Performances of digital acquisition for a BC501A detector system

Abstract

IRSN uses a BC501A detector system to determine reference fluence energy distribution of neutron fields in the energy range between 1 and 20 MeV. The data acquisition chain associated to this detector consists of NIM standard electronic units which makes the system bulky and not easily movable. Recent developments in the field of numerical electronics offer the opportunity to use digital acquisition system which is compact, more convenient for measurements at workplaces and allows numerical data treatment. Within the framework of collaboration between IRSN and the technological university of Cachan a new digital acquisition system was developed and tested with the BC501A. An Acqiris digital card with a data recording capability of 8 bits range at 4 GHz on two channels was chosen. Specific electronic and signal processing were developed to allow gain stability with high voltage feedback, and to obtain energy information with neutron/ discrimination. The performances (energy resolution, threshold values, dead time and count rate) of the digital acquisition prototype were then compared with those of standard analogical acquisition. In the present state, the comparison results were not satisfying for metrology applications, but the use of new digital cards with 10 bits range is awaited to be fully competitive.