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Submitted on 1 Jan 1979
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IONIZATION OF GASES IN STRONG ELECTROMAGNETIC FIELDS
S. Arutyunyan, I. Gekker, D. Karfidov, A. Ruchadze
To cite this version:
S. Arutyunyan, I. Gekker, D. Karfidov, A. Ruchadze. IONIZATION OF GASES IN STRONG ELECTROMAGNETIC FIELDS. Journal de Physique Colloques, 1979, 40 (C7), pp.C7-219-C7-220.
�10.1051/jphyscol:19797108�. �jpa-00219078�
JOURNAL DE PHYSIQUE CoZZoque C7, suppZ6ment au n07, Tome 40, JuiZZet 1979, page C7- 219
IONIZATION OF GASES I N STRONG ELECTROMAGNETIC FIELDS
S.G. Arutyunyan, I.R. Gekker, D.M. Karfidov and A.A. Ruchadze.
Lebedev ~ h ~ s i e a 2 I n s t i t u t e of t h e U . S . S . R. Academy of Sciences, PZasma Physics Laboratory, Moscow, U . S. S. R. .
AbstracttA qualitative theory of gas bre- akdown had been developed f o r the conditi-.
ons when the average energy of electron oscillatibns i n an al8ernating f i e l d go &
= e$$$3axceeds the ion& ation potential of atoms 1,The dependence of the grodh r a t s of ionization
8
on &o(E.
=10~-10~eV) i s presented.Experimental investigations on the development of microwae breakdown i n belitqargon and air have beea conduc- t e d . 4 the region of E0/% ml.540 -8 -8, I O - ? V . S / ~ ~ (&SO.?-300s~) and pressures p=5.10~-10-3torr;~ a t i s f a o t o ~ ; ~ agreemeat between calculated and ~tgperiment9 depen- dearces has been observed f o rIPtroduc%ionr & most theoretical works fos weak f i e l d s ( f o ~ aemple, see /1,2/) it i s assumed t h a t e~k!J!g~I where k!C, i s the average energy of electrons (t&aca- ture).The theory of gas breakdown based, on t h e model of marage eleotron yields re- sults close t o those obtained within t h e framework of kinetic the0ry.b /3/, an at- t e m p t w a s made t o construct a.kinetic the- ory of gas breakdown f o r arbitrary values of €,,in particular,for€dI.In this case ene cannot consider solution of the kine- t i c equation by expansion of spherical functions sufficiently jwtified.nl contra- d i s t a c t i o n t o this,here we considered the quesfion of gas ionization fork771 f r o m t h e standpoiPt of the model of merage electron, cold a eonrpsrison i s made w i t h erx- p e r i m a t al data.
Theor~f: The frequency of trausport collisi- ons of electrons i s m u o h l e s s than frequ-
ency of ionization collisions in a sOrong ectxic f i e l d (&ojvtOI) averaged over pe- od of oscillations.~hercr~ore, t h e average r, dom en&?= of a~ electron gas turms out. to be mall in 001~gaf.1900. with &,until
the gas becomes weakly ioniz;ed.Under such conditions we s h a l l take into accolme on- l y induced motion of electrons in the f i e l d ~ = ~ ~ s i n c u , t
vlCI=
~ r , c ( ~ i n w ~ t -S(nw.a)(~ 0where%=
@
.we note t h a t the formula e2 E~= o ~valid only s f o r &'>>S?& electron
ym cvo
can ionize an atom only i f v ~ ~ = ~ . s I P c ~
'&77%, secondary electrons a e poduced practically a t arbitrary phases.Aftar se- veral collisions electrons may be assumed t o have uniform phase distributions.
The growth r a t e of ionization )( cssl be determines Oom
-
dfle = nen, Ci
v =
n e ;y7 s - (2)
whare ne and no are densities of elecffons and atoms, i s t h e cross section atom ioniz ation by electron impact .Averaging over the period of electron oscillations.
iP t h e field as well as over Snitial pha-
ses of elgctron production,using the ear-, pression f o r
4
(7Y)fkom the Born @proxima-tion
G(v)
r $ En (3 1we obtain,within the limits of large
&,
.Y==
nodE ten + (41
!Phe calculatpn of
8
for more exact va- lues of5
(~)t;aken from cmrperimen-b /4/ w a s performed on a computer .In Big.1, the cal- culated d~pemdence j ( f ~ $ h ~ f o r helium i s presented.1t csol be s e m t h a t a t firstr/nO increases,reaching a maximum
gm
&== 1 . 9 . 1 0 ~ c m - ~ . s ~ a t Ee=300eVythen,it be- gins t o deorease,agpxoadxbg the asympto- t i c depadearce /dotted line/,!Phe coeffici- ent d. w a s chosen so t h a t the curves coin- cide txt E,
=lo3
e~ rlkperim~t:UsuaIly errrperimarts (see, f or errrample,/l,2/) have be= conduc.t.ed In. re- l a t i v e l y weak fields,wha the characteris- t i c pacaneear of breakdown of low p r e s s u ~
r e s Eo/~.did not erceed 10%. s/cm (whe-
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19797108
reby &<I).Here, we have studied the develop- ment o f . avalaches i n a aicrowave . field a t E o / i = l -5 .I0 -8 -8 .IO-~V. s/cm -1-300eV) i n helium, argon a d &.The i n s t a l a t i o n c o ~ s i s t e d of a Q20cn circular w w e e d e o$
s t ~ , e s s s t e e l pmpeii down t o 2,104torr.
hgperipreitts wee conducted with a contipa- oas flow,of gas at pressrtre of 5,10*5,
~ ~ - ~ t o r r . B ~ e &iihwme geaera-bor (welo'?
k 4 , ~ = 1 0 ~ , r # . + ) e ~ r ~ i t d the HI1-wa- ve -in wcxpeguid~).
I?he ionisation frequeuey Vi was deter-
m e d from the, conditi~n o f nonatation- - btedraoan T = \ ) ~ - ))d=tl.ln n,m, ,*we t
i s the measmed duration of the influenee o f microwave radiation,gd i s the characte- r i s t i c freqrzeucy of electron losses, and
n* md ago-the f i n a l and Wtial eleckcon densities,the later w a s created during io- nization o f the gas by electrons emitted from heated tq.s.t;en f i l a m a t (Ua=30-40V) skcetcheb aoross the wa[pggeride in the a- tinode region of the electric f i e l d o$ the Hll stam w-8 (~omalw t o %)(~igr2, iosertim).!Phe value o f nw rsaDhsa
lo9&
neaz' the f i l a 8 ~ 1 t and 5eV.The tinre
C O ~ S ~ G Q L ~ S o i electron loems
td=qdW1
wtmaae-&82!mined exparimaxb- from a plasma d e
cw
(tdt2Fj0ps 002 m g a d rJs rold 10- 1 5 p ~ for hsllru).,lo
cw7/5:
3ig.l
The fact of %breakdownn was established by Ihe taminat;ion o f microwme t~msmis-
sien through .&he l a y e and by the n e e r g ~ ~ & e - of aceelwated d w t r ~ m (in $ di-
rection) #en reae e~ilxi.cal pl-a
d d t y n,pmd&.~m3.!l!he mw2 c u r r a t e f accelerated el-ons wa-ret&~~tsred by a r m x l t i r n i a pmbe
a&&.=
%e sideof +&e wanreguida,"h Fig.2,the depaai damees, on &,of tho weraged4ve-the-spe- - c t m frequancieg o;C ioaization p ' e atom Ji ace prcesauted,In 4zhe regi4uz oZ we&
fields
the
values of .vi_are inaatidactory agreem8~1.t; with those m e s a - tea in /I, 2/, and a t higher fields there i s iwgeeateat w i t h the calculated depernden- ce (Fig.l).Tn o m e s of Irig.2,the values
Eeare cited through a vaauwa f i e l d Eo (aplifieation of f i e l d on the &'ilenent can 9836 an increase by a factm ef 2-3).
Fig. 2
m e o b t r ~ n d a e p ~ a c e s r/no en
&
c a be used t o errfaat;% the BIanlnnmr time f o re n r p e ~ i m ~ t s w i t h strong mS.crowave fields.
ResultstAgre8~ieut has be= obBained for thwre%iaal e x p ~ ~ t a l depcmde~rces f o r the constcprt of breakdown ip gases )fc
=gi
in strong fiialds (Ee>>~>,i;e. in the region &ev& by pow= pulse lasers cOla mic~awave geareators /?I, S/.Contirruatim3- 4
of earpezxbnaats b the region of
&
=I0 10 eV (decrease i n theX/ho,l?ig.l) rwuir&a s w e of radiation from super-high par w a r relativistic? microwme getzerators /6/.
Befea?qncest
/ I / ~ ~ ~ a c D o n a t ~ . ~ a r o w a v e breakdown in ga- ses", ~'m",1969
Yu.P^Be;LzertlLasar spsrlc and discharge propagat$-*
,
wNaukan, 974.Yu.V*Bfaa~ 3- e t all* ,XB3Ph,Z7,58@, 3969
/4/ L, J ; ~ F ~ ~ B E e t all- ,~ev.Y.Ph. ,j8, I 966 / 5 / . 1 ~ F t . ~ ~ e ~ " 1 n t 8 ~ 8 ~ % i ~ 9 Of d c p -
ctrom-etic fields wlth plamuaw 9 "&*onrfi;
-
a&",
7 928/6/ B.P,ICoviJlw,LI.Petel~,M.D.Raiz~,
(4f; d.l.,=h L8tt~~~,18,232,1973
