Study of Ion Temperature Relaxation in GDT During Neutral Beam Heating by a Rutherford Scattering Diagnostic

The neutral beam scattering diagnostic¹ has been developed to measure the ion temperature of the target plasma in the Gas-Dynamic Trap (GDT) experiment. In the GDT, the target plasma density was about 10¹⁴ cm⁻³, the ion temperature was estimated from diamagnetic loops data combined with electron temperature obtained by Thompson scattering to be maximally ≈100 eV. The developed special diagnostic based on small angle scattering of neutral beam particles enables to perform more accurate measurements of the ion temperature. The beam of helium atoms is injected at the angle of 8° to the observation direction. The injection energy is 10 keV, the total equivalent beam current is 1A. The neutral particles are scattered on the plasma ions and enter the 45″ electrostatic analyzer. The ion temperature was inferred from the measured width of the energy distribution function of the scattered particles

This diagnostic was applied to measure temporal variation of the ion temperature during neutral beam heating. The electron temperature was simultaneously measured by Thomson scattering of a ruby laser light. The data will be used to estimate the energy balance of the ion component of the target plasma during neutral beam heating.