810. Ionization gauge using a channel electron miltiplier for pressures below 10−12 torr

Classified abstracts 803-812 21 803. Vacuum pump. (USSR) An improved pump design intended to reduce dead space and increase efficiency is described. This is achieved by making the exhaust valve in the form of an elastic plate set at right angles to the inner wall of the body, which itself has a certain degree of elasticity. Together with the incorporation of a special type of rotor, this arrangement practically eliminates the dead space and greatly increases the efficiency of the whole assembly. The pressure on the valve plate is regulated automatically by connecting it to a membrane or bellows, the position of which is governed by the relative pressures in different parts of the pump. V S Kondrasbev and K S Pak, USSR Patent No 334403, appl 30th April 1970, publd 30th March 1972. 21 804. A gas absorber. (USSR) A new type of gas absorber prepared in the form of a moulding and pressed into a metal strip is described. This has a fair mechanical strength and high absorption properties over a wide temperature range. The composition is as follows (in wt. percent): Ti 50-60, Zr 10-30, Ta 5-15, A1 5-15, the tantalum constituting an innovation. The new constitution widens the working range to 1000 °, increases the mechanical strength, and reduces the danger of spontaneous ignition. The zirconium content may be further reduced by replacing it with a Zr-A1 alloy. M F Boyarina et al, USSR Patent No 336719, appl 19th Oct 1970, publd 29th May 1972. 21 805. Measuring flows of vacuum oil vapour and cracking products in vacuum systems. (USSR) A more sensitive arrangement for measuring flows of complex hydrocarbons in vacuum systems is described; it is intended for residual gas pressures of the order of 10-5 ton'. The total flow of vapour is recorded by means of a field-emission tungsten cathode held at a relatively high temperature, preventing the adsorption of residual gases. Oil cracking products are adsorbed with a heat of adsorption of the order of 100 kcal/mole. If high-voltage pulses are simultaneously applied to the emitter, an emission picture representing the distribution of adsorbed carbon is revealed. The pulse frequency should be no lower than 16 s-1 and the length no greater than 10 ms. V Ya Piiskovskii et al, USSR Patent No 338836, appl lOth Sept 1970, publd 12th June 1972. 21 806. Hydrogen pumping by a new catalytic pump. (USA) A new catalytic pump has been proposed for hydrogen pumping in high and ultrahigh vacuum, and its performance is estimated from the kinetic processes involved. This pump consists of an incandescent metal filament (atomizing catalys0, a cuprous oxide layer (oxidizer), and a liquid nitrogen trap, in which modeular hydrogen is thermally dissociated into atomic hydrogen at the filament which acts upon the cuprous oxide layer to produce condensable water vapour. The speed of the pump in the molecular-flow region is, in principle, associated with the rate of formation of atomic hydrogen at the filament, which not only is a function of hydrogen pressure and filament temperature, but also depends on the filament material and the surface coverage of other chemisorbed species. From the experimental data, suitable temperatures have been determined to obtain the maximum efficiency against electric power. Iridium and rhenium are found to be good materials for the pump filament. Y Murakami, J Vac Sci Technol, 10 (2), March-April 1973, 359-367. 22. G A U G E S 22 807. Vacuum gauges for automated vacuum systems. (USSR) A parametric series of vacuum gauges intended for work with automated vacuum systems is described. The series includes a thermoelectric gauge operating from 30 to 2 × 10 -a torr and a magnetic electrical-discharge gauge operating from 1 0 - 2 t o 10 - 9 torr. These two gauges alone, by virtue of their overlapping ranges, facilitate accurate pressure monitoring over 10 orders of magnitude, Each gauge has an electronic circuit which provides automatic signals when a particular prespecified pressure is reached. Electric scales are also provided to give visual control of the pressure over a fairly wide range. Provision is also made for introducing corrections

necessitated by temperature changes. The low-pressure gauge is based on an inverted magnetron principle, which ensures particularly high reliability. A A Birshert et al, Electronic Industry-a Scientific-Technical Collection, 1972, No. 5, 77-78, (in Russian). 22 808. The MSD-1 mass spectrometer. (USSR) A new mass spectrometer designed for working with automated evacuation systems controlled by a computer is described; it analyses gases with mass numbers of 2-150 at pressures of 10-5-10 - to torr, the resolving power being at least 60. The time required for recording mass spectra is 0.2-2 s. The apparatus is based on a double-beam two-sector mass spectrometer with a magnetic analyser and electric heater, a preamplifier, and a measuring unit. The ion source lies within the analyser and the ion currents are collected by secondaryelectron multipliers, ensuring high speed and sensitivity. The measuring operation is fully automated. A P Averina el al, Electron Industry-a Scientific-Technical Collection, 1972, No 4, 41-42, (in Russian). 22 809. Absolute calibration of Apollo lunar orbital mass spectrometer. (USA) Recent experiments were conducted in Langley Research Center's molecular beam system to perform an absolute calibration of the lunar orbital mass spectrometer which was flown on the Apollo 15 and 16 missions. Tests were performed with several models of the instrument using two test gases, argon and neon in the 10-13-10-9 tort range. Sensitivity to argon at spacecraft orbital velocity was 2.8 × 10 -4 A/ton. enabling partial pressures in the 10-14 torr range to be measured at the spacecraft altitude. Neon sensitivity was nearly a factor of 5 less. The response of the instrument to off-axis beams shows a cosine-to-cosine 2 dependance. Test data support the feasibility of using the lunar orbital mass spectrometer as a tool to gather information about the lunar atmosphere. P R Yeager et al, J Vac Sci Technicol, 10 (2), March-April 1973, 348-354. 22 810. Ionization gauge using a channel electron multiplier for pressures below 10 -12 ton'. (USA) A new ionization gauge of an estimated low pressure limit below 10 - i s torr and of a sensitivity of 2 × 109 torr -1 is presented. The ions, which are produced in an ionizer of conventional design, are extracted through a shield aperture and collected by the funnel-type cathode of a channel electron multiplier. Since the high gain of this multiplier allows the gauge to be operated with an emission current of only several nanoamperes, practically no heat is produced in the gauge. The gauge is mounted on a 4½-in. flange and has approximately the size of a normal Bayard Alpert gauge. A general expression for the low pressure limit of hot filament ionization gauges is given. The results as obtained from this expression for gauges of similar geometry are discussed together with the low pressure limit as found for the new gauge. D Blechschmidt, J Vac Sci Technol, 10 (2), March-April 1973, 376-380. 22 811. Miniaturizing the cold cathode vacuum gauge. (USA) It is possible to greatly reduce the physical dimensions of cold cathode vacuum gauges by increasing the efficiency of the magnetic circuit. The work described was undertaken to establish the limit to which miniaturization could be carried. It is concluded that a gauge 18.5 mm high and weighing 25 g is close to the practical lower limit for gauges of the geometry tested. R O Woods, J Vac Sci Technol, 10 (3), May-June 1973, 433-435. 22:27 812. Experimental investigation of the use of ionization gauges for leak detection. (France) A method of leak detection is described which is applicable to the vacuum system of the C E R N intersecting storage rings after bakeout. The difficulties of access and contamination encountered with conventional leak detectors in this application are overcome by utilising ionization gauges which are already installed in the evacuated chamber. The method is based on the enhanced response of the ionization gauge when the air surrounding the leak is replaced by argon. Detection efficiency is not lower than that obtained with conventional systems. C Bcuvenuti and J C Decroux, Le Vide, 27 (162), Nov-Dec 1972, 243-248 (in French). 427