CONTROL OF ION TEMPERATURE ANISOTROPY IN A HELICON PLASMA

Laser induced fluorescence measurements of the parallel and perpendicu lar ion temperatures in a helicon source indicate the existence of a s ubstantial ion temperature anisotropy, T-perpendicular to/T-parallel t o > 1. The magnitude of the ion temperature anisotropy depends linearl y on the source magnetic field. The parallel ion temperature is indepe ndent of magnetic field strength while the perpendicular temperature i ncreases linearly with increasing magnetic field. Bohm-like particle c onfinement is proposed as an explanation for the linear dependence on magnetic field of the perpendicular ion temperature. In the helicon mo de, the ion temperature components are independent of RF driving frequ ency and power and show a trend towards isotropy at high neutral fill pressures.