Classified Abstracts 742--751 291

Articles on ferromagnetic thin films.

Double barrier in thin film triodes. 723.

33 742. Some transient characteristics of electrically heated tungsten filaments. India. Temperature-time characteristics of tungsten filaments heated electrically under constant voltage in vacuum have been analysed. The analysis is carried out over the temperature range 300-2500°K, taking into account the actual variations with temperature of the various parameters involved, as reported by Jones and Langmuir (1927). The analysis leads to the con- clusion that the temperature-time relationship is exponential th roughout the range. The time constant is shown to be proport ional to the diameter of the filament and Tf -4"2 where Tf is the final temperature of the filament. The results of the analysis are applied to derive the voltage variations (continuous and discrete types) required to keep the transient current within specified limits during the rapid switching on of filaments as met with in high power thermionic valves. (Authors)

K. C. Gupta and M. Satyam, J. Sci. Instrum., 40 (5), May 1963, 244-246.

33 743. Simulated black body absorber for measuring the output of lasers. U.S.A. An evacuated chamber with a sapphire window to admit radiation on to the inside of a blackened metal cone, whose temperature rise can he measured with a plat inum resis- tance thermometer is described. It is stated that an energy of 0.01 J can be measured. (Authors, modified)

S. Koozekanani , P. P. Debye, A. Krutchkoff and M. Ciftan, Proc. Inst. Radio Engrs, 50, Feb. 1962, 207.

33 : 30 744. Instrument for observation of magnetization vector position in thin magnetic films. (U.S.A.) C. J. Bader and D. M. Ellis, Rev. Sci. Instrum., 33 (12), Dec. 1962, 1429-1435.

33 : 30 745. Display of rotational switching characteristics of magnetic thin films. (U.S.A.) J. P. Smith, Rev. Sci. Instrum., 33 (12), Dec. 1963, 1401-1405.

33 : 41 746. Common epitaxial features of various thin film textures. (Great Britain) D. A. Brine and R. A. Young, Phil. Mag., 8 (88), April 1963, 651-652.

33 : 30 Ferromagnetic thin films and ferromagnetic resonance. See Abstr. No. 728.

33 : 30 See Abstr. No. 727.

33 : 30 (U.S.A.) See Abstr. No.

33 : 30 Impact evaporation and thin film growth in a glow discharge. See Abstr . No. 721.

33 : 22 Theory of a frequency dependent background current in the Redhead r.f. mass spectrometer. See Abstr. No. 709.

33 : 19 How lasers work. See Abstr. No. 700.

33 : 18 Impuisive coronal and the prebreakdown mechanism of long sparks. See Abstr. No. 698.

3 3 : 1 8 Studies of the discharge mechanism in a co-axial flash X-ray. See Abstr. No. 696.

3 3 : 1 8 Thin film cold cathodes. See Abstr. No. 695.

33 : 16 Electrical storage and hydrogen transfer between electrode of palladium and palladium alloys. See Abstr. No. 689.

34. H i g h Altitude and Space Technology

34 • 41 747. Tensile tests of metals under high vacuum conditions. U.S.S.R. Apparatus has been built at the Baykov Institute of Metallurgy, Moscow, for testing the tensile strength of metals under high vacuum and temperature up to 2000°C. The cylin- drical heating element of the furnace surrounding the specimen is made of tantalum to prevent contamination, w . J . s .

Anon., New Scientist, 18 (335), 18 April 1963, 154.

35. Impregnation and Potting

748. Impregnating and stoving plant. (Great Britain) Anon., Engineer, 214, 3 Aug. 1962, 205.

35

36. Drying, Degassing and Concentration

36 749. Compact laboratory food freeze dryer. (Great Britain) Anon., Engineer, 214, 23 Nov. 1962, 898.

36 : 37 Notes on the technology of steel degassing. See Abstr. No. 754.

3 6 : 1 3 : 2 0 Combination of vacuum pumps for the evacuation of vapours in the pressure range 50-10-2; tort. See Abstr. No. 687.

37. M e t a l l u r g y , I n o r g a n i c Chemistry, Analytical Chemistry

37 : 41 750. Vacuum decarburization and nitriding of ferromanganese. (Poland) H. Zak and Z. Kulinsky, Prace Instytuton Hutniczych, 13 (1), (1961), 27-36.

37 : 41 : 53 751. Some problems of vacuum metallurgy. U.S.S.R. Three types of vacuum furnaces are at present in use : induction, arc and electron beam. Electron beam melting of metals combines the advantage of a vacuum induction melting furnace in which the liquid metal is continuously under vacuum and the advantage of a vacuum arc furnace which has no ceramic crucible which can form a source of contamination. The author is of the opinion that in the near future the capacity of electron beam furnaces will be greatly increased so as to equal that of present day arc furnaces. After a survey of the effect of pressure on the kinetics of metallurgical reactions, the author describes in detail the methods available at present for the treatment of liquid steel in vacuum. These a r e : (1) Ladle degassing; (2) Stream degassing ; (3) Vacuum lifter process; (4) Circulating lifter process ; and (5) Ladle degassing with bot tom bubbling.

There is no evidence of any marked difference in the end product obtained by the various methods, and the choice of any one will depend on output required and pumping facilities available. The ladle method combined with steam ejector vacuum pumps appears to the author to present special advan- tages, w . J . s .

Samarin, Le Vide, 17 (97), Jan. 1962, 53-71.