Validation of the plasma-wall self-organization model for density limit in ECRH-assisted start-up of Ohmic discharges on J-TEXT

Abstract

A recently developed plasma-wall self-organization (PWSO) model [D.F. Escande et al 2022 Nucl. Fusion 62 026001] predicts a significantly enhanced density limit, which may be attainable in tokamaks with ECRH-assisted ohmic start-up and sufficiently high initial neutral density. Experiments have been conducted on J-TEXT to validate such a density limit scenario based on this model. Experimental results demonstrate that increasing the pre-filled gas pressure or ECRH power during the start-up phase can help effectively enhance plasma purity and raise the density limit at the flat-top phase. The experimental data shows that density limit increases by a ratio 0.76/0.6 ≈ 1.27 for a decrease by a factor 0.13/0.33 ≈ 0.4 in CIII radiation.