Relation Between Electron Density and Temperature of Divertor Simulation Plasma and Upstream Plasma in GAMMA 10/PDX

In GAMMA 10/PDX, the relationship between electron density and temperature of the divertor simulation plasma in the divertor simulation experimental module (D-module) and the density of the upstream plasma has been studied. As the amount of gas (H-2 and Ar) injected into the D-module increases, the line-averaged electron density (n(e)_wp) of the west plug plasma (i.e., upstream plasma) increases due to gas flow from the D-module to the upstream. The electron temperature of the divertor simulation plasma monotonically decreases with increase in n(e)_wp. The electron density of the divertor simulation plasma becomes saturated against increase in n(e)_wp when the plasma is sustained only by the ion cyclotron heating. This may suggest a sign of the beginning of the density roll-over. Additional electron cyclotron heating to the upstream plasma increases the density of both the upstream plasma and the divertor simulation plasma, and the saturated density of the divertor simulation plasma recovers to a linear dependence on n(e)_wp, suggesting an enhanced ionization of neutral gases in the upstream and the D-module.