抄録
In connection with studies for developing a microwave discharge chamber which detects tracks of charged particles, a number of important properties of a pulsed microwave discharge have been investigated. A pulsed microwave field of variable pulse widths, τp=0.1∼2 μ sec, has been applied to a mixture of neon and argon at a total pressure of 100 mm Hg, but with various mixture ratio. The results are; a) the breakdown field strengths are approximately by one order of magnitude higher than those in continuous RF discharges and are less sensitive to the relative concentration of argon in neon, r, for smaller τp, b) the breakdown field strength decreases with increasing r, reaches a minimum and increases again with a further increase of r, and c) the optimum value of r for the minimum breakdown field strength increases with decreasing τp. These properties can be explained in teams of the direct ionization whose relative contribution becomes predominant as E⁄p increases and/or τp decreases. The so-calld Penning effect is found to be important only for a low value of E⁄p. The observed formative time lags and the time variation of particular line intensities are also in essential agreement with our theoretical analysis.
