Isotopic Fission-Fragment Distributions as a
Deep Probe to Fusion-Fission Dynamics
Fanny Farget, Manuel CaamañoUniversidade de Santiago de Compostela (Spain)
O. Delaune, X. Derkx, C. Rodríguez, C. Golabek, A. Navin, M. Rejmund, T. Roger, M.G. Saint-Laurent, H. Savajols, C. Schmitt, C. Stodel, J.C. Thomas, A.C. Villari
GANIL (France)
D. Ramos, J. Benlliure, D. Cortina, B. Fernández USC (Spain)
O. Tarasov, D. Bazin, W. Mittig, D.J. Morrisey, J. Pereira, B.M. Sherrill NSCL (USA)
K.-H. Schmidt, B. Blank, S. Grévy, B. Jurado CENBG (France)
E. Casarejos U. de Vigo (Spain)
L. Audouin, C-O Bacri, L. Perrot IPNO (France)
A. Heinz U. of Chalmers (Sweden)
D. Doré, M. Delphine de Salsac SPhN (France)
S. Lukyanov FNLR (Russia)
L. Gaudefroy CEA DIF (France)
Experimental observables
Mass, Z, and TKE showed that shell effects come
into play
Measurements of fragment distributions and yields hints
on the dynamics of fission
K.F. Flynn et al. PRC 5 (1972) 1725 C. Böckstiegel et al. NPA 802 (2008) 12
B. Jurado et al. PRL 93 (2004) 072501
Y. Ayyad, PhD U. Santiago C (2012)2
Fission probabilities reveal barrier’s features
C. Rodríguez-Tajes et al., to be published
Experimental observablesDifferent reactions grant the access to different observables and conditions
neutron - induced fission: - control of E*- no high L------ limited to stable targets- no access to Z
spallation/EM - induced fission: - inverse kinematics (A, Z of fragments)- access to unstable FS- no high L------ no control of E*- reduced control on FS
fusion - induced fission: - control of E*- access to unstable FS------ high L- quasi-fusion
transfer - induced fission:- control of E*- inverse kinematics (A, Z of fragments)- access to unstable FS- includes fusion for free------ high L- quasi-fusion
3
Dire
ct ki
nem
atics Inverse kinem
atics
Transfer/fusion-induced fission: three flavors
238U (6.1 AMeV) + 12C 238U (24 AMeV) + 12C/9Beat VAMOS at LISE
!"
!"#$%
&'()%&*%+%,$-%
.$%.$%
/0%12345%67"7%
,8!9%:;<"%=">%%
238U (6 AMeV) + 12C/2H/1Hwith MAYA
4
238U (6.1 AMeV) + 12C at VAMOS- Setup based on inverse kinematics
- Transfer reactions produce unstable species, induce fission.
FS’s observables: Z, A, E*. Fragments’ observables: Z, A, q, angles, velocity, gammas.
Fragment 1MW: ToFCD: x, y positionsIC, Si: dE-E Target-like recoil
SPIDER (double stripped Si detector): dE-E, angles
Fragment 2MW: ToFIC, Si: dE-E
Exogam: Gammas
5
238U (6.1 AMeV) + 12C at VAMOSA from 80 to 160 (σ/A~0.3 %) and Z from 30 to 70 (σ/Z~0.9 %)
confirmed by gamma identification.
~10 q states per isotope
D. Ramos, PhD at U. Santiago de Compostela6
238U (6.1 AMeV) + 12C at VAMOSThe target-like recoil tags the different FS
the E* (σ~1 MeV) is deduced from kinematics.
Fission probability shows barrier’s features
C. Rodríguez-Tajes et al., to be published
7
FSbeam
recoil
FF
FF
238U (6.1 AMeV) + 12C at VAMOS
-210
-1101 Se34
-210
-1101 Br35
-210
-1101 Kr36
50 60 70-210
-1101 Rb37
Sr38
Y39
Zr40
50 60 70
Nb41
Mo42
Tc43
Ru44
60 70 80
Rh45
Pd46
Ag47
Cd48
60 70 80
In49
Sn50
Sb51
Te52
70 80 90
I53
Xe54
Cs55
Ba56
70 80 90
La57
Ce58
Pr59
70 80 90
Nd60
Neutron number
Nor
mal
ized
yiel
ds
12C ( 238U , 240Pu (E*~9 MeV) ) 10Be
Z30 40 50 60
Nor
mal
ized
yiel
d
0
5
10
15
(a)<N
>/Z
1.4
1.45
1.5
1.55
1.6
1.65
A80 100 120 140 160
Nor
mal
ized
yiel
d
2
4
6
8 (b)
M. Caamaño et al. PRC 88 (2013) 024605
A. Bail et al. PRC 84 (2011)
034605
C. Schmitt et al. NPA 430 (1984) 21
8
238U (6.1 AMeV) + 12C at VAMOS
- evolution of A, Z, <N>/Z distributions with E*
- gradual disappearance of shell effects
D. Ramos, PhD at U. Santiago de Compostela
– – GEF (K.-H. Schmidt & B. Jurado)
9
240Pu (E*~9 MeV)
238U (6.1 AMeV) + 12C at VAMOS<N
>/Z
1.45
1.5
1.55
1.6 (a)
Z35 40 45 50 55 60
(Z)
!
-20246 (b)
LD scission-point model
the obtained results can be linked to deformed shell effects
(b)
LD scission-point modelEtot = ELD(Z1,A1) + ELD(Z2,A2)
M. Caamaño et al. PRC 88 (2013) 024605
B.D. Wilkins et al. PRC 14 (1976) 1832
D. Ramos, PhD at U. Santiago de Compostela10
240Pu (E*~9 MeV)
238U (6.1 AMeV) + 12C at VAMOS
Z30 40 50 60
> (c
m/n
s)fis
s<v
0.8
1
1.2
1.4
1.6
1.41.61.8 Zn30
Y39
Cd48
La57
Ga31
Zr40
In49
40 60 80 1000.81
1.2 Ce58
Ge32
Nb41
Sn50
40 60 80 100
Pr59
As33
Mo42
0.81
1.2
Sb51
40 60 80 100
Nd60
Se34
Tc43
Te52
40 60 80 100
Pm61
Br35
11.21.4
Ru44
I53
40 60 80 100
Sm62
Kr36
Rh45
Xe54
40 60 80 100
Eu63
1.21.41.6 Rb37
Pd46
Cs55
40 60 80 100
Gd64
Sr38
Ag47
Ba56
Neutron number
(cm
/ns)
fiss
v) (cm/ns)fisscos(fissv-0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8
) (cm
/ns)
fiss
sin(
fiss
v
0
0.2
0.4
0.6
0.8
1
1.2
1.4
The fragments’ velocities are also available.240Pu follows the systematics of Wilkins.250Cf deviates at light fragments.
250Cf240Pu
M. Caamaño et al. PRC 88 (2013) 024605
11
240Pu (E*~9 MeV)
A80 100 120 140 160
Nor
mal
ized
yiel
d
0
1
2
3
4
(b)
Z30 35 40 45 50 55 60 65
Nor
mal
ized
yiel
d
0
2
4
6
8
10
12 (a)<N
>/Z
1.35
1.4
1.45
1.5
1.55
238U (6.1 AMeV) + 12C at VAMOS12C ( 238U , 250Cf (E*~45 MeV) )
-210
-1101 Zn30
-210
-1101 Ga31
-210
-1101 Ge32
-210
-1101 As33
40 50 60 70-210
-110
1 Se34
Br35
Kr36
Rb37
Sr38
40 50 60 70
Y39
Zr40
Nb41
Mo42
Tc43
50 60 70 80
Ru44
Rh45
Pd46
Ag47
Cd48
50 60 70 80
In49
Sn50
Sb51
Te52
I53
60 70 80 90
Xe54
Cs55
Ba56
La57
Ce58
70 80 90 100
Pr59
Nd60
Pm61
Sm62
Eu63
70 80 90 100
Gd64
Neutron number
Norm
alize
d yiel
ds
M. Caamaño et al. PRC 88 (2013) 024605
C. Yadav et al. PRC 86 (2012) 034606
12
238U (6.1 AMeV) + 12C at VAMOS
Fusion-fission reaction: angular momentum distribution
High excitation energy: multi-chance fission
Lcrit~23ħ
GEF output for E*=45 L=16
13
250Cf (E*~45 MeV)
238U (6.1 AMeV) + 12C at VAMOS
Widths and shapes behave as expectedwith small differences.
<L> marks the transition to symmetric fission
solid lines: Code GEF (K.-H. Schmidt & B. Jurado)
14
250Cf (E*~45 MeV)
<N>/Z
1.45
1.5
1.55
1.6 (a)
Z35 40 45 50 55 60
(Z)
!
-20246 (b)
238U (6.1 AMeV) + 12C at VAMOS
LD scission-point model
- no polarization at high E*- cannot be reproduced with multi-chance fission and/or <L> influence.
LD scission-point modelEtot = ELD(Z1,A1) + ELD(Z2,A2)
D.J. Hinde et al. PRC 45 (1992) 1229
• Experiment• Experiment
15
250Cf (E*~45 MeV)
238U (24 AMeV) + 12C/9Be at LISE
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,8!9%:;<"%=">%%
- Setup based on inverse kinematics- Fusion-fission at different E*
Fragment 1MWCP: ToF, x, y positionsSi: dE-E
Fragment’s observables: Z, A, q, angles, velocity, gammas.
Spokesperson:O. Tarasov (NSCL)
16
238U (24 AMeV) + 12C/9Be at LISE
238U + 12C238U + 9Be
132Sn ~10 pps O. Delaune et al., to be published
17
238U + 12C/9Be
250Cf 238U (6.1 AMeV) + 12CE* = 45 MeV<L>~152*<Z>=98 2*<A>=243 (ν~7)
E* = 250 - 200 MeV <L>~952*<Z>=92 2*<A>=219 (ν~?)
E* = 200 - 150 MeV <L>~752*<Z>=96 2*<A>=232 (ν~15)
247Cm 238U (24 AMeV) + 9Be
250Cf ? 238U (24 AMeV) + 12C
no fusion occursO. Delaune et al., to be published
18
Fusion-fission summary
238U + 12C/9Be
U+C 6 AMeVU+Be 24 AMeVU+C 24 AMeVU+d 1 AGeV
U+C 6 AMeVU+Be 24 AMeVU+C 24 AMeVU+d 1 AGeV
polarisation width of isotopic distribution
- As E* diminishes, <N>/Z becomes flat in U+C @ 6 AMeV (!!)- U+Be recovers some shell influence (maybe due to evaporation)
- U+C @ 24 AMeV is remarkably similar to spallation reactions
J. Pereira et al. PRC 75 (2007) 014602
O. Delaune et al., to be published
19
Fusion-fission summary
Summary and conclusions
• The study of transfer- and fusion-induced fission in inverse kinematics allows the access to observables not available so far.• We have shown A, Z, <N>/Z, and velocity distributions for 250Cf, 247Cm, and 240Pu, and their evolution with E* and the reaction mechanism.
• The 240Pu measured distributions are in agreement with their expected behaviour.• 250Cf with E*=45 MeV shows unexpected features in <N>/Z, velocity, and isotopic distributions.
• The results on 250Cf reveal the need for a better understanding of the fission process, post-saddle.• The study of the isotopic distributions of fission fragments proves to be a valid tool to extract new information on the fission dynamics.