AVS 53rd International Symposium
    Vacuum Technology Tuesday Sessions
       Session VT-TuM

Paper VT-TuM13
The Deviation and the Long-Term Variation of the Sensitivity Factor of an Axial Symmetric Transmission Gauge

Tuesday, November 14, 2006, 12:00 pm, Room 2000

Session: Vacuum Generation and Measurement
Presenter: N. Takahashi, ULVAC Inc. Japan
Authors: N. Takahashi, ULVAC Inc. Japan
Y. Tuzi, ULVAC Inc. Japan
I. Arakawa, Gakushuin University, Japan
Correspondent: Click to Email
We have reported the basic characteristics of two types of axial symmetric transmission gauge (AT gauge). The original AT gauge@footnote 1@ was aimed solely at the measurement in extreme high vacuum (XHV) by the pulse counting of ions using a secondary electron multiplier (SEM). In the commercial type gauge (AxTRAN, Ulvac Inc.),@footnote 2@ which is for practical use in the wider pressure range between 10@super -11@Pa and 10@super -3@Pa, the SEM ion detector was replaced with a Faraday cup type ion collector to extend the upper limit of the operating pressure and to improve the drift of a sensitivity caused by SEM. In both types, the soft x-ray effect and the electron stimulated desorption effect, which disturbs the XHV pressure measurement, are reduced by the Bessel-box type energy analyzer placed between an ionizer and the ion detector. In the present paper, two fundamental characteristics of the commercial type AT gauge are reported: the sensor-head deviation and the long-term variation of the sensitivity factor. The sensitivity factors for nitrogen of 50 sensor-heads of AT gauges were measured by the direct comparison with the spinning rotor gauge. These sensitivity factors were compared with those of 30 sensors of the extractor gauges and the BA gauges. The standard deviations for the three types of gauges are almost the same. The long-term variation of the sensitivity factors of two AT gauges for nitrogen has been examined for several years. The factor of one gauge decreased by 10% gradually in first 1.5 year in the examination. In the following 3 years, the variation of the sensitivity factor was less than 2%. The variation for the other one was relatively small. This different behavior of the sensitivity factor between two gauges is likely caused by the difference of the pre-treatment of the Y@sub 2@O@sub 3@ coated Ir filament before assembly. @FootnoteText@ @footnote 1@ H. Akimichi, et al., JVST A15 (1997) 753.@footnote 2@ N. Takahasi, et al., JVST A23 (2005) 554.