Abstrakt
Understanding of disruptions plays an important role for design of future fusion devices as they induce large thermal and mechanical loads on vacuum vessel [Wesson, 1987; Ikeda et al., 2007]. Statistical analysis of set of discharges during the period August-December 2017 was performed in order to improve our knowledge of disruptions on the COMPASS tokamak.
About 58% of COMPASS plasma discharges are disruptive which provides a good opportunity for disruption studies. Hugill diagrams for COMPASS operational space and disruption rate are presented.
Tendency to disrupt increases when safety factor q95 and plasma density density n-e approach current and Greenwald limits. COMPASS is equipped with magnetic diagnostics, which allow measurements of the plasma current at five toroidal locations.
Therefore plasma current asymmetry can be studied. Asymmetrical disruptions parameters such as magnitude, frequency, number of rotations and duration of asymmetry are analyzed within the contribution.
Plasma current asymmetries at COMPASS exhibit similar behavior as at JET. Ambiguity of plasma current measurements due to magnetic diagnostics position with respect to in-vessel components is discussed.
Study of asymmetry magnitude dependence on disruption direction does not prove the assumption that the asymmetry might be caused by the short-circuit between the limiter tiles.