Characterization of a new variable magnetic field linear plasma device

Abstract

A radio frequency plasma device is presented in which the regions of plasma creation and maximum plasma magnetization can be separated along a 1.5-m tube. Measurements of the plasma density, plasma potential, and electron temperature in the device successfully reproduce previously reported plasma features. These validate the ability of the experiment to continue the investigation of a regime of operation in which the axial plasma density follows the profile of the applied magnetic field, as long as the ions are magnetized under the antenna. The density is shown to increase on axis owing to the decreasing cross section of the converging magnetic funnel connecting the antenna region to the solenoids. When the funnel pinching is increased, stronger magnetic fields are required to inhibit cross-field diffusion and to bring the density on axis in the expected 1012 cm−3 range. Collisionless transport of hot electron populations is observed along the field lines which intersect the area under the antenna and coincides with the presence of high-density conics more than 0.5 m away from the antenna for magnetic fields ≥600 G.