Temperature and anisotropic temperature relaxation measurements in cold, pure-electron plasmas

Plasma temperatures in the range 25 to 2 x 10(6) K have been measured using a cryogenic, ultra-high vacuum, pure-electron plasma trap. The rate nu at which the temperatures parallel and perpendicular to the applied magnetic field relax to a common value has been measured over the temperature range 28 to 3.8 x 10(5) K and the magnetic field range 20 to 60 kG. This rate nu is closely related to the plasma collision frequency. When the cyclotron radius r(c) is large compared to the classical distance of closest approach b (r(c)/b much greater than 1), the measured values of nu are in agreement with conventional collision theory. When the cyclotron radius is small compared to the classical distance of closest approach (r(c)/b much less than 1), nu drops precipitously as r(c)/b is decreased, in agreement with the many-electron adiabatic invariant theory of O'Neil and Hjorth. (C) 1996 American Institute of Physics.