LaBr3(Ce) Detector Based HXR Spectroscopy in Aditya-U Tokamak
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 toka-mak plasma devices in terms of melting and damaging the plasma-facing component (PFC) and thereby reduced the lifetime of 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 (MCA) along with the detector, viewing the whole plasma tangentially along a line of sight terminating on the limiter. The system has total ~2000 channels covering the energy range of 75 keV to few MeV and spectral resolution of ~19.86vkeV at 662 keV, which is lowest among the many scin-tillation based detectors. The typical HX spectra which integrated over the discharge duration. The spectrum has been ob-served in the energy range of around ~ 75 keV to 3 MeV and is continuum in nature.
The spectra is calibrated in energy as well as photon space. The measured spectrum shows peaks within ~ 85 to 150 keV for the analyzed discharges. The peak position of HX spectra peak height is directly related to the maximum population of HX flux, and subsequently can be approximately attributed to RE population, at a particular energy. The HX spectra peak height exhibits an inversely proportional nature with the plasma thermal temperature. Hence, the lower value of energy at peak height at higher thermal Te indicates that the plasma is mostly dominated by lower energy RE.
