Nonlinear Excitation Of Ion-acoustic Modes By Rf Waves

We have detected a slow ion-acoustic wave propagating obliquely to the equilibrium magnetic field in a low-density, weakly ionized helium plasma produced by rf power in the linear mirror machine LISA. When an upper hybrid wave is launched perpendicular to the ambient magnetic field, we have observed that the upper hybrid wave decays parametrically into another upper hybrid wave and a slow ion-acoustic wave. © 1992 The American Physical Society.45107640764

Energy Transport in Mirror Machine Lisa at Electron Cyclotron Resonance

The energy balance of a weakly ionized radiofrequency produced plasma at electron cyclotron resonance is analyzed both analytically and experimentally for a mirror-confined configuration. It has been shown that the plasma heating rate is a function of the resonant volume and the anisotropic ternperature condition. I. Introdu Aion LISA is a linear magnetic rnirror machine donated to the Plasma Physics Laboratory of Universidade Fe- steady state weakly ionized mirror-confined RF plasma. An R F sou:rce of 2.45 GHz and 800 W is used to inject power :;hrough the rectangular waveguide to produce the pluma. The magnetic field coils are fed by a DC c u r r e~t generator and produce the rnirror magnetic field. 'rhis field radially confines the I1F produced plasma. The rnirror coils at the two extremities are not being used. The magnetic field along the axis is not uniform since the waveguide port takes up the space of one magnetic coil and consequently a minimum field is formed a,, this location. We make use of this peculiar feature to have a local mirror-confined plasma and operate with seven additional coils next to the waveguide port disconnected to get a larger rnirror ratio and a better confinement. For diagnostics, we use a plane Langmuir probe and a diamagnetic coil to measure the plasma density, temperature, and pressure, and a Hall probe to measure the equilibrium magnetic field distribution. Helium is used as a working gas which is maintained at a background pressure of 6 x 10-4 Torr