Development of high-sensitivity neutron detectors and measurements at the TPS LINAC

Abstract

TPS LINAC is essentially concatenated by three consecutive sections of linear accelerators with a nominal output of 2.25 W (150 MeV, 5 nC, 3 Hz) electron beam. A 15 m long transfer line used to guide accelerated electrons from the LINAC outlet to the beam dump. For ensuring radiation safety of personnel around the area, gamma-ray and neutron dose rates outside the LINAC room were repeatedly measured and reviewed during the commissioning. If all the accelerated electrons are perfectly dumped as we wish, radiation dose rates outside the shielding should be as low as comparable to the natural background level. To be able to clearly identify radiation changes above background levels and perform reliable dose rate measurements, high-sensitivity radiation detectors are necessary. This paper presents the design and characteristics of these detectors and a data analysis of the measured results taken during a full-power LINAC operation. NSRRC is now constructing its second light source facility called Taiwan Photon Source (TPS) to meet the increasing demand for brighter synchrotron X-ray source. Focusing on a low-emittance design, the TPS will become one of the brightest synchrotron light sources in the world. The accelerator system consists of a 3.0-GeV electron storage ring with a circumference of 518.4 m, a concentric booster synchrotron with a circumference of 496.8 m, and a pre-injector of 150-MeV electron LINAC. Due to some delay of the TPS civil construction, NSRRC has built a simple rectangular shielding room made of 1 m thick concrete for the assembly and acceptance test of the outsourcing LINAC.