Classified abstracts 908-919

the absolute amount of gas injected into the device. Mass spectro- metric analysis of helium before and after purification was carried out in an ultrahigh vacuum analyzing chamber with the CEC 21614 residual gas analyzer. With the exception of hydrogen and helium, impurities were reduced from 400 ppm to tess than 1 ppm by the liquid nitrogen cooled charcoal trap. Hydrogen concentration was not at all reduced. Precise analyses of commercial deuterium and hydro- gen were also carried out and compared with manufacturer's specifi- cations. K J Chin et al, J Vac Soc Japan, 9 (10), 1966, 398-404 (in Japanese).

20 908. The application of a selective pumping techniques to upgrade vacuum chambers. (USA) A "selective pumping" approach to the problem of increasing the capacity of a pumping system so that it can handle larger dynamic gas loads at lower chamber pressures. The proposed approach is based on the use of ion, titanium sublimation, and liquid nitrogen cryogenic pumping mechanisms which are committed selectively to the system, after the chamber has been roughed down to the appropriate pressure. This approach is distinguished by the fact that the pumping system is oil-free, capable of continuous operation while relatively unattended, and, in case of operating failure, maintains the chamber under vacuum. R A Wolf, J Environmental Sci, 9, 1966, 12-16.

20 909. Ion chamber. (Great Britain) Gas losses are reduced by keeping the chamber gas-tight when specimens are changed over. Specimens can also be measured con- tinuously. The apparatus consists of a main chamber and a subsidiary compartment which houses the specimen carrier and can be evacuated. A sealing cover can be removed to obtain access to the main chamber without loss of vacuum and a means of positioning the specimen through channels connecting the two compartments is provided. European Atomic Energy Community, Brit Patent 1,052,558, Patent Abstr, 7 (4)part D, 24th Jan 1967, 1.

2O 910. Low pressure apparatus. (Great Britain) This will reach 10 -9 torr within two hours when the head of a cold- gas refrigerator is at 80°K. The space to be evacuated is in thermal contact with the cold-gas refrigerator and is degassed at this low temperature during operation. The chamber attached to a vacuum pump is also degassed. This refrigerator is first operated as a heat pump, after which it is operated as a cold source and the space to be exhausted is further degassed. (Author) Phflips Gineilampenfab N V, Brit Patent 1,052,793, Patent Abstr, 7 (4) part B, 24th Jan 1967, 1.

2O 911. Continuous linear vacuum system. (Great Britain) Suitable for evaporation of metals or dielectrics being processed in a series of interconnected chambers, these chambers hold masking apparatus, means for positioning the substrate and heating apparatus. Pressure is kept constant while substrates are moved through the chambers via special seal units. One such seal unit, has a spring-loaded neoprene or silastic roller with a lever to open or close a rectangular aperture. (Author) Standard Telephones & Cables Ltd, Brit Patent 1,055,020, Patent Abstr, 7, (6) part 6B, 1st Feb 1967, 8.

21. PUMPS AND P U M P FLUIDS 21

912. By-products emitted from spatter-ion pumps. (USA) Due to electrically neutral fragments, gray to black films have grown on a surface a few inches from the pump electrode. Titanium nitride and titanium oxide are both deposited. The weight ratio of these solid by-products is about 0.1 per cent compared to a diffusion pump. K Wear, Res/Develop, Feb 1967, 66-69.

21 913. Study of the efficiency of a getter-ion pump. (India) Efficiency of a getter ion pump developed at the Van de Graaff laboratory was studied. Outgassing of the system, performance of the getter and the distribution of the getter material inside the pump chamber are factors which influence the efficiency. Baking of the pump chamber was found essential for attaining lower ultimate pressures and better pumping efficiency. K B Nambiur and A S Divatia, AERE Bombay, India, 1966, 11 pages.

21 914. A new type of diffusion pump boiler for ultrahigh vacuum use. (Great Britain) Eruptive boiling of pump fluid, which causes pressure fluctuations in high and ultrahigh vacuum systems, has been thoroughly eliminated by a newly developed diffusion pump boiler, named N-boiler. Many improvements in pump performance have been demonstrated in some apposite experiments. The pump with the N-boiler permits a wider range of heater input and shows better stability of ultimate pressure and higher pumping speed so that the performance sur- passes in every respect that of conventional pumps. The N-boiler, in substance, consists of a simple vessel and an external ring heater which is located in a region somewhat higher than the fluid level. Adopting this new method, the fluid rotates or trembles automatically so that the temperature gradient in the fluid is much reduced. The evaporation rate on the moving surface in the N-boiler is almost unity compared with 0.2-0.4 on a placid surface of DC-705 fluid in a conventional boiler. It has been concluded that the continuous production of the fresh surface is one of the essential conditions for obtaining a constant high evaporation rate. H Okamoto and Y Murakami, Vacuum, 17 (2), Feb 1967, 70-86.

21 915. Starting sputter-ion pumps and the outgassing of wet metal surfaces. (Great Britain) Sputter-ion pumps are found to start easily from nitrogen with a wet metal surface load. Repeated wet starts do not change the starting or operating characteristics of the pump. Outgassing of wet stainless steel is found to follow the relation q=1.25 × 10 -5 t -1"47 torr-litres per second per cm 2 after 15 minutes and to be independent in shape for short or long exposures to water. P R Bell et al, Vacuum, 17 (2), Feb 1967, 87-90.

21 916. A new getter system for opaque vacuum tubes, using samarium or thulium. (Great Britain) A new getter system for opaque or metal-walled tubes is described, in which thulium or samarium is fired off the tube envelope by external heating. This eliminates the need for insulated electrical lead-through seals. Also, because the evnelope temperature can be checked externally, some visual control of firing is provided, resulting in greater reliability than is obtained with "blind-fired" conventional barium getters. The rare earth metals can be used as general tube getters and their ability to adsorb a succession of different gases has been demonstrated. The importance of sorption measurements with a succession or mixture of gases is stressed and quantitative data are presented. D S Stark et al, Vacuum, 17 (2), Feb 1967, 91-96.

21 917. Mechanical booster pump. (Great Britain) This Roots type of pump, overcomes incomplete sealing between the impellers and walls of the housing. Two rotating shafts sealed into the wall carry inter-engaging two-lobe impellers. The external peri- pheries of each have openings into a central cavity. Pump fluid escaping into the higher pressure region passes through these holes into the cavities which are adapted for evacuation through the shaft bore. (Author) Leybold Holding A G, Brit Patent 1,054,733, Patent Abstr, 7 (6) part B, 1st Feb 1967. 2.

21 918. High vacuum pumping system. (Great Britain) The system is similar to the one described in 719,990 but simplified and with improved reliability for the controlled operation of an ejector pump in series with a primary pump. A valve automatically controls the need for the use of the ejector pump. This ejector pump includes a supersonic jet diffuser element and when actuated, a supersonic fluid flow is produced and sustained by the combination of a primary and secondary stream of fluid. (Author) Nash Engineering Co, Brit Patent 1,054,749, Patent Abstr, 7 (6) part B, 1st Feb 1967, 2.

21 919. Rotary vacuum pump. (Great Britain) The pump has a rotary slinger-type seal used in conjunction with a surrounding stationary sleeve having one or more annular oil- collecting grooves, eg, for retaining oil leaking past the slinger when the pump is stopped, and the slinger co-operates with part of the sleeve to pump away the collected oil from the drain passage for the grooves. (Author)

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