The C-2W Experimental Device Fueling Systems Overview

The experimental goals of the C-2W program are to demonstrate the ability to heat and maintain a field-reversed configuration (FRC) plasma to a total temperature of several keV for a period of up to 30 ms. As energy confinement times are improved, the particle loss rate will become the dominant limiter of plasma lifetime. In order to mitigate this loss channel, several refueling methodologies have been implemented on C-2W. They are: compact toroid injection (CTI), pellet injection, and gas puffing. Each of the two CTI systems is capable of injecting up to 5 CTs over the course of a single shot. The pellet injector launches cryogenically frozen pellets of deuterium from one end of the confinement vessel, through the FRC’s X-point and into the core. By aiming the pellets such that they miss the beams, ablation of the pellets external to the FRC is minimized. Puff valves placed in strategic locations along the vessel add neutral gas to the scrape-off-layer (SOL). This keeps enough plasma outside of the FRC so good electrical connection with edge divertors is maintained. Each refueling method can provide a sufficient number of particles to overcome the particle loss rate. However, the regions of effective fueling varies between the systems.