Energy and density measurements of sloshing ions in tandem-mirror-experiment upgrade using solid-state probe techniques

Abstract

The energy and flux of charge-exchange neutrals from the sloshing ions in the endplug of tandem-mirror-experiment upgrade were measured using solid-state probes. An average energy of the sloshing ions of 6 keV was inferred from the depth profile of deuterium implanted in a silicon sample exposed to the charge-exchange neutrals. A bounce-averaged Fokker–Planck code was used to calculate the sloshing-ion energy distribution. The calculated depth profile of deuterium in the silicon sample resulting from this energy distribution is in good agreement with the measured profile. Carbon resistance probes were used to measure the charge-exchange flux from which the central chord sloshing-ion line density was inferred. The line density of particles with energies>2 keV was deduced to account for 60% of the total plasma line density in the endplug. By folding the sloshing-ion line density into the diamagnetic loop data, it was shown that the 1/e radial extent of the sloshing ions remained relatively constant from shot to shot at 14 cm.