Behavior of Non-Thermal Electrons during ECR Pre-Ionization at Aditya Tokamak

Abstract

The non-thermal electrons (NTE) in tokamak plasma have a strong effect over the plasma properties and on the plasma facing components. This establishes an importance of NTE to be studied in both flux and energy space. The NTE was studied for Aditya tokamak by monitoring X-ray spectrum using a Silicon Drift Detector (SDD) based X-ray spectroscopic diagnostic for the ECR pre-ionization experiments. The spectra shows X-ray line radiation band on top of the bremsstrahlung. Line radiation is primarily the combination of multiple characteristics lines existed between 5 keV to 7 keV and mostly associated with multiple ionized states of iron, tokamak wall material. This is likely due to the interaction between the NTE, generated during ECR pre-ionization experiment, with the stainless steel vessel wall of the Aditya Tokamak. The behavior of NTE was studied as a function of vertical field and pre-filled pressure. With the application of vertical field, energy carried by the NTE is reduced due to higher vertical drift velocity in comparison to the case of without one. Significant reduction of the X-ray line radiation strength with higher pre-filled pressure also indicates the reduction of NTE due to the enhanced electron neutral collision.