Drift-kink instability induced by beam ions in field-reversed configurations

摘要

The drift-kink instability in field-reversed configurations with a beam component is investigated by means of a three-dimensional particle simulation. The unstable mode with the toroidal mode number n=4 grows with the rate (gamma) (approx) 0.1 - 1.0(omega)(sub ci) for a strong beam current and deforms the plasma profile along the beam orbit in the vicinity of the field-null line. This mode is nonlinearly saturated as a result of the relaxation of current profile. Both the saturation level and the growth rate tend to increase as the ratio of the beam current to the plasma current I(sub b)/I(sub p) increases. It is also found that there is a threshold value of the beam velocity (upsilon) (sub b) (approx) (upsilon)(sub Ti) (ion thermal velocity) for the excitation of the instability. (author)