The Growth of Pre-breakdown Current in Helium†

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Abstract
The growth of pre-breakdown current across a uniform electric field discharge gap of finite dimensions has been calculated for helium. The current has been assumed to be amplified by electron ionization and by the production of secondary electrons at the cathode by positive ions, metastables and non-resonance radiation, with allowance made for the loss of secondary currant out of the discharge gap. It has been shown that experimental measurements of the pre-breakdown current obtained for the range 3 −1 torr−1 cannot be analysed to give the electron ionization coefficient (α) without the help of subsidiary experiments to measure the relative abundance and secondary coefficients for the processes producing the secondary electrons. The analysis of these currents by the currents by the Townsend equations (1915) has been shown to give incorrect values of α, especially at the low E/p values where αT may be several times larger than α.