A Simple Method for Rise-Time Discrimination of Slow Pulses from Charge-Sensitive Preamplifiers

Performance of a simple method of particle identification via pulse rise time discrimination is demonstrated for slow pulses from charge-sensitive preamplifiers with rise times ranging from 10 ns to 500 ns. The method is based on a comparison of the amplitudes of two pulses, derived from each raw preamplifier pulse with two amplifiers with largely differing shaping times, using a fast peak-sensing ADC. For the injected charges corresponding to energy deposits in silicon detectors of a few tens of MeV, a rise time resolution of the order of 1 ns can be achieved. The identification method is applicable in particle experiments involving large-area silicon detectors, but is easily adaptable to other detectors with a response corresponding to significantly different pulse rise times for different particle species.Comment: 10 pages, 7 figure

Influence of the Coulomb Interaction on the Chemical Equilibrium of Nuclear Systems at Break-Up

The importance of a Coulomb correction to the formalism proposed by Albergo et al. for determining the temperatures of nuclear systems at break-up and the ensities of free nucleon gases is discussed. While the proposed correction has no effect on the temperatures extracted based on double isotope ratios, it becomes non-negligible when such temperatures or densities of free nucleon gases are extracted based on multiplicities of heavier fragments of different atomic numbers

Dissipative orbiting in ^{136}Xe+^{209}Bi reactions at 28 and 62 AMeV

Correlations between the energy, charge and the deflection angle of the projectile-like fragments were studied for the ^{136}Xe + ^{209}Bi reaction at E∕A = 28 and 62 MeV. These correlations are seen to exhibit features characteristic of dissipative orbiting, commonly found at bombarding energies of a few MeV/nucleon above the interaction barrier, but also reported in the Fermi-energy domain. It was found, that in the studied bombarding energy range, the reaction cross section is still dominated by the dissipative binary reactions of well defined projectile- and target-like fragments

Structure effects in Ne-20+Pb-208 quasi-elastic scattering

Preliminary results of an analysis of experiments devoted to a study of the sensitivity of the 20Ne + 208Pb quasi-elastic angular distributions at two near-barrier energies and the previously measured corresponding barrier distribution to the value of the nuclear quadrupole deformation length of 20Ne are reported

Production of neutron-rich nuclei in fragmentation reactions of 132Sn projectiles at relativistic energies

The fragmentation of neutron-rich 132Sn nuclei produced in the fission of 238U projectiles at 950 MeV/u has been investigated at the FRagment Separator (FRS) at GSI. This work represents the first investigation of fragmentation of medium-mass radioactive projectiles with a large neutron excess. The measured production cross sections of the residual nuclei are relevant for the possible use of a two-stage reaction scheme (fission+fragmentation) for the production of extremely neutron-rich medium-mass nuclei in future rare-ion-beam facilities. Moreover, the new data will provide a better understanding of the "memory" effect in fragmentation reactions.Comment: 5 pages, 3 figure

Projected Quasi-particle Perturbation theory

The BCS and/or HFB theories are extended by treating the effect of four quasi-particle states perturbatively. The approach is tested on the pairing hamiltonian, showing that it combines the advantage of standard perturbation theory valid at low pairing strength and of non-perturbative approaches breaking particle number valid at higher pairing strength. Including the restoration of particle number, further improves the description of pairing correlation. In the presented test, the agreement between the exact solution and the combined perturbative + projection is almost perfect. The proposed method scales friendly when the number of particles increases and provides a simple alternative to other more complicated approaches

Neutron-rich fragments produced by in-flight fission of U-238

The production cross sections of neutron-rich fission residues in reactions induced by U-238 projectiles at 950A MeV impinging on Pb and Be targets are investigated at the Fragment Separator at GSI. These two targets allow us to investigate fission processes induced by two reaction mechanisms, Coulomb and nuclear excitations, and to study the role of these mechanisms in the neutron excess of the final fragments.Peer reviewe

Are the weak channels really weak?

The transfer probabilities for 20Ne + 90Zr and 20Ne + 92Zr at energies near the Coulomb barrier were measured. This quantity turned out to be very similar for both Zr isotopes and does not explain the observed differences in the barrier height distributions for these systems

Systematic reduction of the proton-removal cross section in neutron-rich medium-mass nuclei

Single-neutron and single-proton removal cross sections have been measured for medium-mass neutron-rich nuclei around Z=50 and energies around 1000A MeV using the FRagment Separator (FRS) at GSI. The measured cross sections confirm the relative low values of the proton-removal cross sections, observed since a long time ago and not yet understood. Model calculations considering the knock-out process together with initial- and final-state interactions describe the measured neutron-removal cross sections. Proton-removal cross sections are, however, significantly over-predicted by the same calculations. The observed difference can be explained to a large extent by the knock-out of short-range correlated nucleons from dominant neutron-proton pairs in neutron-rich nuclei. © 2020 The Author(s)Peer reviewe

Systematic Investigation of Nucleon Knockout around 132Sn

Peer reviewe