Neutral particle analyzer measurements on the SSPX spheromak

Abstract

A neutral particle analyzer is used to measure the time-resolved energy spectrum of neutral hydrogen leaving a spheromak plasma. A gas cell filled with 10-50 mTorr of helium is used to strip electrons from incoming neutral hydrogen, lowering the minimum detectable energy well below that obtained with thin foils. Effective neutral particle temperature is calculated by fitting a Maxwellian energy distribution to the measured energy spectrum above and below approximately 300 eV. A computational model with approximated profiles of plasma density and neutral density is used with the measured neutral hydrogen flux to estimate the ion temperature. Measurement of the power flux due to neutral hydrogen emitted at the measurement location is extended to the whole plasma surface to estimate the total charge exchange power loss from the plasma. The initial results indicate that the charge exchange power loss represents only 2% of the total input gun power during the sustainment phase of the discharge.

Energy confinement and magnetic field generation in the SSPX spheromak

“…The recent addition of a Charge-exchange Neutral Particle Analyzer (CNPA) has allowed measurements of charge exchange power losses and given and estimate of the majority ion temperature [20]. Escaping neutrals are collimated and then stripped by passing through neutral hydrogen.…”

Anisotropic Ion Heating and Tail Generation during Tearing Mode Magnetic Reconnection in a High-Temperature Plasma

“…The flux of neutral atoms is proportional to the product of the probabilities that these events occur. We measure the energy of these charge exchange neutrals with a radially viewing 25-channel analyzer [27]. By using information known about the neutral density profile and the plasma parameters which determine the attenuation (n e , T e , and n i ), information about the ion energy distribution function can be extracted from the neutral spectrum.…”

Determination of Average Ion Temperature of the TVD Tokamak by a Simple Charge Exchange Analyzer Detector

“…In operational energy range of our work this paprameter is approximately constant (0.286) like Ref. [11]. In other tokamaks that use this system for ion temperature measurement resolution depond on particle energy [12].…”