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Submitted on 1 Jan 1979
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ELECTRON BEAM GENERATION BY A HOLLOW CATHODE DISCHARGE
G. Popa, M. Sanduloviciu, P. Croitoru, C. Moldovan
To cite this version:
G. Popa, M. Sanduloviciu, P. Croitoru, C. Moldovan. ELECTRON BEAM GENERATION BY A HOLLOW CATHODE DISCHARGE. Journal de Physique Colloques, 1979, 40 (C7), pp.C7-187-C7- 188. �10.1051/jphyscol:1979792�. �jpa-00219498�
JOURNAL DE PHYSIQUE CoZZoque C7, suppZ&mant au n07, Tome 40, JuiZZet 1979, page C7- 187
ELECTRON BEAM GENERATION BY A HOLLOW C A M O D E DIXHARGE G. Popa, M. Sanduloviciu
*
,and P. Croitoru, C. ~ o l d o v a n * ~ . RzFacuZty of Physics*
" 2 . I . Cuzarr University, I a s i , Romania.I. F. T.A. R. Bucharest, Romania.
B l e e t r o n a of high energy have been pro- duced e i t h e r i n a pulsed plane cathode discharge /1/ o r i n a f r u s t a m . -plane cathode d i s c h a r g e /2/.
T h i s paper r e p o r t s some e x p e r i m e n t a l r e - s u l t s which show t h a t an e l e c t r o n beam of h i g h energy could be produced In a d.c.
discharge w i t h c y l i n d e r cathode which ope- r a t e s a t low c u r r e n t and h i g h v o l t a g e .
Experimental d e v i ~ e is p r e s e n t e d i n f i g . 1 .The discharge was produced I n a Pyrex- g l a s s tube (T) (7.4 c a i a n e r diameter and 4 0 cm long).A a t a i n l e s s s t e l l c y l i n d e r of 1 0 em l o n g and 1.7 am i n n e r diameter was used a s a, cathode ( C ) . I n t h e c y l i n d e r t h e r e is a s t a i n l e s s s t e l l movable p i s t o n ( P ) whiah allowed c o n t i a e u s l y change of t h e i a n e r l e n ~ h ? of t h e cathode.
Fig. 1
I
X l a t h e d i s t a n c e between pistola and front end of t h e cathode.The cathede w a s water c o o l i n g and i n s u l a t e d s o t h a t t h e i n t e r n a l s u r f a c e o n l y is used ia t h e diecharge
.&
o t h e r s t a i n l e s s s t e e l c y l i n d e r of 7 cm diameter aad 2.5 cm l e n g t h is need a s el mode ( A ) placed a t 5 em f a r from t h e cathode. In i r o a t of t h e cathode be haind
o f anode t h e r e is an e l e c t r o s t a t i c €maly- s e r of 1 cm diameter mads from a plane c o l l e c t o r ( 6 % ) and two s t a i a l e e s s t e e l g r i d s (GI and (I2) mesh o f 50% t r a n s p a - rence and 5 wires/mm.'fhe d i s t a n c e betwee~l t h e g r i d 8 and g r i d - c o l l e c t o r was 0.5 ma.
Am a x i a l l y movable o y l i w d r i c a l t u n g s t e n probe (CP 0.2 mrn diameter end 1 em l e n g t h ) was placed geral.lel t o t h e f r o n t e'dge of
t h e cathode.
The measurements a r e p e r f o r m a i n hydro- gen f o r t h e praesure range of 0.1 t o 0.02 mmHg and tha v o l t a g e of 2 t o 50 KV. A d.c.
discharge was used up t o 4 KV and a s a pulae of 5 0 ~ 1 s up t o 50 KV.For above range of parametera t h e plane cathode discharge burns i n dn abnormal regime without posi- t i v e column and c u r r e n t - v o l t a g e c h a r a c t e - r i s t i c i e g i v e n by /3/ :
v3/2 J = o o n ~ t a n t
'ac572
J is t h e c u r r e n t d e n s i t y on t h e cathode, V i a cathode f a l l measured a s a f l o a t i n g p ~ o b e p o t e n t i a l w i t h r a s p a c t t o t h e cathode and d is cathode f a l l t i c k n e s s measured a s t h e d i s t a n a e between cathode and probe whicrh was always placed a t t h e ns g a t ive glow bor de r
.
I& f i g . 2 t h e c u r r e n t v o l t a g e c h a r a c f e -
r i s t i a ( 1 ) is p r e s e n t e d f o r d i f f e r e n t cathode l e n g t h e . The e q n a t i o n ( 1 ) is w e l l
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1979792
Fig02
v e r i f l e d f o r plane cathode, When t h e cy- l i n d e r cathodr is seed the discharge s t i l l burns l~ an abnormal regime w i t h w e l l dafimite cathode f a l l and a v e r y ahazp narrow e lectrola beam come i n g o u t from t h e cathode a l o n g its a x i s and g o i a g
imato negat ive glow. For t h i s case t h e e q u a t i o n ( 1 ) is mo more v a l i d and e x p e r i - meat a 1 curve 8 show a n o a l ime a r i n e r e a s iag of t h e discharge c a r r e n t w i t h cathodr f a l l v o l t age.
The e l s c t r o l a bean diameter wae EIO more t h o r 6 mm s o t h a t a e i n g t h e e l a c t r o e t a t l a a n a l j a s r t h e e l e c t r o s beam c u r r e n t could be measured, In fig.3 t h e both discharge e u r r e n t demaity and r a t i o of t h e beam c u r r e n t ( I b ) t o t h e t o t a l diacharg8 c u r r e n t ( I ) v e r s u s cathode l e n g t h a r e presented. It shews t h a t a c y l i n d e r cathode is more e f f i c i e l a t f o r eleotrom beam p r o d n a t i a a them a plane aathsde.
T h i s e f f i c i e n c y l a c r e a s e s w i t h cathode l e n g t h . AB o f f i o i e n c j i w r e aslm$ was oberr- ved versua lor diaeharge v o l t a g e m d i t beeomes comet apt f o r h i g h e r v o l t a g e
( f l g . 4 ) .
u
( K V )Fig.4 Beferences
-.
l.G,W,HcClare, Phya.Hev.
,a
(1961) 969 2.G.Britesca,B.Toader, Rev.Roum.Phys.,3
(19781, 340.3.B,Badarru, I. Popeaca, Gas i o n i a d s . Csercharges e l e c t r i q n e s dans l e e g a s , Donnod-Blleridiene 1965.