THE INVESTIGATION OF PHYSICAL PROPERTIES OF THE NEAR ELECTRODE REGION OF HF DISCHARGE

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THE INVESTIGATION OF PHYSICAL PROPERTIES OF THE NEAR ELECTRODE REGION OF HF

DISCHARGE

A. Kuzovnikov, V. Kovalevskii, V. Savinov, V.G. Yakunin

To cite this version:

A. Kuzovnikov, V. Kovalevskii, V. Savinov, V.G. Yakunin. THE INVESTIGATION OF PHYSICAL

PROPERTIES OF THE NEAR ELECTRODE REGION OF HF DISCHARGE. Journal de Physique

Colloques, 1979, 40 (C7), pp.C7-459-C7-460. �10.1051/jphyscol:19797223�. �jpa-00219205�

JOURNAL DE PHYSIQUE CoZZoque C7, suppZ6ment au n07, Tome 40, ~ u i Z Z e t 1979, p a g e , ~ 7 - 459

THE INVESTIGATION OF PHYSICAL PROPERTIES OF THE NEAR ELECTRODE REGION OF H- DISCHARGE

A.A. Kuzovnikov, V.L. Kovalevskii, V.P. Savinov and V.G. Yakunin.

Department o f Physics, Moscow S t a t e U n i v e r s i t y , U.S.S.R.

This paper i s devoted t o the investiga- t i o n of near electrode region

(N=)

of High frequency d i ~ c h a r ~ e ( ~ ~ ~ ) o f E-type. Up t o now no s a t i s f a c t o r y study has been made

of the physical mechanism of such HFD, whose c h a r a c t e r i s t i c property i s the occu- rence of the DC e l e c t r i c f i e l d s , caused by HF-detectionrl], and the streams of f a s t electrons[2]in the

NW.

_HFD of the radiofrequency range i n the

He, Ne

and At- has been investigated. The discharge was produced i n tubes of 40 mm diameter with f l a t external and i n t e r n a l electrodes. To investigate the N I B a study waps made of the s p a t i a l d i s t r i b u t i o n of i n t e n s i t y o f i n t e g r a l luminescenceI(~) and some s p e c t r a l linesjrh(~). A comparative study was made of

I(%)

andIA(%)for HFD and the d i r e c t cur- r e n t glow discharge (DCGD)

RBUIU!S. 1)The distributionI(x)in a sum- metrical RFD i n He(p=o,25 t o r r , HF volta- gev, =400v, frequency f = 4Mc) with exter- n a l e l e ~ t ~ d e S i s shorn i n Fig.1.

3

^The

dependence o i I ( ~ ) i n the NJB of HFD i n N e (p=0,25 t o r r , f= 2Mc) on

V,

i s i l l u s t r a - t e d i n Fig.2, where 1-100v, 2-300v, 3-600v,

.

4-800v, 5-1 0 0 0 ~ ) .

Z)

Fie.3 shows the spect- r a l l i n e Ar-r4052i distributionlA(din the NEE2 of XFD and i n the cathode region of DCGD i n the sane discharge tube

(AY ,

p=0,3 t o r r , f = 1,5Mc,V =700v i n both cases).

3

^It is found t h a t atVp 4000 the d i s t r i b u t i o n ~ I ( ~ ) i n HFD and DCGD are ana- lo@;ous and are equally dependent on the voltage supporting the discharge.

3

^he

dependence o f I ( ~ ) i n HFD i n He(p=o,25 t o r r ,

f = 4Mc

,x

^=5OOv) on the electrode material i s i l l u s t r a t e d i n Fig.4. a ~ h e dependence of I()oon the kind of gas a t the fixed re-

gime of HFD ( ~ ~ 0 . 2 t o r r , f = Z M C , ~ =500v) i n the discharge tube with external e l e c t - rodes i s shown i n Fig.5.

DISCUSSION. A s shown i n Fig.1

,I(%)

^{i n HFD}

contains i n the neighbourhood of the elec- trode a l l the inhomogeneities of lumines- cence c h a r a c t e r i s t i c of the cathode f a l l region DCGD. The homogeneous region i n the centre has the appearance of a positive column. We see i n Fig.2 t h a t the mentioned d i s t r i b u t i o n

I(x)

^{i n HFD} i s formed gradually with the increase of

VN .

^{A t} low voltages

(V,<

^300v)I(~) has i t s maximum i n the cent- r e of the discharge gag, f a l l i n g monoto- nously t o the electrodes without any cha- r a c t e r i s t i c s t r u c t v r e

~ ~ T ~ % ) c c G D .

^{The mo-}

notonous f a l l of luminescence i n t e n s i t y from the centre t o the electrodes corres- ponds t o the d i s t r i b u t i o n I(%)in the q - t n e AF discharge. In this discharge the balan- ce of charged p a r t i c l e s i s due t o the vo- lume i o n i i a t i o n by electrons whose ener- g i e s are determined by the i n t e n s i t y value of HR f i e l d a t the p a r t i c u l a r point of space, and by the diffusion departure of charged p a r t i c l e s onto the walls and elec- trodes. A s shown i n Pig.3, the distribu- t i o n L ( 3 f o r the spectral lineAr14052i (as well asI()o) in

HPD

a t v , ~ 300v is analogous to&[.) i n DCGD, t h a t i s , i n a

?-type discharge, where %he emission pro- cesses on the electrode and the electrone avalanche i n the NNR are the determining f a c t o r s .

In

connection with the coinci- denoe o f I ( ~ ) a n d ~ ~ ( ) O i n the NER of RPD and DCGD, one may draw analogy between the luminescing region of both discharges.

It i s natural t o suggest that: due t o its physical properties the

fa

luminescence

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19797223

maximum region nearest t o the electrode, i n HF'D i s analogous t o the "cathode iu- minescence"of DCGD it. i s a l s o reasonable t o consider theZdnext t o the electrode maximum in the d i s t r i b u t i o n

ICX)

^of

^HFD

as an analogue of the "negative lumines- cence" region of DCGD. A s knownC33, mo- ving from the cathode t o the "cathode lu- minescence" region of DCGD, electrons asquire energy close t o the

1 sf

excitation potential, but lower than the gasioniza- t i o n potential. fEhus one may suggest t h a t the luminescence i n t e n s i t y of the "cat- hode luminescence" region i s proportional t o the number of electrons emitted from the cathode. Then, the considerable inc- rease of the amplitude of the 1-lumines- sf cence m a x i m u m with the increase of

shown i n Fig.2, indicates the i n t e n s i f i - cation of emission processes. The distri- bution

I C Y )

^shown

.

. i n Fig. 4,5 support

%,his assumption. Actually, according t o Fig. 4 the luminescence i n t e n s i t y of the quartz ( ~ i ) electrode i n the Nl%l is higher than t h a t i n the neighbourhood of the Ti-electrode. The emission a b i l i t y of S I

is higher t h a t of T i . The emission inten- s i t y is determined by the choice of the p a i r "the gas

-

the electrode material".

According t o the investigation[4], the combination " A r

-

glass" produces the lowest emission whenit i s compared with other p a i r s of "an i n e r t gas

-

glass".

Fig.

5

shows t h a t a t s i m i l a r regimes of RPD i n Ar t h e

fSf

~uminescence maximum is

~ o n s i d e r a b l y weaker than it i s i n Ne.

These r e s u l t s show t h a t

i n

such HFD

-

processes play an important part.

The coincidence of

T(X)

^andIA

(XI

^{i n KPD and}

DCGD shows t h a t the charaater of motion of the eleatrons i n the NlEt i s t h e same f o r theee discharges. Hence, i n the NSl of t h e

EIFD

concerned the electrons must perform a unidirectional r a t h e r than a

vibrational motion from the electrode t o the discharge center. T h i s i e p ~ s s i b l e , if

i n

the NlEt the action w i l l be perfo- med by the e l e c t r i c f i e l d whose direa- t i o n is conetant rather than variable.

According t o the mechamism of HF

-

^detec-

t i o n [ ~ ] , the time variation of the elec- trode p o t e n t i a l r e l a t i v e t o the space po- t e n t i a l of plasma w i l l represent unipolar negative pulses. Thise pulses must appear during negative one-half periods of HI?

f i e l d . When the one-half periods of HJf f i e l d are positive, the electrode poten- t i a l must have a s m a l l value of the order of the "floating" p o t e n t i a l of the disc- harge plasma. Thus, the properties of the investigated stationary HFD are s i m i l a r t o the properties of the pulsed glawing d i r e c t current discharge.

References.

[If Butler H,S., Kino G.S., Phys. Fluids, V. 6 , N. 9, (1963)l

C2]~uzovnikov A.A., Savinov V.P., Radio- technika and Electronika, V. 18, N. 4,

(1973)

133-81

^A., Ionized Gases, OrrPord,(1955).

C41Batanov G.M., Petrov

N.N.,

FTT, V. 1,

N.

129 (1959).