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), nRBAR/B(t)). At the current reversal, I(p) = 0 (1/q(a) = 0), the plasma density remains finite and the Murakami parameter is nRBAR/B(t) = (0.66 +/- 0.22) x 10(18) m-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.