OPTIMISATION OF THE CHARACTERISTICS OF THE PLASMA FLOW FROM A DIELECTRIC CHAMBER

HAL Id: jpa-00219149

https://hal.archives-ouvertes.fr/jpa-00219149

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.

OPTIMISATION OF THE CHARACTERISTICS OF THE PLASMA FLOW FROM A DIELECTRIC

CHAMBER

I. Egorov, L. Lesnevsky, G. Popov, A. Sobol, V. Turin

To cite this version:

I. Egorov, L. Lesnevsky, G. Popov, A. Sobol, V. Turin. OPTIMISATION OF THE CHARAC-

TERISTICS OF THE PLASMA FLOW FROM A DIELECTRIC CHAMBER. Journal de Physique

Colloques, 1979, 40 (C7), pp.C7-349-C7-350. �10.1051/jphyscol:19797172�. �jpa-00219149�

JOURNAL DE PHYSIQUE CoZZoque C7, suppZBment a u n07, Tome 40, ~ u i Z Z e t 1979, page C7- 349

OPTIMISAn(M OF

ME

1.1. Egorov, L.N. Lesnevsky, G.A. Popov, A.G. Sobol and V.N. Turin.

Moscow U. S. S. R.

I n t r o d u c t i o n

It has been shown i n ^['I 1 t h a t t h e possi- b i l i t i e s f o r obtaining plasma flows w i t h high p a r t i c l e consentration by means of e r o s i v e source a r e 1imited.Such sources when used f o r technological purposes, f o r i n s t a n c e , a s l i g h t source f o r laser-pum- ping, o r f o r a c t i v e space experiments 121 a r e required t o provide heavy elements dense plasma lows (with a t o t a l p a r t i c l e number N

l o q o ) a t minimum energy input W by unity of massM.To r e a l i z e such plas- ma flows, we have chosen a source, s i m i ~ l a r t o t h a t of

33, allowing t o spend a l a r g e p a r t of t h e energy input t o increa- s e the number of sharged a n d - n e u t r a l par- t i c l e s .

For p r a c t i c a l use of such sources, i t i s important t o provide an e f f e c t i v e energy u t i l i z a t i o n ( t h e e n e r

of t h e source i a l i m i t e d toW420 and t o o b t a i n a minimum value of W/m f o r v a r i a t e d exter- n a l parameters of the source. The purpose of t h e present i n v e s t i g a t i o n s i s t o per- f e c t t h e source of impulse plasma j e t s w i t h c o n t r o l l e d parameters f o r a n optimal energy u t i l i s a t i o n .

The device and experimental method

The device

shown on Fig.1. The d i e l e c t - r i c chamber

i s made of C , F , w i t h a dis- charge channel of diameter d, and l e n g t h 1,

The anode and cathode a r e made of Cu.

The discharge i s i g n i t e d by supplying a high v o l t a g e t o t h e gap between t h e ca- thode and an intermediary e l e c t r o d e 4 from a s p e c i a l i g n i t i n g source. The model was s e t t l e d on a frame 6, including an

e l e c t r o n i c measurer of displacement and allowing momentum measurement (see calib- r a t i o n scheme on Fig.?). The optimal va- l u e s ofW/m were obtained by use of f,actor experiments C43.

According t o this method, s e v e r a l s e r i e s of experiments were provided and such a combination of t h e parameters was chosen t h a t W/m was minimum. The v a r i a t i n g f ac- t o r s were ( t h e ranges of v a r i a t i o n a r e shown i n brackets):

1. The discharge chamber l e n g t h 1, (10- -40 mm)

2. The discharge chamber diameter d, ^(2-

40 mm)

3. The i n i t i a l r e s i s t a n c e of t h e discharge c i r c u i t R, (0.5-20 -10-2 ohm)

4. The i n i t i a l inductante of t h e discharge c i r c u i t Lo(2-200*10' h)

5. The bank capacity C, (4-60 S" 1

6. The i n i t i a l bank voltage Uo (0.5-

.

2.5-103 V)

B, and La were measured by a "ringing c i r c u i t " method C,

means of a measu- r i n g bridge, t h e momentum P by a s p e c i a l momentum measurer,

t h e e r r o s i v e mass by weighting, N t h e number of discharges by a counter of l i g h t f l a s h e s . For every model 1000 pulses were prodided a t a f r e - quency of 0.5 hz. Experiments were achived i n a vacuum v e s s e l a t a pressure of 1 0 am Hg. Furthemore, t h e momentum of plasma flow and t h e plasma v e l o c i t y a s a func- t i o n of time were measured by means of a pieso-probe and a high-speed camera res- pectively.

The accuracy of a l l t h e measurement l i e s i n t h e range 2 4 5 % .

The c h a r a c t e r i s t i c s of t h e plasma flow w i t h optimal parameters

The higher described method i e l d s an op- t i m a l value of W =3.08.107 jJg f o r

m =6,13~10'~k$. It has been shown experi- mentally t h a t do and 1, a r e l i m i t e d t o

d-3 2 mm and l,-r/

mm because of t h e d i f - f i c u l t i e s of i n i t i a t i o n of long and narrow d i e l e c t r i c chambers. The a n a l i s i s of t h e

c u r r e n t and voltage oscillogram shows t a h t during T =3mks, 95% of the energy stocked i n the c a p a c i t o r

C ! , a r e sup- p l i e d t o t h e discharge, t h i s f a c t demonst- r a t i n g the high e f f i c i e n c y of t h e d i s - charge c i r c u i t . Thereby, i t should be no- t e d , t h a t the r a t e of energy supply essen- t i a l l y depends on the d i s c h a r e channel diameter. For i n s t a n c e , when Se v a r i e s from 2 t o 6 m m , the time of 95% energy supply v a r i e s from 6 t o 1.5mk.This has been explained a s the r e s u l t of t h e incre- a s i n g of &act when do decreases

5 1.

The high-speed photography i n v e s t i g a t i o n shows t h a t the plasma flow from t h e d i e l e c - t r i c chamber begins a t 2 ~ 2 m k s and ends a t 6Omks. Pig.3 gives t h e timeLdependence of the plasma flow velocity. The average mass-flow v e l o c i t y , determined from momen- tum and a c c e l e r a t e d mass measurements i s 1100 m/s, i.e. equal t o t h e flow v e l o c i t y a t T=40mhs. Fig.3 shows t h e plasma flow dinamics (1- discharge c u r r e n t ,

- ^region

of charged p a r t i c l e s flow, 3 - region of e x c i t e d and n e u t r a l p a r t i c l e s flow,

-

region of n e u t r a l p a r t i c l e s flow) Fig.4 and 5 show t h e dependency of W/m on t h e

main geometrical parameters of t h e dis- charge chamber and on the discharge c i r - c u i t parameters.

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19797172

Discussion

We have o p t i m i z e d ~ l m by a f a c t o r of 3 , a s a r e s u l t of using a planned f a c t o r expe- riment. I n d i s t i n c t i o n from analogous ex- periments on metals f I 1 when N 9 s been shown t o be l i m i t e d t o 1 0 ~ 6 1 0 i n t h e present case of Cz F4 , N has been increa-

sed up t o N

3

104?for W

20 j .

Pig.3 and 4 t o g e t h e r w i t h t h e high-speed photographies and t h e current and vol- t a g e , o s c i l l o g r a m s show t h a t when t h e chan- n e l l e n g t h 1, decreases t h e r a t i o

i n c r e a s e s due t o i n c r e a s i n g of the exter- n a l c u r r e n t s behind t h e anode and t h u s of t h e plasma flow v e l o c i t y ; f o r i./&76 t h e v a r i a t i o n ofW/m i s slow, because of t h e increasing of R& and consequently, of t h e decreasing of t h e input power.

An s i m i l a r behavior i s observed f o r w/m a s a f u n c t i o n of do: a t l a r g e diameters of t h e discharge channel we have l a r g e ex- t e r n a l c u r r e n t s and a t small diameters, the i n c r e a s i n g of Raddecreases t h e r a t e of energy supply t o d i e l e c t r i c chamber.

It can be noted thatW/m weakly depends on i,,C, and U, i n the considered range and t h i s f a c t demonstrates t h a t t h e plas- ma flow i s e s s e n t i a l l y gaso-dynarnical.

The s i g n i f i c a n t decreasing of W/m when R.

f a l l s can be explained by a diminution of t h e energy l o s s e s i n t h e discharge c i r - c u i t . The high speed photo (Fig.2) sho- wing a s t r i p e d s t r u c t u r e s i m i l a r t o t h a t

Of

e13 , demonstrates t h e d i s c r e t e cha- r a c t e r of mass supply t o the discharge.

This phenomena r e q u i r e s f u r t h e r i n v e s t i - gations.

The present a n a l y s i s allows t o recommend t h i s Kind of plasma source f o r utilisa- t i o n when plasma clouds w i t h a t o t a l par- t i c l e number of - 1020 a r e required.

References

I. Voronov I . D . , Ivanov G.V., Lesnevsky L.N. e t a l . X I 1nter.Conf .Phenomena i n Ionized Gases, CSBS, Praga, 1973.

2. POPOV G.A. e t a l . X X I Session

g u s t r i a , Insbruk, 1978

3 . AwpMa~oB A.kl.

;qp. f i ~ 1969, % 3.

4.

H~J-IMNOB B.B., YepIiosa H.A. C T & T E I C T H ~ ~ - CKMe MeTO@l IIJIaI-IMpO~aHMff

axcnepMMetiToe. M. , Hapa", 1865.

relative

w.m

1.

I

^.

^{o . ~}

^{IL.1 [ohm1}

0 500 1000 SO0

L,~O"[H]

5, yi

C , , ~ O - ~ ^[f 1

500 U)OO 1500 2000

U-

Fig. 5