Thin Beta-ray Detectors using Plastic Scintillator Combined with Wavelength-shifting Fibers for Surface Contamination Monitoring

Abstract

A thin β-ray detector for surface contamination monitoring has been newly developed. This detector, which we call a “wavelength-shifting” β-ray detector, consists of a thin square plastic scintillator plus wavelength-shifting fibers (WLSFs) to collect scintillation photons. The WLSFs are attached to opposite edges of the scintillator, where they convert highly concentrated scintillation photons into fluorescence. The fluorescent photons can either be detected directly at the ends of the WLSFs or through transparent optical fibers by small photo-multiplier tubes (PMTs). This design provides a thin detector profile while offering good β-ray detection performance.We first carry out a theoretical evaluation of the light output of this design. Then we describe verification tests aimed at device evaluation, including some performance tests using trial-manufactured detectors. The results demonstrate that the new design offers good sensitivity and uniformity, and that the required detection limit for surface contamination monitoring is achieved. Finally, we confirm that the newly developed detectors are suitable for practical application.