Optimized method of measuring directed electron velocities using the incoherent regions of laser scattering

With the presumption that a shifted Maxwellian velocity distribution adequately describes the electrons in a flowing plasma, a method with optimum signal to noise resolution to measure directed velocity is described. The lowest velocity that can be determined by this method is shown to depend on the electron random thermal velocity. The basic diagnostic system is outlined and consists of a ruby laser source and two detectors set 180° from each other and both set at 90° with respect to the incident laser beam. Simplified analysis compared to standard peak shift detection techniques is seen to be possible using optimization techniques. This proposed method is shown to be superior in SNR for plasma temperature below 7.2 eV.