ULTRAVIOLET RADIATION OF THE SURFACE DISCHARGE IS A PREIONIZER OF HIGH PRESSURE ATOMIC-MOLECULAR IMPURITIES

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ULTRAVIOLET RADIATION OF THE SURFACE DISCHARGE IS A PREIONIZER OF HIGH PRESSURE ATOMIC-MOLECULAR IMPURITIES

A. Belyanko, N. Lipatov, P. Pashinin, A. Prokhorov

To cite this version:

A. Belyanko, N. Lipatov, P. Pashinin, A. Prokhorov. ULTRAVIOLET RADIATION OF THE SUR- FACE DISCHARGE IS A PREIONIZER OF HIGH PRESSURE ATOMIC-MOLECULAR IMPURI- TIES. Journal de Physique Colloques, 1979, 40 (C7), pp.C7-505-C7-506. �10.1051/jphyscol:19797245�.

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JOURNAL DE PHYSIQUE CoZZoque C7, suppZ&melzt au n07, Tome 40, JuiZZet 1979, page C7- 505

UCTRAVIOLET RADIATION W THE SURFACE DISCHARGE IS A PREIOMZER OF HIGH PRESSURE ATOMIC-MOLECULAR IMPURITIES

A.E. Belyanko, N.I. Lipatov, P.P. Pashinin and A.M. Prokhorov.

P. N. Lebedev PhgsicaZ I n s t i t u t e of the U. S. S . R. Academy of Sciences, Moscow, U.S.S. R.

The r e a u l t s a r e concerned with t h e

perimental i n v e s t i g a t i o n of preionise d r a d i a t i o n of the surface discharges pro- pagating over t h e substances with d i f fe- r e n t values of d i e l e c t r i c permeability onto atomic..loolecular high pressure gas intpurit i e

.

The i n t e r e s t t o t h e s u r f a c e dischar- ges r e s u l t s from t h e i r following proper- t i e s : h i & o p t i c a l output, high power and considerable discharge aperture, comparan t i v e l y ordinarg b r i e t temperature contr- ol,

s p e c i f i c c h a r a c t e r of t h e discharge i n t e r v a l breakdown due t o s t r o n g gradi- e n t s t o t h e e l e c t r i c f i e l d on an i n t e r f a a e of d i e l e c g r i c gas allow8 t o make an agreement between discharge i n t e r v a l and accumulation wit@out d i f f i c u l t i e s .

a r e s u l t , t h e energy c o n t r i b u t i o n r a t e r a p i d l y i n c r e a s e s and, a s i n consequence,

discharge plaama by t h e i ~ radPative p r o p e r t i e s becomes c l o s e t o a black body with

surface temperature 5 0 0 0 0 ~ ~ .

It is

shown t h a t , a s an u l t r a v i o l e t p r e i o n i s a t i o n source of t h e a t omic-mole- c u l a r gas i m p u r i t i e s it i s appropriate t o use over t h e substances t h e discharges with a high value /

of d i e l e c t r i c

permeability, sag, ceramics, I n t h i s case ,

an e f f i c i e n c y of t h e s u r f a c e discharge, as a p r e i o n i z e r of gas impurity,

oreat-, e s a g r e a t number of phot oelectrons i s much b e t t e r t h a n another o p t i c a l sources,

say, t h e open sparks.

compositions and pressure v a r i a t i o n s of the surrounding

make it p o s s i b l e t o c o n t r o l e f f e c t i v e - l y a s p e c t r a l composition and s u r f a c e d i s - charge r a d i a t i o n c h a r a c t e r t h a t opens

optimal p o s s i b i l i t y (i.e. having

expenditure of energy) f o r

medium pho- t o i o n i z a t i o n o r $or p h o t o i n i t i a t i o n of gas reactione. The former opens theT'good chan- c e s f o r i n v e s t i g a t i o n s of d i f f e r e n t micro-

I

scopic processes such a e recombination, energy exchange between d i f f e r e n t compo- n e n t s of gas i m p u r i t i e s where it is easy t o develop

nonequilibrium thenno-Qnamic passing

c u r r e n t through a photoionised gas.

I n t h e process of i n v e s t i g a t i o n of plasma discharge o p t i c a l r a d i a t i o n t h e new, unknown previously, f e a t u r e s of t h e

pulse behaviour were observed

t h e ceramics eurface.

selfdamage' of t h e overteneed eurfsoe i n t e r v a l favoured t h e short-closed l i n e c r e a t i o n f i l l e d by a

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19797245

d i e l e c t r i c w i t h

high value of d i e l e c t - r i c permeability. The n o n l i n e a r l i n e los- e s caused

dependence of plasma f i l a - ment r e s i s t e n c e of t h e discharge c u r r e n t , under s u i t a b l e conditions promoted a f o r - mation of s h o r t electromagagic wave w i t h t h e f r o n t i r r a d i a t i o n a s h o r t / 30nseci!

pulse of hard u l t r a v i o l e t radiation.

t h e time s c a l e t h i s pulse

followed by a discharge a r c s t a g e i n t h e developing of which one r e a l i z e s

main energy contr- i b u t i o n i n t o a discharge

t h e o p t i c a l discharge r a d i a t i o n pulse

shaped with a d u r a t i o n on the order of magnitude ex- ceeding a n u l t r a v i o l e t glow of the shock electromagnetic wave front.

A s

a r e s u l t of

combined e f f e c t of t h e shock wave f r o n t r a d i a t i o n and t h a t of t h e

s t a g e of a discharge t h e cha- r a c t e r i s t i c values of photoelectron densi- t y

d i f f e r e n t gas i m p u r i t i e s were

The energy i n preioniz;er was

Photoelectrons were r e g i s t e r e d by

probe-Earadey c y l i n d e r whose c o n s t r u c t i v e f e a t u r e s made

possible t o i n v e s t i g a t e a space photoelectron d i s t r i b u t i o n basing of which one can conclude on

mechanism of photoionized process.

f o r example, i n molecular i m p u r i t i e s C02:N2:He of d i f - f e r e n t p a r b i a l composition, a propagation of 17001 u l t r a v i o l e t r a d i a t i o n which ape c o n t r o l l e d by

molecules, t h e phoc t o e l e c t r o n s arranged i n 2-6cm out of pre- i o n i z a t i o n sources were conducted i n con-

sequence of two-step e x c i t a t i o n procees, when two l i g h t quanta molecule absorption r e s u l t s i n photoelectron developing.

A

d i s t i n c t i v e f e a t u r e of t h e surface discharge operation a s a preionizer com- pared, f o r example, t o t h e open sparks

t h a t a t gas pressure over

t o r r the photoelectron density

some gases

N2/

independent of pressure while i n

case of t h e open sparks the photoelectron concentration f a l l s r a p i d l y with gas pressure growth.

This s p e c i f i c p e c u l i a r i t y r e s u l t s from i n c r e a s i n g of o p t i c a l output of t h e surface discharge, t h e more t h e pressure of surrounding gas. Due t o t h i s f a c t , f o r high pressure impurity i o n i z a t i o n

more appropriate t o use t h e sur- f ace discharges.

A

designed q u a l i t a t i v e model of t h e

process i n v e s t i g a t e d explaines t h e ob-

t a i n e d experimental r e s u l t s on t h e

of which a possible photoionization u l t -

r a v i o l e t pumping

a discharge s u r f a c e

r a d i a t i o n of r a p i d l y recombined~omic

hydrogen plasma i s discussed.