Development of 3 He-filled linear position-sensitive detector for neutron scattering instruments at CSNS

Background Helium-3-filled linear position-sensitive detectors (LPSDs) have been widely applied to neutron scattering instruments in recent decades owing to the high detection efficiency, the excellent neutron/gamma discrimination, and the ability to construct the detector with large area coverage. More than 65% of neutron instruments at the China Spallation Neutron Source (CSNS) require 3 He LPSDs for the building of the detector system. The detector of a neutron scattering instrument is normally an array detector composed of a large number of 3 He LPSDs. However, no appropriate substitute detector is available for the 3 He LPSD for operation over a short period, and its specifications need to be customized to satisfy the requirements of different instruments. This necessitates the development of 3 He LPSDs with different specifications for building and upgrading the detectors of neutron scattering instruments at CSNS. Purpose To meet the general requirements specified by the neutron instruments at CSNS, a 3 He LPSD was developed and its performances were investigated by using the neutron beam. Methods The neutron beam experiments for this 3 He LPSD, including measurements of counting rate plateau curve, position calibration, and position resolution along the tube path, were carried out at the beamline-20 of CSNS. To evaluate its performance in the instrument operation, a detector module made of this 3 He LPSD has been installed in the multi-physics instrument (MPI), and the comparison test with the commercial 3 He LPSD has been conducted at neutron scattering experiments. Results and conclusion The experimental measurements for this 3 He LPSD based on the neutron beam showed that it satisfies the requirements for use in neutron scattering instruments. It reaches a plateau slope of 2.6%/100 V with a plateau range from 1750 to 1950 V and attained a minimal position resolution of 5.3 mm (FWHM), superior to the one achieved by the commercial 3 He LPSD. In addition, this 3 He LPSD detector module applied to the MPI has been working steadily for half of year and is available for use in experiments. These results provide a sound basis for the subsequent construction and upgradation of the detector of neutron scattering instruments at CSNS.