Ion Energies at the Cathode of a Glow Discharge

The energy distribution of ions striking the cathode in a glow discharge has been measured for a series of gases including hydrogen, helium, neon, and argon. Standard ultrahigh vacuum techniques were used to maintain a high degree of gas purity. The ions were detected by placing a small pinhole in the cathode of a glow discharge and analyzed for energy by means of a sector-type electrostatic analyzer. The ion species was determined with a conventional magnetic analyzer and the resulting ion beam intensity measured with an electron multiplier. An oscilloscope display gave the ion-energy distribution for a particular ion species. A simple theory involving assumptions that the ions originated in the negative glow and undergo primarily symmetrical charge transfer as they pass through the cathode dark space to the cathode gives results that are in most cases in good agreement with experiment. The charge-transfer cross sections determined are in reasonable agreement with other published data.

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