Spectroscopic diagnostics on the VX-50

We have used hydrogen spectra to estimate electron temperature on VX-50, a 20 kW helicon plasma with a 20 KW ICRF acceleration section, using absolutely calibrated spectroscopic measurements of the Balmer series. The time evolution of the hydrogen spectra shows a transition from an ionizing plasma to a recombining plasma and back during a shot. We used a collisional radiative mode to estimate electron temperatures along with electron density measurements from an interferometer.