Behavior of a Cold Ion Plasma in a Toroidal Octupole

J. C. Sprott
Department of Physics, University of Wisconsin, Madison, Wisconsin 53706
(Received 6 October 1969)


By raising the background hydrogen gas pressure to ~ 10^-4 Torr and injecting 10-100 kW of 700-9000 MHz microwave power for ~ 100 microsec, an afterglow plasma with n ~ 10^9 - 10^11 /cc and kTi < kTe ~ 1 eV can be produced in the Wisconsin toroidal octupole. The particle lifetime is ~ 3 msec, or somewhat longer than for a hot ion, gun injected plasma, and most (~ 80%) of the plasma is lost to the hoops. The electron temperature decays rapidly as a result of inelastic electron-neutral collisions. By changing the magnetic field strength and microwave frequency, the density distribution can be varied, and a variety of fluctuations produced. These fluctuations do not appear to be an important source of plasma loss.

Ref: J. C. Sprott, Phys. Fluids 13, 1626-1633 (1970)

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