PLASMA EFFECTS IN ION BEAM TARGET INTERACTION

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PLASMA EFFECTS IN ION BEAM TARGET INTERACTION

E. Nardi, Z. Zinamon

To cite this version:

E. Nardi, Z. Zinamon. PLASMA EFFECTS IN ION BEAM TARGET INTERACTION. Journal de

Physique Colloques, 1983, 44 (C8), pp.C8-93-C8-106. �10.1051/jphyscol:1983806�. �jpa-00223313�

JOURNAL DE PHYSIQUE:

C o l l o q u e C 8 , s u p p l e m e n t a u nO1l, T o m e 44, n o v e r n b r e 1 9 8 3 p a g e CO-93

PLASMA E F F E C T S IN ION BEAM TARGET INTERACTION

I;.. X a r d i a n d Z. Zinamon

Weizmann i n s t - i t u t o of Sciexce, Reiiouc; t , IsraeZ

On p r Q s e n t e t r o i s e x e m p l e s oG l e s p r o c e s s u s m i s e n j e u d a n s l ' i n t c r a c - t i o n d e f a i s c e a u x d e p a r t i c u l e s c h a r g 6 e s s o n t a f f e c t s s p a r l e f a i t q u e l a c i b l e e s t un p l a s m a .3 f o r t e d e n s i t 6 d 1 6 n e r g i e : 1 . E f f e t s d e p l a s m a s u r l c p o u v o i r d ' a r r d t . 2 . E f f e t s d e p l a s m a s u r l l G t a t d e c h a r g e d e s i o n s r a p i d e s . 3 . E f f e t s d e I ' o p a c i t 6 d u p l a s m a i m p o r t a n t s p o u r l ' i n t e r p r 6 t a ~ i o n d e s m e s u r e s s p e c t r o s c o p i q u e s .

A b s t r a c t

We p o i n t o u t t h r e e e x a m p l e s o f c a s e s i n w h i c h p r o c e s s e s i n v o l v e d i n t h e i n t e r a c t i o n o f c h a r g e d p a r t i c l e b e a m s a r e a f f e c t e d b y t h e f a c t t h a t t h e t a r g e t is a h i g h e n e r g y d e n s i t y p l a s m a : 1. P l a s m a e f f e c t s o n t h e s t o p p i n g m u e r . 2.

P l a s . n a e f f e c t s o n t h e c h a r g e s t a t e o f f a s t i o n s . 3. P l a g n a o p a c i t y e f f e 0 t . s i n p a r t a n t i n t h e i n t e r p r e t a t i o n of s p e c t r o s c o p i o m e a s u r e s e n t s .

1.

I n t r o d u c t i o n .

I n p a r t i c l e bea:n i n e r t i a l c o n f i n e m e n t f u s i o n s y s t m s o n e e n c o u n t e r s h i d h d e n s i t y , h i g h t e m p e r a t u r e m a t t e r . I n p a r t i c u l a r , t h e r e g i o n i n w h i c h t h e beam e n e r g y is d e p o s i t e d c o n s i s t s o f h i g h l y i o n i z e d p l a s m a a t t e m p e r a t u r e s w h i c h , u n d e r c o n d i t i o n s r e l e v a n t f o r a c t u a l f u s i o n s y s t e m s , a r e o f t h e o r d e ~ o f a f e u h u n d r e d s eV. Under s u c h c o n d i t i o n s many f e a t u r e s o f t h e b e a n - t a r g e t i n t e r a c t i o n p r o c e s s e s may b e s i g n i f i c a n t l y d i f f e r e n t f r o m t h e c o r r e s p o n d i n g o n e s i n t h e b e t t e r known s i t u a t i o n o f c o l d m a t t e r . I n t h i s work u e p r e s e n t s t u d i e s o f t h r e e e x a n p l e s o f s u s h c a s e s , w n i c h d e s e r v e e x p e r i m e n t a l a n d t h e o r e t i c a l t r e a t m e n t . T n e s e a r e : 1. P l a s m a e f f e c t s o n t h e s t o p p i n g power o f p a r t i c l e s o f known c h a r g e w h i c h b e n a v e l i k e p o i n t c h a r g e s , 2. P l a s a a e f f e c t s o n t h e c h a r g e s t a t e of f a s t

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1983806

(28-94 JOURNAL DE PHYSIQUE

i o n s a s t h e y a r e s l o w e d down, 3. P l a s m a o p a c i t y e f f e c t s i m p o r t a n t i n t h e i n t e r p r e t a t i o n o f m e a s u r e a e n t s , i n p a r t i c u l a r i n K, s p e c t r o s c o p y .

2. P l a s m a e f f e c t s o n t h e s t o p p i n g p o u e r .

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Tne d i f f e r e n c e s i n s t o p p i n g power b e t w e e n p l a s n a t a r g e t s and c o l d m a t t e r t a r d e t s f o l l o w f r a n two f a c t o r s : 1. The s t o p p i n g power d u e t o t h e f r e e e l e c t r o n s i n t h e p l a s n a i s d i f f e r e n t f r a n t h e s t o p p i n g power d u e t o bound e l e c t r o n 3 i n c o l d m a t t e r . 2. The c o n t r i b u t i o n t o s t o p p i n g o f bound e l e c t r o n s i n t h e p l a s m i o n s is d i f f e r e n t f r o m t n a t o f bound e l e c t r o n s i n n e u t r a l a t o m s i n c o l d m a t t e r .

I n t h e p l a s m a s c o n s i d e r e d h e r e t h e f r e e e l e c t r o n s c a n be r e g a r d e d a s a n i d e a l non d e j e n e r a t e g a s ' ) . We c a l c u l a t e t h e i r c o n t r i b u t i o n t o t h e s t o p p i n g p d e r u s i n g t h e p l a s s a d i e l e c t r i c f u n c t i o n :

d e r e e i s t h e e l e c t r o n c h a r g e , 2 t h e p r o j e c t i l e c h a r g e , p t h e d e n s i t y , k t h e wave ntvnber, p + c o s 8 , g t h e a n g l e b e t w e e n t h e wave v e c t o r and t h e v e l o c i t y v e c t o r , v t n e p a r t i c l e v e l o c i t y , w t h e f r e q u e n c y . D t h e d i e l e c t r i c f u n c t i o n .

l h e c o n t r i b u t i o n o f t h e bound e l e c t r o n s i n t h e p l a s m a i o n s is e v a l u a t e d b y a c a l c u l a t i o n o f t h e e f f e c t i v e B e t h e i o n i z a t i o n e n e r g y I , u s i n g t h e h o m a s - F e r m i modcl f o r t h e i o n s . ' ) T n i s a l l o w s o n e t o t a k e i n t o c o n s i d e r a t i o n t h e e f f e c t of b o t h i o n i z a t i o n s t a t e and e x c i t a t i o n s of t h e p l a s m a i o n e . I n o u r m o d e l t h e e f f e c t i v e i o n i z a t i o n e n e r g y i s g i v e n by:

H e r e w i s a f r e q u e n c y o f r e v o l u t i o n g i v e n by

v h e r e Et i s t h e t o t a l e l e c t r o n e n e r g y a t p o i n t r , V ( r ) is t h e p o t e n t i a l , p i s t n e c h e n i c a l p o t e n t i a l , n ( w ) i s t h e number o f e l e c t r o n s p e r u n i t f r e q u e n c y a t U .

r max ^{( W )} is t h e r a d i u s beyond which t h e energy which f o l l o w s from W i n d i c a t e s a f r e e e l e c t r o n . A s h e l l c o r r e c t i o n is included by e l i m i n a t i n g t h o s e e l e c t r o n s f o r wnich 2mv 2 <b. As was shown e a r l i e r l s 2 ) t h e plasma e f f e c t under c o n d i t i o n s o f i n t e r e s t can r e s u l t i n a r a n g e s h o r t e n i n g by a f a c t o r c l o s e t o 2. Here we d e n o n s t r a t e t h e p o s s i b l e t e m p e r a t u r e e f f e c t on I, i . e . t h e e f f e c t o f d i f f e r e n t e x c i t e d p p u l a t i o n s a t d i f f e r e n t t e m p e r a t u r e s and d e n s i t i e s which r e s u l t i n t h e s a q e degree o f i o n i z a t i o n . In Table I we l i s t v a l u e s o f I a s c a l c u l a t e d i n our model f o r A l a t s o l i d and 0.01 s o l i d d e n s i t i e s o v e r t h e t e m p e r a t u r e range o f 0.1 KeV

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0.2 KeV. For comparison we a l s o l i s t I v a l u e s c a l c u l a t e d by McCuire e t

f o r v a r i o u s A 1 i o n s i n t h e ground s t a t e . Che (nay conclude from t h i s t a b l e t h a t n o b i c e a b l e d i f f e r e n c e s i n I c a n a r i s e even when t h e charge s t a t e s in d i f f e r e n t plasmas a r e e q u a l .

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E f f e c t i v e i o n i z a t i o n p o t e n t i a l 5 I f o r A 1 a t v a r i o u s t e m p e r a t u r e s and degrees o f i o n i z a t i o n .

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exanple of a proposed e x p e r i m e n t a l t e s t c o n f i g u r a t i o n . A beam o f d e u t e r o n s o f 1 MeV a t 500 kA/cn2 o r 200 kA/cfi2 and 1 M A / U ~ ~ h i t s a 8 pm t h i c k CD2 f o i l . Such bean c u r r e n t d e n s i t i e s a r e a l r e a d y present-day s t a t e of t h e a r t . A s a r e s u l t o f t h e energy d e p o s i t i o n i n t h e f o i l it h e a t s up and expands. The p r o c e s s was c a l c u l a t e d b y a f u l l hydrodynamics s i m u l a t i o n . b e t o t h e dependence o f t h e s t o p p i n g p w e r on t h e t e m p e r a t u r e and d e n s i t y , t h e energy d e p o s i t i o n p r o f i l e v a r i e s with time. ?he r e s u l t s o f t h e c a l c u l a t i o n a r e shown i n F i g . 1, where t h e d e p o s i t i o n p r o f i l e s a r e g i v e n i n t a g r a n g e a n c o o r d i n a t e s a t t h e beginning of a s t e p f u n c t i o n p u l s e , and a f t e r 15 ns i n t o t h e p u l s e . The enhancement by a f a c t 0 1 c l o s e t o 2 of t h e s t o p p i n g power: i s e v i d e n t . S i n c e t h e 8 p m f o i l i s sub-range

C8-96 JOURNAL DE PHYSIQUE

t h i s enhancement i n s t o p p i n g power is expected to r e s u l t i n a t i m e dependence of t h e e x i t energy o f t h e beam p a r t i c l e s from t h e back s i d e o f t h e t a r g e t . This is shown i n Fig. 2. A p r o p e r measurement o f t h e t i m e dependent e x i t e;mrgy i s a t o o l f o r t e s t i n g t h e s t o p p i n g power t h e o r y .

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Fig. 1. Energy d e p o s i t i o n p r o f i l e s o f l MeV d e u t e r o n beams i n a CD2 t a r g e t a t t h e b e g i n n i n g and a f t e r 15ns o f t h e p u l s e .

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Fig. 2. The e x i t energy o f d e u t e r o n s a t t h e back s i d e o f a CD2 t a r g e t . The t a r g e t and beams are t h e same a s i n Fig. 1.

3. The c h a r g e s t a t e of f a s t i o n s i n plasma t a r g e t s .

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Tne s t o p p i n g power c a l c u l a t i o n s d e s c r i b e d above assume a known c h a r g e o f t h e p o i n t p a r t i c l e s . k w e v e r , f o r heavy and i n t e r m e d i a t e i o n s t h e c h a r g e s t a t e of t n e p r o j e c t i l e a s i t moves through t h e t a r g e t h a s t o be d e t e r m i n a t e d . h e s i t u a t i o n i n plasma t a r g e t s is d i f f e r e n t from t h a t i n t h e b e t t e r known c a s e o f c o l d t a r g e t s 4 ) . The reason is t h a t t h e competing p r o c e s s e s o f l o s s and c a p t u r e of e l e c t r o n s by t h e p r o j e c t i l e a r e d i f f e r e n t i n t h e two c a s e s . The l o s s p r o c e s s in c o l d t a r g e t s is due t o c o l l i s i o n s with t h e t a r g e t atoms, while i~ plasma t a r g e t s i t is due t o c o l l i s i o n s with t h e i o n s and with t h e f r e e e l e c t r o n s . Tne c a p t u r e i n c o l d t a r g e t s t a k e s p l a c e f r o n bound s t a t e s i n t h e t a r g e t atoms, w h i l e i n p l a s a a t a r g e t s f r e e e l e c t r o n s a r e c a p t u r e d . ?he d i f f i c u l t y with t h e l a s t p r o c e s s is t h a t t h e e x c e s s energy o f t h e f r e e e l e c t r o n has t o be c a r r i e d away e i t h e r by r a d i a t i o n o r by a t h i r d body

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a f r e e o r a bound e l e c t r o n .

I n our c a l c u l a t i o n s 5 ) c o l l i s i o n s with t a r g e t atoms =r i o n s a r e i n t h e b i n a r y encounter approximation (BEA). The t o t a l c r o s s s e c t i o n f o r t h i s p r o c e s s i S

Here Nn _{i s} t h e number o f e l e c t r o n s i n s h e l l n , Un is t h e binding energy, Vn i s t h e s c a l e d v e l o c i t y v/vn where v i s t h e o r b i t a l v e l o c i t y o f t h e t a r a e t e l e c t r o n and v is t h e p r o j e c t i l e v e l o c i t y , and G(Vn) i s taken fram McGuire and Riohard

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s e c t i o n f o r i o n i z a t i o n i n t h e BEA.

The c r o s s s e c t i o n f o r i o n i z a t i o n by t h e plasma fret3 e l e c t r o n s is '):

where N i s t h e nunber o f e l e c t r o n s i n t h e p r o j e c t i l e s h e l l c o n s i d e r e d , U i s t h e i r i o n i z a t i o n e n e r g y , ~ ~ = r n v ~ / 2 where v is t h e l a r g e r of t h e plasma t h e r m a l e l e c t r o n v e l o c i t y vt and t h e p r o j e c t i l e v e l o c i t y v .

JOURNAL DE PHYSIQUE

C a p t u r e by t h e p r o j e c t i l e o f bound e l e c t r o n s i n t h e t a r g e t i o n s is

c a l c u l a t e d by u s i n g B e l l ' s t h e o r y 7 ) . F o r c a p t u r e o f f r e e e l e c t r o n s we c o n s i d e r t h e r a d i a t i v e , t h r e e body, a n d d i e l e c t r o n i c r e c o m b i n a t i v n p r o c e s s e s , ' h e r a d i a t i v e r e c o m b i n a t i o n r a t e is c a l c u l a t e d f o l l o w i n g s e a t o n g ) f o r v("

t

where aZR is t h e r a t e i n c m 3 /S f o r a n i o n o f h y d r o g e n - l i k e c h a r d e s t q t e Z, IZ 1s t h e i o n i z a t i o n e n e r g y , Te i s t h e e l e c t r o n t e s ~ e r a t u r e i n O K and ne i s t h e f r e e e l e c t r o n d e n s i t y . For v > v t T i s r e p l a c e d b y mv /2k. ' h e t h r e e body 2

r e c o s b i n a t i o n i s c a l c u l a t e d u s i n s t h e a d a D t a t i o n l O ) o f Thornson's classical t h e o r y . For v < v t :

d t = vk ^{E L} R:-z '' ^{f l o}

wi.lere R o = 2 2 e 2 / 3 k ~ . In t h e c a s e ">vt. v t is r e p l a c e d b y V i n E q . ( 4 ) and 3kT/2 i s r e p l a c e d b y mv2/2. F o r t h e d i e l e c t r o n i c r e c o s b i n a t i o n r a t e we c h o s e t h e v a l u e 1 1 )

% = l 0 - l 1 , which is b e l i e v e d t o be a n u p p e r l i m i t , d u e t o t h e n e g l e c t o f t h e e f f e c t s o f c o l l i s i o n s i n d e s t a b i l i z i n g t h e e x c i t e d i n i t i a l c o n f i g u r a t i o n s .

F i n a l l y , t h e p o p u l a t i o n s o f e a c h c h a r g e s t a t e P a r e c a l c u l a t e d s e l f c o n s i s t e n t l y w i t h t h e e n e r g y l o s s a l o n g t h e beam t r a j e c t o r y :

where j d e n o t e s a c h a r g e s t a t e , aR and a I a r e t h e t o t a l r a t e s o f r e c o n b i n a t i o n and i o n i z a t i o n , r e s p e c t i v e l y .

In t h e f o l l o w i n g we p r e s e n t some r e s u l t s o f o u r c a l c u l a t i o n s . R e s u l t s f o r c a r b o n i o n s i n c i d e n t o n a l i t h i u m t a r g e t a r e g i v e n i n F i g . 3. For a f u l l y i o n i z a d t a r g e t t h e c a r b o n i o n s a r e a s s u s e d t o h a v e i n i t i a l c h a r g e s t a t e o f Z = 3 . Tne i n i t i a l e n e r g y i s 1 MeV/amu. F o r c o m p a r i s o n we show also t h e c h a r g e p r e d i c t e d f o r a c o l d t a r g e t . 1 2 ) I t is e v i d e n t t h a t t h e l e s s e f f i c i e n t C a p t u r e o f f r e e e l e c t r o n s c a u s e s a s u c h h i g h e r i o n i z a t i o n S t a t e i n t h e p l a s a a t h a n I n t h e c o l d t a r g e t , a n d t h i s h i g h d e g r e e o f i o n i z a t i o n i s m a i n t a i n e d down t o q u i t e I O W

e n e r g i e s . The same h o l d s f o r aluminium i o n s i n a c a r b o n t a r l g e t ( F i g . 4 ) . & r e we show how t n e c h a r g e s t a t e is a f f e c t e d b y t h e t a r g e t d e g r e e o f i o n i z a t i o n . ' h e v a l i d i t y o f o u r c a l c u l a t i o n s f o r c o l d m a t t e r i s c h e c k e d by cornparins o u r r e s u l t s

w i t h t h o s e p r e d i c t e d b y & t z . 12) Tne e f f e c t s o f t h e enhanced c h a r g e s t a t e on t h e d e p o s i t i o n p r o f i l e a r e shown i n F i g . 5. A p a r t f r m t h e e x p e c t e d r a n d e

s h o r t e n i n g , t h e r e i s a d r a s t i c e f f e c t o n t h e s h a p e o f t h e p r o f i l e . h e Bradg peak i s due t o t h e f a c t t h a t i n a p l a s a a t a r g e t t h e h i g h and n e a r l y o o n s t a n t i o n i z a t i o n s t a t e p r e v a i l s down t o v e r y low e n e r g i e s .

Tne knowledge o f t h e p r o j e c t i l e c h a r g e s t a t e i s e s s e n t i a l f o r d e a l i n g w i t h t h e p r o b l e n o f bean p r o p a g a t i o n i n a b a c l y r o u n d n e u t r a l i z i n g low d e n s i t y plasma.

An e x a n p l e i s g i v e n i n F i g . 6 i n which t h e c h a r g e s t a t e o f 1 #eV/anu c a r b o n i o n s ( i n i t i a l l y Z c 2 ) i s shown a s f u n c t i o n o f t h e d i s t a n c e it t r a v e r s e s i n a f u l l y i o n i z z d l o w d e n s i t y He p l a s n a c h a n n e l . A s i m i l a r c a s e f o r U p r o j e c t i l e is shown i n F i g . 7. I n c o n j u n c t i o n w i t h a n e x p e r i m e n t d e v i s e d by E e i

as

13) t o m e a s u r e t h e c h a r g e s t a t e o f e n e r g e t i c i o n s i n l a s e r produced p l a s n a , we h a v e c a l c u l a t e d t h e c h a r g e s t a t e o f 1 MeV/amu c o p p e r i o n s a s f u n c t i o n o f d i s t a n c e t r a v e r s e d i n a CH2 p l a s n a a t a t e n p e r a t u r e o f 1 keV and a d e n s i t y o f 1 ~ - ~ ~ / c 1 1 ~ ( F i g . 8). Tne d i f f e r e n c e f r a n t h e p r e d i c t i o n f o r c o l d m a t t e r i s v e r y s i g n i f i c a n t qnd o b s e r v a b l e o v e r t h e e x p e c t e d p l a s s a d i m e n s i o n s .

h (a) fully ionized target

e I

2l ^{C beam,} Li target E (MeV)

F i g . 3 . The c h a r g e s t a t e o f c a r b o n i o n s s l o w e d down i n l i t h i u m t a r g e t s .

JOURNAL DE PHYSIQUE

I I 1 T I 1 I 1 I 1

(a) fully ionized target

-

(b) 2bound electrons in target

- -

-

AI beam,

C

target

Oo

¹

10

^{I 1}

20

^{I l} 30 ^{I I}

40

^{I 1}

5 0

¹

E

(MeV)

Fig. 4. The charge state of aluminium ions slowed down in carbon targets.

Fig. 5. Energy deposition profiles of carbon and aluminium ions slowed down in

201j

lithium and carbon targets.

10

C b e a m

-

Li target

-

Fully ionized target

-

Cold target

10- I I I I I I l

I

A I b e a m - C target Fully lon~zed target

-

Cold target

I l l I

0 1.0 2.0 3.0 4.0

rng /cm2

DISTANCE ( c m )

C projectile in He channel ( p =10-~cj/crn fully ionized )

3

- I I L I I I I I I

6 -

-

- -

Fig. 6 . Charge s t a t e o f i n i t i a l l y 1 MeY/amu carbon i o n s i n a low d e n s i t y He

2 - I

plasma channel.

- -

U projectile at I MeV/ amu in He channel

( p = ~ ~ - 6 g

/cm3, fully ionized)

35 1 I 1 1 1 1 1 1

-

- BETZ -

I 1 0 10 20 30 4 0 50 60 70

' 0 k ² 15 ^{1'8 $1 2!4 :7}

DISTANCE ( cm )

Fig. 7. Charge s t a t e of i n i t i a l l y 1 MeY/amu u r a n i u q i o n s in a lo* d e n s i t y He plasma channel.

JOURNAL DE PHYSIQUE

I

( m m )

F i g . 8. Charge s t a t e o f i n i t i a l l y 1 ~ e V / a m u c o p p e r i o n s i n a l a s e r produced CH2

3 3

p l a s m a T = i k e ~ ,

P

^{-10- g/cm}

.

4. O p a c i t y e f f e c t s .

--p

x-rays e s i s s i o n i s a u s e f u l t o o l i n plasma d i a g r ) o s t . i c ~ . ' ~ ) I n c o l d m a t t e r t h e K p h o t o n s a r e a b s o r b e d by t h e p h o t o e l e c t r i c e f f e c t . However a t

a

h i g h e r t e n p e r a t u r e s , uhen t h e L - s h e l l is i o n i z e d , r e s o n a n t l i n e a b s q r p t i o n i s a l s o p o s s i b l e , and t h i s may h a v e a d r a s t j c e f f e c t o n t h e s e l f a b s o r p t i o n and nence on t h e i n t e r p r e t a t i o n o f m e a s u r e x ~ e n t s ~ ~ ) . T h i s r e s o n a n t l i n e a b s o r p t i o n i s n a d e p o s s i b l e by t h e e x i s t e n c e i n t h e p l a s m a o f a d i s t r i b u t i o n o f i o n i z a t i o n s t a t e s . Thus t h e l i n e

i s absorbed b y

T n i s r e s o n a n t s e l f a b s o r p t i o n n a y h a v e a d r a s t i c e f f e c t o n t h e o b s e r v e d K a s p e c t r u m , and t h e r e f o r e s h o u l d b e c o n s i d e r e d i n t h e i n t e r p r e t a t i o n o f K

a d i a g n o s t i c s i n h i g h t e m p e r a t u r e s y s t a n s . As a n e x a n p l e we u s e t h e c a s e of a 1 MeV, 1 ~ ~ / cp r o t o n bean h i t t i n g a 1Gp m ~ m t h i c k a l u m i n i ~ n f o i l . The r e s u l t s o f a

f u l l h y d r o d y n a n i c s i m u l a t i o n c a l c u l a t i o n a r e shown i n F i g s . 9-11. I n F i g . 9 t h e t e , n p e r a t u r e p r o f i l e a f t e r 1 5 n s i n t o t h e p u l s e i s shown. In F i g . 10 we p r e s e n t t h e r e s u l t i n g d i s t r i b u t i o n s o f t h e v a r i o u s d e g r e e s o f i o n i z a t i o n i n t h e p l a s m a , The e x p e c t e d s p e c t r u m w i t h and w i t h o u t t h e r e s o n a n t s e l f a b s o r p t i o n i s shown i n F i g . 11. h e c a l c u l a t i o n o f t h i s s p e c t r u i n is a a d e s i m p l e r by t h e f a c t t h a t t h e l i n c ' s i n t h e a r r a y c o r r e s p o n d i n g to e a c h t r a n s i t i o n m e r g e i n t o b a n d s o f a p p r o x i n a t e l y 5 e V i n w i d t h . 1 5 ) I t is e v i d e n t fr0.n F i g . 11 t h a t t h e l i n e o p a c i t y e f f e c t is v e r y b i g b o t h o n t h e i n t e n s i t y a n d o n t h e s p e c t r u i n o f t h e $ e m i s s i o n .

a h i s s h o u l d b e t a k e n i n t o a c c o u n t i n d e s i g n i n g and i n t e r p r e t i n g e x p e y i a e n t s u s i n s K d i a g n o s t i c s i n h i g h t a n p e r a t u r e t a r g e t s .

a

X

( c m )

F i g . 9. T e m p e r a t u r e p r o f i l e i n an i n i t i a l l y 10 m a l u m i n i u m t a r g e t h i t by 1 MeY,

2

r

1 MA/cm p r o t o n beam, afer 15 n s i n t o t h e p u l s e .

JOURNAL DE PHYSIQUE

Fig. the target of Fig. 9.

X (cm)

10. Distributions of the various degrees of ionization in

z

Fig. 11. Calculated K d s a t e l l i t e s p e c t r a a t t h e back s i d e o f t h e t a r g e t of Fig.

9,10. [a) S e l f a b s o r p t i o n due t o l i n e s and p h o t o e f f e c t , Cb) S e l f a b s o r p t i o n due t o p h o t o e f f e c t a l o n e .

0

';;0 2 -

C t 3

?' P

- -

n

L

0 +- X -

V) C W

2

4-

2 -

I I I I I l

4-

a

_-

-

-

I I

I

-

I

b

6-

-

-

-

-

-

- -

-

I

^I

2 3 4 5 6 7 8

5. C o n c l u s i o n s .

-

We h a v e shown t h r e e e x a n p l e s o f c a s e s i n which p l a s n a e f f e c t s a r e i m p o r t a n t i n d e a l i n g w i t h p r o b l e s s o f b e a n - t a r g e t i n t e r a c t i o n :

1. P l a s s a e f f e c t s o n t h e r a n $ e o f p a r t i c l e s o f known c h a r g e a r e i m p o r t a n t ( f a c t o r o f o r d e r 2 r e l a t i v e t o c o l d t a r g e t s ) i n t h e r a n g e o f p a r a s e t e r s r e l e v a n t t o ICF.

2. P l a s a a e f f e c t s o n t h e c h a r g e s t a t e o f h e a v y and i n t e r m e d i a t e i o n s may r e s u l t i n d r a s t i c e f f e c t s 'on t h e r a n g e and s h a p ~ o f t h e e n e r g y d e p o s i t i o n c u r v e .

3. Plasma e f f e c t s o n t h e i n t e n s i t y and s p e c t r u u o f K e m i s s i o n s h o u l d be c o n s i d e r e d i n t h e d e s i g n and i n t e r p r e t a t i o n o f e x p e r i i n e n t s u s i n g K d i a g n o s t i c s .

A l l t h e s e e f f e c t s d e s e r v e e x p e r i m e n t a l v e r i f i c a t i o n . T h i s is d i s c u s s e d i n a n o t h e r p a p e r . 16)

R e f e r e n c e s .

1. E. N a r d i , E. P e l e g , and Z. Z i n a n o n , Phys. F l u i d s

21,

578 ( 1 9 7 8 ) . E. t b r d i and Z. Zina:non, Pnys. Rev.

m,

1246 ( 1 9 7 8 ) .

2. E. N a r d i , E. P e l e g , and Z. Z i n a s o n , Appl. Phys. L e t t .

39,

46 (1981).

3. E. J. McCuire, J. M. P?ck, and L. C. P i t c h f o r d , Pnys. Rev.

a,

⁷³¹⁸ ( 1 9 8 ~ ) .

4. D. S. B a i l e y , Y. T. Lee, and R. M. More, B u l l . An. PhyS. Soc.

6 ,

⁹⁰⁰

( 1 9 8 1 ) .

5. E. Nardi and Z. Z i n a n o n , F'hys. Rev. L e t t .

3,

1251 ( 1 9 5 2 ) .

6. P. R i c h a r d , i n A t o s i c I n n e r S h e l l P r o c e s s e s I, e d i t e d b y B. Crasemann ( A c a i i e s i c , New Y o r k , 1 9 7 5 ) , p . 73.

7. C. I. B e l l , F h y s . Rev.

90,

548 ( 1 9 5 3 ) .

8. U: L o t z , 2. Fhys.

z,

2 0 3 ( 1 9 6 7 ) and

216,

241 ( 1 9 6 8 ) .

CB-106 JOURNAL DE PHYSIQUE

g. M . J. S a t o n , Mon. M t . Roy. A s t r o n . S o c . 1 1 9 , 81 (1953).

10. Ya. B. Z e l d o v i c h and Yu. P. R a i z e r , P h y s i c s of % o c k Waves and High t e m p e r a t u r e H y d r o d y n a m i c Rlenomena ( A c a d a i c , N e w Y o r k , 1 9 6 6 ) Vol. I, p . 406.

11. Y. H a l e n , P h y s . Rev.

g,

2 8 9 6 (1980).

12. H. D. B e t z . Rev. Mod. P h y s .

E.

465 (1972).

13. R. k i - C a s , i n H i g h Fbwer B e a n s 8 1 , e d i t e d b y H. J. b n c e t and J. H. Buzzi ( E c o l e F b l y t e c h n i q u e , P a l a i s e a u , F r a n c e , 1981) p. 457.

14. I. M. V i t k o v i t s k i , L. S. L e v i n e , D. M o s h e r , a n d S. J. S t e p h a n a k i s , Appl.

Pnys. k t t . j, g (1973); D. J. J o h n s o n , B u l l . An. P h y s . Soc.

z,

⁹²⁵

( 9 7 9 ) .

15. E. N a r d i and 2. Z i n a m o n , J. A p p l . P h y s .

52,

7075 (1981 ).

16. E. b r d i and 2. Z i n a a o n , t h e s e p r o c e e d i n g s .