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1808. Shock tube TOF mass spectrometer appratus with cryosorption pumping
Classified
abstracts
1807-1816
the density of the molecules flowing back to the sample by means of an ionization gauge, the following sticking coefficients were determined: nitrogen 0.67 at 20°K and 0.65 at 4.2”K, argon 0.63 at 20°K and 0.67 at 4.2”K. air 0.67 at 20°K and 0.63 at 4.2”K and hvdroeen 0.1 at 4.2”K. All ialues were measured at the gas temperatuie of-300°K and they do not depend on the pressure in the range of 1 x lo-’ to 7 x 1O-5 torr. The chamber residual atmosphere pressure during measurements was better than 5 x 10-O torr. The measuring error does not exceed f5 per cent. N N Bagrov et al, Zh Tekh Fiz, 37 (6), June 1967, 1105-1111 (in Russian). 21 : 32 1807. Liquid helium cryopumps for a large plasma research machine. (USA) The liquid helium cryopumps discussed here are designed to meet specific requirements for hydrogen pumping in the lo-** torr range. They are designed to have about a 2000 litres/sec pumping speed. The design meets configuration and space requirements, and also has the required pumping surface. All-stainless steel construction is used to avoid magnetic coupling. Complicated mechanical supports are used to minimize the heat loss. In one pump a physical property of liquid helium (low viscosity) is utilized to solve the configuration problem. A mode1 of such a pump was made to study this phenomenon and the test results of the model are presented. B S Denhoy, Rep UCRL-70024, 1966 (California &iv, Livermore, Lawrence
Radiation
Lab).
21 : 33 1808. Shock tube TOF mass spectrometer apparatus with cryosorption pumping. (USA) To remove the sampled gas from the ion source of a time-of-flight mass spectrometer, pumping speeds of the order of lo5 litre/sec at 1O-s torr were necessary. A cryosorption pump was built for this purpose employing a freshly evaporated molybdenum film at liquid nitrogen temperature. The apparatus is described and its performance is discussed. P R Ryason, Rev Sci In&rum, 38 (5), 1967 607-611. 21 1809. Cryosorption apparatus. (USA) A heat exchanger within a gas-tight casing consists of one refrigerant conduit, longitudinally coextensive with the walls, and an inlet and outlet at either end. A number of extended surface solid fin members are spaced parallel to each other along the major portion of the conduit exterior surface. They are fixed, and extend normal and outward from the exterior surface with the outer edges spaced from the inner surface of the casing. A screen encloses the fin member outer surfaces and is spaced inward from and parallel to the casing wall forming an annular space, containing a bed of adsorbent material. Hence the fin members are completely surrounded by this material. The outer periphery is directly exposed to the annular space. The gas inlet is in gaseous communication with the adsorbent bed and annular space. Union Carbide COIQ, US Patent 3,335,550, Oficial Gaz US Patent Ofice, 841 (3), 15th Aug 1967, 730. 21 1810. Cryopump.
(Great Britain) This consists of a vessel containing cryogenic fluid at a desired temperature and subsidiary vessel communicating directly for replenishing. The outer surface of the first vessel is in good thermal contact with the gas within a system to be pumped and gas moleculps condense onto the surface. Liquid from the subsidiary vessel to the first vessel can either be pumped or valved by a sensitising means at a pre-determined level only when the liquid is at the desired temperature. (Author) UKAEA, Brit Patent 1,075,316, Patent Abstr, 7 (31) part B. 4th Au,? 1967, 2.
21 1812. Vacuum adsorption pump. (Germany) The pump vessel comprises two concentric cylindrical containers communicating at their lower ends and having pipe unions at their upper ends. Both containers are double walled. The heating and cooling units are located between the inner wall of the outer container and the outer wall of the inner container. The inner wall of the inner container is gas permeable. The adsorptive material is contained between the double walls of each container and in the communicating space at the bottom. (Author) General Electric Co, German Patent purt B, 9th Aug 1967, 2.
1,243,324,
Patent
Abstr,
7 (31)
21 1813. Sorption vacuum pump. (Germany) This comprises a hermetically-sealed casing having side and end walls and an inlet aperture and containing gas absorbent material which is cooled by heat conducting means consisting of a plurality of elongated U-shaped tin members arranged radially within the casing and which conduct heat to the casing. (Author) Varian Associates, German part B, 9th Aug 1967, 2.
Patent
1,243,325,
Patent
Abstr,
7 (31) 21
1814. Multistage
vacuum pump.
(Germany) Suitable for oil free operation, the pump has the high vacuum stage in the centre of the common housing, with additional vacuum stages on either side, followed by any pre-vacuum stages still further towards the outside. The drive shafts are supported only in the outermost housing walls, the internal partitions being sealed against the shafts by non-contacting labyrinth gaps. E Leybold’s Nachfolger, German Patent 1,243,816, Patent Abstr, 7 (32) part B, 16th Aug 1967, 2.
22. GAUGES 22 1815. Ionization gauges with reduced electronic desorption effects. (Poland) The design of an improved modulated Bayard-Alpert gauge with reduced desorption of ions from the anode surface, caused by electron bombardment, is described. Two identical grid-shaped anodes connected to different voltages are arranged as in usual B-A gauge but each two adjacent windings are of different anode systems. Typical voltages are: cathode 70 V, first anode 140 V, second anode 280 V and collector zero V. With this arrangement, 90 per cent of the electrons fall to the windings at higher potential and ions desorbed from the winding are accelerated by the voltage difference between adjacent windings tangentially to the anode shape and slow ions are captured by the winding at lower potential. To avoid X-ray effect a Redhead modulator is used. The effect of reducing the electron desorption is more significant with a collector of diameter 0.5 mm than for thinner ones. The gauge sensitivity is about 2 x 10ea A/torr and the background current is reduced, compared to conventional modulated B-A gauges, by 1.5 x 1Om12 A at 1O-l0 torr. The gauge was also compared with the older Groszkowski’s design of Fayard-Alpert gauge with outer collector (see abstract No. 321/1967) and it is shown that the gauge with the outer collector is free of the X-ray as well as of ele&o&, desorption effects. J Groszkowski. Bull Acad Polon Sci St? Sri Tech. 15 (44‘).1967. (in English). 1816. On some possibilities of improving the sensitivity of mass spectrometer measurements. (USSR)
22 and accuracy
(Great Britain) This pump of the oil sealed radial vane type has greater efficiency and larger throughput by effective degassing of the oil. Starting after being idle under vacuum and when the stages are filled with oil, is made easier and there is more effective sealing of stages and lubrication of moving parts. The pumping capacity is increased without undue increase in the pump size. -(A&h&) Cenco Instr Corp, Brit Patent 1,075,34O,Patent Abstr, 7 (31) part B,
For evaluation of very small ion currents (below 10-l’ A) in magnetic mass spectrometers, the following method is described: the ion accelerating voltage is modulated by sawtooth voltage with peak-topeak amplitude corresponding to a narrow band of mass numbers (eg 198 to 201) and the signal from the mass spectrometer receiving amplifier is converted into phase-modulated pulses and demodulated. ln this way, very high accuracy in resolving isotopes was obtained, since with suitable time-base speed, ion current variations do not influence the mass peak recognition. As an example, the mass spectrum of Hg isotopes measured by MI-1305 mass spectrometer with total ion current of 10-l’ A is given. P I Chalov and U Mamyrov, Pribory Tekh Eksper, 12 (3), May-June
4th Aug 1967, 2.
1967, 123-125
‘1
1811. Rotary vacuum pump.
(in Russian). 619
abstracts
1807-1816
the density of the molecules flowing back to the sample by means of an ionization gauge, the following sticking coefficients were determined: nitrogen 0.67 at 20°K and 0.65 at 4.2”K, argon 0.63 at 20°K and 0.67 at 4.2”K. air 0.67 at 20°K and 0.63 at 4.2”K and hvdroeen 0.1 at 4.2”K. All ialues were measured at the gas temperatuie of-300°K and they do not depend on the pressure in the range of 1 x lo-’ to 7 x 1O-5 torr. The chamber residual atmosphere pressure during measurements was better than 5 x 10-O torr. The measuring error does not exceed f5 per cent. N N Bagrov et al, Zh Tekh Fiz, 37 (6), June 1967, 1105-1111 (in Russian). 21 : 32 1807. Liquid helium cryopumps for a large plasma research machine. (USA) The liquid helium cryopumps discussed here are designed to meet specific requirements for hydrogen pumping in the lo-** torr range. They are designed to have about a 2000 litres/sec pumping speed. The design meets configuration and space requirements, and also has the required pumping surface. All-stainless steel construction is used to avoid magnetic coupling. Complicated mechanical supports are used to minimize the heat loss. In one pump a physical property of liquid helium (low viscosity) is utilized to solve the configuration problem. A mode1 of such a pump was made to study this phenomenon and the test results of the model are presented. B S Denhoy, Rep UCRL-70024, 1966 (California &iv, Livermore, Lawrence
Radiation
Lab).
21 : 33 1808. Shock tube TOF mass spectrometer apparatus with cryosorption pumping. (USA) To remove the sampled gas from the ion source of a time-of-flight mass spectrometer, pumping speeds of the order of lo5 litre/sec at 1O-s torr were necessary. A cryosorption pump was built for this purpose employing a freshly evaporated molybdenum film at liquid nitrogen temperature. The apparatus is described and its performance is discussed. P R Ryason, Rev Sci In&rum, 38 (5), 1967 607-611. 21 1809. Cryosorption apparatus. (USA) A heat exchanger within a gas-tight casing consists of one refrigerant conduit, longitudinally coextensive with the walls, and an inlet and outlet at either end. A number of extended surface solid fin members are spaced parallel to each other along the major portion of the conduit exterior surface. They are fixed, and extend normal and outward from the exterior surface with the outer edges spaced from the inner surface of the casing. A screen encloses the fin member outer surfaces and is spaced inward from and parallel to the casing wall forming an annular space, containing a bed of adsorbent material. Hence the fin members are completely surrounded by this material. The outer periphery is directly exposed to the annular space. The gas inlet is in gaseous communication with the adsorbent bed and annular space. Union Carbide COIQ, US Patent 3,335,550, Oficial Gaz US Patent Ofice, 841 (3), 15th Aug 1967, 730. 21 1810. Cryopump.
(Great Britain) This consists of a vessel containing cryogenic fluid at a desired temperature and subsidiary vessel communicating directly for replenishing. The outer surface of the first vessel is in good thermal contact with the gas within a system to be pumped and gas moleculps condense onto the surface. Liquid from the subsidiary vessel to the first vessel can either be pumped or valved by a sensitising means at a pre-determined level only when the liquid is at the desired temperature. (Author) UKAEA, Brit Patent 1,075,316, Patent Abstr, 7 (31) part B. 4th Au,? 1967, 2.
21 1812. Vacuum adsorption pump. (Germany) The pump vessel comprises two concentric cylindrical containers communicating at their lower ends and having pipe unions at their upper ends. Both containers are double walled. The heating and cooling units are located between the inner wall of the outer container and the outer wall of the inner container. The inner wall of the inner container is gas permeable. The adsorptive material is contained between the double walls of each container and in the communicating space at the bottom. (Author) General Electric Co, German Patent purt B, 9th Aug 1967, 2.
1,243,324,
Patent
Abstr,
7 (31)
21 1813. Sorption vacuum pump. (Germany) This comprises a hermetically-sealed casing having side and end walls and an inlet aperture and containing gas absorbent material which is cooled by heat conducting means consisting of a plurality of elongated U-shaped tin members arranged radially within the casing and which conduct heat to the casing. (Author) Varian Associates, German part B, 9th Aug 1967, 2.
Patent
1,243,325,
Patent
Abstr,
7 (31) 21
1814. Multistage
vacuum pump.
(Germany) Suitable for oil free operation, the pump has the high vacuum stage in the centre of the common housing, with additional vacuum stages on either side, followed by any pre-vacuum stages still further towards the outside. The drive shafts are supported only in the outermost housing walls, the internal partitions being sealed against the shafts by non-contacting labyrinth gaps. E Leybold’s Nachfolger, German Patent 1,243,816, Patent Abstr, 7 (32) part B, 16th Aug 1967, 2.
22. GAUGES 22 1815. Ionization gauges with reduced electronic desorption effects. (Poland) The design of an improved modulated Bayard-Alpert gauge with reduced desorption of ions from the anode surface, caused by electron bombardment, is described. Two identical grid-shaped anodes connected to different voltages are arranged as in usual B-A gauge but each two adjacent windings are of different anode systems. Typical voltages are: cathode 70 V, first anode 140 V, second anode 280 V and collector zero V. With this arrangement, 90 per cent of the electrons fall to the windings at higher potential and ions desorbed from the winding are accelerated by the voltage difference between adjacent windings tangentially to the anode shape and slow ions are captured by the winding at lower potential. To avoid X-ray effect a Redhead modulator is used. The effect of reducing the electron desorption is more significant with a collector of diameter 0.5 mm than for thinner ones. The gauge sensitivity is about 2 x 10ea A/torr and the background current is reduced, compared to conventional modulated B-A gauges, by 1.5 x 1Om12 A at 1O-l0 torr. The gauge was also compared with the older Groszkowski’s design of Fayard-Alpert gauge with outer collector (see abstract No. 321/1967) and it is shown that the gauge with the outer collector is free of the X-ray as well as of ele&o&, desorption effects. J Groszkowski. Bull Acad Polon Sci St? Sri Tech. 15 (44‘).1967. (in English). 1816. On some possibilities of improving the sensitivity of mass spectrometer measurements. (USSR)
22 and accuracy
(Great Britain) This pump of the oil sealed radial vane type has greater efficiency and larger throughput by effective degassing of the oil. Starting after being idle under vacuum and when the stages are filled with oil, is made easier and there is more effective sealing of stages and lubrication of moving parts. The pumping capacity is increased without undue increase in the pump size. -(A&h&) Cenco Instr Corp, Brit Patent 1,075,34O,Patent Abstr, 7 (31) part B,
For evaluation of very small ion currents (below 10-l’ A) in magnetic mass spectrometers, the following method is described: the ion accelerating voltage is modulated by sawtooth voltage with peak-topeak amplitude corresponding to a narrow band of mass numbers (eg 198 to 201) and the signal from the mass spectrometer receiving amplifier is converted into phase-modulated pulses and demodulated. ln this way, very high accuracy in resolving isotopes was obtained, since with suitable time-base speed, ion current variations do not influence the mass peak recognition. As an example, the mass spectrum of Hg isotopes measured by MI-1305 mass spectrometer with total ion current of 10-l’ A is given. P I Chalov and U Mamyrov, Pribory Tekh Eksper, 12 (3), May-June
4th Aug 1967, 2.
1967, 123-125
‘1
1811. Rotary vacuum pump.
(in Russian). 619