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The measurement of the speed of pumps
Classified
abstracts
721-732
18 : 50 721. Stability of a plasma with finite p in ratio of plasma to magnetic energy.
(France)
A necessary stability condition is obtained for a system without magnetic surface, and a sufficient condition for a system with isotropic pressure and without parallel current. These two conditions tend towards the necessary and sufficient condition for very small and very large /3 respectively. From this, the critical /I is evaluated in a magnetic well, showing the importance of the transverse depth. (France) (Author) J Andreoletti, C R Acad-Sci, Paris, 258, May 1964, 5183-5186. 722. Detection of an electron beam in a toroidal plasma. Britain) i
18 (Great
Two methods are described for measuring the energy and flux of an electron beam which is immersed in a high energy plasma in a toroidal magnetic field, when the beam energy is only a few keV. The first method uses an X-ray technique. The electron collision X-ray spectrum from a tungsten target is analysed with scintillation counters. The system is calibrated with a monoenergetic beam. The second method uses a retardation potential analyser. To prevent grid potential breakdown a potential pulse of 2psec duration was applied. This potential was stable in Ijlasma of density up to 1OL4 ions/cc and long enough to cover the electron time of flight (-1 psec). (Great Britain) (Authors) D W Atkinson and J M S Schofield, UKAEA Report CLMR39, Ott 1964.
20. Pumping
systems
20: 11 :21 Properties of high vacunm pumps. See abstract number 727. 20 : 12 723. Avoiding systematic errors in measuring the pumping speed of high vacuum pumps. (Great Britain) Methods are described which allow the determination of the effective speed of high vacuum pumps. Measurements can be made on test domes having the satie diameter as the mouth of the pump. (Authors) (Great Britain) R Bubl and E A Trendelenburg, Vacuum, 15 (5)) May 1965, 231.
II. Vacuum 21. Pumps
apparatus
and pump
and auxiliaries
fluids
21 : 16 Production, technical data and applications of synthetic zeolites (molecular sieves). See abstract number 717. 21 :25 724. An air-cooled diffusion pump and thermoelectrically cooled baffle to reach lO-$ torr. (Great Britain) Air-cooled oil diffusion pumps are well known for use in vacuum systems where the provision of cooling water may be inconvenient, but they have usually been restricted to small sizes and only moderate vacua. In this paper are described the characteristics of an air-cooled pump having the relatively high speed of 600 l./sec. The addition of a thermoelectrically cooled baffle, with an aircooled heat sinnk, produces a compact water-free pumping group capable of reaching 1O-s torr or below using Silicone 705 fluid. New constructional techniques are considered to play a large part in rapidly achieving these low pressures without baking. The influence of a backing diffusion pump on ultimate pressure is also (Authors) discussed. (Great Britain) D J Crawley and J M Miller, Vacuum, 15 (4), April 1965, 183. 725. The measurement of the speed of pumps.
21 (Great Britain)
: 14
It is proposed to specify an “intrinsic” speed of a pump as well as an “intrinsic” conductance of components as obtained when these are connected to a large chamber or between large chambers. It is shown that by separating out an aperture conductance, both for the case of a component and a pump, the reciprocals of conductances and of pump speeds in composite systems are additive in the usual way, provided that the number of aperture conductances have been correctly accounted for. On the other hand Dayton suggested that the pump speed should be specified as measured with a test dome of the same diameter as the pump. In this case, the conductance of a
428
tube of the same diameter as the pump needs to be modified to allow for the beaming effect of the gas into the pump mouth. It is shown that the alternative procedure based on the use of intrinsic speed and conductance is preferable in many ways and gives identical results for the net speed of a composite system, as obtained by the method of Dayton. Finally. it is shown that bv moving the position of a tubulated gauge along a test dome of ihe same-diameter as the pump, a position can be found where the measured pump speed is approximately equivalent to the intrinsic speed. For a test dome of effective length equal to the diameter, the gauge tube should be at a position on the wall, half a diameter away from the pump mouth. (Great Britain) (Author) W Steckelmacher, Vacuum, 15 (5), May 1965,249. 21 :22 726. Orbitron pump of 30-cm diameter. (USA) An orbitron pump of 30-cm diameter was constructed and performance was studied as parameters were varied. The pump arrangement chosen gave pumping speed values of 105 I./set for argon, 4500 l./sec for air, 6000 l./sec for nitrogen, and 9000 l./sec for hydrogen. J C Maliakal et al, J Vat Sci & Tech, 1 (2), Nov-Dee 1964,54. 21 : 11 : 20 727. Properties of high vacuum pumps. (Great Britain) An almost bewildering range of makes and types of pumps is nowadays available for incorporation in high vacuum systems for research and industry. This review article discusses the properties of pumps which are commercially available together with some of the new pumping devices which have been described in the literature. (Great Britain) (Author) T E Lucas, Vacuum, 15 (S), May 1965. 221.
22. Gauges 22 : 21 Orbitron pump of 30-cm diameter. See abstract number 726. 22 728. Float manometer indicates small pressure differences. (USA) R Kumar and N R Kuloor, Chem Engng, 72 (4), Feb 1965, 200. 22 729. A bakeable thermistor vacuum gauge. (USA) A thermistor detector for measuring pressures in the range 1O-4 to 1 torr is described. This gauge operates at constant temperature (.-100°C), has a small volume, and presents an innocuous surface to the vacuum system. This gauge is very stable, maintains its calibrations after a 450°C bakeout, and is suited for use in ultrahigh-vacuum systems. Operating characteristics are described. R W Roberts et al, J Vat Sci & Tech, 1 (2). Nov-Dee 1964,62. 23. Plumbing 23
730. Annular multiple glass-to-metal pressure seals. (Germany) A detailed study is made of the influence of a tubular lead-through placed in the middle of a five-component cylindrical compression seal upon the mechanical stresses within the glass-insulation; potential sealing hazards are discussed when 13-15 per cent chromium steel is used for the metal components. The mechanical stresses in the glass change only about a few per cent if the wall thickness of the tubular lead-through is varied. A number of possibilities are discussed which may avoid the dangerous y + a transition of chromium steels at the Martensite point. F von Gross, Vakuum-Tech, 14 (4)) May, 1965,97. 23 : 30 731. A simple method of realization of reliable electrical contacts
with conducting and semiconducting films. (USSR) A reliable method of attaching leads to films is described. Copper electrodes (0.6 mm x 15-17 mm long) are glued to the substrate (glass or quartz). To these are welded the main leads. Onto the copper leads is sputtered the same material as used in the film. The film is then laid down on the substrate between the leads. The method has been found to give good mechanical and electrical contact over the temperature range -100 to 100°C. (USSR). G D Mokhov, Plant Laboratory, (3). 1965, 389, (in Russian). 23 732. The realization of a practical ceramic-metal bakeable vacuum systems. (USSR)
A study of problems
connected
seal for use in
with the formation
of metal-
abstracts
721-732
18 : 50 721. Stability of a plasma with finite p in ratio of plasma to magnetic energy.
(France)
A necessary stability condition is obtained for a system without magnetic surface, and a sufficient condition for a system with isotropic pressure and without parallel current. These two conditions tend towards the necessary and sufficient condition for very small and very large /3 respectively. From this, the critical /I is evaluated in a magnetic well, showing the importance of the transverse depth. (France) (Author) J Andreoletti, C R Acad-Sci, Paris, 258, May 1964, 5183-5186. 722. Detection of an electron beam in a toroidal plasma. Britain) i
18 (Great
Two methods are described for measuring the energy and flux of an electron beam which is immersed in a high energy plasma in a toroidal magnetic field, when the beam energy is only a few keV. The first method uses an X-ray technique. The electron collision X-ray spectrum from a tungsten target is analysed with scintillation counters. The system is calibrated with a monoenergetic beam. The second method uses a retardation potential analyser. To prevent grid potential breakdown a potential pulse of 2psec duration was applied. This potential was stable in Ijlasma of density up to 1OL4 ions/cc and long enough to cover the electron time of flight (-1 psec). (Great Britain) (Authors) D W Atkinson and J M S Schofield, UKAEA Report CLMR39, Ott 1964.
20. Pumping
systems
20: 11 :21 Properties of high vacunm pumps. See abstract number 727. 20 : 12 723. Avoiding systematic errors in measuring the pumping speed of high vacuum pumps. (Great Britain) Methods are described which allow the determination of the effective speed of high vacuum pumps. Measurements can be made on test domes having the satie diameter as the mouth of the pump. (Authors) (Great Britain) R Bubl and E A Trendelenburg, Vacuum, 15 (5)) May 1965, 231.
II. Vacuum 21. Pumps
apparatus
and pump
and auxiliaries
fluids
21 : 16 Production, technical data and applications of synthetic zeolites (molecular sieves). See abstract number 717. 21 :25 724. An air-cooled diffusion pump and thermoelectrically cooled baffle to reach lO-$ torr. (Great Britain) Air-cooled oil diffusion pumps are well known for use in vacuum systems where the provision of cooling water may be inconvenient, but they have usually been restricted to small sizes and only moderate vacua. In this paper are described the characteristics of an air-cooled pump having the relatively high speed of 600 l./sec. The addition of a thermoelectrically cooled baffle, with an aircooled heat sinnk, produces a compact water-free pumping group capable of reaching 1O-s torr or below using Silicone 705 fluid. New constructional techniques are considered to play a large part in rapidly achieving these low pressures without baking. The influence of a backing diffusion pump on ultimate pressure is also (Authors) discussed. (Great Britain) D J Crawley and J M Miller, Vacuum, 15 (4), April 1965, 183. 725. The measurement of the speed of pumps.
21 (Great Britain)
: 14
It is proposed to specify an “intrinsic” speed of a pump as well as an “intrinsic” conductance of components as obtained when these are connected to a large chamber or between large chambers. It is shown that by separating out an aperture conductance, both for the case of a component and a pump, the reciprocals of conductances and of pump speeds in composite systems are additive in the usual way, provided that the number of aperture conductances have been correctly accounted for. On the other hand Dayton suggested that the pump speed should be specified as measured with a test dome of the same diameter as the pump. In this case, the conductance of a
428
tube of the same diameter as the pump needs to be modified to allow for the beaming effect of the gas into the pump mouth. It is shown that the alternative procedure based on the use of intrinsic speed and conductance is preferable in many ways and gives identical results for the net speed of a composite system, as obtained by the method of Dayton. Finally. it is shown that bv moving the position of a tubulated gauge along a test dome of ihe same-diameter as the pump, a position can be found where the measured pump speed is approximately equivalent to the intrinsic speed. For a test dome of effective length equal to the diameter, the gauge tube should be at a position on the wall, half a diameter away from the pump mouth. (Great Britain) (Author) W Steckelmacher, Vacuum, 15 (5), May 1965,249. 21 :22 726. Orbitron pump of 30-cm diameter. (USA) An orbitron pump of 30-cm diameter was constructed and performance was studied as parameters were varied. The pump arrangement chosen gave pumping speed values of 105 I./set for argon, 4500 l./sec for air, 6000 l./sec for nitrogen, and 9000 l./sec for hydrogen. J C Maliakal et al, J Vat Sci & Tech, 1 (2), Nov-Dee 1964,54. 21 : 11 : 20 727. Properties of high vacuum pumps. (Great Britain) An almost bewildering range of makes and types of pumps is nowadays available for incorporation in high vacuum systems for research and industry. This review article discusses the properties of pumps which are commercially available together with some of the new pumping devices which have been described in the literature. (Great Britain) (Author) T E Lucas, Vacuum, 15 (S), May 1965. 221.
22. Gauges 22 : 21 Orbitron pump of 30-cm diameter. See abstract number 726. 22 728. Float manometer indicates small pressure differences. (USA) R Kumar and N R Kuloor, Chem Engng, 72 (4), Feb 1965, 200. 22 729. A bakeable thermistor vacuum gauge. (USA) A thermistor detector for measuring pressures in the range 1O-4 to 1 torr is described. This gauge operates at constant temperature (.-100°C), has a small volume, and presents an innocuous surface to the vacuum system. This gauge is very stable, maintains its calibrations after a 450°C bakeout, and is suited for use in ultrahigh-vacuum systems. Operating characteristics are described. R W Roberts et al, J Vat Sci & Tech, 1 (2). Nov-Dee 1964,62. 23. Plumbing 23
730. Annular multiple glass-to-metal pressure seals. (Germany) A detailed study is made of the influence of a tubular lead-through placed in the middle of a five-component cylindrical compression seal upon the mechanical stresses within the glass-insulation; potential sealing hazards are discussed when 13-15 per cent chromium steel is used for the metal components. The mechanical stresses in the glass change only about a few per cent if the wall thickness of the tubular lead-through is varied. A number of possibilities are discussed which may avoid the dangerous y + a transition of chromium steels at the Martensite point. F von Gross, Vakuum-Tech, 14 (4)) May, 1965,97. 23 : 30 731. A simple method of realization of reliable electrical contacts
with conducting and semiconducting films. (USSR) A reliable method of attaching leads to films is described. Copper electrodes (0.6 mm x 15-17 mm long) are glued to the substrate (glass or quartz). To these are welded the main leads. Onto the copper leads is sputtered the same material as used in the film. The film is then laid down on the substrate between the leads. The method has been found to give good mechanical and electrical contact over the temperature range -100 to 100°C. (USSR). G D Mokhov, Plant Laboratory, (3). 1965, 389, (in Russian). 23 732. The realization of a practical ceramic-metal bakeable vacuum systems. (USSR)
A study of problems
connected
seal for use in
with the formation
of metal-