r&d on scintillating crystals for the r b...

H. Alvarez Pol R&D on Scintillating crystals for the R3B Calorimeter Nuclear Science Symposium, Honolulu, 28th Oct. 3rd Nov. 2007

R&D on scintillating crystals for the R 3B Calorimeter

H. Alvarez Pol, J. Benlliure, E. Casarejos, D. Cortina, I. Durán, M. Gascón

GENP, Dpto. Física de Partículas, Universidade de Santiago de Compostela

Index:✔ FAIR and the R3B experimental setup✔ A Calorimeter for R3B: CALIFA✔ Crystal tests ✔ Realistic prototypes✔ Conclusions


About FAIR, the SuperFRS and R3B

FAIR Accelerator Facility (Facility for Antiproton and Ion Research) next to GSI @ Darmstadt, Germany✔ New superconducting synchroton double ring (SIS 100/300, 1100 m circunference, magnetic rigidities 100/300 Tm)✔ Ion beams with highest beam intensity and higher energies✔ Experimental programs include Nuclear Structure and Matter, Plasma Physics, Atomic Physics, Antiproton research, ...✔ SuperFRS separates inflight rare isotopes with extraordinary phasespace acceptance, from projectile fragmentation or fission

http://www.gsi.de/fair/index_e.html

http://www.gsi.de/forschung/kp/kp2/collaborations/R3B

R3B (Reactions with Radiactive Relativistic Beams):✔ Beam, proton and fragment ToF & tracking detectors✔ Calorimeter / gamma spectrometer ✔ Silicon arrays around target for recoils✔ Large acceptance superconducting dipole ✔ High resolution neutron detectors✔ Challenging research program including knockout, astrophysical interest reactions, QFS, fission, ...


The R3B Calorimeter: CALIFA

The Calorimeter requirements (R3B LoI, 2005) comprise:✔ A total absorption efficiency of about 80% up to E = 15MeV Lab✔ A gamma energy resolution of E

CoM/E

CoM ~ 3% (FWHM)

✔ A proton energy resolution better than 1% (FWHM) up to 300 MeV✔ A gamma multiplicity: (N)/<N> < 10%✔ A gamma sum energy: (E

sum)/<E

sum> < 10%

✔ Reasonable cost!

But note the particular kinematics due to the relativistic incoming beams:✔ The Lorentz boost shifts the gammas energy up to x3 in forward direction (at 700 MeV /n, and even more at larger energies) ✔ The gamma CoM energy reconstrucion depends strongly on geometry, in particular on the polar angle resolution ()✔ A large granularity [ (), variable with ] is requested!✔ An enhanced forward emission, peaked around 30 degrees (~0.82)

E(emitter) = 700 MeV/n [= 0.82]

...then, the R3B Calorimeter should feature:✔ A sufficient granularity in for a reasonable gamma CoM energy reconstruction; a granularity for a suitable crystal shape ✔ An adapted crystal lengths at different polar angles✔ A compact size, no gaps to increase the efficiency, no escape lines from target without crossing active detector ✔ A small number of different crystal types, with optimal design


The R3B Calorimeter CALIFA: technical design

Strong points in the crystals and calorimeter design:✔ A granularity ensuring a low geometrical contribution to E

CoM/E

CoM (< 3%)

✔ Only five different shapes of crystals for the full Barrel region✔ The shape minimizes space between crystals and escape lines from target✔ Features a variable length with polar angle for an improved efficiency✔ Terminated for the Hamamatsu onpurpose made LAAPD (10x20 mm2)✔ Assymetric, triedrum corner for simplified construction and measurements✔ About 3000 crystals, close to 1 Tm of CsI(Tl) only in the Barrel✔ Design (v5.0, Barrel region) completed, prototypes under construction


Test on CsI(Tl) crystals. Experimental setupExperimental setup, highlights:✔ CsI(Tl) is a reasonable and relatively cheap option✔ Hamamatsu APDs QE matches CsI(Tl) emission wavelength

Experimental setup for the presented (next) results:✔ CsI(Tl) crystals from St. Gobain (France) ✔ Hamamatsu LAAPD S86641010 and S866455✔ Camberra 2001A preamp + Ortec 572 Amplifier, other elec. chains tested (Ortec142 + Canberra 2022, Cremat CR110,...)✔ A black grounded Faraday box, with humidity control and temperature monitorization (0.1C resolution)✔ Other tests with API UV and different with Photonis PMs, different electronics and crystals from other providers...

Wavelength (nm) Wavelength (nm) LAAPD HAMAMATSU S8664-1010

Wavelength (nm)

CsI(Tl) emission wavelength

How do energy resolution behave with crystal length?

LAAPD Quantum efficiency and

Photosensibility


Test on CsI(Tl) + LAAPD: optimization

CsI(Tl) optimization tests on :✔ Wrapping ✔ Optical coupling✔ Amplifier shaping time and gain✔ LAAPD bias voltage✔ Temperature and voltage dependence tests (ongoing)

What is measured on the CsI(Tl) tests? ✔ Energy resolution✔ Crystal nonuniformity

137Cs (662 keV)


Test on CsI(Tl) crystals; energy resolution

Energy resolution Crystal sizeShapping time 1 cm 5 cm 10 cm

4 s 4.68 0.12 5.11 0.12 4.74 0.128 s 4.42 0.12 4.87 0.09 4.72 0.08


4 s 4.98 0.12 5.22 0.09 5.17 0.098 s 4.68 0.12 5.02 0.12 4.90 0.09


--

4 s 4.57 0.08 5.22 0.098 s 4.41 0.10 4.99 0.11

Best results for CsI(Tl) coupled to S86641010 Ham. APD

Mean results for CsI(Tl) coupled to S86641010 Ham. APD

Best results for CsI(Tl) coupled to SD6307073500 AP APD

Energy resolution tests conclusions:✔ Very good energy resolution, results comparable (or better) than those available in the literature✔ Low energy threshold, below 20 keV for most cases✔ Quite independent of the electronic chain✔ Energy resolution (%, FWHM) behaves nicely as √E

137Cs (662 keV)

Several radioisotopes


Test on CsI(Tl) crystals: non uniformity

Non uniformity tests:✔ Setup using 5 cm lead blocks, 5 cm apart from the crystal✔ In these figures, tests on 10 cm long crystal from St. Gobain ✔ G = (LO

maxLO

min)/LO

med between 3% and 17%

✔ Different values for crystals (sometimes shape), even from the same provider and requesting the same quality✔ Additional test required for the prototypes (realistic crystal size)✔ Non homogeneity specification essential to the company contracts. Impact on crystal price!

G = 16.7%

G = 9.6%


Prototype construction

Crystals from different providers have been obtained, ready for the tests:✔ IMP Lanzou, China✔ Hilger Crystals Ltd., England✔ St. Gobain Crystals Inc., France✔ Scionix, Netherlands

LAAPD development (Hamamatsu) based on S86641010 series:✔ First phase: double S86641010 sensor on a circuit, gap < 2 mm between sensors✔ Second phase: single 10x20 mm2 sensor on ceramic mounting✔ Ready 5 units (first phase) for immediate tests at TUDarmstadt (tagged gammas up to 20 MeV, very good resolution), Madrid and Upssala (protons)


Conclusions

... in short:✔ CsI(Tl) with LAAPD is well suited for our application✔ The energy resolution fulfills requirements, even for larger crystals✔ The crystals nonuniformity seems to be a very important point✔ Fullequiped prototypes are ready for test in gamma and proton beams

More information available:

http://www.usc.es/genp/r3b


The R3B Collaboration

Around 200 scientists from more that 50 institutions in 18 countries:

r&d on scintillating crystals for the r b...

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