Lanthanum Bromide (LaBr3(Ce)) based hard X-ray spectroscopic diagnostic for the study of runaway electrons at Aditya Tokamak

Abstract

Study of hard X-ray (HX) spectrum is an important tool to understand the runaway electrons (RE) behavior present in the tokamak plasma as these energetic electrons, especially those generated during disruption, represent a major threat to tokamak plasma devices in terms of melting and damaging the plasma-facing component (PFC) and thereby reduced the lifetime of the first wall. A LaBr3(Ce) detector based spectroscopic diagnostic has been set up on the Aditya tokamak to measure the HX spectrum. This diagnostic consists of a photomultiplier tube and multi-channel analyzer along with the detector, viewing the whole plasma tangentially along a line of sight terminating on the limiter. The spectrum has been observed in the energy range of around ∼ 75 keV to 3 MeV and is continuum in nature. The spectrum is having the peaks within ∼ 85–150 keV and the estimated RE temperatures have been found to be in the range of 100–600 keV for the analyzed discharges. This temperature decreases with the increase of the thermal electron temperature of the discharges. The ratios of the estimated confinement time of runaway electron and energy confinement time of thermal particles are mostly inversely proportional to the plasma electron density.