Limitations on Mass Separation by the Weakly Ionized Plasma Centrifuge

Abstract

bstract A In weakly ionized argon and xenon rotating plasmas the rotational velocity and the temperature and pressure distribution have been measured. The stationary discharge is generated by two opposed cathode-anode configurations. The arc current of 100 A is drawn across an axial magnetic field up to 0.26 T. The filling pressure ijs varied between 1 and 10 torr. The rotational velocity is found to be proportional to the discharge current and the magnetic field and inversely proportional to the viscosity of the neutral gas. The rotational kinetic energies of the particles in the argon and xenon discharge are about equal. Because the temperature of the argon discharge is lower than that of the xenon discharge, the pressure rise in radial direction due to centrifugal forces is steeper for the former. A theoretical analysis taking into account viscous dissipation as the only heating mechanism yields a heavy particle temperature T which imposes an upper limit to the ratio X =½m υθ 2/kT of order unity. The maximum attainable separation factor α is therefore limited in these types of centrifuges. Experimentally, in the parameter region studied, X is found not to exceed a value 0.4 in argon discharges and 0.2 in xenon discharges. A rough estimate shows that besides viscous dissipation other heating mechanisms are also important. Ohmic heating, for instance, is at least a factor 6 larger than the viscous dissipation.