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Katsuhisa NishioAdvanced Science Research CenterJapan Atomic Energy AgencyTokai, JAPANARIS2014 TokyoMass Asymmetric Fission of Iridium NucleusMass Asymmetric Fission of Nucleus Produced in 7Li + 186W

K. Nishio, K. Hirose, I. Nishinaka, H. Makii, R. Orlandi, R. Lguillon, J. Smallcombe, S. Mitsuoka, T. Ishii, H. Ikezoe A. Andreyev N. Tamura, S. GotoT. OhtsukiI.TsekhanovichP. Mller

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- particle induced x - e.m. induced E*~11 MeV

187Ir

196AuZ=82Z=82Z=82Z=82180Hg N/Z=1.25Region of our interest I: beta-delayed fission of A~180-200N/Z~1.22-1.3: Tl,Bi, At, FrISOLDE(CERN)Properties for Low-Energy Fission A. Andreyev et al., Phys. Rev. Lett.105, 252502 (2010).3Calculated Fission Fragment Yield

180Hg Calculated by P. Mller (LANL) and J. Randrup (LBNL)P. Mller, 10th ASRC International Workshop, Nuclear Fission and Structure of Exotic Nuclei , 2013.March, Tokai, Japan193Ir7Li + 186W 193Ir*4

JAEA at Tokai and Tandem Facility20 MV Tandem accelerator (20UR)

Tokai Campus, JAEATokyoTandem facilityJ-PARC

5Time difference signal of FFs in 7Li + 186W186WMWPC2MWPC1Fragment 2Fragment 17Li Beam

Time difference (ch)CountsEc.m.= 65.5MeV40.0 MeV30.0 MeV44oFragment Mass Distributions in 7Li + 186W

31.1 MeV68.0 MeV41.5 MeVElab Fragment Mass (u)110Ru83AsEvents (u)Fusion reaction is assumed

7Li + 186W 193Ir*N = 50N = 66 Folding Angle between Fission Fragments

fold = 1 + 2 (deg)Complete Fusion 7Li + 186W fold =169o Elab = 31.1 MeV BeamFF 1FF 21Recoiled Fissioning Nucleus2Counts8Analysis assuming fusion-fissionViola Formula from Phys. Rev. C 31, 1550 (1985)

7Li + 192Os 199Au* Fragment Mass (u)TKE (MeV) Folding Angle (deg.) =134 MeV fold, =167.9o

TKE (MeV) 7Li + 186W 193Ir* fold =167.5oFragment Mass (u) =129 MeV Folding Angle (deg.)Ebeam = 41.5 MeVZ=1189

7Li + 186W, 192Os

31.1 MeV41.5 MeVEBeam = 64.0 MeVqfold (deg)dT (ns)-20 0 20180

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1607Li + 186W7Li + 192Osfiss = 67 b110 b14 b2.1 b0.8 b-20 0 20dT (ns)192Os191OsBreak-up Fusion187Re188Re189Re188Os189Os190Os185W186Re187Os189Ir190Ir191Ir188Ir192Ir193Ir184W185Re186Os187Ir186W186W( 7Li, )189Re *186W( 7Li, t)190Os* 189Re193Ir

p + 192OsCountsFragment Mass (u)190Os7Li 3H + 4He (Q= -2.467 MeV) 11Break-up Fusion and FissionFragment 1Fragment 2186W7Li4He3H + 186W 189Re*4He3H4He + 186W 190Os*3HCNVCoulEbeam,thres (7Li)4He + 186W190Os*20.3 MeV 36 MeV3H + 186W189Re*10.3 MeV 24 MeV12Fission Barrier Height for 189Re and 190Os

P. Mller, 16th ASRC International Workshop, Nuclear Fission and Decay of Exotic Nuclei , 2014.March, Tokai, Japan

189Re* or 190Os* should have excitation energy larger than 25 MeV189Re, 190OsFission Barrier is 25 MeVdT (ns)Folding Angle at E* = 25 MeV of Fissioning Nucleus7Li + 186W = 193Ir*31.1 MeV41.5 MeVElab E*max = 36 MeV

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160-20 0 20qfold (deg)64.0 MeV

186W(7Li, ) 189Re*, = 45o 186W(7Li, t) 190Os* , t = 45o 186W(7Li, ) 189Re*, = 55o 186W(7Li, ) 189Re*, = 25o186W(7Li, t) 190Os* , t = 45o180

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EETarget7Li186WLABE-E t, 7Li BeamSetup for Break-up Fusion Induced Fission

189Re*MWPC1MWPC2SummaryMass-asymmetric fission was observed for nucleus produced in 7Li +186W.

The fissionig nucleus could be populated by break-up fusion.

Coincidence experiment between particle and both fission fragments is planned. 17Properties for Low-Energy Fission

180Hg A. Andreyev et al., Phys. Rev. Lett.105, 252502 (2010).18dT (ns)Folding Angle Distribution at E* = 25MeV186W(7Li, ) 189Re*, = 25o, 173 186W(7Li, ) 189Re*, = 45o , 172186W(7Li, ) 189Re*, = 55o, 172 186W(7Li, t) 190Os* , t = 45o, 170.0186W(7Li, t) 190Os* , t = 45o,170.0o 186W(7Li, t) 190Os* , t = 45o, 170.0 7Li + 186W = 193Ir*31.1 MeV41.5 MeVElab E*max = 36 MeVE* max = 26 MeV

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160-20 0 20qfold (deg)64.0 MeV

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Multi-nucleon Transfer Induced Fission

18O + 232Th Esum (MeV) Coincidence between particle and fission fragmentsOFNCBBe15N232Th(18O, 15N) 235Pa* Transfer of 3H

232Th(18O, 15N) 235Pa* FissionFragment Mass Distributions for 3H TransferFragment mass yield (u)Excitation energy (MeV)Counts

232Th(18O, 18O) 232Th*Fragment Mass Distributions for 232Th* 26Fragment mass yield (u)Excitation energy (MeV)

Multi-nucleoon Transfer Induced Fission

18O + 232Th Esum (MeV) Coincidence between particle and fission fragmentsOFNCBBeNew Region for Mass Asymmetric Fission

80100A.Andreyev et al., Phys. Rev. Lett.105, 252502 (2010).180Hg28

T. Ichikawa et al.,Phys. Rev.C.86, 024610 (2012).Theoretical Mass Yield

193Ir189Ir29Fission -valueFragment Mass (u)

2010Q-value for Fission (MeV)Present

258Fm

238U193Ir160GdSaddle Point Shape1980Large Fission ProbabilitySmall Fission Probability30