Investigation of Light Transmission Efficiency in ITER Hard X-Ray Monitor

Abstract

A Hard X-ray monitor (HXRM) diagnostic system is being designed for ITER tokamak and will be utilized to detect runaway electrons for the safe operation of the tokamak. Runaway electrons produce X-ray photons by means of thick target and/or thin target bremsstrahlung emission process. In this diagnostic measurement system, the X-ray photons interact with scintillator detector volume and generate secondary UV-photons by luminescence. These UV-photons from the scintillator-crystal guided through the optics and detected by photomultiplier tubes. The light collection efficiency from the scintillator-crystals and light transmission efficiency of the optics determines the detectable energy range of X-rays and energy resolution. In this letter, we perform ray-tracing simulations of the luminescence to optical fiber bundle to assess light collection efficiency from the scintillator-crystal and show the effect on the total light coupling efficiency of the system.