Experimental study of the dissipative trapped ion instability

A new, steady-state linear machine has been constructed which produces a low-density, low-temperature hydrogen plasma in the collisionality regime of the dissipative trapped ion instability. This instability was seen and identified through the observed dependence of the wave amplitude on trapped fraction, axial and radial position, and collisionality and through the scaling of the real frequency with trapped fraction. The observed radial and axial mode structure of the instability is compared with the results of a simple radial model and a calculation of the Landau damping for both trapped and transit particles in a linear geometry.