Interpretation of Experiments on Electron Emission in Spark Gaps

Recent experiments on electron emission in spark gaps with fields of the order of 105 v cm-1 have been interpreted in terms of a Fowler-Nordheim emission process. It is shown that a better explanation is thermionic Schottky emission allowing for surface irregularities, although it is not yet possible to distinguish between the two types of law. Expressions are derived giving relationships between the parameters in the two interpretations. The work function (~1.5-2 eV) and emitting area (1-10-8 cm2), for agreement with the Schottky effect, should be capable of a much simpler physical explanation than the extremely low values obtained from a Fowler-Nordheim interpretation. A large error can be introduced in the latter case by neglecting thermionic emission. If it is assumed that the emitting surface is heated locally to 500°C, the work functions in the Schottky interpretation are of the order of 4 eV.