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New methods to identify low energy 3He with Silicon-based detectors

The identification of low energy mass-3 nuclei is crucial for the study of nuclear structure via transfer reactions. For example, one nucleon transfer like (d,3He) and (d,t) give detailed information on the proton and neutron orbitals respectively. The paper gives a review of the present methods used to detect and identify mass-3 particles. Time of flight is often used but does not allow to disentangle between 3He and tritons. The addition of thin Silicon detectors (20 um) gives the identification by the DeltaE-E technique in two successives Silicon detectors. However thin Silicon detectors are limited to a number of physics cases and very difficult to handle.

The GRIT team has performed an experiment at ALTO with a pulsed deuteron beam impinging on a mylar target to study new methods for the discrimination of mass-3 nuclei. The experimental set-up was composed of a highly segmented Silicon detector very uniform in resisitivity, read by a premplifier that gives charge and current (PACI) designed at IPN coupled with the Wavecatcher digitizer designed by LAL. The identification of mass-3 nuclei is based on pulse shape analysis (PSA) using the amplitude of the current signal (Imax) and the amplitude of the charge (i.e. energy).

Another method relying on a numerical time of flight between the RF from the beam registered in Wavecatcher et a threshold set at 10% on the charge (resp. current) signal has been investigated. It also gives very good discirmination of mass-3 nuclei.

These two later methods will be implemented in the GRIT project that aims at building a 4pi Silicon detector to be coupled with the state-of-the-art gamma-ray arrays like AGATA. The identification of low energy nuclei in GRIT will rely on PSA and time of flight for the particles with the lowest energies.

lien :

See online : Nuclear Inst. and Methods in Physics Research, A 908 (2018) 250–255



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