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58. A simple partial pressure gauge
Classified'abstracts-54~4 22 54, Logarithmic pen recording of mass peaks for an AEI Type M S 2 H
mass spectrometer.
(Great Britain)
J J Wijnbergen et al, JScilnstrum, 41 (9), Sept 1964, 574-575. 22 : 14 55, Thermal molecular manometer according to H Klumb fitted with
magnetic suspension.
(Germany)
The principle underlying the construction of this m a n o m e t e r was 13 (6), Dec 1964, 179-185, abstract 1207). The present instalment gives further details of the dynamics of the system and establishes the necessary equations for equilibrium, restoring m o m e n t and sensitivity. Direct calibration with a McLeod m a n o m e t e r showed a satisfactory agreement with theoretical predictions at pressures of the order of 10 -3 torr. It is t h o u g h t possible to extend the range of this instrument to 10 torr by altering the restoring couple and increasing the temperature of the heating element. A l t h o u g h less sensitive to mechanical vibration t h a n normal molecular m o n o meters, the magnetic suspension introduces other difficulties, mainly connected with uncontrolled variation of the magnetic field. In order to ensure consistency of operation over a period, elaborate magnetic shielding m a y prove necessary. (Germany) W JS Bibliography 4 items. R Hofmann and E Weissmann, Vak Technik, 13 (8), Dec 1964,
241-247. 22 56. Alpha-ray vacuum gauge. (Great Britain) Anon Engineer, 218 (5666), 28 Aug [964,343. 22:21 57. Error in the reading of compression mercury manometers caused by the streaming of mercury vapour. (USSR) The a u t h o r has demonstrated with the help of a mass filter the existence of a pressure difference between a mercury compression m a n o m e t e r and a cold trap separating it f r o m the rest of the system. In order to avoid this error, it is recommended that the entire system, including the m a n o m e t e r be kept below 2°C. Since in the past, the mercury compression m a n o m e t e r has been extensively used to calibrate other types without taking this precaution, it m a y become necessary to revise the values of a n u m b e r of physical constants. (USSR) L P Khavkin, Pribory i Tekh Eksper, (5), 1964, 161-167. 22 58. A simple partial pressure gauge. (USA) A simple 180 ° mass spectrometer is described with a resolution of about 50. It is small, robust and can be easily outgassed and will record partial pressure as low as 2 × 10 -11 torr. The instrument is available commercially and the sensitivity and resolution do not vary by more than I0 per cent for different samples. L Goldstone, Rev Sci Instrum, 35 (10), Oct 1964, 1265-1268.
22 59. A new diaphragm vacuum gauge. (Japan) The deflection of an invar steel d i a p h r a g m is measured by means of a silicon resistance strain gauge m o u n t e d on the disc. Pressure range extends from 1 atmosphere to 1 tort. C Hayashi and O Tsukakoshi, ,lap J Appl Phys, 3 (7), July 1964,
23
62. Seal for electron optical instrument.
(Great Britain)
The article describes the stages in the development of the design of a leakproof valve for a chamber in an electron optical instrument, in order to demonstrate that first ideas are not always the best and that attention to detail m a y result in a greatly improved design. The v a c u u m valve, which was an " O " ring seal, was required to move laterally and the total available height for it was only 0.120 in. Moreover, to avoid u n d u e wear of the " O " ring, it had to be lifted vertically prior to the lateral movement; only 0.015 in. was left for the " O " ring and its m o u n t i n g and of this the " O " ring occupied 0.070 in. It was intended that m o v e m e n t should take place with a v a c u u m on both sides of the seal but after closure air would be admitted to the upper side and no leakage could be permitted to the lower side. Difficulty was experienced in controling the alignm e n t of the " O " ring m o u n t with respect to the valve seat with the result that some leakage occurred before the pressure difference corrected the misalignment. It was therefore necessary to take the valve self-adjusting and it was proposed to do this [:y providing the " O " ring m o u n t i n g with some f o r m of independent suspension. The first attempt was to m a k e the m o u n t i n g plate more flexible by machining a circular groove in it, but this was not satisfactory and it was calculated that replacing the brass BS 249 by p h o s p h u r bronze would still not give adequate flexibility. The second m e t h o d suggested was to machine 3 circular slots, each of are length 105 °, separated by"bridges"; this gave greater flexibility but was more difficult to m a n u f a c t u r e and was mechanically weak. In the third method the " O " ring was m o u n t e d on a p h o s p h o r bronze disc which was soft-soldered at the centre to the brass plate. This led to m a n u f a c t u r i n g difficulties and a modified assembly technique was adopted in m e t h o d 4 which proved to be satisfactory. Nevertheless further consideration led to the adoption of a still later design which required a smaller n u m b e r of machining operations and had a n u m b e r of advantages in performance. The final design proved to be an efficient reliable seal which did not require special care in m a n u f a c t u r e or assembly. (Great Britain) JN J M Sturrock, Engineer, 218 (5671), 2 Oct 1964, 546-547.
24. Valves 24
63. Vacuum seal. (USSR) The standard v a c u u m film coating unit uses a mercury diffusion p u m p connected to the glass base plate of the receiver by means of a normal glass seal. The replacement of the mercury diffusion p u m p with an oil diffusion p u m p with a metal case necessitated a special f o r m of connection to the base plate. The new seal, which consists of these parts (body, valve and operating mechanism) is described in detail. Several advantages in operation over its predecessor are claimed (fewer movable parts in the v a c u u m etc).
(USSR) A A Ahukov and E T Taldaev, Pribory i Tekh Eksper, (5), 1964,
194-195.
25. Baffles, traps and refrigeration equipment
425-428.
25
64. Cryogenic refrigerator. (USA) W H Hogan and R W Stuart, MechanicalEngng, 86 (10), Oct 1964,
23. Plumbing
18-20. 23:41
60. Method of soldering vacuum steel pipes. (USSR) A layer of iron carbide (FzC) obtained by local high temperature gas carbonization is used as solder. The carbide is in the f o r m of a ring, 0.1 to 0.2 m m thick, placed inside the tubes at a short distance f r o m the preliminary weld (1000°C). The temperature is then raised to the melting point of the ring, when the now liquid cemenrite will penetrate any cavities at the joint. (USSR) E V Uganson et al, Patent No. 159361 (USSR), Bulletin No. 24,
published 7 Dec 1963. 23 : 27 61. Protection of metal-glass seals against corrosion by penetration of humidity into the solder. (USSR) Protection is achieved by covering the joint with a thin film of glass which is securely anchored on the metal part of the connection. A A Belousov, Patent No. 164879/24-7/ (USSR), Bulletin No. 5,
published 26 Nov 1964.
27. Leak detectors and leak detection 27 Protection of metal to glass seals against corrosion by penetration of humidity into the solder. See Abstr. No. 61.
III. Vacuum applications 30. Evaporation and sputtering 3O On the synthesis of dielectric multilayer coatings. See Abstr. No. 42. 30
Vacuum study of optical properties of thin films of refractory metals. See Abstr. No. 45.
45
mass spectrometer.
(Great Britain)
J J Wijnbergen et al, JScilnstrum, 41 (9), Sept 1964, 574-575. 22 : 14 55, Thermal molecular manometer according to H Klumb fitted with
magnetic suspension.
(Germany)
The principle underlying the construction of this m a n o m e t e r was 13 (6), Dec 1964, 179-185, abstract 1207). The present instalment gives further details of the dynamics of the system and establishes the necessary equations for equilibrium, restoring m o m e n t and sensitivity. Direct calibration with a McLeod m a n o m e t e r showed a satisfactory agreement with theoretical predictions at pressures of the order of 10 -3 torr. It is t h o u g h t possible to extend the range of this instrument to 10 torr by altering the restoring couple and increasing the temperature of the heating element. A l t h o u g h less sensitive to mechanical vibration t h a n normal molecular m o n o meters, the magnetic suspension introduces other difficulties, mainly connected with uncontrolled variation of the magnetic field. In order to ensure consistency of operation over a period, elaborate magnetic shielding m a y prove necessary. (Germany) W JS Bibliography 4 items. R Hofmann and E Weissmann, Vak Technik, 13 (8), Dec 1964,
241-247. 22 56. Alpha-ray vacuum gauge. (Great Britain) Anon Engineer, 218 (5666), 28 Aug [964,343. 22:21 57. Error in the reading of compression mercury manometers caused by the streaming of mercury vapour. (USSR) The a u t h o r has demonstrated with the help of a mass filter the existence of a pressure difference between a mercury compression m a n o m e t e r and a cold trap separating it f r o m the rest of the system. In order to avoid this error, it is recommended that the entire system, including the m a n o m e t e r be kept below 2°C. Since in the past, the mercury compression m a n o m e t e r has been extensively used to calibrate other types without taking this precaution, it m a y become necessary to revise the values of a n u m b e r of physical constants. (USSR) L P Khavkin, Pribory i Tekh Eksper, (5), 1964, 161-167. 22 58. A simple partial pressure gauge. (USA) A simple 180 ° mass spectrometer is described with a resolution of about 50. It is small, robust and can be easily outgassed and will record partial pressure as low as 2 × 10 -11 torr. The instrument is available commercially and the sensitivity and resolution do not vary by more than I0 per cent for different samples. L Goldstone, Rev Sci Instrum, 35 (10), Oct 1964, 1265-1268.
22 59. A new diaphragm vacuum gauge. (Japan) The deflection of an invar steel d i a p h r a g m is measured by means of a silicon resistance strain gauge m o u n t e d on the disc. Pressure range extends from 1 atmosphere to 1 tort. C Hayashi and O Tsukakoshi, ,lap J Appl Phys, 3 (7), July 1964,
23
62. Seal for electron optical instrument.
(Great Britain)
The article describes the stages in the development of the design of a leakproof valve for a chamber in an electron optical instrument, in order to demonstrate that first ideas are not always the best and that attention to detail m a y result in a greatly improved design. The v a c u u m valve, which was an " O " ring seal, was required to move laterally and the total available height for it was only 0.120 in. Moreover, to avoid u n d u e wear of the " O " ring, it had to be lifted vertically prior to the lateral movement; only 0.015 in. was left for the " O " ring and its m o u n t i n g and of this the " O " ring occupied 0.070 in. It was intended that m o v e m e n t should take place with a v a c u u m on both sides of the seal but after closure air would be admitted to the upper side and no leakage could be permitted to the lower side. Difficulty was experienced in controling the alignm e n t of the " O " ring m o u n t with respect to the valve seat with the result that some leakage occurred before the pressure difference corrected the misalignment. It was therefore necessary to take the valve self-adjusting and it was proposed to do this [:y providing the " O " ring m o u n t i n g with some f o r m of independent suspension. The first attempt was to m a k e the m o u n t i n g plate more flexible by machining a circular groove in it, but this was not satisfactory and it was calculated that replacing the brass BS 249 by p h o s p h u r bronze would still not give adequate flexibility. The second m e t h o d suggested was to machine 3 circular slots, each of are length 105 °, separated by"bridges"; this gave greater flexibility but was more difficult to m a n u f a c t u r e and was mechanically weak. In the third method the " O " ring was m o u n t e d on a p h o s p h o r bronze disc which was soft-soldered at the centre to the brass plate. This led to m a n u f a c t u r i n g difficulties and a modified assembly technique was adopted in m e t h o d 4 which proved to be satisfactory. Nevertheless further consideration led to the adoption of a still later design which required a smaller n u m b e r of machining operations and had a n u m b e r of advantages in performance. The final design proved to be an efficient reliable seal which did not require special care in m a n u f a c t u r e or assembly. (Great Britain) JN J M Sturrock, Engineer, 218 (5671), 2 Oct 1964, 546-547.
24. Valves 24
63. Vacuum seal. (USSR) The standard v a c u u m film coating unit uses a mercury diffusion p u m p connected to the glass base plate of the receiver by means of a normal glass seal. The replacement of the mercury diffusion p u m p with an oil diffusion p u m p with a metal case necessitated a special f o r m of connection to the base plate. The new seal, which consists of these parts (body, valve and operating mechanism) is described in detail. Several advantages in operation over its predecessor are claimed (fewer movable parts in the v a c u u m etc).
(USSR) A A Ahukov and E T Taldaev, Pribory i Tekh Eksper, (5), 1964,
194-195.
25. Baffles, traps and refrigeration equipment
425-428.
25
64. Cryogenic refrigerator. (USA) W H Hogan and R W Stuart, MechanicalEngng, 86 (10), Oct 1964,
23. Plumbing
18-20. 23:41
60. Method of soldering vacuum steel pipes. (USSR) A layer of iron carbide (FzC) obtained by local high temperature gas carbonization is used as solder. The carbide is in the f o r m of a ring, 0.1 to 0.2 m m thick, placed inside the tubes at a short distance f r o m the preliminary weld (1000°C). The temperature is then raised to the melting point of the ring, when the now liquid cemenrite will penetrate any cavities at the joint. (USSR) E V Uganson et al, Patent No. 159361 (USSR), Bulletin No. 24,
published 7 Dec 1963. 23 : 27 61. Protection of metal-glass seals against corrosion by penetration of humidity into the solder. (USSR) Protection is achieved by covering the joint with a thin film of glass which is securely anchored on the metal part of the connection. A A Belousov, Patent No. 164879/24-7/ (USSR), Bulletin No. 5,
published 26 Nov 1964.
27. Leak detectors and leak detection 27 Protection of metal to glass seals against corrosion by penetration of humidity into the solder. See Abstr. No. 61.
III. Vacuum applications 30. Evaporation and sputtering 3O On the synthesis of dielectric multilayer coatings. See Abstr. No. 42. 30
Vacuum study of optical properties of thin films of refractory metals. See Abstr. No. 45.
45