Fission studies at R3B using the SOFIA setup NUSTAR week 2019 Gif -sur-Yvette, France September 25 2019 A. Chatillon (CEA, DAM, DIF) for the R 3 B/SOFIA collaboration
SOFIA@R3B Some results from 2012-2014 Proposal for 2020 and after ? Summary & Conclusion Why studying fission at R3B ? I - Large physics case: applications, r-process, understanding the reaction for models T . I c h i k a w a e t a l . , P R C 8 6 ( 2 0 1 2 ) 0 2 4 6 1 0 (A,Z,E*) compound nucleus Transient time PES: static properties dynamics propagation (A 2 ,Z 2 ) FF2 FF1 gamma neutrons (A 1 ,Z 1 ) SOFIA@R3B: correlation of several fi ssion observables for a complete description YIELDS: Y(Ai,Zi) EVOLUTION WITH E* BARRIER PROBABILITY P R O M P T E M I S S I O N NUSTAR week SOFIA: Fission@R3B A. Chatillon 2/16
SOFIA@R3B Some results from 2012-2014 Proposal for 2020 and after ? Summary & Conclusion Why studying fission at R3B ? II - To avoid the limitation due to direct kinematics DIRECT KINEMATICS: FF WITH LOW RECOIL ENERGY IN THE LAB. FRAME Beam = neutrons, light charged particles, γ & Target = actinides Isotopic yields are incomplete nuclear charge from energy loss measurement: ⇒ limitation to Z ≤ 42 mass from total energy measurement: ⇒ resolution around 4 mass unit FWHM targets limited to long-lives nuclei very low efficiency due to the 4- π emission ⇒ low statistics NUSTAR week SOFIA: Fission@R3B A. Chatillon 3/16
SOFIA@R3B Some results from 2012-2014 Proposal for 2020 and after ? Summary & Conclusion Why studying fission at R3B ? II - To avoid the limitation due to direct kinematics... ... thanks to the powerful tool of the inverse kinematics at relativisitic energy INVERSE KINEMATICS AT 700 A.MeV: (Z,A) IDENTIFICATION FROM ∆ E-B ρ -ToF Radioactive beam & Surrogate reactions analysis by L. Grente 8000 electromagnetic induced fission 7000 FRS + R3B : (Z,A) identification of the 6000 compound nucleus and both fission fragments 5000 counts after neutron emission 4000 3000 ∆ Z = 0.35 charge unit FWHM 2000 1000 0 ∆ A = 0.5 to 0.8 mass unit FWHM 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 nuclear charge (Z) total prompt neutron multiplicity from A CN = A FF1 − A FF2 Use of radioactive beams: broad range of fissioning nuclei Use of surrogate reactions to produce the compound nucleus: ⇒ coulex induced fission: accurate measurement of Y(A,Z) and ν tot at � E ∗ CN � ∼ 14 MeV ⇒ (p,2pf): first experiment in 2020 to measure E ∗ in coincidence: Complementary experiment! very high geometrical efficiency: around 90 % (from 236 U( γ ,f) data in 2014) NUSTAR week SOFIA: Fission@R3B A. Chatillon 4/16
SOFIA@R3B Some results from 2012-2014 Proposal for 2020 and after ? Summary & Conclusion Two experiments in 2012 and 2014 at R3B with ALADIN 2012: Coulex-induced fission in the uranium and thorium regions (J. Taieb et al. ) 2012: Spallation-fission of 208 Pb (J. Benlliure et al. ) 2014: Coulex-induced fission of 236 U (J. Taieb et al. ) ∆E-B ρ -ToF applied at Cave C ∆E-B ρ -ToF applied at FRS 3 50 x10 236 U 45 40 35 counts 30 analysis by L. Grente 25 20 15 10 5 0 93.5 2.56 93 92.5 234 Pa 2.565 e g 92 r A a h / Z c 91.5 r a e 2.57 c l u 91 n 90.5 NUSTAR week SOFIA: Fission@R3B A. Chatillon 5/16
SOFIA@R3B Some results from 2012-2014 Proposal for 2020 and after ? Summary & Conclusion Accurate yields along the uranium chain Error bars are shown in figures ⇒ Elemental yields: σ asym ≤ 1% and σ sym ≤ 2% ⇒ Isotopic yields: σ light ≤ 2%, σ sym ≤ 3% and σ heavy ≤ 5% 234,235 234,235 236 238 analysed by : J.-F. Martin ( U), G. Boutoux ( U), L. Grente ( U) and E. Pellereau ( U) 16 234 U 14 235 U 235 analysed by : J.-F. Martin ( U) 12 Y(Z) [%] 236 U Z=32 Z=42 Z=52 10 3.5 Z=33 Z=43 Z=53 238 U 8 Z=34 Z=44 Z=54 3 6 Z=35 Z=45 Z=55 Y(Z,N) [%] Z=36 Z=46 Z=56 4 2.5 Z=37 Z=47 Z=57 2 Z=38 Z=48 Z=58 2 0 Z=39 Z=49 Z=59 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 nuclear charge (Z) Z=40 Z=50 Z=60 1.5 Z=41 Z=51 1 234 U 234 U 2.8 16 235 U 235 U 15 Y(Z) [%] Y(Z) [%] 0.5 236 U 236 U 2.4 14 238 U 238 U 0 13 45 50 55 60 65 70 75 80 85 90 95 2 12 number of neutrons (N) 11 1.6 10 43 44 45 46 47 48 49 52 53 54 55 56 nuclear charge (Z) nuclear charge (Z) J.-F. Martin, J. Taieb et al. , Eur. Phys. J. A 51 (2015) 541 E. Pellereau, J. Taieb et al. , Phys. Rev C 95 (2017) 054603 NUSTAR week SOFIA: Fission@R3B A. Chatillon 6/16
SOFIA@R3B Some results from 2012-2014 Proposal for 2020 and after ? Summary & Conclusion From asymmetric to symmetric fission along the thorium chain (I) First observed from Y(Z) measurement in the 90’s (K.-H. Schmidt et al., NPA 665 (2000) 221) SOFIA: measurement of Y(Z), Y(N), Y(A) and prompt-neutron multiplicity 230 Th 226 Th 222 Th 8 Y(A) [%] 6 4 2 0 80 90 100 110 120 130 140 150 80 90 100 110 120 130 140 150 80 90 100 110 120 130 140 150 mass (A) 12 Y(N) [%] 10 8 6 4 2 0 50 55 60 65 70 75 80 85 50 55 60 65 70 75 80 85 50 55 60 65 70 75 80 85 number of neutron (N) 20 Schmidt et al. Y(Z) [%] 15 SOFIA 10 5 0 35 40 45 50 55 35 40 45 50 55 35 40 45 50 55 nuclear charge (Z) A. Chatillon, J. Taieb et al. , Phys. Rev C 99 (2019) 054628 NUSTAR week SOFIA: Fission@R3B A. Chatillon 7/16
SOFIA@R3B Some results from 2012-2014 Proposal for 2020 and after ? Summary & Conclusion From asymmetric to symmetric fission along the thorium chain (II) Probe the scission configuration thanks to � ν tot � ( Z ) ⇒ � ν tot � ( Z ) increases with the Q 2 -deformation of the fission-fragments Prompt neutron multiplicity drops at symmetry 236 U 230 Th 226 Th 222 Th 7 A. Chatillon, J. Taieb et al. , in preparation 6 〈ν tot 〉 5 4 3 Y(Z) [%] 15 10 5 0 35 40 45 50 55 60 35 40 45 50 55 35 40 45 50 55 35 40 45 50 55 nuclear charge (Z) new compact scission configuration at symmetry for the light thorium totaly different from the known elongated symmetric scission mode in uranium region NUSTAR week SOFIA: Fission@R3B A. Chatillon 8/16
SOFIA@R3B Some results from 2012-2014 Proposal for 2020 and after ? Summary & Conclusion 208 Pb(p,f) at 500 A.MeV Application: characterize the spallation neutron sources and secondary beam facilities Understanding of the dynamics in fission through the dissipation parameters Isotopic identification of both FF: Z 1 + Z 2 are obtained unambigously in coincidence with ⇒ fission cross section ⇒ neutron excess in the fission fragments Ground to saddle dynamics Saddle to scission dynamics neutron excess cross section J. L. Rodriguez-Sanchez et al. , Phys. Rev C 94 (2016) 061601 (R) J. L. Rodriguez-Sanchez et al. , Phys. Rev C 91 (2015) 064616 NUSTAR week SOFIA: Fission@R3B A. Chatillon 9/16
SOFIA@R3B Some results from 2012-2014 Proposal for 2020 and after ? Summary & Conclusion Accepted proposal for Fission@R3B (s455) 1. Temperature dependance of shell effects in the PES and energy sharing between FF: ⇒ (p,2p) induced fission of 238 U primary beam 2. Fission barrier around N=126 in Po isotopes: ⇒ (p,2p) induced fission of radioactive beams 3. Symmetric to asymmetric fission in neutron deficient A=180-210 nuclides: ⇒ coulex induced fission of radioactive beams Setup based on a common basis Active T arget: coulex U C GLAD T win MUSIC fragmentation target (Be) ( ∆ E, Θ ) Triple-MUSIC Anodes 1,2 with He stripper (Nb) ( Δ E, Θ ) degrador (Al) stripper (Cu) TARGET AREA 238 U primary beam cathode LH2+Si+CALIFA: (p,2pf) anode plane central MWPC0 (x,y) cathode anode planes MWPC 1 MWPC 2 MWPC 3 (x 1 ,y 1 ) (x 2 ,y 2 ) (x 3 ,y 3 ) 1,2 1,2 1,2 T oF wall ( Θ , Φ ) scintillator scintillator 1,2 fl ight path ~ 138m (beam) fl ight path ~ 8 m ( fi ssion-fragments) NUSTAR week SOFIA: Fission@R3B A. Chatillon 10/16
SOFIA@R3B Some results from 2012-2014 Proposal for 2020 and after ? Summary & Conclusion (p,2p) induced fission of primary 238 U beam. J. Benlliure et al. Damping of the shell effects with E ∗ & Energy sharing between FF AIM : Evolution of the fission observables as a function of E ∗ : from B f to 80 MeV Yields and prompt-neutron multiplicity depends on E ∗ and ( A CN , Z CN ) BUT : Difficult to study such effect in direct kinematics SOLUTION : Couple R3B/SOFIA with LH2 target, the Si tracker and CALIFA ⇒ 238 U(p,2pf): tracking of the protons to measure E ∗ ⇒ R3B/SOFIA: isotopic identification of both FF and total prompt-neutron multiplicity NeuLAND can be used to measure the prompt-neutron multiplicity per fragment Describe the evolution of the shell effects as a function of the excitation energy How the additional excitation energy is shared between the FF ? NUSTAR week SOFIA: Fission@R3B A. Chatillon 11/16
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