jrjc 2009 30/11/09 barbara sulignano jrjc 2009 cea saclay key questions how do protons and neutrons...
TRANSCRIPT
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Key questionsKey questions
How do protons and neutrons make stable nuclei and rare isotopes?
How many neutrons can a nucleus hold?
What are the heaviest nuclei that can exist?
How do protons and neutrons make stable nuclei and rare isotopes?
How many neutrons can a nucleus hold?
What are the heaviest nuclei that can exist?
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1934 – Liquide drop model (Bethe, Von 1934 – Liquide drop model (Bethe, Von Weizsäcker):Weizsäcker):
Nuclear fissionNuclear fission
1949 – Shell model (Maria Goeppert-1949 – Shell model (Maria Goeppert-Mayer, Mayer,
Hans Jensen)Hans Jensen)Magic NumbersMagic Numbers
1960 - …Microscopic Models1960 - …Microscopic Models
EHFB = Emacro + Eshell + EpairingEHFB = Emacro + Eshell + Epairing
1934 – Liquide drop model (Bethe, Von 1934 – Liquide drop model (Bethe, Von Weizsäcker):Weizsäcker):
Nuclear fissionNuclear fission
1949 – Shell model (Maria Goeppert-1949 – Shell model (Maria Goeppert-Mayer, Mayer,
Hans Jensen)Hans Jensen)Magic NumbersMagic Numbers
1960 - …Microscopic Models1960 - …Microscopic Models
EHFB = Emacro + Eshell + EpairingEHFB = Emacro + Eshell + Epairingstable nucleistable nuclei
known nucleiknown nuclei
terra incognitaterra incognita
N=Z
pro
ton
s
neutrons
50
82
50
28
28
82
2082
28
20
126
The Nuclear LandscapeThe Nuclear Landscape
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Evidence for shell structureEvidence for shell structureEven-even nuclei: 2+
1 state energy as an indicator of shell structure
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Magicity is a
fragile concept
Near stabilityNear stability N>>ZN>>Z
Nuclear shell structureNuclear shell structureIs nuclear shell strucuture modified away from the line of stability?
As we add neutrons, traditional shell closures are changed, and may
even disappear!
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N=28 is not a good shell closure anymore
Experimental proof of disappearing of shell gap for neutron rich nuclei
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protons
neutrons
82
5028
28
50
82
2082
28
20
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stable double-magic nuclei4He, 16O, 40Ca, 48Ca, 208Pb
radioactive: 56Ni, 132Sn, magic ? 48Ni, 78Ni, 100Sn
70Ca ?48Ca
40Ca42Si32Mg
?4040
Shell structure of atomic nucleiShell structure of atomic nuclei
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Tools we have to investigate shell Tools we have to investigate shell structurestructure
• Evidence for nuclear shell structure from :
– Nuclear masses.
– Spectroscopy of excited states
– Reaction cross sections Corinne’s Talk
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Masses can be measured in different way:
• Time of flight
• Storage ring
• Penning trap Mass measurement via determination ofCyclotron frequency:
fc=qB/2п mFrom characteristic motion of stored ions
Masses measurementMasses measurement
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SpectroscopySpectroscopy
Particle detector
TargetBeam
γ
Reacted beam
stable beam and target
Fusion evaporationCoulomb excitationsOne and two nucleon knockoutCoulomb break upCharge exchange reactions
Only access to stable or neutron deficient nuclei
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Spectroscopy
Particle detector
TargetBeam
γ
Reacted beam
radioactive beam:
Coulomb excitationsOne and two nucleon knockoutCoulomb break upCharge exchenge reactions
Access to neutron rich nuclei
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• Projectile Fragmentation
•Isol technique
How to produce radioactive beamHow to produce radioactive beam
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Key questionsKey questions
How do protons and neutrons make stable nuclei and rare isotopes?
What are the heaviest nuclei that can exist?
How do protons and neutrons make stable nuclei and rare isotopes?
What are the heaviest nuclei that can exist?
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Z = 100
island of stability
?
black: stable isotopered: +-unstable isotopeblue: --unstable isotope yellow: -instable isotopegreen: spontan fission
Pb (lead) and Bi (bismuth)
U (uranium) and Th (thorium)
What is the next magic nucleus beyond What is the next magic nucleus beyond 208208Pb? Pb?
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1934Enrico Fermi proposes to irradiate Uranium with neutrons in order to synthesise Even heavier elements
1938Otto Hahn andFritz Straßmanndiscover the neutron-inducednuclear fission
193960-inch-cyclotron group:Cooksey, Corson, Ernest O. LawrenceThornton, Backus, Salisbury,Luis Alvarez und Edwin McMillan
With Fermi’s method and the 60’’-cyclotron 7 Transurane could (Z=93-98) Be synthesised. By irradiation of actinides with light ions the elements up Z=106 could beProduced in Berkeley (CA, U.S.A.)and in Dubna (Rußland).
The linear acceleratorUNILAC and thevelocity filter SHIP at GSI allowed for the synthesis of elements with Z=107-112.
Synthesis of SHE via fusion of heavy target nuclei with light projectiles1952 1974
Neutron period1940 1952
1896Discovery of radioactivity by A.H. Becquerel
Radioactivity period1896 1940
Synthesis of SHE via fusion (Pb and Bi as target nuclei)1974 1996
1899Actinium (Z=89) 1908
Radon (Z=86) 1939Francium (Z=87)
1917Protactinium (Z=91)
1952Einsteinium (Z=99)Fermium (Z=100)
1940Astatin (Z=85)Neptunium (Z=93)
1944Americium (Z=95)Curium (Z=96)
1941Plutonium (Z=94)
1950Californium (Z=98)
1949Berkelium (Z=97)
1996Copernicium(Z=112)
1994Darmstadium(Z=110) Rontgenium(Z=111)
1982Meitnerium (Z=109)
1981Bohrium (Z=107) 1984
Hassium (Z=108)
1969Rutherfordium (Z=104)
1965Nobelium (Z=102)Lawrencium (Z=103)
1974Seaborgium (Z=106)
1970Dubnium (Z=105)
1955Mendelevium (Z=101)
1898 Polonium (Z=84) Radium (Z=88)
History of the synthesis and History of the synthesis and discovery of super heavy elementsdiscovery of super heavy elements
Synthesis of SHE via fusion (48Ca beam and actinide targets)1999 2005
2005Element 118
2000 Element 1161999
Element 114 2003Element 113 element 115
Dubna
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How to produce super heavy elementsHow to produce super heavy elements
Neutron capture up to Z=100
reactors
bomb
in stars?
ee--
αα
αα
DésexcitationDésexcitation
Chaîne de Chaîne de DésintégrationDésintégration
T ~10T ~10-15-15ss
T >10T >10-6-6ss
Elément Elément superlourdsuperlourd
ee--
nn nnFusionFusion
CompétitionCompétition- fission- fission- évaporation- évaporation
Noyau Noyau composécomposé
T ~10T ~10-20/-17-20/-17ss
Fusion evaporation
Cold fusion X+ 208Pb, 209Bi
Hot fusion 48Ca+X
See Fabien’s talk
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Status of SHE researchCold fusion (GSI, RIKEN) based on Pb and Bi targets
Cold fusion (GSI, RIKEN) based on Pb and Bi targets
1second
1 minute
1 hour
1 day
10 days
GSIRIKEN
1 pb
Hot fusion (JINR) based on actinide targets
Hot fusion (JINR) based on actinide targets
DUBNA
1 pb35fb3 events250days
2pb6 events (Dubna)44days
Needs for- Higher Z- More events for studies
Beam:High intensity beamSpectrometer:High rejection powerWide angular acceptanceGood mass resolution
Needs for- Higher Z- More events for studies
Beam:High intensity beamSpectrometer:High rejection powerWide angular acceptanceGood mass resolution
Proton
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Reaction synthesisReaction synthesis
DAVID’s talk