Penetration of a transverse magnetic field by an accelerated field-reversed configuration

Abstract

The field-reversed configuration (FRC) is a compact toroid with near unity β that is an ideal candidate to provide central fueling for large tokamaks. The study of the acceleration and penetration physics of the FRC into a transverse magnetic field gradient is necessary in order to evaluate the fueling efficiency of the FRC. To this end, experiments were conducted on the LSX/mod facility [J. T. Slough and A. L. Hoffman, 16th IAEA Fusion Energy Conference 1996 (International Atomic Energy Agency, Vienna, 1997), Vol. II, p. 237], where large mass (0.8 mg) FRCs were accelerated to high velocity (2×105 m/s), and then guided into a transverse magnetic field. Various diagnostics were employed to characterize the penetration process. These included thermocouple probes, magnetic probes, and emission arrays. A simple analytical model is developed that explains the basic features of the penetration process. Further modeling with two-dimensional numerical calculations provided for scaling laws to reach the conditions necessary to penetrate a large fusion tokamak.