Progress and Issues with Pulsed Magnetic Fusion

Pulsed magnetic fusion (PMF) concepts have been explored since the 1950’s as both z-pinch and theta-pinch discharges offered early opportunities for creating high temperature plasma. It was quickly realized that high-beta plasma configurations suffered from several MHD instabilities, so attention shifted to very low-beta systems (e.g., stellarators). During the intervening decades, however, progress has been made on arrangements that are both high-beta and adequately stable. These include the Sheared-Flow Stabilized Pinch and the Field Reversed Configuration. Some concepts benefit especially from the ability to retrieve the energy delivered and portions of the nuclear energy retained in the plasma in order to reduce the fusion energy necessary for the reactor cycle and thereby lessen the required energy per pulse. Concepts operating at high magnetic fields offer reductions in energy and system size and also the possibility of extension to so-called advanced fuels, mitigating the problem of dealing with tritium. PMF involves the manipulation of magnetic flux and depends critically on avoiding interception of magnetic flux by electrical conduction between power source and load (e.g., insulator breakdown, surface flashover, extraneous plasma, and charged-particle flows). Energy is also lost to magnetic diffusion into and out of conductor surfaces. The effects of fusion plasma radiations on these processes are discussed in the context of reactor prospects.