Pulsed Low Frequency Inductively Coupled Plasma Generator and Applications

In this paper, an inductively coupled pulsed plasma source with an operating frequency of 29 kHz is described. Using a series resonance circuit with a load capacitance of 12 muF and large diameter (approximately 20 cm) induction coils surrounding a spherical discharge vessel, a discharge plasma was produced and investigated in a pressure range of 0.1 to 100 Pa. Pulsed coil currents reached a maximum value of 9.6 kA with current rise times of 1.8 kA/mus while achieving an energy coupling efficiency of 80% between the driving circuit and the plasma. Pulsed-power peak values reached more than 800 kW. Moreover, the spectroscopic diagnostic revealed a high fraction of ionized particles and an emission spectrum in the near UV domain. Electron densities reached peak values of 10²¹ m^-3. By using a fast camera system, the initiation of the discharge was investigated. The ignition of the discharge along an azimuthal path was documented, showing evidence of an entirely inductive plasma initiation without capacitive coupling.