Energy calibration of silicon drift detector - based spectrometer at ADITYA-U

Abstract

The Tokamak plasma start-up is the first process to have a successful Tokamak plasma discharge. Considering the start-up condition, high electric field and neutral density with the absence of flux surfaces an enhanced electron transport to the Plasma-Facing Components (PFC) or the inner vessel wall is expected. Such electron excursion under an applied electric field induces electromagnetic emission, especially in the x-ray region. Such emission is important as it gives vital information about the initial condition of the plasma start-up and the potential for energy loss to the PFC/vessel walls. A Silicon Drift Detector (SDD) based soft x-ray (SX) spectrometer is installed at the ADITYA-U tokamak, operating within the range of 1–30 keV generating a 4 K channel spectrum. The energy calibration, spectra transformation from channel space to the energy space, is a pre-requisite for any spectroscopic measurement. The calibration is performed by natural radioactive sources 241Am, 109Cd, 133Ba, and 55Fe having micro-curie strength. Two-point and multipoint calibrations are applied to the SDD spectra. The results from the two processes establish that the multipoint calibration works well for the identification of the photon energy due to the realization of the detector linearity for a wider band.