Wave Structure in a Plasma Produced by the Injection of Fast Ions

The authors established in an earlier paper that, in the AS device, for injection currents from 0.1 to 0.8 mA, there occurs in a plasma an extremely abrupt increase in the amplitude of the high-frequency electric fields at the fundamental ion frequency and. its harmonics. This threshold value of the mean plasma density depended on the magnetic field strength, in close accordance with the theoretical condition when this condition is fulfilled there may develop in the plasma ion-cyclotron instability caused by the presence of a positive derivative in the transverse energy distribution function for fast ions. The authors present experimental results obtained by measuring the wavelengths of oscillations that develop as a result of instability. A conclusion regarding the wavelengths is reached by performing measurements with the help of a phase meter based on a system of antennae. It is established that for a constant -injection current the phase shifts between the antennae vary with time; this suggests that a set of oblique waves is excited in the plasma. (author)