Effect of an external electrode on the characteristics of a low frequency discharge

The variation of the breakdown voltage of a low frequency electrical pulsed discharge due to an external electrode is reported. The discharge tube consists of a thin glass tube having two internal hollow electrodes. A thin copper foil wrapped around the glass tube forms the external electrode. The internal electrodes of the discharge tube are supplied by a flyback converter. Its operating point is self-adjusted being matched to the operating regime of the discharge. In this way the flyback converter has two functions, namely, to supply the discharge and to detect the discharge changes. The pulsed electrical discharge was achieved including the discharge tube and flyback converter in a relaxation oscillator circuit. The modifications of the relaxation oscillations threshold voltages if the external electrode is connected to the ground by means of a resistor are evidenced. The discharge tube is intended to be used as a plasma antenna. Because at low frequencies the RF excitation circuit is equivalent to a low impedance connection to the ground, the purpose of the work is to evaluate the RF excitation circuit influence on the characteristics of the discharge plasma. Measurements revealed that breakdown voltage decreases as effect of the external electrode.