Development of Z_eff diagnostic system on the Globus-M (M2) tokamak and the first experimental results

Studying the behavior of effective ion charge Z_eff, which indicates the degree of pollution of plasma and can provide valuable information about many processes taking place in plasma, mechanisms of the releasing impurities, transport, etc is of great interest. This paper describes the development of the Z_eff diagnostic system for the Globus-M2 tokamak. The effective ion charge is determined on the basis of measurements of the bremsstrahlung intensity and Thomson scattering data—T_e and n_e profiles. The results of the first Z_eff measurements obtained for several discharges on the Globus-M tokamak are presented in this paper. The results have been validated by simulation using the ASTRA transport code for the same discharges, and it has demonstrated a good agreement with the experimental results.