PARTICLE DISTRIBUTIONS IN METAL VAPOUR-RARE GAS ARC DISCHARGES

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PARTICLE DISTRIBUTIONS IN METAL VAPOUR-RARE GAS ARC DISCHARGES

K. Jayaram, K.H. Tsui

To cite this version:

K. Jayaram, K.H. Tsui. PARTICLE DISTRIBUTIONS IN METAL VAPOUR-RARE GAS ARC DISCHARGES. Journal de Physique Colloques, 1979, 40 (C7), pp.C7-275-C7-276.

�10.1051/jphyscol:19797135�. �jpa-00219108�

JOURNAL DE PHYSIQUE CoZSoque C7, suppZdment au n07, Tome 40, JuiZZet 5979, page C7- 275

PARTICLE DISTRIBUTIONS IN METAL VAPOUR-RARE GAS ARC DISCHARGES

K. Jayaram and K.H. ~ s u i .

Institute de Fisica, U n i v ~ r s i d a d e Federa2 FZwninense, f l i t e r z i , Rio de Janeiro,24000 BraaiZ.

INTRODUCTION :

S t u d y o f g a s d i s c h a r g e s w i t h c o n t a m i n a t e d m e t a l vapour h a s g a i n e d i m p o r t a n c e b e c a u s e o f t h e i n e v i t - a b l e p r e s e n c e o f m e t a l vapour i n I n d u s t r i a l Discha- r g e d e v i c e s . Also, t h e r o l e of m e t a l vapour imp- u r i t i e s i n f u s i o n - t y p e d e v i c e s i s b e i n g i n c r e a s i n g - l y i n v e s t i g a t e d . I n c o n n e c t i o n w i t h m e t a l vapour c o n t a m i n a t e d a r c d i s c h a r g e s , i t h a s been noted by one of t h e a u t h o r s / l / t h a t s u b s t a n t i a l d i f f e r e n c e s i n t r a n s p o r t p r o p e r t i e s o f a plasma c a n a r i s e d u e t o t h e p r e s e n c e o r m e t e 1 vapour i m p u r i t i e s . Find- i n g s c f a similar n a t u r e have been r e p o r t e d e l s e - where/2,3/. F u r t h e r , i n a m o d i f i e d t y p e o f Maecker a r c t h e c o l l i s i o n c r o s s s e c t i o n of n e u t r a l metal a t o m s w i t h r a r e g a s a t o m s h a s been d e t e r m i n e d / 4 / . Arc d i s c h a r g e between m e t a l e l e c t r o d e s is a l t h o u g h b a s i c a l l y s i m p l e h a s a number of c o m p l i c a t e d mech- a n i s m s s u s t a i n i n g i t . I n o t h e r :vords; uihile mode- l l i n g a n a r c d i s c h a r g e one h a s t o c o n s i d e r ; r a d i a l / a x i a l t e m p e r a t u r e snd d e n s i t y g r a d i e n t s , d i f f u s i o n , r e c o m b i n a t i o n and even c h e m i c a l a c t i v i t i e s . The main aim o f t h i s p a p e r i s t o o f f e r a t h e o r e t i c a l e x p l a n a t i n n t o t h e e x p e r i m e n t a l l y o b s e r v e d heavy p a r t i c l e d i s t r i b u t i o n i n a r s r e g a s , m e t a l vapour a r c d i s c h a r g e .

STF3ILIZED ARC MEASUREMENTS:

A b r i e f d e s c r i p t i o n of t h e m e t a l vapour w a l l s t a b i - l i z e d a r c of s p e c i e 1 d e s i g n i s g i v e n i n /S/, B r i e f - l y i t is a s i m p l i f i e d v e r s i o n of Maecker t y p e a r c w i t h J u s t two s t a b i l i z i n g d i s c s . The arc d e v i c e i s d e s i g n e d t o b e e v a c u a t e d s o as t o f a c i l i t a t e r u n n i n g i n a n y t y p e of g a s . 1 0 , 1 5 and 2OA DC a r c s were r u n between c o p p e r e l e c t r o d e s i n a p u r e Helium medium a t e t m o s p h e r i c p r e s s u r e w i t h a s t a b i l i z i n g h o l e d i a m e t e r o f G mm. A x i a l e l e c t r i c a l g r a d i e n t s u s i n g p r o b e s , arc c u r r e n t and r a d i a l t e m p e r a t u r e d i s t r i b u t i o n s u s i n g c o p p e r s p e c t r a l l i n e s p e c t r o - graphy have been d e t e r m i n e d . O p t i c a l t h i n n e s s of e m i t t i n g r e g i o n s f o r c o p p e r l i n e s u s e d h a s been ve- r i f i e d r e s o r t i n g t o i n t e n s i t i e s w i t h i n a m u l t i p l e t t Copper v a p o u r p r e s s u r e d i s t r i b u t i o n h a s been d e t e r - mined by c o r r e a l t i n g t e m p e r a t u r e d i s t r i b u t i o n and t h e measured r e l a t i v e i n t e n s i t y of a s p e c t r a l l i n e . The d i f f e r e n t c h a r a c t e r i s t i c s and o t h e r d e t a i l s have been p u b l i s h e d e l s e w h e r e / 6 / a n d o n l y t h e r a d i a l d i s t r i b u t i o n o f copper vapour i n a 10A a r c o b t a i n e d by t h e above p r o c e d u r e is reproduced i n F i g . 1 . It may Dw.observed t h a t n e u t r a l c o p p e r atoms a p p e a r s t o p i l e - u p near t h e w a l l o f t h e d i s c h a r g e . T h i s i s n o t a p e c u l i a r i t y of t h i s e x p e r i m e n t b u t h a s been o b s e r v e d e l s e w h e r e / 7 / . With t e m p e r a t u r e a t t a i n i n g a

maximum i n t h e c e n t e r o f t h e a r c and assuming LTE t o hold(which i s probably t r u e forO.Z<T<O.8, : normalized r a d i u s ) , t h i s means t h a t t h e i o n i z e d components a r e a l s o i n f l u e n c e d by t h i s p i l e - u p e f f e c t . A t h e o r e t i c a l e x p l a n a t i o n f o r t h i s e f f e c t i s given.

.THEORY:

S i n c e t h e a r c c u r r e n t

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l=Helium,2=Copper,p=Parial pressure,n=number of p a r t i c l e s , m = m a s s , ~ = c o l l i s i o n fr e q u e n c y , Q=energy ,F=

f r i c t i o n f o r c e , X = t h e r m a l c ~ n d u c t i v i t y , ~ = v e l o c i t y and t h e s e l e a d t o

~ ( p , + p ~ ~ ~ o - - - - @ ; JZ

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$0111 in% : uz= ^-2$;/c nzw)2 &J 4

u s i n g t h e d e f i n i t i o n of A l =

';lq,

t h e p a r t i c a l p r e s s u r e s o f ~ e l i u m - a n d - 6 6 p p e r a r e g i v e n by

- P~FA ^{&. aP%R=} ~,f@$&'-

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)(;//i

R i s t h e r a d i u s o f t h e arc, where a r c t e m p e r a t u r e d r o p s t o room t e m p e r a t u r s , X1 i s t h e f i r s t z e r o of Ja and To is a x i s temperature. By i n s e r t i n g seve-

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19797135

r a l ( T , r) from e x p e r i m e n t a l l y o b t a i n e d d i s t r i b u t i o n a v a l u e o f R=2.5

9

! i u s was o b t a i n e d , By a p p l y i n g L a p l a c e ' s o p e r a t o r it i s e a s y t o approximate

v.d

R ~ ~ ~

(

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and t h e d e n s i t i e s a r e g i v e n by

S i n c e t h e a r c o p e r a t e s a t a t m o s p h e r i c p r e s s u r e Y),(op ,.

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.

A comparison of e x p e r i m e n t a l and t h e o r e t i c a l r e s u - l t s a r e made i n F i g . 2 ,

CONCWSIONS

As c a n b e s e e n from F i g . 2 , t h e t h e o r e t i c a l and ex- p e r i m e n t a l c u r v e s a g r e e o n l y q u a l i t a t i v e l y w i t h r e - g a r d t o t h e t r e n d o f t h e i r s l o p e s . P r o b a b l y b e t t e r a g r e e m e n t w i t h e x p e r i m e n t may b e o b t a i n e d by numeri c a l l y p r o c e s s i n g t h e p a r t i a l p r e s s u r e e q u a t i o n s @ ,

r a t h e r t h a n o b t q i n i n g a n a n a l y t i c a l s o l u t i o n which i n v o l v e s a d d i t i o n a l a s s u m p t i o n s . However, t h e p i l e - up e f f e c t i s e v i d e n t and t h i s o c c u r s a t t h e e x p e n s e o f Helium a c c u m u l a t i n g a t t h e a r c c e n t e r . F u r t h e r , i n o r d e r t o u n d e r s t a n d t h i s mechanism b e t t e r i t

*ill b e n a c E a s a r y t o know t h e metal v a p a u r elm- l u t i o n p r o c e s s and r e c o m b i n a t i o n mechanisms.

Acknowledgement

One of t h e a u t h o r s (KJ) t h a n k s t h e A u s t r a l i a n 3e- s e a r c h G r a n t s Committee f o r t h e PD f e l l o w s h i p and members o f t h e Plasma E n g i n e e r i n g Group of Sydney U n i v e r s i t y f o r t h e i r p a r t i c i p a t i o n and h e l p . He e l s o t h a n k s P r o f . D.'~V.George, Vice-Chancellor o f Univ. o f Newcastle f o r h i s g u i d a n c e and P r o f . J.

Uhlenbusch o f Univ. o f DUsseldorf f o r a d i s c u s s i o n on t h i s t o p i c .

R e f e r e n c e s

/1/ J A Y A R R M , I < : ~ ~ ~ . 271,217 (1974).

/2/ Sakuda e t a l : J a p . I n s t . o f E l e c . E n g r s . , P l a s - ma Research Group r e q o r t , EP-76-30,l-9 (1976).

/3/ A i r e l y , D.R. st a l ; IEEE T r a n s . on PAS, PAS-95, No. 1, P 1 (1975).

/4/ Jayaram, K. G Kane, E.L.: 1 3 t h ICPIG, Bedin, 497-498 (1979).

/5/ Miyachi, I. G Jayaram, K.: Rev. S c i . I n s t . 42, 1002 (1971).

/6/ Jayaram, K. G Kam, T.M.: C h a r l e s K o l l i n g R e s . Lab. r e p o r t , Sydney Univ., T-N P-8, 1-26(1974), s e e a l s o / 4 / a b o v e .

/7/ S c h n e i d e r , R.T. e t a l : App. S p e c t r o . Vol. 24, No. 2, 253-258 (19701, s e e a l s o Mack, J.M. : T h e s i s , Univ. F l o r i d a (1969).

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