Assessment of the Capability for Vetoing Beta-Decay Events in the Lundium Decay Station

Abstract: Alpha decay spectroscopy using the latest and most sensitive detector setup as well as fast sampling read-out electronics has become very important for discovery and analysis of short-lived nuclei created in collision experiments in the laboratory. The Nuclear Structure Group in Lund is currently developing the Lundium Decay Station for use in comprehensive nuclear spectroscopy of decays for rare isotopes, particularly in the heavy & superheavy region. In this thesis work, the performance of the veto detector in the Lundium decay station is investigated to observe how well the implantation detector can distinguish low energy signals of to-be-reconstructed alpha particles from beta particles passing through. To investigate this, a Bi-207 source was used to radiate electrons on an implantation plus veto detector, back-to-back, setup at a distance very close to the face of the implantation detector. Data on the number and position of energy depositions (hits) recorded on both of them are analysed and used to build distributions of the electrons spread on the veto detector while ‘gating’ on pixels hit on the implantation detector. This very important finding allows one to determine how far apart hits on the two detectors can be for a beta particle passing through and still be considered to be from that same particle; this is becoming increasingly important as more (and new) fine structure of the alpha decays is investigated. The standard deviations calculated for the veto detector hit distributions, that can then be used to set electron hits apart in actual experiments to a suitable confidence level, was found to be about 4 mm.