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78. Polythene cover plate manufacture
Classified abstracts 78--85 range 195-373°K a direct logarithmic growth law was obeyed. Limiting oxygen uptakes varied from , ~ l l A at 90°K to ,-~87A at 373 °K. Electrical resistance and thermal e.m.f, measurements have been made on thin polycrystalline layers of orthorhombic lead monoxide at oxygen pressures in the range 10 -1 to 10-3 ram. The results are consistent with a model in which the lead oxide retains n-type bulk behaviour over the whole of this range, but the measured over-all resistance is dominated by a p-type surface layer at oxygen pressures > ~ 1 0 -~ ram. It is considered that in the principal mode of bulk nonstoichiometry there are present anion vacancies and electrons. The observed oxidation kinetics have been interpreted on the basis of the dissociation of oxygen being rate controlling, while the exact form of the oxidation kinetics depends on the way in which the concentration of adsorption sites varies in the course of the reaction. If at high temperatures the degree of surface coverage by adsorbed oxygen is low, a linear law results. If at lower temperatures a substantial fraction of adsorption sites is occupied and if adsorbed oxygen is present both as neutral pairs and as fieldcreating ions with the former in large excess, it is shown that the concentration of adsorption sites may decrease approximately exponentially with increasing oxide layer thickness, leading to an approximate direct logarithmic growth law. The oxidation theory of Grimley and Trapnell has been extended to include systems where anion vacancies are involved. (Authors) J R Anderson and V B Tare, J Phys Chem, 68, June 1964, 1482-
1489.
32. Nucleonics 32
British national bubble chamber at CERN. See Abstr. No. 28. 32 Large liquid hydrogen filled bubble chamber. See Abstr. No. 29. 32 : 58 78. Polythene cover plate manufacture. (Great Britain) Description of the techniques involved in producing the polythene cover plates for the N I M R O D accelerator vacuum system. Anon, Nuclear Engng, 9 (97), June 1964, 200. 32 79. " N i m r o d " 7 GeV proton synchrotron. (Great Britain) Anon, Engineer, 217 (5649), 1 May 1964, 776-777. 32 80. Magnet and vacuum system of "Nimrod". (Great Britain) Anon, Engineer, 217 (5651), 15 May 1964, 855. 32 81. German electron synchrotron. (Great Britain) Anon, Engineer, 218 (5667), 4 Sept 1964, 387-389. 32 82. Engineering techniques in Nimrod. (Great Britain) The Nimrod accelerator is a 7 GeV weak-focusing constant gradient proton synchrotron designed for a maximum beam current of 101~ proton; it is situated at the Rutherford High Energy Laboratory at Harwell. Its construction involved a capital expenditure of £35 million and involved high precision engineering on a large scale. In addition to the contribution it is expected to make to high-energy physics research, the article points out that there has been a valuable technological fall-out as a result of the engineering problems that have had to be solved. The protons make about one million circuits round a 150 ft diameter ring before being ejected and the vacuum vessel within which they circulate has a cross-section 36 in. by 9 in. and must be made of a non-conducting and non-magnetic material with a low outgassing rate, high irradiation resistance and great mechanical strength. Bisphenol " A " di-epoxide resin cured with methyl " N o d i c " anhydride and reinforced with glass cloth has been found most suitable. The vessel is of double construction with the outer vessel bolted through vacuum seals to the pole-pieces and the interspace pumped down to 1 torr. Thus the outer vessel need only be 1/8 in. thick, since it is mechanically supported, and the inner } in., since it has only a small pressure difference to withstand. Details are given of the manufacturing techniques used in fabricating the individual 50 ft long vessels. It was discovered that the glass fibres were tubular and precautions had therefore to be taken to seal exposed ends. The leakage rate in the inner vessel was better than 5 × 10 -4 torr h/s. PVC/Nitrile rubber seals have been developed for use with the system. Initial pump-down of the inner and outer vessels is carried out by 16 rotating vane pumps (each of 60 l./sec capacity) to 1 ton. The inner vessel is then taken down to
0.02 torr by 8 Roots rotary combinations (each of 100 1./sec capacity). A final pressure of 10-6 torr is produced by 40 pumping units, each consisting of a 24 in. fractionating oil diffusion pump backed by a vapour booster and a 150 1./min rotary pump. Sliding gate valves and chevron baffles cooled to --25°C reduce backstreaming. Mercury diffusion pumps are used for the 15 MeV linear accelerator injector because of the need to eliminate oil from the r.f. cavity. The I0 pumps have a total speed of 10,000 1./sec and are arranged to pump each drift tube separately. Backstreaming of mercury vapour is arrested by a series of baffles, the final of which is cooled by the evaporation of liquid air fed from a selfcontained system. Anon, Nuclear Engng, 9 (97), June 1964, 197-200.
33. G e n e r a l p h y s i c s a n d e l e c t r o n i c s 33 Field emission from vacuum deposited metallic film and its role in electric break-down in vaccuum. See Abstr. No. 39. 33 Electron microscope study of vacuum condensates of copper. See Abstr. No. 64. 33 Dependence of rate of growth of monocrystalline germanium layers on orientation of substrate and condition of crystallization in a gaseous medium. See Abstr. No. 67. 33 Superconducting thin films of niobium, tantalum, tantalum nitride, tantalum carbide and niobium nitride. See Abstr. No. 69. 33 Large electron beam furnace. See Abstr. No. 87. 33 Utilization of rhenium and rhenium alloys in electron vacuum tubes. See Abstr. No. 97. 33 Destruction of ceramic and glass by ion bombardment. See Abstr. No. 98. 33 : 41 83. Surface potentials of nitrogen on individual crystal faces of tungsten. (USA) A A Holscher, J ChemPhys, 41 (2), 15 July 1964, 579-580. 33 84. Mass spectrometer. (Great Britain)
Nuclear Engng, 9 (101), Oct 1964, 378-379.
34. High altitude and space technology 34 Vacuum chamber for IP-4M mechanical test installation. See Abstr. No. 94.
36. Drying, degassing and concentration 36 85. A device for preventing vapour from the pump fluid entering high vacuum chamber during the bakeout period. (Germany) An ultra-high vacuum system incorporating a fore pump followed by two mercury diffusion pumps in series is described. The suction lead from the recipient to the main pump has 2 cold traps in parallel, each fitted with a ground-in ball valve. By operating the traps in turn, it is possible to bake out the whole system, including valve and traps. Final pressures were recorded on Bayard-Alpert and Penning gauges. Measurements were also made with an omegatron and field emission microscope. Differences in gauge readings under ultra-high vacuum conditions are discussed. It appears that the system as desented is capable of producing an end pressure of the order of 10-11 torr. The partial pressure of the Hg after final bake out is estimated at less than 10 per cent of this. It is proposed to carry out similar tests with oil instead of Hg diffusion pumps.
(Germany)
W JS
Bibliography 10 items. F Binder et al, Vakuum Technik, 13 (7), Oct 1964, 210-213.
37. Metallurgy, inorganic chemistry, analytical chemistry 37
The importance of vacuum technique for the production and processingof metals with high melting points. See Abstr. No. 1. 47
1489.
32. Nucleonics 32
British national bubble chamber at CERN. See Abstr. No. 28. 32 Large liquid hydrogen filled bubble chamber. See Abstr. No. 29. 32 : 58 78. Polythene cover plate manufacture. (Great Britain) Description of the techniques involved in producing the polythene cover plates for the N I M R O D accelerator vacuum system. Anon, Nuclear Engng, 9 (97), June 1964, 200. 32 79. " N i m r o d " 7 GeV proton synchrotron. (Great Britain) Anon, Engineer, 217 (5649), 1 May 1964, 776-777. 32 80. Magnet and vacuum system of "Nimrod". (Great Britain) Anon, Engineer, 217 (5651), 15 May 1964, 855. 32 81. German electron synchrotron. (Great Britain) Anon, Engineer, 218 (5667), 4 Sept 1964, 387-389. 32 82. Engineering techniques in Nimrod. (Great Britain) The Nimrod accelerator is a 7 GeV weak-focusing constant gradient proton synchrotron designed for a maximum beam current of 101~ proton; it is situated at the Rutherford High Energy Laboratory at Harwell. Its construction involved a capital expenditure of £35 million and involved high precision engineering on a large scale. In addition to the contribution it is expected to make to high-energy physics research, the article points out that there has been a valuable technological fall-out as a result of the engineering problems that have had to be solved. The protons make about one million circuits round a 150 ft diameter ring before being ejected and the vacuum vessel within which they circulate has a cross-section 36 in. by 9 in. and must be made of a non-conducting and non-magnetic material with a low outgassing rate, high irradiation resistance and great mechanical strength. Bisphenol " A " di-epoxide resin cured with methyl " N o d i c " anhydride and reinforced with glass cloth has been found most suitable. The vessel is of double construction with the outer vessel bolted through vacuum seals to the pole-pieces and the interspace pumped down to 1 torr. Thus the outer vessel need only be 1/8 in. thick, since it is mechanically supported, and the inner } in., since it has only a small pressure difference to withstand. Details are given of the manufacturing techniques used in fabricating the individual 50 ft long vessels. It was discovered that the glass fibres were tubular and precautions had therefore to be taken to seal exposed ends. The leakage rate in the inner vessel was better than 5 × 10 -4 torr h/s. PVC/Nitrile rubber seals have been developed for use with the system. Initial pump-down of the inner and outer vessels is carried out by 16 rotating vane pumps (each of 60 l./sec capacity) to 1 ton. The inner vessel is then taken down to
0.02 torr by 8 Roots rotary combinations (each of 100 1./sec capacity). A final pressure of 10-6 torr is produced by 40 pumping units, each consisting of a 24 in. fractionating oil diffusion pump backed by a vapour booster and a 150 1./min rotary pump. Sliding gate valves and chevron baffles cooled to --25°C reduce backstreaming. Mercury diffusion pumps are used for the 15 MeV linear accelerator injector because of the need to eliminate oil from the r.f. cavity. The I0 pumps have a total speed of 10,000 1./sec and are arranged to pump each drift tube separately. Backstreaming of mercury vapour is arrested by a series of baffles, the final of which is cooled by the evaporation of liquid air fed from a selfcontained system. Anon, Nuclear Engng, 9 (97), June 1964, 197-200.
33. G e n e r a l p h y s i c s a n d e l e c t r o n i c s 33 Field emission from vacuum deposited metallic film and its role in electric break-down in vaccuum. See Abstr. No. 39. 33 Electron microscope study of vacuum condensates of copper. See Abstr. No. 64. 33 Dependence of rate of growth of monocrystalline germanium layers on orientation of substrate and condition of crystallization in a gaseous medium. See Abstr. No. 67. 33 Superconducting thin films of niobium, tantalum, tantalum nitride, tantalum carbide and niobium nitride. See Abstr. No. 69. 33 Large electron beam furnace. See Abstr. No. 87. 33 Utilization of rhenium and rhenium alloys in electron vacuum tubes. See Abstr. No. 97. 33 Destruction of ceramic and glass by ion bombardment. See Abstr. No. 98. 33 : 41 83. Surface potentials of nitrogen on individual crystal faces of tungsten. (USA) A A Holscher, J ChemPhys, 41 (2), 15 July 1964, 579-580. 33 84. Mass spectrometer. (Great Britain)
Nuclear Engng, 9 (101), Oct 1964, 378-379.
34. High altitude and space technology 34 Vacuum chamber for IP-4M mechanical test installation. See Abstr. No. 94.
36. Drying, degassing and concentration 36 85. A device for preventing vapour from the pump fluid entering high vacuum chamber during the bakeout period. (Germany) An ultra-high vacuum system incorporating a fore pump followed by two mercury diffusion pumps in series is described. The suction lead from the recipient to the main pump has 2 cold traps in parallel, each fitted with a ground-in ball valve. By operating the traps in turn, it is possible to bake out the whole system, including valve and traps. Final pressures were recorded on Bayard-Alpert and Penning gauges. Measurements were also made with an omegatron and field emission microscope. Differences in gauge readings under ultra-high vacuum conditions are discussed. It appears that the system as desented is capable of producing an end pressure of the order of 10-11 torr. The partial pressure of the Hg after final bake out is estimated at less than 10 per cent of this. It is proposed to carry out similar tests with oil instead of Hg diffusion pumps.
(Germany)
W JS
Bibliography 10 items. F Binder et al, Vakuum Technik, 13 (7), Oct 1964, 210-213.
37. Metallurgy, inorganic chemistry, analytical chemistry 37
The importance of vacuum technique for the production and processingof metals with high melting points. See Abstr. No. 1. 47