CALIBRATION OF AN AXIAL SYMMETRICAL TRANSMISSION GAUGE IN ULTRAHIGH AND EXTREME HIGH-VACUUM

The sensitivity factor of an axial symmetric transmission gauge (AT ga uge) was determined by the conductance modulation method (CMM) in the pressure range from 10(-10) to 10(-6) Pa. The gauge has a Bessel-box t ype energy filter between a Bayard-Alpert gauge type ionizer and an io n detector to eliminate the limiting factors of pressure measurement i n extreme high vacuum such as the soft x-ray effect and the electron s timulated desorption of ions. The lower limit of the pressure measurem ent of the gauge is estimated to be about 10(-12) Pa or lower. The sen sitivity factor showed a slight pressure dependence caused mainly by o utgassing from the gauge itself. The sensitivity factor of the AT gaug e, which was further corrected for the effect of outgassing by the CMM , is almost constant in the pressure range from 10(-10) to 10(-6) Pa a nd is (2.3 +/- 0.1) x 10(3) Pa-1 for hydrogen. (C) 1997 American Vacuu m Society.