Mass Asymmetric Fission of Iridium Nucleus Mass Asymmetric

Mass Asymmetric Fission of Iridium Nucleus Mass Asymmetric Fission of Nucleus Produced in 7 Li + 186 W Katsuhisa Nishio Advanced Science Research Center Japan Atomic Energy Agency Tokai, JAPAN ARIS 2014 Tokyo

① ④ ② ⑤ ③ ⑥ ① K. Nishio, K. Hirose, I. Nishinaka, H. Makii, R. Orlandi, R. Léguillon, J. Smallcombe, S. Mitsuoka, T. Ishii, H. Ikezoe ② A. Andreyev ③ N. Tamura, S. Goto ④ T. Ohtsuki ⑤ I. Tsekhanovich ⑥ P. Möller

Properties for Low-Energy Fission Region of our interest I: betadelayed fission of A~180 -200 N/Z~1. 22 -1. 3: Tl, Bi, At, Fr ISOLDE(CERN) A. Andreyev et al. , Phys. Rev. Lett. 105, 252502 (2010). Z=82 180 Hg - particle induced N/Z=1. 25 187 Ir 196 Au x - e. m. –induced E*~11 Me. V

Calculated Fission Fragment Yield 180 Hg Calculated by P. Möller (LANL) and J. Randrup (LBNL) 193 Ir 7 Li + 186 W 193 Ir* P. Möller, 10 th ASRC International Workshop, “ Nuclear Fission and Structure of Exotic Nuclei ”, 2013. March, Tokai, Japan

JAEA at Tokai and Tandem Facility Tokai Campus, JAEA 20 MV Tandem accelerator (20 UR) J-PARC Tandem facility Tokyo

Time difference signal of FFs in 7 Li + 186 W MWPC 1 7 Li Beam 44 o 186 W Fragment 2 MWPC 2 40. 0 Me. V Counts Fragment 1 Ec. m. = 65. 5 Me. V 30. 0 Me. V Time difference (ch)

Fragment Mass Distributions in 7 Li + 186 W Elab 68. 0 Me. V Fusion reaction is assumed + 186 W 193 Ir* 41. 5 Me. V Events (u) 7 Li 31. 1 Me. V 83 As N = 50 110 Ru N = 66 Fragment Mass (u)

Folding Angle between Fission Fragments Elab = 31. 1 Me. V Complete Fusion 7 Li + 186 W θfold =169 o FF 1 θ 1 FF 2 θ 2 Counts Beam Recoiled Fissioning Nucleus θfold = θ 1 + θ 2 (deg)

Analysis assuming fusion-fission 7 Li + 192 Os 199 Au* 7 Li θfold, =167. 9 o + 186 W 193 Ir* θfold =167. 5 o Ebeam = 41. 5 Me. V Fragment Mass (u) <TKEViola> =134 Me. V Folding Angle (deg. ) TKE (Me. V) Folding Angle (deg. ) Z=118 Fragment Mass (u) Viola Formula from Phys. Rev. C 31, 1550 (1985) <TKEViola> =129 Me. V

7 Li + 186 W, 192 Os + 186 W 7 Li 180 EBeam = 64. 0 Me. V 180 σfiss 170 = 67 μb qfold (deg) 160 41. 5 Me. V + 192 Os 170 180 170 160 14 μb 110 μb 160 2. 1 μb -20 0 180 31. 1 Me. V 170 0. 8 μb 160 -20 0 20 d. T (ns) 20

Break-up Fusion 7 Li 3 H + 4 He (Q= -2. 467 Me. V) 187 Ir 188 Ir 189 Ir 190 Ir 191 Ir 192 Ir 193 Ir Counts p + 192 Os 186 Os 187 Os 188 Os 189 Os 190 Os 191 Os 192 Os 185 Re 186 Re 187 Re 188 Re 189 Re 184 W 185 W 186 W Fragment Mass (u) 186 W( 7 Li, t)190 Os* 186 W( 7 Li, α)189 Re *

Break-up Fusion and Fission 3 H 3 H 7 Li 4 He 186 W 4 He + 186 W 190 Os* 3 H + 186 W 189 Re* Fragment 2 Fragment 1 CN VCoul Ebeam, thres (7 Li) 4 He + 186 W 190 Os* 20. 3 Me. V 36 Me. V 3 H + 186 W 189 Re* 10. 3 Me. V 24 Me. V

Fission Barrier Height for 189 Re and 190 Os 189 Re, 190 Os Fission Barrier is 25 Me. V 189 Re* or 190 Os* should have excitation energy larger than 25 Me. V P. Möller, 16 th ASRC International Workshop, “ Nuclear Fission and Decay of Exotic Nuclei ”, 2014. March, Tokai, Japan

Folding Angle at E* = 25 Me. V of Fissioning Nucleus 7 Li 180 Elab 186 W(7 Li, α) 189 Re*, θα = 25 o 186 W(7 Li, t) 190 Os* , θt = 45 o 170 64. 0 Me. V + 186 W = 193 Ir* 41. 5 Me. V qfold (deg) 160 186 W(7 Li, α) 189 Re*, θα = 45 o 186 W(7 Li, t) 190 Os* , θ = 45 o t 170 160 180 31. 1 Me. V 186 W(7 Li, 170 α) 189 Re*, θα = 55 o E*max = 36 Me. V 160 -20 0 20 d. T (ns)

Setup for Break-up Fusion Induced Fission MWPC 1 Target 7 Li Beam 189 Re*… 186 W θLAB t, α MWPC 2 ΔE-E 7 Li ΔE E

Summary Mass-asymmetric fission was observed for nucleus produced in 7 Li +186 W. The fissionig nucleus could be populated by break-up fusion. Coincidence experiment between particle and both fission fragments is planned.

Properties for Low-Energy Fission 180 Hg A. Andreyev et al. , Phys. Rev. Lett. 105, 252502 (2010).

Folding Angle Distribution at E* = 25 Me. V 180 Elab 7 Li 170 64. 0 Me. V 186 W(7 Li, 41. 5 Me. V qfold (deg) 160 180 t) 190 Os* , θt = 45 o, 170. 0 α) 189 Re*, θα = 25 o, 173 186 W(7 Li, t) 190 Os* , θt = 45 o, 170. 0 o 186 W(7 Li, α) 189 Re*, θ = 45 o , 172 α 170 160 E* max = 26 Me. V 180 31. 1 Me. V + 186 W = 193 Ir* 186 W(7 Li, t) 190 Os* , θt = 45 o, 170. 0 186 W(7 Li, α) 189 Re*, θ = 55 o, 172 α 170 160 -20 0 20 d. T (ns) E*max = 36 Me. V

Summary

21

22

23

Multi-nucleon Transfer Induced Fission 18 O + 232 Th F O 15 N Be B Esum (Me. V) N C Coincidence between particle and fission fragments 232 Th(18 O, 15 N) 235 Pa* Transfer of 3 H

Fragment Mass Distributions for 3 H Transfer → Fission Counts Excitation energy (Me. V) 232 Th(18 O, 15 N) 235 Pa* Fragment mass yield (u)

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

Multi-nucleoon Transfer Induced Fission 18 O + 232 Th Coincidence between particle and fission fragments F O N Be B Esum (Me. V) C

New Region for Mass Asymmetric Fission 180 Hg 100 80 A. Andreyev et al. , Phys. Rev. Lett. 105, 252502 (2010). T. Ichikawa et al. , Phys. Rev. C. 86, 024610 (2012). 28

Theoretical Mass Yield 189 Ir 193 Ir

Q-value for Fission (Me. V) Fission Ｑ-value 1980 Large Fission Saddle Point Shape Probability 258 Fm 238 U 2010 193 Ir Present Small Fission Probability Fragment Mass (u) 160 Gd