Hard X-ray Measurement with LaBr 3 Detector for the Study of Runaway Electrons on the HL-2M Tokamak

AbstractRunaway electrons (REs) generated during disruptions pose a significant safety threat to tokamaks, as they can melt and damage the plasma-facing components (PFCs). Therefore, studying RE behavior is crucial for fusion devices. The interaction between REs and the first wall/PFCs results in the emission of high-energy X-rays, known as bremsstrahlung. To investigate RE behavior, it is necessary to quantitatively evaluate the emission of hard X-rays. A real-time hard X-ray spectrometer, utilizing a LaBr3 detector, has been successfully developed for studying REs on the HL-2M tokamak. This spectrometer has a counting rate capability reaching 3 MHz, with an energy resolution of 3.3% at 662 keV (137Cs). The time resolution for energy spectrums is as short as 1 ms. During the HL-2M discharge, observations were made on the hard X-ray energy spectrum, and by analyzing the spectrum within the energy range of 250 keV to 750 keV, the temperature of the corresponding REs was deduced.Keywords: HL-2M tokamakhard X-ray spectrometerLaBr3 detector AcknowledgmentsIt is a pleasure to acknowledge the assistance from the Neutron Flux Monitor team of the Southwestern Institute of Physics.Disclosure StatementNo potential conflict of interest was reported by the authors.Additional informationFundingThis work is supported by the National MCF Energy Research and Development Program of the Ministry of Science and Technology of China [grant no. 2022YFE03080003].