(updated: october 2012)
experiment: E556/E556a at GANIL (78Kr fragmentation)
contact@CENBG: J. Giovinazzo
Date: september 2008 (E556); october 2010 (E556a)
Purpose of the experiment
This experiment is part of a campaign that aims to determine the Gamow-Teller (GT) strength distribution in the beta-decay of TZ = -1 and -2 isotopes, and to study the mirror symmetry. The TZ = +1 and +2 nuclei GT strength has been measured via charge exchange reaction, and for TZ = -1 and -2, the GT strength is studied via decay spectroscopy.
The purpose of E556 experiment was to measure both 58Zn (TZ = -1) and 56Zn (TZ = -2), but the production rate for this latter was far too low, and the experiment has been redone (E556a).
The exotic isotopes are produced by quasi-fragmentation of a 58Ni beam, selected with the LISE3 spectrometer, and implanted in a standard silicon telescope device surrounded with a germanium array (fig. 1).
The decay events are triggered by a charged particle signal in the implantation DSSSD, and correlated to ions implanted in the same pixel.
Figure 1: Experimental setup: the ions selected by the LISE3 spectrometer are implanted in the DSSSD. The identification of ions is performed with energy loss and time-of-flight measurements with the silicon telescope. The silicon detectors also register the charged particles (betas and protons) energy in the decay after implantation, and the germanium detectors surrounding the telescope measure the gamma-rays in coincidence with the decay events.
The identification plots (fig. 2) shows the implantation and online identification of ions for the setup optimised on 56Zn production. The contours on various isotopes allowed for an offline analysis of decay spectra, as presented in figure 3 in teh case of 56Zn decay.
Figure 2: Identification matrix for 56Zn setting.
Figure 3: 56Zn decay spectra: (1) time of decay event after ion implantation: all decay events in black, with strip energy above 1000 (coder units); (2) decay energy in the DSSSD (each peak corresponds to a proton transition after beta decay): raw spectrum in black, with background subtraction in red.
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