The Relation Between the Diameter of a Nipple and the Sensitivity Coefficient of a Nude Type Bayard-Alpert Gauge

Four nude type Bayard-Alpert gauges attached in nipples of different inner diameters of 35, 38, 54 and 70 mm, were calibrated for nitrogen at the emission currents of 0.4, 1 and 4 mA using a spinning rotor gauge as a reference standard. The sensitivity coefficient of the gauges was influenced considerably by the diameter of the nipple and the emission current. All of the gauges attached in the 70 mm-diameter nipple showed a good stability of the sensitivity coefficient in the pressure region from 1×10-5 Pa to 3×10-2 Pa at the emission current of 0.4 mA. The change in the sensitivity coefficient was also discussed from the viewpoint of the distribution of the electric potential inside the nipple and the space charge effect of electrons and ions.