Ion Flow Measurements and Plasma Current Analysis in the Irvine Field Reversed Configuration

The contribution of the ion current in the lab frame to the total plasma current is studied in the Irvine Field Reversed Configuration (IFRC). A charge-exchange neutral particle analyzer chops the emitted neutrals at a rate of 13 kHz and shows that the peak energy is below the 20eV minimum detectable energy threshold. A modified monochromator that is used to measure Doppler shifts of impurity lines indicates that there is a flow in the range of 5-7km/s in IFRC. By evaluating the collision times between the impurities and hydrogen, the dominant plasma ion species, it is concluded that the ions rotate with an angular frequency of $\sim 4\times 10^4$ rad/s. Estimates of the ion current in the lab frame are accomplished by determining the ion density distribution using pressure balance, and by fitting the measured magnetic probe data to a theoretical equilibrium. The results from these estimates indicate that the ion current is 1-2 orders of magnitude larger than the measured plasma current of 15kA. Calculations of electron drifts from the equilibrium fields show that the electrons cancel most of the ion current.