Observation of Collisionless Heating and Thermalization of Ions in a Theta Pinch

Spectral line profiles from impurity ions in a small theta pinch have been measured and are interpreted as ion-velocity distribution functions. For antiparallel driving and bias fields, the ions attain a Maxwellian distribution corresponding to a perpendicular temperature of 3-4 keV in a time short compared to particle self-collision times. Thermalization is less rapid for parallel magnetic fields.