Excitation and Ionization Rates in Hydrogen at Very High E/n
We will report time-dependent electron density and excited state density measurements at very high E/n with a temporal resolution of 1 nsec. We create electron avalanching in gases of interest using a fast-rising (3–6 nsec) microwave (S-band) pu1se, while simultaneously monitoring the electrondensity with a low-power, S-band probe signal. This latter signal is in an interferometer configuration having sufficient sensitivity to monitor densities as low as ≅106 cm–3. The avalanche ionization takes place in a quartz cell contained in the S-band waveguide and having no electrodes or externally applied fields, except for a longitudinally applied magnetic field tuned to electron-cyclotron resonance at the high-power pulse frequency. The equivalent effective field under these conditions reduces to a DC field at one-half the peak value.