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A fast, low cost LR-115 hole counter
0735-245X/91 $3.00+ .00 pergamon Press plc
Nucl. Tracks Radiat. Meas., Vol. 19, Nos 1--4,pp. 249-250, 1991 Int. J. Radiat. Appl. Instrum., Part D
Printed in Great Britain
A FAST, LOW COST LR-II5 HOLE COUNTER A. Drsgu Metrologicsl Laboratory, Institute for Nuclear Physics and Engineering, M~gurele P.O. Box MG-6 Bucharest, Romania
ABSTRACT A Vitatron densitometer was modified to get m fast ~R-II5 etched-through t r a c k c o u n t e r . The m o v i n g m a g n i f i e d h o l e i m a g e i s p r o j e c t e d on a p h o t o m u l t ~ p l i e r and t h e r e s u l t e d i m p u l s e s , a f t e r e l e c t r o n i c processing, are counted b~ a n u s u a l s c a l e r . KEYWORDS LR-115 t ~ p e I I , e t c h e d - t h r o u g h t r a c k s , impulses, statistical counting.
mechanical scanning,
gaussian
shaped
INTRODUCTION Ten ~ e a r s ago a method b a s e d o n a p h o t o m u l t i p l i e T t r a c k c o u n t i n g s ~ s t e m was t e s t e d . B u t u n l i k e Nashemi Nezhad and Nami, i 9 8 6 , w h i c h used e R e i c h a r t p h o t o m i c r o e c o p e , t h i s method t o o k a d v a n t a g e o f t h e p o s s i b i l i t i e s of a Carl Zeiss Jena recording miorodensitometer, Being adapted to get hole area distributions. Though c h e a p and s e m i - a u t o m a t i c , t h e s ~ s t e m was v e r y s l o w . A V i t a t r o n d e n s i t o m e t e r was m o d i f i e d and i t r e s u l t e d a f a s t and low c o s t h o l e counter.
DESCRIPTION OP EQUIPMENT The three main interacting s~stems, of the device sketched in Fig. I, are: mechanics, optics, electronics. M,w, ~
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L 5£ANXJ~iG
I
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Fig.l.General sketch of the device : ?:oving table, optical system, electronics,..., evaluation. 249
250
A. DRAGU
Mechanical
s~stem
A m o v i n g t a b l e , p e n d u l a t i n g w i t h a f r e q u e n c ~ o f 5 Hz and a n a m p l i t u d e d e p e n ding on the detector width, has in its center the detector support that c a n b e r o t a t e d i n t h e d e t e c t o r p l a n e i n f o u r b~ 90 ° d e l a y e d p o s i t i o n s . The o p t i c a l s ~ s t e m i s m o u n t e d on a n i n d e p e n d e n t l ~ m o v i n g s t a g e h a v i n g a l s o a n a u t o r e v e r s e movement i n a p e r p e n d i c u l a r direction on t h a t o f t h e t a b l e and a s p e e d o f 1 c m / m i n . The r e s u l t o f t h e s e two i n d e p e n d e n t m o v e m e n t s i s a continous scanning of the detector with a line width of 35 um. Optical s~stem It consists of: power light source, condenser, filter, objective, diaphragms and photomultiplier. The best fit between the photomultiplier sensitivity and t h e r e d d e t e c t o r u n d e r g r o u n d i s a n i n t e r f e r e n c e filter with a p a s s b a n d a r o u n d 526 ~ n . The m a g n i f i e d p r o j e c t i o n of the "viewed" detector z o n e on t h e p h o t o m u l t i ~ l i e r e n t r a n c e i s l i m i t e d b~ a n o p t i c a l d i a p h r a g m . From t h e i n t e r s e c t i o n of moving hole projection and p h o t o m u l t i p l i e r circul a r diaphragm results slow, gaussian-sha~ed, light impulses. Electronics Slope improvement, discrimination and c o u n t i n g a r e t h e s t e p s p a s s e d b~ t h e electric impulses from the photomultiplier to the printer. At e v e r ~ s t r o k e end o f t h e m o v i n g o p t i c a l s ~ s t e m , t h e number o f c o u n t e d i m p u l s e s a r e p r i n t e d . The main parameters of the device are listed in Table I. Table i. Main parameters of the device Hole diameter: ~0 ~ 35 ~_ 2 Liniarit~: 0 holes/cm Counting area speed: I mm /s Efficiency: 0 - I00 % EVALUATION Calibration From the scanning movement represented in Fig. I, it results that the LR-II5 etched-through detector will be twice counted. To avoid over or underevaluation of hole number a standard microscope counted probe is used. Statistics Though individuall~ counted, etched-through tracks are subject to statistical laws. To achieve low errors the detectors will be counted i0 - 20 times in four, b~ 90 ° delayed positions. Gross errors from the printed results are eliminated b~ a computer program using the Grubbs-Smirnov criterion. Overlapping holes are counted as single events but can be electronically discriminated. CONCLUSION A fast, low-cost and high reproducible LR-115 hole counter was presented. Being and adaptation of a different aimed tool, the system has important dimensions, weight and is unmovable. But with a special particular design and microprocessor analysis, 20 - 30 detectors could be counted at once, such a portable device having the dimensions of a casetterecorder. REFERENCE ~ashemi Nezhad, S.R. and F.Nami (1986). A Photomultiplier based track counting system. Proc. 13 Int.Conf. on Solid State Nuclear Track Detectors, Rome. Pergamon Press, 295.
Nucl. Tracks Radiat. Meas., Vol. 19, Nos 1--4,pp. 249-250, 1991 Int. J. Radiat. Appl. Instrum., Part D
Printed in Great Britain
A FAST, LOW COST LR-II5 HOLE COUNTER A. Drsgu Metrologicsl Laboratory, Institute for Nuclear Physics and Engineering, M~gurele P.O. Box MG-6 Bucharest, Romania
ABSTRACT A Vitatron densitometer was modified to get m fast ~R-II5 etched-through t r a c k c o u n t e r . The m o v i n g m a g n i f i e d h o l e i m a g e i s p r o j e c t e d on a p h o t o m u l t ~ p l i e r and t h e r e s u l t e d i m p u l s e s , a f t e r e l e c t r o n i c processing, are counted b~ a n u s u a l s c a l e r . KEYWORDS LR-115 t ~ p e I I , e t c h e d - t h r o u g h t r a c k s , impulses, statistical counting.
mechanical scanning,
gaussian
shaped
INTRODUCTION Ten ~ e a r s ago a method b a s e d o n a p h o t o m u l t i p l i e T t r a c k c o u n t i n g s ~ s t e m was t e s t e d . B u t u n l i k e Nashemi Nezhad and Nami, i 9 8 6 , w h i c h used e R e i c h a r t p h o t o m i c r o e c o p e , t h i s method t o o k a d v a n t a g e o f t h e p o s s i b i l i t i e s of a Carl Zeiss Jena recording miorodensitometer, Being adapted to get hole area distributions. Though c h e a p and s e m i - a u t o m a t i c , t h e s ~ s t e m was v e r y s l o w . A V i t a t r o n d e n s i t o m e t e r was m o d i f i e d and i t r e s u l t e d a f a s t and low c o s t h o l e counter.
DESCRIPTION OP EQUIPMENT The three main interacting s~stems, of the device sketched in Fig. I, are: mechanics, optics, electronics. M,w, ~
- qco.pu~-u I / ~"nsI
L 5£ANXJ~iG
I
I
Fig.l.General sketch of the device : ?:oving table, optical system, electronics,..., evaluation. 249
250
A. DRAGU
Mechanical
s~stem
A m o v i n g t a b l e , p e n d u l a t i n g w i t h a f r e q u e n c ~ o f 5 Hz and a n a m p l i t u d e d e p e n ding on the detector width, has in its center the detector support that c a n b e r o t a t e d i n t h e d e t e c t o r p l a n e i n f o u r b~ 90 ° d e l a y e d p o s i t i o n s . The o p t i c a l s ~ s t e m i s m o u n t e d on a n i n d e p e n d e n t l ~ m o v i n g s t a g e h a v i n g a l s o a n a u t o r e v e r s e movement i n a p e r p e n d i c u l a r direction on t h a t o f t h e t a b l e and a s p e e d o f 1 c m / m i n . The r e s u l t o f t h e s e two i n d e p e n d e n t m o v e m e n t s i s a continous scanning of the detector with a line width of 35 um. Optical s~stem It consists of: power light source, condenser, filter, objective, diaphragms and photomultiplier. The best fit between the photomultiplier sensitivity and t h e r e d d e t e c t o r u n d e r g r o u n d i s a n i n t e r f e r e n c e filter with a p a s s b a n d a r o u n d 526 ~ n . The m a g n i f i e d p r o j e c t i o n of the "viewed" detector z o n e on t h e p h o t o m u l t i ~ l i e r e n t r a n c e i s l i m i t e d b~ a n o p t i c a l d i a p h r a g m . From t h e i n t e r s e c t i o n of moving hole projection and p h o t o m u l t i p l i e r circul a r diaphragm results slow, gaussian-sha~ed, light impulses. Electronics Slope improvement, discrimination and c o u n t i n g a r e t h e s t e p s p a s s e d b~ t h e electric impulses from the photomultiplier to the printer. At e v e r ~ s t r o k e end o f t h e m o v i n g o p t i c a l s ~ s t e m , t h e number o f c o u n t e d i m p u l s e s a r e p r i n t e d . The main parameters of the device are listed in Table I. Table i. Main parameters of the device Hole diameter: ~0 ~ 35 ~_ 2 Liniarit~: 0 holes/cm Counting area speed: I mm /s Efficiency: 0 - I00 % EVALUATION Calibration From the scanning movement represented in Fig. I, it results that the LR-II5 etched-through detector will be twice counted. To avoid over or underevaluation of hole number a standard microscope counted probe is used. Statistics Though individuall~ counted, etched-through tracks are subject to statistical laws. To achieve low errors the detectors will be counted i0 - 20 times in four, b~ 90 ° delayed positions. Gross errors from the printed results are eliminated b~ a computer program using the Grubbs-Smirnov criterion. Overlapping holes are counted as single events but can be electronically discriminated. CONCLUSION A fast, low-cost and high reproducible LR-115 hole counter was presented. Being and adaptation of a different aimed tool, the system has important dimensions, weight and is unmovable. But with a special particular design and microprocessor analysis, 20 - 30 detectors could be counted at once, such a portable device having the dimensions of a casetterecorder. REFERENCE ~ashemi Nezhad, S.R. and F.Nami (1986). A Photomultiplier based track counting system. Proc. 13 Int.Conf. on Solid State Nuclear Track Detectors, Rome. Pergamon Press, 295.