HOLOGRAPHIC TIME-DIFFERENTIAL CINE-IMERFEROMETRY OF THE GAS DISCHARGE PLASMA

HAL Id: jpa-00219424

https://hal.archives-ouvertes.fr/jpa-00219424

Submitted on 1 Jan 1979

HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.

L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

HOLOGRAPHIC TIME-DIFFERENTIAL CINE-IMERFEROMETRY OF THE GAS

DISCHARGE PLASMA

Yu. Filenko, B. Stepanov, L. Ushakov

To cite this version:

Yu. Filenko, B. Stepanov, L. Ushakov. HOLOGRAPHIC TIME-DIFFERENTIAL CINE- IMERFEROMETRY OF THE GAS DISCHARGE PLASMA. Journal de Physique Colloques, 1979, 40 (C7), pp.C7-873-C7-874. �10.1051/jphyscol:19797422�. �jpa-00219424�

JOURNAL DE PHYSIQUE CoZZoque C7, suppze'rnent au n07, Tome 40, JuiZZet 1979, page C7- 873

HOLOGRAPHIC TIME-DIFFERENTIAL CINE-INTEFWEROMETRY ff THE GAS DISCHARGE PLASMA

Yu. I. Filenko, B.M. Stepanov and L.S. Ushakov.

Gosstandard, U. S. S . R.

The methods of obtaining holographic t i m e - d i f f e r e n t i a l cine-interfesograms of t h e e l e c t r i c discharge i n t h e a i r a r e con- sidered. These a r e t h e i m p r ~ v e d methods of those described i n 1 , 2

.

idea of t h e s e new methods i s t h a t t h e re- f e r e n c e beam is passing t o a photographic p l a t e through an opaque mask (Fig.1) with a p e r t u r e s placed along t h e s p i r a l s ,

Fig.l. The mask,

Khen r o t a t i n g such a mask some a r e a s of t h e photographic p l a t e a r e opened twice t o p u l s e reference r a d i a t i o n , t h e time between exposures being multiple t h e ra- d i a t i o n puLse r e p e t i t i o n period. This mul- t i p l i c i t y depends on t h e area p o s i t i o n of t h e photographic p l a t e , which enables t h e comparison interferograms of any p a i r of a l l recorded discharge phases t o be obta- ined i n one recording. The number of t h e discharge phases i s equal t o t h a t of t h e l i g h t r a d i a t i o n p u l s e s , whose r e p e t i t i o n r a t e must agree with %he mask r o t a t i o n speed.

The block-diagram o f t h e experimenf;~

made with t h e use of t h e s o v i e t UIG-1M ho- lographic instrument and t h e above methods i s shown i n Fig.20

Pig.2. The block-diagram of t h e experi- ment s

.

The ruby l a s e r 1,3,5 was provided with an acousto-optical modulator 2 t o generate t h e required p u l s e t r a i n s . The sound wa- ve was excited

ih

symmetrical transducers. Applying about 10 kHz i n t e r r u p t i o n frequency t o t h e bri- ving acoustic s i g n a l and choose t h e aP- p r o p r i a t e pumping l e v e l t h e s t a b l e genera- t i o n of 5 g i a n t p u l s e t r a i n was obtained.

The r o t a t i o n speed of t h e disk-mask 6 i n the reference beam was 40 000 r.p.8. The

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19797422

reference beam passed through t h e mask M i c e r e f l e c t i n g from t h e mirror 1 placed behind t h e mask*

IQ agree t h e mask r o t a t i o n speed with t h e generation pulse r e p e t i t i o n r a t e a He-Ne l a s e r 17 was used, whose beam modu- l a t e d by t h e same mask was f a l l i n g onto t h e photodiode 16. The s i g n a l s from t h e photodiode and t h e driving frequency gene- r a t o r 14 were d i r e c t e d t o t h e two-beam os- c i l l o g r a p h 15. Four i n t e r f erograms of t h e successive phases o f t h e a i r discharge between t h e electrodes 9 and a l l t h e time- d i f f e r e n t i a l interferograms of these di- scharge phases were recorded ... 9n t h e same photographic p l a t e 11.

The d i s t r i b u t i o n s of t h e plasma re- f r a c t i o n f a c t o r were evaluated i n t h e a x i a l ppproximation by computer processing.

These d i s t r i b u t i o n s corresponding t o 140,~s and 240 ps from t h e moment of i n i t i a t i o n a r e shown i n Fig. 3a,b. There a r e a l s o gi- ven t h e e r r o r i n t e r v a l s whose values were caused by t h e e r r o r s of d a t a obtaining and processing. I n P i g . 3 ~ t h e s o l i d l i n e denotes t h e changing of t h e r e f r e c t i o n f a c t o r between phase A and B obtained by s u b t r a c t i n g A curve from B curve. I n t h i s case t h e e r r o r i n t e r v a l of t h i s dependen- ce t u r n s out t o be so l a r g e t h a t t h e zero l i n e n (r)-n (r)=O i s included i n t o it, with such a processing one cannot be su- r e whether t h e change of n took place a t a l l . The r e s u l t s of t h e t i m e - d i f f e r e n t i a l comparison interferogram of A and B pha- s e s i s shown by a dashed l i n e i n F i g . 3 ~ .

"..

Fig. 3.

he

The e r r o r of n c a l c u l a t i o n was I ~ O , which allowed q u a n t i t a t i v e s t u d i e s of t h e t r a n s i t i o n A B.

It should a l s o be pointed out t h a t due t o t h e t i m e - d i f f e r e n t i a l interferometry method t h e range of n change i s widened t o l a r g e r values. The nwnber of f r i n g e s

acceptable f o r t h e q u a n t i t a t i v e proces- s i n g i s l i m i t e d by t h e obtained space re- solution. When comparing successive pha- s e s with t h e i n i t i a l phase % h i s number determines t h e deviation of t h e object p r o p e r t i e s from t h e i n i t i a l ones. However t h e t i m e - d i f f e r e n t i a l interferometry me- thods allow such number of f r i n g e s f o r each comparison interferogram of t h e pha- s e successive p a i r s r e s u l t i n g i n t h e men- ti oned broadening.

References

1. J.CrBinder,Nouv.Rev.d'0pt.Appl.,v.2,

N*3,1971.

2. P.Hariharan,Z.S.Hegedus,Opt~commm., v*9,N*2,1973*