Experimental study of a boron coated straw detector module at CPHS

Abstract

Large-area position-sensitive thermal neutron detector plays an important role in the small angle neutron scattering (SANS) technique. Considering the shortage of 3He supply, a detector module composed of 64 boron coated straw (BCS) tubes was developed in the present work for the time-of-flight (TOF) SANS instrument that will be deployed on the Compact Pulsed Hadron Source (CPHS) at Tsinghua University. In this paper, 64 straw tubes were tightly packed into 8 rows by 8 columns. A multiplex readout system was utilized to locate the straw tube that has registered a neutron deposition event in the detector module, and to reconstruct the longitudinal position according to the charge division method. Several key aspects, including the pulse height spectrum, the spatial resolution and the position linearity, have been studied using the CPHS neutron beams generated by 3 MeV protons. The results indicated that the detector module can achieve an average axial spatial resolution of 5.8± 0.2 mm with a good position linearity. The neutron detection efficiency of the detector module was simulated with Geant4 code and was found to be larger than 39% for the neutrons at CPHS operated with 13 MeV proton beams in the future. It was concluded that the BCS tubes can be used to build the two-dimensional position-sensitive area detector for the TOF-SANS instrument at CPHS.