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/q_a, nR/B_t). At the current reversal, I_p = 0 (1/q_a = 0), the plasma density remains finite and the Murakami parameter is nR/B_t = (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