Energy measurement and fragment identification using digital signals from partially depleted Si detectors

A study of identification properties of a Si-Si DE-E telescope exploiting an underdepleted residual-energy detector has been performed. Five different bias voltages have been used, one corresponding to full depletion, the others associated with a depleted layer ranging from 90% to 60% of the detector thickness. Fragment identification has been performed using either the DE-E technique or Pulse Shape Analysis (PSA). Both detectors are reverse mounted: particles enter from the low field side, to enhance the PSA performance. The achieved charge and mass resolution has been quantitatively expressed using a Figure of Merit (FoM). Charge collection efficiency has been evaluated and the possibility of energy calibration corrections has been considered. We find that the DE-E performance is not affected by incomplete depletion even when only 60% of the wafer is depleted. Isotopic separation capability improves at lower bias voltages with respect to full depletion, though charge identification thresholds are higher than at full depletion. Good isotopic identification via PSA has been obtained from a partially depleted detector whose doping uniformity is not good enough for isotopic identification at full depletion.Comment: 13 pages, 10 figures 5 tables; submitted to European Physical Journal

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

Quasiprojectile breakup and isospin equilibration at Fermi energies: an indication of longer projectile-target contact times?

An investigation of the quasiprojectile breakup channel in semiperipheral and peripheral collisions of $^{58,64}$Ni+$^{58,64}$Ni at 32 and 52 MeV/nucleon is presented. Data have been acquired in the first experimental campaign of the INDRA-FAZIA apparatus in GANIL. The effect of isospin diffusion between projectile and target in the two asymmetric reactions has been highlighted by means of the isospin transport ratio technique, exploiting the neutron-to-proton ratio of the quasiprojectile reconstructed from the two breakup fragments. We found evidence that, for the same reaction centrality, a higher degree of relaxation of the initial isospin imbalance is achieved in the breakup channel with respect to the more populated binary output, possibly indicating the indirect selection of specific dynamical features. We have proposed an interpretation based on different average projectile-target contact times related to the two exit channels under investigation, with a longer interaction for the breakup channel. The time information has been extracted from AMD simulations of the studied systems coupled to GEMINI++: the model calculations support the hypothesis hereby presented

From light to heavy nuclear systems, production and decay of fragments studied with powerful arrays

Reactions between heavy-ions at various energy regimes produce many nuclear fragments which can be populated in highly excited states. The study of these fragments, detected at the end of their particle decay, is important to investigate nuclear forces and structure effects. In recent years there have been many efforts to extend these studies towards the drip-lines, i.e. to systems far from the β-stability valley, by using accelerated radioactive beams. The development of such infrastructures is accompanied by the development of more powerful detectors and associated electronics, capable to identify ions with very different sizes and kinetic energies. Here we give two examples which show how advanced arrays can contribute to the studies on nuclear phenomena. The examples come from the European FAZIA collaboration and from recent campaigns with the GARFIELD apparatus, the latter in operation at the INFN Legnaro Laboratory (Italy) where the SPES RIB facility is under construction

Double sided strip monolithic silicon E-ΔE telescope produced by Quasi-Selective Epitaxy

The problem of cross-talks (induction of signals) from the E detector to the deltaEdetector in a monolithic E-deltaE telescope was solved by the appropriate geometry ofthe telescope. It was shown by a solution of the telegraphic equation describing thetime-dependent evolution of induced signals in the deltaE detector RC line, that forlong and narrow monolithic telescopes the induced signals (cross-talks) were suppressed.These results are experimentally supported by measurements of alpha particleswith the circular monolithic E-deltaE telescope. When alpha particles were measured atthe telescope edge, the induced signal (cross-talk) was decreased. For alpha particlesmeasured at the center of the telescope the amplitude of cross-talk was bigger.Applying these results we have designed a new type of device based on the n+ - n -p+ - n - n+ structures: double-sided strip monolithic silicon E-deltaE telescope. Thedevice is similar to the Radeka double sided strip detector, however, an introducedp+ type buried grounded separating layer isolates the (upper) deltaE strip detectorfrom the (bottom) E strip detector of the telescope