Abstract
The purpose of this paper is to determine the low-pressure limit due to the soft X-ray effect for the sub-standard ionization gauge of type VS-1 which is specified as the standard in “Calibration Method of Vacuum Gauges” of the Japanese Industrial Standards.
Measurements have been made in a bakable ultra-high vacuum glass system by using such two methods as follows;
(1) Observation of the ion collector current as a function of the grid voltage,
(2) Comparison of the ion collector current in the sub-standard ionization gauge with that in the Bayard-Alpert type gauge.
The results indicate that the photoelectric current leaving the ion collector is about 2.8×10-10 A at the normal operating condition, corresponding to a pressure of 7×10-9 mmHg for nitrogen. It is, therefore, considered that there is an error of 1 % in the sensitivity of this gauge at a pressure of 7×10-7 mmHg. Factors affecting the measurements of the photoelectric current are discussed in detail.
