APPLICATION OF FIELD VISUALIZATION TECHNIQUE TO SMM DIAGNOSTICS OF AXISYMMETRIC PLASMA

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Submitted on 1 Jan 1979

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APPLICATION OF FIELD VISUALIZATION TECHNIQUE TO SMM DIAGNOSTICS OF

AXISYMMETRIC PLASMA

V. Zatsepin, V. Lazarev, E. Tishchenko

To cite this version:

V. Zatsepin, V. Lazarev, E. Tishchenko. APPLICATION OF FIELD VISUALIZATION TECH- NIQUE TO SMM DIAGNOSTICS OF AXISYMMETRIC PLASMA. Journal de Physique Colloques, 1979, 40 (C7), pp.C7-857-C7-858. �10.1051/jphyscol:19797414�. �jpa-00219415�

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JOURNAL DE PHYSIQUE Colloque C7, supplgment au n07, Tome 40, J u i l l e t 2979, page C7- 857

APPLICATION OF F m D WSUALIZATION TECHMQUE TO SMM DIAGNOSTICS OF AHSYMMETRIC PLASMA

V.G. Zatsepin, V.B. Lazarev and E.A. Tishchenko.

I n s t i t u t e for Physical Problems, Moscow U. S . S . R.

Abstract a We present t h e development of sub- millimeter (SMM) diagnostics M r inhomogene- ous plasma under conditions of strong r e f r a - c t i o n

11-31 ,

s t a r t e d e a r l i e r by t h e l o c a l probing [4] of moving UIIF discharge [5]

.

Here is

described

the f i e l d v i s u a l i z a t i o n technique f o r quiescent plasma, based on re- g i s t r a t i o n of t h e probing f i e l d phase-amplitude d i s t r i b u t i o n .

Experiment : Investigated discharge was si- t u a t e d a t one of t h e channels of H20-laser (

%

= l l g p m ) interferometer (Fig.1).

Fig.? Scheme of experimental i n s t a l l a t i o n Laser r a d i a t i o n consisted of two ortogonally p o l a r i s e d waves I61 with frequencies ^{0 1}and

U,

,

s h i f t e d a t

&;?$$*

=33 kc. Detection of r a d i a t i o n was performed.by Ge:B photocon- ductors

[7]

Dl and D2 a t 4.2 K. Po s p l i t and rn* t h e waves 0 9 and W z we used t h e one

-

dimensional wire g r i d s PI-P4 (period 20 pm).

PI r e f l e c t e d the reference wave W 2 and pas- sed the.probing wave

ud

^$P2 was crossed with PI. Bdixers Pg, P4 were ad juated a t 45O t o polarizations. The b e a t s i g n a l used a s a reference f o r t h e phase-voltage converter [8]

was d e l i v e r e d by d e t e c t o r Dl, coupled with l a s e r by mylar s p l i t t e r MI. Plasma was i m a - ged by polyethylene l e n s h (diameter-54 mm, f o c a l length

f

⁼²⁸⁰^mm,d i s t a n s e t o plasma and. D2 equals t o

2f

⁾onto t h e h o r i z o n t a l

input s l i t (1x10 mm2) of D2. Image ssan- ning was r e a l i z e d by r o t a t i o n of the m i r - r o r M4 with angular speed, s t a b i l i z e d up t o 0.01%. Output voltage of t h e d e t e c t o r D2 was proportional f o t h e i n c i d e n t r a d i r

a t i o n intend. t y :

V ~ X ) = { X I X ) ~

~ ~ I c o s Q t

+YI-4]

with plasma

~ , ( x ) + 4 ~ ~ b ) l ~ o ~ ~ * ~ ( ~ ) ~ without plasma, -i YJx)

-''(*)

^\M(x))Io

where ff(~)/e a r e phase-

amplitude d i s t r i b u t i o n s , U- i s constant c o e f f i c i e n t , Z=U* and U

ii

l i n e a r scanning speed. This s i g n a l was transmit- t e d t o t h e AM- and phase-detectors through a s e l e c t i v e a m p l i f i e r (2). Image f i e l d phase-amplitude d i s t r i b u t i o n was r e g i s t e - re& by a storage oscilloscope and p u l e analyzer LP 4840 operating i n a 'multisca- l a r regime. Sweep of t h e s e , d e v i c e s was synhronized with mirror M4. Parameters of t h e scanning system were a s follows i Id4 r o t a t i o n period T,=600 m s , ~ = 4 7 i f / ~ , =

=5.9 mm/ms, v i s u a l i z e d region A=25 mm and number of used analyzer channels N=100.

Results : Fig.2 a , b shows t h e phase-am- plitiude d i s t r i b u t i o n s of the probing f i e l d f o r filamentary UHP discharge in D2

151

(P=3.3 a t a , W=23 ,kWt). Complex appa- r a t u s function

1~(~)1e-"'~)

( P i g . 2 ~ ) of t h e interferometer was measured vpiith a narrow sl&% in plasma plane. Phase s h i f t intmdu- ced by plasma column was equal t o *(*)=

!f(r)-Yo(%)

^;modulus of t r a n s m i t t i v i t y (curve (2) i n Fig.4) was obtained a s a r a t i o 02 t h e functions (2) and (1) in Fig.2a. Data processing w a s done by t h e nuqerical solu- t i o n [g'] of t h e convolution and ~ b e l equa- t i o n s [3] with regard t o refraction. Big.3 represents t h e plasma e l e c t r o n density p r o f i l e , c a l c u l a t e d by Abel inversion of t h e phase function

*(XI .

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19797414

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Fig.2

a)

(1) and (2)

-

^fieldamplitudes

M (XI

^and^{F ( x )} ^;

a

⁽³⁾^{and (4)}

-

^phase

distributions

K(x)

^and

?!-I%)

;

-

^plasma

phase function (1)

,

(2)-modulus

1x1

and (3)-phase

a

^ofthe apparatus function.

F i e 4 Electron

den&-@

profile

2 4 6 8

k nn

Dashed llnes display the error limits cor- responding to the absolute accuracy of the phase measurement

AY=

0.1 radn. Calcu- lated rqodulus of transmittivity for phase function *(x) is shown in Fig.4 (curve 1). Slight asymmetry of the curve is

caused by the small inclination (~0.04 radn) of the probing beam to the axis of the receiving system (see Fig.2c,curve

3).

Pia.4 Theoretical (1) and experimental (2) modulus of transmittivity The difference between two curves is due to additional radiation loss besides re- f ractive one. Its value in the experimental conditions was too small for application of the Abel inversion procedure to evaluate the radial distribution of the attenuation coefficient.

The authors are grateful to Academi- cian P.L.Kapitza for the support.of this work and would like to thank V.N.Sidorov for technical assistance.

References :

[II

L.A.Vainstein, E.A.Tishcbenko, Zh.

Tech.Fiz, 46, 11, 2271 (1976)

123

E.A.Tishchenko, L.A.Vainstein, F i z . Plasmy,

2,

1, 124 4.1977)

131 E.A.Tishchenk0, XI11 ICPIG, Berlin, Contr.papers, p.159 (1977)

[4] E.A.Tishchenko et al., XI11 ICPIG, Berlin, Contr.papers, p.161 (1977)

[5]

P.L.Kapitza, ZJ3TF,

z ,

1801 (1969)

SOV-PWS*-JE'J!P,

B , ⁹⁷³

⁽¹⁹⁷⁰⁾

,

.

[6] V.V.Zav1 yalov, G.D.Bogomolov, PisTma

. .

v ZETF, 20,

393

(1974)

[7]

V.B.Lasarev, E.A.Tishchenko, Prib.

Tech.Exper, 1979, to be published [8] V.B.La&arev, Prib.Tech.Exper,

2 , ⁸⁵

⁽¹⁹⁷⁶⁾

2 ,

1 9 1

V.G.Zatsepin, E.A.Tishchenko, A.V.

Golubev, paper at this conference

APPLICATION OF FIELD VISUALIZATION TECHNIQUE TO SMM DIAGNOSTICS OF AXISYMMETRIC PLASMA

HAL Id: jpa-00219415

https://hal.archives-ouvertes.fr/jpa-00219415