Investigation of Temporal Evolution of Hard X-Ray Spectrum from Neon-Seeded Plasma of ADITYA-U Tokamak

The adverse effect associated with runaway electrons (RE) requires the temporal monitoring of the Hard Xray (HX) spectrum produced by RE. This enables us to know the photon flux corresponding to a particular energy of HX in temporal space. A Lanthanum Bromide (LaBr3)-based HX spectrometer system (80 keV ~ 5 MeV) is routinely operated on the ADITYA-U tokamak for monitoring the temporal evolution of the HX spectrum. The temporal evolutions of the HX energy having maximum count and the average RE temperature (RE average energy) have been analyzed for the plasmas injected with neon (Ne) impurity. It has been found that peak energy and average runaway energy reduces significantly after the Ne gas puff and this reduction happens when the electron density rises after the Ne gas puff. The RE temperature values were ~ 620 KeV and 230 KeV before and after the Ne injection, respectively. The spectral shape, in both counts and energy, shrunk drastically, suggesting the reduction of the HX emission after the Ne gas puffing. © 2023 The Japan Society of Plasma Science and Nuclear Fusion Research