ION SOUND DISSEMINATION IN MOVING PLASMA JET

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Submitted on 1 Jan 1979

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ION SOUND DISSEMINATION IN MOVING PLASMA JET

A. Pertsev

To cite this version:

A. Pertsev. ION SOUND DISSEMINATION IN MOVING PLASMA JET. Journal de Physique Colloques, 1979, 40 (C7), pp.C7-645-C7-646. �10.1051/jphyscol:19797313�. �jpa-00219304�

JOURNAL DE PHYSIQUE ColZoque C7, suppZQment au n07, Tome 40, JuiZZet 2979, page C7- 645

ION SOUND DISSEMINATION IN MOVING PLASMA JET

A.A. Pmtsev.

Moscou, U.S. S..R.

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

Beginning from some c u r r e n t v a l u e , c r i - t i c a l d u t i e s , c h a r a c t e r i z i n by sharp i n c r e a s e of v a l u e a U / a l [I ,28

,

reached i n g a s d i s c h a r g e h i g h c u r r e n t d e v i c e s w i t h s t a t i o n a r y supply of L i

-

n e u t r a l mass flow. One of t h e main fea- t u r e s of c r i t i c a l duty i s i n t e n s i v e po- t e n t i a l o s c i l l a t i o n and plasma consent- r a t i o n e x i t a t i o n [3].

Parameters of such e x i t a t i o n , dessimi- n a t i n g i n d i s c h a r g e a r e a and i n moving plasma j e t , were considered i n t h i s work.

2. Experimental technique

I n v e s t i g a t i o n s were made i n gas d i s c h a r - ge system of c o a x i a l eometry (Fig.1).

Multi-wire cathode (ck of 1 5 m m diameter i s l o c a t e d on t h e c y l i n d r i c a l anode a x i s

( a ) (anode diameter i s 65 mm). L i

-

pours supply gasdischarge chaumber t h r o - ugh t h e cathode. Fixed h i g h frequency probe ( I ) was i n s t o l l e d n e a r t h e anode f a c e (z=O, r=R). Moving h i g h frequency probe (2) t r a v e l e d i n t h e range

-(R-50 ma) 6 r (R-50 mm);

-40 m m s 2 ~ 2 0 0 mm.

O s c i l l a t i o n parameters were measured by panorame spectrum a n a l y z e r (bandwidth 0.02-100 MHz), h i g h frequency m i l l i v o l t - meter (0.01-5.0 MHz) and analoge c o r r e l o - meter (0.05-2.0 MHz).

D i s t r i b u t i o n s of s p e c t r a l and i n t e g r a l i n t e n s i t y o s c i l l a t i o n s were s t u d i e d by spectrum a n a l y z e r and h i g h frequency m i l l i v o l t m e t e r , and time-space c o r r e l a - t i o n f u n c t i o n s were measured by t h e cor- relometer.

3 . Experimental r e s u l t s

The Fig.2 shows t h e volt-ampere charac- t e r i s t i c . The i n v e s t i g a t i o n of o s c i l l a - t i o n was c a r r i e d out a t t h e p o i n t s a , b and c.

Under c o n s t a n t f l o w h = 4 9 t h e p o i n t a corresponds w i t h Icr

,

,

.

E l e c t r i c p o t e n t i a l (-30 v ) conserning t h e anode was s u p p l i e d t o t h e measure- ment probe. Pig.3 shows t h e o s c i l l a t i o n spectrum of probe i n s a t u r a t i o n c u r r e n t . The fundamental o s c i l l a t i o n frequency i s F=0.2 MfIz.

Fig.4 shows t h e space d i s t r i b u t i o n o f i n t e g r a t e d i n t e n c i v i t y i o n s a t u r a t i o n c u r r e n t o s c i l l a t i o n on t h e moving probe.

Fig.5 shows space c o r r e l a t i o n f u n c t i o n s

of i o n s a t u r a t i o n c u r r e n t o s c i l l a t i o n s f o r t h e probes 1 and 2 along a x i s z and r a d i u s r. Fig.6 and 7 shows space-time c u r r e l a t i o n f u n c t i o n f a m i l y

K(&T)

^f

t ^{+ot) d t}

a l o n g z

(82.1

a ) i o n wave ghase v e l o c i t y along a x i s Z

-

Vz =23.10 m / ~

and along t h e r a d i u s r

vP

b ) i o n c o n c e n t r a t i o n d i s t u r b a n c e wave- l e n g t h

X Z

In a d d i t i o n t o t h a t absence of phase s h i f t between i o n c o n c e n t r a t i o n and plas- ma p o t e n t i a l waves was defined. The accom- p l i s h e d measurements show t h e a s i m u t a l

symmetry of d i s c r i b i n g waves.

4. Discussion

Measured i o n s a t u r a t i o n c u r r e n t o s c i l l a - t i o n s of probe a r e connected w i t h plasma d e n s i t y o s c i l l a t i o n s . The plasma d e n s i t y i n n e a r l y comgletely d e f i n e d by i o n com- ponent d e n s i t y , a s plasma i s h i g h l y i o n i - zed i n t h i s case.

Basing on experiment a 1 d a t a were c a l c ula- t e d wave v e c t o r s : K z r 55 _{[ m-l] ;}

Kt* U 170 [me'], i o n t e r m a l v e l o c i t y V i "-- 2.10~ m l s

,

Consequently,

ia

Assuming t h a t d i s c r i b e d waves a r e i o ~ i i c - s o n i c n a t u r e t h e damping decrement looks l i k e :

b

k k 8

= ( { ) +($)

Hence t h e l o g a r i t h m i c damping decrement may be c a l c u l a t e d a s f o l l o w s

8 = p . T =

,&

# n 0.48

Ah+./

o r

--

-

An,/ and An a r e wave amplitudes of i r e c e d i n and c o n s e c u t i v e p e r i o d s accor-

u g l y . k p e r i m e n t a l a t t e n u a t i o n t h e wave l e n g t h i s measured t o be 0.89.

Basing on t h e accomplished e v a l u a t i o n s and t h e wave motion behaviour d e f i n e d a p o s t e r i o r i , we can conclude, t h a t t h e d i s c r i b e d waves indeed a r e t h e i o n i c - -sonic waves.

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19797313

References

I . ~ O ~ O T H M K O B A

-4.

~ ~ e n . " . N l . , ~ ~ M H o c T ~ o ~ H M € ? " , 1973:~~- 2. /iOpO30B A.M aha me.

3. ~ A O T O B ~ H.H: M &p. " ~ K C ~ ~ ~ M M ~ H T ~ ~ H O ~ E c c n e n o s a H H e a a o b a r r b m I x p e a a M o B ~ J I ~ K T -

O~MHElMMYeCKOI'O C K O P M T e J I R nJIa3~b1".

ETQ,

^a. 8.

Fig.1. The e x p e r i m e n t a l d e v i c e .

p. a u-a ch.

MHr

0.2

I ^{p . b} v-a ch.

0 2 0.6 f-U

f00 300 500

Fig.2. The volt-ampere c h a r a c t e - r i s t i c of d i s c h i a g e . .v

Pig.4.The d l s t r l b u t l o n of integra- t e d i n t e n s i t y i o n i c c u r r e n t o s c i l l a t i o n i n t h e plasma jet.

Fig.3. The i o n i c c u r r e n t o s c i l l a t i o n s F i g . 5 .Space c o r r e l a t i o n f u n c t i o n of s p e c t r u m i n p o i n t s a

,

K(z, PI

K(qz)

0

I

Fig.6. The space-time c o r r e l a t i o n f u n c t i o n s of o s c l l l a t i o n S a l o n g Z-axies.

Fig.7. The space-time c o r r e l a t i o n f u n c t i o n s of o s c i l l a . t i o n s a l o n g R

-