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HAL Id: jpa-00219349

https://hal.archives-ouvertes.fr/jpa-00219349

Submitted on 1 Jan 1979

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AN EXPERIMENTAL INVESTIGATION OF THE CONTINUOUS OPTICAL DISCHARGE

D. Wróblewski, A. Cybulski, Z. Szyma_ski

To cite this version:

D. Wróblewski, A. Cybulski, Z. Szyma_ski. AN EXPERIMENTAL INVESTIGATION OF THE CONTINUOUS OPTICAL DISCHARGE. Journal de Physique Colloques, 1979, 40 (C7), pp.C7-733- C7-734. �10.1051/jphyscol:19797354�. �jpa-00219349�

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JOURNAL DE PHYSIQUE Colloque C7, suppliment au n07, Tome 40, J u i l l e t 1979, page C7- 733

AN EXPWMENTAL INVESTIGATION ff THE CONTINUOUS OPTICAL DISCHARGE

D. Wdblewski, A. Cybulski and 2. Szymafiski.

Department of Fluid Dynamics, I n s t i t u t e o f Fundamental TechnoZogicaZ Research, PoZish Academy o f Sciences, 00-049 Warszma, u l . M e t o k r z y s k a 21, Poland.

1. INTRODUCTION i n v e s t i g a t e t h e dynamics of t h e gas flow

A plasma maintained by C.W. l a s e r o s c i l l a t i o n s .

beam i s r e f f e r e d t o a s a continuous o p t i - It was found t h a t t h e l r i n g e s h i f t due c a l d i s c h a r g e /COD/. For t h e plasma main

-

t o t h e e l e c t r o n component of t h e plasma tenance focused r a d i a t i o n of p o w e r f u l l C02 w a s i n t h e range of t h e measurement accu- l a s e r s i s used. The COD was o b t a i n e d i n

r a r e g a s e s / I , 2 , 3 , 4 / and i n t h e a i r /5/.

Due t o l a r g e temperature g r a d i e n t s a c o n v e c t i v e flow i s produced i n t h e v i c i n i - t y of t h e p1asma.h i n t e r e s t i n g p r o p e r t y of t h e flow i s i t s r e g u l a r o s c i l l a t i o n w i t h t h e frequency of about 25 Hz /4/.

The aim of t h e s t u d y , t h e p r e l i m i n a r y r e s u l t s of which a r e given here,was t o in- v e s t i g a t e t h e temperature and d e n s i t y d i s - t r i b u t i o n i n t h e COD i n argoii.3pecJ--- l,rosco- py Nas used t o s t u d y t h e h o t plasma c o r e and i n t e r f e r o m e t r y f o r t h e n e u t r a l

as

de- n s i t y i n v e s t i g a t i o n i n t h e o u t e r region.

2. EXPERIMEivTAL ARRANGEMENT

The scheme of t h e experimental set-up i s shown on Fig. 1. The plasma was produ-

r a c y

-

a f r a c t i o n of a fririge.Thus, t h e i n t e r f e r o g r a m s were i n t e r p r e t e d i n t h e terms of t h e n e u t r a l d e n s i t y only.

The i n t e r f erograms e x h i b i t e d pronoun- ced v e r t i c a l symmetry a x i s and were evalu- a t e d v i a t h e Abel transformation.The re- s u l t of t h e t r a n s f o r m a t i o n i s t h e r e l a t i v e d e n s i t y d i s t r i b u t i o n and i n o r d e r t o ob- t a i n t h e a b s o l u t e v a l u e s t h e d e n s i t y must be known i n some point.The f i t t i n g a t t h e flow boundary r e s u l t s i n poor accuracy a d t h e r e f o r e i n our c a s e i t was made a t t h e plasma boundary,with t h e u s e of t h e d a t a o b t a i n e d from t h e s p e c t r o s c o p i c measure- ment s.

A s an example,the d e n s i t y d i s t r i b u -

ced i n s i d e t h e p r e s s u r e chamber i i ~ t h e f o - c u s of horizon-Lally p r o p a g a t i n g GO2-laser 8 beam.T'fie beam was focused by a s p h e r i c a l u i r r o r , i t s power was i n t h e r a n g e from 100 t o 300 iiiatts.9he p r e s s u r e o f t h e argon @ was 4 t o 6 bars.

3. IltTBRFEROUBTElrC bBA8UREMENTS Iviach-Zehnder i n t e r f e r o m e t e r w i t h a He -Ne l a s e r a s a l i g h t source was used.The p i c t u r e s 02 t h e i n t e r 2 e r o g ~ ' a m s were t a k e n

fringe image tungsfen ribbao retoruer and di~play

w i t h t h e u s e of a movie-camera.The expo- done

s u r e time was t y p i c a l l y s m a l l e r t h a n 2 ma. Fig. 1. Scheme of t h e e x p e r i m e n t a l arrangement.

The u s e of t h e movie-camera allowed t o

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19797354

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t i o n s i n t h r e e d i f f e r e n t phases of t h e o- s c i l l a t i o n s , a t t h e p r e s s u r e of 4 b a r s , a r e shown on Pig. 2.

Fig. 2. N e u t r a l d e n s i t y o s c i l l a t i o n s i n t h e COD a t t h e p r e s s u r e of 4 bars.

The frequency of t h e o s c i l l a t i o n s i s 21 Hz. The time i n t e r v a l b e t s e e n t h e frames i s 14.25 m s .

The temperature on t h e 1 x 1 0 ~ ~ cm-3 i s o d e n s e i s 2900 K.

4. SPECTROSCOPIC KEASUREMENTS

The a b s o l u t e i n t e n s i t i e s of A r I 7147a l i n e and t h e continuum a t 7182

a,

7112 1 and 4314 1 were rneasured.For t h e a b s o l u t e c a l l i b r a t i o n a t u n g s t e n r i b b o n lamp w a s used. A s i n d i c a t e d on Fig. 1 a s p h e r i c a l m i r r o r was used t o i n v e s t i g a t e t h e plasma a b s o r p t i o n a t 7147 A.The a b s o r p t i o n was found t o be n e g l i g i b l e . Other d e t a i l s of t h e arrangement a r e shown on Pig. 1.

Though t h e plasma was found t o be a- symmetric,with a t a i l i n t h e upward d i r e - c t i o n , t h e Abel i n v e r s i o n was used f o r t h e o b t a i n e d i n t e n s i t i e s and t h e n c o r r e c t i o n f a c t o r s were i n t r o d u c e d t o account f o r t h e

change of t h e shape. The temperature was determined from t h e r e s u l t i n g e m i s s i v i t i e s The r e s u l t s o b t a i n e d from t h e measurement of 7147

1

l i n e and t h e blue and r e d c o n t i - nua d i f f e r e d one from each o t h e r no more t h a n 15 p e r c e n t .

A v e r t i c a l s e c t i o n of t h e i s o t h e r m s i n t h e h o t c o r e of t h e plasma, a t t h e pre- s s u r e of 4 b a r s , i s shown on Fig. 3. The d i s p l a y e d v a l u e s r e p r e s e n t t h e average from t h e measurements made a t d i f f e r e n t wavelengt he.

5. COI'?CLUSIo~S

A complex d i a g n o s t i c s of t h e COD was performed and t h e t e m p e r a t u r e / d e n s i t y d i s - t r i b u t i o n was determined i n t h e whole r e - g i o n i n f l u e n c e d by t h e plasma presence.

The i n f l u e n c e of t h e c o n v e c t i v e flow on t h e plasma parameters was shown.The r e s u - l t s can be used a s d a t a f o r hydrodynamic c a l c u l a t i o n s of t h e gas v e l o c i t y f i e l d .

c q h e r Owm direction

-

Fig. 3. Isotherms i n t h e COD plasma a s o b t a i n e d from s p e c t r o s c o p i c measuranent

REFERENCES

1

.

N.A. Generalov e t a l . , J E T P , ~ , 1434/1971/

2. D.L.Pranzen,J.Appl.Phys.,fi,1727/1973/

3. C.D.Moody, ~ . ~ ~ ~ l . ~ h y s . ,&,2475/1975/

4. Z.Mucha e t a l . , ~ u l l . ~ c a d . ~ c i . ~ , 3 6 2 /I 977/

5. M.C.Fowler,D.C.Smith,J.Appl.Phys.

46,138/1975/

-

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