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Thermoelectron emission from tungsten in a stream of Ba and Cs atoms
Classified
abstracts
936-947
16 936. Electron impact desorption of carbon monoxide from tungsten. (Italy)* It has been established that CO is adsorbed on tungsten in at least three different states of binding. By measurement of desorbed ion currents, the ion energy distribution was derived and used to estimate the relative populations in the adsorbed states. Desorption crosssections are in reasonable agreement with values from the work of others, but show significant difference between the values for CO cross-sections on tungsten and molybdenum. It is considered that the experimental evidence indicates a larger electron impact desorption cross-section for molybdenum than for tungsten, despite the similarity in crystal structure. (Canada) P A Redhead, Nuovo Cimento Suppl, 5 (2), 1967, 586-597. 16 937. Instructions between low-energy electrons and adsorbed carbon monoxide. (Italy)* Desorption from carbon monoxide adlayers on molybdenum were investigated using a resonant-ion mass spectrometer device employing 5 grids and allowing direct mass analysis of desorbed ions. At CO pressures of 1O-4 newtons/ma, Of and CO+ ions were clearly recognized in the spectrum arising from 100 eV electron bombardment. Measurements of the energy losses of 20 eV impinging electrons and surface potential measurements were consistent with previous data obtained on the adsorption kinetics of CO on transition metals. (France) D ADegras and J Lecante, Nuovo Cimento Suppl, 5 (2), 1967,598 -605. 16 938. Interaction of electrons with adsorbed water. (Italy)+ The effects of low-energy electron bombardment of polycrystalline nickel and tungsten ribbons, during exposure to water, was investigated by the dynamic sorption method. Mass spectrometric measurements indicated that the water disappears and molecular hydrogen and oxygen are desorbed. The results for tungsten indicate that atomic oxygen is also evolved. The investigational method allows study of electronic desorption under steady-state conditions and measurement of the adsorption properties of the metals. Water pressure ranged from 10-O to 1O-Btorr and electron current densities from 1O-5 to lO-p A/cm?. The metal ribbon temperature rose to 200°C after bombardment with 10-a A/cm2 at 400 V and all measurements were performed at this temperature. (Germany) A Klopfer, Nuovo Cimento Suppl, 5 (2), 1967, 606-611. 16 : 18 939. Thermoelectron emission from tungsten in a stream of Ba and Cs atoms. (USSR) A method is described for the investigation of thermoelectron emission from a metal simultaneously under the action of two streams of neutral atoms. In this way, the emission from tungsten for barium streams of 5 x 10ia to 1Ol6 at/cm%ec and caesium streams of 4 x 1Ol5 to 5x 10” at/cm%ec was determined. The emission proaerties of tungsten are primarily determined by the barium atoms and only a weak caesium influence was observed. V G Baxanov et al, Fiz Tverd Telu, 10 (2), Feb 1968, 507-512 (in Russian). 16 940. Study of potassium ion adsorption on molybdenum surfaces. (USSR) By means of a modulated atomic beam, the desorption temperatures for positive potassium ions from polycrystalline molybdenum surfaces were determined. They were found to increase linearly from 1.82 eV at 950°K to 2.1 eV at 1200°K. N G Ban’kovskiy et al, Fiz Tverd Tela, 10 (l), Jan 1968, 153-158 (in Russian). 17. THERMODYNAMICS 17 941. Study of thermal dissociation of alkaline-earth oxides ln high vacuum. (USSR) BaO and SrO samples were heated at 1O-s torr and the components of evaporation were analyzed by a mass spectrometer. For barium oxide, the predominant component is BaO with an evaporation rate of about 2x lo-* g.cm-2sec-1 at 1300°K. Quantities of evaporated Ba and 0, are only of several per cent of the BaO and the ratio of evaporated Ba molecules to 0, molecules is about 2 at 1150°K. At higher temperatures the BaO sample is enriched by barium as 426
oxygen evaporates more rapidly until some equilibrium state is reached. Strontium oxide is evaporated much more slowly with basic components Sr and 0, but the character of the process is the same as for BaO. G Ya Pikus et al, Fiz Tverd Telu, 10 (l), Jan 1968, 125-134 (in Russian). 17 942. Electronographic study of a thermally treated corundum surface. (USSR) The influence of therma treatment on a corundum surface Iayer damaged by mechanical processing was investigated by means of electronography. Corundum was baked at 1O-6 torr or in inert atmosphere at temperatures of up to 2100°C. Comparing difraction pictures with the curves of evaporation at different temperatures it is shown that the basic process occurring during thermal treatment is recrystallization of the damaged layer, and not evaporation. S A Semiletov et al, Fiz Tverd Tela, 10 (l), Jan 1968, 71-76 (in Russian). 18. GASEOUS ELECTRONICS 18 : 16 Field emission studies of oxygen, hydrogen and nitrogen by a molybdenum tip. See abstract number 930. 18 : 16 Thermoelectron emission from tungsten in a stream of Ba and Cs atoms. See abstract number 939. 18 : 16 943. Inert gas ion bombardment induced work function changes In polycrystalline tungsten and gold ribbon. (Great Britain) Polycrystalline tungsten and gold ribbon targets were bombarded with low-energy (100 eV-600 eV) inert gas ions of helium, argon and krypton. The thermionic work function of the target was monitored before and after bombardment by a retarding potential field method in a diode valve with the target as the anode. Work function recovery was monitored during post-bombardment stop annealing studies. Bombardment-induced work function increases of several tenths of an electron volt in tungsten were recovered in annealing stages corresponding to surface vacancy migration and gas release from the surface regions. Smaller work function reductions in gold targets were annealed in stages corresponding to damage diffusion, normal diffusion and gas diffusion processes. R P W Lawson and G Carter, Vacuum, 18 (4), April 1968.205-211. 18 944. Discrimination and amplification of difference frequency in a plasma waveguide, by an electron beam. (USSR) Discrimination and amplification of difference frequency is theoretically analyzed for plasma excited in a waveguide by the passage of an electron beam through a neutral gas. N Ya Kotsarenko and A M Fedorchenko, Rudiotekh Elektron, 12 (12), 1967, 2162-2170 (in Russian) 18 945. Determination of the effective emitting surface of an oxide cathode. (USSR) By a method employing a longitudinal magnetic field for measurement of the effective emitting surface of oxide cathodes, it was found that for porous oxide coatings with a small accelerating voltage near to the surface, the emission may be 4 times higher than that from non-porous cathodes with the same work function. This effect is caused by extraction of electrons from the pores. The possibility of emission current control outside of the space-charge limited region by a small accelerating voltage in the vicinity of the cathode surface, is discussed. M V Krasin’kova et al, Radiotekh Elektron, 12 (12), 1967, 2197-2206 (in Russian). 946. The work function of alloys of rhenium with scandium. (USS: Thermionic emission work functions of 3.0 eV and 3.35 eV were measured for rhenium-scandium alloys containing 0.8 and 5 per cent of scandium respectively. A minimal value of 2.85 eV was determined at 30 per cent scandium. Below 1600°K no influence of temperature was observed. A A Gugnin and 0 Kb Khamidov, Radiotekh Elektron, 12 (12), 1967, 2270 (in Russian). 18 947. Emission properties of thin film tunnel cathodes. (USSR) Thin film systems of Cr-SiO$-Al and Ni-Al,O,-Au were prepared by
abstracts
936-947
16 936. Electron impact desorption of carbon monoxide from tungsten. (Italy)* It has been established that CO is adsorbed on tungsten in at least three different states of binding. By measurement of desorbed ion currents, the ion energy distribution was derived and used to estimate the relative populations in the adsorbed states. Desorption crosssections are in reasonable agreement with values from the work of others, but show significant difference between the values for CO cross-sections on tungsten and molybdenum. It is considered that the experimental evidence indicates a larger electron impact desorption cross-section for molybdenum than for tungsten, despite the similarity in crystal structure. (Canada) P A Redhead, Nuovo Cimento Suppl, 5 (2), 1967, 586-597. 16 937. Instructions between low-energy electrons and adsorbed carbon monoxide. (Italy)* Desorption from carbon monoxide adlayers on molybdenum were investigated using a resonant-ion mass spectrometer device employing 5 grids and allowing direct mass analysis of desorbed ions. At CO pressures of 1O-4 newtons/ma, Of and CO+ ions were clearly recognized in the spectrum arising from 100 eV electron bombardment. Measurements of the energy losses of 20 eV impinging electrons and surface potential measurements were consistent with previous data obtained on the adsorption kinetics of CO on transition metals. (France) D ADegras and J Lecante, Nuovo Cimento Suppl, 5 (2), 1967,598 -605. 16 938. Interaction of electrons with adsorbed water. (Italy)+ The effects of low-energy electron bombardment of polycrystalline nickel and tungsten ribbons, during exposure to water, was investigated by the dynamic sorption method. Mass spectrometric measurements indicated that the water disappears and molecular hydrogen and oxygen are desorbed. The results for tungsten indicate that atomic oxygen is also evolved. The investigational method allows study of electronic desorption under steady-state conditions and measurement of the adsorption properties of the metals. Water pressure ranged from 10-O to 1O-Btorr and electron current densities from 1O-5 to lO-p A/cm?. The metal ribbon temperature rose to 200°C after bombardment with 10-a A/cm2 at 400 V and all measurements were performed at this temperature. (Germany) A Klopfer, Nuovo Cimento Suppl, 5 (2), 1967, 606-611. 16 : 18 939. Thermoelectron emission from tungsten in a stream of Ba and Cs atoms. (USSR) A method is described for the investigation of thermoelectron emission from a metal simultaneously under the action of two streams of neutral atoms. In this way, the emission from tungsten for barium streams of 5 x 10ia to 1Ol6 at/cm%ec and caesium streams of 4 x 1Ol5 to 5x 10” at/cm%ec was determined. The emission proaerties of tungsten are primarily determined by the barium atoms and only a weak caesium influence was observed. V G Baxanov et al, Fiz Tverd Telu, 10 (2), Feb 1968, 507-512 (in Russian). 16 940. Study of potassium ion adsorption on molybdenum surfaces. (USSR) By means of a modulated atomic beam, the desorption temperatures for positive potassium ions from polycrystalline molybdenum surfaces were determined. They were found to increase linearly from 1.82 eV at 950°K to 2.1 eV at 1200°K. N G Ban’kovskiy et al, Fiz Tverd Tela, 10 (l), Jan 1968, 153-158 (in Russian). 17. THERMODYNAMICS 17 941. Study of thermal dissociation of alkaline-earth oxides ln high vacuum. (USSR) BaO and SrO samples were heated at 1O-s torr and the components of evaporation were analyzed by a mass spectrometer. For barium oxide, the predominant component is BaO with an evaporation rate of about 2x lo-* g.cm-2sec-1 at 1300°K. Quantities of evaporated Ba and 0, are only of several per cent of the BaO and the ratio of evaporated Ba molecules to 0, molecules is about 2 at 1150°K. At higher temperatures the BaO sample is enriched by barium as 426
oxygen evaporates more rapidly until some equilibrium state is reached. Strontium oxide is evaporated much more slowly with basic components Sr and 0, but the character of the process is the same as for BaO. G Ya Pikus et al, Fiz Tverd Telu, 10 (l), Jan 1968, 125-134 (in Russian). 17 942. Electronographic study of a thermally treated corundum surface. (USSR) The influence of therma treatment on a corundum surface Iayer damaged by mechanical processing was investigated by means of electronography. Corundum was baked at 1O-6 torr or in inert atmosphere at temperatures of up to 2100°C. Comparing difraction pictures with the curves of evaporation at different temperatures it is shown that the basic process occurring during thermal treatment is recrystallization of the damaged layer, and not evaporation. S A Semiletov et al, Fiz Tverd Tela, 10 (l), Jan 1968, 71-76 (in Russian). 18. GASEOUS ELECTRONICS 18 : 16 Field emission studies of oxygen, hydrogen and nitrogen by a molybdenum tip. See abstract number 930. 18 : 16 Thermoelectron emission from tungsten in a stream of Ba and Cs atoms. See abstract number 939. 18 : 16 943. Inert gas ion bombardment induced work function changes In polycrystalline tungsten and gold ribbon. (Great Britain) Polycrystalline tungsten and gold ribbon targets were bombarded with low-energy (100 eV-600 eV) inert gas ions of helium, argon and krypton. The thermionic work function of the target was monitored before and after bombardment by a retarding potential field method in a diode valve with the target as the anode. Work function recovery was monitored during post-bombardment stop annealing studies. Bombardment-induced work function increases of several tenths of an electron volt in tungsten were recovered in annealing stages corresponding to surface vacancy migration and gas release from the surface regions. Smaller work function reductions in gold targets were annealed in stages corresponding to damage diffusion, normal diffusion and gas diffusion processes. R P W Lawson and G Carter, Vacuum, 18 (4), April 1968.205-211. 18 944. Discrimination and amplification of difference frequency in a plasma waveguide, by an electron beam. (USSR) Discrimination and amplification of difference frequency is theoretically analyzed for plasma excited in a waveguide by the passage of an electron beam through a neutral gas. N Ya Kotsarenko and A M Fedorchenko, Rudiotekh Elektron, 12 (12), 1967, 2162-2170 (in Russian) 18 945. Determination of the effective emitting surface of an oxide cathode. (USSR) By a method employing a longitudinal magnetic field for measurement of the effective emitting surface of oxide cathodes, it was found that for porous oxide coatings with a small accelerating voltage near to the surface, the emission may be 4 times higher than that from non-porous cathodes with the same work function. This effect is caused by extraction of electrons from the pores. The possibility of emission current control outside of the space-charge limited region by a small accelerating voltage in the vicinity of the cathode surface, is discussed. M V Krasin’kova et al, Radiotekh Elektron, 12 (12), 1967, 2197-2206 (in Russian). 946. The work function of alloys of rhenium with scandium. (USS: Thermionic emission work functions of 3.0 eV and 3.35 eV were measured for rhenium-scandium alloys containing 0.8 and 5 per cent of scandium respectively. A minimal value of 2.85 eV was determined at 30 per cent scandium. Below 1600°K no influence of temperature was observed. A A Gugnin and 0 Kb Khamidov, Radiotekh Elektron, 12 (12), 1967, 2270 (in Russian). 18 947. Emission properties of thin film tunnel cathodes. (USSR) Thin film systems of Cr-SiO$-Al and Ni-Al,O,-Au were prepared by