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509. Investigation of outgassing and evaporation of cathodes with dense oxide coating prepared by the method of plasma deposition
Classified abstracts 501--510 5 to 7 mm, current of 0.1 to 3 A, and electron energy of 1 to 4 keV, was injected into the discharge chamber. The background pressure of the vacuum system was 3 × 10-6 torr. The magnetic field was varied from 3 to 6.5 kG. As the working gas, argon, krypton, xenon or molybdenum vapour were admitted into the working chamber. A magnetic analyzer was used for analysis of charge composition of ions. The highest fraction of multicharged ions is observed at the hightemperature region of discharge. A method of generation of multicharged ions is presented which is based on utilization of plasmabeam discharge. A I Vladimirnv et al, Zh Tekh Fiz, 41 (6), 1971, 1141-1145 (in Russian). 18 501. Elastic interactions and recombination of charged particles in potassium discharge plasma. (USSR) Some parameters of basic interactions in a low-temperature, weakly ionized potassium plasma are determined on the basis of measurement of properties of positive column of arc discharge in potassium vapour. The transport cross section of electron scattering by potassium atoms is determined in the electron temperature range of 3000 to 9000°K. Mobility of K + ions in potassium vapour is determined at 500°K with the aid of diffusion and plasma disintegration methods. The obtained dependence of the recombination coefficient at potassium vapour pressure of 8 × 10-3 torr on electron concentration and temperature agrees with the results of calculations. D Ya Dudko et al, Zh Tekh Fiz, 41 (6), 1971, 1164-1169 (in Russian). 18 502. Development of low-voltage are discharge in caesium vapour. I. Development of discharge with formation of spherical plasma cluster. (USSR) The development of a low-voltage arc discharge with formation of a spherical plasma cluster in caesium vapour is investigated as a function of cathode temperature, caesium vapour pressure in the range 5 × 10 -3 to 5 × 10 -2 torr, geometry of discharge space and, intensity of magnetic field. A I Kiryushenko and M A Lebedev, Zh Tekh Fiz, 41 (6), 1971, 11701173 (in Russian). 18 503. Angular dependence of the secondary electron emission characteristics of single crystal niobium. (USSR) The results of experimental investigation in vacuum of the dependences of the secondary electron emission coefficients and the coefficients of inelastic reflection on the incidence angle of primary electrons on niobium single crystal faces, in a broad range of primary electron energy from 200 eV to 10 keV, are considered. It is found that changes in the fine structure of the curves of secondary emission coefficients as a function of primary electron energy are caused by the changes in the fine structure of the curves of inelastically reflected electrons. Energy spectra of secondary electrons are examined at different incidence angles of primary electrons. A R Shuiman and V V Korablev, Electronic Technology, Scient-Techn Collect, Electron-beam and Photoelectron Devices, No 1, 1971, 68-73 (in Russian). 18 504. Influence of electric field and current on the evaporation rate of the barium component from an oxide cathode. (USSR) Evaporation of coating materials, and especially of the barium component, is an important factor limiting the life of an oxide cathode. Emission of the oxide cathode begins to decrease at a loss of 2 per cent of active material of the coating. Investigation of physical and chemical processes influencing evaporation of coating material and leading to a decrease of the working temperature of oxide cathode has been carried out. The evaporation rate of barium was measured by the integral Becker method. A tungsten filament 90 #m in diameter, previously degassed by heating to 2000°C, was for some time exposed at room temperature to the evaporation products from an oxide cathode. The experiments have shown that electric field and current influence the evaporation rate of the barium component from oxide coating. The current flow to a probe in the cathode coating results in an additional dissociation of the oxide. The experimental results demonstrate the presence of electric transport of ions in the coating of oxide cathode. V M Tarakovskiy and V P Vasilev, lzv Akad Nauk Uzbec SSR Ser Fiz Mat Nauk. No 3. 1971, 48-52 (in Russian).
18 505. Approximative analysis of the energy characteristics of a glow discharge. (USSR) The results of approximative analysis of the energy characteristics of a high-voltage glow discharge, employed as a heating source, are presented. It is shown that to improve heating of the anode, the coefficient of electron emission from the cathode should be higher than 3 and the cathode-anode distance should be of the order of the electron free path. These conditions are well fulfilled at high-voltage discharges at low pressures with cathodes covered by refractory oxides. A A Novikov and V I Melnik, Vestn Kiev Polytekh Inst Ser Radioelektron, No 8, 1971, 61-64 (in Russian). 18 506. Non-selfmaintaining discharge in a Penning tube. (USSR) It is known that initiation of a Penning discharge in a cold cathode tube has a two-stage character. The first stage has the form of ignition of a non-selfmaintaining avalanche discharge which turns into a selfmaintalning avalanche discharge. Two stable stages of discharge ignition in the Penning cell were found. The experiments were performed with a Penning cell having 15 mm radius and the height of the anode and the distance between the cathodes were equal to 19 mm. The hydrogen pressure was varied in the range of 10 -e to 10-a torr and the discharge current was measured from 2 × 10-18 A. R F Mukhamedov, Zh Tekh Fiz, 41 (10), Oct 1971, 2241-2244 (in Russian). 18 507. Thermal processes in layer cathodes under the action of an electric arc. (USSR) An axially symmetric problem of heating of a layer cathode is solved using a computer. Development of the trace of arc on the layer, the fraction of energy of evaporation in the energy balance, and other effects are considered on a basis of the calculations. G S Belkin, Inzh Fiz Zh, 21 (1), 1971, 127-131 (in Russian) 18 508. Angular distributions of the field ion current. (USSR) It is experimentally shown that at sufficiently high potentials of a point emitter, the dependence of the field ion current on the polar angle has a maximum in the range 30 to 40 °. A theoretical calculation, based on the assumption, that neutral particles come to the ionization region only from the volume, shows that the shape of the angular distribution is fully determined by geometry of the emitter. I V Goldenfeld and V A Nazarenko, Ukr Fiz Zh, 16 (7), 1971, 10761080 (in Ukrainian). 18 509. Investigation of outgassing and evaporation of cathodes with dense oxide coating prepared by the method of plasma deposition. (USSR) Using a highly sensitive mass spectrometric method, outgassing and evaporation of constituents of an oxide cathode, with dense coating of three-component composition, and prepared by the method of plasma deposition, are investigated. The emission properties of these oxide cathodes are also studied. It is shown that at the moment of deposition of the layer, the coating is composed of oxides of alkalineearth metals. The small amount of released C02 and the relatively low temperature required for cathode outgassing result in preservation of a considerable excess of metal in the oxide layer. The emission properties of the investigated cathodes are similar to conventional oxide coating on passive core. G Ya Pikus et al, Electronic Technology, Scient-Tech Collect, Receiving Tubes, No 1, 1971, 11-19 (in Russian). 18 510. Influence of carbonate decomposition conditions on evaporation of the barium component of an oxide cathode. (USSR) Evaporation of the barium component was investigated during the thermal treatment of oxide cathode coating in vacuum and causes of considerable Ba evaporation are discussed. Evaporation of the barium component during the decomposition process of carbonates was investigated using the radioactive isotope Ba 1~° incorporated in barium carbonate. It is found that, on carbonate decomposition, only slight evaporation of the barium component takes place and it is independent of the pressure in the device. After heating the device to high temperature (420°C), the barium evaporation increases considerably. This effect is explained by materials produced by the heating of the glass envelope interacting with the coating components and forming volatile components. This is confirmed by the formation 165
18 505. Approximative analysis of the energy characteristics of a glow discharge. (USSR) The results of approximative analysis of the energy characteristics of a high-voltage glow discharge, employed as a heating source, are presented. It is shown that to improve heating of the anode, the coefficient of electron emission from the cathode should be higher than 3 and the cathode-anode distance should be of the order of the electron free path. These conditions are well fulfilled at high-voltage discharges at low pressures with cathodes covered by refractory oxides. A A Novikov and V I Melnik, Vestn Kiev Polytekh Inst Ser Radioelektron, No 8, 1971, 61-64 (in Russian). 18 506. Non-selfmaintaining discharge in a Penning tube. (USSR) It is known that initiation of a Penning discharge in a cold cathode tube has a two-stage character. The first stage has the form of ignition of a non-selfmaintaining avalanche discharge which turns into a selfmaintalning avalanche discharge. Two stable stages of discharge ignition in the Penning cell were found. The experiments were performed with a Penning cell having 15 mm radius and the height of the anode and the distance between the cathodes were equal to 19 mm. The hydrogen pressure was varied in the range of 10 -e to 10-a torr and the discharge current was measured from 2 × 10-18 A. R F Mukhamedov, Zh Tekh Fiz, 41 (10), Oct 1971, 2241-2244 (in Russian). 18 507. Thermal processes in layer cathodes under the action of an electric arc. (USSR) An axially symmetric problem of heating of a layer cathode is solved using a computer. Development of the trace of arc on the layer, the fraction of energy of evaporation in the energy balance, and other effects are considered on a basis of the calculations. G S Belkin, Inzh Fiz Zh, 21 (1), 1971, 127-131 (in Russian) 18 508. Angular distributions of the field ion current. (USSR) It is experimentally shown that at sufficiently high potentials of a point emitter, the dependence of the field ion current on the polar angle has a maximum in the range 30 to 40 °. A theoretical calculation, based on the assumption, that neutral particles come to the ionization region only from the volume, shows that the shape of the angular distribution is fully determined by geometry of the emitter. I V Goldenfeld and V A Nazarenko, Ukr Fiz Zh, 16 (7), 1971, 10761080 (in Ukrainian). 18 509. Investigation of outgassing and evaporation of cathodes with dense oxide coating prepared by the method of plasma deposition. (USSR) Using a highly sensitive mass spectrometric method, outgassing and evaporation of constituents of an oxide cathode, with dense coating of three-component composition, and prepared by the method of plasma deposition, are investigated. The emission properties of these oxide cathodes are also studied. It is shown that at the moment of deposition of the layer, the coating is composed of oxides of alkalineearth metals. The small amount of released C02 and the relatively low temperature required for cathode outgassing result in preservation of a considerable excess of metal in the oxide layer. The emission properties of the investigated cathodes are similar to conventional oxide coating on passive core. G Ya Pikus et al, Electronic Technology, Scient-Tech Collect, Receiving Tubes, No 1, 1971, 11-19 (in Russian). 18 510. Influence of carbonate decomposition conditions on evaporation of the barium component of an oxide cathode. (USSR) Evaporation of the barium component was investigated during the thermal treatment of oxide cathode coating in vacuum and causes of considerable Ba evaporation are discussed. Evaporation of the barium component during the decomposition process of carbonates was investigated using the radioactive isotope Ba 1~° incorporated in barium carbonate. It is found that, on carbonate decomposition, only slight evaporation of the barium component takes place and it is independent of the pressure in the device. After heating the device to high temperature (420°C), the barium evaporation increases considerably. This effect is explained by materials produced by the heating of the glass envelope interacting with the coating components and forming volatile components. This is confirmed by the formation 165