Broadband microwave measurement of electron temperature of a large coaxial gridded hollow cathode helium plasma

Abstract

This paper reports a new kind of large coaxial gridded hollow cathode discharge at low pressure in a helium atmosphere. A method is presented to determine the electron temperature by measuring the broadband microwave properties; typically, the frequency band extends from 2 to 12 GHz. The method involves positioning the discharge device between the two antenna ports to measure the scattering parameter using a network analyzer. For a weak ionized plasma, this method is stable over the entire frequency range. A microwave signal loss of 0.27–37.83 dB was measured within the frequency range. Based on the measured attenuation of the microwaves, the electron temperature was estimated to range from 1.6–4.6 eV under different conditions, which showed good agreements with the results of Langmuir Probe measurements.