SECONDARY ELECTRON EMISSION BY LOW ENERGY ION IMPACT

R. MOSHAMMER, R. MATTHÄUS
1989 Le Journal de Physique Colloques  
L ' e f f i c a c i t b d e d e t e c t i o n d e s i o n s a y a n t d e s e n e r g i e s d a n s l e d o m a i n e d u k e V a e t e e s t i m e e e n m e s u r a n t l e n o m b r e d ' e l e c t r o n s e m i s s o u s i m p a c t A p a r t i r d e s u r f a c e s m e t a l l i q u e s r e c o u v e r t e s d e A l z O B e t C s I . L e s e l e c t r o n s s e c o n d a i r e s C t a i e n t a c c e l e r e s a 21 k V e t l e u r s t r a j e c t o i r e s c o u r b e e s p a r u n c h a m
more » ... p a r u n c h a m p m a g n e t i q u e a f i n q u ' i l s p u i s s e n t @ t r e d 6 t e c t e s p a r u n d e t e c t e u r s e m i -c o n d u c t e u r r e f r o i d i . U n e a n a l y s e d e l a f o r m e d e s a m p l i t u d e s d e s i m p u l s i o n s r e c u e i l l i e s a e t 6 f a i t e p a r o r d i n a t e u r . O n t r o u v e q u e l e n o m b r e d ' e l e c t r o n s e m i s d e C s I e s t 1 0 f o i s p l u s g r a n d q u e l e n o m b r e e m i s d e A I Z O a . U n e m a s s e o r g a n i q u e d e 2 0 0 0 J ( g r a m e c i d i n e l p r o d u i t p a r i m p a c t s u r C s I , e n v i r o n 4 0 e l e c t r o n s e t l ' e f f i c a c i t e d e d e t e c t i o n e s t d o n c d e 1 0 0 X . I 1 e s t a u S s i p o s s i b l e p a r c e t t e m e t h o d e d e d i s t i n g u e r u n i m p a c t u n i q u e d e p l u s i e u r s i m p a c t s S i m u l t a n C s p a r l a d e t e r m i n a t f o n d u no,fibt-e d ' h l e c t r o n s e m i s . Abstract In order to estimate the detection efiiciency of ion detectors in the keV regime, the secondary electron yield of metal plates covered by Alz03 and CsI was measured using a 2b2Cf time-of-ilight technique. The mono-and multiatomic ions were produced by 2 6 2~f fission fragment impact on various solid samples and then accelerated by a 21 kV potential towards the metal plate. The secondary electrons ejected from the surface were directed by means of magnetic deflection to a cooled semiconductor detector having a resolution of 6.5 keV at 19 keV electron energy. To deduce the mean number of electrons per impact the pulse height spectrum was defolded with help of a new computer supported formalism. In most cases the spectra could be defolded without a residual backgroundeven at high electron yields, where the events of adjacent electron numbers were not resolvable. It was found that at 21 keV ion energy the number of electrons ejected hom CsI is about one order of magnitude higher than that of A1203. The Gramecidine ( M i l ) ion produces about 40 electrons at CsI, that means, at least up to mass 2000 amu the detection efficiency was dose to 100 %. I t was possible to distinguish between one and two simultanously detected ions of same mass. The relative electron yields plotted versus ion mass were compared with theoretical predictions. In case of multiatomic ions the electron yields are hardly explainable by the sum rule.
doi:10.1051/jphyscol:1989220 fatcat:c57aylviyrgdxndo5oyljstz3e