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Measurement of vacuum in image, orthicon tubes
Classified a b s t r a c t s 442--451 and Lothrop and by Redhead are interpreted in terms of ionization by electron impact at the grid surface. A comparison of such effects in various gauges is given. Other effects on pressure measurement due to electron bombardment of the grid are described. W C Schuemann et al, Trans 10 A V S Nat Vac Symp, MacMillan & Co, 1963, p 223. 22 442. A rotating sphere absolute vacuum gauge. (Great Britain) The torque required to maintain constant angular speed of a magnetically suspended sphere depends only on the ambient air pressure. Its rate of increase with pressure can be calculated by well-established methods of the kinetic theory assuming that the tangential momentum coefficient is unity under the prevailing vacuum conditions. Similarly by measuring the deceleration of the sphere the ruling gas pressure can be deduced if the molecular weight of the gas is known. Comparison with an ionization gauge indicates an absolute accuracy of 3 per cent. (Great Britain) P T Harbour and R G Lord, J Sci Instrum, 42 (2), Feb 1965, 105-108. 22 443. Reverse X-ray currents in Bayard-Alpert ionization gauges. (USA) The soft X-rays generated at the grid of a Bayard-Alpert gauge cause photo electrons to be emitted from walls surrounding the gauge. If the ion collector is operated at a potential near that of these walls, some of the photo electrons will be energetically capable of reaching the collector. Some small fraction of those passing through the grid will actually arrive at the collector, thereby giving rise to a component of residual current opposite in direction to the normal X-ray current and producing a net reduction in the X-ray limit of the gauge. With appropriate combinations of gauge geometry and operating voltages, the net X-ray limit can be reduced to zero or can even become negative. W H Hayward et al, Trans 10 A VS Nat Vac Symp, MacMillan & Co, 1963, p 228. 22 444. A cold cathode discharge gauge fur ultra-high vacuum use. (USA) A cold cathode gauge which utilizes the Penning type discharge has been constructed which has been shown to be capable of measuring pressure between 10 3 and 10 -14 torr. This gauge has a sensitivity near 1 a m p / t o m A trigger filament enables instant starting even at pressures below 10 -l° torr. This gauge provides several advantages over an ionization gauge for measuring pressure. The advantages are: (1) increases sensitivity; (2) no hot filaments to interact with active gases during normal operation, the trigger filament is heated only during starting; (3) ability to measure pressure below the X-ray limit of most ionization gauges; (4) much less outgassing during operations; (5) does not interact with active gases to produce impurities. A cold cathode discharge gauge has also been constructed with an electron multiplier which may be capable of measuring much lower pressures. J R Young and F P Hession, Trans 10 A V S Nat Vac Syrup, MacMillan & Co, 1963, p 234. 22 445. High sensitivity pressure probes for use in the millitorr region
(USA) A constant temperature thermocouple vacuum gauge has been designed for use in probes in a low-density wind tunnel. It has a gauge volume of less than 0.1 ml (0.04 ml in one case), a usable sensitivity of less than 10 5 torr at 10 3 tort (limited by gauge-head ambient temperature) and is of modest cost. During one month's use no drift in the calibration constant of the gauge could be detected. These probes have been used to investigate velocity slip, temperature jump a n d accommodation coefficients in air flowing at a Mach number of 0.5. S A Gordon, Trans 10 A V S Nat Vac Symp, MacMillan & Co, 1963, p 238. 22 446. Measurement of vacuum in image, orthicon tubes. (USA) A method for the vacuum measurement in the image orthicon tube is developed using its secondary electron multiplier section as an ionization gauge. The behaviour of this vacuum gauge is almost the same as that of a conventional ionization gauge though there are some peculiar characteristics due to the effects of secondary electron mission. Under an atmosphere of argon, extremely slow leaks could be detected by measuring the pressure in the
manufactured to other types factors which are examined. H Kobayashi, 1963, p 287.
tube. This leak detection technique is also applicable of tubes which use barium or similar getters. Several affect the residual pressure in image orthicon tubes
Trans 10 A VS Nat Vac Symp, MacMillan & Co,
22 : 21 447. Investigation of air and water vapour pressures in a five and a six stage steam jet ejector. (USA) Water vapour vs. air content has been measured on five and six stages of a steam ejector under load conditions. Interpretation of the action of cold traps in such measurements are presented. Data indicates for a six-stage ejector almost 100 per cent water vapour at no-load, decreasing to a constant (1.6 × 10 -3 torr) partial pressure as an air load is introduced. This partial pressure is independent of total pressure for either five or six stages. Much lower pressures than produced by six-stage ejectors have been obtained by addition of cryogenic or gas-actuated pumping stages. Potential of these methods is discussed. D H Martin and C H Stallings, Trans 10 A V S Nat Vac Syrup, MacMillan & Co, 1963,p 297.
26. Automatic protective and control equipment 26 Vacuum techniques for fabricating integrated cryoelectric computer devices. See abstract number 460. 26 448. A device for the continuous passage of manufactured articles through a vacuum by means of air locks. ( U S S R ) Two systems for the passage of objects into a high vacuum (10 -e torr) and for their subsequent re-entry into the atmosphere after a short sojourn are described. By means of a series of air locks, suitably controlled, the pressure variation in the main chamber during loading and unloading is kept below 10 torr. Up to 300 objects can be tested in this installation per hour. V N Avdeev et al, Dokl A k a d Nauk B S S R , (11), 1964, 699-701, (in Russian).
27. Leak detectors and leak detection 27 449. Detection of leak sand mercury vapour in vacuum systems by analysing light from discharges. (USA) At --5 × 10 6 torr total pressure, < 5 × 10 9 torr partial pressure of Hg is detected in terms of the intensity of 2537/~ light issuing from a PIG discharge. For leak detection, two methods using the same discharge cell geometry are used. Between --0.1 and < 1 × 10 s torr, characteristic spectra from gases (helium, etc) is analyzed by gratings or prisms or interference filters and monitored by photomultiplier tube detectors. Between 0.5 and l0 torr, established against air leaks, no magnetic field is used and the change in total visible light from the discharge cell, picked up by a photo cell, rises sharply when the leaks are probed with He, Ne, or Ar. The onset response of the detector is limited by system volume; and helium clean up is determined by the pumping time constant of the system. N Milleron, Trans 10 A V S Nat Vac Syrup, MacMillan & Co, 1963, p 283.
28. Heating equipment and thermometers 28 : 37 450. A crucibleless vacuum induction melting and casting process for consolidation and purification of reactive metals. (USA) A crucibleless vacuum induction melting and casting technique has been developed to consolidate reactive metals without contamination. Indeed, purification of the melt is effected. There is no reason to believe that the technique cannot be scaled up to the 5-10 size in beryllium using adequate power supplies and coil design. ( U S A ) R F Bunshah and R S Juntz, Trans 6 Vac Metall Conf, American Vacuum Society, 1964, 110-120. 28 : 37 451. Laboratory installation for melting and processing of refractory metal-ceramic materials by electronic beams in vacuum. (USSR)
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(USA) A constant temperature thermocouple vacuum gauge has been designed for use in probes in a low-density wind tunnel. It has a gauge volume of less than 0.1 ml (0.04 ml in one case), a usable sensitivity of less than 10 5 torr at 10 3 tort (limited by gauge-head ambient temperature) and is of modest cost. During one month's use no drift in the calibration constant of the gauge could be detected. These probes have been used to investigate velocity slip, temperature jump a n d accommodation coefficients in air flowing at a Mach number of 0.5. S A Gordon, Trans 10 A V S Nat Vac Symp, MacMillan & Co, 1963, p 238. 22 446. Measurement of vacuum in image, orthicon tubes. (USA) A method for the vacuum measurement in the image orthicon tube is developed using its secondary electron multiplier section as an ionization gauge. The behaviour of this vacuum gauge is almost the same as that of a conventional ionization gauge though there are some peculiar characteristics due to the effects of secondary electron mission. Under an atmosphere of argon, extremely slow leaks could be detected by measuring the pressure in the
manufactured to other types factors which are examined. H Kobayashi, 1963, p 287.
tube. This leak detection technique is also applicable of tubes which use barium or similar getters. Several affect the residual pressure in image orthicon tubes
Trans 10 A VS Nat Vac Symp, MacMillan & Co,
22 : 21 447. Investigation of air and water vapour pressures in a five and a six stage steam jet ejector. (USA) Water vapour vs. air content has been measured on five and six stages of a steam ejector under load conditions. Interpretation of the action of cold traps in such measurements are presented. Data indicates for a six-stage ejector almost 100 per cent water vapour at no-load, decreasing to a constant (1.6 × 10 -3 torr) partial pressure as an air load is introduced. This partial pressure is independent of total pressure for either five or six stages. Much lower pressures than produced by six-stage ejectors have been obtained by addition of cryogenic or gas-actuated pumping stages. Potential of these methods is discussed. D H Martin and C H Stallings, Trans 10 A V S Nat Vac Syrup, MacMillan & Co, 1963,p 297.
26. Automatic protective and control equipment 26 Vacuum techniques for fabricating integrated cryoelectric computer devices. See abstract number 460. 26 448. A device for the continuous passage of manufactured articles through a vacuum by means of air locks. ( U S S R ) Two systems for the passage of objects into a high vacuum (10 -e torr) and for their subsequent re-entry into the atmosphere after a short sojourn are described. By means of a series of air locks, suitably controlled, the pressure variation in the main chamber during loading and unloading is kept below 10 torr. Up to 300 objects can be tested in this installation per hour. V N Avdeev et al, Dokl A k a d Nauk B S S R , (11), 1964, 699-701, (in Russian).
27. Leak detectors and leak detection 27 449. Detection of leak sand mercury vapour in vacuum systems by analysing light from discharges. (USA) At --5 × 10 6 torr total pressure, < 5 × 10 9 torr partial pressure of Hg is detected in terms of the intensity of 2537/~ light issuing from a PIG discharge. For leak detection, two methods using the same discharge cell geometry are used. Between --0.1 and < 1 × 10 s torr, characteristic spectra from gases (helium, etc) is analyzed by gratings or prisms or interference filters and monitored by photomultiplier tube detectors. Between 0.5 and l0 torr, established against air leaks, no magnetic field is used and the change in total visible light from the discharge cell, picked up by a photo cell, rises sharply when the leaks are probed with He, Ne, or Ar. The onset response of the detector is limited by system volume; and helium clean up is determined by the pumping time constant of the system. N Milleron, Trans 10 A V S Nat Vac Syrup, MacMillan & Co, 1963, p 283.
28. Heating equipment and thermometers 28 : 37 450. A crucibleless vacuum induction melting and casting process for consolidation and purification of reactive metals. (USA) A crucibleless vacuum induction melting and casting technique has been developed to consolidate reactive metals without contamination. Indeed, purification of the melt is effected. There is no reason to believe that the technique cannot be scaled up to the 5-10 size in beryllium using adequate power supplies and coil design. ( U S A ) R F Bunshah and R S Juntz, Trans 6 Vac Metall Conf, American Vacuum Society, 1964, 110-120. 28 : 37 451. Laboratory installation for melting and processing of refractory metal-ceramic materials by electronic beams in vacuum. (USSR)
277