337. A cathode unit

Classified abstracts 331-340 33 331. Photoemission from germanium with Ai903 coverage. (USSR) The spectral distribution of photoemission from an etched (111) surface of single crystal n-type germanium covered by Al=Oa, was investigated. Gradual coverage of germanium by Al20~ and photoemission measurements were performed in sealed-off devices at a pressure of 2 × 10-9 torr. It was found that, at all tested coverages of aluminium oxide, the photoemission work function of germanium does not change its value. Also the character of the distribution of the quantum yield from germanium photoemission remains unchanged at all aluminium oxide coverages, but as coverage thickness increases, the photoemission is diminished. The effect of the photocurrent decrease with increasing aluminium oxide thickness can be explained by an increase in the absorption and scattering of photoelectrons in the aluminium oxide layer. The constancy of the photoelectron work function indicates that the dielectric layer coverage does not change the band positions on the germanium surface. The aluminium oxide molecules are tightly bonded and they do not disturb the surface properties of germanium. Aluminium oxide coverage stabilizes the surface condition of the semiconductor, leaving the inner potential in elementary surface cells of the crystal and the electron affinity unchanged. It can be used for protection of the semiconductor surface. A N Arseneva-Geil and A Belal, Fiz Tverd Tela, 12 (7), July 1970, 21912192 (in Russian). 33 332.Photoemission from silicon and germanium at barium coverage. (USSR) Effect of barium coverage on the photoemission from silicon and germanium is investigated. Measurement of the energy distribution of photoelectrons and the spectral distribution of the quantum yield of the photoemission from etched (111) surfaces of single crystals of p-type silicon and germanium, during gradual deposition of barium, is performed in sealed-off devices at 10 -9 torr. Results of measurement of the spectral distribution of the quantum yield of photoemission from silicon and germanium showed that the work function is gradually decreased as the barium coverage increases, and, on the curves of spectral distribution of the quantum yield, a structure is formed corresponding to the band structure of these materials. In the energy distribution of photoelectrons with barium coverage, a more complex structure is observed than with caesium coverage. New maxima are formed, which correspond to direct interband transitions. It is shown that barium coverage results in lower photoelectron scattering as compared to caesium coverage. A Belal and A N Arseneva-Geil, Fiz Tverd Tela, 12 (7), July 1970, 21902191 (in Russian). 33 333. Method of preparing thin-walled cathode bases. (USSR) Difficulties arising from the conventional method of moulding thinwalled cathode bases of relatively small size by introducing plastic materials into a correspondingly-shaped mould are recounted. An improved version of this method, in which the plastic material is introduced in the form of simple cylindrical rods, is proposed. This arrangement facilitates the moulding process by minimizing the change in shape of the plastic so introduced, and preventing undue outflow from the ends, with consequent wastage. N A Iofis et al, USSR Patent, No 258,468, appl lOth July 1967, publd lOth April 1970. 33:41 334. A cathode. (USSR) A cathode made from an alloy of rhenium with lanthanum (0.5-35 at/ per cent La) is proposed; it has a work function of 2.8 eV and a secondary-emission coefficient of 2. i, the working temperature being no higher than 1600°C. This alloy may be used as a source of electrons in magnetrons and thermionic converters; its emission characteristics are stable under electron bombardment. Lanthanum being liable to rapid oxidation, it may prove desirable to use lanthanum compounds (LaH3, LaN, La203, LaF3, LaSig, LAB6, or LaC2 as original materials for preparing the alloy. A A Gugnin et al, USSR Patent, No 245,925, appl 15th Dec 1964, publd 12th May 1970. 33 : 41 335. A titanium-base alloy. (USSR) A titanium alloy for use in electrical-vacuum apparatus is described. Apart from titanium, the material contains 10-20 per cent of niobium and traces (0.05-0.5 per cent) of rare-earth metals, the latter consti-

196

tuting an innovation, and correspondingly improving the heat resistance and thermionic emission. Thus an alloy containing 15 per cent niobium and 0.1 per cent cerium heated by means of an electric current of about 40 A (heating power 12 W/cm 9) has a thermionic emission of 35 mA/cm 9 and an evaporation rate of 6-7.10 -8 g/cmg.sec. The alloy may easily be cold-rolled or drawn at room temperature; it may be welded at about 1000°C. T I Zelentsov et al, USSR Patent, No 256,275, appl 3rd Dec 1965, publd 7th April 1970. 33 336. Semi-automatic device for making frame-type grids. (USSR) An improved semi-automatic device for the manufacture of frametype (electronic-valve) grids is proposed. The feed mechanism is specially adapted to ensure correct positioning of the laminations, incorporating an adjustable support for this purpose. In this way the quality of the grids may be improved without complicating the device as a whole. Reliability is improved by feeding the laminations into the shaping element directly from the initial feed mechanism, thus eliminating intermediate stages. Detailed diagrams clarifying the operating principles of the system are presented. V A Burlyaev and N A Konyakhin, USSR Patent, No 245,213, appl 24th March 1966, publd lOth Nov 1969. 33 337. A cathode unit. (USSR) A new type of cathode unit for electron guns is proposed; it differs from conventional units in that both the main and the auxiliary cathodes are made in the same (disc) shape. A current sufficient to initiate thermionic emission from the auxiliary cathode is first passed; this creates an electron beam, which is then acted upon by an alternating voltage applied between the cathodes; the electron beam heats the main cathode and initiates thermionic emission from the latter, the heating current to the auxiliary current then being automatically disconnected. This arrangement, together with the carefully-chosen geometry of the system, reduces loss of heating current and ensures uniform emission. A V Ivlev, USSR Patent, No 247,415, appl 13th Feb 1967, publd 8th Dec 1969. 33 338. High-temperature resonator for studying dielectrics in an inert medium. (USSR) A high-temperature resonator designed for studying the parameters of dielectrics at 20-1600°C (dielectric constant and loss factor) is proposed; it is furnished with a special mechanism for adjusting the position of the dielectrics and hence their degree of coupling with the measuring circuits. Measurements are carried out in an inert gas medium, and the mechanical arrangements are such as to minimize the loss of gas when samples are changed; no protracted evacuation is required before each measurement. Typical loss factors (tan 8) rang~ from 10-4 at room temperature to 10-x near the melting point. A V Antonov et al, USSR Patent, No 248,805, appl 23rd Jan 19682 publd 19th Dec 1969. 33 339. A plane grid for electrical-vacuum devices. (USSR) An improved form of grid for electronic valves and analogous apparatus is described. Existing "parquet"-type grids have some advantages over primitive forms but provide a relatively poor control in the case of short inter-electrode distances. The new grid constitutes a modification in which one or several "bridge" pieces are introduced into each cell; these lie parallel to the greater side of the cell and their cross section is considerably smaUer than that of the main cell bars. This system gives efficient control of the electron flow and increases the general uniformity of the structure. A I Geren, USSR Patent, No 256,091, appl lOth May 1967, pubM 3rd April 1970. 33 340. Apparatus for the pulse conditioning of electrical-vacuum devices. (USSR) An apparatus suitable for the pulse conditioning of a wide range of electrical-vacuum devices (eg radio valves) without resetting for each different type is described. The pulse voltage source (such as a thyratron generator) used for this purpose is connected to the anode of the device under treatment through a separating diode. A pulse voltage is taken to the grid of the device in question from the load of the same generator. A condenser (10-100 pF) is connected across the