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Decay studies around 69Kr and 65Se (E538) - 2008

(updated: october 2012)


experiment: E538 at GANIL (78Kr fragmentation)
contact@CENBG: J. Giovinazzo

Date: september 2008


  1. Argonne National Laboratory (USA)
  2. Centre d’Etudes Nucléaires de Bordeaux-Gradignan (France)
  3. Grand Accélérateur National d’Ions Lourds, Caen (France)

Purpose of the experiment

This experiment aim to produce isotopes at the proton drip-line in the region of 65Se and 69Kr. This region is interesting for various aspects, such as decay spectroscopy at the drip-line, CVC test from TZ = 0 nuclei decay, test of isospin symmetry, ...

The beta decay of 65Se and 69Kr populates the proton-unbound nuclei 65As and 69Br, and beta-proton spectroscopy is a unique access to the structure of such unbound isotopes. This information is also important as the nucleosynthesis rp-process goes throught this mass region, and 64Ge and 68Se are possible waiting points for this process.

During the experiment, we also looked for the existence of 68Kr, in the context of the search for new candidates for the ground-state 2-proton radioactivity. But no event corresponding to a 68Kr implantation could be identified.

Experimental setup

The exotic isotopes are produced by fragmentation of a 78Kr 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.

Typical results

Figure 2: Example of identification plot: time-of-flight versus energy loss. The colors correspond to identification precision.

Figure 3: 65Se decay. (1) half-life measurement; (2) proton energy distribution; (3) preliminary decay scheme.

Figure 3: 69Kr decay. (1) half-life measurement; (2) proton energy distribution; (3) preliminary decay scheme.