Status of the Subtask 6 Heavy ion reactions in the Fermi-energy domain M. Veselsky, IoP SASc Bratislava Main objective: Investigation of the production cross sections of exotic n-rich nuclei in the heavy ion reactions in the Fermi-energy domain

Peripheral collisions 86 Kr + 64 Ni, 112,124 Sn at 25 AMeV (M.Veselsky, G.Souliotis, NPA765(2006)252) - enhancement of the neutron-rich products in the peripheral collisons, inversion of the bulk isospin equilibration flow - a correction to model of Deep-Inelastic Transfer ( version of Tassan-Got ) describes the effect of shell structure on isospin asymmetry at nuclear periphery - consistent description for all reactions using identical parameter κ - statistical multifragmentation model (SMM reproduces the yields of n-rich species well while overestimating the yields of β-stable isotopes close to the projectile - model of sequential binary decay (SBD) typically overestimates the width of mass distributions - for p-rich target 112 Sn stronger Coulomb interaction supresses the effect of isospin asymmetry at nuclear periphery at separations below 1 fm ( see dash-dotted line ) 86 Kr + 64 Ni at 25 AMeV solid - SBD, dash -SMM, dash-dot - SMM+Coulomb 86 Kr Sn at 25 AMeV

Central collisions in reactions 86 Kr + 112,124 Sn at 25 AMeV (M. Veselsky and G. Souliotis, Nucl.Phys. A781, 521 (2007)). For reaction products with ΔZ > the cold fragments from the incomplete fusion increasingly dominate on the neutron-rich side. However, the simple geometric fragmentation model with combinatorial probabilities overestimates the observed yields (dashed line). Model of incomplete fusion was modified for cold fragments by introducing the extra isospin-dependent component of the excitation energy due to the energetic cost of neutron transfer (M. Veselsky and G. Souliotis, Nucl.Phys. A781, 521 (2007), solid line). For reaction products with ΔZ > the cold fragments from the incomplete fusion increasingly dominate on the neutron-rich side. However, the simple geometric fragmentation model with combinatorial probabilities over- estimates the observed yields (dashed line). Model of incomplete fusion was modified for cold fragments by introducing the extra isospin-dependent component of the excitation energy due to the energetic cost of neutron transfer (solid line). 86 Kr(25AMeV)+ 124 Sn deg 86 Kr(25AMeV)+ 112 Sn deg

Isoscaling in nuclear processes - symmetry energy ? - isospin equilibration ? - fluctuation-dissipation ? - reaction dynamics ? M.B. Tsang et al., PRL 86(2001)5023 G. Souliotis et al., PRC 68(2003)24605 M. Veselský et al., PRC 69(2004)44607

18 O Ta at 35 AMeV, carbon isotopes Experiment (COMBAS) PE+DIT/ICF+SMM

18 O Ta at 35 AMeV, beryllium isotopes 7 Be - fast component, intense pre-eq emission, ICF kinematically impossible, motion along classical Coulomb trajectory ? Transparency ? Experiment (COMBAS) PE+DIT/ICF+SMM 7 Be

Codes – status: - DIT model verified, modified ( n-skin ) - ICF model verified, modified ( N/Z-dependent E * ) - pre-eq model verified ( COMBAS data ) - Weisskopf-Ewing valid below 1 AMeV - SMM valid above 3 AmeV - ABLA-07 or other alternative ?

132 Sn beam - production cross sections for fragmentation and Fermi energy domain ( 132 Sn(28AMeV)+ 238 U). Black, red, green and blue lines - modified and standard DIT/ICF, EPAX and COFRA, respectively.

132 Sn beam - in-target production rates for fragmentation and Fermi energy domain ( beam rate s -1 )

Notes on: Heavy Residue Measurements at 15 MeV/nucleon

MARS Recoil Separator Setup for 15 MeV/u DIC Studies PPAC2 X,Y, Stop T Silicon Telescope: ΔE 1 (65um) E residual (1mm) PPAC1 Start T X,Y Production Target D1D2 D3 Wien Filter Q1 Q2 Q3 Q4 Q5 Dispersive Image Final Achromatic Image Rotatable Arm Reaction Angle: 0-12 o (selectable) MARS Acceptances: Angular: ~ 3 msr Δθ = 3 ο,Δφ =3 ο Momentum: 4 % Beam angles on tgt: 0 o, 4 o, 7 o Special attention on: 4.0 o ( ) for Kr+Ni (  gr ~5.0 o )

Extracted physical quantities: Velocity, Energy loss, Total Energy Mass-to-charge ratio: A/Q B  ~ A/Q   Atomic Number Z Z ~  ΔE 1/2 Ionic charge Q Q ~ f(E, , B  ) Mass number A A = Q int  A/Q Reconstructed: PLF Yield distribution (Z,A,υ) at each of the two beam-angle settings Reactions recently measured with MARS at 4 o and 7 o 86 Kr (15 MeV/u, 10 pnA) + 64,58 Ni (2.2 mg/cm 2 ) (  gr ~ 6.0 o ) + 124,112 Sn (2.0 mg/cm 2 ) (  gr ~ 8.0 o ) 40 Ar (15 MeV/u, 10 pnA) + 64,58 Ni (2.2 mg/cm 2 ) (  gr ~ 7.0 o ) + 124,112 Sn (2.0 mg/cm 2 ) (  gr ~ 9.0 o ) Rare Isotope production at 15 MeV/nucleon: Measured quantities: x-position at First Image (Bρ info.), ΔE 1, Ε r, time of flight (START-STOP)

Example of on-line Z-A: 86 Kr(15MeV/u) Sn B  =1.5 Tm Reaction Angle: 7.0 deg. Z A -4p Kr Ge Rare Isotope production at 15 MeV/nucleon: -2p+2n Se

Further progress : - analyze experiment - validate cross section simulations - write detailed report - thick target experiment ?