Expansion Rate Measurements at Moderate Pressure of Nonneutral Electron Plasmas in the Electron Diffusion Gauge (EDG) Experiment
Authors: Kyle A. Morrison, Ronald C. Davidson, Stephen F. Paul, Emily A. Belli, and Edward H. Chao
Date of PPPL Report: May 2001
To be published: in the July 2001 issue of Physics of Plasmas.
Measurements of the expansion rate of pure-electron plasmas have been performed on the Electron Diffusion Gauge (EDG) device at background helium gas pressures in the 5 x 10-8 Torr to 1 x 10-5 Torr range, where plasma expansion due to electron-neutral collisions dominates over plasma expansion due to trap asymmetries. It is found that the expansion rate, defined as the time rate of change of the particles' mean-square radius, scales approximately linearly with pressure and inversely as the square of the magnetic field strength in this regime, in agreement with classical predictions.