Ion-chamber measurements of the photoionization produced by point-to-plane corona discharges in air, oxygen, and nitrogen (commerical grade) over a pressure range of 0.1 to 18 Torr are reported in this paper. The results are expressed in a generalized form that reduces the data for each gas to a single curve relating photoionization to pressure (p) times distance (R) from the discharge. The range of Rp values is between 1 and 550 cm Torr. Absorption coefficients are compared to those reported by other investigators by plotting absorption coefficient/pressure vs Rp. In air and oxygen the values fall along a common curve. These results indicate that relating the ion-chamber currents to Rp in the manner described in this paper may provide a useful basis for calculating the photoionization produced by discharges in these gases.
The influence of a positive streamer upon its successor in a sequence of streamers is experimentally studied in a 3.17-cm positive point-to-plane gap using room air at room temperature. Streamers are triggered either by natural processes or by voltage perturbations (pulses) superimposed on the steady gap voltage. Despite the fact that a streamer has an inhibiting effect on the triggering of a later streamer, if another streamer is successfully triggered within a few tenths of a millisecond of the earlier streamer, using gap voltages of 16–25 kV, the later streamer will follow the same path and propagate faster than if the time interval between streamers was longer. Observations are made of the buildup and speed of primary and secondary streamers in sequences culminating in breakdown, and the filamentary spark breakdown of the gap is shown to have different current and light characteristics as a function of time from a streamer. A qualitative model of the streamer buildup mechanism involving metastable atoms or molecules is presented.
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