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Reactions with exotic nucleiReactions with exotic nuclei( ( at FLNRat FLNR ) )
• Recent experiments on fusion of Recent experiments on fusion of 66HeHe
• Deep sub-barrier fusion of neutron rich nucleiDeep sub-barrier fusion of neutron rich nuclei
• A few words about astrophysicsA few words about astrophysics
DIRECT
10m
0
R IB
400-cm cyclotron
400-cm cyclotronradioactive ion beams
low energy beam line
7Li
DubnaRadioactive IonBeams
6He
Electronaccelerator
ISOL
Acculinna
DIRECT
Fusion, transfer and breakup reaction mechanisms induced by halo nucleus Fusion, transfer and breakup reaction mechanisms induced by halo nucleus 66HeHeJINR (Dubna), CSNSM (Orsay), IRS (Strasbourg), ULB (Bruxelles), Vanderbilt Univ. (USA)
6He + 166Er 172Yb* 166Yb + 6n
6He + 166Er 170Yb* + 2n
6He + 166Er 168Er* + 4He
166Er(6He,6n)166Yb & 165Ho(6Li,5n)166Yb <==> 166Er(4He,4n)166Yb //PRC48(1993)319//3 2 1
DRIBsDec.- January ’07U400
6He + 166Er → 172Yb* → 166Yb + 6n → 167Yb + 5n → 170Yb*+2n → 168Yb + 4n → 168Er* + α → 168Er
Complete & incomplete fusion reactions with 6He (Complete & incomplete fusion reactions with 6He (E=62 MeVE=62 MeV))
Data analysis using EMPIRE-II code http://www.nndc.bnl.gov/nndcscr/model-codes/empire-ii/
The statistical model used in the EMPIRE-II is an advanced implementation of the Hauser-Feshbach theory. The exact angular momentum and parity coupling is observed. The emission of neutrons, protons alpha-particles and light ion is taken into account along with the competing fission channel. The full gamma-cascade in the residual nuclei is considered.
4n5n 6n
6n
5n4n
B(6He+Er) = 16 MeV, B(6Li+Ho) = 26 MeV
EMPIER-II calculation of EMPIER-II calculation of xnxn and and fusfus
At well-above barrier energies there is no difference between 6He and 6Li from the point of view of the fusion probability.
Other reaction channels are still under analysis.
Sub-barrier fusion of Sub-barrier fusion of 66HeHe
M.S. Hussein, M.P. Pato, L.F. Canto and R. Donangelo, Phys.Rev. C 46, 377 (1992).L. F. Canto, R. Donangelo, P. Lotti and M.S. Hussein, Phys.Rev. C 52, R2848 (1995).N. Takigawa and H. Sagawa, Phys.Lett. B 265, 23 (1991).C.H. Dasso and A. Vitturi, Phys.Rev. C 50, R12 (1994).K. Hagino, A. Vitturi, C.H. Dasso and S.M. Lenzi, Phys.Rev. C 61, 037602 (2000).A.S. Fomichev et al., Z.Phys. A 351, 129 (1995).J.J. Kolata et al., Phys.Rev.Lett. 81, 4580 (1998).M. Trotta, J.L. Sida, N. Alamanos et al., Phys.Rev.Lett. 84, 2342 (2000).R. Raabe, J.L. Sida, J.L. Charvet et al., Nature 431, 823 (2004).A. Di Pietro et al., Phys. Rev. C 69, 044613 (2004).A. Navin et al., Phys. Rev. C 70, 044601 (2004).C. Beck, N. Keeley, and A. Diaz-Torres, Phys. Rev. C 75, 054605 (2007).…
Neutron excess itself does not play an important roleNeutron excess itself does not play an important role
Neutron transfer with positive Q-value is important !Neutron transfer with positive Q-value is important !
Sub-barrier fusion enhancement due to neutron transferSub-barrier fusion enhancement due to neutron transfer( sequential fusion, “energy lift” )( sequential fusion, “energy lift” )
Wave functions of valence neutrons spread over both nuclei before they reach and overcome the Coulomb barrier
Time dependent Time dependent Schrödinger equationSchrödinger equation
( Zagrebaev, Samarin & Greiner, PRC 2006)
Proposed experimentsProposed experiments
First experimentFirst experiment
MSP-144
Focal plane
Ionizationchamber
Reactionchamber
Si-detectors
Strip-detector
Au-targets
Monitors
Monitor
SETUP FOR ACTIVATION MEASUREMENTS with MSP-144
dE/dx~40keV/mm
target~20mm
E ~ 0.4MeV
Huge enhancement Huge enhancement in deep sub-barrier fusion of weakly bound nucleiin deep sub-barrier fusion of weakly bound nuclei
Fusion of light neutron rich and stable nucleiFusion of light neutron rich and stable nuclei
Light neutron rich nuclei in astrophysical nucleosynthesis ?Light neutron rich nuclei in astrophysical nucleosynthesis ?
in particular,in particular,
instead of the bottle-neck three-body reaction
4He + 4He (→8Be, 10-16s ) + 4He → 12C,
4He + 6He(1s) → 9Be + n probably may occur.
Fusion of light neutron rich nuclei produced in the r-process Fusion of light neutron rich nuclei produced in the r-process may significantly change the nucleosynthesis scenario ?may significantly change the nucleosynthesis scenario ?
Experiments which could be performedExperiments which could be performed
• 11HH((66He,nHe,nγγ))66LiLi
• 33HeHe((66He,2nHe,2nγγ))77BeBe
• 66LiLi((66He,nHe,nγγ))1111BB
• 99BeBe((66He,2nHe,2nγγ))1313CC
• 1010BB((66He,2nHe,2nγγ))1414NN
• 1212CC((66He,2nHe,2nγγ))1616OO
• 1414NN((66He,2nHe,2nγγ))1818FF
• ……
• 11HH((99Li,nLi,nγγ))99BeBe
• 33HeHe((99Li,2nLi,2nγγ))1010BB
• 66LiLi((99Li,2nLi,2nγγ))1313CC
• 99BeBe((99Li,2nLi,2nγγ))1616NN
• 1010BB((99Li,3nLi,3nγγ))1616OO
• 1212CC((99Li,2nLi,2nγγ))1919FF
• 1414NN((99Li,2nLi,2nγγ))2121NeNe
• ……
Reactions withReactions with 66HeHeReaction Barrier Energy (c.m.)
lab.Q (MeV) Reaction channels Gamma-lines
6He + p → 7Li 0.4 (0.2 – 0.5)1.4 – 3.5
+10 1H ( 6He, 7Li γ)1H ( 6He, 6Li n γ)
6Li: 3.6, 0+ 2.2, 3+
g.s., 1+
6He + 3He → 9Be 0.8 (0.4 – 1.2)1.2 – 3.6
+21 3He ( 6He, 8Be n γ)3He ( 6He, 7Be 2n γ)
6He + 6Li → 12B 1.0 (0.5 – 1.5)1.0 – 3.0
+18 6Li ( 6He, 11B n γ)6Li ( 6He, 10B 2n γ)
10B: 2.2, 1+ 1.7, 0+ 0.7, 1+
g.s., 3+
6He + 9Be → 15C 1.3 (0.6 – 1.6)1.0 – 2.7
+19 9Be ( 6He, 14C n γ)9Be ( 6He, 13C 2n γ)
6He + 10B → 16N 1.6 (0.8 – 2.4)1.3 – 3.8
+24 10B ( 6He, 15N n γ)10B ( 6He, 14N 2n γ)
6He + 12C → 18O 1.9 (1.0 – 3.0)1.5 – 4.5
+18.4 12C ( 6He, 17O n γ)12C ( 6He, 16O 2n γ)
16O: 6.9, 2+ 6.1, 3- 6.0, 0+ g.s., 0+
6He + 14N → 20F 2.2 (1.1 – 3.1)1.6 – 4.5
+20.5 14N ( 6He, 19F n γ)14N ( 6He, 18F 2n γ)
6He + 16O → 22Ne 2.5 (1.2 – 3.3)1.7 – 4.5
+20.9 16O ( 6He, 21Ne n γ)16O ( 6He, 20Ne 2n γ)
Reactions withReactions with с с 99LiLi
Reaction Barrier Energy (c.m.)lab.
Q (MeV) Reaction channels Gamma-lines
9Li + 3He → 12B 1.2 (0.5 – 1.2)2.0 – 4.8
+26.5 3He ( 9Li, 10B 2n γ) 10B: 2.2, 1+ 1.7, 0+ 0.7, 1+
g.s., 3+
9Li + 6Li → 15C 1.5 (0.7 – 1.5)1.7 – 3.7
+29.1 6Li ( 9Li, 13C 2n γ)6Li ( 9Li, 11Be + 4He)
13C: 3.9, 5/2+ 3.7, 3/2- 3.1, 1/2+ g.s., 1/2-
9Li + 10B → 19O 2.4 (1.1 – 2.4)2.1 – 4.7
+33.7 10B ( 9Li, 17O 2n γ)10B ( 9Li, 15C + 4He)
9Li + 14N → 23Ne 3.3 (1.5 – 3.3)2.5 – 5.5
+33.0 14N ( 9Li, 21Ne 2n γ)14N ( 9Li, 19O + 4He)
Standard scenario Standard scenario for nucleosynthesisfor nucleosynthesis
Уровни Уровни 77LiLi и и 99BeBe