A Method for Plasma Electron Temperature Evaluation for GOL-NB facility

TL;DR

This paper introduces a spectral line ratio method to measure plasma electron temperature in the GOL-NB facility, utilizing Doppler shifts of fast hydrogen atoms with different energies for accurate diagnostics.

Contribution

It presents a novel spectral line ratio technique based on Doppler shifts of fast atoms to determine plasma electron temperature in GOL-NB.

Findings

Method effective up to 40 eV electron temperature.

Spectral line ratios depend on plasma temperature.

Achieves 20 eV measurement accuracy with precise intensity ratio measurements.

Abstract

A new method for measuring the electron temperature of the plasma in GOL-NB facility is proposed. The proposed method is based on measuring the ratio of intensities of spectral lines emitted by fast atoms injected into the plasma. The beams of fast hydrogen atoms used for plasma heating or diagnostics contain atoms with full energy as well as atoms with fractional energies (E/2, E/3, E/18), which arise from the dissociation of molecular ions H+2, H+3, H2O+. Spectral lines of atoms with different energies (especially Ha) can be resolved due to Doppler shift caused by differences in atom velocities. For low-energy atoms, excitation occurs due to collisions with thermal electrons, while for high-energy atoms, collision processes with plasma ions are essential. Therefore, the intensity ratio of line fractions with different energies depends on the electronic temperature of the plasma and can be used for its measurement. At a beam energy of 24 keV, the method can be used to measure electronic temperatures up to 40 eV, which is of interest for experiments on the GOL-NB facility. To measure the temperature with an accuracy of 20 eV, it is necessary to measure the intensity ratio of lines with percentage precision and also measure the same precision of attenuation of the neutral beam passing through the plasma.