Classical Collisional Diffusion in the Annular Penning Trap

摘要

Transport of particles and energy by cross-field diffusion has been studied in the annular Penning trap in which a nonneutral plasma of electrons is contained between concentric cylinders. At densities sufficiently low (<10~5 cm~(-3)) to suppress mobility transport arising from the space charge electric field, the dominant source of transport is diffusion from collisions of electrons with added helium gas. The particle diffusivity, when corrected for asymmetry transport, is observed to scale linearly with collision frequency and inversely with the square of the axial magnetic field. Measurements of (he electron energy distribution as a function of time show an initial mean energy of 0.3 eV which decreases with time as a result of diffusion cooling.