TUNGSTEN EVAPORATION LIMIT OF HOT-CATHODE IONIZATION GAUGES

Experiments were made to determine reasons for discrepancies in measurements of pressure in the low 10** minus **1**2 Torr range with hot filament and partial pressure gages. The method proposed by Alpert and Buritz, with a slight modification, was used for estimates of the tungsten evaporation limit, which for three gages fell in the range (1-2) multiplied by 10** minus **1**2 Torr at electron emission of 10 mA. Reduced emission of the ionization gage at 4 mA is recommended to reduce error due to tungsten vapor.