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A new helium mass spectrometer for leak tests, using a novel low pressure analysis cell
Classified Abstracts 919--925
378
24 919. A suggested range of vacuum valves of similar design and telecontroiled. (France) The author lays down a number of requirements which are met by the series in question (clear diameter ranging from 30 to 600 mm~, ~1) The operating mechanism is strong enough to deform the sealing material by the requisite amount. (2) The sealing material is securely located in suitable recess. (3) Deformation of slide or plunger in uniform. (4) The last stages of approach of plunger or slide is always perpendicular to the seat. Pneumatic telecontrol is provided. A reserve of compressed air ensures automatic closure in case of power failure. (France) W . J. S.
L. Maurice, Le Vide, 19 (110), March/April 1964, 57-59. 24 920. Gate, slide and throttle valves for vacuum circuits. (France) Representative examples of valves of various types in present use are described and illustrated. The special requirements of ultrahigh circuits are stressed. Especially for large aperture valves, the requisite tightness when closed is difficult to reconcile with the ability of the device to withstand high baking temperatures. The advantage of two walled circuits, both evacuated, with the inner one at the lower pressure are discussed. In this case the pressure difference across the valve can be reduced and their design simplified. (France) w. J. s. B. L. Blanc, Le Vide, 19 (110), March/April 1964, 26-37.
25.
Baffles, T r a p s and R e f r i g e r a t i o n E q u i p m e n t
25 921. Baffles, traps and methods of replenishing with coolant. (France) Baffles are fitted to the delivery side of diffusion pumps with the object of preventing the passage of pumping fluid into the recipient. The purpose of the trap is to stop back diffusion of any vapour present in the baffle, Both baffles and traps should be optically opaque and have as high a conductance as possible. Typical designs are illustrated. The effectiveness of the trap depends on its temperature and methods of supplying the coolant automatically are described. (France) w.J.s. J. Moreau, Le Vide, 19 (110), March/April 1964, 16-21.
26.
A u t o m a t i c P r o t e c t i v e and C o n t r o l E q u i p m e n t
26 922. Automatic level control for liquid nitrogen. (France) An electric circuit is described which will keep the level of liquid nitrogen in a vacuum device (e.g., a trap) constant as evaporation proceeds. The variation in level is measured by the change in electrical resistance of a carbon compact as it enters or leaves the surface of the liquid and thus undergoes a pronounced change in temperature. Constancy of level is ensured by suitable operation of a slide valve of special design placed in the circuit between the device and a store of liquid nitrogen under pressure. Depending on the capacity of the store the system can operate over long periods without requiring any attention. (France) w.J.s. J. Postif and J. Reynaud, Le Vide, 19 (110), March/April 1964, 22-25.
26 923. Safety devices and automization of vacuum pumping sets. (France) The author describes the various devices required to safeguard a pumping unit should there be a power failure or a sudden leak in the system. The author illustrates the problem by considering in detail a set operating continuously consisting of a mechanical fore pump followed by a secondary diffusion pump. Such an installation requires a number of valves for sealing off parts of the circuit in case of need, together with pressure gauges for this operation. In addition controls for cooling (water or air) have to be provided. The author points out that in order to guard against all eventualities, the control system becomes rather complex and this in its return may affect its reliability. A compromise has therefore to be accepted. A useful discussion on the subject concludes the article. (France) w.J.s. P. No6, Le Vide, 19 (111), May/June 1964, 146-153.
26 924. Protection against the entry of air into vacuum plants. (France) Particles extracted from an accelerator usually emerge through a window placed at the end of a straight and narrow channel. Such windows are fragile and their collapse will cause sudden entry of atmospheric air into the accelerator. A safety measure can be provided by a quick closing valve placed at the accelerator end of the tube. It is difficult to design such valves with a delay time of less than 20 m/see, which means that the distance to the window must be more than 6 m (sonic speed consumed) in order to effect closure in time. Such distances are impracticable for various reasons and the author shows how the delay time can be artificially increased by the insertion of conical baffles in the channel leading to the window. With only a small increase in diameter, a delay time of over 20 msec can be introduced into a 2 m connection and a quick closing v a n e of standard design employed. (France) w. J. s. R. Jean and R. Jauss, Le Vide, 19 (111), May/June 1964, 123-127.
26 925. Historical development and present state of vacuum switches. (Germany) As long ago as 1930, vacuum switches capable of cutting at a current of 15 kA in a power circuit of 450 MVA were available. Such switches had, however, a very short life. By improvements in the purity of the contact materials (freedom from occluded gas) the higher vacua (10 -7) reasonable performances are now possible, provided the field strength between the electrode is limited to 106-107 V/cm and any pinch effect avoided. Suitable design features are discussed. (Germany) w.J.s. K. Thiel, Vakuum Technik, 13 (4), May 1964, 116.
27.
L e a k D e t e c t o r s and L e a k D e t e c t i o n
27 : 33 A new helium mass spectrometer for leak tests, using a novel low pressure analysis cell. See Abstr, No. 935,
378
24 919. A suggested range of vacuum valves of similar design and telecontroiled. (France) The author lays down a number of requirements which are met by the series in question (clear diameter ranging from 30 to 600 mm~, ~1) The operating mechanism is strong enough to deform the sealing material by the requisite amount. (2) The sealing material is securely located in suitable recess. (3) Deformation of slide or plunger in uniform. (4) The last stages of approach of plunger or slide is always perpendicular to the seat. Pneumatic telecontrol is provided. A reserve of compressed air ensures automatic closure in case of power failure. (France) W . J. S.
L. Maurice, Le Vide, 19 (110), March/April 1964, 57-59. 24 920. Gate, slide and throttle valves for vacuum circuits. (France) Representative examples of valves of various types in present use are described and illustrated. The special requirements of ultrahigh circuits are stressed. Especially for large aperture valves, the requisite tightness when closed is difficult to reconcile with the ability of the device to withstand high baking temperatures. The advantage of two walled circuits, both evacuated, with the inner one at the lower pressure are discussed. In this case the pressure difference across the valve can be reduced and their design simplified. (France) w. J. s. B. L. Blanc, Le Vide, 19 (110), March/April 1964, 26-37.
25.
Baffles, T r a p s and R e f r i g e r a t i o n E q u i p m e n t
25 921. Baffles, traps and methods of replenishing with coolant. (France) Baffles are fitted to the delivery side of diffusion pumps with the object of preventing the passage of pumping fluid into the recipient. The purpose of the trap is to stop back diffusion of any vapour present in the baffle, Both baffles and traps should be optically opaque and have as high a conductance as possible. Typical designs are illustrated. The effectiveness of the trap depends on its temperature and methods of supplying the coolant automatically are described. (France) w.J.s. J. Moreau, Le Vide, 19 (110), March/April 1964, 16-21.
26.
A u t o m a t i c P r o t e c t i v e and C o n t r o l E q u i p m e n t
26 922. Automatic level control for liquid nitrogen. (France) An electric circuit is described which will keep the level of liquid nitrogen in a vacuum device (e.g., a trap) constant as evaporation proceeds. The variation in level is measured by the change in electrical resistance of a carbon compact as it enters or leaves the surface of the liquid and thus undergoes a pronounced change in temperature. Constancy of level is ensured by suitable operation of a slide valve of special design placed in the circuit between the device and a store of liquid nitrogen under pressure. Depending on the capacity of the store the system can operate over long periods without requiring any attention. (France) w.J.s. J. Postif and J. Reynaud, Le Vide, 19 (110), March/April 1964, 22-25.
26 923. Safety devices and automization of vacuum pumping sets. (France) The author describes the various devices required to safeguard a pumping unit should there be a power failure or a sudden leak in the system. The author illustrates the problem by considering in detail a set operating continuously consisting of a mechanical fore pump followed by a secondary diffusion pump. Such an installation requires a number of valves for sealing off parts of the circuit in case of need, together with pressure gauges for this operation. In addition controls for cooling (water or air) have to be provided. The author points out that in order to guard against all eventualities, the control system becomes rather complex and this in its return may affect its reliability. A compromise has therefore to be accepted. A useful discussion on the subject concludes the article. (France) w.J.s. P. No6, Le Vide, 19 (111), May/June 1964, 146-153.
26 924. Protection against the entry of air into vacuum plants. (France) Particles extracted from an accelerator usually emerge through a window placed at the end of a straight and narrow channel. Such windows are fragile and their collapse will cause sudden entry of atmospheric air into the accelerator. A safety measure can be provided by a quick closing valve placed at the accelerator end of the tube. It is difficult to design such valves with a delay time of less than 20 m/see, which means that the distance to the window must be more than 6 m (sonic speed consumed) in order to effect closure in time. Such distances are impracticable for various reasons and the author shows how the delay time can be artificially increased by the insertion of conical baffles in the channel leading to the window. With only a small increase in diameter, a delay time of over 20 msec can be introduced into a 2 m connection and a quick closing v a n e of standard design employed. (France) w. J. s. R. Jean and R. Jauss, Le Vide, 19 (111), May/June 1964, 123-127.
26 925. Historical development and present state of vacuum switches. (Germany) As long ago as 1930, vacuum switches capable of cutting at a current of 15 kA in a power circuit of 450 MVA were available. Such switches had, however, a very short life. By improvements in the purity of the contact materials (freedom from occluded gas) the higher vacua (10 -7) reasonable performances are now possible, provided the field strength between the electrode is limited to 106-107 V/cm and any pinch effect avoided. Suitable design features are discussed. (Germany) w.J.s. K. Thiel, Vakuum Technik, 13 (4), May 1964, 116.
27.
L e a k D e t e c t o r s and L e a k D e t e c t i o n
27 : 33 A new helium mass spectrometer for leak tests, using a novel low pressure analysis cell. See Abstr, No. 935,