- Email: [email protected]
933. The Dewar vessel for liquid helium
Classified abstracts 927--937 by dry air pressure with the aid of a diaphragm gauge operated as a null indicator. The compression gauge is used for absolute pressure measurement of the dry air pressure. The system is evacuated to 10-4 torr before calibration. This method was used for calibration of a resistance gauge in the range of 12 to 10-= torr. Calibration of a thermocouple gauge for water vapour is complicated due to the fact that the sensitivity of the diaphragm gauge is limited in the lower pressure range. To overcome this difficulty, a radioisotope gauge was calibrated for water vapour in the range 10 to 10-2 torr. A relative sensitivity of 0.75 was obtained and it was used also for the range 10-2 to 10-4 torr. The thermocouple gauge was calibrated in this pressure range for water vapour with the aid of the radioisotope gauge. It is found that the calibration curves for water vapour of thermal-conductivity gauges are not similar to those for other gases. This effect is explained by the dependence of the water vapour accommodation coefficient on pressure. On the basis of the experimental results, the dependence of the water vapour accommodation coefficient on pressure was determined for platinum. h I Fursov, Prib Tekh Eksper, No 6, Nov-Dec 1970, 163-165 (in
23 932. Matching of $49-2 glass-to-29NK Kovar alloy seals at low temperatures. (USSR) The variation of stress in wire seals of Kovar-to-glass is investigated in the temperature interval of - 70 to 20°C; V A Blinkov et al, Elektron Tekh Materialy, 9, 1969, 3-11 (in Russian).
Russian).
25 934. Calculation of the helium evaporation rate in nitrogen-free cryostats with high-vacuum insulation. (USSR) An approximative calculation of the liquid helium evaporation rate and temperature of radiation shields in cryostats with high-vacuum insulation is presented, the shields of which are cooled by vapours of evaporating helium. V S Goluhkov and N A Pankratov, lnzh FizZh, 19 (1), 1970, 53-61 (in
22 927. Mechano-electronic transducers (mechanotrons) and their utilization. (USSR) A review of existing types of mechano-electronic transducers is presented. The mechanotron is a vacuum tube, in which the electron current is controlled by mechanical displacement of its electrodes. Principles of operation of different mechanotrons are given. Constructions and parameters of commercially produced rnechanotrons are described. Examples of their utilization in precision control-measuring instruments are given. It is noted that besides mechanotron transducers of displacements and forces, one of the most promising trends in mechanotron applications is the development of highsensitivity mechanotron transducers of pressure--manotrons. Displacement of the mobile anode with respect to the cathode in a manotron depends on pressure difference on both sides of the diaphragm. As the pressure in the manotron is very small (10 -e torr), the displacement of the mobile anode is proportional to the measured pressure. The manotron indication does not depend on the nature of gas or vapour, the pressure of which is measured. Preliminary investigations of characteristics and parameters of some types of manotrons demonstrated the possibility of utilizing these devices for the measurement of pressure in the range from 10-a to 700 torr. G S Berlin, Prib Tekh Eksper, No 6, Nov-Dec 1970, 5-12 (in Russian). 22 928. Control digital manometer. (USSR) Properties of the control digital manometer type KMTs-I.6 are described. It measures pressure in the interval of 0 to 1.6 kg/cm 2 with the measuring accuracy of 0.1 per cent and resolution of 1 x 10-4 kg/cm =. I L Neguritsa, Prib Tekh Eksper, No 5, Sept-Oct 1970, 248 (in
Russian). 22 929. Determination of ratio of D / H on mass spectrometer type MI-1305 with modulated accelerating voltage. (USSR) Simultaneous measurement of the ion beams of H=+ and H D + on a mass spectrometer with a relative error of 4-0.3 per cent is described. The method is based on application of modulated accelerating voltage and it is intended for isotopic analysis of hydrogen. (Hungary) L Matush and I Olmnski, Prib Tekh Eksper, No 5, Sept-Oct 1970, 241242 (in Russian). 22 930. Farvitron signal decay. (Bulgaria) The theoretical calculation of the output signal shape change of a farvitron on switching-off a high-frequency voltage is performed on the basis of the voltage distribution determination in the ion source. The calculated data agree with experiment. Chr Tenchov, Dokl Bulg Akad Nauk, 23 (5), 1970, 499-502. 23. PLUMBING 23 931. Arrangement for motion transfer in vacuum. (USSR) An arrangement for motion transfer in vacuum is described which permits the transfer of objects in vacuum in an arbitrary direction, to a determined distance, with high accuracy. V B Kornilov and I V Ikonitskiy, Prib Tekh Eksper, No 6, Nov-Dec 1970, 212 (in Russian).
25. BAFFLES, TRAPS AND REFRIGERATION EQUIPMENT 25 933. The Dewar vessel for liquid helium. (USSR) It is shown that hermetization of the inter-wall space of Dewar vessels for liquid helium and non-exhaustion of the air from this space, accelerates cooling of the inner body to the liquid nitrogen temperature. To eliminate fast crystallization of air on the surface of the inner body on cooling by liquid helium, an adsorbent is placed in the inter-wall space. The cool-down time dependence of the Dewar vessel on the inter-wall pressure is presented. Ya S Kan, Prib Tekh Eksper, No 6, Nov-Dec 1970, 209-210 (in
Russian).
Russian). 25 935. Cryostat for liquid helium with high-vacuum insulation and without nitrogen. (USSR) A demountable cryostat for liquid helium with high-vacuum insulation is described which does not employ additional cooling of radiation shields by liquid nitrogen. N A Pankratov and V S Goinbkov, Elektron Tekh Kriogen Elektron, 1, 1970, 72-80 (in Russian). 27. LEAK DETECTORS AND LEAK DETECTION 27 936. Methods and instruments for modern leak detection (USSR) It is noted that in conditions of mass production of electrovacuum devices and assemblies, the most stringent task of leak detection is enhancement of productivity and sensitivity of leak monitoring. The task of enhancement of productivity is solved in the construction of an automatic leak-tightness monitor type A K G M with a mass spectrometric head. Increased sensitivity of leak detection is achieved in the leak detector type STI-8 permitting detection of leaks of 10-x4 torr litre/sec by selective pumping using a zeolite pump while the inert test gas is not pumped. All leak monitors allow quantitative determination of the magnitude of the leak when used with the calibrated leak, type Helit 1, which provides a steady helium inleakage into vacuum of 10-6 to 10-8 torr litre/sec. To test forevacuum systems, the halogen leak detector type VAGTI-4 is recommended. The halogen leak detectors are also used for monitoring systems filled with gas containing halides. Calibration of halogen leak detectors is provided for by the halogen leak type Galot 1. V I Karpov and L E Levina, Vakuum Tekh, 2, Kazan 1970, 208-214
(in Russian). 28. HEATING EQUIPMENT AND THERMOMETERS 28 937. Aspects of an ultrahigh vacuum furnace at temperature of 800°C. (USSR) Construction of an ultrahigh vacuum furnace is described. Metallic sealing gaskets are used for its hermetization. The pumping system, including zeolite pumps and electrical-discharge pumps maintains a pressure of 6× 10-s torr in the furnace. To improve the ultimate vacuum of the furnace by an order of magnitude in the cold state, argon treatment of the electrical-discharge pumps is recommended. At temperature of 800°C, the improving effect of the argon treatment is not practically observed. To reduce the time required for obtaining the ultimate pressure, it is advantageous to perform degassing a t temperatures higher than working temperatures. The degassing proceeds faster at higher temperature and the degassing time is reduced. It is shown that it is not possible to use oil pumping systems, (even with special oil-protecting devices such as liquid nitrogen and sorp-
435
23 932. Matching of $49-2 glass-to-29NK Kovar alloy seals at low temperatures. (USSR) The variation of stress in wire seals of Kovar-to-glass is investigated in the temperature interval of - 70 to 20°C; V A Blinkov et al, Elektron Tekh Materialy, 9, 1969, 3-11 (in Russian).
Russian).
25 934. Calculation of the helium evaporation rate in nitrogen-free cryostats with high-vacuum insulation. (USSR) An approximative calculation of the liquid helium evaporation rate and temperature of radiation shields in cryostats with high-vacuum insulation is presented, the shields of which are cooled by vapours of evaporating helium. V S Goluhkov and N A Pankratov, lnzh FizZh, 19 (1), 1970, 53-61 (in
22 927. Mechano-electronic transducers (mechanotrons) and their utilization. (USSR) A review of existing types of mechano-electronic transducers is presented. The mechanotron is a vacuum tube, in which the electron current is controlled by mechanical displacement of its electrodes. Principles of operation of different mechanotrons are given. Constructions and parameters of commercially produced rnechanotrons are described. Examples of their utilization in precision control-measuring instruments are given. It is noted that besides mechanotron transducers of displacements and forces, one of the most promising trends in mechanotron applications is the development of highsensitivity mechanotron transducers of pressure--manotrons. Displacement of the mobile anode with respect to the cathode in a manotron depends on pressure difference on both sides of the diaphragm. As the pressure in the manotron is very small (10 -e torr), the displacement of the mobile anode is proportional to the measured pressure. The manotron indication does not depend on the nature of gas or vapour, the pressure of which is measured. Preliminary investigations of characteristics and parameters of some types of manotrons demonstrated the possibility of utilizing these devices for the measurement of pressure in the range from 10-a to 700 torr. G S Berlin, Prib Tekh Eksper, No 6, Nov-Dec 1970, 5-12 (in Russian). 22 928. Control digital manometer. (USSR) Properties of the control digital manometer type KMTs-I.6 are described. It measures pressure in the interval of 0 to 1.6 kg/cm 2 with the measuring accuracy of 0.1 per cent and resolution of 1 x 10-4 kg/cm =. I L Neguritsa, Prib Tekh Eksper, No 5, Sept-Oct 1970, 248 (in
Russian). 22 929. Determination of ratio of D / H on mass spectrometer type MI-1305 with modulated accelerating voltage. (USSR) Simultaneous measurement of the ion beams of H=+ and H D + on a mass spectrometer with a relative error of 4-0.3 per cent is described. The method is based on application of modulated accelerating voltage and it is intended for isotopic analysis of hydrogen. (Hungary) L Matush and I Olmnski, Prib Tekh Eksper, No 5, Sept-Oct 1970, 241242 (in Russian). 22 930. Farvitron signal decay. (Bulgaria) The theoretical calculation of the output signal shape change of a farvitron on switching-off a high-frequency voltage is performed on the basis of the voltage distribution determination in the ion source. The calculated data agree with experiment. Chr Tenchov, Dokl Bulg Akad Nauk, 23 (5), 1970, 499-502. 23. PLUMBING 23 931. Arrangement for motion transfer in vacuum. (USSR) An arrangement for motion transfer in vacuum is described which permits the transfer of objects in vacuum in an arbitrary direction, to a determined distance, with high accuracy. V B Kornilov and I V Ikonitskiy, Prib Tekh Eksper, No 6, Nov-Dec 1970, 212 (in Russian).
25. BAFFLES, TRAPS AND REFRIGERATION EQUIPMENT 25 933. The Dewar vessel for liquid helium. (USSR) It is shown that hermetization of the inter-wall space of Dewar vessels for liquid helium and non-exhaustion of the air from this space, accelerates cooling of the inner body to the liquid nitrogen temperature. To eliminate fast crystallization of air on the surface of the inner body on cooling by liquid helium, an adsorbent is placed in the inter-wall space. The cool-down time dependence of the Dewar vessel on the inter-wall pressure is presented. Ya S Kan, Prib Tekh Eksper, No 6, Nov-Dec 1970, 209-210 (in
Russian).
Russian). 25 935. Cryostat for liquid helium with high-vacuum insulation and without nitrogen. (USSR) A demountable cryostat for liquid helium with high-vacuum insulation is described which does not employ additional cooling of radiation shields by liquid nitrogen. N A Pankratov and V S Goinbkov, Elektron Tekh Kriogen Elektron, 1, 1970, 72-80 (in Russian). 27. LEAK DETECTORS AND LEAK DETECTION 27 936. Methods and instruments for modern leak detection (USSR) It is noted that in conditions of mass production of electrovacuum devices and assemblies, the most stringent task of leak detection is enhancement of productivity and sensitivity of leak monitoring. The task of enhancement of productivity is solved in the construction of an automatic leak-tightness monitor type A K G M with a mass spectrometric head. Increased sensitivity of leak detection is achieved in the leak detector type STI-8 permitting detection of leaks of 10-x4 torr litre/sec by selective pumping using a zeolite pump while the inert test gas is not pumped. All leak monitors allow quantitative determination of the magnitude of the leak when used with the calibrated leak, type Helit 1, which provides a steady helium inleakage into vacuum of 10-6 to 10-8 torr litre/sec. To test forevacuum systems, the halogen leak detector type VAGTI-4 is recommended. The halogen leak detectors are also used for monitoring systems filled with gas containing halides. Calibration of halogen leak detectors is provided for by the halogen leak type Galot 1. V I Karpov and L E Levina, Vakuum Tekh, 2, Kazan 1970, 208-214
(in Russian). 28. HEATING EQUIPMENT AND THERMOMETERS 28 937. Aspects of an ultrahigh vacuum furnace at temperature of 800°C. (USSR) Construction of an ultrahigh vacuum furnace is described. Metallic sealing gaskets are used for its hermetization. The pumping system, including zeolite pumps and electrical-discharge pumps maintains a pressure of 6× 10-s torr in the furnace. To improve the ultimate vacuum of the furnace by an order of magnitude in the cold state, argon treatment of the electrical-discharge pumps is recommended. At temperature of 800°C, the improving effect of the argon treatment is not practically observed. To reduce the time required for obtaining the ultimate pressure, it is advantageous to perform degassing a t temperatures higher than working temperatures. The degassing proceeds faster at higher temperature and the degassing time is reduced. It is shown that it is not possible to use oil pumping systems, (even with special oil-protecting devices such as liquid nitrogen and sorp-
435