ABSTRACT

We change our focus to the discharge phenomena that occur under high voltages in various gaseous media. For the purpose of this chapter the discussion is limited to sparking phenomena. It is well known that, given a uniform electric field, the breakdown voltage of a gap between smooth, clean electrodes spaced one cm apart in nitrogen at atmospheric pressure (101.3 kPa) is approximately 30.4 kV and that the breakdown voltage of a gap in the range from 0.1 to 5 cm shows a linear relationship with the gap length. Any deviation from linearity may be attributed to nonuniformity of the electrodes or to electrodes that are not tolerably clean and lack mechanical polish. Humidity also contributes to an increase in observed breakdown voltage, as discussed in connection with attachment processes in water vapor.