Time-resolved measurement of the electron distribution function in a magnetized laboratory plasma

A method for making time-resolved measurements of the electron distribution function in a strongly magnetized laboratory plasma is presented. Computer automation makes possible acquisition of data for ensemble averaged distributions simultaneously at 51 points in time with as little as 10 nsec separating distributions. Distribution functions are recovered from the raw data using a microcomputer and the uncertainty in the resulting distributions is estimated. Results of a pulsed beam experiment (Δt = 2 μsec) are presented. Properties of the measured distributions are compared with measurements made using traditional diagnostics. In particular, increases in density and temperature measured with langmuir probes are in good agreement with the measured distributions. Two-dimensional velocity-space diffusion is seen occurring on time scales short compared to particle-particle collision times