Edge plasma measurements near the minimum-B anchor cell of GAMMA10 using Langmuir probe and calorimeter arrays

Abstract

Edge plasma diagnostic system equipped in minimum-B anchor cell of the GAMMA10 tandem mirror is described together with the measured results. Several sets of the diagnostic element consisting of a Langmuir probe and a calorimeter are placed in array on the conducting plates installed in the east anchor cell. This diagnostic system is designed to be capable of precisely investigating the spatial dependence of the edge plasma parameters. In typical ion cyclotron range of frequency-heated plasmas, detailed behavior of the edge plasma in the anchor transition regions has been measured by using this system. From these measurements a significant asymmetry of spatial profile was observed in the floating potentials. Heat flow profiles also showed the similar dependence to the probe signals. In this region there exists a strong gradient of the magnetic field strength and the direction of the observed shift is found to be consistent with that of gradient B drift for ions.