Anomalous ion temperature and plasma resistance due to MHD fluctuations in REPUTE-1 reversed field pinch plasmas

Abstract

Anomalous ion temperature and plasma resistance have been studied in reversed Held pinch discharges of the REPUTE-1 device. The ion temperature measured by Doppler broadening of carbon V (2271 Å) has been observed to be anomalously high in hydrogen discharges with low electron density (n̄e ≤ 0.5 × 1014 cm−3); also the plasma resistance is anomalously large in these discharges. The ion temperature and the plasma resistance are shown to increase with the MHD fluctuation level. The profiles of ion temperature and soft X-ray emission have been found to be more peaked in the lower electron density regime than in the higher one. A high ion temperature and a large plasma resistance are observed simultaneously when the profile of the soft X-ray emission Isx is more peaked. If Isx is mainly affected by the electron temperature profile(Isx ∝ ne2Te3.5),the experimental observations are in qualitative agreement with a calculation showing that the heating power of ions is larger when the electron temperature has a more peaked profile in a magnetic configuration.