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Time characteristics of vacuum breakdown
Classified
abstracts
843-854
processes take part in vacuum breakdown initiation at small electrode distances. T A Poshekhonova et al, Radiotekh Elekfron, 15, (IO) Ott 2156-Z 162 (in Russian).
inter1970,
31 843. Packing density and optical properties of electron beam tube screens. (USSR) A method of determining the thickness, average size and packing density of phosphor grains in electron beam tube screens, is presented. It is based on measurement of optical properties of the screen. Ya 0 Dovgiy et al, Izv VUZ Fiz, No IO, 1970, 98-103 (in Russim). 31 844. Time characteristics of vacuum breakdown. (USSR) Sufficient statistical data is gathered to evaluate the time and the nature of vacuum breakdown under conditions of steady and pulsed voltages. The experimental vacuum-gap device was evacuated to pressure of 5x IO-” torr by diffusion pump equipped with a liquid nitrogen trap. The pulse generator produces rectangular pulses of amplitude 0.5 to 45 kV with 30 nsec duration and leading edge of 2 nsec. Measurements were performed for different electrode materials and electrode treatments. The number of pulses was 5000. On the basis of measurements, some hypotheses are presented on the relation between the breakdown time characteristics and the explosion-like mechanism of breakdown development. The breakdown time at pulsed voltages is composed of the time constant of the circuit, time lag of breakdown and proper time of conduction formation. The time lag of breakdown is characterized by the time interval, in which heating of the electrodes by pre-breakdown currents take place up to the stage, in which explosion of electrode material may occur. The time lag decreases with enhancement of the pre-breakdown currents, ie with increasing field intensity. The vacuum-gap conduction formation time is determined by the removal velocity of the exploded material. A A Avdienko and A V Kiselev, Zh Tekh Fiz, 40 (9), Sept 1970, 19351941 (in Russion). 31 845. Microdischarges of fast micron particles. (USSR) The intensities of light flashes generated on micron charged particle impact on conducting surface in vacuum at 2 x IO-” torr are measured as function of velocity, charge, and size of particles. It is found that at velocities up to 1 km/set the light flash is generated as a result of electrical discharge between the particle and the surface, while at higher velocities the discharge arises from thermal effects connected with the impact. E P Martynov, Zh Tekh Fiz, 40 (9), Sept 1970, 1966-l 968 (in Russian). 31 846. Manufacturing technique for resonance lamps and absorption cells with optical pumping by He4 and He” atoms. (USSR) A new simple technique for the manufacture of resonance lamps and absorption cells with optical pumping by helium atoms is described. This technique is based on the introduction into the cells and lamps of a continuously acting and very efficient getter which chemically binds and removes all impurities which are contained in the helium or which may be released from the walls during operation with gas discharge. Metallic rubidium or caesium are used as such getters. The atomic vapours of these elements are chemically very active and immediately react with practically all possible impurities, continuously maintaining the required purity of helium. Application of this technique eliminated the steps of helium purification at the filling stage and gas discharge cleaning of the walls before final filling. 11 is shown that application of this technique in the manufacture of cells and lamps enables impurity contents in helium below 10eJ torr to be maintained, as well as providing a high level of helium atom optical pumping in the lamps and cells. R A Zhitnikov and I A Kravtsov, Zh Tekh Fiz, 40 (lo), Ott 1970, 2131-2173 (in Russian). 31 847. Attaining ultrahigh vacuum in sealed vacuum tubes by means of oil-free pumps with low pumping speed. (Germany) An ultrahigh vacuum plant with small sputter-ion pumps having pumping speeds of 1-2 litre/sec is described. A mechanical pump evacuates the system to 10-l torr. Backstreaming of oil vapours from the mechanical pump is made impossible by a gas velocity of 10” cm/set in the pumping direction. Intermediate evacuation to the starting pressure of the sputter-ion pump is by a simple glass sorption pump filled with zeolite. The first sputter-ion pump is 364
used to evacuate the system to high vacuum and during degassing by baking at up to 420 C. The sputter ion pumps contain a Hall diode arrangement in a glass envelope. A liquid nitrogen trap is used in the first period of degassing for removal of condensible vapours. With the aid of the second sputter-ion pump, which is degassed in the furnace together with the vacuum tube, an ultimate pressure lower than IO-” torr is reached in the ultrahigh vacuum section. Bakeable permanent magnets are used in the sputter-ion pumps. This evacuation procedure was successfully employed in the manufacture of vacuum tubes with photocathodes. S Fleischer et al, Eupev Tech Phys, 18 ( I - 2), 1970, 69 74 (i/i Ger~xru). 31 848. Semi-automatic machine for vacuum treatment of vidiconq with finished photolayers. (USSR) Construction and performance of a semi-automatic machine I’OI evacuation of vidicons, with finished photolayers, are described. V M Mikhaylov and Ts B Cheranovskiy, Elektrm Tckh EIektronlmh Fofoelektron Prih, I, 1970. 62-64 (in Ru.wiml). 31 849. Vibrational noise of vacuum tubes under a complex form of acceleration. (USSR) The level of vibrational noise of vacuum tubes under a complex form of acceleration is calculated. A P Vesnin, Elektron Tekh Priermo Usilit Ltrmp.v, I, 1970. 98 I IO (in Russian). 31 850. Device for contact potential difference measurement between electrodes of directly heated vacuum tubes, using the phase harmonic method. (USSR) Construction of a device for contact potential difTerence measurement between the grid and the cathode of vacuum tubes with directly heated cathodes using the phase harmonic method is described. Its advantages include high resolution and sensitivity. V 1 Ovcharenko et al, Elektron Tekh Priemno U.dlit Lrmp.v. 1, 1970, 127 129 (in Russian). 31 851. On reliability tests of long-life and reliable receiving tubes. (USSR) Selection of vacuum tubes for reliability tests and the method fol life estimation on the basis of sample examinations are presented. E I Zhevakin, Elektron Tekh Priemw Usilit Lumper, I, 1970, 78 ~86 (in Russian).
31 852. Method of determining the evaporation from active layers on the electrodes of electro-vacuum devices. (USSR) A method of determination of evaporated layers of active material from the cathode on the electrodes of electro-vacuum devices i\ presented. It is based on measurement of the reverse currents from the electrodes immediately after the active layer is heated by bombardment with electrons from the cathode. 0 M Nilov and S Sh Rutshteyn, Elektron Tekh Priet,rno l/xi/it Ltr/~t>.~~, I, 1970, 125-127 (in Russian). 31 853. Chamber evacuation of electron devices with glass envelooe. (USSR) Laboratory technique of stem-less pumping of electro-vacuum devices. with glass envelopes, is presented. In this technique. the sealing is interchanged with the evacuation process in a high vacuum chamber with expanded parts of the device. The system of the device, mounted on the base, and the envelope are separately degassed in the vacuum chamber. After thermal treatment, the envelope is sealed to the base by diffusion welding in vacuum. The technique wab tested in receiver tube manufacture and it eliminated oxidation of metallic parts of the device systems, reduced the evacuation and hermetiration times, and enabled automation of these processes. R E Kashlatyy et al, Elektron Tekh Priemno Usilit Lamp,~~, I, 1970. 18-Z I (in Russian). 31 854. Kinetics of alkaline earth carbonate conversion on different cathode cores in the evacuation of receiver tubes on semi-automatic machines. (USSR) The conversion rates of alkaline earth carbonates on passive cathode cores and cores with tungsten and magnesium additives are investigated during evacuation of receiver tubes. For measurement of kinetic curves of carbonate conversion, BaCO, labelled with C” isotope was used. It is experimentally found that the conversion rate
abstracts
843-854
processes take part in vacuum breakdown initiation at small electrode distances. T A Poshekhonova et al, Radiotekh Elekfron, 15, (IO) Ott 2156-Z 162 (in Russian).
inter1970,
31 843. Packing density and optical properties of electron beam tube screens. (USSR) A method of determining the thickness, average size and packing density of phosphor grains in electron beam tube screens, is presented. It is based on measurement of optical properties of the screen. Ya 0 Dovgiy et al, Izv VUZ Fiz, No IO, 1970, 98-103 (in Russim). 31 844. Time characteristics of vacuum breakdown. (USSR) Sufficient statistical data is gathered to evaluate the time and the nature of vacuum breakdown under conditions of steady and pulsed voltages. The experimental vacuum-gap device was evacuated to pressure of 5x IO-” torr by diffusion pump equipped with a liquid nitrogen trap. The pulse generator produces rectangular pulses of amplitude 0.5 to 45 kV with 30 nsec duration and leading edge of 2 nsec. Measurements were performed for different electrode materials and electrode treatments. The number of pulses was 5000. On the basis of measurements, some hypotheses are presented on the relation between the breakdown time characteristics and the explosion-like mechanism of breakdown development. The breakdown time at pulsed voltages is composed of the time constant of the circuit, time lag of breakdown and proper time of conduction formation. The time lag of breakdown is characterized by the time interval, in which heating of the electrodes by pre-breakdown currents take place up to the stage, in which explosion of electrode material may occur. The time lag decreases with enhancement of the pre-breakdown currents, ie with increasing field intensity. The vacuum-gap conduction formation time is determined by the removal velocity of the exploded material. A A Avdienko and A V Kiselev, Zh Tekh Fiz, 40 (9), Sept 1970, 19351941 (in Russion). 31 845. Microdischarges of fast micron particles. (USSR) The intensities of light flashes generated on micron charged particle impact on conducting surface in vacuum at 2 x IO-” torr are measured as function of velocity, charge, and size of particles. It is found that at velocities up to 1 km/set the light flash is generated as a result of electrical discharge between the particle and the surface, while at higher velocities the discharge arises from thermal effects connected with the impact. E P Martynov, Zh Tekh Fiz, 40 (9), Sept 1970, 1966-l 968 (in Russian). 31 846. Manufacturing technique for resonance lamps and absorption cells with optical pumping by He4 and He” atoms. (USSR) A new simple technique for the manufacture of resonance lamps and absorption cells with optical pumping by helium atoms is described. This technique is based on the introduction into the cells and lamps of a continuously acting and very efficient getter which chemically binds and removes all impurities which are contained in the helium or which may be released from the walls during operation with gas discharge. Metallic rubidium or caesium are used as such getters. The atomic vapours of these elements are chemically very active and immediately react with practically all possible impurities, continuously maintaining the required purity of helium. Application of this technique eliminated the steps of helium purification at the filling stage and gas discharge cleaning of the walls before final filling. 11 is shown that application of this technique in the manufacture of cells and lamps enables impurity contents in helium below 10eJ torr to be maintained, as well as providing a high level of helium atom optical pumping in the lamps and cells. R A Zhitnikov and I A Kravtsov, Zh Tekh Fiz, 40 (lo), Ott 1970, 2131-2173 (in Russian). 31 847. Attaining ultrahigh vacuum in sealed vacuum tubes by means of oil-free pumps with low pumping speed. (Germany) An ultrahigh vacuum plant with small sputter-ion pumps having pumping speeds of 1-2 litre/sec is described. A mechanical pump evacuates the system to 10-l torr. Backstreaming of oil vapours from the mechanical pump is made impossible by a gas velocity of 10” cm/set in the pumping direction. Intermediate evacuation to the starting pressure of the sputter-ion pump is by a simple glass sorption pump filled with zeolite. The first sputter-ion pump is 364
used to evacuate the system to high vacuum and during degassing by baking at up to 420 C. The sputter ion pumps contain a Hall diode arrangement in a glass envelope. A liquid nitrogen trap is used in the first period of degassing for removal of condensible vapours. With the aid of the second sputter-ion pump, which is degassed in the furnace together with the vacuum tube, an ultimate pressure lower than IO-” torr is reached in the ultrahigh vacuum section. Bakeable permanent magnets are used in the sputter-ion pumps. This evacuation procedure was successfully employed in the manufacture of vacuum tubes with photocathodes. S Fleischer et al, Eupev Tech Phys, 18 ( I - 2), 1970, 69 74 (i/i Ger~xru). 31 848. Semi-automatic machine for vacuum treatment of vidiconq with finished photolayers. (USSR) Construction and performance of a semi-automatic machine I’OI evacuation of vidicons, with finished photolayers, are described. V M Mikhaylov and Ts B Cheranovskiy, Elektrm Tckh EIektronlmh Fofoelektron Prih, I, 1970. 62-64 (in Ru.wiml). 31 849. Vibrational noise of vacuum tubes under a complex form of acceleration. (USSR) The level of vibrational noise of vacuum tubes under a complex form of acceleration is calculated. A P Vesnin, Elektron Tekh Priermo Usilit Ltrmp.v, I, 1970. 98 I IO (in Russian). 31 850. Device for contact potential difference measurement between electrodes of directly heated vacuum tubes, using the phase harmonic method. (USSR) Construction of a device for contact potential difTerence measurement between the grid and the cathode of vacuum tubes with directly heated cathodes using the phase harmonic method is described. Its advantages include high resolution and sensitivity. V 1 Ovcharenko et al, Elektron Tekh Priemno U.dlit Lrmp.v. 1, 1970, 127 129 (in Russian). 31 851. On reliability tests of long-life and reliable receiving tubes. (USSR) Selection of vacuum tubes for reliability tests and the method fol life estimation on the basis of sample examinations are presented. E I Zhevakin, Elektron Tekh Priemw Usilit Lumper, I, 1970, 78 ~86 (in Russian).
31 852. Method of determining the evaporation from active layers on the electrodes of electro-vacuum devices. (USSR) A method of determination of evaporated layers of active material from the cathode on the electrodes of electro-vacuum devices i\ presented. It is based on measurement of the reverse currents from the electrodes immediately after the active layer is heated by bombardment with electrons from the cathode. 0 M Nilov and S Sh Rutshteyn, Elektron Tekh Priet,rno l/xi/it Ltr/~t>.~~, I, 1970, 125-127 (in Russian). 31 853. Chamber evacuation of electron devices with glass envelooe. (USSR) Laboratory technique of stem-less pumping of electro-vacuum devices. with glass envelopes, is presented. In this technique. the sealing is interchanged with the evacuation process in a high vacuum chamber with expanded parts of the device. The system of the device, mounted on the base, and the envelope are separately degassed in the vacuum chamber. After thermal treatment, the envelope is sealed to the base by diffusion welding in vacuum. The technique wab tested in receiver tube manufacture and it eliminated oxidation of metallic parts of the device systems, reduced the evacuation and hermetiration times, and enabled automation of these processes. R E Kashlatyy et al, Elektron Tekh Priemno Usilit Lamp,~~, I, 1970. 18-Z I (in Russian). 31 854. Kinetics of alkaline earth carbonate conversion on different cathode cores in the evacuation of receiver tubes on semi-automatic machines. (USSR) The conversion rates of alkaline earth carbonates on passive cathode cores and cores with tungsten and magnesium additives are investigated during evacuation of receiver tubes. For measurement of kinetic curves of carbonate conversion, BaCO, labelled with C” isotope was used. It is experimentally found that the conversion rate