Electron Bombardment of Nitrogen Gas Ionization in a DC Electric Field

Nitrogen gas can be ionized by the high field produced by the needle-plate electrode arrangement. Nitrogen gas ionization occurs around the tip of the needle with the highest field intensity. Each ionization process produces one electron and one positive ion from the nitrogen gas molecule. If the needle electrode voltage is negative polarity and the plate is grounded, then in the dc electric field, electrons will move accelerated towards the electrode plate and positive ions will always be present around the tip of the needle and a portion of the remainder is dissipated into the needle electrode. The level of electron energy that bombards a plate electrode is determined by the level of the electric field and the pressure of the Nitrogen gas. The greater the energy kinetic electron when it hits the electrode plate, the cavity diameter will also be greater. However, the energy of electrons when hitting plates varies because the final free path of electrons is probabilistic.