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1466. High-vacuum valve for shock-tube application
Classified
abstracts
1461-1473
22 (Great Britain) A description is given of a form of mercury manometer which has the measurement arms in line with each other, has a very rigid construction and yet a loss in working range of only 3.5 cm. Where a cathetometer is used and where a large number of accurate readings must be made, such an instrument may save time and effort and diminish sources of error. F Akerboom and H H van Mal, J Sci Instrum, Ser 2, 1 (6), 1968, 689690. 22 1462. The absolute calibration of gauges for tritium gas in the pressure range 1O-8 to 1O-5 torr. (Great Britain) A procedure for the absolute calibration of vacuum gauges for tritium gas is described. The method depends upon measuring the radioactive decay current generated by a known volume of tritium. Calibrations, in the pressure range lo-@ to 1O-5 torr, are presented for a mass analyzer and an ionization gauge which are commercially available. M R Barnes and A Gibson, Vacuum, 18 (8), August 1968,451-455. 1461. An improved form of mercury manometer.
23. PLUMBING
23 : 33 A flat membrane inflatable gasket for a large liquid hydrogen bubble chamber. See abstract number 1492. 23 : 34 1463. Lubrication of sliding and rolling element electrical contacts in vacuum. (USA) Sliding electrical contact problems in vacuum, and recent experiments in this field, are reviewed in regard to the lubricants used. Attention is given to the relationship between surface contamination and the wear of graphite. Organic lubrication is considered to be an undesirable method of lubricating electrical contacts, on the basis of the friction polymer data examined. Thin, metallic films are seen as a promising method of contact lubrication, and several methods of depositing these films are presented. J Przybyszewski, Rep NASA-TM-X-52382, May 1968, 34 pages (Sci Tech Aerospace
plunger and Viton O-ring. The shortcomings of a greased stopcock are overcome. J Frazer and R K Stomp, Rep UCRL-50317, Sept 1967, 6 pages (Sci Tech Aerospace Reps, 6 (8), 1143, N68-18041). 25. BAFFLES, TRAPS AND REFRIGERATION EQUIPMENT
25 1468. An automated, variable temperature condensation trap. (USA) A variable temperature cold trap, utilizing liquid nitrogen as a coolant and a resistance thermometer as a detector, was designed for use in vacuum analytical and synthesis chemistry. The trap consists of a glass U-tube, with both legs encased in Cu tubing. Temperature can be varied from - 180°C to lOO”C, and the trap may be computer controlled. R K Stump and J W Frazer, Rep UCRL-50318, Sept (Sci Tech Aerospace Reps, 6 (8), 1143, N-68-l 8042).
1967, 5 pages
25 1469. Ultimate pressure obtained by adsorbing air on activated charcoal cooled with liquid nitrogen. (Great Britain) Results are given of the determination of the residual air pressure over a charcoal adsorbent when desorption of gases from the walls of the vacuum system is prevented. In this case a pressure of 5 x lo-@ torr was reached in the system. (USSR) B G Lazarev et al, Cryogenics, 8 (3), 1968, 172. 27. LEAK DETECTORS AND LEAK DETECTION
27 1470. Leak detection in sealed off vacuum devices. (Great Britain) The reasons for leak testing individual components of electronic valves during their manufacture are reviewed. Where a large variety of components is to be tested, practical considerations lead to the use of several universal jigs and fixtures, and the more generally applicable of these are described. A description of methods used, and the difficulties which can arise, is given. Finally, the sensitivity of presentday leak detection methods is critically examined, and it is concluded that, for the type of work under review, the helium mass spectrometer leak detector is highly satisfactory. D J Thorpe, Vacuum, 18 (8), August 1968, 44-444.
Reps, 6 (7), 1003, N68-16665). 23
1464. Bearings and seals for cryogenic fluids.
(USA) The bearing load carrying surfaces are lubricated by thin transfer films, the lubricant being provided by the bearing cage which is of Teflon. H W Scibbe, Rep NASA-TM-X-52415, 1968, 39 pages (Sri Tech Aerospace Reps, 6 (8), 1183, N68-18124). 23 1465. Cryogenic lead-seals. (Great Britain) Three types of seals are described and evaluated; a seal with 20 copper rods (l/16 inch) cast into the male portion of a It-inch Specdivac union with Stycast resin; another with the rods passing through a thick copper block with Viton O-rings and PTFE insulators; and a third with the rods cemented with Stycast into holes drilled in the copper block. T Ashworth et al, Cryogenics, 8 (3), 1968, 167-168.
28. HEATING EQUIPMENT
AND THERMOMETERS
28 : 34 Accurate surface temperature measurements at liquid helium conditions in space environment facilities. See abstract number 1504. 28 1471. The thermal equilibrium of wires in hot gas streams. (Great Britain) The thermal equilibrium of wires in hot gases is discussed both generally and as applied particularly to thermocouples. The estimation of the radiation correction is considered with special reference to methods available for determining the emissivity of a metal wire coated with silica to eliminate catalytic effects. In the case of a silicacoated platinum/platinum-rhodium thermocouple, three different methods are shown to give concordant results for the emissivity. Formulae are presented by which the correction may be estimated. K N Bascombe, Rep ERDE-TM-11/M/66; WAG/174/012, Aug 1966, 28 pages (Sci Tech Aerospace
Reps, 6 (8), 1255, N68-17305). 28
1472. Some properties of gold-iron thermocouple
24. VALVES 24 : 34 Study of propellant valve leakage in a vacuum. See abstract number 1505. 24 1466. High-vacuum valve for shock-tube application. (Great Britain) A valve is described which is suitable for use in the low pressure section of a shock-tube. As well as being capable of withstanding the pressures obtained in such a device, it can maintain high vacuum, high gas purity and utilize the fullest capacity of the evacuation pumps. I G Crow, J Sci Instrum, Ser 2, 1 (6), 1968, 666-667. 24 1467. A hermetically sealed, high vacuum glass valve. (USA) A hermetically sealed glass valve was designed to automate the vacuum analytical system in a chemistry laboratory using a computer. The valve incorporates a glass body, stainless steel bellows, Teflon
610
wire.
(USA) Gold wire with nominal 0.02 atomic per cent iron has been calibrated vs Chromel-P from 0.4 to 85°K. The high sensitivity of this dilute solution, its reproducibility upon cycling from room temperature, and stability upon ageing were favourably confirmed. R L Rosenbaum, Rev Sci Instrum, 39 (6), 1968, 890-899.
III.
Vacuum
applications
30. EVAPORATION
AND SPUTTERING 30 : 33
High
resolution
electron
microscopy
of biological
specimens.
See
abstract number 1494. 30 1473. Low energy diffraction
apparatus
designed
for thin film use.
(USA)
For the study of epitaxial films by LEED it has been necessary to
abstracts
1461-1473
22 (Great Britain) A description is given of a form of mercury manometer which has the measurement arms in line with each other, has a very rigid construction and yet a loss in working range of only 3.5 cm. Where a cathetometer is used and where a large number of accurate readings must be made, such an instrument may save time and effort and diminish sources of error. F Akerboom and H H van Mal, J Sci Instrum, Ser 2, 1 (6), 1968, 689690. 22 1462. The absolute calibration of gauges for tritium gas in the pressure range 1O-8 to 1O-5 torr. (Great Britain) A procedure for the absolute calibration of vacuum gauges for tritium gas is described. The method depends upon measuring the radioactive decay current generated by a known volume of tritium. Calibrations, in the pressure range lo-@ to 1O-5 torr, are presented for a mass analyzer and an ionization gauge which are commercially available. M R Barnes and A Gibson, Vacuum, 18 (8), August 1968,451-455. 1461. An improved form of mercury manometer.
23. PLUMBING
23 : 33 A flat membrane inflatable gasket for a large liquid hydrogen bubble chamber. See abstract number 1492. 23 : 34 1463. Lubrication of sliding and rolling element electrical contacts in vacuum. (USA) Sliding electrical contact problems in vacuum, and recent experiments in this field, are reviewed in regard to the lubricants used. Attention is given to the relationship between surface contamination and the wear of graphite. Organic lubrication is considered to be an undesirable method of lubricating electrical contacts, on the basis of the friction polymer data examined. Thin, metallic films are seen as a promising method of contact lubrication, and several methods of depositing these films are presented. J Przybyszewski, Rep NASA-TM-X-52382, May 1968, 34 pages (Sci Tech Aerospace
plunger and Viton O-ring. The shortcomings of a greased stopcock are overcome. J Frazer and R K Stomp, Rep UCRL-50317, Sept 1967, 6 pages (Sci Tech Aerospace Reps, 6 (8), 1143, N68-18041). 25. BAFFLES, TRAPS AND REFRIGERATION EQUIPMENT
25 1468. An automated, variable temperature condensation trap. (USA) A variable temperature cold trap, utilizing liquid nitrogen as a coolant and a resistance thermometer as a detector, was designed for use in vacuum analytical and synthesis chemistry. The trap consists of a glass U-tube, with both legs encased in Cu tubing. Temperature can be varied from - 180°C to lOO”C, and the trap may be computer controlled. R K Stump and J W Frazer, Rep UCRL-50318, Sept (Sci Tech Aerospace Reps, 6 (8), 1143, N-68-l 8042).
1967, 5 pages
25 1469. Ultimate pressure obtained by adsorbing air on activated charcoal cooled with liquid nitrogen. (Great Britain) Results are given of the determination of the residual air pressure over a charcoal adsorbent when desorption of gases from the walls of the vacuum system is prevented. In this case a pressure of 5 x lo-@ torr was reached in the system. (USSR) B G Lazarev et al, Cryogenics, 8 (3), 1968, 172. 27. LEAK DETECTORS AND LEAK DETECTION
27 1470. Leak detection in sealed off vacuum devices. (Great Britain) The reasons for leak testing individual components of electronic valves during their manufacture are reviewed. Where a large variety of components is to be tested, practical considerations lead to the use of several universal jigs and fixtures, and the more generally applicable of these are described. A description of methods used, and the difficulties which can arise, is given. Finally, the sensitivity of presentday leak detection methods is critically examined, and it is concluded that, for the type of work under review, the helium mass spectrometer leak detector is highly satisfactory. D J Thorpe, Vacuum, 18 (8), August 1968, 44-444.
Reps, 6 (7), 1003, N68-16665). 23
1464. Bearings and seals for cryogenic fluids.
(USA) The bearing load carrying surfaces are lubricated by thin transfer films, the lubricant being provided by the bearing cage which is of Teflon. H W Scibbe, Rep NASA-TM-X-52415, 1968, 39 pages (Sri Tech Aerospace Reps, 6 (8), 1183, N68-18124). 23 1465. Cryogenic lead-seals. (Great Britain) Three types of seals are described and evaluated; a seal with 20 copper rods (l/16 inch) cast into the male portion of a It-inch Specdivac union with Stycast resin; another with the rods passing through a thick copper block with Viton O-rings and PTFE insulators; and a third with the rods cemented with Stycast into holes drilled in the copper block. T Ashworth et al, Cryogenics, 8 (3), 1968, 167-168.
28. HEATING EQUIPMENT
AND THERMOMETERS
28 : 34 Accurate surface temperature measurements at liquid helium conditions in space environment facilities. See abstract number 1504. 28 1471. The thermal equilibrium of wires in hot gas streams. (Great Britain) The thermal equilibrium of wires in hot gases is discussed both generally and as applied particularly to thermocouples. The estimation of the radiation correction is considered with special reference to methods available for determining the emissivity of a metal wire coated with silica to eliminate catalytic effects. In the case of a silicacoated platinum/platinum-rhodium thermocouple, three different methods are shown to give concordant results for the emissivity. Formulae are presented by which the correction may be estimated. K N Bascombe, Rep ERDE-TM-11/M/66; WAG/174/012, Aug 1966, 28 pages (Sci Tech Aerospace
Reps, 6 (8), 1255, N68-17305). 28
1472. Some properties of gold-iron thermocouple
24. VALVES 24 : 34 Study of propellant valve leakage in a vacuum. See abstract number 1505. 24 1466. High-vacuum valve for shock-tube application. (Great Britain) A valve is described which is suitable for use in the low pressure section of a shock-tube. As well as being capable of withstanding the pressures obtained in such a device, it can maintain high vacuum, high gas purity and utilize the fullest capacity of the evacuation pumps. I G Crow, J Sci Instrum, Ser 2, 1 (6), 1968, 666-667. 24 1467. A hermetically sealed, high vacuum glass valve. (USA) A hermetically sealed glass valve was designed to automate the vacuum analytical system in a chemistry laboratory using a computer. The valve incorporates a glass body, stainless steel bellows, Teflon
610
wire.
(USA) Gold wire with nominal 0.02 atomic per cent iron has been calibrated vs Chromel-P from 0.4 to 85°K. The high sensitivity of this dilute solution, its reproducibility upon cycling from room temperature, and stability upon ageing were favourably confirmed. R L Rosenbaum, Rev Sci Instrum, 39 (6), 1968, 890-899.
III.
Vacuum
applications
30. EVAPORATION
AND SPUTTERING 30 : 33
High
resolution
electron
microscopy
of biological
specimens.
See
abstract number 1494. 30 1473. Low energy diffraction
apparatus
designed
for thin film use.
(USA)
For the study of epitaxial films by LEED it has been necessary to