Tangentially viewing hard X-ray imaging system and its measurement simulation on the HL-2M tokamak

A tangentially viewing Hard X-ray Real-Time Imaging (HXR-RTI) system and its measurement simulation on the HL-2M tokamak are presented. The HXR-RTI system mainly consists of a CsI:Tl scintillator crystal, a pinhole mechanism and a high-speed camera. When the CsI:Tl crystal is struck by the X-ray photons, certain wavelengths of visible or near-visible photons will be scintillated, which could be collected by the lens and imaged by the high-speed camera. This system can measure HXR with energy up to 300 keV, spatial resolution of less than 10 mm, and temporal resolution of several tens of microseconds. To understand the emission profile, we have developed a Geant4 model. The simulation results confirm that the spatial asymmetry will eventually lead to radiation asymmetry distribution. This system is designed for real-time exhibition of hard X-ray radiations from fast electron forward bremsstrahlung and will be used to study the dynamics of fast electrons.