Katsuhisa - PowerPoint PPT Presentation

Fission Study using Multi-nucleon Transfer Reactions ( Surrogate Reactions ) 重イオン多核子移行反応による核分裂特性の研究 （代理反応） Katsuhisa Nishio Advanced Science Research Center Japan Atomic Energy Agency 西尾 勝久 日本原子力研究開発機構 先端基礎研究センター ND2018, 29-30 Nov., Tokyo Institute of Technology 1

Collaborators Japan Atomic Energy Agency (JAEA) K. Nishio, K. Hirose, H. Makii, R. Orlandi, K. Tsukada, M. Asai, A. Toyoshima, T.K.Sato, Y. Ito, Y. Nagame University of York, JAEA A.N. Andreyev China Institute of Atomic Energy S. Yan, C.J. Lin Kindai University Y. Aritomo, S. Tanaka, Y. Miyamoto, M. Okubayashi, S. Ishizaki Tokyo Institute of Technology K. Ratha, S. Chiba University of Bordeaux I. Tsekhanovich, B. Jurado Kyoto University T. Ohtsuki ORNL K. Rykaczewski, R.A. Boll

Tokai Campus, JAEA Tokyo 20UR J-PARC Tandem facility

Contents ☑ Multi-nucleon transfer (MNT) reactions and fission ☑ Experimental setup ☑ Experimental results and discussions ☑ Fission experiments using 254 Es ☑ Summary 4

Nuclear Structure and Fission Liquid drop model Including shell energy correction Ground state shape Ground state shape 240 U 1 st Saddle point Fission isomer 2 nd Saddle point Saddle Point scission scission Highly excitation energy Low excitation energy Fission fragment mass distributions is one of the important observable 5 to know the structure of deformed nucleus.

Measured Fragment Mass/Charge Yield ~1995 Data for low-energy fissions, Excitation energy ≦ B f +10MeV A.N. Andreyev, K. Nishio, K.-H. Schmidt, Reports on Progress in Physics, 81 , 016301(2018 )

Measured Fission-Fragment Mass/Charge Yields ~2017 R. Léguillon et al ., Phys. Lett. B 761 , 125 (2016) K. Hirose et al. Phys. Rev. Letters, 119 , 222501 (2017) A.N. Andreyev, K. Nishio, K.-H. Schmidt, Reports on Progress in Physics, 81 , 016301(2018 )

Multi-nucleon transfer reactions and fission ② 原子核構造（理論） In the multi-nucleon transfer (MNT) reactions: (1) We can generate many nuclei depending on transfer channels. (2) Excitation energy of compound nucleus distributes widely. Silicon ΔE -E Fission fragment detector 16 O... 18 O 18 O n 240 U * … 238 U Liquid Scintillator 238 U n (47 detetors ) Energy Fission Barrier (1) Fission probability and Fission barrier height. (2) Fission fragment mass distributions. (3) Fission fragment angular distributions. (4) Prompt neutrons accompanied by fission. Measured and Planned experiments using 18 O beam and targets of 8 232 Th, 238 U, 248 Cm, 237 Np, 249 Cf, 243 Am, 249 Bk, 254 Es

Experimental Setup E (300 μ m) D E (75 μ m) 16 strips 12 detectors recoil Silicon ΔE -E DE θ φ Multi-wire proportional Counter

Targets and Detectors MWPC Target ( 248 Cm) Silicon ΔE -E detector ~ 30 - 60 μ g/cm 2 ΔE = 75 μ m Position Sensitive ~ ø 2.0 mm Thickness fluctuation < 1 μ m. 200 x 200 mm 2

Particle Identification using ΔE– E Telescope 18 O + 248 Cm (E beam = 162MeV) F 18 O (  248 Cm*) 17 O (  249 Cm*) O 16 O (  250 Cm*) Elastic Scattering N D E (MeV) 15 N (  251 Bk*) C 14 N (  252 Bk*) B Be 14 C (  252 Cf*) Li 13 C (  253 Cf*) α 12 C (  254 Cf*) E res (MeV)

Fission Probability and Fission Barrier Height 238 U( 18 O, 16 O) 240 U* 0 5 10 15 20 25 n 0.3 of Compound Nucleus 3rd Fission Probability 2nd n B f 0.2 3rd 2nd Potential 0.1 1st 0 5 10 15 20 25 Excitation energy (MeV) exp = 5.5 MeV B f Deformation cal = 6.38 MeV (P. M ӧ ller ） B f Fission after neutron evaporation is called “Multi - chance fissions”

Fission Barrier Height from MNT reactions Fission Probability Fission Probability 238 U( 18 O, 16 N) 240 Np* 238 U( 18 O, 17 N) 239 Np* B f (cal) =5.57 MeV 6.01 MeV P. M ӧ ller et al., PRC 79, 064304 (2009) Excitation energy (MeV) Excitation energy (MeV) B.N. Lu et al., Fission Probability Fission Probability PRC 89, 014323 (2014) 5.98 MeV 5.92 MeV 6.35 MeV 238 U( 18 O, 16 C) 240 Pu* 238 U( 18 O, 15 C) 241 Pu* Excitation energy (MeV) Excitation energy (MeV) Poster Presentation by Kean Kun Ratha (PA13)

Extending the Fission Barrier D ａｔａ using MNT Reactions 152 162 152 162 184 184 Theory (KUYT) 12 12 12 12 Cm (Z=96) Cm (Z=96) Md (Z=101) 10 10 Md (Z=101) 10 10 Theory (ETFSI) 8 8 8 8 6 6 6 6 Theory (M ӧ ller) Fission Barrier Height (MeV) 4 4 4 4 2 2 2 2 12 12 12 12 ● Available Data (33) 10 Am (Z=95) 10 0.2 MeV 10 Am (Z=95) 10 0.2 MeV Fm (Z=100) Fm (Z=100) 8 8 8 8 RIPL-2, RMP (Bjornholm) 6 6 6 6 4 4 4 4 2 2 ◇ 2 2 JAEA MNT Setup 20 12 20 12 10 10 Es (Z=99) 16 Es (Z=99) 16 Pu (Z=94) Pu (Z=94) 〇 Planned at JAEA 8 8 12 12 6 6 8 8 4 4 4 4 2 2 We plan to obtain 34 new 20 12 20 12 Cf (Z=98) 10 Cf (Z=98) 10 16 16 fission barrier data using the Np (Z=93) Np (Z=93) 8 8 12 12 6 6 reaction of 8 8 4 4 4 4 2 2 237 Np, 244 Pu, 20 12 20 12 10 U (Z=92) 10 Bk (Z=97) 16 U (Z=92) Bk (Z=97) 16 18 O + 241,243 Am, 248 Cm, 8 8 12 12 6 6 8 8 249 Bk, 249 Cf, 254 Es 4 4 4 4 2 2 0 0 130 140 150 160 170 180 190 130 140 150 160 170 180 190 130 140 150 160 170 180 190 130 140 150 160 170 180 190 Neutron Number

Fission Events registered on the Excitation Energy of Compound Nucleus and Fragment Mass 60 237 Np( 18 O, 19 O) 236 Np * 50 Excitation Energy (MeV) Fission fragment mass distributions 40 34.2 MeV 30 22.3 MeV 17.8 MeV 20 16.3 MeV 14.3 MeV 10 12.8 MeV B f = 6.3 MeV 0 60 80 100 120 140 160 180 Fragment Mass (u)

Benchmark of Fission Fragment Mass Distribution (FFMDs) Excitation Energy E * =33.70-35.70 5 4 33.7-35.7 MeV 237 Np ( 18 O, 19 O) 236 Np * 3 2  1 0 E * =21.75-23.75 5 21.8-23.8 MeV Present Data 4 3 2 1 0 E * =17.3-18.3 17.3-18.3 MeV 5 Yield (%) 4 3 p + 235 U = 236 Np* 2  1 0 E * =15.8-16.8 5 15.8-16.8 MeV Mulgin (2009) 4 3 Yield (%) 2 1 Ferguson (1973) 0 E * =13.8-14.8 13.8-14.8 MeV 5 4 3 2 1 0 E * =12.3-13.3 12.3-13.3 MeV Good agreement with the literature data is found. 5 4 3 2 1 0 60 80 100 120 140 160 180 Fragment Mass (u) Fragment Mass (u)

Fission Fragment Mass Distributions (FFMDs) obtained in 18 O + 237 Np 240-243 Am 242-245 Cm 244-246 Bk 246-249 Cf 236-239 Np 238-241 Pu Excitation Energy (MeV) 236 Np 237 Np 238 Np 239 Np 238 Pu 240 Pu 241 Pu 240 Am 241 Am 242 Am 242 Cm 243 Cm 244 Cm 245 Cm 244 Bk 246 Bk 246 Cf 247 Cf 248 Cf 239 Pu 243 Am 245 Bk 247 Bk 249 Cf 6 6 6 60-70 4 4 2 2 0 0 6 6 5 50-60 4 4 2 2 0 0 6 6 4 40-50 4 4 2 2 Yield (%) 0 0 3 6 6 30-40 4 4 2 2 0 0 2 6 6 20-30 4 4 2 2 0 0 6 1 6 10-20 4 4 2 2 0 0 6 6 5-10 4 4 2 2 0 0 100 200 100 200 100 200 100 200 100 200 100 200 100 200 100 200 100 200 100 200 100 200 100 200 100 200 100 200 100 200 100 200 100 200 100 200 100 200 100 200 100 200 100 200 100 200 100 20 Fragment Mass (u) Fission data for 23 nuclides are obtained in the single experiment.

Average Masses of Heavy （ H ） and Light （ L ） Fragments Excitation Energy Range = 10 - 20 MeV 18 O + 238 U 18 O + 232 Th 18 O + 248 Cm

Effects of Compound Nucleus Neutron-emission on FFMDs Role of Multi-chance Fission on FFMDs 240 U (E * = 45 MeV) Langevin Calculation 1 st chance 2 nd 3 rd 4 th Poster Presentation by Shoya Tanaka (PA10)

Experimental Data in Comparison with Langevin Calculation                      Excitation Energy 234,235,236,237,238,239,240 U 236,237,238,239,240,241,242 Np 238,239,240,241,242,243,244 Pu (MeV) 0 0 0 5 5 5 N=146 40-50 0 0 0 5 5 5 30-40 Yield (%) 0 0 0 5 5 5 20-30 0 0 0 5 5 5 10-20 0 0 0 80 160 80 160 80 160 80 160 80 160 80 160 80 160 80 160 80 160 80 160 80 160 80 160 80 160 80 160 80 160 80 160 80 160 80 160 80 160 80 160 80 160 Fragment mass (u) Fragment mass (u) Fragment mass (u) Fragment Mass (u) Data from 18 O+ 232 Th and 18 O + 238 U Without multi-chance fission With multi-chance fission Langevin calculation by S. Tanaka, Kindai Univ. Experimental data Y. Aritomo and S. Chiba, Phys. Rev. C 88 , 044614 (2013).

ҧ Neutron Multiplicity at the Excitation Energy corresponding to Effects of Compound Nucleus Neutron-emission on FFMDs Thermal Neutron-induced Fissions Pu Np Am 𝜉 ● This work □ JENDL-4.0 Mass number of Fissioning Nucleus

Toward Understanding the Spins of Compound Nucleus (1) Fission Probability Fission probability changes with the spins of compound nucleus. Statistical Model Calculation 16 O... 18 O 18 O Fission Probability 240 U * … 238 U 238 U We are getting an evidence that fission probability changes with scattering angle. Excitation Energy (MeV)

Toward Understanding the Spins of Compound Nucleus (2) Fission Fragment Angular Distribution Fission fragment angular distribution has Information on spins of compound nucleus. 238 U( 18 O, 16 O) 240 U* W = d  fiss / d W (arb.) J (rotation) Axis Fragment φ No Rotation 𝜄 𝑔 Ejectile K θ Projectile cos q f Fragment We are getting an evidence that compound nucleus spins are proportional to the number of transferred nucleons.