SURFACE PLASMA SOURCE OF HYDROGEN ATOMS WITH AN ENERGY OF HUNDREDS eV

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SURFACE PLASMA SOURCE OF HYDROGEN ATOMS WITH AN ENERGY OF HUNDREDS eV

V. Dudnikov, G. Fiksel’

To cite this version:

V. Dudnikov, G. Fiksel’. SURFACE PLASMA SOURCE OF HYDROGEN ATOMS WITH AN ENERGY OF HUNDREDS eV. Journal de Physique Colloques, 1979, 40 (C7), pp.C7-479-C7-480.

�10.1051/jphyscol:19797232�. �jpa-00219215�

JOURNAL DE PHYSIQUE

SURFACE FtASMA SOURCE OF HYDROGEN ATOMS WITH AN ENERGY OF HUNDREDS eV

V.G. Dudnikov and G.I. Fiksel'.

I n s t i t u t e o f Nuclear Physics, Novosibirsk, U.S.S.R.

1. The e f f i c i e n c y of a c c e l e r a t e d p a r t i c - l e beam p r o d u c t i o n w i t h t h e h e l p of t h e w e l l developed e l e c t r o s t a t i c beam-forming

systems d e c r e a s e s s i g n i f i c a n t l y when accel- e r a t i n g :,roltage d e c r e a s e s below one k i l o - v o l t / I / . I n o r d e r t o produce i n t e n s e beams of a c c e l e r a t e d p a r t l c i s s w i t h a n en- ergy of hundreds eV, w h i c h a r e n e c e s s a r y f o r many a p p l i c a t i o n s , one can u s e t h e s u r f a c e plasma method developed f o r pro- d u c t i o n of n e g a t i v e i o n s /2/. Negative i o n s a r e formed i n s u r f a c e plasma s o u r c e s on t h e bombarded s u r f a c e of e l e c t r o d e s w i t h a minimized work f u n c t i o n due t o t h e c a p t u r e of e l e c t r o n s from t h e e l e c t r o d e s a t t h e e l e c t r o n a f f i n i t y l e v e l of t h e s p u t t e r e d and r e f l e c t e d p a r t i c l e s . These i o n s a r e a c c e l e r a t e d by t h e n e a r - e l e c t r o d e v o l t a g e drop a c c e l e r a t i n g p o s i t i v e i o n s from t h e d i s c h a r g e plasma t o t h e e l e c t r o - de. I n t h e n e g a t i v e i o n s o u r c e s t h e s i g n i - f i c a n t s h a r e of n e g a t i v e i o n s i s d e s t r o y e d d u r i n g t h e i r movement through plasma and transformed t o t h e d i r e c t e d f l u x of atoms

e s , t h e r e were used t h e s u r f a c e plasma s o u r c e s w i t h p l a n o t r o n c o n f i g u r a t i o n of e l e c t r o d e s d e s c r i b e d i n d e t a i l i n /3/with a 1 x 10 mm2 emission s l i t and without e x t r a c t i o n system. The s o u r c e worked i n a p u l s e mode w i t h h a l f - s i n u s o i d a l p u l s e s of c u r r e n t up t o 50 A , p u l s e d u r a t i o n up t o 3 msec and r e p e t i t i o n frequency up t o 10 Hz. The f l u x e s of aocelerated.atoms and f l u x d e n s i t y d i s t r i b u t i o n s were de-

t e c t e d by t h e secondary emission d e t e c t o r (SED) and by t h e p u l s e bolometer w i t h t h e system of g r i d s t o remove charged p a r t i c - l e s . The bolometer used is analogous t o t h a t described i n /4/: r a d i a t i o n of a f o i l p r e l i m i n a r y h e a t e d up t o I O ~ O K i s de- t e c t e d by ' a photodiode ; t h e p u l s e h e a t i n g of a f o i l by a n atom f l u x l e a d s t o a n in- c r e a s e of r a d i a t i o n . ( P r e l i m i n a r y h e a t i n g is i n t r o d u c e d t o s h i f t t h e s p e c t r a of pul- s e r a d i a t i o n t o t h e s e n s i t i v e r e g i o n o f photodiode.) Bolometer s e n s i t i v i t y was 1 mA p e r j o u l .

3. When f e e d i n g t h e s o u r c e w i t h ce- w i t h a n energy of hundreds eV. One may de- sium t h e d i s c h a r g e v o l t a g e d e c r e a s e s from s t r o y a l l a c c e l e r a t e d n e g a t i v e i o n s by i n - 600+400 V t o 100+15O V and t h e SED and t e n s i f y i n g t h e d e s t r u c t i o n of them, due t o bolometer s i g n a l s a r e s h a r p l y i n c r e a s e d . t h i c k e n i n g of t h e plasma and g a s gap, and The f l u x d e n s i t y d i s t r i b u t i o n s d e t e c t e d o b t a i n atom f l u x e s w i t h a n emission d e n s i - by t h e SED and t h e bolometer were t h e sa- t y of s e v e r a l ampers p e r cm 2

.

2. To produce a c c e l e r a t e d atom f l u x - The FNHNI divergence is +lo0. The f l u x

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Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19797232

C7- 480

emission d e n s i t y is 1 A/cm2 a t a 5 A/cm2 d i s c h a r g e c u r r e n t d e n s i t y ( d i s c h a r g e cur- r e n t is 1 8 A ) . The d i s c h a r g e c u r r e n t de- pendence is l i n e a r when d i s c h a r g e v o l t a g e is f i x e d ,

A d d i t i o n a l experiments have shown t h a t t h e f r a c t i o n o f d i s c h a r g e r a d i a t i o n t o t h e SER and bolometer s i g n a l s was l e s s t h a n 10%: t h e s i g n a l s d e c r e a s e d 10+30- f o l d when we changed hydrogen t o helium, removed t h e c e n t r a l cathode p l a t e (Penn- i n g d i s c h a r g e 1, and c l o s e d t h e e n t r a n c e h o l e o f bolometer by LiF g l a s s w i t h a 70%

t r a n s p a r e n c y a t a wavelength of 1200 W.

From t h e 90° beam d e f l e c t i o n i n f l a t c a p a c i t o r t h e r e were found t h e energy spe- c t r a of n e g a t i v e i o n s produced due t o t h e charge exchange of a c c e l e r a t e d atoms on a g a s , outcoming from t h e s o u r c e and on a s p e c i a l cesium t a r g e t . (Negative i o n s from t h e s o u r c e a r e d e f l e c t e d by a magnet- i c f i e l d and n o t d e t e c t e d . )

The s p e c t r a o b t a i n e d a r e i d e n t i c a l t o t h e high-energy p a r t of s p e c t r a of ne- g a t i v e i o n s e x t r a c t e d from p l a n o t r o n s o u r c e s /5/: when d i s c h a r g e v o l t a g e i s 130 V, t h e r e were d e t e c t e d t h e p a r t i c l e s w i t h a n energy of 90*300 eV and w i t h ma- ximum of spectrum a t 160 eV; when d i s c h a r - ge v o l t a g e was 300 e V , d e t e c t e d p a r t i c l e s had an energy of 200*500 eV w i t h maximum of spectrum a t 330- eV.

References :

/I/ M.D.Gabovich, Physics and Technology of Plasma Ion Sourcee, Moscow, A-tom- i s d a t , 1972.

/2/ Yu.I.Bel~chenko, G.I.Dimov, V,G.Dud-

nikov, P r e p r i n t IMP 77-50, Novosibirsk, 1972. Froc. Symp. Production and

N e u t r a l i z a t i o n o f Negative I o n s and Beams, BNL, Upton, N.Y., 1977.

/3/ Yu. 1,Bel 'chenko, G. I,Dimov, V,G,Dud- nikov, ZhTP,

a,

/4/ RI.G.Kagansky, S.I.Lashku1, K,G,Shak- h o v e t s , F i z i k a Plasmy,

2,

/5/. Yu.I,Bel 'chenko, G,I,Dimov, V.G,Dud- nikov, I z v e s t i a Am SSSR, S e r , F i z , ,

22,