VACUUM

Classified A b s t r a c t s

O

O

I I - - V a c u u m Apparatus and Auxi l iar ies - - I I Contd.

Some Remarks on Ion P u m p s

Hungary. The work ing pr inciple of i on - t r anspo r t and ion-get te r p u m p s is br ief ly discussed. The func t ion of t he se p u m p s depends on t h e anode -ca thode dis tance, t h e vol tage, t he cu r r en t densi ty , t he condi t ion of t he ca thode sur face and t he gaseous a tmosphe re .

Sommaire : Le proc6d6 de p o m p a g e des p o m p e s ~ t r a n s p o r t ionique ou des pompes ge t te r ionique es t h r i 6 v e m e n t discut6.

Some Theoretical and Experimental Observations on the Ultimate Vacuum Obtainable in Vapour P u m p s

See A b s t r a c t No. : 69 / I

The Theory of High-Speed Oil Diffusion P u m p s

United Kingdom. This pape r is concerned wi th the ac t ion of t he top je t of f r ac t iona t ing p u m p s ill which all j e t towers e x t e n d to the boiler. Th i s je t is responsible for t he h igh speed of evacua t ion a t low pressures . The m a g n i t u d e of tile p ressure g rad ien t in t he cent ra l tower which leads to t he top jet , and t he m a n n e r in wh ich t he v a p o u r b e a m spreads as i t m o v e s ou t wa rds f rom the je t ape r tu re affects t he speed and can resu l t in a s u b s t a n t i a l loss of speed. A first order t heo ry is developed f rom which a reIa t ionship be tween t he speed of t he t op je t and i ts ape r tu re is es tabl ished, and theore t ica l curves for t h e air speed of a 16-inch p u m p as a func t ion of t h e rad ius of t he cent ra l tower, wh ich agree wi th e x p e r i m e n t a l resul ts , show t h a t for m a x i m u m speed an o p t i m u m ape r tu re exists . Smaller and larger p u m p s w i th cent ra l tower d i ame te r s de t e rmined f rom similar theore t ica l curves h a v e a h i gh efficiency and are able to p roduce v a c u a close to 10 .7 ram. H g w i t h o u t t he a id of t raps . T h e h igh u l t i m a t e v a c u u m toge the r wi th t he adequa t e speed of t he subs id i a ry je t s and t he h igh l imi t ing fore p ressure of t hese p u m p s m a k e t h e m par t i cu la r ly su i tab le for use wi th par t ic le accelerators. I t was found expe r imen t a l l y t h a t t he o p t i m u m angle be tween t he je t and the hor izonta l is abou t 45 ° and t h a t for a pa r t i cu la r a r r a n g e m e n t t he speed is a lmos t i n d e p e n d e n t of the w id th of t he slit, f rom which t he v a p o u r b e a m emerges, in t h e r ange 0 .3-0.6 cm. T he discuss ion sets ou t t h e a d v a n t a g e s of increas ing t he n u m b e r of j e t s in 6 - inch . or larger p u m p s , to four.

Sommaire : Cet articIe es t une 4rude th6or ique du m6can i sme de t rava i l des p o m p e s k diffusion ~ huile. On d iscute auss i les difficult4s rencontr6es , pour ob ten i r de g randes vi tesses de p o m p a g e avec l 'hydrog6ne .

Correct Use of the Formula for Apparent Pumping Speed See A b s t r a c t No. : 68 / I

Improvements Relating to V a c u u m P u m p s of the Vapour Jet Type

United Kingdom. I n a conven t iona l v a p o u r p u m p each je t usua l ly t akes t he form of a d ive rgen t a n n u l a r nozzle fed by a cent ra l v a p o u r tube , t he p u m p e d gas being d r a w n downwards be tween t he ou te r edge of t he nozzle and t he s u r r o u n d i n g p u m p wall. I n t he a r r a n g e m e n t described here t he a n n u l a r nozzle is s i tua ted close to t he p u m p wall and tile p u m p e d gas passes down t h r o u g h i ts inner per iphery . The nozzle is fed wi th vapou r by a lagged t u b e ex te rna l to t h e p u m p and is designed so t h a t t he inner b o u n d a r y of t he je t converges to an apex in t h e cent re while t he ou te r b o u n d a r y s t r ikes the cold wall in t he n o r m a l way. I t is c la imed that t h e hol low conical v a p o u r s t r e a m so fo rmed cons t i tu te s a barr ier wh ich largely e l iminates t he back-di f fus ion of both , v a p o u r and en t r a ined gas, f rom t he region nea r t he cold wall into t he h igh v a c u u m side.

Somma~ire : L a r6al isat ion d ' u n e p o m p e k in ject ion 6quipee d ' u n in jec teur p r o d u i s a n t un j e t conique de v a p e u r d ' u n t y p e par t icu l ie r es t d6crite. Ce sys tgme est dit, de r6duire le r i sque d ' u n re tour de v a p e u r et de l ' e n t r a i n e m e n t de gaz d a n s l 'apparei l .

High V a c u u m Diffusion P u m p

United States. The patent describes a device for preventing displacement of the jet assembly of a diffusion pump during operation or in transit. It consists of a length of spring wire of such a size that its ends stretch across the inside of the pump body, provided at its centre with a loop which locates around a spigot projecting from the top of the uppermost jet cap. The loop is big enough to allow slight radial movement of the jet assembly, so that it may seat squarely on the base, but prevents the possibility of its lifting from the base.

Sommaire : On d6crit un syst6me emp6chant le d6placement de l'ensemble de l'4jecteur d'une pompe k diffusion, soft pendant le fonctionuement soft pendant le transport.

Distillation System for Recovering Spent Pumping Oils See A b s t r a c t No. : 91 / I I I

Abstract, No. and References

38/1I

Letter by P. F. Varadi

Vacu%q~b 4, Jan. 1954

66-67

39/11

40/II

Article by L. Riddiford &

R . F. Coo J. Sci. Instrum. 3I, Feb. 1954

33-36

41/1I

42/11

W. J. Scott & British Thomson- Houston Co. Ltd.

Brit. Pat. 705,160

43/11

J. Wishart & Consolidated

Vacuum Corp. U.S. Pat. 2,668,005

4 4 / I I

April , 1954 Vacuum 231 Vol. I V No. 2