Measurement of ion temperature and density profiles with a time-of-flight type neutral-particle analyzer

Abstract

High beta plasmas in the anchor cell of the GAMMA 10 tandem mirror are formed by using a fundamental ion cyclotron resonance heating. Because the closed resonance surface exists near the midplane of the anchor cell, strongly peaked profile of the plasma pressure will be formed. To measure the axial profiles of the ion temperature and density, a time-of-flight type neutral-particle analyzer (TOF-NPA) has been developed. TOF-NPA can detect neutral particles and photons separately at the same time. The ion temperature and density have been evaluated from the particle and photon signals, respectively. The peaked profile of the ion temperature within the closed resonance surface has been confirmed.

Contemporary Instrumentation and Application of Charge Exchange Neutral Particle Diagnostics in Magnetic Fusion Experiments

“…Electrostatic acceleration of ions scattered by the stripping foil provided focusing of the ions before the E||B dispersion which leads an increase of the detection efficiency in the lower energy range E < 1 keV. After the first application at PLT [67], similar systems have been used on ASDEX [68,69], JFT-2M [70], RFX [71,72], Alcator C-Mod [73], GAMMA-10 [74] and TORTUR [75,76]. About half of these systems applied a standard chopper plate as depicted in The RFX reversed field pinch is equipped with two low-energy TOF NPAs [72], one viewing vertically and one horizontally.…”