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

Paper VT-TuP10
Influences of Handling Procedures on the Accommodation Coefficient of a Spinning Rotor Gauge

Tuesday, November 14, 2006, 6:00 pm, Room 3rd Floor Lobby

Session: Vacuum Technology Poster Session
Presenter: M. Hirata, NMIJ AIST, Japan
Authors: M. Hirata, NMIJ AIST, Japan
E. Komatsu, NMIJ AIST, Japan
H. Akimichi, NMIJ AIST, Japan
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A spinning rotor gauge is widely used as a reference standard and as a transfer standard. Stability of the effective accommodation coefficient of the rotor in the gauge is very important for these applications. The value of the coefficient is very stable in operation mode. Though the gauge was turned switch to on and off several times, the relative value of two gauges was constant within 0.05 % - 0.1 % corresponding to the limit by drift and fluctuation of their offset. But significant change in the value is some times observed by transportation. For example, change in the value up to 2% was observed during the comparison of vacuum standard among NMIJ, NIST, IMGC and KRISS. In this study, we examined the influence of handling procedures on the value. In the case that the sensing head was mounted and demounted from the thimble, the value changes about 0.3 % - 0.5 % occasionally. By the washing of the rotor by alcohol and water, the value changes about 2 % - 3 %. Scrubbing the rotor inside the thimble by moving a magnet externally caused about 1 % change in it. Putting the rotor out of and into the thimble also caused about 1 % change in it some times. Even if the rotor was handled with spring-loaded device, in which the rotor is moved and fixed by a spring, used for the comparison of vacuum standards in Europe countries, it changes also about 0.3 % - 0.5 % occasionally. These results show that it is depend on the surface condition of the rotor and scrubbing the rotor inside the thimble causes also unexpected change in it. Finally stability within 0.1% in it was obtained by the transportation of the rotor together with the thimble and the sensing head.