241
Abstracts 216-226 stabilization is always beneficial and sometimes essential, and that emission stabilities of better than 0.5 per cent at powers up to 20 kW are practicable. (Author) D. Allenden, J. Sci. Instrum. 36, 66-70, Feb. 1959.
of simple design which has proved very satisfactory for the vacuum degassing of small ultra-high vacuum system components. It can achieve a temperature of 1600 °C using 2 kW of power at a pressure of 2 × 10 -~ Torr. Note by E. V. Kornelson and J. O. Weeks, Rev. Sci. lnstrum. 30, 290, April 1959.
27.
L e a k Detectors and L e a k Detection 27
216. Thermal Conductivity Leak Detector. United States. Note by Clarke C. Minter, Rev. Sei. Instrum. 29, No. 9, 793, Sept. 1958. 27 : 40 217. Experiments on flow of gases through leaks. As in 1956 National Vacuum Symposium on Vacuum Technology Transactions (Pergamon Press, London 1957), p. 1-7. A. Nerken, Vakuum-Technik 7, 111-116, 1958. 27 : 37
218. Application of Mass Spectrometry to Vacuum Technique. Survey of different types of mass spectrometers, their applications and limitations as manometers (for measuring partial pressures and vapour pressures). The use of mass spectrometers for the analysis of residual gases in vacuum systems is discussed. Experimental results from many publications including curves and tables are cited and discussed. Finally the survey concludes with a discussion of the application of mass spectrometers to leak detection, the sensitivity obtainable, the working principle and the selection of detector gases. H. Hintenberger and E. D6rnenburg, Vakuum-Technik 7, 121-130, 159-171, 1958.
29,
Miscellaneous 29 : 59
222. Molybdenum Disilicide for High Temperature Sliding. A n investigation into the use of molybdenum disulphide as a lubricant at temperatures up to 700--800 °C in vacua or in air is reported, s.N. G. W. Rowe, Engineer 206, 5357, 497, Sept. 1958. 29 223. Method for Breaking Open Sealed Electronic Devices in
Vacuum. Note by M. G. Charlton and G. M. C. Perkin, J. Sci. Instrum. 36, 49-50, Jan. 1959. 29
224. Five Ways to Automatically Control Pressure for Ejector Vacuum Systems. Graham B. Knight, Chem. Eng. 66, 171-174, March 1959. 29 : 42
225. Use of Borosilicate Glass in Ozonizer Tubes. Richard F. Grossman, Allen C. Bluestein, Science 128, No. 3338, 1578, 19 December 1958. 29
28.
Heating Equipment 28 : 30
219. Electron Bombardment Apparatus for Vacuum Evaporation. Gt. Britain. Certain metals are difficult to evaporate by conventional means because they are of very high melting point, or react with convenient crucible or filament materials. The method described here uses the specimen in the form of a wire, held vertically, the lower end being heated by electron bombardment until a molten drop is formed from which evaporation takes place at a useful rate in favourable cases. (In this connexion, see also Abstract no. 241.) The cathode used here is a single loop of 0.5 m m tungsten wire, supported in a horizontal plane between two shields at cathode potential. These prevent evaporated metal from contaminating the filament : the upper one is pierced by a small hole to allow the emission current to pass. The work to be coated is mounted a little to one side, and the filament is shielded from this as well. The anode wire is mounted from a bellows with three screw adjustments. It is reported that if overheated, the pendant drop may oscillate in shape, with danger of touching the cathode shield plate when .longest. The power supply to the system was controlled only by a hand-operated Variac, and it is mentioned that for a 3 m m zirconium rod 1 0 m A at 2.2kV was n e e d e d ; for a 2.5 m m tantalum rod, 80 m A at 2.2 kV. M.D.A. J. C. Kelly, J. Sci. Instrum. 36, 89-90, Feb. 1959.
226. Le spectrom~tre ~t rayons [~ du centre de physique nucl~aire Liege. ~ Spectrometer of the Nuclear Physics Center of Liege (Belgium). The principles of the [~ spectrometer are recalled. The vacuum installation is described in great detail. The vessel, for secondary emission reasons, is made of aluminium and was manufactured with great care by the " London Aluminium Company." Each end of the tube is linked to side chambers by a slide valve. These chambers are mounted to insure the quick introduction of the [~ sources and of the scintillation crystal. Detailed description of the construction and operation of the valves is given as well as that of the vacuum accessories to insure a very speedy operation needed for the study of low lifetime ~ radioactive elements. The problem set by the vapour pressure of the average scintillation crystal is examined thoroughly and the simplest solution found was the use of a plastic phosphor with a vapour pressure of 10 -8 Torr. The vacuum pumping set is a 1S50 Edwards rotary pump backing a 203 oil diffusion pump. The pressure in the vessel is lower than 5 × 10 -5 Torr. A Penning gauge indicates the pressure and security measures have been taken to prevent damage due to current failure, heating element of the oil diffusion pump failure, or cooling water failure. M. Gueben, M. Legros and, Rev. Soc. Roy. Belge lngrs, et lndus. 27-35, 1957.
28
220. Concerning a Large Capacity Uranium Melting Furnace. H. Hardung-Hardung, Vakuum-Technik 7, 135-137, 1958.
29 : 19 : 30
Obtaining Low Orders of Interference in Measuring Film Thicknesses by Multiple Beam Interferometry. Abstr. No. 175. 28
29 : 19 : 51
221. High Temperature Laboratory Vacuum Furnace. Canada. This note describes a small resistance heated furnace
Ultraviolet Transmission Properties of Conducting Coatings on Glass.
Abstr. No. 176.