Comparison of experiments on plasma rotation in counter-rotating and divergent plasma centrifuges for isotope separation

Experimental studies on cylindrical plasma centrifuges of a counter-rotating type and a divergent type are carried out through measurements and analytic analyses of the rotating plasma velocity. In the experiments, the two plasma centrifuges are investigated under the same operation conditions with arc currents of 20-50 A, axial magnetic field intensities of 150-450 Gauss, electrode gap distances of 2-4 cm and chamber pressures of 50 Torr. Rotating velocities of plasma are measured along the radial and axial positions by using a double probe method, and show unique profiles predicted by theoretical analysis for these two centrifuges. In the case of counter-rotating plasma centrifuge having discharges between two ring electrodes of the same radii and no end losses, a high velocity region is formed in the discharge chamber broader than that of the divergent plasma centrifuge having discharges between two ring electrodes of considerably different radii and viscous losses caused by the presence of end walls. However, the peak rotating velocity is relatively lower in the former case. Compared with the theoretical results, these different characteristics of the rotating velocity profiles mainly come from the different discharge volumes depending on the electrode geometry and the boundary loss effects near the electrodes. Therefore, separation factors of these two plasma centrifuges should be estimated considering the different characteristics of their velocity profiles.