Microwave interferometry for high pressure non-thermal pulsed plasma

Abstract

Summary form only given. Atmospheric pressure non-equilibrium plasmas are now used in many applications including those where low-pressure plasmas have traditionally been used. However, measurements of key plasma parameters in the highly collisional regime exhibited at atmospheric pressure offer challenges, which usually have to satisfy requirements that are different than those found at low pressures. In this paper, a millimeter (mm) wave interferometer system is used to measure the electron density and temperature of a low temperature atmospheric pressure helium plasma driven by nanoseconds pulses1. The plasma is generated by a modified dielectric barrier discharge where one of the electrodes is made of an aluminum plate covered by an alumina sheet while the second electrode is made of a copper disc (diameter of 5.7 cm) with several holes through which the operating gas is injected. The diameter of the holes is about 1 mm while the distance between nearby holes is 5 mm. The peak electron density and electron-neutral collision frequency are found to reach up to 8xl012cm"3 and 2.1x10 s" , respectively. Based on the electron-helium collision cross-section and the measured electron-neutral collision frequency, the electron temperature of the plasma is estimated to reach a peak value of about 8.7 eV.