Plasma property measurement in a miniature microwave discharge ion thruster by laser Thomson scattering

For understanding the mechanism of plasma production and loss in a miniature microwave discharge ion thruster, plasma parameters, electron number density and electron energy distribution function, in a miniature microwave discharge ion thruster were successfully measured by means of laser Thomson scattering. A photon counting method and a double monochromator were used against small Thomson scattering signal and strong stray laser light. The result shows an electron energy distribution function is Maxwellian, since the scattered spectrum can be fitted by Gaussian at the temperature of 1.5 eV. An electron number density is 2.3 × 10¹⁸ m^-3 The measured electron number density and electron temperature values were found to be reasonable compared with estimation deduced form extracted ion beam current.