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Thin formvar coated counter windows
Classified
abstracts
1986-1999
23 1986. Thin formvar coated counter windows. (Netherlands) By coating pyroxylin films with formvar a pressure tight window can be produced that will stand up better under roughing and venting of the vacuum system than the same thickness of pure pyroxylin. The technique used to prepare these windows is described. A typical thickness of 45 /cg/cm”, with a surface area of 0.2 square inches will withstand a pressure of 100 torr. R A Morrison and K A Reed, NIICI I~~str.~nt Methods, 53 (I), JII!,, 1Y67, 173-174. 22 1987. Modified McLeod gauge eliminates measurement errors. (USA) Conventional McLeod gauges are subject to errors due to diffusion of mercury, particularly when a cold trap is used. A method is described to overcome this difficulty by inserting a magnetically operated valve between the mercury reservoir and the sample chamber. M C Kells, Fusion, 14 (2), 1967, 19-20. 22 1988. Modified McLeod
gauge records automatically.
(USA)
A modified McLeod gauge which records measurements automatically and can be programmed in advance by means of an automatic timer is described. The system consists of the gauge, an air/vacuum pumping device, and appropriate circuitry to cycle the pumping device. The gauge - - is a modification of the McLeod gauge - _ which indicates the pressure by the change in resistance of two platinum wires, contacted by the columns of mercury. The construction of the device and its operation is described. P A Faeth, Fusion, 14 (2), 1967, 21-23. 1989. In-chamber vacuum gauge calibration to cryopumping measurements. (USA)
22 method and its application
The report describes a method of calibrating mass spectrometers and ion gauges for pumping speed measurements. Sensitivity factors and pumping speed constants are determined from an analysis of the chamber pressures during gauge calibration and pumping speed measurements. The CO, sensitivity factor for the ion gauge or mass spectrometer is obtained. The pumping speed of a 77°K surface was determined for 300°K CO,. R M Freeman, Rep AEDC-TR-66-234; AD-645509, Jan 1967 (AR0 Itlc, Arnold Air Force Station. Terrrressee). 22 : 33 1990. A small 180” fast scanning mass spectrometer. (Great Britain) In order to monitor fast changes in residual gas composition, a fast
scanning mass spectrometer was developed, which achieved a full mass scan from 2 to 100 amu in 100 msec. The construction of the electron multiplier, and the modifications of the source are discussed. A scanning speed of approximately 1 amu msec-’ and a source sensitivity of 0.1 mA torrr’ produces a statistical fluctuation in the number of ions arriving at the dynode of about f3 % at a partial pressure of 10 ntorr and f 10% at a partial pressure of 1 ntorr. D K Jefferies, J Sci Instrum, 44 (8), Aug 1967, 587-592. 22 1991. A mercury reservoir for cut-offs or McLeod gauges. (Great Britain) The compact and reliable mercury reservoir which is described, utilizes flexible stainless steel tubing which permits control of the mercury level by bending. F S Baker and J Pritchard, J Sci Instrum, 44 (8), Aug 1967, 652-653. 23. PLUMBING Operating gears in a simulated 2070.
space vacuum.
See abstract
23 : 34 number
23 : 43 1992. The application of polyimide to ultrahigh vacuum seals. (Great Britain) In order to achieve ultrahigh vacuum levels, vacuum systems must be baked out to temperatures as high as 300°C. Until the present time, the only satisfactory seals that have been demonstrated to withstand such bakeout temperatures are those with metal gasket material usually OFHC copper. When system bakeout temperatures need not exceed 15O”C, Viton A has been commonly used. This article describes measurements made recently on a new ultrahigh vacuum material called polyimide. It withstands intermediate temperature bakeout up to 300°C and has a lower outgassing rate than Viton A. To examine
the usefulness of polyimide as a sealing material compared to Viton A, the following criteria were chosen for experimental evaluation: (a) outgassing rate, (b) pumpdown characteristics, (c) mass spectrographic analysis of outgassing products, (d) mechanical properties. P W Hait, Vacrrmn, 17 (IO), Ott 1967, 547-550. 1993. The properties of Viton “A” Elastomers. application of Viton “A” seals in high vacuum.
23 : 43 Part V. The practical
(Great Britain) Previous articles in this series have described in detail the mechanisms by which gases and vapour are released from Viton “A” elastomer when used as atmospheric seals or fully immersed in vacuum. Experimental measurements have given quantitative data for sorption, solubility, diffusion and permeation of gases in and through Viton under various conditions. The findings, which are briefly summarized, indicate how Viton elastomers may be used to best advantage in high vacuum systems, and how pump-down performance may be predicted. The importance of atmospheric permeation leads to the adoption of double O-ring seals, with an evacuated interspace, as an alternative to all-metal gaskets. Pressures of about lO_‘” torr can fairly readily be reached, with very low organic contamination levels. At high pressures, contamination due to O-rings appears to be negligible. L de Csernatony and D J Crawley, I’uclruf?r, 17 (IO), Ott 1967, 55l554. 23
: 33
(USA) A fibre optic window has been fitted to a stainless steel field ion microscope permitting the use of direct contact photography for recording the image. The elimination of intermediate optics coupled with the use of large format sheet film results in shorter exposure times and increased quality of the field ion micrograph. The technique of fixing the window onto a Conflat vacuum seal is described. J J Hren and R W Newman, Rev Sci Znstrrtm, 38 (7), 1967, 869-870. 1994. Fibre optics in field ion microscopy.
1995. Thermal O.l”K. (USA)
transport
across
superconducting
solder
23 : 17 joints near
Heat transfer rates across various types of soft solder joints were investigated between 0.06 and 0.5”K using a 3He-4He dilution refrigerator. For Cd-Bi junctions and thin Sn-Pb junctions, the heat flux per unit area and unit temperature difference is about twice that predicted by the theory. Junctions of Sn-Sb and Sn-In have a much lower conductance. W A Steyert, Rev Sci Iustrrrm, 38 (7), 1967. 9644966. 23 1996. Device to move mechanisms inside chambers at ultrahigh vacuum.
(USA)
A cylindrical metallic bellows has in the far end an internal gear and a smaller gear which is coupled to a rigid shaft that can rotate and extends inside the vacuum chamber. The construction of the device is described. J M Guerrero, Rev Sri Instrrm~, 38 (7), 1967, 970-97 I. 23 : 30 1997. Preparation of thin self-supporting beryllium foils. (USA) Self-supporting beryllium foils of 5-10 micrograms/cm2 and a diameter of 0.63 cm, were obtained by evaporating Be onto a substrate of monobasic trisodium phosphate (Na,P,Or”) which is evaporated previously. The technique is described in detail. H Oona and D G Rickel. Rev Sci Instrrrm, 38 (7). 1967. 980. 23 1998. Tee drawing for tubular vacuum systems. (USA) Improved welded tee connections are made by drawing a die of circular cross section through an elliptical cut-out in the wall of the main tube to form a smooth tee transition, and then butt-welding an extension tube to this opening. Fabrication procedures, tooling, and equipment has been developed for stainless steel tubing, from 1 to 6 inch od and 0.065 to 0.025 inch wall thickness. The process has been successfully applied to copper, Inconel, aluminium and types 304, 316 and 321 stainless steels. H M Ruess et al, Rep LA-35 17, Nov 1966 (Los Alamos Scientific Lab, New Mexico). 23 : 44 1999. The behaviour of lubrication system components in a vacuum environment. (USA) Evaporation experiments were conducted with various fluids, greases, inorganic compounds, and soft metals, to determine the vacuum environment effect on evaporation behaviour. Friction, adhesion and 675
abstracts
1986-1999
23 1986. Thin formvar coated counter windows. (Netherlands) By coating pyroxylin films with formvar a pressure tight window can be produced that will stand up better under roughing and venting of the vacuum system than the same thickness of pure pyroxylin. The technique used to prepare these windows is described. A typical thickness of 45 /cg/cm”, with a surface area of 0.2 square inches will withstand a pressure of 100 torr. R A Morrison and K A Reed, NIICI I~~str.~nt Methods, 53 (I), JII!,, 1Y67, 173-174. 22 1987. Modified McLeod gauge eliminates measurement errors. (USA) Conventional McLeod gauges are subject to errors due to diffusion of mercury, particularly when a cold trap is used. A method is described to overcome this difficulty by inserting a magnetically operated valve between the mercury reservoir and the sample chamber. M C Kells, Fusion, 14 (2), 1967, 19-20. 22 1988. Modified McLeod
gauge records automatically.
(USA)
A modified McLeod gauge which records measurements automatically and can be programmed in advance by means of an automatic timer is described. The system consists of the gauge, an air/vacuum pumping device, and appropriate circuitry to cycle the pumping device. The gauge - - is a modification of the McLeod gauge - _ which indicates the pressure by the change in resistance of two platinum wires, contacted by the columns of mercury. The construction of the device and its operation is described. P A Faeth, Fusion, 14 (2), 1967, 21-23. 1989. In-chamber vacuum gauge calibration to cryopumping measurements. (USA)
22 method and its application
The report describes a method of calibrating mass spectrometers and ion gauges for pumping speed measurements. Sensitivity factors and pumping speed constants are determined from an analysis of the chamber pressures during gauge calibration and pumping speed measurements. The CO, sensitivity factor for the ion gauge or mass spectrometer is obtained. The pumping speed of a 77°K surface was determined for 300°K CO,. R M Freeman, Rep AEDC-TR-66-234; AD-645509, Jan 1967 (AR0 Itlc, Arnold Air Force Station. Terrrressee). 22 : 33 1990. A small 180” fast scanning mass spectrometer. (Great Britain) In order to monitor fast changes in residual gas composition, a fast
scanning mass spectrometer was developed, which achieved a full mass scan from 2 to 100 amu in 100 msec. The construction of the electron multiplier, and the modifications of the source are discussed. A scanning speed of approximately 1 amu msec-’ and a source sensitivity of 0.1 mA torrr’ produces a statistical fluctuation in the number of ions arriving at the dynode of about f3 % at a partial pressure of 10 ntorr and f 10% at a partial pressure of 1 ntorr. D K Jefferies, J Sci Instrum, 44 (8), Aug 1967, 587-592. 22 1991. A mercury reservoir for cut-offs or McLeod gauges. (Great Britain) The compact and reliable mercury reservoir which is described, utilizes flexible stainless steel tubing which permits control of the mercury level by bending. F S Baker and J Pritchard, J Sci Instrum, 44 (8), Aug 1967, 652-653. 23. PLUMBING Operating gears in a simulated 2070.
space vacuum.
See abstract
23 : 34 number
23 : 43 1992. The application of polyimide to ultrahigh vacuum seals. (Great Britain) In order to achieve ultrahigh vacuum levels, vacuum systems must be baked out to temperatures as high as 300°C. Until the present time, the only satisfactory seals that have been demonstrated to withstand such bakeout temperatures are those with metal gasket material usually OFHC copper. When system bakeout temperatures need not exceed 15O”C, Viton A has been commonly used. This article describes measurements made recently on a new ultrahigh vacuum material called polyimide. It withstands intermediate temperature bakeout up to 300°C and has a lower outgassing rate than Viton A. To examine
the usefulness of polyimide as a sealing material compared to Viton A, the following criteria were chosen for experimental evaluation: (a) outgassing rate, (b) pumpdown characteristics, (c) mass spectrographic analysis of outgassing products, (d) mechanical properties. P W Hait, Vacrrmn, 17 (IO), Ott 1967, 547-550. 1993. The properties of Viton “A” Elastomers. application of Viton “A” seals in high vacuum.
23 : 43 Part V. The practical
(Great Britain) Previous articles in this series have described in detail the mechanisms by which gases and vapour are released from Viton “A” elastomer when used as atmospheric seals or fully immersed in vacuum. Experimental measurements have given quantitative data for sorption, solubility, diffusion and permeation of gases in and through Viton under various conditions. The findings, which are briefly summarized, indicate how Viton elastomers may be used to best advantage in high vacuum systems, and how pump-down performance may be predicted. The importance of atmospheric permeation leads to the adoption of double O-ring seals, with an evacuated interspace, as an alternative to all-metal gaskets. Pressures of about lO_‘” torr can fairly readily be reached, with very low organic contamination levels. At high pressures, contamination due to O-rings appears to be negligible. L de Csernatony and D J Crawley, I’uclruf?r, 17 (IO), Ott 1967, 55l554. 23
: 33
(USA) A fibre optic window has been fitted to a stainless steel field ion microscope permitting the use of direct contact photography for recording the image. The elimination of intermediate optics coupled with the use of large format sheet film results in shorter exposure times and increased quality of the field ion micrograph. The technique of fixing the window onto a Conflat vacuum seal is described. J J Hren and R W Newman, Rev Sci Znstrrtm, 38 (7), 1967, 869-870. 1994. Fibre optics in field ion microscopy.
1995. Thermal O.l”K. (USA)
transport
across
superconducting
solder
23 : 17 joints near
Heat transfer rates across various types of soft solder joints were investigated between 0.06 and 0.5”K using a 3He-4He dilution refrigerator. For Cd-Bi junctions and thin Sn-Pb junctions, the heat flux per unit area and unit temperature difference is about twice that predicted by the theory. Junctions of Sn-Sb and Sn-In have a much lower conductance. W A Steyert, Rev Sci Iustrrrm, 38 (7), 1967. 9644966. 23 1996. Device to move mechanisms inside chambers at ultrahigh vacuum.
(USA)
A cylindrical metallic bellows has in the far end an internal gear and a smaller gear which is coupled to a rigid shaft that can rotate and extends inside the vacuum chamber. The construction of the device is described. J M Guerrero, Rev Sri Instrrm~, 38 (7), 1967, 970-97 I. 23 : 30 1997. Preparation of thin self-supporting beryllium foils. (USA) Self-supporting beryllium foils of 5-10 micrograms/cm2 and a diameter of 0.63 cm, were obtained by evaporating Be onto a substrate of monobasic trisodium phosphate (Na,P,Or”) which is evaporated previously. The technique is described in detail. H Oona and D G Rickel. Rev Sci Instrrrm, 38 (7). 1967. 980. 23 1998. Tee drawing for tubular vacuum systems. (USA) Improved welded tee connections are made by drawing a die of circular cross section through an elliptical cut-out in the wall of the main tube to form a smooth tee transition, and then butt-welding an extension tube to this opening. Fabrication procedures, tooling, and equipment has been developed for stainless steel tubing, from 1 to 6 inch od and 0.065 to 0.025 inch wall thickness. The process has been successfully applied to copper, Inconel, aluminium and types 304, 316 and 321 stainless steels. H M Ruess et al, Rep LA-35 17, Nov 1966 (Los Alamos Scientific Lab, New Mexico). 23 : 44 1999. The behaviour of lubrication system components in a vacuum environment. (USA) Evaporation experiments were conducted with various fluids, greases, inorganic compounds, and soft metals, to determine the vacuum environment effect on evaporation behaviour. Friction, adhesion and 675