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On the conditions of the performance of an absolute mercury manometer
VACUUM Classified A b s t r a c t s
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Vacuum
Apparatus
and Auxiliaries
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II
Abstract No. ana ]~eferences
Contd.
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O
inch diameter and corrugated over the remaining area of the surface. The corrugations were formed b y a spinning process, described in detail, and were a b o u t 0.01 inch deep. Only copper and silver foil was found to be flee from pin holes and p o r o s i t y in this application. The finished-machined d i a p h r a g m h a d a t u r n e d d o w n rim a b o u t 0.03 inch deep which after a s s e m b l y of the d i a p h r a g m was soldered to the s u p p o r t in the gauge head. The u p p e r condenser plate, 11/16th inch wide and m o u n t e d on a bridge, faces the flat centre p a r t of the diap h r a g m at a distance of a b o u t 0.01 inch. A circuit d i a g r a m is given. Only one valve, an electron-coupled oscillator, is used. A n y change in capacity is converted into a frequency change. The capacity change depends on the position of the diaphragm. If the d i a p h r a g m is in a n e u t r a l position, i.e. b o t h sides are evacuated to the same pressure, the frequency is a b o u t 6.6 Mc/s. If the pressure difference across the d i a p h r a g m is a b o u t 100 H g the frequency is decreased to a b o u t 5.8 Mc/s. The dial of the i n s t r u m e n t tlas 100 equal divisions b u t as the response of the i n s t r u m e n t is n o t linear, due to the particular t y p e of electrical e q u i p m e n t used, a calibration curve is required. T w o s t a n d a r d and one special m e t h o d of calibration are mentioned. I n the case of the latter a 5 1. gas reservoir and the m a n o m e t e r to be calibrated are joined to the inlet leak of the m a s s spectrometer. A sample of gas is filled into a 5 m 1. gas pipette, its pressure in the pipette is determined and t h e n the gas is transferred to the reservoir b y m e a n s of a Toepler p u m p . The calculated pressure of the gas in the reservoir is c o m p a r e d w i t h t h e respective reading of the m i c r o m a n o m e t e r . I n operation, at a pressure difference of 200 /~ H g the d i a p h r a g m touches the u p p e r condenser plate. I n this m a n n e r the d i a p h r a g m is protected against excessive m o v e m e n t which m a y result in p e r m a n e n t distortion. Sommaire : Construction simple d ' u n d i a p h r a g m e m i c r o m a n o m ~ t r e p o u r l'emploi dans les spectrom~tres de masse afin d'analyser u n m61ange de gaz.
Sorption and Desorption of Gas in the Cold-Cathode Ionisation Gauge United Kingdom. I t is k n o w n t h a t , as distinct from the case of the hot-cathode ionisation gauge, the coldcathode P e n n i n g gauge sorbs gases in quantities which affect the readings for m a n y gases and v a p o u r s . The e x p e r i m e n t s r e p o r t e d here f o r m an extension of the w o r k carried o u t b y P e n n i n g (Physica 4, 1937, 71). The gauge employed in the e x p e r i m e n t s h a d a cylindrical anode, 2 cm. diameter and 2½ cm. long, which w a s operated at e a r t h potential. The end plates were a p p r o x i m a t e l y 0.3. cm. a w a y from the anode and where at a potential variable f r o m 0 to-4,000 V. The magnetic field h a d a s t r e n g t h of 900 G along the axis of t h e cylinder. The experimental a r r a n g e m e n t s i n c o r p o r a t e d a 3-inch. oil diffusion p u m p (Apiezon A oil), a needle valve and 2 h o t cathode ionisation gauges. One of the hot-cathode ionisation gauges was situated in front, and one, together w i t h the P e n n i n g gauge, at the end of a U - s h a p e d t u b u l a t i o n leading t h r o u g h a cold trap. Calibratiou curves of the P e n n i n g gauge for argon are given. The rate of gas c l e a n - u p was determined on the base of the f o r m u l a Q = C [(P1--PI)-- (P.--P,~)] (lusec) where C is the conductance of the piece of t u b i n g between the gauges, P1 and P2 the pressure readings at either end of the t u b e w i t h the P e n n i n g gauge working, and P~ and P~ the corresponding pressures w i t h the Penning gauge switched off. The following gases were investigated : nitrogen, air, w a t e r vapour, ethyl ether, carbon tetrachloride, argon and hydrogen. E x c e p t ethyl ether all gases gave similar results which are s h o w n in graphs. E t h y l ether was the only gas where sorption could be observed to continue for some time after the P e n n i n g gauge h a d been switched off. The results for p e r m a n e n t gases were independent of the use of the trap. The P e n n i n g gauge a b s o r b s residual v a p o u r s coming from the oil diffusion p u m p in the same w a y as the h o t cathode ionisation gauge. I n an e x p e r i m e n t w i t h a high-speed ionisation gauge in front of the t u b u l a t i o n the ultimate pressure of the p u m p was indicated to be 2 x 10 -5 mm. H g on the ionisation gauge, and 10 -~ m m . H g on the P e n n i n g gauge. The desorption rate at room t e m p e r a t u r e never exceeds 1 % of the sorption rate observed, b u t can be speeded up b y baking the gauge. The gas given up during b u r s t s caused b y baking is of the same order of m a g n i t u d e as the gas originally sorbed. The error of reading of the pressure caused b y the p u m p i n g effect of the discharge can be appreciable and is d e m o n s t r a t e d for the case of nitrogen in a table. No definite conclusions can be d r a w n on the clean-up mechanism. The clean-up m a y result either from ions being driven into the gauge electrode or b y gas adsorbed on electrode material s p u t t e r e d onto the walls of the gauge envelope. The results of the e x p e r i m e n t s indicated t h a t the former t y p e of m e c h a n i s m is more likely to be responsible for the cleanup b u t t h e latter t y p e c a n n o t be completely ignored in view of the results with ethyl ether. Sornmaire: L a vitesse de l ' a b a i s s e m e n t de pression caus6 p a r la jauge ~t ionisation £ cathode froide a 5t~ 6tudi6e.
On the Conditions of the Performance of an Absolute Mercury Manometer Russia. A. description is given of the P e a r s o n M a n o m e t e r used for measuring pressures of gas m i x t u r e s containing u p to 90% of w a t e r vapour. The range of pressures m e a s u r e d varied from 0.01 to 1.5 ram. Hg. The sensitivity over t h e entire range was 0.002 m m . The original p a p e r b y P e a r s o n o m i t t e d several i m p o r t a n t considerations for effective use which are here described. These include the strict t h e r m o s t a t i n g of the m a n o m e t e r below r o o m t e m p e r a t u r e (15°C), the reduction of jolts and shakes, the p u r i t y of the m e r c u r y and the cleanliness of the glass surfaces. W h e n the m a n o m e t e r is used for t h e r m a l analysis of gaseous m i x t u r e s it is necessary to take into account the t e m p e r a t u r e of the gas investigated and to correct b y the R e y n o l d s formula. The use of such a m a n o m e t e r is r e c o m m e n d e d for the analysis of gaseous m i x t u r e s containing easily condensable components. (Science Abstracts) Sommaire : D~scription d ' u n m a n o m ~ t r e ~. m e r c u r e P e a r s o n employ6 p o u r la mesure des pressions de m~langes de gaz c o n t e n a n t j u s q u ' ~ 90 % de v a p e u r d'eau.
October, 1953
Vacuum Vol. I l l No. d
Article by D. B. Cook & C. J. Danby J. Sci. Instrum. 3o, July 1953 238-240
143qi
Article by J. H. Leck J. 8ci. Instrum. 30, August 1953 271-274
144/II
Article by V. T. Slavianskii Zh. Tekh. Fiz. 22, No. 11, 1952 1881-1884
457
II - -
Vacuum
Apparatus
and Auxiliaries
--
II
Abstract No. ana ]~eferences
Contd.
O
O
inch diameter and corrugated over the remaining area of the surface. The corrugations were formed b y a spinning process, described in detail, and were a b o u t 0.01 inch deep. Only copper and silver foil was found to be flee from pin holes and p o r o s i t y in this application. The finished-machined d i a p h r a g m h a d a t u r n e d d o w n rim a b o u t 0.03 inch deep which after a s s e m b l y of the d i a p h r a g m was soldered to the s u p p o r t in the gauge head. The u p p e r condenser plate, 11/16th inch wide and m o u n t e d on a bridge, faces the flat centre p a r t of the diap h r a g m at a distance of a b o u t 0.01 inch. A circuit d i a g r a m is given. Only one valve, an electron-coupled oscillator, is used. A n y change in capacity is converted into a frequency change. The capacity change depends on the position of the diaphragm. If the d i a p h r a g m is in a n e u t r a l position, i.e. b o t h sides are evacuated to the same pressure, the frequency is a b o u t 6.6 Mc/s. If the pressure difference across the d i a p h r a g m is a b o u t 100 H g the frequency is decreased to a b o u t 5.8 Mc/s. The dial of the i n s t r u m e n t tlas 100 equal divisions b u t as the response of the i n s t r u m e n t is n o t linear, due to the particular t y p e of electrical e q u i p m e n t used, a calibration curve is required. T w o s t a n d a r d and one special m e t h o d of calibration are mentioned. I n the case of the latter a 5 1. gas reservoir and the m a n o m e t e r to be calibrated are joined to the inlet leak of the m a s s spectrometer. A sample of gas is filled into a 5 m 1. gas pipette, its pressure in the pipette is determined and t h e n the gas is transferred to the reservoir b y m e a n s of a Toepler p u m p . The calculated pressure of the gas in the reservoir is c o m p a r e d w i t h t h e respective reading of the m i c r o m a n o m e t e r . I n operation, at a pressure difference of 200 /~ H g the d i a p h r a g m touches the u p p e r condenser plate. I n this m a n n e r the d i a p h r a g m is protected against excessive m o v e m e n t which m a y result in p e r m a n e n t distortion. Sommaire : Construction simple d ' u n d i a p h r a g m e m i c r o m a n o m ~ t r e p o u r l'emploi dans les spectrom~tres de masse afin d'analyser u n m61ange de gaz.
Sorption and Desorption of Gas in the Cold-Cathode Ionisation Gauge United Kingdom. I t is k n o w n t h a t , as distinct from the case of the hot-cathode ionisation gauge, the coldcathode P e n n i n g gauge sorbs gases in quantities which affect the readings for m a n y gases and v a p o u r s . The e x p e r i m e n t s r e p o r t e d here f o r m an extension of the w o r k carried o u t b y P e n n i n g (Physica 4, 1937, 71). The gauge employed in the e x p e r i m e n t s h a d a cylindrical anode, 2 cm. diameter and 2½ cm. long, which w a s operated at e a r t h potential. The end plates were a p p r o x i m a t e l y 0.3. cm. a w a y from the anode and where at a potential variable f r o m 0 to-4,000 V. The magnetic field h a d a s t r e n g t h of 900 G along the axis of t h e cylinder. The experimental a r r a n g e m e n t s i n c o r p o r a t e d a 3-inch. oil diffusion p u m p (Apiezon A oil), a needle valve and 2 h o t cathode ionisation gauges. One of the hot-cathode ionisation gauges was situated in front, and one, together w i t h the P e n n i n g gauge, at the end of a U - s h a p e d t u b u l a t i o n leading t h r o u g h a cold trap. Calibratiou curves of the P e n n i n g gauge for argon are given. The rate of gas c l e a n - u p was determined on the base of the f o r m u l a Q = C [(P1--PI)-- (P.--P,~)] (lusec) where C is the conductance of the piece of t u b i n g between the gauges, P1 and P2 the pressure readings at either end of the t u b e w i t h the P e n n i n g gauge working, and P~ and P~ the corresponding pressures w i t h the Penning gauge switched off. The following gases were investigated : nitrogen, air, w a t e r vapour, ethyl ether, carbon tetrachloride, argon and hydrogen. E x c e p t ethyl ether all gases gave similar results which are s h o w n in graphs. E t h y l ether was the only gas where sorption could be observed to continue for some time after the P e n n i n g gauge h a d been switched off. The results for p e r m a n e n t gases were independent of the use of the trap. The P e n n i n g gauge a b s o r b s residual v a p o u r s coming from the oil diffusion p u m p in the same w a y as the h o t cathode ionisation gauge. I n an e x p e r i m e n t w i t h a high-speed ionisation gauge in front of the t u b u l a t i o n the ultimate pressure of the p u m p was indicated to be 2 x 10 -5 mm. H g on the ionisation gauge, and 10 -~ m m . H g on the P e n n i n g gauge. The desorption rate at room t e m p e r a t u r e never exceeds 1 % of the sorption rate observed, b u t can be speeded up b y baking the gauge. The gas given up during b u r s t s caused b y baking is of the same order of m a g n i t u d e as the gas originally sorbed. The error of reading of the pressure caused b y the p u m p i n g effect of the discharge can be appreciable and is d e m o n s t r a t e d for the case of nitrogen in a table. No definite conclusions can be d r a w n on the clean-up mechanism. The clean-up m a y result either from ions being driven into the gauge electrode or b y gas adsorbed on electrode material s p u t t e r e d onto the walls of the gauge envelope. The results of the e x p e r i m e n t s indicated t h a t the former t y p e of m e c h a n i s m is more likely to be responsible for the cleanup b u t t h e latter t y p e c a n n o t be completely ignored in view of the results with ethyl ether. Sornmaire: L a vitesse de l ' a b a i s s e m e n t de pression caus6 p a r la jauge ~t ionisation £ cathode froide a 5t~ 6tudi6e.
On the Conditions of the Performance of an Absolute Mercury Manometer Russia. A. description is given of the P e a r s o n M a n o m e t e r used for measuring pressures of gas m i x t u r e s containing u p to 90% of w a t e r vapour. The range of pressures m e a s u r e d varied from 0.01 to 1.5 ram. Hg. The sensitivity over t h e entire range was 0.002 m m . The original p a p e r b y P e a r s o n o m i t t e d several i m p o r t a n t considerations for effective use which are here described. These include the strict t h e r m o s t a t i n g of the m a n o m e t e r below r o o m t e m p e r a t u r e (15°C), the reduction of jolts and shakes, the p u r i t y of the m e r c u r y and the cleanliness of the glass surfaces. W h e n the m a n o m e t e r is used for t h e r m a l analysis of gaseous m i x t u r e s it is necessary to take into account the t e m p e r a t u r e of the gas investigated and to correct b y the R e y n o l d s formula. The use of such a m a n o m e t e r is r e c o m m e n d e d for the analysis of gaseous m i x t u r e s containing easily condensable components. (Science Abstracts) Sommaire : D~scription d ' u n m a n o m ~ t r e ~. m e r c u r e P e a r s o n employ6 p o u r la mesure des pressions de m~langes de gaz c o n t e n a n t j u s q u ' ~ 90 % de v a p e u r d'eau.
October, 1953
Vacuum Vol. I l l No. d
Article by D. B. Cook & C. J. Danby J. Sci. Instrum. 3o, July 1953 238-240
143qi
Article by J. H. Leck J. 8ci. Instrum. 30, August 1953 271-274
144/II
Article by V. T. Slavianskii Zh. Tekh. Fiz. 22, No. 11, 1952 1881-1884
457