Computer-aided evaluation of SSNTD

0191-278X/89 $3.00 + .00 © 1989 Pergamon Press plc

Nucl. Tracks Radiat. Meas., Vol. 15, Nos. 1-4, pp. 281-285, 1988 Int. J. Radiat. Appl. lnstrum., PartD Printed in Great Britain

COMPUTER-AIDED E V A L U A T I O N OF SSNTD

WOLFGANG

BIRKHOLZ

University of Technology, Leipzig, Department Kommandant-Trufanow-Str. 2-6, Leipzig

MICHAEL

and

STEINERT

and

PETER

of Natural Sciences 70220 G.D.R.

ST~BE

A c a d e m y of S c i e n c e s of the GDR, C e n t r a l I n s t i t u t e for Radiation Research, Leipzig, Permoser Str. 15, L e i p z i g

STANISLAV Ooint

Institute

G.

Stetsenko

and

VLADIMIR

P.

Isotope 7050, G.D.R.

PERELYGIN

for Nuclear Research, Laboratory of 101000 Moscow, P.O.Box 79 U.S.S.R.

Nuclear

Reactions

Abstract - T h e DENSITRON 4H i m a g e a n a l y z i n g system developed at the Central Institute for Isotope and Radiation Research Leipzig, was m o d i f i e d for the search, counting end measurement of tracks i n SSNTD a t t h e 3 o i n t Institute for Nuclear Research Dubne. A microscope was c o m p l e t e d by stepping motors for moving the x-, y- and z-coordinates. The c o n t r o l of the motors is done by the microcomputer of the DENSITRON 4M s y s t e m . For track detector evaluation special subroutines were linked to the software.

KEYWORDS autofocus, automatic measurement system, image analysis, heavy ionS. particle tracks, nuclear track detectors

computerized solid state

INTRODUCTION Evaluation is the bottle-neck in many applications of solid state nuclear track detectors (SSNTD). The s c a n n i n g of large areas, track counting and measurement w i t h an o p t i c a l m i c r o s c o p e are t r o u b l e s o m e and time consuming. Therefore some laboratories developed instruments suituable for SSNTD evaluation or u s e d c o m m e r c i a l equipments such as O u a n t i m e t , Videomat, Classimat, Hegiscan a n d o t h e r s /1/,/2/,/3/. For many years instruments for the evaluation of eutoradiograms have been developed at the Central Institute for Isotope and Radiation Research, Leipzig (ZfI). The l a t e s t o n e i s t h e DENSITRON 4 s y s t e m , e digital software controlled image analyzer / 4 / , / 5 / . Parallel to the m o d e l for s e r i e s p r o d u c t i o n in the Centre for the Manufacture of S c i e n t i f i c Instruments of the A c a d e m y of S c i e n c e s of the GDR a modified system DENSITRON 4N', for track measurements in SSNTD in the Laboratory of Nuclear Reactions of the 3oint Institute for Nuclear Research 3INR),Dubna, was b u i l t by the ZfI. THE SYSTEM The scanning of the image is done by a black-and-white TV camera (UFK 1 2 , Studiotechnik RFA 4010). F o r SSNTD e v a l u a t i o n t h e TV c a m e r a is a d d e d to an o p t i c a l m i c r o s c o p e (Ergaval, C a r l Zeiss, O e n a ) . D u r i n g 40 ms one TV p i c t u r e is d i g i t i z e d with a resolution of 5 b i t s ( c o r r e s p o n d i n g 64 g r e y levels) end written in e g r a p h i c c o n t r o l unit (GSE) with a memory of 5 1 2 x 7 6 8 p i x e l s size (8 b i t s ) . This m e a n s 6 b i t s are u s e d for p i c t u r e i n f o r 281

282

W. B I R K H O L Z et al.

mation and 2 bits are free for additional texts or graphics. The GSE a l l o w s ZOOH', w i n d o w and c u r s o r functions by the hardware. The i n f o r m a t i o n stored in the m e m o r y can be r e a d out through "look-up tables" and written over three digital/analog converters as R G B - s i g n a l s on a c o l o u r TV monitor. It is possible to code the pictures by colours, manipulate the information (e.g. contrast, logarithm, a.o.) without changing the contents of the memory. The control of the system and picture processing i s d o n e by a p e r s o n a l computer (Robotron A 5 1 2 0 , PC 1 7 1 5 ) with minifloppy disks. For automatic SSNTD e v a l u a t i o n the optical microscope was modified by adding s t e p p i n g motors (100 s t e p s per r e v o l u t i o n ) f o r moving the o b j e c t in the x - and y-directions ( 1 2 . 5 pm per s t e p ) and the focus (z-direction, 0.5 pm per s t e p ) . The c o n t r o l of the motors i s done by a s p e c i a l i n t e r f a c e of the PC. This m o d i f i e d system i s c a l l e d "DENSITRON 4 H ' . Fig. 1 shows the b l o c k scheme and f i g s . 2 and 3 a r e p h o t o g r a p h s of the DENSITRON 4H.

FK ADC GSE FD H HR HFD [] T

TV c a m a r a anal./dig, converter grapic unit / memory colour display stepping motors microprocessor minifloppy drives printer key-board @

Fig.

1

Block image

scheme of processing

the digital, system.

interactive

DENSITRON

4H

Fig.

2

Densitron 4H at the JINR

Fig.

3

Hicroscope with stepping motors

COMPUTER-AIDED EVALUATION OF SSNTD

283

SOFTWARE The DENSITRON 4H i s an i n t e r a c t i v e system for image analysis. Special knowledge of p r o g r a m m i n g is n o t n e c e s s a r y for the u s e r . All functions are controlled by a global m e n u . A f t e r selection of a s p e c i a l function submenues l e a d the u s e r . A s e l e c t e d a l g o r i t h m of e v a l u a t i o n by d i f f e r e n t functions can be stored and r e p e a t e d . For t r a c k m e a s u r e m e n t the p r o g r a m "evaluation of autoradiogram" was modified. The video

main

functions a r e :

input

Reading of p i c t u r e s f r o m the TV c a m e r a i n t o the memory. The w h o l e m e m o r y m a y be d i v i d e d into 7 sections. 6 sections with a size of 256x256 pixels and one with 512x512 pixels (overlay with 4 smaller sections). Hoving of the stepping motors by the key-board.

mask

Definition of s i z e a n d p o s i t i o n ture, measurements by a c u r s o r . carried out i n s i d e of the f r a m e .

greywedge, c a l i b r a tion, contrast man i p u l a t ion

C a l i b r a t i o n of geometric and o p t i c a l d e n s i t y for t a t i v e measurements.

equidensite, isohel

Marking of p o i n t s of equal o p t i c a l d e n s i t y by equidens i t e s and t r a n s f o r m i n g the p i c t u r e by pseudocolours.

storage

Storage and r e a d i n g disk .

text,

histogram

autofocus

The functions

-

quanti

d i g i t i s e d p i c t u r e s on m i n i f l o p p y

Adding t e x t to the p i c t u r e ' , c a l c u l a t i o n of a histogram of the o p t i c a l d e n s i t y of the p i c t u r e and drawing i t on the TV m o n i t o r . Measuring of the c o n t r a s t in the p i c t u r e by changing the focus plane w i t h the stepping motor and f i x i n g the focus in the plane w i t h the highest c o n t r a s t .

programs of the evaluation functions may be l i n k e d to the system.

Some examples w i l l SSNTD e v a l u a t i o n . -

of

of a f r a m e in the picAll other functions are

are

written

EXPERIMENTS i l l u s t r a t e the p o s s i b i l i t i e s

of

in

BASIC.

User

the DENSITRON 4H f o r

Coun tin~ of track density F o r many a p p l i c a t i o n s it is necessary to count the track density in different areas. If there are tracks with t h e same s h a p e , e.g, in the irradiation of SSNTD with heavy ions at a definite angle of incidence, the relative track density c a n be m e a s u r e d by the summation of the track covered-area in a frame. Fig. 4 shows U-238 tracks (8.6 MeV/amu, UNILAC, GSI Darmstadt) in glass detectors irradiated perpendicular, and their representation in a binary picture on t h e TV m o n i t o r , The r e l a t i o n between the track density counted with an o p t i c a l microscope and the area covered with tracks in a frame measured with t h e DENSITRON 4M is drawn in fig. 5. Heavy ion experiments i n t h e OlNR a r e e v a l u a t e d by this calibration. The m e a s u r i n g t i m e was s h o r t e n e d to 1/10 compared with optical track counting, The t r a c k density d a t a o f m a n y a r e a s may be s t o r e d and evaluated directly with t h e PC o f t h e DENSITRON 4M. Measurement of track parameters In heavy ion experiments the measurement of the length', diameter and depth of volume tracks is of interest. With the help of the cursor and changing the focus plane by the stepping motor one can measure the track parameters i n an e a s y w a y . By c a l i b r a t i o n of the optical magnification quantitative values are printed on t h e TV s c r e e n . Fig. 6 gives an i m p r e s s i o n of measured track parameters of Ne-22 tracks (8.6 MeV/amu, U 400 3INR Dubna) in CR-39, angle of incidence lO o. For etching t h e Ne v o l u m e t r a c k s with the track in track method (TINT) an a d d i t i o n a l , perpendicular irradiation was carried out.

284

-

W. BIRKHOLZ et al.

S e a r c h of r a r e n u c l e a r events The s e a r c h of r a r e e v e n t s in heavy ion physics experiments, e.g., the synthesis of transuranium elements or the study o f new k i n d s of radioactivity, s u c h ms c l u s t e r emission is v e r y monotonous and f a t i g u i n g work /6/. A single track with a typical structure m u s t be f o u n d i n a b a c k g r o u n d of other tracks on a l a r g e area. Fig. 7 shows, that it is possible to discriminate between single fission tracks end t h e h i g h n o i s e of recoil tracks with t h e DENSITRON 4H ( A 1 - 2 7 track, 2.5 HeV/amu, angle of incidence 30 ° , U 400,

additional

The s y s t e m nates of events and

irradiation

of

lollcm

scanned the whole detector events of interest. In a the operator could identify

0

w

W

~

-2

alpha-particles,

automatically second run the the tracks.

SSNTD

Maline×).

end s t o r e d the system repeated

I

tr

%,.

|

O ~!i~ ~iii~' ~i~ ~ii~ii, ii~,

0 i @ @

%

Fig.

< uJ tY <

4

U-238

tracks

in

glass

SSNTD

30 20 10 0

I0 NUHBER

Fig . 5

I

I

I

I

I

20

30

40

50

60

OF TRACKS

/ARBITRARY

U N I TS

Basic relation between track-covered area in a binary picture and optically counted track density. The steep decrease at high track density depends on the overlapping of tracks and t h e change of the transparency in t h i s region.

coordithese

COMPUTER-AIDED E V A L U A T I O N OF SSNTD

F i g . 6 Measurement of t r a c k parameters with the DENSITRON 4H

Fig. single picture

7

285

Identification of tracks by a binary

CONCLUSION The e x p e r i m e n t s c a r r i e d out w i t h the i n t e r a c t i v e DENSITRON 4H image p r o c e s s i n g system demonstrate the a p t i t u d e of t h i s system f o r SSNTD e v a l u a t i o n , e s p e c i a l l y in c o n n e c t i o n w i t h a s t e p p i n g motor d r i v e n m i c r o s c o p e . They showed t h a t the measuring time can be s h o r t e n e d and t e d i o u s work in the l a b o r a t o r y can be a b o l i s h e d . Further programs f o r t r a c k measurements, e.g. the i d e n t i f i c a t i o n of c l u s t e r s of t r a c k s , d i f f e r e n t scanning p r o c e d u r e s , the c a l c u l a t i o n of h i s t o grams, etc. are b e i n g developed a t the C e n t r a l I n s t i t u t e for Isotope and R a d i a t i o n Research, L e i p z i g .

Acknowledgements We a r e i n d e b t e d to Mrs. U. Birkholz, Mrs. G.P. BugrOVo who t o o k p a r t i n t h e e x p e r i m e n t s , and t h e s t a f f s i n D a r m s t a d t and Dubna, who c a r r i e d out the irradiations.

K n a s e v a , and M r . Yu. of t h e a c c e l e r a t o r s

REFERENCES /1/ /2/ /3/ /4/ /5/ /6/

RT I$Sl/4--T

Staderini, E.M.0 C a s t e l l a n o , A. N u c l . T r a c k s 12 ( 1 9 8 6 ) 2 2 1 - 2 2 5 Fews. A . P . N u c l e a r T r a c k s 12 ( 1 9 8 6 ) 2 2 1 - 2 2 5 Dreute, 3. e t 8 1 . N u c l e a r T r a c k s 12 ( 1 9 8 6 ) 2 6 1 - 2 6 4 Birkholz, W., F r e y e r , K. O. R a d i o s n a l . Chem. 79 ( 1 9 8 3 ) 2 4 5 - 2 5 4 Steinert, M. e t a l . I s o t o p e n p r a x i s in press B i r k h o l z . W Z f I - H i t t e i l u n g e n (1985) 103, 119-123