (3).

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half the background of ve from nuclear reactors [21]. It is cur-rently collecting data, and can expect to observe approximately6 geoneutrinos per year, with a predicted total geoneutrino fluxmeasurement accuracy of better than 30% after five years.

The next detector online will likely be SNO+, which willhave a fiducial mass similar to that of KamLAND and belocated in Sudbury, Canada [22]. The expected ve backgroundfrom surrounding nuclear reactors will be approximately onequarter of that at KamLAND, and this detector is located insome of the oldest continental crust unlike KamLAND, whichis located near the oceanic and continental crust boundary.This should allow for a reasonably sensitive measurement at alocation with a completely different mix of geoneutrinos fromcontinental crust and mantle compared with KamLAND.

A detector similar to KamLAND but located at Homestakewould have approximately 7% of the ve background from sur-rounding nuclear reactors. Such a detector could make an accu-rate measurement of the geoneutrino fluxes from 238U and 232Thdecays, but would also test the hypothesis of a nuclear reactor atthe center of the Earth with a sensitive better than 1 TW [23].

101103

104

105

106

[cm–2S–1]

φU

102

5

4

3

2

1

103

1 Himalaya (crust)

2 Kamioka (crust)

3 LNKGS (crust)

4 Hawali (crust)

5 Mantle (crust)

R [Km]104

Figure 3. Cumulative geoneutrino flux as a function ofdistance to the source. Lines 1 through 4 are for variousdetector locations, and line 5 is the contribution from themantle [17].

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There are also plans for two different multipurpose detec-tors with a fiducial mass more than ten times as large as thatof KamLAND: Hanhano [24], and LENA [25]. LENAwould be located in continental crust in Europe. Hanohanowould be a relocatable detector positioned at approximately4000m-depth at the bottom of the ocean. Because oceaniccrust is thinner than continental crust, and has lower U andTh content, the majority of the observed geoneutrinos wouldcome from the mantle. It would also have a very small ve

background from surrounding nuclear reactors. Finally, there are plans to build a detector capable of

detecting the geoneutrino source [26]. This is a very ambi-tious project in its very early stages. As much as geophys-icsts may like a measurement of the 40K content of theEarth, there are currently no viable plans.

Conclusions A measurement of geoneutrinos is an important step in

constraining our understanding of the Earth’s U and Th dis-tributions. The heat from the decays of these isotopes is thedriving force for plate tectonics and earthquakes, and this is

the only technique that allows us to directly observe thesedecays occurring at the inner depths of the Earth. The Kam-LAND experiment [1,2] has recently shown the viability ofsuch a measurement; however, it was limited by ve back-grounds from nearby nuclear power plants. Future experi-ments located away from commercial nuclear reactors willmake measurements sensitive enough to determine if thecurrent BSE models are correct, shed light on the structureof the lower continental crust, and experimentally test thehypothesized natural reactor at the center of the Earth.

Acknowledgement I am particularly grateful to Sanshiro Enomoto and

Kazumi Tolich for their useful comments on this article.

References 1. T. Araki et al., Nature 436, 499 (2005). 2. S. Abe et al., Phys. Rev. Lett. 100, 221803 (2008). 3. G. Schubert, D. L. Turcotte, and P. Olson, Mantle Convection

in the Earth and Planets (Cambridge University Press, Cam-bridge, 2001).

4. W. F. McDonough and S. S. Sun, Chem. Geol. 120, 223 (1995). 5. H. Palme and H. O’Neill, Cosmochemical estimates of mantle

composition, in Treatise on Geochemistry (Pergamon, 2003). 6. T. Lyubetskaya and J. Korenaga., J. Geophys. Res. 112,

B03211 (2007). 7. J. M. Herndon, Proc. Nat. Acad. Sci. 100, 3047 (2003). 8. R. J. de Meijer and W. van Westrenen, arXiv:0805.0664. 9. H. N. Pollack, S. J. Hurter, and J. R. Johnson, Rev. Geophys.

31, 267 (1993). 10. A. Hofmeister and R. Criss, Tectonophysics 395, 159 (2005). 11. F. M. Richter, Earth Planet. Sci. Lett. 68, 471 (1984). 12. M. J. Jackson and H. N. Pollack, J. Geophys. Res. 89, 10103

(1984). 13. T. Spohn and G. Schubert, J. Geophys. Res. 87, 4682 (1982). 14. S. Taylor and S. McLennan, Reviews of Geophys. 33, 241 (1995). 15. N. R. Tolich, Experimental study of terrestrial electron anti-

neutrinos with KamLAND, Ph.D. thesis, Stanford, 2005,UMI-31-62346.

16. B. Aharmim et al., arXiv:0806.0989. 17. F. Mantovani, L. Carmignani, G. Fiorentini, and M. Lissia,

Phys. Rev. D 69, 013001 (2004). 18. M. Apollonio et al., Phys. Rev. D61, 012001 (2000). 19. I. Shimizu, Nucl. Phys. Proc. Suppl. 168, 147 (2007). 20. S. Enomoto, Earth, Moon, and Planets 99, 131 (2006). 21. M. Giammarchi and L. Miramonti, Earth, Moon, and Planets

99, 207 (2006). 22. M. Chen, Earth, Moon, and Planets 99, 221 (2006). 23. N. Tolich et al., Earth, Moon, and Planets 99, 229 (2006). 24. S. Dye et al., Earth, Moon, and Planets 99, 241 (2006). 25. K. Hochmuth et al., Earth, Moon, and Planets 99, 253 (2006). 26. R. de Meijer et al., Earth, Moon, and Planets 99, 193 (2006).

Anti-neutrino energy, Eν (MeV)

Eve

nts

/ 0.1

7MeV

1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.40

5

10

15

20

25

30

Anti-neutrino energy, Eν (MeV)

Eve

nts

/ 0.1

7MeV

2 4 6 80

5

10

15

20

a b

Figure 4. xe energy spectra in KamLAND [1]. Main panel,experimental points together with the total expectation (thindotted black line). Also shown are the total expected spectrumexcluding the geoneutrino signal (thick solid black line), theexpected signals from 238U (red line), and 232Th (green line)geoneutrinos based on Earth models, and the backgroundsdue to reactor xe (light blue line), 13C(α,n) 16O reactions(brown line), and random coincidences (dashed purple line).Inset, expected spectra extended to higher energy.

facilities and methods


EURISOL High Power Targets

Introduction Modern Nuclear Physics requires

access to higher yields of rare iso-topes, that relies on further develop-ment of the In-flight and IsotopeSeparation On-Line (ISOL) produc-tion methods. The limits of the In-Flight method will be applied via thenext generation facilities FAIR in Ger-many, RIKEN in Japan, and RIBF inthe United States. The ISOL methodwill be explored at facilities includingISAC-TRIUMF in Canada, SPIRAL-2in France, SPES in Italy, ISOLDE atCERN, and eventually at the veryambitious multi-MW EURISOL facil-ity [1]. ISOL and in-flight facilitiesare complementary entities. While in-flight facilities excel in the productionof very short lived radioisotopes inde-pendently of their chemical nature,ISOL facilities provide high Radioiso-tope Ion Beam (RIB) intensities andexcellent beam quality for 70 ele-ments. Both production schemes areopening vast and rich fields of nuclearphysics research.

In this article we will introduce thetargets planned for the EURISOL facil-ity and highlight some of the technicaland safety challenges that are beingaddressed. The EURISOL RadioactiveIon Beam production relies on three100kW target stations and a 4MW con-verter target station, and aims at pro-ducing orders of magnitude higherintensities of approximately one thou-sand different radioisotopes currentlyavailable, and to give access to new rareisotopes. As an illustrative example ofits potential, beam intensities of theorder of 1013 132Sn ions per second willbe available from EURISOL, providingideal primary beams for further frag-mentation or fusion reactions studies.

Direct High Power ISOL Targets Classical ISOL targets are operat-

ing for more than four decades. Inorder to open the fission, spallation,and fragmentation reaction channels,the target material is directly exposedto energetic charged particle beams ofprotons or light ions. This method hasproven to be very successful; around1,000 radioisotope beams of 70 differ-ent chemical elements have been pro-duced with driver beams energiesranging from 40 MeV/A to 1.4 GeV/Aat ISOLDE-CERN-Geneva, RIBF-Oak Ridge, TRIUMF-Vancouver, andISIS-Gatchina. The crucial need forchemical purity and the presence ofisobars with orders of magnitude moreintensity, due to their relative proxim-ity to stability, lead to the develop-ment of various types of chemicallyselective ion-sources, molecular sidebands, and active transfer lines.

Today, 100 target-transfer-line-ion-source systems are operated rou-tinely at with both pulsed (1–4 kW)and quasi DC (up to 10–35 kW)driver beams. The main challenge setby the 100 kW EURISOL beampower, is that the evacuation of theenergy deposited by the 1 GeV pro-tons through ionization in the targetmaterial, while the target materials(some of which are low density andopen structure materials or are in theform of oxides with thermal insulat-ing properties) are kept at the highestpossible temperature to minimize thediffusion time of the radioisotopes.The target oven is designed to opti-mize the pumping speed. TheEURISOL ion-source and transferlines are designed to efficiently ion-ize larger amounts of radioisotopes inthe presence of an increased flow of

impurities released by larger amountsof target materials.

The life time of the target, transfer-line, and ion-source system is a keyissue that directly impacts on theavailability of the facility via the ratioof the time required to change the tar-get-ion-source unit and to tune thebeam, versus the radioactive beamoperation time (typically a total of10 days). Today’s target-ion-sourceunit’s life time is 1.5 1019 protons whenoperated in pulsed mode at 1.4 GeV,and reaches 3.2 1020 protons underquasi cw operations with 0.5 GeV pro-tons (EURISOL: 5.4 1019 1 GeV pro-tons per 100 kW beam day). This, andthe need to deliver different ion-beamsto several users in parallel, motivatedthe choice of three independent100 kW direct target stations.

High temperature sintering, graingrowth, and radiation damagesinduced by the driver beam on the tar-get material, its container and ionsource components, are the likely fac-tors limiting the life time of the targetand ion-source system. The effectswill be increased decay losses as wellas the reduction of yields and ion-source efficiency. Four target and ion-source systems were selected in theEURISOL design study in order tobenchmark the necessary R&D fieldsand to validate the necessary engineer-ing and numerical simulations tools.

Heat transfer. With depositedpowers of the order of 10 to 60 kW,efficient and novel heat dissipationschemes must be developed. For oxidetargets—otherwise known as thermalinsulators—this is addressed by thedevelopment of new composite mate-rials such as a niobium-foil–aluminumoxide compound. For molten metal



target units, circulation loops and heatexchangers will handle the heat load,where the release properties rely onthe appropriate design of an isotopediffusion chamber with minimal dropsize or liquid layer thickness.

Multi-body target. Efficient heatdissipation is achieved at TRIUMF fora primary beam power of 20 to 50 kW.Several compact sub-units of the sametype, each accommodating ~25 kW,will successfully address the heatdeposited by a 100 kW driver beam(Figure 1). The release properties areinfluenced by the merging of the neu-tral atomic streams from the sub unitsinto a single ion source, through shorttransfer lines. The target life time isslightly affected by the pulsed protonbeam time structure inherent to thedistribution of the p-beam to each subunit. To benchmark the release, a dualcontainer target equipped with twotransfer lines and remotely actuatedtight valves has been tested with anoble gas ion source at ISOLDE. The

measured release reproduces theexpected effusion delay originatingfrom a fraction of the isotopes revisit-ing the second transfer line and target.As it is known for many elements, thediffusion process is dominating therelease. The first results on Ar and Neradioisotopes are promising.

Radiation induced materialdamage. The Target Prototypes Irra-diation Programme for EURISOL(TARPIPE) is ongoing at Injector 1 at

the Paul Scherrer Institute. Samples ofmetals, carbides and oxides were irra-diated in order to reach several dis-placements per atom (dpas), whichcorresponds to 3 weeks of target oper-ation at nominal EURISOL parame-ters. Visual and microscopicobservation of the material before andafter irradiation will allow assessingsintering and irradiation effects atnominal operation temperatures.

Diffusion. New submicrometricand nanometric target materials areunder development, where their stabil-ity at high temperature and underintense irradiation is a critical feature.A first milestone has been achievedwith the successful development ofsubmicrometric SiC targets (Figure 2),which has produced the highest andmost stable yields of exotic Na andMg isotopes at CERN-ISOLDE.

Ion-sources and effusion. The ionsources tested with one order of magni-tude increase of the stable ion current,kept their efficiencies. For the morecomplex target-ion-source systems thathave been proposed, the effusion timewill increase. Very short lived elementswill still require dedicated systems.

Direct target yields. The produc-tion cross-sections of the 100 kW tar-get stations are the same as thosefound at ISOLDE (1 GeV). The

Figure 1. The EURISOL 100 kW multi-body direct target concept, four targetsare connected to a single ion-source. The proton beam is sequentiallydistributed on each target.

Figure 2. Micrograph of a sub-micrometric SiC target before (left) and after(right) in-beam operation at CERN-ISOLDE.



yields of neutron rich radioisotoperesulting from fission reactions arenot very sensitive to the protonenergy between 0.5 and 1.4 GeV;however, evaporation is larger withincreasing proton beam energy andenhances the production in the n-deficient and deep spallationdomains. Light fragments arestrongly enhanced with increasingproton energy (i.e., yield increases ofseveral orders of magnitude weremeasured for light sodium isotopesbetween 600 MeV and 1.4 GeV atISOLDE). Within the EURISOLframework, the direct target RIBintensities are expected to be propor-tional to the driver beam power.

Neutron Converter ISOL Targets The neutron converter ISOL con-

cept was first proposed by Jerry Nolenand co-workers. In an ISOL convertersystem, the neutrons are generated byhigh energy protons impacting on ahigh Z material (so-called spallationn-source). The radioisotopes are thefission products of fissile target mate-rial positioned close to the neutronsource. The “low” temperature con-verter is also designed to convey theheat resulting from the primary parti-cle’s ionization losses to dedicatedheat exchangers. In order to cope with

the 2.3 MW power deposited in thespallation target, out of the 4 MWEURISOL proton beam, it has to bemade of liquid metal. Two optionsbased on axial or radial molten metalflow directions were investigated. It isinteresting to note that, for a given Hgtemperature increase (typically 120–180 K), a radial flow allows one orderof magnitude higher power density.

Converter with Liquid Metal in Contact with a Window

In the Coaxial Guided Stream(CGS) design, the mercury is keptunder pressure and flows within adouble walled tube with a proton beamwindow at one end (Figure 3). The mer-cury flows toward the proton beam inthe outer part of the tube and along thep-beam in the inner part making a u-turn at the window. By choosing mer-cury, which is an excellent spallationtarget and is liquid at room tempera-ture, this liquid metal can transportaway a huge amount of heat, and atthe same time cool the target walls andthe window. The radioactivity inducedin the mercury can to some extent beremoved, with some of the extractedisotopes having a commercial value.

The energy deposition peaks atapproximately 2 cm after the interac-tion point, reaching 1.9 kW/cm3/MW

of beam, and decreases rapidly there-after. The beam window must with-stand 900 W/cm3/MW of beam. Thewindow parameters were optimizedusing an interative process in whichthe temperature and thermal stress inthe window were calculated to bebelow irradiated materials stress lim-its. Once the beam window was opti-mised, the liquid mercury flow insidethe target container was tuned to mini-mise pressure losses while ensuringadequate cooling of the window andpreventing vaporization and cavitationin the back-swept surfaces. Eventually,annular blades were inserted along thebeam window to accelerate the flow,increase the local cooling and reducethe pressure drop at the 180-degreesturn. With this design, and a bulk pres-sure of 7.5 bar, the maximum tempera-ture in the beam window is 200°C andthe maximum von-Misses stress is135MPa. The mercury peak tempera-ture is 180 °C and its maximum veloc-ity is 6 m/s at the 180-degrees turn, inthe channels formed by the flow-guidesand the walls.

A Windowless Liquid Metal Converter The so-called Windowless Trans-

verse Mercury Film (WTMF) target(Figure 4) avoids the technical diffi-culties related to pressurized beamwindows and is advantageous in termsof neutronics. Mercury flowingthrough the upper tube is guided into avertical jet by sets of fins. Below theinteraction point, the mercury isrecovered and pumped to the heatexchanger circuit, where the volatileseparator and the mercury reservoirare placed.

The brief exposure of the liquidmetal to the proton beam permitscontrol of the temperature increase bysetting the local velocities via tuningof the fin pitches to match the beam

Figure 3. Coaxially Guided Stream Hg-spallation neutron source designed forthe 4 Mw target station of the EURISOL facility, the expected Hg-flow velocitiesare indicated on the detailed view of the 180° turn.



cooling requirements. The WTMFtarget was evaluated for a mercuryflow-rate of about 12 l/s; a tempera-ture increase of the mercury of about117.5 K; a heat deposition density onthe beam centre line of 25 kW/cm3;and a total heat deposition of 2.3 MW.The film is split in two regions, a cen-tral one (1 cm thickness), receiving theimpact of the beam and flowing at highspeed, and an external one confiningthe former (1.5cm on each side) toreduce high-energy secondary particlesescape and maximize the productionof spallation neutrons.

Three different prototypes weretested on an Indium-Gallium-Tin loopat the Institute of Physics and the Uni-versity of Latvia (IPUL, Riga). Thefilm behavior and flow stability seem apriori compatible with the EURISOLdesign requirements, although furthertests, involving larger mass flows,have to be performed. In order to testthe feasibility of the WTMF design, ascale model is being developed andwill be tested with mercury.

The beam-target interaction as afree surface facilitates operation overextended periods; a reduction of thetarget exchange frequency (due tobeam window radiation damage) isanticipated. Moreover, the reduced

thickness of the film produces a harderneutron spectrum and permits thepositioning of actinide fission targetscloser to the interaction point. Thisincreases the fission density rates andreduces the higher actinide produc-tion, by favoring fission rather thancapture reactions.

Fission Target EURISOL-DS targets are derived

from the concept proposed by thePIAFE (Projet d’Ionisation et d’Accel-eration de Faisceaux Exotiques) and

MAFF (Munich Accelerator for FissionFragments) projects. Conceptually, atarget filled with 235U or other actinide isinserted, through a channel created in theshielding, close to the neutron source atthe position of maximum neutron flux.Each target module can be inserted,replaced and serviced by means ofremote handling. The shielding aroundthe n-spallation source is a combinationof iron and concrete with a total thick-ness of about 6 meters. The neutron fluxis thermalized in order to optimize 235Ufission while for other fissionable targetmaterials, like 238U or 232Th, a hard neu-tron spectrum is required. Up to six ver-tical channels are foreseen eachcontaining MAFF-like production sys-tems. Loading and unloading all beamelements, including the fission targets, isaccomplished within a mobile transporttube. The assembly is then moved into ahot cell where remote handling of thecomponents will be performed undervisual control.

In operation position, all compo-nents are inside a double walled vac-uum tube embedded in the concreteshielding. A cooling water system is

Figure 4. Windowless Metal Transverse Flow (WMTF) spallation neutronsource. Three pitch flow-guide racks were designed to match the Hg-flow to thedriver beam deposited power density illustrated by the lego plot.

Figure 5. Fission target assembly (left); Details of the finned target, maximizingheat dissipation, and its thermal equilibrium calculation are shown (right).



required to evacuate the fission heat of30 kW that correspond to 1015 fissionsper second. In view of the radiationlevels, vacuum pumps have to beplaced after the shielding. In order toevacuate the gases continuously ema-nating from the fission target duringoperation, cryo-panels are distributedinside the vacuum tube. The systemnot only improves the vacuum but alsotraps and confines the radioactivityfrom gaseous elements.

The MAFF fissile material ishighly enriched uranium dispersed inthe graphite matrix with a 235U-densityof 2g/cm3. To host 235U, two graphitetypes were selected in view of theirthermal properties: MKLN (specialgraphite) and POCO (graphite foam).High density uranium-carbide (UC)pellets containing 238U, enriched withabout 2% of 235U, has a total U-densityof 12 g/cm3. An intensive R&D pro-gram to characterize the RIB-yields ofhigh density uranium-carbide has beencarried out in collaboration with sev-eral European Institutions.

The target assembly is shown inFigure 5. The actinide carbide disks arehoused in a graphite primary container,200 mm long and 35 mm diameter, sur-rounded by a tantalum container actingas confinement and as heat radiator.This container has a finned structurethat increases its effective emissivityand allows the active target volume toremain at the required high temperatureof around 2000°C, while the tempera-ture drop is mainly localized across thefins. A central hole of 8mm diameterlinks to single ionization ion sources(laser, plasma, ECR) that are underinvestigation. The fission target hasbeen designed to operate at 100kV.

Fission target yields. The flexibleapproach resulting from the multi-fissiletargets inspired from the MAFF-PIAFEprojects, allows neutron spectra from

thermal to hard and the choice of suit-able actinides. The isotope productioncharts are under investigation; the vari-ous options yield up to orders of magni-tude differences in specific cross-sections (illustrated by the difference ofthermal neutrons induced 235U fissionvs. hard neutron driven 238U fission).The individual target units are to bedesigned to handle 1015 fission/s for a235U targets in a thermal neutrons flux.Reduction of the fission rate by oneorder of magnitude is expected for otheractinide targets used with hard neutrons.

The release time is driven by diffu-sion and effusion. Therefore, the decaylosses will be given by the chosenactinide, its isotopic distribution, stochi-ometry, mass, and geometry. As a firstapproximation, in view of the similaractinide masses and target volumeinvolved, the typical release parameters(and decay losses) should be close tothose of standard ISOLDE UCx targets.

The ion-sources will be dealingwith 3 orders of magnitude higherradioactive beams and higher stableelements streams than today’s systems.Further work is required to assess theMulti-MW fission target ionizationefficiencies. The ion beams of this tar-get and ion-source multi-systems needsto be merged, a proposition based on anopen ECR structure is under investiga-tion, while seemingly promising, itsefficiency is not yet determined.

Safety for High Power ISOL Targets

The envisaged EURISOL facilitywill produce RIBs at intensities 2–3orders of magnitude higher than exist-ing facilities. A corresponding increaseof the radioactive inventory is expectedthat requires a dedicated safety filecontaining procedures, hazard evalua-tion, risk analysis, operational safetythat should be in the foreground from

the very first design, to the dismantlingof the facility including disposal of theradioactive waste. The selection of theproduction methods, the choice ofmaterials and the design of the facilitymust be integrated from the start. Thesafety aspects of the future RIB pro-duction targets and transport system,among them, the fissile targets aimingat a few 1015 fissions/s, will bear thehighest activity and shall integrate thebest safety standards. The new RIBproduction techniques will be keyinputs to the safety approval proce-dures and will have a major impact onthe final cost of the entire facility.

Spallation neutron source.EURISOL relies on a high-energy high-intensity proton accelerator coupled tothe high power liquid Hg target. Thisresults in a comparable nuclear installa-tion to the new generation spallationneutrons sources SNS (Oak-Ridge,USA) and J-SNS (J-PARC, Japan).

Fission products. The fissile mate-rial RIB production targets will useeither uranium or thorium, leading toan in-target thermal fission power com-parable to low power research reactors.

Confinement. Radioactive nucleibeams of unprecedented intensities upto 1013 ions/s will be extracted, ionized,and post-accelerated up to the energiesof 150 MeV/u and distributed overlarge areas to the experiments. In viewof these mobile and quickly transportedsources, ensuring the radioprotection ofthe staff in the experimental hall will bea major challenge. Furthermore, non-ionized gaseous/volatile radioactivity isfreely traveling in the beam pipes andvacuum system and must be monitored,controlled, and managed.

Dose rates. Much of the safetywork has focused on the Multi-MW tar-get station—the most challenging issuein this context. The characterization ofprompt radiation from primary beam



components, target-converter, RIB pro-duction targets, beam dump, and sec-ondary beam lines is being assessed.The activation of the entire environ-ment including buildings, air, soil, andground water have been estimated. Theprompt and residual dose levels are cru-cial inputs to the dimensioning of thebuildings and appropriate shieldingstructures, for defining the maintenanceprocedures and accessibility levels, andfor preparing dismantling and decom-missioning strategy. As an example, theresidual specific activity of the concreteshielding is shown in Figure 6.

Radioactive waste disposal. Thehandling and disposal of the radioac-tive production targets (e.g., UCx,ThCx), the liquid Hg converter targetand its auxiliary systems is not yetstudied. Our estimates show that theinduced radioactivity of the Multi-MW target station reaches approxi-mately 109 GBq. This implies that theradioactivity handling and the preven-tion of release accidents should becomparable to the nuclear powerindustry. At the end of EURISOL

operations, the irradiated liquid mer-cury (~20 tons) has to be treated ashighly radioactive waste. The onlyappropriate final disposal form for thisradiotoxic and toxic type of waste issolidification. Therefore, we launchedboth theoretical and experimental ded-icated studies on solidification of mer-cury, aimed at the selection of anadequate sythesis and of a matrixsuited for its final disposal.

Radioactive gases. 1015 fissions/salso yield sizable amounts of volatileradioactive species that have to be con-fined. For this purpose, the concept of acryo-trap system placed between theproduction target and the experimentalarea has been proposed, designed andtested to freeze gaseous radioactivity asclose to its origin as possible. The stud-ies converged on the design of a com-pact cryo-trap operated with coldhelium gas at a saturation temperaturearound 18K, with a volatile radioactiv-ity retention capability of 99.98%.These design goals have been experi-mentally verified with two differentprototype cryo-traps. One of these

solutions will be implemented in thebeam line design of EURISOL.

Alpha emitters. Direct irradiationof actinide targets with high-energy,high-intensity protons results in theproduction of volatile long-lived alphaemitters. The most obvious is radonthat itself conveys little radiologicalhazard, but decays into products (theso-called radon progeny) of consider-able radio-toxicities such as 210Po. Thedose per unit intake of activity ofalpha-particle emitters, is approxi-mately 1,000 times that of beta/gamma-emitting radio-nuclides. Theinstallation should be equipped withdedicated monitoring systems andprocedures to keep under control thealpha radioactivity levels.

Critical group. The critical groupexposure via complex pathways,including the air, water, and food chainboth in normal operation and accidentalsituations must be investigated. For thispurpose, a dedicated EURISOL Toolkitwas created, which gathers the relevantinformation and source data as well asother information or methods alreadyvalidated, accepted, and recommendedby national and international regulatorybodies. This toolkit includes models forassessing the health and environmentalimpact of nuclear facilities that aresuitable for research nuclear reactorsand high-power high-energy particleaccelerators. The EURISOL Toolkit isbeing tested and will be applied for aselected case study characteristic forthe EURISOL Multi-MW target sta-tion, leading to the environmentalimpact assessment both in normaloperation condition as well as in acci-dental situations.

Eventually, we would like to stressthat safety and radioprotection aspectsof the future high power ISOL targetsmust be addressed at the very concep-tual stage of the design studies. The

Concrete, 0 degree, at 1m70

Ca41

Ar39

H3

Fe55

Ca45Ar37

Total

Figure 6. Time evolution of the specific activity of the shielding concrete afterforty years of operation. In this simulation, 2.3 MW are deposited in the Hgneutron spallation source, out of the 4 MW average beam power.



EURISOL design study is a goodexample of this approach.

Discussion and Conclusion Development and engineering.

New target arrangements or materialsaiming at improved heat dissipation orconduction (ISOLDE, TRIUMF), long-term stability (high density UC, PNPIGatchina) or release properties SiC(ISOLDE) were successfully developed.Synthesis of new UCx materials withimproved mechanical properties areunder development at INFN-LNL andwill be evaluated for RIB productionboth at ISOLDE and within the SPESproject. Innovative solutions were pro-posed for windowless neutron spallationsources, modular actinide targets,atomic beam merging in ion-sources,and radioactive ion-beam merging inopen ECRs that are all mandatory assetsfor future high intensity RIB facilities.

Figure of Merit of theEURISOL Facility. The potential ofthe EURISOL facility in producing1,000 different radio-isotopes, withtwo to three orders of magnitude yieldincrease, is within reach. The cross-sections are well known; the decaylosses were extensively measured andassessed; the ion-source efficienciesare confirmed or improved via devel-

opments of Resonant Ionization Laserion-source based on solid state lasers;and improvement in release time wereobtained and are still to be expectedwith increasing experience in theengineering of new materials. Newreaction channels become de factoavailable; in dedicated modular unitscoupled to the neutron spallationsource with the n,x reactions such asthose explored at Louvain-La-Neuve,or being developed at the futureSARAF accelerator at Soreq NRC.

Safety. Safety integration from thestart hints to the need of innovative andflexible solutions in matters of safety.While EURISOL has similarities tohigh-power spallation n-sources and tosmall research reactors, the use of hightemperature pyrophoric actinide car-bide targets, the presence of alphaemitters and the distribution overextended buildings of intense radioac-tive beams and sources of all chemicalnatures, is very specific and requiresdedicated technical standards that willhave to be applied under utmost reli-able safety rules and procedures.

The ambitious targetry goals set bythe EURISOL study group [2] are beingeffectively addressed within theEURISOL-Design Study; this globaltargetry and safety effort involved close

to 200 scientists and technicians across40 institutes from 22 countries. Theircrucial contributions in delivering inno-vative solutions and relevant technicaldevelopments are herby acknowledged.Furthermore, a wide dissemination ofinformation took place, its apex beingthe training of many young scientists inthe most effective manner, namely viathe simulation and realizations of proto-types tested in realistic conditions atoperational RIB facilities.

YACINE KADI, JACQUES LETTRY, AND

MATS LINDROOS

CERN

DANAS RIDIKAS

CEA

THIERRY STORA

CERN

LUIGI TECCHIO

INFN

References 1. http://www.eurisol.org and references

therein. 2. “The EURISOL report,” Ed. J. Cor-

nell, GANIL, Caen, 2003, Europeancommission contract No. HPRI-CT-1999-500001.



A New 6MV Accelerator Mass Spectrometer for the University of Cologne

Accelerator Mass Spectrometry(AMS) is a technique to measure long-lived radioisotopes with very highsensitivity. The radioisotopes can beof natural origin such as cosmogenicnuclides produced by cosmic rays orof anthropogenic origin such asnuclides produced in nuclear fuel pro-cessing. Since its development in1977 AMS has revolutionized thefield of radionuclide dating. There isnowadays a wide range of applicationsfor AMS in various fields like earthand ocean sciences, archaeology,hydrology, pollution studies, bio-chemistry and biomedicine [1].

Due to the increasing demand for“standard” AMS measurements (10Be,14C, 26Al, 36Cl, 41Ca, 129I) and thewish for the development of newtechniques the German ResearchFoundation (DFG) decided in 2007to fund a new 6 MV high performanceAMS user facility. All German uni-versities and research institutionswere invited to apply with a detailedinfrastructure proposal and a strongin-house research plan. The applica-

tion of the University of Cologne,which was a combined effort of sci-entists from the Institute of Geologyand Mineralogy, the department ofGeography, and the Institute forNuclear Physics, got the highest rankand Cologne was chosen as the loca-tion of the new accelerator. The Uni-versity support for the new researchfacility is tremendous, including sixnew positions, the building of labora-tories for sample preparation, all civilconstruction costs, and the runningcosts during the startup period. Theplanned amount of beam time attrib-uted to different AMS applications,developments, and maintenance isgiven in Figure 1.

The main local research programwill focus on applications in the geo-sciences. Examples are exposure dat-ing of glacial moraines important forglobal climate change studies, theinvestigation of fault movements fortectonics and paleoseismics, the quan-tification of landscape evolution, orthe study of ocean currents. The Insti-tute for Nuclear Physics adds a

research program in Nuclear Astro-physics. In this very active fieldexperimental studies are often facedwith measurements of extremely lowcross-sections below the detectionlimits of conventional techniques. Thepotential of AMS to detect ultra-smallamounts of long-lived isotopes allowsunique measurements of astrophysi-cally important reactions and hasalready been successfully applied inseveral experiments in the last years[2,3]. An increasing number of experi-ments of astrophysical implicationusing AMS are under way [4–6].Recently, AMS measurements haveshown an increased amount of super-nova-produced 60Fe on Earth, fromwhich the spectacular conclusion maybe derived that a supernova eventoccurred nearby the earth approxi-mately 2.8Myr ago [7]. This discoveryhas triggered further AMS experi-ments of several other supernova-produced isotopes, for example, 182Hfand 244Pu, which are currently underdevelopment [8,9]. Such signaturesserve as stringent tests for astrophysi-cal models. Figure 1. Planned distribution of beam time.

Figure 2. The main experimental hallof the existing FN Tandem.



The existing infrastructure at theInstitute for Nuclear Physics [10]facilitates the setup of the new AMSsystem enormously. It will be mountedin the second basement floor of theunderground accelerator buildingbelow the existing experimental hall(see Figure 2). The new AMS areawill be separated from the existing FNtandem area with respect to all radia-tion protection issues, so that theaccelerators are not interfering witheach other for what concerns access.

Work has already started to pre-pare the technical infrastructure forthe new AMS area, for example,electrical power, cooling water, andair conditioning. The gas systemitself for both accelerators will becompletely renewed except thestorage tanks, which will be used incommon by both accelerators. Thepresent insulating gas of the FN tan-dem will be converted from a N2/SF6

gas mixture to pure SF6. Thus it willbe possible to operate the FN tandemat a low pressure of only 6–7 bar.Except for a common gas system the

accelerators can be operated com-pletely independent from each otherfrom a new common control room.Figure 3 shows the layout of theAMS system consisting of a lowenergy mass spectrometer, a 6 MVTANDETRON accelerator, and thehigh-energy mass spectrometer.

The system will be built by HighVoltage Engineering, Amersfoort, TheNetherlands. The low energy massspectrometer consists of a multi sam-ple sputter ion source that can beloaded with up to 200 cathodes. It canbe operated with both solid as well asgaseous samples admitted from groundpotential, allowing the on-line integra-

tion of elemental analyzers. The sourceis followed by a second order corrected54° electrostatic analyzer (ESA) and90° magnet with achromatic design foroptimal ion optics and a high massresolution of up to m/�m = 700.Because the ESA can be mechani-cally switched from +54° to −54° asecond Ion source can be mounted inparallel. The chamber of the 90°magnet can be put on a high voltagepotential via a fast high voltagebouncer power supply for a cyclingfrequency as high as 100 Hz.

The 6 MV Tandetron accelerator,which uses a parallel fed Cockroft-Walton generator as a charging sys-tem, is equipped with an all-solid-statehigh voltage power supply. Theexpected low ripple and high stabilityis obtained without a corona-stabiliza-tion. A turbo-molecular pump in theterminal and large diameter accelerat-ing tubes ensure good vacuum in thetubes during operation. The accelera-tor can be operated with foil and gasstripper. Because of the absence ofmoving parts, except of a rotatingshaft driving a generator in the termi-nal, we expect virtually maintenancefree operation and stable performanceover time.

In the high-energy mass spectrom-eter the rare isotopes subsequentlypass a 90° high mass resolving analyz-ing magnet and two 35° electrostaticanalyzers before they are directed into

3240

control room

ESA 35°Faraday-cup unit

90°-magnet

switching magnet

6MVtandetron

LE mass-spectromter

absorber foil

corridor

workshop

corridor

gas storage

office office office

Figure 3. Layout of the new AMS facility in the second basement.

Table 1. Specifications of the ordered AMS facility.

Element Isotopes Background Precision At isotope ratio

Graphite 14C/12C 5 E-16 ≤0.5% 1 E-12

Beryllium 10Be/9Be 3 E-15 ≤3% 1 E-12

Aluminium 26Al/27Al 5 E-15 ≤3% 1 E-11

Chlorine 36Cl/35Cl 3 E-15 ≤3% 1 E-13

Iodine 129I/127I 5 E-14 ≤2% 1 E-10



a switching magnet. The switchingmagnet forms a third analyzing ele-ment which is needed especially forheavy elements like, for example,239U, 244Pu for a further backgroundreduction and it offers the possibilityto use different detection beam-linesfor different isotopes in order tomeet the specific requirements foreach isotope.

For the analyses of elements like14C, 26Al, and 129I one beam-line isequipped with a gas-ionization cham-ber. A second beam-line supports theapplication of an absorber foil tech-nique for isobar suppression for 10Beand 36Cl via a secondary stripper foilof Si3N4 followed by a 120° magnetand a high-resolution gas detector.Thus it becomes possible to use gasstripping for 36Cl detection instead ofthe necessity of foil stripping in theterminal. This technique makes the36Cl analysis less sensitive to sulfurcontent in the sample, which allows ahigher ion source current to be usedthat counterbalances partially lossesin detection efficiency by the addi-tional absorber foil. Other ports areavailable for future extension of thesystem like, for example, a time-of-flight detector system especially forheavy isotopes. The stable isotopesare measured in high precision Fara-day cups with combined electrostaticand magnetic secondary electron sup-pression. The measurement of thestable isotopes as well as of the rareisotope is synchronized with the cor-responding injection periods. Thespecification for typical isotopes isgiven in Table 1.

The system has been ordered anddelivery is expected in the beginningof 2010. The set up and commission-ing of the system at the Institute willneed about 9 months. We thereforeexpect first operation for the end of

2010, which almost exactly coincideswith the first forty years of successfuloperation of the 10 MV Cologne FNTandem accelerator.

1. C. Tuniz, W. Kutschera, and D. Fink,Accelerator Mass Spectrometry, CRCPress, Boca Raton (2009).

2. A. Arazi, T. Faestermann, J. O.Fernandéz Niello, K. Knie, G.Korschinek, M. Poutivtsev, E. Richter,G. Rugel, and A. Wallner, Phys. Rev.C 74 (2006), 025802.

3. H. Nassar, M. Paul, I. Ahmad,D. Berkovits, M. Bettan, P. Collon,S. Dababneh, S. Ghelberg, J. P. Greene,A. Heger, M. Heil, D. J. Henderson,C. L. Jiang, F. Käppeler, H. Koivisto,S. O’Brien, R. C. Pardo, N. Patronis,T. Pennington, R. Plag, K. E. Rehm,R. Reifarth, R. Scott, S. Sinha, X.Tang, and R. Vondrasek, Phys. Rev.Lett. 94 (2004), 092504.

4. F. Käppeler, Nucl. Instr. and Meth. inPhys. Res. B 259 (2007), 663.

5. D. Robertson, C. Schmitt, P. Collon, D.Henderson, B. Shumard, L. Lamm,E. Stech, T. Butterfield, P. Engel,G. Hsu, G. Konecki, S. Kurtz,R. Meharchand, A. Signoracci, andJ. Wittenbach, Nucl. Instr. and Meth.in Phys. Res. B 259 (2007), 669.

6. A. Wallner, M. Bichler, I. Dillmann,R. Golser, F. Käppeler, W. Kutschera,M. Paul, A. Priller, P. Steier, andC. Vockenhuber, Nucl. Instr. andMeth. in Phys. Res. B 259 (2007), 677.

7. K. Knie, G. Korschinek, T.Faestermann, E. A. Dorfi, G. Rugel,and A. Wallner, Phys. Rev. Lett. 93(2004), 17.

8. C. Vockenhuber, A. Bergmaier, T.Faestermann, K. Knie, G. Korschinek,W. Kutschera, G. Rugel, P. Steier, K.Vorderwinkler, and A. Wallner, Nucl.Instr. and Meth. in Phys. Res. B 259(2007), 250.

9. G. Raisbeck, T. Tran, D. Lunney, C.Gaillard, S. Goriely, C. Waelbroeck,and F. Yiou, Nucl. Instr. and Meth. inPhys. Res. B 259 (2007), 673.

10. J. Jolie, H. Paetz gen Schieck, J.Eberth, and A. Dewald, Nucl. Phys.News 12 (2002), 4.

ALFRED DEWALD, JAN JOLIE, AND

ANDREAS ZILGES

Institut für Kernphysik,Universität zu Köln

impact and applications


Masses of Short-Lived Nuclides: Precision Measurement Techniques and Applications

Similar to fingerprints, atoms canbe identified by their masses—whenweighted with sufficient accuracy. Themass of an atom reflects all internalforces and thus carries information onthe strong, weak, and electromagneticinteractions both of the nucleons andthe electrons. Thus, atomic masses areaddressed in numerous applications, atdifferent levels of accuracies. Foratomic-physics applications, like QEDtests or electron binding energies, rela-tive mass uncertainties down to thecurrent limit of about �m/m ≈ 10−11

can be essential. In contrast, nuclearbinding energies are on the MeV scaleand �m/m = 10−6 to 10−8 is sufficientfor, for example, astrophysics or testsof nuclear models (Table 1).

The method of choice to reach amass precision of 10−8 and better onspecific long-lived radio-nuclides isPenning trap mass spectrometry. Formass mapping of the nuclear chart andfor nuclides having shorter half-lives,storage-ring mass spectrometry is acomplementary approach [1]. Bothmethods use frequency measurementsfor the mass determination. The resolvingpower and accuracy rely on a sufficientlylong measurement time and thus ion stor-age is an essential ingredient. In the fol-lowing, both techniques and selectedapplications in nuclear physics will behighlighted. Other approaches of massspectrometry on short-lived nuclides arefound in recent reviews [2,3].

Production and Separation of Nuclides Far from Stability

A prerequisite for any mass mea-surements of exotic nuclides is their

production and separation. A variety ofnuclear reactions is used to produceradioactive nuclei: fission, target spalla-tion, projectile fragmentation, fusion,deep inelastic, and nuclear transfer reac-tions [4]. All these reactions produce awide variety of nuclei. Therefore, it isnecessary to separate the nuclides ofinterest from the unwanted contami-nants. Two main complementary sepa-ration techniques were developed,namely Isotope Separation On-Line(ISOL) and in-flight separation. In theformer method, the exotic nuclei areproduced and stopped in thick targets(up to a few 100 g/cm2). Extraction pro-cesses are chemistry dependent and cantake seconds, which, on one hand,restricts the nuclei that can be investi-gated [5]. On the other hand, the ISOLbeams are superior in terms of intensityand optical quality and ideally suitedfor Penning-trap spectrometers.

In the in-flight method, the primarybeams impinge on a thin target. Thus,the reaction products emerge with highkinetic energies, mainly in the forwarddirection. The fragments are highlyionized, which allows an efficient elec-tromagnetic separation “in-flight.” Asthe separation depends mainly on kine-matical properties, all nuclides can beprovided without any chemical restric-tion. The disadvantage of the inevitablephase-space enlargement of the sepa-rated beams can be compensated bycoupling to storage-cooler rings.

In order to combine the best of bothmethods, a hybrid technique has beendeveloped, whereby the fragments sep-arated in-flight are thermalized in a gascell. After fast and efficient extrac-tion from the gas cell the rare-isotope

beams of ISOL-quality are post-accelerated.

Due to their small production cross-sections and short lifetimes the nucleifar away from the valley of b-stabilityare difficult to investigate. Therefore,very efficient and fast experimentaltechniques had to be developed. Beamsof separated extremely unstable nucleiare already available for precision massspectrometry at: ISOLDE at CERN inGeneva, Switzerland, SHIP at GSI inDarmstadt, Germany, the IGISOLfacility in Jyväskylä, Finland, theNSCL facility at Michigan State Uni-versity, Argonne, USA, as well as atTRIUMF in Vancouver, Canada.

Penning-Trap Mass Spectrometry A strong magnetic field confines

the ions radially in the Penning trapwith the Lorentz force leading to cir-cular orbits with the mass-characteris-tic cyclotron frequency of revolution

For an ion with charge q and mass min a magnetic field B along the direc-tion of the magnetic field lines, that is,in the axial direction, harmonic con-finement is obtained by an additionalweak static electric quadrupole poten-tial. In addition, this combination ofelectric and magnetic fields leads to alow-frequency circular drift motioncentered in the trap axis (Figure 1,right). Thus, the trajectory of a storedion consists of three independent har-monic modes with the correspondingmagnetron ( f−), modified cyclotron( f+) and axial frequency ( fz) [6]. The

fqB

mc =1

2p. (1)



sum f−+f+=fc, is equal to the cyclotronfrequency in free space, that is, in theabsence of an electric field. This “true”cyclotron frequency can be determinedby applying radiofrequency signals at fre-quencies fHF close to fc and subsequentlyejecting the ions into a drift region. In this“time-of-flight ion cyclotron resonance”(ToF-ICR) method a resonant excitationof the ion motion results in a reduced ToFto an ion detector. The frequency isscanned and the center of the ToF reso-nance determines fc and thus the mass ofthe ion of interest. Masses of radionu-clides with production rates of only 100ions per second and half-lives as short as10 ms have been measured with anuncertainty as low as 10−8.

Storage Ring Mass Spectrometry In contrast to several Penning

trap facilities [7], there is only onestorage ring that is presently pursuinghigh-precision mass measurements,namely the experimental storagering ESR at GSI Darmstadt [8]. Thenuclides of interest come as highlycharged ions (bare, H-, and He-like)from the in-flight Fragment Separa-tor (FRS) [9] and are injected as a500-ns bunch into the ESR [10]. The

frequencies f of the circulating ions(f ≈ 2 MHz) can be related in first-order approximation to their mass-to-charge ratios (m/q) by the followingexpression [11]:

where g is the relativistic Lorentz

factor and is the so-

called momentum compaction fac-tor, which characterizes the relativevariation of the orbital length C per rel-ative variation of the magnetic rigidityBr. Obviously, an unambiguous rela-tion between f and m/q is obtainedwhen the velocity-dependent term dis-appears. There are two complementaryways to achieve this (Figure 2):

1. In Schottky-Mass-Spectrometry(SMS) [12] �v/v → 0 is reachedby the electron cooling and f ismeasured by Fourier analysis ofthe image charges induced on twopick-up electrodes by the circulat-ing ions. Relative mass uncertain-ties below 10−7 [13] can bereached, however, due to the time

needed for the electron-cooling,only for nuclides with half-livesexceeding a few seconds.

2. For Isochronous-Mass-Spectrome-try (IMS) [14] the storage ring isoperated at g2 = 1/ap, that is, the ionfrequencies are independent of theirvelocity spread. IMS gives accessto nuclides with half-lives evendown to microseconds at relativeuncertainties in the order of 10−6.Ion detection is achieved via sec-ondary electrons that are producedat each passage of the circulatingion through a foil mounted insidethe ring aperture. The ions typicallyrun for a few hundred revolutions.

Both methods, SMS and IMS, areextremely efficient. �(m/q)/(m/q) of2.5% and 13%, respectively, can be cov-ered simultaneously in one ion-opticalsetting. Moreover, the mass can bedetermined from a single ion. Thesetechniques are therefore ideally suited tomap large areas on the chart of nuclides.

Applications of Nuclear Masses and Mass Spectrometry

Isomer Resolution Many nuclides have long-lived

isomeric states—often with unknown

Δ Δ Δf

f

m q

m q

v

vp p= − + −a g a( / )

/( ),1 2 (2)

ar rp

C C

B B

ΔΔ

/

( ) /

Table 1. Fields of applications and respective required relative uncertainty of the measured mass δm/m as well as absolute uncertainty δm (in keV) for a nuclide of mass A = 100.

Field of application Research area addressed dm/m dm (keV)

Chemistry Identification of molecules 10−4–10−7 10 keV–10 MeV

Nuclear Physics Nuclear structure, mass models 10−6–10−7 10–100 keV

Astrophysics Stellar nucleosynthesis processes 10−6–10−7 10–100 keV

Weak Interaction CVC hypothesis, CKM unitarity ≤10−8 ≤1 keV

Metrology Fundamental constants ≤10−9 ≤100 eV

Atomic Physics Binding energies, QED ≤10−10 ≤10 eV

Particle Physics CPT invariance test ≤10−11 ≤1 eV

B f-

fz

f+

Figure 1. Left: Sketch of a Penning trap(diameter about 2cm). Right, top:Trajectory of charged particles insidethe trap with typical amplitudes of 1mm:Superposition of the three independentmotional modes. Right, bottom:Projection onto the radial plane.



excitation energies. If unresolved themeasurement leads to deviations fromthe correct ground-state mass values.To avoid such errors resolving powersR= m/�m =106 and above are required.On the other hand, high-resolutionmass spectrometry allows to determineisomeric-state sequences, to prepareisomerically pure beams [16], and evento discover nuclear isomers, for exam-ple, 65Fe at LEBIT [17] (left part ofFigure 3). R≈ 106 corresponds to, forexample, an excitation time of TRF ≈1 sat f≈ 1 MHz, that is, B≈ 7 T for singlycharged ions of mass A≈ 100 in a Pen-ning trap. If the half-lives allow, evenhigher resolving powers can be reachedby further increasing TRF. Alterna-tively, because nc scales with q, R canbe improved considerably by increas-ing the charge state, as planned forTITAN at TRIUMF/Vancouver [18].

Another way to resolve isomericand ground states is based on the factthat a single stored ion can only bepresent in one or another state. This isoften used in SMS. Isomers with verysmall excitation energies can beresolved, for example, a new isomericenergy of only 103(12) keV was dis-covered [19] (right part of Figure 3).

Proton-Neutron Interactions and the New Masses

The mass M(N,Z) of a nucleuswith N neutrons and Z protons is oneof the most fundamental characteris-tics because the binding energyB(N,Z)={NMn +ZMp −M(N,Z)}c2 (withneutron mass Mn and proton massMp) contains the summed effects ofall nucleonic interactions. Thus thegrowth in number and accuracy ofnuclear mass values contributes

again and again to our understandingof nuclear structure. In particularmasses of very neutron-rich nucleican reveal new nuclear propertiesdue to the strong asymmetry of theirproton-to-neutron ratio. The storage-ring mass spectrometry has provenmost powerful, providing in a singleexperiment several hundreds ofmass values [12]. This gives anoverview of the hills and valleys thatform the mass surface M(N,Z) andallows to study the influence of cer-tain nuclear configurations andinteractions.

Various correlations betweennucleons can be extracted from massdifferences of neighboring nuclei. Forinstance, a systematic study of thewell-known like-nucleon pairing cor-relations has been performed [20].Another class of interactions is that of

Figure 2. Schematic illustrations of the storage ring mass spectrometry. Left: Schottky Mass Spectrometry (SMS); Right:Isochronous Mass Spectrometry (IMS) at the ESR [15].



the last proton(s) with the last neu-tron(s), defined by

dVpn(Z,N) = ¼[{B(Z,N) − B(Z,N-2)}−{B(Z-2,N)−B(Z-2,N-2)}]

for even-even nuclei. For example,dVpn values show striking singularitiesfor nuclei with N = Z, reflecting theT = 0 interaction. Recently, dVpn valuesfrom masses of the latest Atomic MassEvaluation AME2003 [21] high-lighted the variations of the p-n inter-action [22,23]. dVpn values describeand explain the shell structure andorbit occupations near the Fermi sur-face, for example in the rare-earthregion (see Figure 4). Because dVpn

varies by about 150–250 keV in agiven region, its uncertainties shouldbe below 30–50 keV. Because fourmasses enter in the dVpn(Z,N) equa-tion, trends can be distinguished

unambiguously only if the uncertain-ties of the individual mass values areof the order of 10–20 keV, that is, dm/m < 1 × 10−7 for nuclides above A ≈ 100.

Testing of New Mass Models by Nuclear Masses Far from Stability

Due to the lack of an exact descrip-tion of the strong interaction and thecomplexity of the many-body nucleonicsystem, the nuclear binding energy is notreadily predicted by ab initio theories.Instead, one has to rely on phenomeno-logical (macroscopic-microscopic) massmodels or mass formulas aiming at aquantitative prediction of atomicmasses [2]. They make use of a set offree parameters (up to several hun-dreds), which have to be constrained byfitting to experimental data. In particu-lar data far from the valley of b-stabilitycan act as test cases for the predictive

power of the models and formulas, asdemonstrated in Figure 5.

In the last few years there has beensignificant progress in the constructionof microscopic mass models on thebasis of self-consistent mean-fieldmodels. Large-scale fits of Skyrme-typeinteractions to all available massesbecame feasible [25]. When includingphenomenological correction terms forcorrelation effects, these Skyrme-forcecalculations compete with the best avail-able microscopic-macroscopic models.Calculations with Gogny-type interac-tion are also on the way. More recenttheoretical developments allow thelarge-scale microscopic calculation ofcorrelation energies, either in the frame-work of a symmetry-restored GeneratorCoordinate Method [26], or a micro-scopic Bohr-Hamiltonian [27]. There isalso a promising progress in RelativisticMean Field models. We note that inaddition to masses all these microscopicmodels aim to describe other nuclei prop-erties such as, for example, nucleondensities. However, further development

Frequency difference [kHz]

Inte

nsity

[arb

. uni

ts]

1

10

1

10

Inte

nsity

[arb

. uni

ts]

Ge69 32+Ce1 58+25

singleion

singleion

E=103(12) keV

Ce1 58+25Ge69 32+

-0.1 0 0.1 0.2 0.3

Figure 3. Left: Time-of-flight cyclotron resonance of 65Fe2+ (ground state “gs”and isomeric state “is”) using an excitation time of 50 ms. A fit of the theoreticalline shape to the data is added [17]. Right: Schottky frequency spectra of singlestored 125Ce58+ ions in the ground and isomeric states. This isomer was notknown before Ref. [19]. The peaks of 69Ge32+ ions are shown as a reference.

Figure 4. δVpn values in the rare-earthregion in a Z-N chart, highlighting thesymmetry of δVpn with respect to shellclosures and the need for data in thelower right quadrant.



of the models is necessary to include allimportant correlation effects simulta-neously, but the present results are mostencouraging as they improve the pre-dicted masses around shell closures. Fora more reliable extrapolation of massesnot only the models, but also the effec-tive interactions used and the protocolsfor the adjustment of their coupling con-stants have to be improved. To that aim,it is highly desirable to collect furtherdata on neutron-rich nuclei beyond theneutron shell closures that separate thestable nuclei from the drip line. Theirstructure is mainly determined by thesingle-particle states above the shell clo-sures, which are not completely con-strained by the data on more stablenuclei. Here, the new facilities underconstruction at, for example, FAIR, maydeliver a large number of new data,either using a storage ring or the Pen-ning trap technique.

Test of the Conserved Vector Current Hypothesis and the Unitarity of the CKM Matrix

The Cabibbo-Kobayashi-Maskawa(CKM) quark-mixing matrix V param-eterizes the weak charged currentinteractions of quarks. Today the bestpossible direct test of its unitarity,which is a fundamental concept of theStandard Model, involves the top row ofV, namely |Vud|2+|Vus|2+|Vub|2=1−�. Inthe Standard Model with a unitaryCKM matrix, � is zero.

The most precise value for theVud element can be extracted fromthe vector coupling constant GV

derived from the mean Ft value ofsuperallowed nuclear b-decay, inconjunction with the Fermi cou-pling constant from m-decay Gm:Vud

2 = GV2 /Gm

2. Together with parti-cle physics data from K and B mesondecay, this can be used to test CKM

unitarity. The experimental Ft valueis expressed as:

Ft ≡ ft (1 + dR)(1 − dC)= K / (2|Vud|2 Gm2 (1 + �R)) = const.,

where dR is the nucleus-dependentradiative correction, dC the isospin-symmetry-breaking correction, and�R the nucleus-independent radiativecorrection [29]. Experimentally, Ft isaccessible by a combination of thedecay energy Q, the half-life T1/2, andthe branching ratio R. The Q valueenters to the fifth power into the calcu-lation of the statistical rate function fand thus the masses of the mother andthe daughter nuclei are needed with aprecision of at least 1× 10−8 in order toreach a relative uncertainty of the orderof 0.1% on Ft. This is one of the mostchallenging applications of nuclear pre-cision mass measurements, which canbe addressed by Penning traps only.Here, concerning nuclear mass mea-surements, especially the Penning trapexperiments at Argonne (CPT) [30], atISOLDE (ISOLTRAP) [31], LEBIT[32], and IGISOL (JYFLTRAP) [33]have made significant contributions.

Recently improved calculationsof the isospin-symmetry-breaking cor-rections addressed 20 superallowed b

Figure 5. Differences in mass predictions of various theoretical models andexperimental data to predictions of the Hartree-Fock-Bogoliubov (HFBCS2001) mass model as a function of N for tin isotopes (Sn, Z= 50). Since the modelparameters are adjusted to measured masses, the agreement is very good wheremasses are known [24].

Z OF DAUGHTER

t-val

ue (s

)

14O 26 mAl 34Cl 38 mK

42Sc46V

50Mn54Co

10C

5 3025201510 35

3070

3080

3090

3100

3060

22Mg 34Ar74Rb62Ga

Figure 6. Corrected experimentalFt-values for the 13 best-knownsuper-allowed decays [28]. The greyband gives one standard deviationaround the average Ft value.



decays, which cover the nuclear chartfrom 10C to 74Rb [29]. A consistentpicture for the 13 best-known casesconfirmed the conserved-vector-current (CVC) hypothesis, which claimsidentical Ft-values for all transitionsbetween isospin T = 1-analog states onthe 10−4 level (Figure 4). With anaveraged Ft-value of 3072.3(8) s, theup-down element of the CKM matrixresults in Vud = 0.97402(26) and (usingthe Vus and Vub values from the 2006Particle Data Group review) yieldsVud

2 + Vus2 + Vub

2 = 0.9997(10), that is,unitarity is satisfied with in an uncer-tainty of 0.1% [28].

Summary and Outlook The masses of more than 1,000

short-lived radionuclides, that is,about one third of all known nuclides,have been directly determined byPenning trap and storage ring massspectrometry. In many cases relativemass uncertainties down to 10−8 havebeen reached. The huge progress inmeasurement techniques is accompa-nied by recent developments in theion-beam production of the exoticunstable nuclei. Further improvementscan be expected from new researchfacilities with unprecedented rare-isotope production capabilities, suchas, for example, SPIRAL2 at GANIL/Caen [34], FAIR at GSI/Darmstadt[35], Germany, RIBF at RIKEN/Wako [36] or a new advanced rare iso-tope accelerator in discussion in theUnited States [37]. Already the cur-rent measurements span the wholerange from the lightest halo nuclei as,for example, 11Li (recently measuredwith TITAN at TRIUMF [18]) to thesuperheavies like nobelium (which isin the focus of SHIPTRAP at GSI[38]). The new-generation facilitieswill produce nuclei further off the line

of beta-stability, for example, many ofthe nuclides along the astrophysicalr-process, where the mass values playan important role.

Acknowledgment The authors express their grati-

tude to all colleagues within the fieldof high-precision mass spectrometryon short-lived nuclides, especially toR. Casten, J. C. Hardy, and D. Lunneyfor their valuable comments.

References 1. H.-J. Kluge, K. Blaum, and C.

Scheidenberger, Nucl. Instrum. Meth.A 532, 48 (2004).

2. D. Lunney, J. M. Pearson, and C. Thibault,Rev. Mod. Phys. 75, 1021 (2003).

3. K. Blaum, Phys. Rep. 425, 1 (2006). 4. H. Geissel et al., Ann. Rev. Nucl. and

Part. Sci. 45, 163 (1995). 5. U. Köster, Eur. Phys. J. A15, 255 (2002). 6. L. S. Brown and G. Gabrielse, Rev.

Mod. Phys. 58, 233 (1986). 7. L. Schweikhard and G. Bollen (eds.),

special issue Int. J. Mass Spectrom.251 (2006).

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9. B. Franzke, Nucl. Instr. Meth. B 24/25,18 (1987).

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11. F. Bosch et al., Int. J. Mass Spectrom.251, 212 (2006).

12. Yu. A. Litvinov et al., Nucl. Phys. A756, 3 (2005).

13. Yu. A. Litvinov et al., Hyperfine Inter-actions 173, 55 (2006).

14. M. Hausmann et al., Nucl. Instr. Meth.A446, 569 (2000).

15. F. Bosch, J. Phys. B 36, 585 (2003). 16. J. van Roosbroeck et al., Phys. Rev.

Lett. 92, 112501 (2004). 17. M. Block etal., Phys. Rev. Lett. (2008). 18. J. Dilling et al., Int. J. Mass Spectrom.

251, 198 (2006). 19. B. Sun et al., Eur. Phys, J. A31, 393

(2007).

20. Yu. A. Litvinov et al., Phys. Rev. Lett.95, 042501 (2005).

21. G. Audi, A. H. Wapstra, and C. Thibault,Nucl. Phys. A 729, 337 (2003).

22. R. B. Cakirli et al., Phys. Rev. Lett. 94,092501 (2005).

23. Y. Oktem et al., Phys. Rev. C 74,027304 (2006).

24. D. Lunney, private communication(2008).

25. S. Goriely et al., Phys. Rev. C 68,054325 (2003).

26. M. Bender, G. F. Bertsch, and P.-H.Heenen, preprint nucl-th/0410023 (2004).

27. P. Fleischer et al., Phys. Rev. C 70,054321 (2004).

28. J. C. Hardy, private communication(2008).

29. I. S. Towner and J. C. Hardy, Phys.Rev. C 77, 025501 (2008).

30. G. Savard et al., Phys. Rev. Lett. 95,102501 (2005).

31. A. Kellerbauer et al., Phys. Rev. Lett.93, 072502 (2004).

32. G. Bollen et al., Phys. Rev. Lett. 96,152501 (2006).

33. T. Eronen et al., Phys. Rev. Lett. 100,132502 (2008).

34. http://www.ganil.fr/research/develop-ments/spiral2/

35. http://www.gsi.de/GSI-Future/CDR/ 36. http://www.riken.go.jp/engn/r-world/

research/lab/nishina/index.html 37. http://www.sc.doe.gov/np/program/

FRIB.html 38. M. Block et al., Eur. Phys. J. D 45, 39

(2007).

KLAUS BLAUM

GSI Darmstadt, Darmstadt, GermanyMax-Planck-Institut für Kernphysik,

Heidelberg, Germany

YURI A. LITVINOV

GSI Darmstadt, Darmstadt, GermanyPhysikalisches Institut, Justus-Liebig-Universität Gießen, Gießen, Germany

LUTZ SCHWEIKHARD

Institut für Physik, Ernst-Moritz-Arndt-Universität

Greifswald, Germany

meeting reports


The First Workshop on the “State of the Art in Nuclear Cluster Physics”

The Workshop on the “State OfThe Art in Nuclear Cluster Physics”(SOTANCP2008) took place on May13–16, 2008 in Strabourg and washosted by Institut PluridisciplinaireHubert Curien (IPHC). The scope ofthis first workshop brought togetherdifferent groups, both theoretical andexperimental, involved in the study of“Clusters in Nuclei.”

A Theoretical Winter School on“Clusters in Nuclei” had previouslybeen organized in Strasbourg in 2005. Inrecent years, besides the traditionalCluster Conferences series (Cluster ’03held in 2003 in Nara and Cluster ’07held last September in Stratford-upon-Avon, UK as described in Nuclear Phys-ics News Vol. 18, No. 1, p. 25), othermore informal workshops have beenorganized with relatively limited num-bers of participants in Rostock (2003,2004, and 2005), in Munich (2006), andin Osaka (also in 2006). The subjecttreated in these meetings has mainlyconcentrated on alpha particle condensa-tion in nuclear systems (see NuclearPhysics News Vol. 17, No. 4, p. 11).

The purpose of SOTANCP2008was to promote the exchange of ideasand discuss new developments in“Clustering Phenomena in NuclearPhysics and Nuclear Astrophysics”from both the theoretical and experi-mental points of views.

The various aspects of the maintopics of SOTANCP2008 were dividedinto seven sections:

1. Alpha Clustering and NuclearMolecules

2. Alpha Condensates and Analogywith Condensed Matter

3. Clusters in Nuclear Astrophysics 4. Cluster in Superheavy Nuclei 5. Cluster in Radioactivity 6. Clustering in Nuclei far from

Stability 7. Two- and Three-body Reaction

The workshop attracted 95 partici-pants from some 20 different countriesfrom all over the world (North andSouth America, Asia, Australia, andEurope).

Twelve Invited Talks of 40 min-utes and 30 minutes duration werepresented by distinguished col-leagues in their respective area ofexpertise as part of the 15 plenarysessions. As the organizers wished topresent as many as possible of thecontributions in oral form, 55 20- and15-minute talks were also given inthe 4 days of the meeting. The struc-ture of the Hoyle state (Y. Funaki)and its role in element genesis(P. Descouvemont), the formation ofsuperheavy elements (V. Zagrebaev)and giant nuclear systems (S. Heinzand C. Golabek) were among thehighlights that have been the mostactively discussed. Various modelapproaches to the understanding ofalpha-molecular-cluster structure inlight (T. Neff) and medium heavynuclei (Y. Kanada-En’yo), of nuclearmolecules (E. Uegaki), and of clusterradioactivity (D. Poenaru) were pre-sented. The study of exotic fission,fusion-fission (M. Itkis), complexfusion processes (R. K. Gupta andE. Bonnet), as well as three-body reac-tions (D. Baye) has gained a renewedinterest with available radioactive ionbeam facilities. The formats of the

sessions were such that a sufficientamount of time was available forboth discussions and questions. Theclosing remarks were delivered byProfessor Walter Greiner in aremarkable Summary Talk.

The Workshop was sponsored fromIN2P3 and IPHC (Direction de Recher-ches Subatomiques), Strasbourg.

The details of the Workshop pro-gram (including the slides of the talks)may be found at http://sotancp2008.in2p3.fr/. The Proceedings, in a form ofpeer-reviewed papers of most of theorally presented talks, will be publishedin a forthcoming issue of the Interna-tional Journal of Modern Physics E.

Owing to the interest shown bythe community and the potential forfuture research in clustering innuclei, the members of the Interna-tional Advisory Committee (most ofwhom were present at Strasbourgduring the first SOTANCP Work-shop) have agreed to considerSOTANCP as a new series of meet-ings to complement the traditionalCLUSTER Conferences. We lookforward to the new and excitingwork that will be presented at thesecond “SOTANCP Workshop”expected to be held in Brussels in2010 for the occasion of the retire-ment of our colleague ProfessorDaniel Baye.

CHRISTIAN BECK

MARIANNE DUFOUR

IPHC and Universite Louis PasteurStrasbourg

PETER SCHUCK

IPN Orsay

meeting reports


The Halo 08 Workshop, Held at TRIUMF, Vancouver, Canada

More than 50 experts from Europe,Japan, and North America gathered atTRIUMF last March 28–29, in orderto assess current progress in—andfuture directions for—research onhalo nuclei. The Halo 08 Workshopalso provided the opportunity toreview and discuss TRIUMF’s impacton the field. In addition, the workshopcovered future avenues of researchand preparation for TRIUMF’s2010–2015 funding proposal. Theworkshop was organized by SaintMary’s University and TRIUMF,with R. Kanungo as the chair-person.A photograph of the participants isshown opposite.

Halo nuclei are those with extra,weakly bound neutrons or protons forwhich the wave function extends toclassically forbidden regions. Althoughnuclear halos were discovered in 1985,they are still not fully understood.

The atom is often thought of as aminiature solar system with the elec-trons as planets that orbit the centralnucleus. What is fascinating is thatscientists have found that nucleonsthemselves can also play the role ofplanets, orbiting relatively far from anuclear core. As an example, the twohalo neutrons in 11Li have a radiusalmost as large as 208Pb. Importantfindings show that the proton radiusin the Li isotopes shrinks as the neu-tron number increases, but for the11Li halo nucleus, the proton radiusincreases, showing that the protoncore is modified.

Numerous experiments concern-ing halos have been performed at TRI-UMF, including b-decay, chargeradius determination, Penning-trap

mass spectrometry, di-neutron correla-tions, and halo-fusion. The collectionof successes made TRIUMF a naturalchoice for the workshop venue.

For b-decay measurements, threenovel techniques have been devel-oped: (1) polarized 11Li beams forspin-parity assignment of the daughterstates, (2) the use of g-ray line shapesafter neutron emission, and (3) mea-surement of charged particles in finalstates.

High beam quality at low energy isthe hallmark of an ISOL-type facility,such as CERN-ISOLDE and SPIRAL,and now with more intensity at TRI-UMF. As such, the most precise mea-surements of bulk 11Li properties, themass and the charge radius, have nowbeen performed at TRIUMF. As dis-cussed at the workshop, the nuclearcharge radii are a consequence ofimportant advances in both theory andexperiment. The radii were deter-mined by combining high precisionmeasurements of the isotope shift withequally high precision theory for theatomic transition frequencies, includ-ing relativistic and quantum electrody-namic effects. (These large-scalecalculations were performed with thehelp of SHARCNET.) The result is aremarkable confluence of both theoryand experiment at the interfacebetween atomic physics and nuclearphysics.

With the new ISAC-2 facility,11Li(p,t) and 11Li(p,d) inverse-kine-matic transfer reactions were recentlystudied by an international collabora-tion using the active target MAYA.

The energy domain goes fromstopped and cooled ions to reactions

at 1 GeV/nucleon. TRIUMF has themost intense 11Li beam in the worldin the low-energy domain, from keV/nucleon to 5 MeV/nucleon. In thehigh-energy domain, secondarybeams delivered by fragmentationfacilities such as GANIL (France),GSI (Germany), RIKEN (Japan), andthe NSCL (USA) were used to studyhalo nuclei by using high-resolutionand highly efficient and selectiveexperimental setups to study theproperties of these intriguing sys-tems. Here, one of the important sub-jects is to understand how the weaklybound nucleons are correlated: in aweakly bound system the residualinteraction between the valencenucleons will play a significantrole—much more than in normalnuclei, in which the binding to thecore is dominating. This was illus-trated during the workshop by severalcontributions that showed correla-tions between two neutrons observedafter excitation of the system. Thisposes new challenges for ab-initioand phenomenological approaches tonuclear structure and reactions.

Other new phenomena of weaklybound systems were discussed: oneexample is the existence of low-lyingresonances, called pygmy reso-nances. In these systems, a newdegree of freedom arises: the weaklybound nucleons may oscillate withrespect to the strongly bound core,and give rise to low-lying E1 reso-nances. This was also illustrated bythe case of 11Li where evidence for astrong E1 enhancement just abovethreshold was exhibited by Coulombdissociation experiments. Such

meeting reports


phenomena should also exist in manyvery neutron-rich nuclei.

In heavier systems a neutron skindevelops, this is a region with more orless normal nuclear density but consti-tuted essentially by neutrons. Little isknown of the properties of such aneutron skin: the spin-orbit splittingmay be different and the nuclear com-pressibility would differ consider-ably. These questions are related tothe isospin dependence of nuclearmatter properties, and hence to ourunderstanding of nuclear forces with astrong relation to astrophysical scenar-ios. This was also discussed in boththeoretical and experimental context.

The workshop was at the sameoccasion an outlook of future workin this domain and the object of

discussion sessions during theworkshop. The strong potential atTRIUMF for transfer reactions andfusion was stressed and some newideas for instrumentation, such asion and atom traps, and gammaand neutron detection, were alsopresented.

Taking into account the workachieved at TRIUMF already, andwith the excellent existing beams andothers to be developed, TRIUMF willcertainly continue to play a leadingrole in the low-energy studies of halonuclei in particular, and weakly boundsystems in general. Thus, the role ofTRIUMF is a necessary complementto high-energy studies and both arenecessary to achieve a full understand-ing of exotic nuclear systems.

More information can be found atthe workshop website: http://www.triumf.info/hosted/HALO. The Halo-08 International AdvisoryCommittee:

G. W. F. DRAKE

U. of Windsor

H. GEISSEL

GSI/U. Giessen

W. MITTIG

NSCL/MSU

A. RICHTER

TU Darmstadt

I. TANIHATA

RCNP/Osaka

The participants of the Halo-08 workshop at TRIUMF.

meeting reports


N=52: A New Magic Number? A workshop on spectroscopy of

neutron-rich nuclei was held fromMarch 16–21, 2008 in Chamrousse tohonor the career of Jean-Alain Pinston(formerly ILL, then CEA, and finallyISN/LPSC Grenoble) and Janine Gen-evey (ISN/LPSC) who made impor-tant contributions to nuclear physics inGrenoble and retire this year.

Presentations were given aboutrecent experiments, results, andideas for future work on exoticnuclei at existing facilities such asthe ILL, ISOLDE, JYFL, GSI,GANIL, LISOL, ALTO/PARRNe,LNL Legnaro, IKP Cologne, FloridaState University, HRIBF OakRidge, and NSCL Michigan usingbeta-decay, isomer, in-beam, andlaser spectroscopy, as well as life-time and magnetic moment mea-surements.

The sessions were focused on thecurrent status of experimental andtheoretical studies in particularregions of the nuclear chart, such asthose around the magic nuclei 208Pb,

132Sn, 78Ni, and 48Ca. In each sessiona selection of experimental tech-niques were described that eachallow different facets of nuclearstructure to be studied, often bring-ing complementary information tothe understanding of a particularregion.

The enthusiastic presentations bysenior scientists such as Jean-AlainPinston, Janine Genevey, JocelyneSauvage, and Nick and Jirina Stonedemonstrated impressively that thecurrent retirement age in Europerequires reconsideration.

It was shown that the currentlyexisting small and mid-size facilitiesstill have much to offer over the nextfew years. Different presentationsshowed a wealth of new spectros-copy data that was obtained at the35-year-old LOHENGRIN recoilseparator, which had recently beenequipped with two clover Ge detec-tors plus ancillary detectors. SamTabor (FSU) explained how newinformation on excited states of neu-

tron-rich nuclei can be obtained withfusion-evaporation reactions at a“poor man’s radioactive isotope col-lider,” that is, by reactions betweenlong-lived radioactive ion beams andtargets like 10Be and 14C at a univer-sity tandem.

More than one session dealt withthe measurement of nuclear moments.The recoil-in-vacuum method is anelegant way to measure g-factors as by-product of Coulex or fission experi-ments. The advantages and drawbacksof different methods of nuclear orien-tation were discussed in detail. Someparticipants even got a life experienceof the “opposite,” namely, unclearorientation, due to foggy conditionsduring a skiing afternoon.

The workshop also provided timeto reinforce current collaborations, anddiscuss new ones in different areas.The participants were impressed by theILL’s facilities during their guided touron one afternoon of the workshop.

The workshop was attended by 52participants from 26 different insti-tutes and universities. Hopefully thisnumber of 52 will really prove to be“magic” by creating enough momen-tum to bring in the future a largegamma detector array to the ILL for ameasurement campaign of neutron-rich nuclei produced in neutron-induced fission.

ULLI KÖSTER

ILL Grenoble

GARY SIMPSON

LPSC Grenoble

meeting reports


Prof. Yuri Oganessian (on His Seventy-Fifth Birthday)

An International Symposium,“Trends in Heavy Ion PhysicsResearch,” dedicated to Yuri Oganes-sian’s 75th birthday was held fromMay 22–24, 2008 in Dubna. Yuri

Oganessian, a brilliant physicist andexperimentalist, was born on April 14,1933. He is well known for his worksin the field of physics of atomic nucleiand nuclear reactions, and experi-ments on the synthesis of new ele-ments of the Periodic Table.

The meeting was organized byFlerov Laboratory of Nuclear Reac-tions of the Joint Institute of NuclearResearch. Over 100 scientists from 14countries took part in the symposium.The main subject of the conversationwas a general review of the problemsthat are on the agenda of heavy ionphysics today. Experimental advanceto the drip-lines and the study ofexotic nuclei are the mainstream innuclear physics today. This activitycovers a wide range of studies that

were discussed at the symposium:synthesis of superheavy elements andstudies of their chemical properties,search for two-proton radioactivity,discovery of extremely neutron-richisotopes 40Mg, 42,43Al, 44Si, and inves-tigations of the resonance statesbeyond the drip-line 5,7H, 9,10He, and10-13Li. The status of the new experi-mental facilities SPIRAL2 at GANIL(the talk of professor S. Gales), FAIRat GSI (professor H. Stoecker), RIBFat RIKEN (professor T. Motobayashi),and NICA at JINR (professor A.Sissakian) that are under developmentin the leading nuclear centers was oneof the most discussed topics.

SERGEY SIDORCHUK

JINR Dubna

YURI OGANOSSIAN

news and views


ERC Grants Awarded to Nuclear Physicists

The European Research Council(ERC) has awarded two Starting Inde-pendent Researcher Grants (SIRG) ofup to 1.25 million Euros to scientists innuclear physics. The SIRG competitionis an initiative to support excellence andis intended to allow young researchersto start up their own research group at aEuropean Institution.

One grant goes to Finnish AcademyResearch Fellow Paul Greenlees of theUniversity of Jyväskylä Department ofPhysics (JYFL), for his research pro-posal “SHESTRUCT: Understandingthe Structure and Stability of Heavyand Superheavy Elements.”

The-five year project will resolvearound the construction and exploita-tion of the unique new SAGE spec-trometer, which will allow the nuclearstructure of very heavy elements to beinvestigated in detail. SAGE willallow simultaneous measurement ofgamma rays and internal conversionelectrons and be coupled to the RITUgas-filled recoil separator for recoil-decay tagging studies.

The ultimate goal of the project isto learn more about the nuclear struc-ture of superheavy elements. Thespectrometer is currently being con-structed in a collaboration betweenthe Universities of Jyväskylä, theUniversity of Liverpool, and Dares-bury Laboratory, led by Paul Green-lees at JYFL, Rolf-Dietmar Herzbergat Liverpool, and John Simpson atDaresbury. A large part of the fund-ing for SAGE comes from a grantawarded by the U.K. EPSRC (trans-ferred to STFC), which will be com-plemented by the ERC grant. Themajority of the ERC funds will beused to allow a local group tobe formed to maintain and exploit thenew device.

The other grant is awarded toNWO (Dutch Organisation for Scien-tific Research) VENI Fellow AndreMischke of the Science Faculty ofUtrecht University. His proposal isentitled: “Characterization of a NovelState of Matter: The Quark-GluonPlasma.”

This project aims to explore theproperties of the Quark-Gluon Plasma(QGP), a novel state of matter createdby colliding very high energy atomicnuclei, using new and sensitive exper-imental probes based on multi-particlecorrelations. The QGP is predicted bythe fundamental theory of strong inter-actions and is characterized by anequilibrated system of liberatedquarks and gluons that are the constit-uents of atomic nuclei. In cosmology,it is believed that the early expandinguniverse consisted of such plasmaapproximately 10 microseconds afterthe Big Bang.

Heavy-quark particle correlationswill be used as a sensitive probe tostudy the dynamical properties of theQGP. The measurements will be per-formed at the new forefront particleaccelerator, the Large Hadron Col-lider, located at CERN (EuropeanLaboratory for Particle Physics) utiliz-ing the dedicated ALICE (A Large IonCollider Experiment) detector, whichis best suited for comprehensive mea-surements in heavy-ion collisions.

Competition for the SIRG wasvery high, and only projects aimingat new scientific breakthroughs ledby talented researchers were funded.The first call for proposals led to9,167 proposals being submitted,from which only 300 or so proposalswill be funded. Grant agreementnegotiations are ongoing and it ishoped that the projects will start laterthis summer.

RAUNO JULIN

University of Jyväskylä

THOMAS. PEITZMANN

University of UtrechtPAUL GREENLESS ANDRE MISCHKE

news from NuPECC


ENASTRON—The European Nuclear Astrophysics Network: A NuPECC Initiative for a European High-Current Stable Ion-Beam Facility Dedicated to Nuclear Astrophysics Studies

In December 2007, an expertworkshop on “The Future of StableBeams in Nuclear Astrophysics” tookplace at the Congress Center ofthe National Centre for ScientificResearch “Demokritos,” Athens, Greece(www.inp.demokritos.gr/~ESFW). TheWorkshop was fully funded by theEuropean Science Foundation (ESF). Itwas attended by 25 scientists from 10different European countries. TheWorkshop covered the broad andinterdisciplinary field of NuclearAstrophysics and brought togetherexperimentalists and theoreticiansfrom the communities of nuclearphysics, astrophysics, astronomy, andaccelerator technology. The Work-shop focused on the importance ofstable ion-beams on Nuclear Astro-physics studies. The program includedpresentations on scientific problems ofkey importance for the understandingof stellar evolution and nucleosynthe-sis as well as reports on recent devel-opments in the existing ion-beamfacilities and their instrumentation.Half of the program was devoted toround-table discussions on (a) theneed to create a new low-energystable ion-beam facility in Europededicated to Nuclear Astrophysicsstudies, (b) the specifications the newfacility will have to meet in order toresolve outstanding open questions inNuclear Astrophysics, and (c) themajor scientific problems that can bestudied almost exclusively with stableion-beams.

The conclusions of the Workshopcan be summarized as follows:

• Many nuclear reactions across theperiodic table play an importantrole in the aspects of stellarnucleosynthesis. Some of them(about 25 reactions among lightnuclides) are considered as “keyreactions” as they play a decisiverole in the energy production instars as well as in their evolution.The very small cross sections ofthese reactions required indirectmeasurements that improved ourknowledge of stellar evolutionconsiderably. Yet, as their resultssuffer from model dependencies,they cannot replace direct mea-surements. The latter are still con-sidered to provide the clearestsignatures of many astrophysicalphenomena.

• Direct measurements requireintense low-energy stable ionbeams (notably protons, alpha-par-ticles, and some other heaviernuclides) with a suitable energyresolution. Unfortunately, the lead-ing nuclear astrophysics laborato-ries in Europe that fulfill theserequirements are already closed orwill be closed in the near future,whereas others have been “trans-formed” into analytical laborato-ries or irradiation facilities in orderto survive in a highly competitiveenvironment, where the demandfor industrial applications has

washed out many basic researchactivities in the field of low-energynuclear physics. As a result, afacility dedicated to nuclear astro-physics studies in Europe is miss-ing and, therefore, there is anurgent need for Europe to create anew state-of-the art high-currentfacility equipped with advanceddetection techniques.

• A number of nuclear astrophysicsprojects could indeed be realizedin European large-scale facilitiesoffering user support via EC tran-snational access programs. Therequests, however, for the time-consuming experiments necessaryto measure the very low cross-sections face a strong competitionto the high number of beam-timeapplications from other fields suchas nuclear structure. Hence, thereis indeed a need for a new facilitydedicated mainly, but not exclu-sively, to nuclear astrophysics.

• Europe has opened a new era inNuclear Physics: New facilitiesproviding intense radioactivebeams, such as FAIR, SPIRAL2,and HI-ISOLDE will soon be ableto host ambitious nuclear physicsprograms including astrophysics-related important projects requiringunstable ion beams. The operationof such facilities will be realizedthanks to a series of technologicalachievements. Some of these need tobe adopted by the new stable-beamfacility for nuclear astrophysics.

news from NuPECC


Hence, a strong interaction with theRIB-related scientific communityis mandatory.

• The creation of a new low-energyhigh-current stable ion-beam facil-ity for nuclear astrophysics is notaimed at competing with theRadioactive Ion-Beam facilities(RIB) existing in Europe or withthose proposed for the future. Onthe contrary, it will complementand support the physics programsof these facilities.

• Although the new facility is ofimportance for the whole Europeanscientific community, the fundingrequired for its creation is, in com-parison with other projects of thesame scientific impact, muchsmaller, that is, of the order of 8–10 million Euros. As such, thefunding of the new facility cannotbe included as an individual projectin, for example, the EuropeanRoadmap for Research Infrastruc-tures (ESFRI Roadmap). There-fore other funding options shouldbe identified.

The importance of stable ion beams innuclear physics research was indepen-dently documented in the recent scien-tific report produced by ECOS, theEuropean Collaboration on Stable ion-beams (www.nupecc.org/ecos). ECOShas operated in the past two years as aworking group of NuPECC. Accord-ing to the ECOS report, “a low-energy

and high-intensity stable-ion beamfacility dedicated to nuclear astro-physics is seen as vitally important toimprovement of our current under-standing of stellar evolution andnucleosynthesis. . . . Such a facility,built on the earth’s surface, will haveto meet demanding specifications if itis to resolve outstanding open ques-tions in nuclear astrophysics . . .” TheESF Workshop came up with ideasabout how these recommendations canbe achieved in the near future.

The Workshop on “The Future ofStable Beams in Nuclear Astrophysics”met its goals: the framework of theresearch to be conducted in the newfacility as well as the specifications ofthe facility was identified. The experi-mental setups and detector systems tobe embedded in the facility were alsodiscussed. An expert committee for fol-low-up activities was assigned with theaim to produce a physics-case reportand a basic design study for the newfacility and, furthermore, identify initi-atives at a European level that will leadto the creation of this facility. Theexpert committee has recognized thedecisive role of ESF and NuPECC inpromoting and supporting science initi-atives and expressed the interest tolaunch activities under the guidance ofESF and NuPECC.

In this direction, NuPECC hasdecided, in its recent meeting held inZagreb on June 2008, to support anew initiative for a high-current

stable ion-beam facility dedicated toNuclear Astrophysics studies. As aresult a working group coinedENASTRON (European NuclearASTROphysics Network) was giventhe mandate to present the physicscase and a design study for the facil-ity in the next NuPECC Town Meet-ing. ENASTRON members arecurrently M. Arnould (Brussels),L. Gialanella (Naples), S. Harissopulos(Athens), J. Jose (Barcelona), and A.Zilges (Cologne). ENASTRON is anopen Working Group seeking contri-butions from all those sharing thesame scientific interests. With this inmind, and for a successful outcome,ENASTRON is inviting all interestedcolleagues for contributions.

SOTIRIOS V. HARISSOPULOS

On behalf of ENASTRON

obituary


Harald A. Enge (1920–2008)

Tools for Gauging Constituents of Matter: A Bergen Perspective

While his senior MIT colleagueRobert Van de Graaff made the funda-mental constituents of matter fly,Harald Enge made their reactionsrecordable in an intelligible way. Bothwere awarded the Tom W. Bonnerprize in Nuclear Physics, Enge in1984 “For his outstanding contribu-tions to the design of magnetic spec-trometers and beam optics in the fieldof nuclear physics.” They were facilita-tors for nuclear physics, more than aca-demic experimentalists. Enge belongsto a proud line with particular talentfor and interest in accelerators andinstrumentation, many of Norwegiandescent, including Rolf Widerøe,Ernest O. Lawrence, Odd Dahl, andKjell Johnsen.

Harald A. Enge, who passed awayon April 14, age 87, was born inFauske in Northern Norway in 1920.He joined the staff of the newlyfounded University of Bergen (UoB)in 1948, having just graduated with anEngineering Diploma from the Nor-wegian University of Technology(NTH). Charged with a dream ofdoing electrical engineering, Engeended up in physics instead.

“Norwegian scientists are cur-rently involved in work on splittingthe atom that is being carried out inthe USA. Such work is now also beingdone in Norway. In Bergen there is aspecial institute where Norwegians,under the leadership of Americancolleagues, perform investigationsrelated to the splitting of the atom.”This 1947 commentary in “Red Star,”Moscow, illustrates how easily openinternational research could be misin-terpreted in the post-war years. The

backbone of the Bergen activity waspeople like Odd Dahl (soon to bedirector of the early-CERN PS group)and Helmer Dahl, both working at theneighboring Christian MichelsenInstitute (CMI), who had returnedfrom the United States and the UnitedKingdom, and Bjørn Trumpy, profes-sor of physics and the first UoB rec-tor. All three were filled withambition to bring Norway into themodern atomic age.

The main assets of Bergen’sKjernefysisk Laboratorium were a Vande Graaff (the second one in Bergen),and a betatron. A magnetic spec-trograph, built by Enge, is still in Ber-gen; another and larger one he alsobuilt is still at MIT. These early mag-netic spectrographs ran under the nameBrowne-Buechner, his senior collabo-rators at MIT. Enge moved to MIT in1955 to become an assistant professor,having earned a doctorate in physicsfrom UoB based on research he hadpartly done at MIT on a student pro-gram in 1950 and 1951. Enge became afull professor at MIT in 1959.

Enge’s work while in Bergen keptthe contacts with MIT alive. As aconsequence he was “head-hunted” byW. W. Buechner, the leader of MIT’sVan de Graaff group, who came tovisit Bergen. It did not help to keephim home that CMI was instrumentalin the design of JEEP (1951), Nor-way’s experimental nuclear reactor atKjeller near Oslo, the first one outsidethe monopoly of the big powers. Nei-ther did early CERN work in Bergenon the future Proton Synchrotron,assisted by Brookhaven visitors Johnand Hidred Blewett.

Enge left Bergen for greateropportunities than Norway couldoffer. Was this brain-drain a com-plete loss for Bergen? It would havebeen if the Bergen group had notused the MIT contact as a steppingstone for its further internationaliza-tion. Thus, in the 1960s and 1970stens of students took data for theirtheses from the MIT lab and its Engemulti-gap spectrometer. They couldalso support their work by readingEnge’s popular textbook, Introduc-tion to Nuclear Physics (Addison-Wesley 1966). Enge spectrographsare still part of the inventory ofmany laboratories, and not only fornuclear physics applications. Googleprovides a fast entry to Enge’s heri-tage. His work and what he inspiredlives on.

JAN S. VAAGEN

University of Bergen, Norway

calendar


August 31–September 5 Dresden, Germany. 16th International

Conference of ion Beam Modification ofMaterials

http://www.ibmm2008.org/frsindex_html.asp

September 1–7 Zakopane, Poland. Zakopane Confer-

ence on Nuclear Physics http://zakopane2008.ifj edu.pl/

September 7–13 Ryn, Poland. ENAM08 http://enam08.fuw.edu.pl/

September 8–11 Ulaanbaatar, Mongolia. Ulaanbaatar

Conference on Nuclear Physics andApplications

http://www.monamescienc.org/ulaanbaatarconference.html

September 14–18 Lanzhou, China. 7th International

Conference on Nuclear Physics as StorageRings, STORI’08

http://ribll.impcas.ac.cn/conf/stori08/

September 15–18 Vienna, Austria International Confer-

ence on Exotic Atoms EXA08 http://www.oeaw.ac.at/smi/event/exa08/

September 16–19 Vienna, Austria International Confer-

ence on Low Energy Antiproton PhysicsLEAP08

http://www.oeaw.ac.at/smi/event/leap08/

September 17–19 Rhodos, Greece. EURONS Town

Meeting http://www.gsi.de/informationen/jofu/

EURONS/TownMeeting Rhodos.html

September 22–26 Chicago, USA. International Confer-

ence on New Aspects of Heavy-Ion CollisionsNear the Coulomb Barrier FUSION08

http://www.phy.anl.gov/fusion08/

October 7–11 München, Germany 3rd Biennial

Leopoldina Conference on “DARKENERGY”

http://www.mpe.mpg.de/events/dark-energy-2008/

October 10–18 Erice, Sicily, Italy Critical Stability of

Quantum Few-Body Systems http://lpsc.in2p3.fr/Indico/conference

Display.py?confld=29

November 3–5Pisa, italy. Unbound Nuclei Workshophttp://www.df.unipi.it/~angela/pisa.8.htmt

November 9–14 Eilat, Israel. 18th Particles And Nuclei

International Conference PANIC 08 http://www.weizmann.ac.il/conferences/

panic08/

November 17–19CERN Geneva, Wsitzerland. Isdde

Physics Workshop and Users Meeting http://indico.cem.ch/conferenceDisplay.py?

confId=36293

December 1–5 Queenstown, New Zealand. Interna-

tional Conference on Interfacing Structureand Reactions at the Centre of the Atom

http://www.kernz.org

2009January 26–30

Bormio, Italy. XLVII InternationalWinter Meeting on Nuclear Physics

http://panda.physik.uni-giessen.do:8080/indics/conferenceDisplay.py?confId=7

March 16–20 Bochum, Germany. European Nuclear

Physics Conference http://www.epl.rub.de/EUNPC

March 21–24Prague, Czech Republic. International

Conference on Compating in High Energyand Nuclear Physics CHEP’ 09

http://www.particle.cZ/conferences/chep2009/

March 29–April 4 Knoxville, Tennesse, USA. Quark Mat-

ter 2009 http://www.phy.ornl.gov/QM09

March 30–April 1 Pisa, Italy. EURISOL Design Study

Town Meeting http://www.eurisol.org/site01/town_

meeting- t-202.html

May 4–8Vienna, Austria. International Topical

Meetingon Nuclear Research Applica-tions and Utilization of Accelorators(AccApp’09)

http://www-pub.iaea.org/MTCD/Meetings/Announcements.asp?confId=173

June 2–5 Mackinac Island, Michigan, USA. 3rd

International Conference on “Collec-tive Motion in Nuclei Under ExtremeConditions” (COMEX 3)

http://meetings.nscl.msu.edu/COMEX3/

September 27–October 3 Milos, Greace. 8th European Research

Conference on Electromagnetic Interac-tions with Nucleons and Nuclei (EINN2009)

http://www.iasa.gr/EINN_2009

More information available under: http://www.nupecc.org/calendar.html . . . and check also http://www.ect.it®MEETINGS

nuclear physics newswieland/paper_wieland/npn183.pdf · 2008. 11. 12. · nuclear physics news...

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