Analysis of Zeff during H-Mode Regime in the Globus-M2 Tokamak

Abstract

The current configuration of effective ion charge diagnostics at the Globus-M2 facility is described, as well as the results of measuring the \(\left\langle {{{Z}_{{\operatorname{eff} }}}} \right\rangle \) chord-average effective ion charge in a wide range of plasma discharge parameters, both in the ohmic heating regime and the regime with additional heating by neutral particle beams. It was ascertained that under the Globus-M2 conditions, boronization makes it possible to reduce the \(\left\langle {{{Z}_{{\operatorname{eff} }}}} \right\rangle \) charge by 35%. The effect of impurity accumulation in the main plasma volume in the H-mode was confirmed. In shots with desynchronized low-intensity edge localized modes (ELMs), the plasma interaction with plasma-facing materials, including that of the tokamak divertor plates, weakly affects \(\left\langle {{{Z}_{{\operatorname{eff} }}}} \right\rangle \). In the case of development of the ELMs synchronized with the sawtooth oscillations, the \(\left\langle {{{Z}_{{\operatorname{eff} }}}} \right\rangle \) charge considerably increased by a factor of 1.1–3.0, as compared to that in the L-mode.