In:
Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, American Vacuum Society, Vol. 13, No. 5 ( 1995-09-01), p. 2574-2578
Abstract:
For extreme high vacuum pressure measurements a modified gauge of the type described by Lafferty was fabricated [J. M. Lafferty, J. Appl. Phys. 32, 424 (1961)]. To determine the limit of low pressure measurement, its residual current was experimentally estimated. Residual current consists of x-ray-produced photoelectron current and electron stimulated desorption (ESD) ion current. Residual current was studied using the Bayard–Alpert method [R. T. Bayard and D. Alpert, Rev. Sci. Instrum. 21, 571 (1950)] . The linear relationship between emission current and residual current was obtained. The ratio of x-ray-produced photoelectron current to emission current was on the order of 10−7; the ratio of ESD ion current to emission current was on the order of 10−8; both ratios were obtained using a cleaned stainless steel anode. In order to investigate the upper limit of ESD ion current, the anode was exposed to oxygen gas at a fixed pressure and ESD ion currents were measured as a function of exposure. The upper limit of the ratio of ESD ion current to emission current was on the order of 10−5; residual current was on the order of 10−16 A with an emission current of 10−9 A. Sensitivity obtained was 4×10−3 A/Pa with an emission current of 10−9 A. Therefore, the predicted low pressure limit for the modified Lafferty gauge was on the order of 10−13 Pa.
Type of Medium:
Online Resource
ISSN:
0734-2101
,
1520-8559
Language:
English
Publisher:
American Vacuum Society
Publication Date:
1995
detail.hit.zdb_id:
1475424-1
detail.hit.zdb_id:
797704-9
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