Valves

Classified abstracts 420--430 gases a n d v a p o u r s f r o m elastomer seals into high v a c u u m systems a n d it h a s been s h o w n that a t m o s p h e r i c p e r m e a t i o n during a n d after baking is usually the limiting factor in reaching low pressures. In order to be able to retain the convenience o f elastomer seals down into the U H V region, it is necessary to provide double o-rings a n d to evacuate the interspace so that p e r m e a t i o n o f the inner ring is eliminated. T h e advantages of double o-ring seals over metal seals lie in the speed a n d reliability with which they m a y be assembled. However, it is i m p o r t a n t to k n o w h o w far residual degassing f r o m the elastomer m a y limit the ultimate pressure, a n d to what extent organic c o n t a m i n ation m a y be introduced. A series of experiments was carried out on a n ultrahigh c h a m b e r having a large flange suitable for either doubte o-ring or metal seals. L de Csernatony and D J Crawley, Le Vide, 22 (131), Sept-Oct 1967. 277-279 (in French). 23

420. A static high pressure low temperature seal. (Great Britain) A m e t h o d o f p r o d u c i n g a d e m o u n t a b l e seal between a thin walled tube a n d a pressure vessel is described. It can be used from 0.1 torr to 500 a t m o s p h e r e s over the t e m p e r a t u r e range 90-300°K. T h e seal is based o n conically s h a p e d gaskets. B J Bailey and K Keflner, J Sci Instrum, 44 ( 11 ), 1967, 962 963. 23 421. The sealing of illuminators of large hydrogen bubble chambers. (Great Britain) In the sealing s y s t e m described, the v a c u u m sealing o f the working space o f a liquid h y d r o g e n bubble c h a m b e r is achieved by an inflatable element a n d three layers o f indium. Sealing is achieved by the flattening o f the i n d i u m gaskets as a result o f h i g h pressure helium introduced into the inflatable element. ( U S S R ) R M Lebedev et al, Cryogenics, 7 (5), 1967, 302-304. 24. V A L V E S 24 422. High vacuum valve. ( U S S R ) A stainless steel valve sealed by copper a n d resistant to temperature changes f r o m 20 to 600°C is described. T h e seat is pressed by Believille springs to avoid effects o f material dilatation. V I Petrov and A P Kobarenkov, Pribory Tekh Eksper, 12 (5), Sept Oct 1967, 243 (in Russian). 24 423. Equipment for producing calibrated leaks especially adapted for substances with melting points above room temperature. (Great Britain) A system o f calibrated leaks is described, which is based on holes m a d e in m o l y b d e n u m by electron b o m b a r d m e n t . T h e calibrated leak c a n be used for v a p o u r detectors, p r o d u c t i o n o f aerosols or gas leak detectors, in the range o f 5 × 10 -4 a t m cma/sec. (Italy) K Klein and L Verheyden, J Sci Instrum, 44 (I I), 1967, 954 956.

27. L E A K D E T E C T O R S A N D L E A K D E T E C T I O N 27 : 34 424. Leak detection technique improvement study for space vehicles. (USA) T h e following topics are covered by the report: a model o f the halogen gradient detector u s i n g t h e dual-flow principle: a theoretical a n d experimental study o f the p l a t i n u m diode; a n d the design o f a helium separation probe. T h e superiority o f Teflon over heated silica glass as a m e m b r a n e material for the given specifications is d e m o n s t r a t e d . Anon, Ohio University, Annual Rep, NASA-CR-87159; EER-7-6; AR-2-a, Jan 1967, 264 pages (Sci Tech Aerospace Reps, 5 (19), 3454, N67-33271). 27 : 63 425. Leak detection technique improvement study for space vehicles. (USA) A n extensive search o f the literature published prior to 1962 o n the subject o f leak detection a n d related fields h a s been carried out. T h e i n f o r m a t i o n collected h a s been stored in an a u t o m a t e d retrieval s y s t e m by m e a n s o f I B M cards a n d a c o m p u t e r so that information on a n y p h a s e o f the project m a y be readily available. Anon, Ohio University, Rep NASA-CR-86670; 1R-2-b, Jan 1967, 308 pages (Sci Teeh Aerospace Reps, 5 (18), 3272, ?467-32472).

194

28. H E A T I N G E Q U I P M E N T A N D T H E R M O M E T E R S 28:17 Thermal time constants of germanium thermometers at liquid helium temperatures. See abstract n u m b e r 370. 2,~ 426. New method of temperature control in capsule irradiation.(Japan) A m e t h o d of controlling the temperature of an irradiating fuel or material specimen is proposed. T h e m e t h o d is based on the control of the v a c u u m or helium pressure in the insulating gas gap s u r r o u n d i n g the specimen. F o r m u l a e for the calculation are given a n d results of m e a s u r e m e n t s are presented. T Hayashi and S Ouchi, .1 Nucl Sci "l~'clmol, 4 (7), 1967, 6 1 63.

III. V a c u u m applications 30. E V A P O R A T I O N A N D S P U T T E R 1 N ( ; 3(} : 31 Characteristic of the new Vidican type camera tube using CdSe as a target material. See abstract n u m b e r 457. 30 427. Preparation of high purity CdTe and CdS films by cathodic sputtering under ultrahigh vacuum. (France) A n o m a l o u s photoconductivity in c a d m i u m telluride a n d c a d m i u m sulphide films is attributed to the f o r m a t i o n o f electron traps by oxygen, a d s o r b e d during thin film g r o w t h a n d during annealing. In order to investigate the photoconductivity o f films u n c o n t a m i n a t e d by oxygen, C d T e fihns were prepared by cathodic sputtering in a glass bell-jar system p u m p e d by an ion p u m p , a titanium s u b l i m a t i o n p u m p a n d two sorption p u m p s . Pressures below 10 8 torr were attained after b a k e o u t o f the complete system. CdS films were prepared by sputtering at 3 to 4 10 ~ torr at a substrate temperature o f 170'C. T h e films obtained were e x a m i n e d by electron a n d X-ray diffraction techniques a n d their electrical a n d optical properties determined. It is concluded that this procedure affords pure, stoichiometric films and that the c o m b i n a t i o n of ion a n d sorption p u m p i n g has great advantages for cathodic sputtering procedures. G Brincourt and S Martinuzzi, Le Vide, 22 ( 131 ), Sept Oct 1967, 253 259 (ht French). 3O 428. Continuous metallizing machine to coat one or both faces of very thin electric films. (France) T h e m a c h i n e described allows the c o n t i n u o u s coating of one or both sides o f polymer fihns to produce thin film capacitors on an industrial scale. T h e m a c h i n e consists o f a system o f rollers h o u s e d in a v a c u u m c h a m b e r with a source o f a l u m i n i u m v a p o u r at the base o f the chamber. T h e polymer film (ethylene polyterephthalate, polycarbonate, polypropylene, polystyrene or kapton) is led t h r o u g h the roller system in a c o n t i n u o u s strip o f thickness 2-12 microns depending on the material. T w o rollers above the a l u m i n i u m vapour source expose first one then the other side o f the film to the metal vapour. These rollers are cooled by therrnal exchange with black body radiators. T h e refractory crucible in the metal v a p o u r source permits evaporation rates equivalent to 1000 A/sec, is durable a n d h a s very low degassing properties. T h e entire system is m a i n t a i n e d at 5 >: 10 5 to 10 4 torr by a 2000 litre/sec diffusion p u m p , a 500 ma/hr R o o t s p u m p a n d a 60 m~/hr mechanical p u m p . M Braguier and G Paricard, Le Vide, 22 ( 131 ), Sept Oct 1967,280 287

(in French). 3O 429. Ionic diffusion at the aluminium-aluminium oxide interface. (USA) Ionic diffusion currents m e a s u r e d in a metal-insulator-metal structure yield an activation energy of 1.60 eV at 550°K for a l u m i n i u m ions diffusing into a l u m i n i u m oxide. The altmainium was evaporated at I0 ~0 torr by using an electron gun. T h e a l u m i n i u m oxide was f o r m e d thermally from dry oxygen a d m i t t e d to a pressure o f 40 to 50 m t o r r while infrared quartz lamps heated the substratc to 550~K. P u m p i n g to low pressure preceded a second evaporation of a l u m i n i u m J H Christian and H L Taylor. J Appl Phys, 38 (10), 1967, 3843-3845. 3() 430. Gas incorporation into sputtered films. (USA) The concentration of a r g o n in sputtered nickel films has been obtained as a function of the film growth temperature, the discharge pressure, and the energy (bias voltage) with which the argon ions