Dynamical fission in Sn induced reactions at 35 A. MeV CHIMERA-ISOSPIN Collaboration (*) (*)...
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Transcript of Dynamical fission in Sn induced reactions at 35 A. MeV CHIMERA-ISOSPIN Collaboration (*) (*)...
Dynamical fission in Sn induced reactions at 35 A.MeV CHIMERA-ISOSPIN Collaboration(*)
(*) presented by Paolo Russotto INFN CT-LNS
XII Nuclear Physics Workshop Marie and Pierre Curie Nuclear Structure and Low Energy Reactions
September 21-25, 2005 Kazimierz Dolny, Poland
Analysed systems
124Sn+64Ni at 35 A.Mev neutron rich
112Sn+58Ni at 35 A.Mev neutron poor
Phenomenon
Fission of projectile like fragments (PLF) in peripheral and semi-peripheral reaction
Competition
Statistical “slow” equilibrated fission
Vs
“Dynamical” “fast” non-equilibrated fission
E.De Filippo et al., Phys. Rev. C 71, 064604 (2005)
100Mo + 100Mo at 19 A.MeV
A.A. Stefanini et al.,
Z. Phys. A351 (1995) 167
1m
1°
30°
176°
•good angular resolution
•identification in mass and/or charge of the detected particles
•low detection threshold and high dynamical range in energy
•direct velocity measurement (TOF)
The CHIMERA detector
TARGET
Beam
REVERSE
Forward part
1°
30°
REVERSE Experiment: 688 Telescopes, forward part. (2000-2002)
2003/2004- CHIMERA-ISOSPIN 1192 telescopes
Si
CsI(Tl)p
t
d
4He6He
3He
LiH.I.
E-TOF E-TOF M,E E-E E-E Z,E
PSD LCP
NOTE:Z2F=37-57 Zproj log scaleAH/AL Mass asymmetries
2 < multiplicity < 7 (peripheral reactions) Data Analysis focused on two heaviest fragmentsE
2F =
kin
etic
en
ergy
of
the
two
frag
men
ts
Cen
tral
ity
of c
olli
sion
Coulomb ring < Vbeam = 8 cm/ns
Well defined PLF source: sequential scattering of PLF followed by its splitting into 2 fragments.
The lighter fragments are emitted
preferentially backwards in the PLF reference system, i.e.,
towards the target nucleus:
Dynamical Fission
Angular distribution are not forward/backward symmetric.
fast process Time interval between the two steps
much shorter than PLF rotational time
In the neutron rich system the Dynamical effects are
stronger than in the neutron poor system
In-plane () and out-of-plane () angles definition [A.A. Stefanini et al., Z.Phys. A 351(1995)167]]
Note:VLpar>4 cm/ns
Time estimation
Time interval between collision and PLF splitting: 100-300 fm/c
Asymmetric cases (outside Coulomb ring) shortest time scale: 40-120 fm/c
E.De Filippo et al., Phys. Rev. C 71, 064604 (2005)
E.De Filippo et al., Phys. Rev. C 71, 044602 (2005)
V.Baran et al., Nucl. Phys. A730, 329 (2004)
Difference: ??? no models nor simulations capable of describing
Dynamical fission
DYN/TOT [%]
-180 -135 -90 -45 0 45 90 135 1800
500
1000
1500
2000
2500
3000
Equilibrated
Dynamical
124Sn+64Ni E2F
=2700-3060 MeV AH/AL=1.6-2.6Y
ield
plane
(deg)
Conclusion
Analysed system 124Sn+64Ni at 35 A.Mev
112Sn+58Ni at 35 A.Mev
•Peripheral and semi-peripheral reactions are basically binary:PLF+TLF
•We have analysed the sequential splitting of PLF in two fragments of comparable masses
•In 20-80% of cases we have observed a fast non-equilibrated dynamical fission of PLF (100<t<300 fm/c): this process is one or two order of magnitude faster than equilibrated fission
•In the neutron rich system the Dynamical effects are stronger (+1030%) than in the neutron poor system
•We are not able to explain the reason of this difference because we have no models nor simulations capable of describing Dynamical fission
•Further analysis and theoretical model are required!!
COLLABORAZIONE ISOSPINCOLLABORAZIONE ISOSPINE. De Filippob, A. Paganob, E. Piaseckic, F. Amorinia, A. Anzalonea, L. Auditored, V. Barana, I. Berceanue, J.
Blicharskaf, J. Brzychczykg, A. Bonaseraa, B. Borderieh, R. Bougaulti, M. Brunoj, G. Cardellab, S. Cavallaroa, M.B. Chatterjeek, A. Chbihil, M. Colonnaa, M. D'Agostinoj, R. Dayrasm, M. Di Toroa, J. Franklandl, E.
Galicheth, W. Gawlikowiczg, E. Geracij, F. Giustolisia, A. Grzeszczukf, P. Guazzonin, D. Guineto, M. Iacono-Mannoa, S. Kowalskif, E. La Guidaraa, G. Lanzanob, G. Lanzalonea, N. Le Neindreh, S. Lip, S. Lo Nigroa, C. Maiolinoa, Z. Majkag, M. Papab, M. Petrovicie, S. Pirroneb, R. Planetag, G. Politib, A. Pope, F. Portoa, M.F.
Riveth, E. Rosatoq, F. Rizzoa, S. Russon, P.Russottoa M. Sassin, K. Schmidte, K. Siwek-Wilczynskac, I. Skwirac, M.L. Sperdutoa, J. C. Steckmeyeri, L. Swiderskic, A. Trifiròd, M. Trimarchid, G. Vanninij, M. Vigilanteq, J.P.
Wieleczkol, J. Wilczynskir, H. Wup, Z. Xiaop, L. Zettan, and W. Zipperf
a) INFN, Laboratori Nazionali del Sud and Dipartimento di Fisica e Astronomia, Università di Catania, Italyb) INFN, Sezione di Catania and Dipartimento di Fisica e Astronomia, Università di Catania, Italy c) Institute of Experimental Physics, Warsaw University, Warsaw, Polandd) INFN, Gruppo Collegato di Messina and Dipartimento di Fisica, Università di Messina, Italy e) Institute for Physics and Nuclear Engineering, Bucharest, Romaniaf) Institute of Physics, University of Silesia, Katowice, Polandg) M. Smoluchowski Institute of Physics, Jagellonian University, Cracow, Polandh) Institute de Physique Nucléaire, IN2P3 and Université Paris-Sud, Orsay, Francei) LPC, Ensi Caen and Université de Caen, Francej) INFN, Sezione di Bologna and Dipartimento di Fisica, Università di Bologna, Italyk) Saha Institute Of Nuclear Physics, Kolkata, Indial) GANIL, CEA, IN2P3, Caen, Francem) DAPNIA/SPhn, CEA-Saclay,Francen) INFN, Sezione di Milano and Dipartimento di Fisica, Università di Milano, Italyo) IPN, IN2P3-CNRS and Université Claude Bernard, Lyon, Francep) Institute of Modern Physics, Lanzhou, Chinaq) INFN, Sezione di Napoli and Dipartimento di Fisica, Università di Napoli, Italyr) A. Soltan Institute for Nuclear Studies, Swierk/Warsaw, Poland
Relative velocities between two fragments normalized to velocity resulting from Coulomb repulsionViola Systematics [D.J. Hinde et al., Nucl. Phys. A472, 318 (1987)]
The velocity field of various parts of the PLF did not attain
equilibrium as in statistical fission
<Vratio> larger then 1 (+20%) in plane dynamical region
Note:VLpar>4 cm/ns
out=90°
in-plane emission
Exponentially decreasing distribution: dynamical
Flat distribution: statistical
NOTE: TLF’s fragments have been cut off; VLpar >4cm/ns.
Dyn: -30°< plane <45°
Eq: -130°<plane<-90° and -90°<plane<130°
Dyn: -30° < plane< 45°
Eq: -130° < plane< -90° and -90° <plane <130°
NOTE:
Angular coverage
1°<lab< 30°
log scale
Outside Coulomb ring and largest asymmetries neck emission
[E.De Filippo et al., Phys. Rev. C 71, 044602 (2005)]
VLpar>4 cm/ns and Z2F Zproj
PLF splitting into 2 main fragments
Low velocity and Z2F >Zproj
Target remnants
AH/AL Mass asymmetries
E2F
peripherality
NOTE:in the highest asymmetry ZL> 9
Data Analysis focused on two heaviest fragments
Conditions
2 < multiplicity < 7 (peripheral reactions)
30<ZTOT<80 and Z2F>15
log scale
AH/AL Mass asymmetries
E2F
peripherality
log scale
How to select peripherality in both system to compare them????????
Angular coverage 1°<lab< 30° no Energy Transverse lcp,
no Total Kinetic Energy Loss (TKEL)
E2F TKEL and centrality of the collision
The global variables show
a similar behaviour for both system
Selection of same percentage of events in the E2F distribution
Example:velocity of the source of the two heaviest fragments
DYN/TOT [%]
(124Sn+64Ni) – (112Sn+58Ni)
2.6-4.6 1.6-2.6 1.0-1.62700-3060 7% 17% 6%3060-3450 15% 26% 6%3450-4000 19% 22% 11%
(124Sn+64Ni)-(112Sn+58Ni)DYN/(DIN+EQ)
AH/AL.
E2F(MeV)
2.6-4.6 1.6-2.6 1.0-1.6
2700-3060 83% 71% 37%
3060-3450 78% 57% 26%
3450-4000 71% 53% 42%
AH/AL.
E2F(MeV)
DYN/(DIN+EQ)124Sn+64Ni
2.6-4.6 1.6-2.6 1.0-1.62650-3000 76% 53% 31%3000-3360 63% 31% 20%3360-4000 52% 31% 30%
DYN/(DIN+EQ)AH/AL.
E2F(MeV)
112Sn+58Ni