Reignition Voltage in a High-Pressure rf Discharge

rf glow discharges at high pressure are quenched after every half-cycle and must be reignited in the following half-cycle. The reignition voltage Vi was investigated experimentally in the frequency range 0.15–1 MHz. It was found that Vi grows with electrode distance d up to a certain value dmax. At dmax, Vi decreases distinctly and stays low for a further increase of d. The explanation given for this effect is that at relatively small electrode distances all charge carriers can be removed from the discharge gap before reignition and breakdown must take place without support from space charges. For large d, however, the charge carriers cannot travel through the whole gap in the given time. Some remain in the gap and facilitate breakdown. Therefore a smaller value of Vi can reignite a long gap. The measured frequency response of Vi supports this explanation. A theoretical estimate of values of dmax is within a factor of 1.6 of experimental values.