Growth and Scintillation Properties of a New Red-Emitting Scintillator Rb₂HfI₆ for the Fiber-Reading Radiation Monitor

Abstract

A new red-emitting halide scintillator Rb2HfI6 was developed using the vertical Bridgman furnace and quartz ampoule. Under X-ray irradiation, Rb2HfI6 had a broad emission band of around 725 nm. The light output and energy resolution were determined to be ~40000 photons/MeV and ~7.4% (full-width at half-maximum at 662 keV), respectively. Since red photons are transmitted with smaller losses than blue or yellow photons inside an optical fiber, a long-fiber-reading radiation detection system using the high light-output red scintillator can be established for severe or hazardous environments. We fabricated the Rb2HfI6 scintillation crystal and performed the gamma-ray detection test under high-dose irradiation condition from a 60Co source with an activity of ~100 TBq. The dynamic range of the Rb2HfI6 gamma-ray detection with a 20-m optical fiber was evaluated and compared with the previously developed Cs2HfI6 crystal and the conventional deep-red Cr: $\alpha $ -Al2O3 (ruby) scintillator. The gamma-ray doses from ~0.4 to ~1 kSv/h were successfully measured using Rb2HfI6 through the 20-m fiber.