Gaseous divertor experiment

This work investigates the effectiveness of the gaseous divertor scheme for resolving the energy removal problem in a fusion reactor. In this scheme a volume of neutral gas, instead of a solid collector plate, absorbs the scrape-off plasma heat flux in the divertor chamber. A gaseous divertor is simulated in the QED device at PPPL. Radial plasma transport is determined by the intrinsic ion transverse diffusion rate, which is larger than the classical ambipolar diffusion theory prediction. Thermal transport along the field line can be explained by energy dissipation to neutrals through elastic ion-neutral collisions. It is demonstrated that the scrape-off plasma can be terminated in the divertor by the volume of neutral gas without touching a material wall, thus eliminating the need for the collector plate structure. Plasma heat flux is absorbed and deposited by neutrals over the larger surface area of the divertor chamber wall. Simultaneously, the scrape-off plasma maintains the larger neutral density in the divertor chamber by impending the backflow of neutrals through the divertor channel. Finally, the role of gaseous divertor in fusion devices and its advantages over a conventional divertor system are discussed