On Some Improvements of Ionization Gauges of the Extractor Type for the Measurement of Extreme High Vacuum.

Abstract

The extractor principle seems to be the most useful principle for the measurement of xhv. Even simple extractor systems are able to discriminate between ions generated in the gas phase and ESD ions produced at the grid surface. According to our calculations the modified extractor gauge developed in our institute is less influenced by ESD ions than the extractor gauge suggested by Redhead. By experiments was demonstrated, that a gold coating of the anode reduces the ESD effect too.In the case of an extractor gauge the light of the hot filament gauge has a small influence on the ion current in the xhv range. The influence of the vapor pressure of the cathode material on the ion current can be reduced by the use of activated cathodes operating at low temperatures. These results were obtained experimentally.Topics of a further development are the problems of the reduction of the outgassing rate and the fast and convinient measurement of extremely low ion currents. The use of electron multipliers complicates the degassing process and the electronicequipment for the measurement of these low ion currents.