Vacuum and Surface Science
Online ISSN : 2433-5843
Print ISSN : 2433-5835
Volume 61 , Issue 8
Special Issue : Maintenance for Vacuum Equipment and Components
Showing 1-15 articles out of 15 articles from the selected issue
Preface
Special Issue : Maintenance for Vacuum Equipment and Components
Regular articles
  • Kohta KAWAHARA, Yuki KATO, Kosuke KUBOTA, Koichiro YAMAKAWA, Ichiro AR ...
    Type: Regular article
    2018 Volume 61 Issue 8 Pages 533-538
    Published: August 10, 2018
    Released: August 10, 2018
    JOURNALS FREE ACCESS

    An experimental system was developed for the physisorption study of hydrogen at substrate temperatures between 1.8 K and 10 K and at pressures down to 10-10 Pa. The vaccum system was separated into two rooms by a bulkhead ; the upper chamber contained a cryostat equipped with a 4 K mechanical refrigerator and the lower one a substrate kept in an extremely high vacuum. Helium was liquefied at the refrigerator in the upper chamber and was stored in a pot in the lower one. The substrate was directly attached to the helium pot. The substrate temperature was controlled with an accuracy of 0.1 K by a heater located in the helium pot. The adsorption density of hydrogen physisorbed on the copper surface was measured with use of the electron stimulated desorption method. The mean residence time of hydrogen was directly determined by applying this technique to the transient state of adsorption. The adsorption isotherms were obtained by monitoring the hydrogen ion yield as a function of the pressure in the adsorption equilibrium state.

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  • Namio MATUDA
    Type: Regular article
    2018 Volume 61 Issue 8 Pages 539-543
    Published: August 10, 2018
    Released: August 10, 2018
    JOURNALS FREE ACCESS

    In application of one dimensional diffusion theory to gas molecular flow in the steady state through long ducts of uniform cross section, diffusion coefficient 𝒟 is generally represented as

    here λ is a kind of mean free path and v is avarage velocity of molecules. Up to now rigorous expressions of λλS where λS is Smoluchowski's expression for λ which have been given by Smoluchowski himself and other author for rectangular, ellipsoidal and annular cross section. As for triangular cross section, the rigorous expression has been obtained only on equilatera-triangle cross section. In this report, the concrete expression of λS and the correction factor α defined by the ratio of λS/λK where λK is Knudsen's expression for λ, are deduced for long ducts with isosceles-triangle cross sections. The values for λS and α, which are given by these deduced formula, are compared with those obtained from the Monte-Carlo simulation, which uses the mean free path in the duct and the mean square of free path in the axial direction of the duct .

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