Particle and Heat Transport Measurement Using Laser Induced Fluorescence.
Abstract
Cross-magnetic-field diffusion of test particles and heat in pure ion plasmas has been measured. The ion plasma is contained in a Penning-Malmberg trap for weeks, with plasma expansion and loss suppressed by a ``rotating wall'' technique. The ion spin orientation is used to ``tag'' the test particles. The spin orientation is controlled by direct optical pumping, and is non-destructively probed with a ``cyclone'' transition. The transport in these plasmas is dominated by long range E × B drift collisions, with impact parameters ρ in the range rc < ρ < λ_D. In contrast, ``classical'' velocity scattering collisions with impact parameters ρ < rc produce negligible transport. The measured diffusion of test particles is in precise agreement with the long range production, and is 10 times larger than the ``classical'' velocity scattering production. In axially short systems, the interactions become essentially 2-dimensional, and particles interact for long periods of time. The test particle transport is then limited by the shear in the E × B rotation. Also, the thermal diffusivity due to long range collisions is found to be independent of the magnetic field and plasma density; and is up to 200 times larger than predicted by classical collisions in the parameter range of the experiments.
- Publication:
-
APS Division of Plasma Physics Meeting Abstracts
- Pub Date:
- October 2003
- Bibcode:
- 2003APS..DPPKM2003A