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1
XII Nuclear Physics Workshop Marie and Pierre
Curie Nuclear Structure and Low Energy Reactions
September 21-25, 2005 Kazimierz Dolny, Poland
Dynamical fission in Sn induced reactions at 35
A.MeV  CHIMERA-ISOSPIN Collaboration() ()
presented by Paolo Russotto INFN CT-LNS
2
Analysed systems 124Sn64Ni at 35 A.Mev ? neutron
rich 112Sn58Ni 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
3
The CHIMERA detector
Beam
REVERSE Experiment 688 Telescopes, forward part.
(2000-2002) 2003/2004- CHIMERA-ISOSPIN 1192
telescopes
TARGET
176
REVERSE Forward part
30
1
30
1m
1
  • 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)

DE-TOF M,E
4
2 lt multiplicity lt 7 (peripheral reactions) ??
Data Analysis focused on two heaviest
fragments
5
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
6
Difference ??? ?no models nor simulations
capable of describing Dynamical fission
7
  • Conclusion
  • Analysed system 124Sn64Ni at 35 A.Mev
  • 112Sn58Ni at 35 A.Mev
  • Peripheral and semi-peripheral reactions are
    basically binaryPLFTLF
  • 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
    (100lttlt300 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 (10?30) 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!!

8
COLLABORAZIONE ISOSPIN
E. 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, Italy b) INFN, Sezione di Catania and
Dipartimento di Fisica e Astronomia, Università
di Catania, Italy c) Institute of Experimental
Physics, Warsaw University, Warsaw, Poland d)
INFN, Gruppo Collegato di Messina and
Dipartimento di Fisica, Università di Messina,
Italy e) Institute for Physics and Nuclear
Engineering, Bucharest, Romania f) Institute of
Physics, University of Silesia, Katowice,
Poland g) M. Smoluchowski Institute of Physics,
Jagellonian University, Cracow, Poland h)
Institute de Physique Nucléaire, IN2P3 and
Université Paris-Sud, Orsay, France i) LPC, Ensi
Caen and Université de Caen, France j) INFN,
Sezione di Bologna and Dipartimento di Fisica,
Università di Bologna, Italy k) Saha Institute Of
Nuclear Physics, Kolkata, India l) GANIL, CEA,
IN2P3, Caen, France m) DAPNIA/SPhn,
CEA-Saclay,France n) INFN, Sezione di Milano and
Dipartimento di Fisica, Università di Milano,
Italy o) IPN, IN2P3-CNRS and Université Claude
Bernard, Lyon, France p) Institute of Modern
Physics, Lanzhou, China q) INFN, Sezione di
Napoli and Dipartimento di Fisica, Università di
Napoli, Italy r) A. Soltan Institute for Nuclear
Studies, Swierk/Warsaw, Poland
9
Relative velocities between two fragments
normalized to velocity resulting from Coulomb
repulsion?Viola Systematics D.J. Hinde et al.,
Nucl. Phys. A472, 318 (1987)
NoteVLpargt4 cm/ns
ltVratiogt larger then 1 (20) in ?plane dynamical
region
The velocity field of various parts of the PLF
did not attain equilibrium as in statistical
fission
10
?out90 in-plane emission
11
Exponentially decreasing distribution
dynamical Flat distribution statistical
Dyn -30lt ?plane lt45 Eq -130lt?planelt-90
and -90lt?planelt130
NOTE TLFs fragments have been cut off VLpar
gt4cm/ns.
12
Dyn -30 lt ?planelt 45 Eq -130 lt ?planelt
-90 and -90 lt?plane lt130
13
Outside Coulomb ring and largest asymmetries?
neck emission E.De Filippo et al., Phys. Rev. C
71, 044602 (2005)
log scale

NOTE Angular coverage 1lt?lablt 30
14
Data Analysis focused on two heaviest
fragments Conditions 2 lt multiplicity lt 7
(peripheral reactions) 30ltZTOTlt80 and Z2Fgt15
NOTEin the highest asymmetry ZLgt? 9
AH/AL Mass asymmetries
log scale
Low velocity and Z2F gtZproj Target remnants
E2F?peripherality
VLpargt4 cm/ns and Z2F ? Zproj PLF splitting into
2 main fragments
15
AH/AL Mass asymmetries
log scale
E2F?peripherality
16
How to select peripherality in both system to
compare them???????? Angular coverage 1lt?lablt
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
17
Examplevelocity of the source of the two
heaviest fragments
18
DYN/TOT (124Sn64Ni) (112Sn58Ni)
19
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