Measurement of collisional anisotropic temperature relaxation in a strongly magnetized pure electron plasma

The rate at which the temperatures parallel and perpendicular to a magnetic field relax to a common value has been measured in a pure electron plasma. This rate was measured over the temperature range 28 to ${10}^4$ K and for magnetic fields in the range 30 to 60 kG. When the cyclotron radius ${\mathit{r}}_{\mathit{c}}$ is large compared to the classical distance of closest approach b, the measured rates are described by conventional scattering theory. When ${\mathit{r}}_{\mathit{c}}$/b<1, the measured rate drops precipitously as ${\mathit{r}}_{\mathit{c}}$/b is decreased, in agreement with the adiabatic-invariant theory of O’Neil and Hjorth.