ABSTRACT
The γ(3) setup has been designed as a versatile, high sensitivity spectrometry platform. State-of-the art techniques have been implemented to reduce its background to minimum level even though the system is installed at ground level. The shield design and background performance of the setup are presented. The spectrometer is composed of three identical HPGe detectors for high detection efficiency or coincidence measurement and can accommodate several sample geometries. Its shield includes three layers of increasing purity lead, a cosmic veto, an inner borated polyethylene layer, and a radon-free gas injection system. The spectrometer normalized background count rate is 4.4 counts per minutekgGe(-1) (in the 40-2500keV energy range). Its background characteristics, cosmic veto efficiency, and radon-free gas injection performances are discussed.
ABSTRACT
The present work reports on a long-term analysis of the performances of the (95)Zr/(95)Nb chronometer for dating a nuclear event. Taking benefit of a recent Profiency Test Exercise, a sample containing a standardized mixture of fission products has been measured repeatedly with a low background HPGe spectrometer during a period extending up to one year with the aim of assessing the accuracy of the various zero-time determinations. Evaluation of the uncertainties associated to these evaluations was performed using a Monte Carlo approach. Input parameters sensitivity has been investigated, especially the influence of the (95m)Nb decay branch. The (95)Zr/(95)Nb chronometer was found to be accurate for zero-time determination within one day and one week for a decay of 3 months and 10 months respectively. Sub-day uncertainties are achievable for a two months old sample whereas sub-week uncertainties are reached after a decay of six months. Limitations of the technique for dating a real event are investigated.
