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Vacuum system of the Jerevan synchrotron
Classified abstracts 458-467 operation, initially decreases, reaches the first minimum after about 2000 hours, exhibits a maximum after about 3000 hours, and after about 6000 to 7000 hours the transconductance minimum is observed. The effect of the change in the transverse resistance on the decrease of transconductance during the life of the tube was determined using methods of mathematical statistics. After an analysis of the variation in the transverse cathode resistance, a theory based on two independent processes is described, containing in addition to the known process of interface formation, a new process involving formation of a boundary resistance. This process was investigated and after extensive experiments a new hypothesis on its mechanism was established. According to this hypothesis, adsorbed gases are released and fusible admixtures, particularly magnesium, evaporated from the heated cathode nickel and form, against the resistance of the antidiffusion harrier, an excess pressure causing internal recrystallization of nickel and increasing contact resistance by tearing off parts of the oxide coating. J Maehovee, Tesla Electronics, 3 (4), 1970, 109-116. 31 458. Universal device for obtaining and investigating multialkali photocathodes. (USSR) A continuously pumped glass vacuum device is described which enables complex investigation of photocathodes. The device contains a quartz film thickness monitor, an electron gun for photocathode work function determination, arrangement for film conductivity measurement, and a spherical analyzer of photoelectron initial energy. It is also possible to obtain an electron-optical image on a phosphor screen with magnification. B G Popngaev, Materialy Nauchno Tekhn Konfer Sev Kavkaz Gorno Metallur lnst 1968, Ordzhonikidze 1970, 115-116 (in Russian). 31 459. Organisation of statistical checks in the electro-vacuum industry. (USSR) Methods and organisation of statistical checks in the electro-vacuum industry are discussed. E V Nasedkine and N M Mishagin, Materialy Nauchno Tekhn Konfer Sev Kavkaz Gornometallur Inst 1968, Ordzhonikidze 1970, 140-141
(in Russian). 31 460. Microminiaturization of hot cathodes for electrovacoum devices. (USSR) Methods for obtaining miniature oxide cathodes with high quality coatings are described. These cathodes require a heating power lower by an order of magnitude than contemporary efficient cathodes for receiving tubes. V N Avdeev et al, Voprosy Konstruir Tekhnol Kontrol lzgotovl Elektrovakuum Prib, Minsk 1970, 9-22 (in Russian). 31 461. Utilization of the self-heating principle for improvement of electron tube efficiency. (USSR) Construction of an efficient electron tube employing the self-heating principle is described. The cathode has a cylindrical form. Two anodes, one inside the cathode and the second anode around the cathode, are used. Volt-ampere characteristics of such electron tubes are measured. A I Vishnevskiy et al, Tr 1-oy Yubileyn Resp Mezhvuz Konfer Probl Povysh Eff'ektivn Elektrovakuumn Prib, 1, Kiev 1970,17-25 (in Russian). 32. NUCLEONICS 32 462. Vacuum system of an accelerator with a small aperture chamber. (USSR) The design of a vacuum system for an accelerator with a small aperture chamber is presented. Construction and performance are described for the vacuum system of a model of the accelerator with an energy of 1 GeV and a chamber aperture of ellipsoidal shape with axis of 16 and 22.4 ram. Residual gas pressures have to be lower than 8 × 10-7 torr. Evacuation is performed by a titanium inn-sorption pump with pumping speed higher than 60 litres/sec at working pressure of 1 × 10-7 torr, and life of 2000 hours. A L Mints and N Ya Basalaeva, Tr Vses Sovechan Uskorit Zaryazh Chastits 1968, 2, Moskva VIN1T1 1970, 549-555 (in Russian). 32 463. Vacuum system of the Jerevan synchrotron. (USSR) The ring vacuum synchrotron chamber contains 48 curved sections, 380 cm long placed in interpole gaps, and 48 straight sections of
248
different constructional shape and purpose. 24 straight sections represent volume resonators. The resonators are of petal shape, constructed of cylinders of sheet copper with a diameter of 160 and length pf 50 cm. The resonator is mounted in a stainless steel vacuum vessel, 190 cm diameter 70 cm long. Two straight sections contain an arrangement for beam introduction. Other sections contain arrangements for beam observation, outlet of accelerated electrons, and inner targets. Each straight section tubulated for pumping. Evacuation is performed in three stages. The VN-4 pumps evacuate the system to pressure of 1 to 0.1 torr. For obtaining pressures of 10-4 to 10-5 torr turbomolecular pumps, TMN-200 type, are used. The working pressure of 10-6 torr is maintained by titanium sputter-ion pumps. G M Martyoguv et al, Tr Vses Sovechaniya Uskorit Zaryazh Chastits 1968, 2, Moskva V1N1T1 1970, 556-559 (in Russian). 32 464. Ultrahigh vacuum pumping system for the VEPP-2 accelerator. (USSR) Initially the working chamber of the VEPP-2 accelerator was pumped by four sorption titanium pumps and oil diffusion pumps. To increase the life of the beam, the ultrahigh vacuum system was modernized. Only oil-free pumps are used for pumping of the inner chamber. The pumping speed of the chamber was increased with the aid of a distributed magnetic discharge pump operating in the magnetic field of the accelerator. Tantalum foil was introduced as a radiation receiver in the chamber. It is found that, after repair of leaks in the system, the electrical discharge pump maintains a pressure lower than 10-5 torr in the chamber during baking. After baking, a pressure of 1 × 10-8 torr is reached. After switching on a voltage of 6 to 7 kV to the distributed pump, the pressure is reduced to 3-5× 10-9 torr. Pressure measurement was performed with the aid of beam life determination at a small beam current. V V Anashin et al, Tr Vses Soveschaniya Uskoritel Zaryazh Chastits 1968, 2, Moskva VIN1T1 1970, 560-563 (in Russian). 33. GENERAL PHYSICS AND ELECTRONICS 33 465. Metal tips produced by electron bombardment. An apparatus is described to transform the end of a wire (tungsten in the vacuum into a fine tip by electron bombardment. Curvature radii at the tip apex down to l0 BX are obtained. The tips are controlled by (I) an optical microscope (2) an electron microscope and (3) a field electron microscope. The interpretation of the process of tip sharpening is based on evaporation, surface diffusion and surface energy in the presence of a temperature gradient caused by the electron bombardment. It seems to use the method for the production and the regeneration of point cathodes in electron microscopes as well as a field emitter in field emission microscopes. M Drechsler and J P Prulhiere, Vacuum, 20 (11), Nov 1970, 491494
(in English and French). 33 466. Quadrupole mass filter: circular rods and peak shapes. (USA) A frequently observed characteristic of quadrupole mass filters is the appearance, at high resolution, of a separate "precursor" peak on the low mass side of each mass peak. Such false precursor peaks are shown to result from the use of round rods (rather than hyperbolic rods) which are common in all commercial instruments. Round rods introduce sixth- and tenth-order terms to the ideal quadrupole field. The amount of sixth-order distortion introduced by the use of circular rods is computed. The equipotential line produced at the surface of a round rod can be represented quite well by a quadrupole field with a large amount of sixth-order distortion. This distortion introduces a resonance line in the Mathieu stability diagram which at high resolution is near the edge of the peak on the low mass side. The resonance line can distort the peak to produce an apparent precursor peak. P H Dawson and N R Whetten, J Vac Sci Technol, 7 (3), May/June 1970, 440441. 33 467. Electron microscopic investigation of the oxide layer formed on the surface of chemically treated germanium single crystals. Effects of some corrosive agents on morphology of the surface oxide layer. (Hungary) The effect of various etching agents containing nitric acid or hydrogen peroxide as oxidant on the morphological and structural parameters
(in Russian). 31 460. Microminiaturization of hot cathodes for electrovacoum devices. (USSR) Methods for obtaining miniature oxide cathodes with high quality coatings are described. These cathodes require a heating power lower by an order of magnitude than contemporary efficient cathodes for receiving tubes. V N Avdeev et al, Voprosy Konstruir Tekhnol Kontrol lzgotovl Elektrovakuum Prib, Minsk 1970, 9-22 (in Russian). 31 461. Utilization of the self-heating principle for improvement of electron tube efficiency. (USSR) Construction of an efficient electron tube employing the self-heating principle is described. The cathode has a cylindrical form. Two anodes, one inside the cathode and the second anode around the cathode, are used. Volt-ampere characteristics of such electron tubes are measured. A I Vishnevskiy et al, Tr 1-oy Yubileyn Resp Mezhvuz Konfer Probl Povysh Eff'ektivn Elektrovakuumn Prib, 1, Kiev 1970,17-25 (in Russian). 32. NUCLEONICS 32 462. Vacuum system of an accelerator with a small aperture chamber. (USSR) The design of a vacuum system for an accelerator with a small aperture chamber is presented. Construction and performance are described for the vacuum system of a model of the accelerator with an energy of 1 GeV and a chamber aperture of ellipsoidal shape with axis of 16 and 22.4 ram. Residual gas pressures have to be lower than 8 × 10-7 torr. Evacuation is performed by a titanium inn-sorption pump with pumping speed higher than 60 litres/sec at working pressure of 1 × 10-7 torr, and life of 2000 hours. A L Mints and N Ya Basalaeva, Tr Vses Sovechan Uskorit Zaryazh Chastits 1968, 2, Moskva VIN1T1 1970, 549-555 (in Russian). 32 463. Vacuum system of the Jerevan synchrotron. (USSR) The ring vacuum synchrotron chamber contains 48 curved sections, 380 cm long placed in interpole gaps, and 48 straight sections of
248
different constructional shape and purpose. 24 straight sections represent volume resonators. The resonators are of petal shape, constructed of cylinders of sheet copper with a diameter of 160 and length pf 50 cm. The resonator is mounted in a stainless steel vacuum vessel, 190 cm diameter 70 cm long. Two straight sections contain an arrangement for beam introduction. Other sections contain arrangements for beam observation, outlet of accelerated electrons, and inner targets. Each straight section tubulated for pumping. Evacuation is performed in three stages. The VN-4 pumps evacuate the system to pressure of 1 to 0.1 torr. For obtaining pressures of 10-4 to 10-5 torr turbomolecular pumps, TMN-200 type, are used. The working pressure of 10-6 torr is maintained by titanium sputter-ion pumps. G M Martyoguv et al, Tr Vses Sovechaniya Uskorit Zaryazh Chastits 1968, 2, Moskva V1N1T1 1970, 556-559 (in Russian). 32 464. Ultrahigh vacuum pumping system for the VEPP-2 accelerator. (USSR) Initially the working chamber of the VEPP-2 accelerator was pumped by four sorption titanium pumps and oil diffusion pumps. To increase the life of the beam, the ultrahigh vacuum system was modernized. Only oil-free pumps are used for pumping of the inner chamber. The pumping speed of the chamber was increased with the aid of a distributed magnetic discharge pump operating in the magnetic field of the accelerator. Tantalum foil was introduced as a radiation receiver in the chamber. It is found that, after repair of leaks in the system, the electrical discharge pump maintains a pressure lower than 10-5 torr in the chamber during baking. After baking, a pressure of 1 × 10-8 torr is reached. After switching on a voltage of 6 to 7 kV to the distributed pump, the pressure is reduced to 3-5× 10-9 torr. Pressure measurement was performed with the aid of beam life determination at a small beam current. V V Anashin et al, Tr Vses Soveschaniya Uskoritel Zaryazh Chastits 1968, 2, Moskva VIN1T1 1970, 560-563 (in Russian). 33. GENERAL PHYSICS AND ELECTRONICS 33 465. Metal tips produced by electron bombardment. An apparatus is described to transform the end of a wire (tungsten in the vacuum into a fine tip by electron bombardment. Curvature radii at the tip apex down to l0 BX are obtained. The tips are controlled by (I) an optical microscope (2) an electron microscope and (3) a field electron microscope. The interpretation of the process of tip sharpening is based on evaporation, surface diffusion and surface energy in the presence of a temperature gradient caused by the electron bombardment. It seems to use the method for the production and the regeneration of point cathodes in electron microscopes as well as a field emitter in field emission microscopes. M Drechsler and J P Prulhiere, Vacuum, 20 (11), Nov 1970, 491494
(in English and French). 33 466. Quadrupole mass filter: circular rods and peak shapes. (USA) A frequently observed characteristic of quadrupole mass filters is the appearance, at high resolution, of a separate "precursor" peak on the low mass side of each mass peak. Such false precursor peaks are shown to result from the use of round rods (rather than hyperbolic rods) which are common in all commercial instruments. Round rods introduce sixth- and tenth-order terms to the ideal quadrupole field. The amount of sixth-order distortion introduced by the use of circular rods is computed. The equipotential line produced at the surface of a round rod can be represented quite well by a quadrupole field with a large amount of sixth-order distortion. This distortion introduces a resonance line in the Mathieu stability diagram which at high resolution is near the edge of the peak on the low mass side. The resonance line can distort the peak to produce an apparent precursor peak. P H Dawson and N R Whetten, J Vac Sci Technol, 7 (3), May/June 1970, 440441. 33 467. Electron microscopic investigation of the oxide layer formed on the surface of chemically treated germanium single crystals. Effects of some corrosive agents on morphology of the surface oxide layer. (Hungary) The effect of various etching agents containing nitric acid or hydrogen peroxide as oxidant on the morphological and structural parameters