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Submitted on 1 Jan 1979
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THE INVESTIGATION OF THE FAST ELECTRONS ENERGY DISTRIBUTION IN THE POSITIVE COLUMN AND NEGATIVE GLOW OF THE LOW
PRESSURE HELIUM DISCHARGE
L. Volkova, A. Devyatov, E. Kralkina, A. Kuralova
To cite this version:
L. Volkova, A. Devyatov, E. Kralkina, A. Kuralova. THE INVESTIGATION OF THE FAST ELEC-
TRONS ENERGY DISTRIBUTION IN THE POSITIVE COLUMN AND NEGATIVE GLOW OF
THE LOW PRESSURE HELIUM DISCHARGE. Journal de Physique Colloques, 1979, 40 (C7),
pp.C7-231-C7-232. �10.1051/jphyscol:19797114�. �jpa-00219085�
JOURUAL DE PHYSIQUE C o Z l o q u e C7, s u p p z g m e n t au n 0 7 , Tome 40, Jzr{ZZet 1979, page C7- 231
THE INVESllGATDN OF THE FAST ELECTRONS ENERGY DISTRIBUTION IN THE POSITIVE COLUMN ANLl NEGATIVE GLOW OF M E LOW PRESSURE HELIUM DISCHARGE
L.M. Volkova, A.M. Devyatov, E.A. Kralkina and A.V. Kuralova.
Moscow S t a t e U n i v e r s i t y , U.S.S.R.
The e l e c t r o n energy d i s t r i b u t i o n (ZED) was s t u d i e d i n a helium hot-cathode a r c discharge a t pressure 0,3,0.1,0.05 and 0.025 mmHg f o r t h e discharge c u r r e n t 25 lnA. The discharge was produced i n a g l a s s tube of t h e l e n g t h 70 cm and diametr 3 cia The f a s t e l e c t r o n s ener,gy d i s t r i b u t i o n was deduced from t h e experimentally mea-
sured s p e c t r a l l i n e s i n t e n c i t i e s I i n ac- cordance with [I ,2J .The s p e c t r a l l i n e s i n t e n s i t i e s were measured a c r o s s t h e d i s - charge tube a t t h e d i f f e r e n t d i s t a n c e s from t h e cathode.Fig l a , 2a r e p r e s e n t t h e dependence of t h e discharge glow i n t e n s i t y a t t h e d i f f e r e n t d i s t a n c e from t h e catho- de a t t h e p r e s s u r e 0.1 and 0.025 mm H g r e s p e c t i v e l y . The values of 10-16 inten- s i t i e s of t h e s p e c t r a l l i n e s , which were used f o r t h e c a l c u l a t i o n of EED f ( E
1.
A l l chosen s p e c t r a l l i n e s f i t t e d t h e equ
EEB were c a l c u l a t e d i n t h e energy i n t e r - v a l 29-46eV.Itts pointed out i n [3] t h a t a f t e r t h e passage throgh t h e darc catho- de space t h e e l e c t r o n irnpulse d i s t r i b u t i o n i n c l o s e t o t h e i s o t r o p i c and e l e c t r o n en- ergy i s n e a r eV
.
Here V i s the cathode drop. Consequently i t was t h e e l e c t r o n energy d i s t r i b u t i o n t h a t was determined i n t h e p r e s e n t work. F i g 1 shows t h e f a s t e l e c t r o n energy d i s t r i b u t i o n c a l c u l a t e d f o r d i f f e r e n t d i s t a n c e s from t h e cathode a t helium pressure 0.1 mrn Hg. The 1st po- s i t i o n ( see F i g l a ) corresponds approxi- mately t o the middle p a r t of t h e negative glow. The s p e c t r a l l i n e s i n t e n s i t i e s here a r e l a r g e compared t o t h e s e z t t h e o t h e r p o i n t s of t h e negative glow and m D shows sharp maximum a t 30-35 eV. f h i l e appraa- ching t h e p o s i t i v e column ( p o s i t i o n 2-51 t h e maximum diminishes and i n t h e p o s i t i - ve column we find t h e smooth EED. The served maximum on EED a t 30-35 eV canob- har-
-
- -~rtk)
Here C i s c o n s t , x i s the parainetr, which dly be a t t r i b u t e d t o t h e primary e l e c t r o n s c h a r a c t e r i s e s t h e s p e c t r a l l i n e , 3 ( X
1,
a c c e l e r a t e d by t h e cathode drop which was g K ( x ) , Q(x,& ) a r e t h e frequence, e x i t a t - about 60 V i n our case.Yhe e l e c t r o n ener- i o n t h r e s h o l d and e f f e c t i v e e x c i t a t i o n gy l o s s e s i n t h e i n e l a s t i c c o l l i s i o n s . a r e cross-section of t h e x - s p e c t r a l l i n e r e - approximately equal t o t h e e x c i t a t i o n s p e c t i v e l y , ~ i s t h e e l e c t r o n energy. A l l ( b 20 eV) and i o n i s a t i o n ( N 25 e~ ) t h r e s -Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19797114
holds, so the appearance of the secondary t h e 15 cm. from anode. A t 0.025 H@; t h e e l e c t r o n s with the energies within 35-40
eV is possible. Consequently the existen- ce of the observed aaxinux Dn IiED can be q u a l i t i vely explained by the influence of i n e l a s t i c s c a t t e r i n g of primary electrons.
I n t h e pressure 0.3 mm rig ZXD shows the redundzncy of Past e l e c t r o n s i n t h e nega- t i v e glow i f compared t o the p o s i t i v e co-.
lumn.'ilhe shape o f $ED i s smooth with,.in a l l i n v e s t i g a t e d energy i n t e r v a l . A t lower
He pressure (0.05 and 0.025 m m Hg) the be- haviour of E l D i n the negative glow i s j u s t the same a s a t 0.q a5 Bg. A t the s t a r t ; t o t h e p o s i t i v e column t h e amplifi- c a t i o n of the maximum occurs. This is li- k e l y connected with t h e presence of the s t r i a t i o n i n t h i s p a r t of t h e discharge.
Nhile moving towards t h e anode t h e max- imum diminishes. There i s weak p l a t e a u a t t h e pressure 0.05 mm Hg a t the distance of
f - Q
length of the p o s i t i v e column i n our tube i s srnall (10 cm) and even t h e anode the maximum on EZD e x i s t s . ( see Fig 2b
1.
References
I ; A.@. Devyatov, et a l . ICPIG, Prague,
1973,
Contributed Papers, p. 13.2. L.M. Volkova, e t a l . ICPIG X I I , Eindhoven, 1975, Contributed Papers,
P. 384.
3 . 1 3 . ~ .
