Time-resolved measurements of electron number density in argon and nitrogen plasmas sustained by high-voltage, high repetition rate, nanosecond pulses

Abstract

Weakly ionized plasmas in argon and nitrogen in a parallel-plate electrode configuration at a gas pressure of several Torr were sustained by repetitive nanosecond pulses with the pulse repetition frequency sufficiently high to ensure that the plasma does not fully decay between the pulses. In order to measure the electron number density decay in the afterglow of each pulse, a custom-constructed 58.1 GHz homodyne microwave interferometer was used. Initial analysis of the measured electron density decay indicates that dissociative recombination with molecular and cluster ions was the dominant electron loss mechanism for both gases, and that the electron thermalization was significantly faster than the decay of their density. The plasma with low electron temperature between the pulses could potentially be used to reduce the Johnson-Nyquist thermal noise in plasma antennas.