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11. Production of low pressures
Classified abstracts Classified
abstracts
505704
505511 on this page
Editor’s note The label immediately following the title of each item denotes country or origin end of each absfracf indicafes country of origin of work (where known).
I. General
vacuum
science
and engineering
10. VACUUM SCIENCE AND TECHNOLOGY 10 505. High vacuum. (Bulgaria) This book deals with basic principles of producing and measuring high vacuum and with designing high vacuum apparatus. Some modern methods are described, but greatest coverage is given to older techniques (eg tables of data on Soviet pumps, leak detection methodes, applications of high vacuum). The given explanations are clearly presented. A table of flange standards and many references are included. (Bulgaria) V G Kanev and G Y Grigorov, Book, publd by Tekhnika. Sofia, 1965, 461 pages (in Bulgarian-original
title:
Visok Vakuum).
11. PRODUCTION OF LOW PRESSURES 11 : 14 506. A review of the molecular flow conductance for systems of tubes and components and the measurement of pumping speed. (Great Britain) The definition of molecular flow conductance for tubes and components is considered and the calculation of the conductance of long tubes with differently shaped cross-sections reviewed. The conductance and transmission probability for short tubes is discussed in relation to Clausing type integral equations and their approximate solutions. A review is given of theoretical and experimental investigations of molecular gas flow emission patterns for tubes and components. An estimation for the effective transmission probability and conductance of more complex systems, particularly of tubes, diaphragms, baffles etc. connected in series, is considered as well as their experimental determination using models and statistical Monte Carlo type methods for their more accurate calculation. The definition of pumping speed and the development of different procedures which have been adopted in recent years for its measurement under molecular flow conditions are reviewed. It has been shown that the difficulty in the various methods was associated with the determination of the pressure at the mouth of the pump which depended on a number of inter-related factors. The most important of these concerned the design and dimensions of the test dome which it is necessary to attach to the pump, the position and distribution of gas entry to this dome as well as the method and place of pressure measurement. The physical interpretation of speeds measured with various arrangements is discussed in relation to recent proposals of a test dome arrangement which forms the basis for an internationally agreed standard for pump speed specification. (Author) W Steckelmacher, Vacuum, 16 (ll), Nov 1966, 561-584. 14. KINETIC THEORY OF GASES 14 : 11 A review of the molecular flow conductance for systems of tubes and components and the measurement of pumping speed. See abstract number 506. 14 507. An evaluation of the performance of gas flow meters which use a porous membrane as the control element. (Great Britain) Results are presented on the suitability of a porous membrane as the basic element for the control and measurement of gas flow into a vacuum system, A porous plug of silicon carbide is shown to have a very low conductance, of the order of lode litres set-’ for argon, and to be stable over a long period of time. The Knudsen laws of molecular flow are obeyed up to pressures in excess of 100 torr, ie flow is proportional to pressure difference up to at least 100 torr for most
of publicafion,
and that at fhe
gases, and also inversely proportional to the square root of the gas molecular weight. It is estimated that a high accuracy of measurement, to the order of &l per cent can be maintained for flow rates down to lo-* litres torr set-‘. (Authors) R G Christian et al, Vacuum, 16 (I I), Nov 1966, 609-61 I. 14 :22 508. Experiments on the molecular Row of gas through tubes and vacuum system components using a B.A. ionization gauge. (Great Britain) Experiments have been made to determine the density distribution of gas beams issuing under conditions of molecular flow from tubes and vacuum components exposed to a gas in a random state. Argon was used to avoid sorption effects in the vacuum components and beam detector. The investigations have been divided into two parts. In the first the behaviour was studied of a Bayard-Alpert gauge when used for measuring the density of gas beams. It is shown that the beam density in the detector is enhanced by the presence of the gauge envelope enclosing the ionization system and that the enhancement factor depends critically on the envelope and electrode geometry and the angle of incidence of the gas beam. In the second part of the work the Bayard-Alpert gauge was used for measuring the density of gas beams from apertures, tubes and vacuum couplings. It is shown that the density distributions for apertures, short and long tubes, which have been theoretically derived by several workers, are only experimentally verified when the diameters of the detector aperture and gas source are
abstracts
505704
505511 on this page
Editor’s note The label immediately following the title of each item denotes country or origin end of each absfracf indicafes country of origin of work (where known).
I. General
vacuum
science
and engineering
10. VACUUM SCIENCE AND TECHNOLOGY 10 505. High vacuum. (Bulgaria) This book deals with basic principles of producing and measuring high vacuum and with designing high vacuum apparatus. Some modern methods are described, but greatest coverage is given to older techniques (eg tables of data on Soviet pumps, leak detection methodes, applications of high vacuum). The given explanations are clearly presented. A table of flange standards and many references are included. (Bulgaria) V G Kanev and G Y Grigorov, Book, publd by Tekhnika. Sofia, 1965, 461 pages (in Bulgarian-original
title:
Visok Vakuum).
11. PRODUCTION OF LOW PRESSURES 11 : 14 506. A review of the molecular flow conductance for systems of tubes and components and the measurement of pumping speed. (Great Britain) The definition of molecular flow conductance for tubes and components is considered and the calculation of the conductance of long tubes with differently shaped cross-sections reviewed. The conductance and transmission probability for short tubes is discussed in relation to Clausing type integral equations and their approximate solutions. A review is given of theoretical and experimental investigations of molecular gas flow emission patterns for tubes and components. An estimation for the effective transmission probability and conductance of more complex systems, particularly of tubes, diaphragms, baffles etc. connected in series, is considered as well as their experimental determination using models and statistical Monte Carlo type methods for their more accurate calculation. The definition of pumping speed and the development of different procedures which have been adopted in recent years for its measurement under molecular flow conditions are reviewed. It has been shown that the difficulty in the various methods was associated with the determination of the pressure at the mouth of the pump which depended on a number of inter-related factors. The most important of these concerned the design and dimensions of the test dome which it is necessary to attach to the pump, the position and distribution of gas entry to this dome as well as the method and place of pressure measurement. The physical interpretation of speeds measured with various arrangements is discussed in relation to recent proposals of a test dome arrangement which forms the basis for an internationally agreed standard for pump speed specification. (Author) W Steckelmacher, Vacuum, 16 (ll), Nov 1966, 561-584. 14. KINETIC THEORY OF GASES 14 : 11 A review of the molecular flow conductance for systems of tubes and components and the measurement of pumping speed. See abstract number 506. 14 507. An evaluation of the performance of gas flow meters which use a porous membrane as the control element. (Great Britain) Results are presented on the suitability of a porous membrane as the basic element for the control and measurement of gas flow into a vacuum system, A porous plug of silicon carbide is shown to have a very low conductance, of the order of lode litres set-’ for argon, and to be stable over a long period of time. The Knudsen laws of molecular flow are obeyed up to pressures in excess of 100 torr, ie flow is proportional to pressure difference up to at least 100 torr for most
of publicafion,
and that at fhe
gases, and also inversely proportional to the square root of the gas molecular weight. It is estimated that a high accuracy of measurement, to the order of &l per cent can be maintained for flow rates down to lo-* litres torr set-‘. (Authors) R G Christian et al, Vacuum, 16 (I I), Nov 1966, 609-61 I. 14 :22 508. Experiments on the molecular Row of gas through tubes and vacuum system components using a B.A. ionization gauge. (Great Britain) Experiments have been made to determine the density distribution of gas beams issuing under conditions of molecular flow from tubes and vacuum components exposed to a gas in a random state. Argon was used to avoid sorption effects in the vacuum components and beam detector. The investigations have been divided into two parts. In the first the behaviour was studied of a Bayard-Alpert gauge when used for measuring the density of gas beams. It is shown that the beam density in the detector is enhanced by the presence of the gauge envelope enclosing the ionization system and that the enhancement factor depends critically on the envelope and electrode geometry and the angle of incidence of the gas beam. In the second part of the work the Bayard-Alpert gauge was used for measuring the density of gas beams from apertures, tubes and vacuum couplings. It is shown that the density distributions for apertures, short and long tubes, which have been theoretically derived by several workers, are only experimentally verified when the diameters of the detector aperture and gas source are