Plasma density at the current reversal in the STOR-1M tokamak with AC operation

The plasma density behaviour in the STOR-1M tokamak with alternating current (AC) operation is described using the Murakami-Hugill diagram (1/qa, n-barR/Bt). At the current reversal, Ip=0 (1/qa=0), the plasma density remains finite and the Murakami parameter is n-barR/Bt=(0.66±0.22)x1018m-2·T-1. Gas puffing before the current reversal does not noticeably increase the plasma density at the current reversal, but allows AC operation with larger currents and improves its reproducibility. A qualitative explanation for the finite plasma density at the current reversal is given on the basis of a short circuit effect by the limiter. (author). 18 refs, 10 figs