NUCLEAR MICROPROBE ANALYSIS AT KARLSRUHE

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NUCLEAR MICROPROBE ANALYSIS AT KARLSRUHE

D. Heck

To cite this version:

D. Heck. NUCLEAR MICROPROBE ANALYSIS AT KARLSRUHE. Journal de Physique Colloques,

1984, 45 (C2), pp.C2-245-C2-248. �10.1051/jphyscol:1984254�. �jpa-00223967�

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Colloque C2, supplbment a u n02, Tome 45, f6vrier 1984 page ~ 2 - 2 4 5

NUCLEAR MICROPROBE A N A L Y S I S A T KARLSRUHE

D. Heck

Kernforschungszentrwn KarZsruhe, I n s t i t u t fiir Kernphysik 111, Postfach 3640, 0-7500 KarZsruhe, F. R. G.

Rdsumd Des r d a c t i o n s avec p a r t i c u l e s chargdes s o n t employdes pour a n a l y s e r l e s dldments l d g e r s dans l a microsonde n u c l d a i r e de K a r l s r u h e . Des r d a c t i o n s (d,p) s o n t u t i l i s d e s pour ddterminer l e contenu en carbone e t a z o t e dans des c i b l e s massives m d t a l l i q u e s e t non-mdtalliques. Au moyen d e s rayons X i n d u i t s p a r l e s p a r t i c u l e s , l e s dldments avec Z 2 13 s o n t i d e n t i f i 6 s avec des concen- t r a t i o n s dans l e domaine de l a ppm. C e t t e mdthode e s t t r S s b i e n adaptde 1 l a d e t e c t i o n des dldments en t r a c e dans d e s matdriaux organiques.

A b s t r a c t Charged p a r t i c l e r e a c t i o n s a r e used i n t h e Karlsruhe n u c l e a r micro- probe f o r t h e a n a l y s i s of l i g h t elements. ( d , p ) r e a c t i o n s a r e performed t o de- termine t h e c o n t e n t of carbon and n i t r o g e n i n m e t a l l i c and nonmetallic bulk m a t e r i a l specimens. Elements w i t h Z 3 13 a r e i d e n t i f i e d by means of p a r t i c l e

induced X-ray emission (PIXE) i n c o n c e n t r a t i o n s down t o t h e ppm range. This method i s b e s t s u i t e d f o r d e t e c t i o n of t r a c e elements i n o r g a n i c m a t t e r .

I n t r o d u c t i o n I n a n u c l e a r microprobe [ l ] t h e p o s i t i o n r e s o l u t i o n of an i o n beam focussed down t o micrometer dimensions, is combined w i t h t h e v a r i e t y of r e a c t i o n s which a r e induced by H + , D+ or ~ e + i o n s w i t h e n e r g i e s i n t h e low MeV range. As by e l e c t r o n e x c i t a t i o n , r e a c t i o n products l i k e secondary e l e c t r o n s , bremsstrahlung, op- t i c a l f l u o r e s c e n c e , c h a r a c t e r i s t i c X-rays and Auger-electrons a r e e m i t t e d . Moreover t h e s e ions undergo e l a s t i c n u c l e a r s c a t t e r i n g (Rutherford b a c k s c a t t e r i n g ) and t h e energy of t h e s c a t t e r e d i o n s c a r r i e s t h e information on t h e s c a t t e r i n g nucleus and t h e depth p o s i t i o n of t h e s c a t t e r i n g e v e n t . Also n u c l e a r r e a c t i o n s with emission of secondary charged p a r t i c l e s o r gamma r a y s a r e p o s s i b l e . They a r e i s o t o p i c a l s p e c i f i c and may be used a s a n a l y t i c a l t o o l [ 2 ] . The charged p a r t i c l e d e t e c t i o n w i t h s u r f a c e b a r r i e r diodes i s h i g h l y e f f i c i e n t and i n p a r t f r e e from background r a d i a t i o n , which compensates t h e low r e a c t i o n c r o s s s e c t i o n s .

When p e n e t r a t i n g bulk m a t e r i a l , charged p a r t i c l e s a r e slowed down. Therefore t h e energy of t h e secondary p a r t i c l e s a l s o g i v e s information on t h e d e p t h , i n which t h e r e a c t i o n h a s taken p l a c e . This i s demonstrated i n t h e f i r s t example. A d d i t i o n a l l y t h e occurence of narrow resonances i n t h e energy dependence of t h e r e a c t i o n c r o s s s e c t i o n e n a b l e s depth dependent a n a l y s e s [2].

The p a r t i c l e induced X-ray emission (PIXE) e n a b l e s t r a c e element d e t e c t i o n , a s i n m a t r i c e s of low Z m a t e r i a l t h e continuous bremsstrahlung background i s about two o r d e r s of magnitude lower compared with t h e X-ray spectrum, induced by e l e c t r o n s w i t h t h e same v e l o c i t y a s t h e ions [31. This method i s w e l l s u i t e d f o r biomedical samples a s shown i n t h e second example.

~ i c r o ~ r o b e s e t u p The primary i o n beam (H+, D+, o r ~ e + ) i s generated i n a 3.5 MeV Van de Graaff a c c e l e r a t o r . By c o l l i m a t i o n and f o c u s s i n g w i t h a magnetic quadrupole dou- b l e t t h e beam diameter i s reduced t o 3 Mm a t c u r r e n t s of % 600 pA [ 4 1 . Mapping of t h e elemental c o n c e n t r a t i o n s i s performed by sweeping t h e i o n beam i n one o r both dimensions a c r o s s t h e sample s u r f a c e ; t h e d e f l e c t i o n i s c o n t r o l l e d by a d i g i t a l p a t t e r n g e n e r a t o r [ 5 ] . A S i ( ~ i ) d e t e c t o r (80 m m Z , d i s t a n c e 22 m) and a s u r f a c e

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1984254

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b a r r i e r d e t e c t o r (450 mn?, d i s t a n c e 37 mm) a r e used f o r t h e r e g i s t r a t i o n of t h e X- r a y s and t h e e j e c t e d c h a r g e d p a r t i c l e s . Both d e t e c t o r s a r e o r i e n t e d a t 135" r e l a t i v e t o t h e p r i m a r y i o n beam.

Measurement examples

a ) S u p e r c o n d u c t i n g f i l a m e n t s . I n t h e f a b r i c a t i o n of f i l a m e n t s of h i g h f i e l d s u p e r - c o n d u c t o r s which c o n s i s t of c a r b o n f i b r e s of 7 pm d i a m e t e r c o a t e d w i t h NbCN, sorne- t i m e s f a i l u r e s o c c u r e c a u s e d by a n unknown s o u r c e . It r e s u l t s i n a r e d u c t i o n o f t h e m e c h a n i c a l a d h e s i o n o f t h e s u p e r c o n d u c t i n g l a y e r o r i n a l o w e r i n g of t h e c r i t i c a l t e m p e r a t u r e . I t i s t h e hope t h a t t h e knowledge of t h e c o n t a m i n a t i n g t r a c e e l e m e n t s may g i v e a h i n t o n t o t h e s o u r c e of t h e s e f a i l u r e s . S i m u l t a n e o u s l y i t i s a l s o of i n - t e r e s t t o c o n t r o l t h e c o r r e c t s t o i c h i o m e t r i c r a t i o of t h e e l e m e n t s i n t h e supercon- d u c t i n g l a y e r . T h e r e f o r e any embedding m a t e r i a l c o n t a i n i n g carbon i s n o t p e r m i s s i b l e i n t h e t a r g e t p r e p a r a t i o n . I n a f i r s t a t t e m p t t h e f i l a m e n t s a r e embedded i n Wood's m e t a l ( a low m e l t i n g a l l o y o f 48 % B i , 26 X Pb, 1 3 % Sn and 13 % Cd). To make t h e f i l a m e n t s a d h e s i v e f o r t h i s a l l o y t h e y were e l e c t r o p l a t e d w i t h Cu. F i g . I h shows a m i c r o p h o t o of t h e p o l i s h e d s u r f a c e of a b u n d l e of f i l a m e n t s t a k e n a f t e r t h e elemen- t a l a n a l y s i s . The i n d i c a t e d a r e a was scanned w i t h a 1.44 MeV D+ beam. The r e l a t i o n between t h e e n e r g y o f t h e p r o t o n s emerging o u t of t h e ( d , p ) r e a c t i o n and t h e d e p t h w i t h i n t h e sample i s d e t e r m i n e d a n a l o g o u s w i t h f i g . 4 of r e f . [61. From t h e l a t e r a l s h i f t of t h e maxima i n t h e d i s t r i b u t i o n s f i g . la-d, a n i n c l i n a t i o n a n g l e of 75" be- tween t h e f i l a m e n t a x e s and t h e s u r f a c e normal i s d e t e r m i n e d , which a g r e e s w i t h t h e l e n g t h r a t i o 1:3 of t h e two a x e s o f t h e e l l i p t i c s e c t i o n s o f t h e f i l a m e n t s i n f i g . I h .

U n f o r t u n a t e l y t h e i n t e n s e Cu K X-rays of t h e c o a t i n g m a t e r i a l a s w e l l a s t h e L and M X-rays of a l l components of t h e embedding a l l o y c o v e r t h e i n t e r e s t i n g r a n g e of e n e r g i e s up t o 4 keV and between 6 and 16 keV r a t h e r c o m p l e t e l y , s o no s u s p i c i o u s t r a c e e l e m e n t c o u l d b e deduced t i l l now. With a m o d i f i e d specimen p r e p a r a t i o n tech- n i q u e u s i n g s o f t aluminium t o embed t h e f i l a m e n t s t h e s e measurements w i l l b e con- t i n u e d

.

b) R a t k i d n e y . The k i d n e y of a W i s t a r r a t was p r e p a r e d by shock f r e e z i n g t o l i q u i d n i t r o g e n t e m p e r a t u r e . S l i c e s of -7 pm t h i c k n e s s were c u t i n a cryo-microtome and l y o p h i l i z e d a f t e r mounting o n a ~ o r m v a r ~ b a c k i n g f o i l of ". 50 pg t h i c k n e s s . The i r r a d i a t i o n w i t h 3 MeV p r o t o n s was performed i n a l i n e s c a n mode. Along t h i s l i n e t h e complete X-ray s p e c t r u m between 1 and 2 4 keV was r e c o r d e d a s a f u n c t i o n of po- s i t i o n . S i m u l t a n e o u s l y f o r e a c h p o i n t of t h e s c a n l i n e t h e t o t a l amount of back- s c a t t e r e d p r o t o n s was r e g i s t e r e d t o deduce t h e l o c a l mass t h i c k n e s s o f t h e sample, which i s needed f o r t h e d e t e r m i n a t i o n of t h e l o c a l e l e m e n t a l c o n c e n t r a t i o n s 171. The

t h i c k n e s s i s p l o t t e d on t o p of t h e e l e m e n t a l d i s t r i b u t i o n s i n f i g . 2 .

Two pronounced d i p s i n t h e d i s t r i b u t i o n s of C 1 and K a r e caused by lumina o r i - g i n a t i n g p r o b a b l y from p r o x i m a l o r d i s t a l c o n v o l u t e d t u b u l e s . T h i s i s confirmed by t h e a b s e n c e of F e , which would b e p r e s e n t i n t h e c a s e of blood v e s s e l s . I n t h e s p a c e between t h e s e two lumina t h e s c a n n i n g p a t h c r o s s e s a g l o m e r u l u s ( s e e microphoto i n t o p of f i g . 2 ; t h e c e n t e r of t h i s g l o m e r u l u s i s 50 pm above t h e s c a n l i n e ) . It i s r e s p o n s i b l e f o r t h e i n c r e a s e of Fe (hemoglobin from r e d blood c e l l s ) and a l s o of Cu.

The i n c r e a s e d c o n c e n t r a t i o n of Br n e a r t h e l e f t end of t h e s c a n l i n e may b e ex- p l a i n e d by t h e o c c u r e n c e of a g r a n u l o c y t e ( w h i t e blood c e l l ) , which i n d i c a t e s on a n i n t e r l o b u l a r a r t e r y . T h i s i s s u p p o r t e d b y t h e h i g h e r Fe c o n c e n t r a t i o n ( e r y t r o c y t e s ) . The n e i g h b o u r i n g peak i n t h e Ca d i s t r i b u t i o n may b e c a u s e d by a c a l c i f i c a t i o n of t h e w a l l of t h e i n t e r l o b u l a r a r t e r y .

Summary These two examples might d e m o n s t r a t e t h e v a r i e t y of a p p l i c a t i o n s of a nuc- l e a r microprobe. E s p e c i a l l y t h e u s e of n u c l e a r r e a c t i o n s o r b a c k s c a t t e r i n g o f f e r s t h e p o s s i b i l i t y o f a 3-dimensional e l e m e n t a l a n a l y s i s w i t h o u t d e s t r o y i n g t h e s p e c i - men.

R R e g i s t e r e d Trade Mark of Monsanto Chemical Co.

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(d,p,) in depth

F i g . 1 A n a l y s i s o f s u p e r c o n d u c t i n g f i l a m e n t s of c a r b o n c o a t e d w i t h NbCN. The f i l a - ments a r e embedded i n Cu w i t h i n a Wood's m e t a l m a t r i x . By bombardment w i t h 1.44 MeV d e u t e r i u m t h e ( d , p ) r e a c t i o n p r o d u c t s and PIXE a r e r e g i s t e r e d s i m u l t a n e o u s l y . The l e f t row shows t h e d i s t r i b u t i o n of c a r b o n a s a f u n c t i o n of d e p t h , t a k e n w i t h v a r i o u s g a t e s on t h e p a r t i c l e spectrum: a ) 3.25 < E < 3.4 MeV (0 t o 0.8 pm); b) 3.0 I E

< 3.25 MeV ( 0 . 8 t o 2.1 c ) 2.8 L E

( ~ ? O M ~ V

5 2.8 MeV ( 3 . 2 t o 4.4 urn). The r i g h t rgw shows t h e d i s t r l b u t l o n o f e ) nit?ogt?n (.gate 8.1 < E 1 8 . 9 MeV); f ) t h e Cu K X-rays; g ) t h e Nb K X-rays. An o p t l c a l microphoto o f P t h e specimen s u r f a c e i s g i v e n i n h ) . The f i l a m e n t s a r e i n c l i n e d by

75" r e l a t i v e t o t h e s u r f a c e normal.

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F i g . 2

A n a l y s i s of t h e k i d n e y of a W i s t a r r a t . Along t h e s c a n l i n e t h e t h i c k n e s s of t h e sample and t h e con- c e n t r a t i o n s of some e l e m e n t s a r e g i v e n . A g l o m e r u l u s i s v i s i b l e w i t h i t s c e n t e r 50 pm above t h e m i d d l e of t h e s c a n l i n e . The two pro- nounced d i p s i n t h e d i s - t r i b u t i o n s o f C 1 and K a r e caused by lumina o f p r o x i m a l o r d i s t a l con- v o l u t e d t u b u l e s .

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0,s - thick-

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ness

Acknowledgement

I t h a n k D r . E. R o k i t a , I n s t i - t u t e of P h y s i c s o f t h e J a g e l - l o n i a n U n i v e r s i t y o f Cracow f o r t h e p r e p a r a t i o n and eva- l u a t i o n o f t h e r a t k i d n e y sample.

R e f e r e n c e s

[ l ] Cookson, J. A., Ferguson, A. T. G., F i l l i n g , F. D . , J. R a d i o a n a l . Chem.

12

(1972) 39; Cookson, J. A., McMillan, 3. W . , P i e r c e , T. B . , J. R a d i o a n a l . Chem.

48 (1979) 337.

-

[2] B i r d , J. R., Campbell, B. L . , B r i c e , P . B . , Atomic Energy Rev.

12

[3] J o h a n s s o n , T. B . , A k s e l s s o n , R., J o h a n s s o n , S. A. E . , Nucl. I n s t r . Meth.

84

(1970) 141; Folkmann, F . , J. Phys. E.

8

[4] Heck, D . , B e i t r . e l e k t r o n e n m i k r o s k o p . D i r e k t a b b . O b e r f l .

12

Nucl. I n s t r . Meth.

181

[ 5 ] Heck, D . , R e p o r t KfK 2734 (1978)

161 Heck, D . , Nucl. I n s t r . Meth.

197

171 Heck. D . , R o k i t a , E . , Nucl. I n s t r . Meth. ( i n p r e s s , Febr. 1984)