- Email: [email protected]
764. Theoretical and experimental studies of the underlying processes and techniques of low pressure measurements
Classified abstracts 756-766 21 756. Centrifugal and axial flow pumps. Applications and operation. (Italy) C o n s t r u c t i o n a l details a n d operating specifications are given for various types o f centrifugal a n d axial flow p u m p s . D i a g r a m s are given for operational calculations by graphical methods. E c o n o m i c s are discussed for s o m e solutions to the given problems. A Finazzi, Scuola Azione, 1966, 38-71 (in Italian). 21 757. Rotary vane-type pump. (Great Britain) A rotor carrying diametral intersecting vanes is m o u n t e d eccentrically in a ported sleeve revolving at the s a m e speed as the rotor, sealing strips being interposed between the vanes a n d sleeve. F o r improved sealing, the strips are m a d e hollow, a n d are r o u n d e d where they engage the sleeve, eg, resilient inflatable t u b u l a r strips m a y be used. ( A u t h o r ) W Hubener, Brit Patent 1,052,169, Patent Abstr, 7 ( 3 ) p a r t B, 19th Jan 1967, 3. 22. G A U G E S
from a tungsten w irc~(0.1 m m diameter a n d 22 m m long), a t a n t a l u m a n o d e cylinder of diameter 25 m m a n d t a n t a l u m collector a n d screen at the top o f the anode. C a t h o d e holders were located 3 m m inside the a n o d e cylinder so the v, hole c a t h o d e h a d a potential barrier against positive alkali ion emission a n d parts outside this barrier were at suitable low temperatures. T h e anode-to-collector gap was 1.5 ram. A n o d e voltage o f r 400 V, c a t h o d e voltage of - 5 0 V, screen voltage o f : 40 V, collector voltage of 0 V, magnetic tield intensity of 480 Oe a n d emission current of 1 /~A were applied. This gauge h a s a linear relation between pressure a n d emission current in the range of 10 '; to 10 ~ torr with sensitivity of 7 . 6 x 10 -2 A / t o r t . It was calibrated by c o m p a r i s o n with the type 1M-12 Bayard-Alpcrt gauge with sensitivity of 1.5 × 10 ~-A / t o r r a n d good linearity up to 5 :< 10 -~ tort, and with th2 type M M - 1 4 S inverted m a g n e t r o n gauge with linearity up to 10 1~ torr a n d sensitivity of 3.1 × 10 -1 A/torr. "l-h::se m e a s u r e m e n t s are the first experiments calibrating linearity of the M M - 1 4 S gauge up to 10 'lz torr. T h e p u m p i n g effect o f the gauges was not investigated. G A Nicbiporovich, Pribory Tekh l:ksper, 11 (6), Nov-Dec 1966, 150154 (hz Russian).
22 758. Pressure-change indicator. ( U S S R ) A new, simple a n d reliable piece o f e q u i p m e n t for indicating pressure c h a n g e s (specially designed for keeping the pressure in gas-volumetric a p p a r a t u s c o n s t a n t ) is described. T h e principle is that o f the c h a n g e p r o d u c e d in the level o f a liquid in a large vessel on c h a n g i n g the pressure. T h e large vessel, filled with oil or mercury, has a fine side tube for indicating the pressure changes. T h e new a p p a r a t u s is free from defects c o m m o n to its predecessors such as high v a p o u r pressure o f the liquids employed, unstable sensitivity, a n d the tendency o f the working liquids to stick to the sides of the tube. T E Kafarov~ Za Tekhnicheskii Progress, No 10, 1966, 4 (in Russian). 22 759. Apparatus for testing and regulating vacuum-technological processes, ( U S S R ) A system for m e a s u r i n g a n d recording the pressure o f foreign gases ia m e r c u r y rectifiers at all stages of m a n u f a c t u r e is described. T h e system is based on the c o m b i n a t i o n of an a u t o m a t i c electronic potentiom~'ter a n d a rotating gauge with a variable c o m p r e s s i o n coefficient. T h e rotating g a u g e covers a pressure range of I0 i to 10 -7 tort, but its sensitivity is a function o f pressure; in order to increase the sensitivity in s o m e ranges, the c o m p r e s s i o n coefficient h a s to be adjusted, a n d convenient m e t h o d s o f effecting this are d i s c u s s : & T h e modified system enables pressures between 10 -~ a n d 10 -7 torr to be c o n t i n u o u s l y recorded with a fair degree o f accuracy; it m a y also serve as a control element in various a u t o m a t e d v a c u u m technological processes. 1 G Goloshcbekin and V V Morozov, lzv N-I Postoyan Toka, (J Direct Current Scientific Research Institute), 12, 1966, 206-212 (in
22 764. Theoretical and experimental studies of the underlying processes and techniques of low pressure measurements. ( U S A ) Progress is reported related to i m p r o v i n g the low pressure characteristics o f the S c h u e m a n n s u p p r e s s o r gauge a n d the v a c u u m work necessary to accomplish this. Problems with the gauge are associated with the o u t g a s s i n g o f the electrode structure during operations at pressures as low as 10 -~-' torr, the mechar.i:al structure of the electrodes a n d the B a r k h a u s e n oscillations. Efforts to reach lower pressures are discussed for the presently-used glass system as well as for metal systems. In a steel system initial results at 8 x I0 - n torr werc obtained. ' / h i s system is being outfitted with a well-trapped diffusion p u m p to m a i n t a i n low pressures during bakeout, thereby reducing saturation o f t h e metal by the gases present. A d s o r p t i o n o f gases at metal surfaces is being studied by the A u g e r process. R N Peacock, Rep NASA-CR-77333, Aug 1966 (Illinois Univ, Urbana,
Russian).
Coordinated Science Labs). 22
760. Discharge mechanism and the role of space charge in a coldcathode gauge. ( U S S R ) Experiments with cold-cathode gauges in v a c u u m systems based on oil-diffusion a n d cryogenic p u m p s arc described. T h e current in the g a u g e circuit was determined as a function o f magnetic field at various pressures a n d a n o d e voltages; the results indicated the f o r m a t i o n o f a n electron cloud near the anode, the space charge playing a considerable part in the m a i n t e n a n c e o f the discharge. Special experiments were m a d e to determine the electric-field distribution in the cloud, and a theory relating the rotatory electron current with the current in the gauge circuit was developed. By c o m bining the theory with experimental results, a general picture o f the processes taking place in the gauge at low pressures was built up. B A Sharevskii, Ukr Fiz Zh, 11 (12), Dec 1966 (in Ukrainian). 22 761. New variant of the double-focnsed mass-spectrometer. ( U S S R ) Design o f a double-focused m a s s - s p e c t r o m e t e r in which the electrostatic field o f a fiat capacitor with a bent b e a m entry operates as the ion energy analyzer, is described. M M Bredov and E G Ostroumova, Pribory Tekh Eksper, I1 (6), Nov.Dec 1966, 148-149 (in Russian). 22 762. Comparing calibrations of a hot cathode magnetron gauge and an inverted magnetron gauge in ultrahigh vacuum conditions. ( U S S R ) T h e hot c a t h o d e m a g n e t r o n gauge consisted o f a direct c a t h o d e m a d e 248
22 : 33 763. Triode ionizer with an ionization efficiency of 2 × 10 -:~. (USSR) T h e design of a polariscd ion source is described. This device consists o f a ring cathode system, two a n o d e s a n d an electron collector. T h e first a n o d e with the high potential shapes the electron b e a m coaxially with the molecular beam a n d the second a n o d e with the lower potential retards electrons to a suitable speed. A t o m s are ionized between the second a n o d e a n d the electron collector. With 1st a n o d e voltage of 2 kV, 2nd a n o d e voltage of 700 kV and collector voltage o f 600 V, the efficiency obtained was 2 × 10 -u. R P Slabospitskiy et al, Zh Tekh Fiz, 36 (12), Dec 1966, 2145-2147
(ill Russian).
22 765. Ion gauge for vapour pressure measurements below 1 x 10 -1° torr. (USA) Low pressure m e a s u r e m e n t s by Bayard-Alpert gauges arc limited by x-ray photoelectron currents at the ion collector equivalent to a pressure reading o f a b o u t 1 x 10 u tort. T h r o u g h efforts to reduce this x-ray current, the B-A structure has been modified whereby a beam of ions is extracted from the grid a n d bent a r o u n d a corner to a remote collector. By this geometry the collector is shielded from the x-ray source at the grid a n d the photoelectric current is reduced by a factor of 100, without incurring a loss in gauge sensitivity. A total pressure of 5 x 10 -13 torr, nitrogen equivalent, h a s been m e a s u r e d in a stainless steel v a c u u m system e m p l o y i n g ion sputtering a n d titanium sublimation as the m e a n s of evacuation. d C l-leimer and W H Hayward, Rev Sci lnstrum, 37, 1966, 1652-1654. 22 766. Pressure gauges. ( U S A ) T h e article is chiefly concerned with the B o u r d o n tube type pressure gauges, in which the m e d i u m under pressure which is to bc m e a s u r e d enters a closed end tube formed in a partial circle. T h u s , the fluid in the system usually is in direct contact with a working part of the gauge. Various types a n d grades o f gauges are described in s o m e detail together with the different uses for which they are suitable. Safety considerations are also discussed. P W Harland, Machhw Design, 38, 1966, 73-78.
from a tungsten w irc~(0.1 m m diameter a n d 22 m m long), a t a n t a l u m a n o d e cylinder of diameter 25 m m a n d t a n t a l u m collector a n d screen at the top o f the anode. C a t h o d e holders were located 3 m m inside the a n o d e cylinder so the v, hole c a t h o d e h a d a potential barrier against positive alkali ion emission a n d parts outside this barrier were at suitable low temperatures. T h e anode-to-collector gap was 1.5 ram. A n o d e voltage o f r 400 V, c a t h o d e voltage of - 5 0 V, screen voltage o f : 40 V, collector voltage of 0 V, magnetic tield intensity of 480 Oe a n d emission current of 1 /~A were applied. This gauge h a s a linear relation between pressure a n d emission current in the range of 10 '; to 10 ~ torr with sensitivity of 7 . 6 x 10 -2 A / t o r t . It was calibrated by c o m p a r i s o n with the type 1M-12 Bayard-Alpcrt gauge with sensitivity of 1.5 × 10 ~-A / t o r r a n d good linearity up to 5 :< 10 -~ tort, and with th2 type M M - 1 4 S inverted m a g n e t r o n gauge with linearity up to 10 1~ torr a n d sensitivity of 3.1 × 10 -1 A/torr. "l-h::se m e a s u r e m e n t s are the first experiments calibrating linearity of the M M - 1 4 S gauge up to 10 'lz torr. T h e p u m p i n g effect o f the gauges was not investigated. G A Nicbiporovich, Pribory Tekh l:ksper, 11 (6), Nov-Dec 1966, 150154 (hz Russian).
22 758. Pressure-change indicator. ( U S S R ) A new, simple a n d reliable piece o f e q u i p m e n t for indicating pressure c h a n g e s (specially designed for keeping the pressure in gas-volumetric a p p a r a t u s c o n s t a n t ) is described. T h e principle is that o f the c h a n g e p r o d u c e d in the level o f a liquid in a large vessel on c h a n g i n g the pressure. T h e large vessel, filled with oil or mercury, has a fine side tube for indicating the pressure changes. T h e new a p p a r a t u s is free from defects c o m m o n to its predecessors such as high v a p o u r pressure o f the liquids employed, unstable sensitivity, a n d the tendency o f the working liquids to stick to the sides of the tube. T E Kafarov~ Za Tekhnicheskii Progress, No 10, 1966, 4 (in Russian). 22 759. Apparatus for testing and regulating vacuum-technological processes, ( U S S R ) A system for m e a s u r i n g a n d recording the pressure o f foreign gases ia m e r c u r y rectifiers at all stages of m a n u f a c t u r e is described. T h e system is based on the c o m b i n a t i o n of an a u t o m a t i c electronic potentiom~'ter a n d a rotating gauge with a variable c o m p r e s s i o n coefficient. T h e rotating g a u g e covers a pressure range of I0 i to 10 -7 tort, but its sensitivity is a function o f pressure; in order to increase the sensitivity in s o m e ranges, the c o m p r e s s i o n coefficient h a s to be adjusted, a n d convenient m e t h o d s o f effecting this are d i s c u s s : & T h e modified system enables pressures between 10 -~ a n d 10 -7 torr to be c o n t i n u o u s l y recorded with a fair degree o f accuracy; it m a y also serve as a control element in various a u t o m a t e d v a c u u m technological processes. 1 G Goloshcbekin and V V Morozov, lzv N-I Postoyan Toka, (J Direct Current Scientific Research Institute), 12, 1966, 206-212 (in
22 764. Theoretical and experimental studies of the underlying processes and techniques of low pressure measurements. ( U S A ) Progress is reported related to i m p r o v i n g the low pressure characteristics o f the S c h u e m a n n s u p p r e s s o r gauge a n d the v a c u u m work necessary to accomplish this. Problems with the gauge are associated with the o u t g a s s i n g o f the electrode structure during operations at pressures as low as 10 -~-' torr, the mechar.i:al structure of the electrodes a n d the B a r k h a u s e n oscillations. Efforts to reach lower pressures are discussed for the presently-used glass system as well as for metal systems. In a steel system initial results at 8 x I0 - n torr werc obtained. ' / h i s system is being outfitted with a well-trapped diffusion p u m p to m a i n t a i n low pressures during bakeout, thereby reducing saturation o f t h e metal by the gases present. A d s o r p t i o n o f gases at metal surfaces is being studied by the A u g e r process. R N Peacock, Rep NASA-CR-77333, Aug 1966 (Illinois Univ, Urbana,
Russian).
Coordinated Science Labs). 22
760. Discharge mechanism and the role of space charge in a coldcathode gauge. ( U S S R ) Experiments with cold-cathode gauges in v a c u u m systems based on oil-diffusion a n d cryogenic p u m p s arc described. T h e current in the g a u g e circuit was determined as a function o f magnetic field at various pressures a n d a n o d e voltages; the results indicated the f o r m a t i o n o f a n electron cloud near the anode, the space charge playing a considerable part in the m a i n t e n a n c e o f the discharge. Special experiments were m a d e to determine the electric-field distribution in the cloud, and a theory relating the rotatory electron current with the current in the gauge circuit was developed. By c o m bining the theory with experimental results, a general picture o f the processes taking place in the gauge at low pressures was built up. B A Sharevskii, Ukr Fiz Zh, 11 (12), Dec 1966 (in Ukrainian). 22 761. New variant of the double-focnsed mass-spectrometer. ( U S S R ) Design o f a double-focused m a s s - s p e c t r o m e t e r in which the electrostatic field o f a fiat capacitor with a bent b e a m entry operates as the ion energy analyzer, is described. M M Bredov and E G Ostroumova, Pribory Tekh Eksper, I1 (6), Nov.Dec 1966, 148-149 (in Russian). 22 762. Comparing calibrations of a hot cathode magnetron gauge and an inverted magnetron gauge in ultrahigh vacuum conditions. ( U S S R ) T h e hot c a t h o d e m a g n e t r o n gauge consisted o f a direct c a t h o d e m a d e 248
22 : 33 763. Triode ionizer with an ionization efficiency of 2 × 10 -:~. (USSR) T h e design of a polariscd ion source is described. This device consists o f a ring cathode system, two a n o d e s a n d an electron collector. T h e first a n o d e with the high potential shapes the electron b e a m coaxially with the molecular beam a n d the second a n o d e with the lower potential retards electrons to a suitable speed. A t o m s are ionized between the second a n o d e a n d the electron collector. With 1st a n o d e voltage of 2 kV, 2nd a n o d e voltage of 700 kV and collector voltage o f 600 V, the efficiency obtained was 2 × 10 -u. R P Slabospitskiy et al, Zh Tekh Fiz, 36 (12), Dec 1966, 2145-2147
(ill Russian).
22 765. Ion gauge for vapour pressure measurements below 1 x 10 -1° torr. (USA) Low pressure m e a s u r e m e n t s by Bayard-Alpert gauges arc limited by x-ray photoelectron currents at the ion collector equivalent to a pressure reading o f a b o u t 1 x 10 u tort. T h r o u g h efforts to reduce this x-ray current, the B-A structure has been modified whereby a beam of ions is extracted from the grid a n d bent a r o u n d a corner to a remote collector. By this geometry the collector is shielded from the x-ray source at the grid a n d the photoelectric current is reduced by a factor of 100, without incurring a loss in gauge sensitivity. A total pressure of 5 x 10 -13 torr, nitrogen equivalent, h a s been m e a s u r e d in a stainless steel v a c u u m system e m p l o y i n g ion sputtering a n d titanium sublimation as the m e a n s of evacuation. d C l-leimer and W H Hayward, Rev Sci lnstrum, 37, 1966, 1652-1654. 22 766. Pressure gauges. ( U S A ) T h e article is chiefly concerned with the B o u r d o n tube type pressure gauges, in which the m e d i u m under pressure which is to bc m e a s u r e d enters a closed end tube formed in a partial circle. T h u s , the fluid in the system usually is in direct contact with a working part of the gauge. Various types a n d grades o f gauges are described in s o m e detail together with the different uses for which they are suitable. Safety considerations are also discussed. P W Harland, Machhw Design, 38, 1966, 73-78.