Study and Characterization of LiF Thin Film Combined with a Silicon Detector for Neutron Metrology

Abstract

The last decades have seen a lot of work and development on new methods of neutron detection that would replace 3 He gas-based detectors, a device widely used due to its efficiency, which is being phased out due to the scarcity of 3 He gas and its high cost. The work showed that a combination of inorganic materials (Si, 6 LiF) could represent a viable basis for the development of new generations of thermal neutron detectors. This type of device is based on a silicon detector coupled to 6 LiF thin film converters. In this work, a model has been developed based on the fabricated silicon detector with a Schottky surface barrier associated with different thicknesses of 6 LiF films. To study its behavior as a function of the different film thicknesses, the model was characterized using a thermal neutron flux from the source (AmBe-OB26). Preliminary results show that it is possible to measure low-energy neutrons with an average detection efficiency of about 1%, a sensibility of 10 ± 0.1 cps on the 3 H peak, and insensibility to gamma radiation < 10 −6 , with a thin films size of about 2 µm. In this paper, we will present a state of the art of detector design, an evaluation of its characteristics (efficiency, resolution, dead time, proper motion), and a clarification of the influence of other parameters on the shape of the spectrum, highlighting the possibility of improving its detection efficiency to make it high, with a gamma/neutron rejection capability comparable to the 3 He gas detector.