14th edi)on of the Interna)onal Conference on Nuclear Reac)on Mechanisms: Fission of ac*nide nuclei using mul*- nucleon transfer reac*ons

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1 14th edi)on of the Interna)onal Conference on Nuclear Reac)on Mechanisms: Fission of ac*nide nuclei using mul*- nucleon transfer reac*ons Romain LÉGILLON Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, JAPAN 1

2 Tokai Campus, JAEA Tokyo J- PARC Tandem facility Japan Osaka Tokyo Tokai 2

3 JAEA Tandem facility 20 MV Tandem accelerator (20R) Super-conducting Booster Liniac ECR Ion Source on the terminal Booster linac Negative Ion Source

4 Magnetic Spectrometer Booster Linac Recoil Mass Separator Ge-detector array In beam fission and reaction ISOL p & Gas-jet coupled Radioactive materials can be used,, Np,, Np, Am, Cm, Cf

5 Fission fragment mass/charge distributions Atomic number (Z) Mul* nucleon transfer: Ø Large set of nuclei Ø Wide range of excita*on energy Ra N= Np Cm Cf 241 Am Fm 249 Cf No 226 Ra Rf 232 N= Cm N= Cf Lead to neutron rich ac*nides (ex: 245 Np, 248,249 Am, 253 Bk with unknown masses) Low excita*on fission data Neutron number (N) 5

6 Nuclei in Reactors and Decay-Network RED Long-life MA (Capture is Main process) BLE Fissioning Nuclei GREEN Decay with short life 163d 30y 18.1y 14.9y 242 Cm 243 Cm 244 Cm 245 Cm 242m Am 152y 6h (0.16) 241 Am 242 Am 243 Am 244 Am 16h (0.84) h 10.1h Np 2.12d 237 Np 238 Np 239 Np 2.25h 6.75d d 23.5m Fission and Neutron Capture Cross Sec*on σ fiss and σ capt Prompt Neutron Mul*plicity ν Prompt Neutron Spectrum χ (E n ) Fission fragment mass distribu*on Y(A) Delayed Neutron Yield β n 6

7 Transfer reaction and surrogate reaction - Access many nuclei with wide excitation energy range 16 O 16 O 18 O * Fragment 2 Fragment 1 n 233 ( T 1/2 =22.3m) 7

8 Experimental Setup to measure fragment mass MWPC3 MWPC1 18 O beam Target Fragment 2 Fragment 2 Fragment 1 16 O sca^ered MeV 18 O Beam θ LAB * 16 O Fragment mm 200 mm MWPC4 MWPC2 8

9 Experimental setup: target and ΔE detector Azimuthal angle ΔE = 75μm 18 O 248 Cm Target Sca^ering angle E = 300μm Ø 2.0 mm, 1.5μg, 300Bq 9

10 Transfer Reaction: 18 O O N Pa de (MeV) B C Np Pa 235 Pa E+dE (MeV) E* 10

11 Event reconstruc,on 18 O Target Energy loss Kine*c energy Sca^ering angle Azimuthal angle Recoil Fragment 1 Recoil iden*fica*on Momentum vector Excita*on energy Fragment mass Fission probability: - > Fission barrier Fragment 2 Emission direc*on Time of flight difference 11

12 ( 18 O, 16 O) 240 * Fission Barrier Events / 0.5 MeV (A) Spectrum for 16 O Events / 0.5 MeV (B) Coincidence between 16 O and fission fragments Fission Probability B f 5.5 MeV 2 nd 3 rd (B) (A) 1 Efficiency Excitation Energy (MeV) 12

13 Excitation energy (MeV) = Neutron Energy +S n Fission Fragment Mass Distribution 239 * ß n Mass (u) Mass yield (%) Ex = MeV Ex = MeV 31 45MeV Ex = MeV 19 24MeV Ex = MeV Mass (u) 16 18MeV V.D.Simutkin et al. Nuclear Data Sheets 119(2014)331

14 Excitation Energy vs Fragment Mass 18 O reac*on New New New New 239 Np 240 Np 241 Np 242 Np New Excita*on energy Fission Yield (%) MeV MeV MeV MeV Fragment Mass (u) From K. Hirose 15

15 18 O reac*on Excitation Energy vs Fragment Mass New New New New Pa 233 Pa 234 Pa 235 Pa 236 Pa Excita*on energy MeV Fission Yield (%) Yield (%/u) MeV MeV MeV MeV Fission Fragment mass Fragment mass (u) 0-10 MeV 16

16 233 Ac Excitation Energy vs Fragment Mass New 18 O reac*on Excita*on energy 5 0 Excita*on energy MeV MeV Yield (%/u) MeV MeV MeV MeV MeV MeV MeV Fission fragment mass distribu*on (u) Fragment mass (u) Fission fragment mass distribu*on (u) 17

17 Nuclear Shape two-center parametrization (Maruhn and Greiner, Z. Phys. 251(1972) 431) qzδα (,, ) ( z, δ, α) Charge center Deforma*on (posi*ve and nega*ve) δ1=δ2 is assumed. δ > 0 δ < 0 Mass asymmetry α = 0 α = 0

18 Potential Energy 2 hl( l+ 1) V( q, l, T) = VDM ( q) + + VSH ( q, T) 2() Iq V ( q) = E ( q) + E ( q) DM S C V q T E q T 0 SH (, ) = shell ( ) Φ( ) T : nuclear temperature E * =at 2 a : level density parameter Toke and Swiatecki E S : Generalized surface energy (finite range effect) E C : Coulomb repulsion for diffused surface E 0 shell : Shell correction energy at T=0 I : Moment of inertia for rigid body Φ(T) : Temperature dependent factor # Φ(T ) = exp at 2 & $ ' % ( E d = 20 MeV E d

19 多次元ランジュバン方程式 Mul*- dimensional Langevin Equa*on Multi-dimensional Langevin Equation dq dt dp dt i i = 1 ( m ) V = q i ij p j 2 q 1 ( m ) p p γ ( m ) p + g R ( t) 1 1 jk j k ij i Fric*on Random force dissipa*on fluctua*on jk k ij j R k i ( t) = 0, Ri ( t1) R j ( t2) = 2δ ijδ ( t1 t2 g ik g jk = Tγ ij ) : white noise (Markovian process) q i : deformation coordinate ( z, δ, α) p i : momentum m ij : Hydrodynamical mass (iner*a mass) γ ij : Wall and Window (one-body) dissipation (fric*on ) ( m ) p p V ( q) 1 1 * Eint = E ij i 2 E int :intrinsic energy, E * j : excitation energy

20 Excitation Energy vs Fragment Mass 18 O reac*on New New New New Pa 233 Pa 234 Pa 235 Pa 236 Pa Excita*on energy MeV MeV Fission Yield (%) MeV MeV MeV 0-10 MeV Fragment Mass (u) 22

21 Fission Data from Multi-nucleon Transfer-induced Fission Neutron Detectors (Liquid Scintilator) ν Fission Neutron Mul*plicity 238 ( 18 O, 17 N) 239 Np* Excita*on Energy (MeV)

22 Summary Large set of fissioning nuclei that are under study Large range of excita*on from few MeV up to ~ 50 MeV Evolu*on of Heavy and Light fragment mass in func*on isotopes and excita*on energy Neutron mul*plicity Fission anisotropy 27

23 Collabora,ons K. Nishio, K. Hirose,R. Léguillon, K. Makii, I. Nishinaka, R. Orlandi, J. Smallcombe, S. Chiba, S. Araki, Y. Watanabe, R. Tatsuzawa, N. Takaki, A. Andreyev 28