The measurement of negative-ion concentration in the plasma of non-self-maintained Townsend discharge and microwave discharge

We present the results of direct measurements of the ratio of concentrations of the negative ions and electrons in a mierowave discharge at pressure p = 0.1 Torr, and in a non-self-maintained Townsend discharge at pressure p = 50-760 Torr. The method of measurement is based on the introduction of a high-frequency filter in the gas during the application of a weak diagnostic constant field.