The energy balance of divertor discharges in the PDX tokamak

The energy balance of divertor discharges in the PDX tokamak has been studied as a function of the divertor geometry, heating method, and discharge parameters. In the original open divertor geometry, energy flow to the neutralizers accounted for 50-60% of the input energy, while radiation from the main plasma accounted for 20-40%, depending on the density and the heating source. For single-null discharges in the modified closed divertor geometry, the main plasma radiation remains at a similar level, but the neutralizer deposition decreases to < 20% and radiation from the divertor scrape-off must be included to achieve energy accountability. The energy deposition width on the neutralizers is found to vary with plasma conditions in the closed geometry.