Electrical Cleanup of Gases in an Ionization Gauge

Observations have been made on the electrical cleanup of different gases in a Bayard-Alpert ionization gauge. It has been found that the ion current striking the wall of such a gauge is 5 to 10 times that reaching the ion collector. It is therefore possible to account for a maximum pumping speed of 0.1 to 0.2 l/sec due to ion pumping at the gauge walls. The maximum pumping speed observed was 0.1 l/sec for nitrogen. It was found that the maximum pumping speed for nitrogen remained the same when the inner wall of the ion gauge was covered with a thin metal deposit or Aquadag. An expression has been derived on the basis of ion pumping which describes the observed cleanup.