AVS 45th International Symposium
    Vacuum Technology Division Monday Sessions
       Session VT-MoM

Paper VT-MoM4
Long Term Behavior of an Axial-Symmetric Transmission Gauge

Monday, November 2, 1998, 9:20 am, Room 329

Session: Vacuum Gauging, Outgassing and Leak Detection
Presenter: H. Akimichi, ULVAC Corporation, Japan
Authors: H. Akimichi, ULVAC Corporation, Japan
K. Takeuchi, ULVAC Corporation, Japan
Y. Tuzi, ULVAC Corporation, Japan
I. Arakawa, Gakushuin University, Japan
Correspondent: Click to Email
An axial-symmetric transmission gauge (AT gauge) is an ionization gauge developed for the pressure measurements in ultrahigh and extreme high vacua. In the gauge, a Bessel-box type energy filter is placed between the ionizer and the ion collector to eliminate the effects of soft X-ray and electron stimulated desorption ions. The lower limit of the pressure measurement by the AT gauge is estimated to be 10 @super -12@ Pa. The sensitivity factor for hydrogen calibrated by the conductance modulation method was about 2 x 10 @super -3@ Pa @super -1@, and was constant in the pressure range from 10 @super -10@ to 10 @super -6@ Pa. We have examined the characteristics of the AT gauge such as the sensitivity factor, the outgassing rate, etc., over the period of 3200 hours. It was found that the condition of the continuous dynode type electron multiplier, which is used for the ion detection in pulse counting mode, was one of the most important factor that determine the gauge characteristics. The followings were noticed in our study: (1) the outgassing rate of the electron multiplier was higher than that of the ionizer and the energy filter, (2) the outgassing rate of the multiplier as received from the manufacturer was very high but decreased to acceptable level after a few days operation, (3) the outgassing rate of the multiplier increased after exposure to the atmospheric air but restored, (4) the temporal increment of the sensitivity factor was observed after the exposure to the atmospheric air and was assumed due to the change in the secondary electron yield of the electron multiplier, (5) the correlation between the residual current by the X-ray effect and the sensitivity factor of the gauge were observed.