Spinodal decomposition, nuclear fog and two characteristic volumes in thermal multifragmentation

Thermal multifragmentation of hot nuclei is interpreted as the nuclear liquid-fog phase transition inside the spinodal region. The experimental data for p(8.1GeV) + Au collisions are analyzed within the framework of the statistical multifragmentation model (SMM) for the events with emission of at least two IMFs. It is found that the partition of hot nuclei is specified after expansion to a volume equal to Vt = (2.6+-0.3) Vo, with Vo as the volume at normal density. However, the freeze-out volume is found to be twice as large: Vf = (5+-1) Vo.Comment: 8 pages, 6 figures, to be published in Nucl.Phys.

KRATTA, a triple telescope array for charged reaction products

KRATTA, a new, low threshold, broad energy range triple telescope array has been built to measure the energy, emission angles and isotopic composition of light charged reaction products. It has been equipped with fully digital chains of electronics. The array performed very well during the ASY-EOS experiment, conducted in May 2011 at GSI. The structure and performance of the array are presented using the first experimental results

Nuclear multifragmentation and fission: similarity and differences

Thermal multifragmentation of hot nuclei is interpreted as the nuclear liquid--fog phase transition deep inside the spinodal region. The experimental data for p(8.1GeV) + Au collisions are analyzed. It is concluded that the decay process of hot nuclei is characterized by two size parameters: transition state and freeze-out volumes. The similarity between dynamics of fragmentation and ordinary fission is discussed. The IMF emission time is related to the mean rupture time at the multi-scission point, which corresponds to the kinetic freeze-out configuration.Comment: 7 pages, 3 Postscript figures, Proceedings of IWM 2005, Catani

Critical temperature for the nuclear liquid-gas phase transition (from multifragmentation and fission)

Critical temperature Tc for the nuclear liquid-gas phase transition is stimated both from the multifragmentation and fission data. In the first case,the critical temperature is obtained by analysis of the IMF yields in p(8.1 GeV)+Au collisions within the statistical model of multifragmentation (SMM). In the second case, the experimental fission probability for excited 188Os is compared with the calculated one with Tc as a free parameter. It is concluded for both cases that the critical temperature is higher than 16 MeV.Comment: 15 pages, 8 figure

Background reduction in long CsI(Tl) crystals

A simple method to reduce the background from secondary reactions in telescopes composed of long CsI(Tl) crystals is presented. The method has been developed for the KRATTA [1] modules

Phase transitions in highly excited nuclei

Phase transition in highly excited nucleus is treated in terms of thermo-dynamics of microensembles. The emission of intermediate mass fragments from pure thermally excited heavy nucleus 197Au is an indication of the liquid to fog phase transition. Evidence of the spinodal decomposition of the heavy nuclear system is found and its relation to the multisaddle transition configuration and freeze-out state is presented

KRATTA, a versatile triple telescope array for charged reaction products

A new detection system KRATTA, Krak\'ow Triple Telescope Array, is presented. This versatile, low threshold, broad energy range system has been built to measure the energy, emission angle, and isotopic composition of light charged reaction products. It consists of 38 independent modules which can be arranged in an arbitrary configuration. A single module, covering actively about 4.5 msr of the solid angle at the optimal distance of 40 cm from the target, consists of three identical, 0.500 mm thick, large area photodiodes, used also for direct detection, and of two CsI(1500 ppm Tl) crystals of 2.5 and 12.5 cm length, respectively. All the signals are digitally processed. The lower identification threshold, due to the thickness of the first photodiode, has been reduced to about 2.5 MeV for protons (~0.065 mm of Si equivalent) by applying a pulse shape analysis. The pulse shape analysis allowed also to decompose the complex signals from the middle photodiode into their ionization and scintillation components and to obtain a satisfactory isotopic resolution with a single readout channel. The upper energy limit for protons is about 260 MeV. The whole setup is easily portable. It performed very well during the ASY-EOS experiment, conducted in May 2011 at GSI. The structure and performance of the array are described using the results of Au+Au collisions at 400 MeV/nucleon obtained in this experiment.Comment: 10 pages, 18 figures, accepted by Nucl. Instr. and Meth.

Phase transitions in highly excited nuclei

Phase transition in highly excited nucleus is treated in terms of thermo-dynamics of microensembles. The emission of intermediate mass fragments from pure thermally excited heavy nucleus Au is an indication of the liquid to fog phase transition. Evidence of the spinodal decomposition of the heavy nuclear system is found and its relation to the multisaddle transition configuration and freeze-out state is presented. 19

Isotopic effects in elastic and inelastic 12,13C + 16,18O scattering

New angular-distribution data of 13С + 18О elastic and inelastic scattering at the energy Elab(18O) = 105 MeV were obtained for the transitions to the ground and excited states 3.088 MeV(1/2+), 3.555 MeV (1/2-), 3.854 MeV (5/2+) of 13С and 1.982 MeV (2+), 3.555 MeV (4+), 3.921 MeV (2+), 4.456 MeV (1-), 5.098 MeV (3-), 5.260 MeV (2+) of 18O. These and the 13С + 18О elastic scattering data taken from the literature at the energies Elab(18O) = 15, 20, 24, 31 MeV and Elab(13С) = 24 MeV were analysed within the optical model and coupled-reaction-channels methods. Sets of 13С + 18О optical potential parameters and their energy dependence were obtained. Contributions of potential scattering and transfer reactions to the elastic and inelastic channels of 13С + 18О scattering were studied. Isotopic differences (effects) in 12, 13С + 16, 18О optical potential parameters were investigated