FRC 2001: A White Paper on FRC Development in the Next Five Years (1996)

This document expresses the consensus of a worldwide community of fusion energy researchers on directions for research on the field-reversed configuration (FRC) over the next 5 yr.The FRC, a variety of compact torus, occupies a unique position in the parameter space of magnetically confined plasmas. It differs markedly from other toroidal systems: no mechanical structure in the center of the torus, no appreciable toroidal field, engineering beta near unity, no rotational transform, and scrape-off layer exhausting outside the coil system. FRCs range from small gyroradius to large-orbit ion-ring-dominated plasmas. Because of these peculiar features, FRC research adds unique insight into the physics of tokamaks and similar fusion systems. Moreover, FRC research offers a means of exploring fundamental plasma physics questions unrelated to fusion.Review panels have repeatedly called for fusion system improvements in order to project economical fusion energy. However, even improved tokamaks may not overcome the shortcomings of low power density, high complexity, large unit size, and high development cost. Among alternative concepts based on low-density magnetic confinement, the FRC offers arguably the best reactor potential because of high power density, simple structural and magnetic topology, simple heat exhaust handling, and potential for advanced fuels. Projected FRC reactors are much smaller than those based on the tokamak. Small size leads to lower costs. The enormous potential payoff as a reactor justifies a broad and sustained program on FRC stability and confinement.Several FRC-related facilities are in operation around the world as well as other small theory efforts. Favorable results from theory and experiments have raised hopes for ultimate development into a practical fusion system. Parameters achieved include densities ranging from 5 × 1013 to 5 × 1015 cm−3, temperatures up to 3 keV (ions) and 500 eV (electrons), and β ∼ 0.75 to 0.95. Noteworthy achievements include formation by theta pinch and by counterhelicity merging, simulation of large-orbit ion-ring injection and trapping, stabilization of rotational instability, detection of global internal modes, tilting mode theory, global translation along a guide field, identification of transport anomalies, and demonstration of the convective nature of energy loss.In view of the foregoing, five action items are recommended. First, FRC research should be continued and expanded both as an adjunct to mainline fusion research and as a stand-alone alternative fusion concept. Second, existing FRC-related resources should be exploited in an expanded program, including both facilities and the intellectual capital established in institutions and individuals with a long commitment to FRCs. Third, new FRC facilities or upgrades of existing facilities should be considered on the merits of how they address the directions offered in this document. This should include consideration of a jointly operated international FRC research facility. Fourth, researchers and institutions with a history of activity on the tokamak should be encouraged to broaden their research to include FRC theory, diagnostic development, and systems studies. Fifth, vigorous international collaboration on FRC research should be encouraged, including at least annual workshops and long-term exchange visits.