Detection Limit of Laser Thomson Scattering for Low Density Discharge Plasmas

Laser Thomson scattering is a method for measuring electron properties of plasmas. Recent applications have showed that this method can be applied to much lower density plasmas than was previously possible. In this paper, a formalism is given for estimating the lower detection limit for different experimental arrangements and the lower detection limit of electron density in low density discharge plasmas is presented. It is shown that the intensity of the background plasma emission is the main factor that determines the signal-to-noise ratio and hence the lower detection limit. The dynamic range for measurements of electron energy distribution functions is also discussed.