Stability tests of ionization gauges using two-stage flow-dividing system

Stability tests of four ionization gauges (a BA gauge, an extractor gauge, an AT gauge, and a BA gauge with a heating electrode) were performed using a two-stage flow-dividing system from four viewpoints: (1) the fluctuation and drift of pressure readings, (2) the repeatability of pressure readings, (3) the change in sensitivity owing to prior conditions of use and (4) long-term stability. These tests were performed at pressures from 8 × 10−6 Pa to 8 × 10−4 Pa using N2 gas under tightly controlled conditions.The fluctuation and drift of the four IGs were within 1% over 1 h. Their repeatability was also within 1% during eight cycles with an interval of 1 h between each cycle. Although changes in sensitivity of several percent owing to prior conditions of use were observed, the sensitivity was recovered to within 1% of its original values after operation in ultrahigh vacuum for one day. The result of a long-term stability test over a year showed that the sensitivity of the four IGs tended to decrease by 2.6–5.4% due to aging, depending on the gauge.