Time resolved Thomson scattering using a periodically emitting ruby laser

A ruby laser is presented which emits a sequence of regular spikes of megawatt peak power during each flashlamp discharge. Periodic Q-switching by means of a Pockels cell and a high voltage pulse generator was found to produce the desired laser emission. The laser was designed for application in plasma diagnostics to measure submillisecond temporal changes in electron density and temperature via Thomson scattering. The improvement in the signal-to-noise ratio obtained by the use of periodically emitted short pulses is discussed. A "boxcar" integrator was used for signal processing, allowing a choice between an optimum signal-to-noise ratio or time resolution of the measurement. A scattering experiment on a high density arc plasma was carried out successfully, demonstrating the capabilities of this new method. From these results the feasibility of a scattering measurement on a Tokamak machine, using this kind of laser, is inferred.