High-Velocity Plasma Injection into a Cusped Magnetic Field

Abstract

The injection and subsequent behavior of a dense (∼3 × 1013/cm3) fast (V̄ ∼ 108 cm/sec) deuterium plasma jet fired from a coaxial plasma gun into a simple biconical cusped magnetic field has been studied. The experiment shows that for sufficiently high cusp fields up to 90% the plasma jet penetrates the entrance cusp and is lost through the ring cusp without being trapped. In the process of injection a part of the ion energy in the plasma jet is found to be transferred to a group of electrons. X rays of up to 220-keV energy are observed from these energetic electrons with a characteristic decay time of up to 1 msec for cusp fields of 8.5 kG. These long duration energetic electrons are found to be accompanied by a variety of slow high momenta impurity ions (e.g., Fe, O, Si, etc.) in transit through the field and lower energy ions trapped for times in essential agreement with theoretical values for a low-β plasma in a simple cusped field. Observations on the plasma potential are also described.