EXPERIMENTAL INVESTIGATION OF THE ELECTRICAL AND HEAT CONDUCTIVITIES OF ALKALI DENSE PLASMAS

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EXPERIMENTAL INVESTIGATION OF THE ELECTRICAL AND HEAT CONDUCTIVITIES OF

ALKALI DENSE PLASMAS

V. Vorobiov, P. Kulik, A. Pallo, A. Rakitin, E. Rozanov, V. Riabyi

To cite this version:

V. Vorobiov, P. Kulik, A. Pallo, A. Rakitin, E. Rozanov, et al.. EXPERIMENTAL INVESTIGATION OF THE ELECTRICAL AND HEAT CONDUCTIVITIES OF ALKALI DENSE PLASMAS. Journal de Physique Colloques, 1979, 40 (C7), pp.C7-693-C7-694. �10.1051/jphyscol:19797336�. �jpa-00219329�

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JOURNAL DE PHYSIQUE CoZZoque C7, suppZ6ment n07, Tome 40, JuiZZet 1979, page C7- 693

EXPERIMENTAL INYESnGATION OF THE ELECTRICAL AND HEAT C OOF ALKALI DENSE ~ PLASMAS ~ ~

V.V. Vorobiov, P.P. Kulik, A.V. Pallo, A.A. Rakitin, E.K. Rozanov and V.A. Riabyi.

Moscow, U.S.S.R.

This work i s a f u r t h e r development of t h e i n v e s t i g a t i o n s [I ,2] of a l k a l i dense highly non-ideal plasma generated by pul- sed high pressure (up t o 1000 atm) a r c discharge s t a b i l i z e d by a transparent c a p i l l a r y .

The experimental device (Fig.1) includes quartz o r g l a s s c a p i l l a r y between nozzle and cup e l e c t r o d e s , t h e l a s t being made of t a n t a l and f i l l e d by s o l i d a l k a l i me- t a l . These elements a r e s e t i n t o an argon high pressure v e s s e l t o unload t h e c a p i l l a r y from t h e i n n e r pressure and so prevent i t s d i s t r u c t i o n during o r j u s t a f t e r t h e discharge. Two tungsten f l o a - t i n g probes allow t o measure t h e e l e c t r i - c a l f i e l d E= & u / A ~ of t h e a r c column ( A U being the p o t e l i t i a l drop between t h e probes, l o c a t e d at t h e d i s t a n c e )

.

The a r c e l e c t r o d e s a r e C o ~ e C t e d t o a c a p a c i t o r bank through an inductor, The discharge i s t r i g g e r e d e i t h e r by an in- t e r e l l e c t r o d e wire ( ~ i g . 1 ) o r by meana of a s h o r t a u x i l l i a r y discharge between t h e cup e l e c t r o d e and an a d d i t i o n a l elec- trode. For a c a p i l l a r y of diameter

-

²^mm

and l e n g t h

-

^{1 5}^mm t h e c u r r e c t amplitude reaches I k A and t h e discharge l a s t s

- 2 0 msec. The argon d e t e n t i o n volume o u t s i d e of t h e c a p i l l a r y has been increa- sed u t o -. 70 cm (compared t o 4 cm i n ['l-3f). This measure guarantees t h e discharge plasma pressure t o be e s s e n t i a l l y constant and equal t o i n i t i a l argon s t a - t i c pressure i n t h e vessel.

I n t h i s work C s , K, Na, Li and 78% K

+

22% Na e u t e c t i c a l l o y (weight 74%) have been i n v e s t i g a t e d . The pressure l e v e l s adopted a r e 100, 300 and 1000 atm ( f o r Cs t h e intermediate pressure i s 250 atm).

Usin dual t r a c e storage o s c i l l o s c o p e , a U 71) dependences have been recorded, which f o r known probe separations

~e

^=1.5-4 ^mm can e a s i l y be transformed i n t o EX-characteristics, These measure- ments correspond t o time sequences when plasma uniformly f i l l s t h e i n t e r p r o b e space. This f a c t has been confirmed by speed f i l m i n g of t h e a r c column through a window (Fig.?).

S p e c i a l experiments using a f l o a t i n g probe t e c b n i ue have r e i n f o r c e d t h e argu- ments of 91-31 f o r plasma p u r i t y . I n p a r t i c u l a r a l o n g i t u d i n a l a r r a y of probes, t h a t proved t h e plasma p o t e n t i a l v a r i a t i o n along t h e a r c column t o be li- near, have shown t h a t the t o t a l e l e c t r o - de p o t e n t i a l drop i s l o c a l i z e d a t t h e cup e l e c t r o d e a t any a r c p o l a r i t y . This

p o t e n t i a l drop turned out t o be more i n magnitude a t t h e normal a r c p o l a r i t y when t h e cup e l e c t r o d e i s a cathode.

Such p o l a r i t y l e d t o more i n t e n s i v e a l - k a l i metal evaporation and b e t t e r ven- t i l a t i o n of t h e discharge space t h a n i n t h e case of inverse p o l a r i t y , so t h e pre- s e n t experiments were c a r r i e d out a t n o r ma1 a r c p o l a r i t y .

Experimental EI-data were f u r t h e r t r a n s - formed i n t o i s o b a r s ^T [3] where

% r e R-capillary r a d i u s , x -Stephan- -Boltzmann constant, T,, -outer s u r f ace temperature of t h e a r c column.

following^ l23 experimental dependences d (T) and A ( T ) have been obtained by solving the f u l l inverse problem of heat conductivity based on t h e ~ q u a t i o n s [2]:

R

a = z g J

^{$ Z ~ Z} ⁽²⁾

where ( 1 ) i s tbOe r e s u l t of i n t e g r a t i o n of t h e Elenbaas-Eeller equation f o r t h e present conditions and (2) i s t h e expre- s s i o n f o r t h e average e l e c t r i c a l conduc- t i v i t y . Dependences 6 (T) and . A (T) have been found by means of a numerical v a r i a t i o n a l method using a modified ,Monte- -Carlo technique.

The r e s u l t s of the present i n v e s t i g a t i o n a r e shown on Fig.2 f o r 6 (T,P) and i n t h e Table f o r A (T,P)

.

Within t h e experimental e r r o r s t h e s e d a t a reasonably agree w i t h t h e previous r e s u l t s fl] f o r

d (T,P) and contain t h e following new information: 1 ) d (T) f o r P=100 atm;

2 ) 6 (9) f o r T 3 3000 K a t P=1000 atm;

3 ) h (T,P).

References

1. B a r o l s k i i S.G. ? Yermokhin N.V., Kova- l i o v B.M., Kulik P.P., R i a b i i V.A.

Proc.XIIth ICPIG, Eindhoven, 7975,

p.181.

2. k u l i k ~ P.P., Rozanov E.K., R i a b i i V.A.

Proc .XIIIth ICPIG Berlin 1977, p.585, 3. 6a o J I ~ c K A ~ ~ C.F.,

E?

^MOXHH

d . ~ .

IlyJIHK

n.8.

^PKCM ^B.A.

^{~ B T ,}

^1976,fi,~^4,

c

.?of!.

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19797336

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TO EZECTRICAL SOURCE

100

-

FIG .2a P=lOO atm

FIG.2b -300 atm

(Ca :250 atm)

1 .Y !F. 1 0-?K

2 0 ' ^I

200

- 6 ,oh,-!

^QP-'

loo -

P=lOOO a*

..---

^/

50

-

" M e - - - -

/ /

T

-

ⁱ0-?K

----A'

x

^b ^T%,

r/m.r

^;^[TI

=lo%

(with aeourad of the o d e * of factor 2)