Investigation of atomic and molecular processes in ADITYA and ADITYA-U tokamak plasmas

We report the analysis of experimental discharges of ADITYA and ADITYA-U tokamak by a thorough understanding of various atomic and molecular process. In these tokamaks, the fuel neutrals enter into the plasma from limiter surface and interact with plasma particles. In addition to that, various impurities such as Carbon, Oxygen can also be present inside the tokamak plasmas. As a result, different atomic and molecular processes occur when these neutrals interact with either plasma charge particles and/or impurities. Due to the atomic and molecular reactions, the radiation comes out from the plasma, which can be measured by spectroscopic means. Hence, the measurement of wavelength spectrum provides a tool to obtain the information about the species present in the plasma. In this work, the impurity transport behaviour is studied using impurity transport code, STRAHL. The diffusion coefficients are estimated along the minor radius of ADITYA using Oxygen impurity transport, which are found higher compare to that of neo-classical values. The density distributions of different charge state of Carbon are also estimated from STRAHL code to study the behaviour of radial profile of Hα emissivity profile. The behaviour of neutral particle is then studied in details after successfully implementing the limiter geometry in neutral particle transport code DEGAS2. (author)