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, nR/Bt). At the current reversal, Ip = 0 (1/qa = 0), the plasma density remains finite and the Murakami parameter is nR/Bt = (0.66 ± 0.22) × 1018m-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