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Some peculiarities of the discharge of a Penning tube at low pressures
Classified abstracts 136--147 m e a s u r e d with a p o r t i o n o f the s y s t e m i m m e r s e d in liquid helium. A discussion is given of variations in the residual m o d u l a t i o n factor o f the g a u g e in the presence o f extremely low gas pressures. ( U S A ) J P Hobson, J Vac Sci & Tech, 1 (1), Sept~Oct 1964, 1-6. 22:18 136. Discharge gauge for transient density measurements. (USA) T h e g a u g e operates on t h e P e n n i n g discharge principle with a r e s p o n s e time of less t h a n 100t~ sec. (USA) M E Levy, Rev Scilnst, 35 (9), Sept 1964, 1232-1233. 22:18 137. Some peculiarities of the discharge of a Penning tube at low pressures. ( USSR) T h e relative p r o p o r t i o n o f ions a n d electrons in the discharge b e a m f r o m a P e n n i n g t u b e d e p e n d s on the s t r e n g t h of the m a g n e t i c field applied as well as o n t h e pressure. In the particular case e x a m i n e d , t h e electron c o m p o n e n t u n d e r w e n t a s h a r p increase w h e n the field s t r e n g t h exceeded 8000 0 ° at 5 × 10 -8 torr. Yu E Kreindel and A S Ionov, Zh Tekh Fiz, 34 (7), July 1964, 1199-1205. English translation will a p p e a r in Soy Phys Tech Phys,
(USA), Jan 1965. 22 : 27 138. Ion gauge calibration at low pressures using a leak detector.
(usA) A simple m e t h o d for ion gauge calibration is presented. T h e flow rate of a p u r e g a s t h r o u g h the calibration cell a n d a k n o w n c o n d u c t a n c e is m e a s u r e d with a leak detector (or residual gas analyzer) on the h i g h pressures side of the diffusion p u m p . F r o m t h e k n o w n c o n d u c t a n c e a n d the increased flow rate the calibration pressure is calculated. P u m p i n g by walls a n d gauge does n o t interfere with calibration, since it is based on the flow rate o u t o f the calibration cell. T h e m e t h o d is illustrated by calibrating an ion gauge for h e l i u m a n d d e u t e r i u m , using a s t a n d a r d h e l i u m leak detector as flow meter. (USA) B B e r g s n o v - H a n s o n et al, J Vac Sci and Tech, I (1), Sept~Oct 1964,
7-9.
23. Plumbing 23 : 45 139. Installation of ceramic terminals in metal vacuum systems by electron beam welding. (USA) T h e a d v a n t a g e s o f electron b e a m welding o f ceramic t e r m i n a l s can be s u m m a r i z e d as follows: (1) A terminal which leaks after welding c a n be rewelded to eliminate the leak. (2) T h e r e is less c h a n c e of h e a t d a m a g e to the terminal w h e n installing by this m e t h o d . (3) T h e r e is n o oxide f o r m a t i o n in or a r o u n d t h e weld zone. (4) G r e a t e r terminal density c a n be achieved. (5) A b r o k e n terminal c a n be r e m o v e d a n d replaced w i t h o u t d i s t u r b i n g n e a r b y terminals.
( usa ) c D Jarvis, J Vac Sci and Techn, I (1), Sept/Oct 1964, 25-26. 23 140. Feedthroughs for UHV systems. (USA) In e x a m i n i n g the various electrical f e e d t h r o u g h materials available, two basic seals a p p e a r e d m o s t suitable: glass-to-metal a n d ceramicto-metal. E l a s t o m e r s are ruled o u t on a c c o u n t of their high outg a s s i n g rates a n d disintegration at elevated b a k e - o u t t e m p e r a t u r e s . R e c e n t w o r k h a s s h o w n that ceramic-to-metal seals w h e n designed into suitable m o u n t i n g configuration h a v e higher m e c h a n i c a l a n d t h e r m a l properties t h a n glass-to-metal seals a n d will m e e t t h e m o s t exacting r e q u i r e m e n t s of ultrahigh v a c u u m work. (USA) H Schwartz, Res & Develop, 15 (8), Aug 1964, 42--44. 23 141. Introduction of motion into a vacuum system by means of bimetallic elements. (USA) T h e i n t r o d u c t i o n o f m o t i o n into a v a c u u m s y s t e m is a c o m m o n p r o b l e m w h i c h h a s been solved in a n u m b e r o f ways. T h e a u t h o r s describe a novel way o f i n t r o d u c i n g accurately controlled translational m o t i o n in a v a c u u m t h r o u g h a static seal. A n electric c u r r e n t is t a k e n t h r o u g h the v a c u u m c h a m b e r wall by m e a n s of s t a n d a r d c o n n e c t i o n s a n d is used to heat a resistive element. This heat is t r a n s m i t t e d by radiation or c o n d u c t i o n to a bimetallic strip c o n n e c t e d in t u r n to the m o v a b l e parts. T h e principle h a s been applied to the c o n s t r u c t i o n of an adjustable slit i n c o r p o r a t e d in a small u l t r a h i g h v a c u u m m a s s spectrometer. (USA) P E McElligott et al, J Vac Sci and Techn, 1 (I), Sept~Oct 1964,
24-25. 84
24. Valves 24 142. Slide valve with remote control. (France) A v a c u u m - t i g h t slide valve is described, characterized by the fact that the sealing plate is in the f o r m of a circular disk w h i c h is p r e s s u r e loaded in the closed position. O p e n i n g the valve is carried o u t by a remotely controlled rod which releases the s p r i n g load a n d enables the disk to m o v e laterally w i t h o u t friction. In the open position the valve p a s s a g e s are completely clear. (Italy) P Neri and V Vannini, Le Vide, 19 (113), Sept/Oct 1964, 304-341.
25. Baffles, traps and refrigeration equipment 25 : 16 143. All glass sorption vacuum trap. (USA) T h e material u s e d as a t r a p p i n g a g e n t is C o r n i n g type 7930 in t h e f o r m of discs (50 m m d i a m e t e r a n d 3 m m thick) s u p p o r t e d inside a pyrex tube. T h e p e r f o r m a n c e is c o m p a r a b l e with t h a t o f a zeolite or a l u m i n i u m trap, with the a d v a n t a g e o f absence of dust. ( U S A ) F B Hailer, Rev Sci lnstrum, 35 (10), Oct 1964, 1356-1357. 25 : 26 144. Device for the automatic replenishing of liquid nitrogen traps.
(France) T h e liquid nitrogen reserve is c o n t a i n e d in a D e w a r vessel fitted with a lid a n d variable leak to the a t m o s p h e r e . T h e leak is controlled by the c h a n g e in resistance o f a coil partly i m m e r s e d in the trap liquid. A decrease in the level o f the latter, alters the coil resist a n c e a n d this in turn reduces the leak to the a t m o s p h e r e o f the store. T h e resultant rise in pressure transfers liquid nitrogen to the trap till the original level is restored. (France) G Mesnard et al, Le Vide, 19 (112), July 1964, 239.
26. Automatic protective and control equipment 26 Device for the automatic replenishing of liquid nitrogen traps. See abstract n u m b e r 144. 26 Automatic control of vacuum spray during installations. See abstract n u m b e r 175. 26 145. Doser for microquantities of gas. (USA) T h e doser consists of a calibrated capillary tube with m e r c u r y cutoffs. T h e gas can be t r a p p e d at p r e s s u r e s r a n g i n g f r o m a t m o s p h e r i c to 0.5~ a n d is s u b s e q u e n t l y transferred to the s y s t e m where it is required. Possible doses r a n g e f r o m 1012 to 10 ]9 a t o m s . (USA) A Weinstein and I-[ C Friedman, Rev Sci lnstrum, 35 (8), Aug 1964,
1083-1084.
27. Leak detectors and leak detection 27 Ion gauge calibration at low pressures using a leak detector. See abstract n u m b e r 138.
28. Heating equipment and thermometers 28 Preparation of thin targets for work with charged particles. See abstract n u m b e r 158. 28 Radiation electronic vacuum furnaces. See abstract n u m b e r 178. 28 : 42 146. Ceramic crucibles for electron bombardment heating. (USA) Electron b o m b a r d m e n t p r o d u c e s excellent deposits o f copper a n d gold u s i n g crucibles m a d e of beryllia, a l u m i n a or zirconia. Beryll i u m deposits on plastic strips were obtained f r o m a beryllia crucible at the relatively low t e m p e r a t u r e of 1100-1200 °C. J W Voigt and K W Foster, Rev Sci lnstrum, 35 (8), Aug 1964,
1087. 28 : 37 147. Treatment of silicon by electron bombardment. (France) A n electron b o m b a r d m e n t f u r n a c e is described which c a n deal with a c o n t i n u o u s s u p p l y of c o m m e r c i a l silicon needles as o b t a i n e d by the P a s t o r process (needles are 5-10 m m long a n d 2-3 m m diameter). T h e fused p r o d u c t leaves the v a c u u m f u r n a c e in the f o r m of cylindrical rods, approx. 15 m m diameter a n d 2 0 - 3 0 c m long. T h e final p r o d u c t is practically free of m e t a l impurities s u c h as Sb, M n , AI, Fe, N a , Pb a n d Sn. There is n o d o u b t t h a t this m e t h o d will p r o d u c e silicon of high purity. T h e d i s a d v a n t a g e is the
(USA), Jan 1965. 22 : 27 138. Ion gauge calibration at low pressures using a leak detector.
(usA) A simple m e t h o d for ion gauge calibration is presented. T h e flow rate of a p u r e g a s t h r o u g h the calibration cell a n d a k n o w n c o n d u c t a n c e is m e a s u r e d with a leak detector (or residual gas analyzer) on the h i g h pressures side of the diffusion p u m p . F r o m t h e k n o w n c o n d u c t a n c e a n d the increased flow rate the calibration pressure is calculated. P u m p i n g by walls a n d gauge does n o t interfere with calibration, since it is based on the flow rate o u t o f the calibration cell. T h e m e t h o d is illustrated by calibrating an ion gauge for h e l i u m a n d d e u t e r i u m , using a s t a n d a r d h e l i u m leak detector as flow meter. (USA) B B e r g s n o v - H a n s o n et al, J Vac Sci and Tech, I (1), Sept~Oct 1964,
7-9.
23. Plumbing 23 : 45 139. Installation of ceramic terminals in metal vacuum systems by electron beam welding. (USA) T h e a d v a n t a g e s o f electron b e a m welding o f ceramic t e r m i n a l s can be s u m m a r i z e d as follows: (1) A terminal which leaks after welding c a n be rewelded to eliminate the leak. (2) T h e r e is less c h a n c e of h e a t d a m a g e to the terminal w h e n installing by this m e t h o d . (3) T h e r e is n o oxide f o r m a t i o n in or a r o u n d t h e weld zone. (4) G r e a t e r terminal density c a n be achieved. (5) A b r o k e n terminal c a n be r e m o v e d a n d replaced w i t h o u t d i s t u r b i n g n e a r b y terminals.
( usa ) c D Jarvis, J Vac Sci and Techn, I (1), Sept/Oct 1964, 25-26. 23 140. Feedthroughs for UHV systems. (USA) In e x a m i n i n g the various electrical f e e d t h r o u g h materials available, two basic seals a p p e a r e d m o s t suitable: glass-to-metal a n d ceramicto-metal. E l a s t o m e r s are ruled o u t on a c c o u n t of their high outg a s s i n g rates a n d disintegration at elevated b a k e - o u t t e m p e r a t u r e s . R e c e n t w o r k h a s s h o w n that ceramic-to-metal seals w h e n designed into suitable m o u n t i n g configuration h a v e higher m e c h a n i c a l a n d t h e r m a l properties t h a n glass-to-metal seals a n d will m e e t t h e m o s t exacting r e q u i r e m e n t s of ultrahigh v a c u u m work. (USA) H Schwartz, Res & Develop, 15 (8), Aug 1964, 42--44. 23 141. Introduction of motion into a vacuum system by means of bimetallic elements. (USA) T h e i n t r o d u c t i o n o f m o t i o n into a v a c u u m s y s t e m is a c o m m o n p r o b l e m w h i c h h a s been solved in a n u m b e r o f ways. T h e a u t h o r s describe a novel way o f i n t r o d u c i n g accurately controlled translational m o t i o n in a v a c u u m t h r o u g h a static seal. A n electric c u r r e n t is t a k e n t h r o u g h the v a c u u m c h a m b e r wall by m e a n s of s t a n d a r d c o n n e c t i o n s a n d is used to heat a resistive element. This heat is t r a n s m i t t e d by radiation or c o n d u c t i o n to a bimetallic strip c o n n e c t e d in t u r n to the m o v a b l e parts. T h e principle h a s been applied to the c o n s t r u c t i o n of an adjustable slit i n c o r p o r a t e d in a small u l t r a h i g h v a c u u m m a s s spectrometer. (USA) P E McElligott et al, J Vac Sci and Techn, 1 (I), Sept~Oct 1964,
24-25. 84
24. Valves 24 142. Slide valve with remote control. (France) A v a c u u m - t i g h t slide valve is described, characterized by the fact that the sealing plate is in the f o r m of a circular disk w h i c h is p r e s s u r e loaded in the closed position. O p e n i n g the valve is carried o u t by a remotely controlled rod which releases the s p r i n g load a n d enables the disk to m o v e laterally w i t h o u t friction. In the open position the valve p a s s a g e s are completely clear. (Italy) P Neri and V Vannini, Le Vide, 19 (113), Sept/Oct 1964, 304-341.
25. Baffles, traps and refrigeration equipment 25 : 16 143. All glass sorption vacuum trap. (USA) T h e material u s e d as a t r a p p i n g a g e n t is C o r n i n g type 7930 in t h e f o r m of discs (50 m m d i a m e t e r a n d 3 m m thick) s u p p o r t e d inside a pyrex tube. T h e p e r f o r m a n c e is c o m p a r a b l e with t h a t o f a zeolite or a l u m i n i u m trap, with the a d v a n t a g e o f absence of dust. ( U S A ) F B Hailer, Rev Sci lnstrum, 35 (10), Oct 1964, 1356-1357. 25 : 26 144. Device for the automatic replenishing of liquid nitrogen traps.
(France) T h e liquid nitrogen reserve is c o n t a i n e d in a D e w a r vessel fitted with a lid a n d variable leak to the a t m o s p h e r e . T h e leak is controlled by the c h a n g e in resistance o f a coil partly i m m e r s e d in the trap liquid. A decrease in the level o f the latter, alters the coil resist a n c e a n d this in turn reduces the leak to the a t m o s p h e r e o f the store. T h e resultant rise in pressure transfers liquid nitrogen to the trap till the original level is restored. (France) G Mesnard et al, Le Vide, 19 (112), July 1964, 239.
26. Automatic protective and control equipment 26 Device for the automatic replenishing of liquid nitrogen traps. See abstract n u m b e r 144. 26 Automatic control of vacuum spray during installations. See abstract n u m b e r 175. 26 145. Doser for microquantities of gas. (USA) T h e doser consists of a calibrated capillary tube with m e r c u r y cutoffs. T h e gas can be t r a p p e d at p r e s s u r e s r a n g i n g f r o m a t m o s p h e r i c to 0.5~ a n d is s u b s e q u e n t l y transferred to the s y s t e m where it is required. Possible doses r a n g e f r o m 1012 to 10 ]9 a t o m s . (USA) A Weinstein and I-[ C Friedman, Rev Sci lnstrum, 35 (8), Aug 1964,
1083-1084.
27. Leak detectors and leak detection 27 Ion gauge calibration at low pressures using a leak detector. See abstract n u m b e r 138.
28. Heating equipment and thermometers 28 Preparation of thin targets for work with charged particles. See abstract n u m b e r 158. 28 Radiation electronic vacuum furnaces. See abstract n u m b e r 178. 28 : 42 146. Ceramic crucibles for electron bombardment heating. (USA) Electron b o m b a r d m e n t p r o d u c e s excellent deposits o f copper a n d gold u s i n g crucibles m a d e of beryllia, a l u m i n a or zirconia. Beryll i u m deposits on plastic strips were obtained f r o m a beryllia crucible at the relatively low t e m p e r a t u r e of 1100-1200 °C. J W Voigt and K W Foster, Rev Sci lnstrum, 35 (8), Aug 1964,
1087. 28 : 37 147. Treatment of silicon by electron bombardment. (France) A n electron b o m b a r d m e n t f u r n a c e is described which c a n deal with a c o n t i n u o u s s u p p l y of c o m m e r c i a l silicon needles as o b t a i n e d by the P a s t o r process (needles are 5-10 m m long a n d 2-3 m m diameter). T h e fused p r o d u c t leaves the v a c u u m f u r n a c e in the f o r m of cylindrical rods, approx. 15 m m diameter a n d 2 0 - 3 0 c m long. T h e final p r o d u c t is practically free of m e t a l impurities s u c h as Sb, M n , AI, Fe, N a , Pb a n d Sn. There is n o d o u b t t h a t this m e t h o d will p r o d u c e silicon of high purity. T h e d i s a d v a n t a g e is the