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Sorption of nitrogen by titanium films
Classified
abstracts
962-971
within about 0.03 eV of threshold, the probability of exciting the 23 S state of helium is about 1.5 times larger than that for the 2l S state. For HCl all of the optically allowed transitions are observed. Temporary negative ion resonances are observed below the first electronic state for all of the aromatic molecules studied. R N Compton et al J C/rem Whys, 48 (2), 15th Jan 1968,901-909. 18 962. Photoionization of CH,; heat of formation of CHs. (USA) Methyl radicals produced by pyrolysis at various temperatures have been photoionized by photons in a 1.6 A bandwidth over the energy range 9.5-16.5 eV with mass-spectrometric detection. The curve of photoionization cross section for the parent ions shows that direct ionization predominates in the threshold region, and that the geometrical form of the positive ion in its ground state is very similar to that of the neutral radical. Hot bands and other vibrational features observed near threshold are only partly explained. The data are compared with adsorption spectra and electron-impact curves. W A Chupka and C Lifshitz, J Chem Phys, 48 (3), 1st Feb 1968, 11091115. -
II.
Vacuum
20. PUMPING
apparatus
and auxiliaries
SYSTEMS
20 : 30 A bakeable vacuum evaporator for the deposition of large area thin film circuits. See abstract number 1002. 20 963. Theoretical analysis of a two-pump vacuum system. (USA) Factors affecting the pressure in a vacuum chamber pumped by two dissimilar pumps are investigated by mean? of a simplified theoretical model, taking account of the possibility of one of the pumps acting as a significant source of gas or vapour. It is shown that minimum chamber pressure may only be obtained with a finite pumping line impedance in series with this pump. This is experimentally demonstrated for a system pumped by a mechanical pump and a zeolite trap. The application of the theory to the design of vacuum systems is discussed. B F R Kendall, .I Vat Sci Technoi, 5 (2), March-April 1968 45-48. 20 964. Industrial
ultrahigh vacuum by means of the double-chamber technique. (France) A complete ultrahigh vacuum system, suitable for industrial evaporation processes, is described in which an intermediate chamber is interposed between the pumps (operating down to lo-’ torr) and the work chamber which incorporates an 150 litres/sec “Orbion” pump and a 2ooO litres/sec cryotitanium pump (evaporated titanium on a liquid cooled surface). Tests have shown that this unit will provide lo-’ torr in the intermediate chamber and 5 x lo-r0 torr in the work chamber within two or three hours of start-up and including a l-hour bake-out. Construction and operation of the system is detailed and an example is given of application to co-evaporation processes with the crucibles in the intermediate chamber while coating occurs in the WHV chamber. J Bailleul-Langlais, Le Vide, 23 (133), Jan-Feb 1968,25-3 1 (in French). 20 965. Emission electron microscope with ultrahigh vacuum in the object chamber. (Czechoslovakia) An emission electron microscope is described in which the object chamber is pumped down to 1O-8 torr by an Orbitron type ion gettering pump and down to lo-& torr in other parts of the optical system by conventional pumping. The object chamber is viton-sealed and although it is not baked, pressures of 5 x 1O-8 torr are reached in 15 min. with the ultimate pressure of 1 x 1O-8 torr. The residual gases are analyzed by a Farvitron mass spectrometer. A Delong et al, Slabopr Obzor, 29 (2), Feb 1968, 65-70 (in Czech). 20 966. Accessory for stressing of polymer strips in the vacuum coat% VUP-1. (USSR) An accessory is described designed for preparation of samples of elastomers for electron microscopy by means of coating the elastomer, in a stressed form, at temperatures below zero. G T Tkachenko and I A Alekseev, Zavodsk Lab, 34 (I), 1968, 117 (in Russian). 428
21. PUMPS AND PUMP FLUIDS 21 : 16 Sorption of nitrogen by titaninm films. See abstract number 910. 21 :2p Effect of a thermoelectrically cooled batKe in oil diffusion pan15 systems. See abstract number 997. 1.
Ll
967. Glass orbitron pump of J-cm diameter. (USA) The construction of a 5-cm diameter glass orbitron pump is described and its performance investigated. The inside wall of the glass body is covered by a stainless steel mesh to avoid diiculties due to peeling of titanium. The average pumping speeds obtained with this system were 11.6 litres/sec for nitrogen, 5.6 litres/sec for air and 0.1 litres/sec for argon in pressure ranges between lo+ and lo-” torr. P K Naik and R G Herb, J Vat Sci Technol, 5 (2), March-April 1968, 4244. 21 :25 968. Isolation of ultrahigh vacuum systems from oil diiusion pumps. (USA) Surface diffusion and adsorption-desorption are the means by which oil is passed through traps, in the molecular flow region. Surface diffusion may be eliminated by molecular sieve material on the surface paths in the trap. It is shown that a long isolation time (ie time remaining at base pressure) is a necessary but not a sufficient condition for complete isolation of a system from an oil diffusion pump. Field emission microscopy studies indicate that oil may be transferred to the vacuum system during baking and also under subsequent quiescent conditions. Oil transfer during bake-out may be avoided by use of an optical baffle where all internal trap surfaces see only molecular sieve material, but this does not exclude transfer under quiescent conditions. The addition of a titanium getter, in-line between the molecular sieve trap and the high vacuum chamber, avoids oil transfer under all operating conditions. R D Gretz, J Vat Sci Technol, 5 (2), March-April 1968,49-53. 21 969. Production of ultrahigh vacuum by a titanium deposit on a cold surface. 1. Basic research. (France) Evaporated titanium films, deposited under vacuum on substrates cooled by liquid nitrogen, show very high activity, yielding a practical pumping speed of 10 litres/sec per cm% for air or hydrogen. The surface capacity is limited to a few monolayers but this capacity is greatly increased by migration of the gas into the metal. Ultimate pressures should certainly be better than lo-r0 torr. An adsorption mechanism is proposed which assumes that the effect of low temperature on the deposited titanium is to produce a heterogeneous surface presenting preferential adsorption sites in numbers about the same as those on the apparent surface of room temperature deposits. F Prevot and Z Sledziewski, Le Vide, 23 (133), Jan-Feb 1968, l-5 (in French). 21 970. Production of ultrahigh vacuum by a titanium deposit on a cold
surface. 2. Technology and application. (France) The Fusion Research Group at the Euratom-CEA Association Laboratories at Fontenay-aux-Roses, France, have constructed about 20 of these pumps in the period since 1961. The largest system developed was for the plasma research project MM11 and involved several titanium pumps, each with a speed of l,OOO,OOO litres/sec. The evaporators operate by direct heating (Joule effect) of spiral titanium filaments, 0.8 mm diameter with interlocking molybdenum spirals both supported on a tantalum or tungsten core. For cold surfaces up to 1 m2, aluminium bronze is used but in very large assemblies copper sheet welded to stainless steel is employed, The construction of the MM11 system is described in detail. The pumped volume amounted to 40 ms and the auxiliary pumping system, composed of rotary vane, Roots and oil diffusion pumps with liquid nitrogen traps, operated at 10,000 litres/sec. The active surface of titanium required was 10 ma giving a pumping speed of l,lOO,OOOlitres/sec. Z Sledziewski and F Prevot, Lx ‘vide, 23 (133), Jan-Feb 1968, 5-14 (in French). 21 971. Titanium filaments for sublimation pumps operating under ultra-
high vacuum. (France) Sublimation of titanium wire to obtain a gettering film is accompanied by release of gases, particularly hydrocarbons and large amounts of argon. The hydrocarbons originate in the wire-drawing process while the argon derives from the metallurgical process in producing the
abstracts
962-971
within about 0.03 eV of threshold, the probability of exciting the 23 S state of helium is about 1.5 times larger than that for the 2l S state. For HCl all of the optically allowed transitions are observed. Temporary negative ion resonances are observed below the first electronic state for all of the aromatic molecules studied. R N Compton et al J C/rem Whys, 48 (2), 15th Jan 1968,901-909. 18 962. Photoionization of CH,; heat of formation of CHs. (USA) Methyl radicals produced by pyrolysis at various temperatures have been photoionized by photons in a 1.6 A bandwidth over the energy range 9.5-16.5 eV with mass-spectrometric detection. The curve of photoionization cross section for the parent ions shows that direct ionization predominates in the threshold region, and that the geometrical form of the positive ion in its ground state is very similar to that of the neutral radical. Hot bands and other vibrational features observed near threshold are only partly explained. The data are compared with adsorption spectra and electron-impact curves. W A Chupka and C Lifshitz, J Chem Phys, 48 (3), 1st Feb 1968, 11091115. -
II.
Vacuum
20. PUMPING
apparatus
and auxiliaries
SYSTEMS
20 : 30 A bakeable vacuum evaporator for the deposition of large area thin film circuits. See abstract number 1002. 20 963. Theoretical analysis of a two-pump vacuum system. (USA) Factors affecting the pressure in a vacuum chamber pumped by two dissimilar pumps are investigated by mean? of a simplified theoretical model, taking account of the possibility of one of the pumps acting as a significant source of gas or vapour. It is shown that minimum chamber pressure may only be obtained with a finite pumping line impedance in series with this pump. This is experimentally demonstrated for a system pumped by a mechanical pump and a zeolite trap. The application of the theory to the design of vacuum systems is discussed. B F R Kendall, .I Vat Sci Technoi, 5 (2), March-April 1968 45-48. 20 964. Industrial
ultrahigh vacuum by means of the double-chamber technique. (France) A complete ultrahigh vacuum system, suitable for industrial evaporation processes, is described in which an intermediate chamber is interposed between the pumps (operating down to lo-’ torr) and the work chamber which incorporates an 150 litres/sec “Orbion” pump and a 2ooO litres/sec cryotitanium pump (evaporated titanium on a liquid cooled surface). Tests have shown that this unit will provide lo-’ torr in the intermediate chamber and 5 x lo-r0 torr in the work chamber within two or three hours of start-up and including a l-hour bake-out. Construction and operation of the system is detailed and an example is given of application to co-evaporation processes with the crucibles in the intermediate chamber while coating occurs in the WHV chamber. J Bailleul-Langlais, Le Vide, 23 (133), Jan-Feb 1968,25-3 1 (in French). 20 965. Emission electron microscope with ultrahigh vacuum in the object chamber. (Czechoslovakia) An emission electron microscope is described in which the object chamber is pumped down to 1O-8 torr by an Orbitron type ion gettering pump and down to lo-& torr in other parts of the optical system by conventional pumping. The object chamber is viton-sealed and although it is not baked, pressures of 5 x 1O-8 torr are reached in 15 min. with the ultimate pressure of 1 x 1O-8 torr. The residual gases are analyzed by a Farvitron mass spectrometer. A Delong et al, Slabopr Obzor, 29 (2), Feb 1968, 65-70 (in Czech). 20 966. Accessory for stressing of polymer strips in the vacuum coat% VUP-1. (USSR) An accessory is described designed for preparation of samples of elastomers for electron microscopy by means of coating the elastomer, in a stressed form, at temperatures below zero. G T Tkachenko and I A Alekseev, Zavodsk Lab, 34 (I), 1968, 117 (in Russian). 428
21. PUMPS AND PUMP FLUIDS 21 : 16 Sorption of nitrogen by titaninm films. See abstract number 910. 21 :2p Effect of a thermoelectrically cooled batKe in oil diffusion pan15 systems. See abstract number 997. 1.
Ll
967. Glass orbitron pump of J-cm diameter. (USA) The construction of a 5-cm diameter glass orbitron pump is described and its performance investigated. The inside wall of the glass body is covered by a stainless steel mesh to avoid diiculties due to peeling of titanium. The average pumping speeds obtained with this system were 11.6 litres/sec for nitrogen, 5.6 litres/sec for air and 0.1 litres/sec for argon in pressure ranges between lo+ and lo-” torr. P K Naik and R G Herb, J Vat Sci Technol, 5 (2), March-April 1968, 4244. 21 :25 968. Isolation of ultrahigh vacuum systems from oil diiusion pumps. (USA) Surface diffusion and adsorption-desorption are the means by which oil is passed through traps, in the molecular flow region. Surface diffusion may be eliminated by molecular sieve material on the surface paths in the trap. It is shown that a long isolation time (ie time remaining at base pressure) is a necessary but not a sufficient condition for complete isolation of a system from an oil diffusion pump. Field emission microscopy studies indicate that oil may be transferred to the vacuum system during baking and also under subsequent quiescent conditions. Oil transfer during bake-out may be avoided by use of an optical baffle where all internal trap surfaces see only molecular sieve material, but this does not exclude transfer under quiescent conditions. The addition of a titanium getter, in-line between the molecular sieve trap and the high vacuum chamber, avoids oil transfer under all operating conditions. R D Gretz, J Vat Sci Technol, 5 (2), March-April 1968,49-53. 21 969. Production of ultrahigh vacuum by a titanium deposit on a cold surface. 1. Basic research. (France) Evaporated titanium films, deposited under vacuum on substrates cooled by liquid nitrogen, show very high activity, yielding a practical pumping speed of 10 litres/sec per cm% for air or hydrogen. The surface capacity is limited to a few monolayers but this capacity is greatly increased by migration of the gas into the metal. Ultimate pressures should certainly be better than lo-r0 torr. An adsorption mechanism is proposed which assumes that the effect of low temperature on the deposited titanium is to produce a heterogeneous surface presenting preferential adsorption sites in numbers about the same as those on the apparent surface of room temperature deposits. F Prevot and Z Sledziewski, Le Vide, 23 (133), Jan-Feb 1968, l-5 (in French). 21 970. Production of ultrahigh vacuum by a titanium deposit on a cold
surface. 2. Technology and application. (France) The Fusion Research Group at the Euratom-CEA Association Laboratories at Fontenay-aux-Roses, France, have constructed about 20 of these pumps in the period since 1961. The largest system developed was for the plasma research project MM11 and involved several titanium pumps, each with a speed of l,OOO,OOO litres/sec. The evaporators operate by direct heating (Joule effect) of spiral titanium filaments, 0.8 mm diameter with interlocking molybdenum spirals both supported on a tantalum or tungsten core. For cold surfaces up to 1 m2, aluminium bronze is used but in very large assemblies copper sheet welded to stainless steel is employed, The construction of the MM11 system is described in detail. The pumped volume amounted to 40 ms and the auxiliary pumping system, composed of rotary vane, Roots and oil diffusion pumps with liquid nitrogen traps, operated at 10,000 litres/sec. The active surface of titanium required was 10 ma giving a pumping speed of l,lOO,OOOlitres/sec. Z Sledziewski and F Prevot, Lx ‘vide, 23 (133), Jan-Feb 1968, 5-14 (in French). 21 971. Titanium filaments for sublimation pumps operating under ultra-
high vacuum. (France) Sublimation of titanium wire to obtain a gettering film is accompanied by release of gases, particularly hydrocarbons and large amounts of argon. The hydrocarbons originate in the wire-drawing process while the argon derives from the metallurgical process in producing the