Range and energy-loss measurement of 238U in Makrofol-N using CR- 39 track detector
A T U L S A X E N A , K K D W l V E D I , R K P O D D A R a n d G F I E D L E R * Department of Chemistry, North-Eastern Hill University, Shillong 793 003, India
*II Physikalisches Institut, Justus-Liebig Universit/it, D-6300. Giessen, West Germany MS received 19 May 1987: revised 9 July 1987
Abstract. A simple experimental technique has been described for measuring range and energy-loss of any heavy ion in any complex medium with the help of a sensitive solid state nuclear track detectors (SSNTDs). In this paper we present the results obtained from our measurements of ranges and energy-toss of 16.34 MeV/u 23~U in Makrofol-N using CR-39 track detector. Experimental ranges are compared with the corresponding theoretical values.
The significance and scope of the present work are discussed.
Keywords. CR-39 detector; energy-loss rate; ranges; Makrofol-N; track length; 238|}.
PACS No. 61-80
1. Introduction
It has been s h o w n earlier (Saxena et al 1985) that a p a r t f r o m several other a p p l i c a t i o n s of S S N T D s , a few sensitive detectors are quite useful to m e a s u r e ranges and energy- loss rate of h e a v y ions in elemental media. Such m e a s u r e m e n t s are possible for all heavy ions whose entire range could be revealed as tracks in the detector foils. A few well-known track detectors such as CR-39, cellulose nitrate, Lexan a n d ZnP-glass are highly sensitive for the detection of heavy ions. These detectors are inexpensive small pieces of either plastic sheets or thin glass plates a n d are easily available. In c o m p a r i s o n to other experimental techniques the one based on these S S N T D s for measuring heavy ion ranges and energy-loss rate is very simple a n d does not involve any sophisticated instrumentation.
In the last couple of years thin sheets of p o l y c a r b o n a t e s have been used to p r o d u c e microfilters a n d single-pore m e m b r a n e s for their r e m a r k a b l e applications in the field of e n v i r o n m e n t a l (Fischer and Spohr 1983 a n d references therein), bio-medical ( R o g g e n k a m p et al 1981) and superfluidity ( G a m o t a 1973). Such devices are p r o d u c e d by b o m b a r d i n g p o l y c a r b o n a t e foils with highly ionizing ions (viz. 23sU) at energies a b o v e 10 M e V / u . Since M a k r o f o l - N is quite suitable for its use in the p r o d u c t i o n o f microfilters a n d single-pore m e m b r a n e s and as no e x p e r i m e n t a l d a t a are available in literature, it is worthwhile to measure energy-loss a n d p e n e t r a t i o n depth of 23sU in M a k r o f o l - N . Here, we present o u r experimental results on ranges a n d energy-loss r a t e of 16.34 M e V / u 238U in M a k r o f o l - N foils employing CR-39 as track detector. An a t t e m p t is also m a d e to c o m p a r e our measured d a t a with the c o r r e s p o n d i n g theore- tical values o b t a i n e d f r o m d a t a tables of Northcliffe a n d Schilling (1970) a n d f r o m s t o p p i n g - p o w e r e q u a t i o n s of Mukherji and N a y a k (1979).
485
486 Atul Saxena et al 2. Experimental
2.1 Preparation of detector and targets
2.1.1 CR-39 detector--Cast sheets of CR-39 are p r o d u c e d from allyl diglycol carbon- ate (composition: C 12 H i sO7 and sp. gr. 1-32 g/ml) a n d are m a n u f a c t u r e d by Homalite C o r p o r a t i o n , Wilmington, Del. (USA). Small d e t e c t o r plates were obtained from commercially available sheets (thickness .~ 1.5 ram) by cutting into the size of 20 x 20 m m 2. After removing the surface protecting layers, these detector plates were washed in warm soap solution and then dried inside a v a c u u m desiccator.
2.1.2 Makrofol-N targets--Makrofol-N (composition:
CI6H1403
and sp. gr.1-23 g/ml) is a trade name of yellow polycarbonate, m a n u f a c t u r e d by Bayer AG, West G e r m a n y . Several rectangular foils in the size of 15 x 20 m m 2 were cut from 20 am thin sheets of Makrofol-N. The stacks of varied thicknesses (20-240 #m) were pre- pared by m o u n t i n g 1 to 12 foils successively on CR-39 detectors. These stacks were then fixed on slide glass backing for irradiation.
2.2 Irradiation
The target-detector assemblies were exposed with a well collimated beam of 16.34 M e V / u 2 3 s u ion at XO channel of U N I L A C , G.S.I., Darmstadt. All irradi- ations were done at an incident angle of 45 ° to the detector surface as shown in figure 1. An o p t i m u m flux of -~ 104 ions/cm 2 was used. A n u m b e r of CR-39 detectors (without target foils) were ~also irradiated under similar conditions with different energies of 2 3 s u to obtain a calibration curve.
2.3 Chemical etching
After irradiation, the target foils of Makrofol-N were r e m o v e d from CR-39 detectors.
The detectors were then etched in 6N N a O H at 55°C for 2 - 4 hr to develop n a r r o w conical tracks. T h e etching was continued till r o u n d e d track tips were observed. After complete etching and thorough washing the detectors were dried under vacuum.
2.4 Measurement of track length
Well defined n a r r o w tracks were observed at o r d i n a r y magnification. Etchable track lengths were measured at r a n d o m all over the d e t e c t o r surface to average out the effects due to non-uniformity of targets. Projected track lengths and diameters were measured at a magnification of 675 x and 1500 x respectively. Using the measured
MAKROFOL-N COLLIMATED ~, HEAVY pNS ~{~.'~/
CR-3g DETECTOR
Figure 1. Schematic diagram showing the irradi- ation of target-detector assembly.
data the true m a x i m u m etchable track lengths were o b t a i n e d from the e q u a t i o n given by Dwivedi a n d M u k h e r j i (1979).
2.5 Detector calibration
CR-39 track detectors were calibrated for energy m e a s u r e m e n t s of 238U in t e r m s of m a x i m u m etchable track lengths. Figure 2 shows the calibration curve of 238 U ion in CR-39 detector. A few high energy points are taken f r o m Dwivedi et al 0986). W i t h the help of this calibration curve the energy of 238U ions has been o b t a i n e d f r o m the values of m a x i m u m etchable track lengths in CR-39.
2.6 Measurement of energy-loss and ranges
An energy-loss curve for a heavy ion in any m e d i u m m a y be constructed by p l o t t i n g ion energy as a function of target thickness. F o r a given target thickness (Ax) the energy lost by a h e a v y ion m a y be o b t a i n e d by
AE=(E,--Ex), (1)
where E i is the initial energy of the ion before entering the foil a n d Ex is the d e g r a d e d energy of the ion after penetrating t h r o u g h the target of thickness Ax. A o n e - dimensional p o l y n o m of third order seems to show a best fit for energy-loss data. By e x t r a p o l a t i o n of the curve till Ex = 0, one can easily o b t a i n the range (R~) of a h e a v y ion of energy El in a n y target. F r o m this range value (Ri), the range R(E) at a n y e n e r g y E m a y simply be o b t a i n e d from
R(E)=R,--x(E), (2)
where x(E) is the target thickness which reduces the ion energy f r o m E~ to E a n d is o b t a i n e d f r o m energy-loss curve.
A
E ~
o- r- o o I-- L
I 1
I I I I i I I I
2 3 8
U in CR-39
o Dwiv~i et al. (19861
i i I I I I J I
/~ 8 12 16
Energy ( NeVlu }
o 1
0 20
Figure 2. A plot showing calibration curve between the energy of 23a U and the measured track length in CR-39.
488 Atul Saxena et al 2.7 Experimental errors
The uncertainties in determining the beam energies are very small (~0.1%). The uniformity of the foils was checked by weighing m e t h o d as well as by Heidenhain depth measuring device with an accuracy of _+ 1 pm. It was f o u n d that the stacks of M a k r o f o l - N targets were uniform within 5%. The s t a n d a r d deviation in track length measurement was found ~ 3/~m.
3. R e s u l t s and discussion
Table 1 lists the values of target thickness (Ax), m a x i m u m etchable track lengths (L) of 23aU ions emerged out through M a k r o f o l - N targets, c o r r e s p o n d i n g ion energies (Ex) obtained from calibration curve (figure 2), total energy (AE) lost by the ions in targets of different thicknesses and experimental ranges along with theoretical values obtained (a) from stopping p o w e r equations of Mukherji and N a y a k (1979) and (b) from data tables of Northcliffe a n d Schilling (1970). An energy-loss curve is drawn between target thickness and ion energy (Ex) and is shown in figure 3. F r o m the energy-loss curve, it has been found that 16.34MeV/u 238U has a range of 2 3 0 + 2 p m in M a k r o f o l - N whereas the maximum etchable track length is measured to be 226 _ 4 pm. This indicates that the entire length of latent tracks are revealed by etching the M a k r o f o l - N foils. Using (2), the ranges of 238U ions are obtained at different energies and are shown in figure 4 along with c o r r e s p o n d i n g theoretical values.
In view of the fact that generally 30-60 #m thick films of different polymers are used for the p r o d u c t i o n of microfilters and single-pore membranes, o u r measured range d a t a predict that uniform microholes in M a k r o f o l - N m a y be p r o d u c e d by 238U ions having initial energies m o r e than 10 MeV/u.
Table 1. Values of Makrofol-N thickness, maximum etchable track length of z3s U ions in CR-39 detector, energy of the transmitted 23su ion, total energy-lost by the ions and the ranges obtained in Makrofol-N.
Target thickness Track length Ion energy
Ax (/~m) L (pm) E~ (MeV/u)
23s U-ranges in Makrofol-N (/~m) Total energy-lost Experimental Theoretical
AE (MeV/u) (present work) (a) (b)
Without target 204 _+ 2 16.34
28-3_+1.4 195-t-3 15-70+0-25
56-6_+2.0 161 +_3 13.00_+0-25
84-9 _+ 2.4 128 + 3 9-95 +_0-26 113"1 _+2.8 104_+3 7.72+-0.27 141.4_+ 3-2 82 _+ 3 5.55 _+0.28 169.7 _+ 3.5 59 +- 3 326 +_ 0.24 198.0_+ 3.7 32__+3 108 _+0.18
226.3_+4.0 14+3 ff32_+0.11
254.6 _+ 4.2 No tracks --
0-0 230-0_ 2-0 223-5 - -
0.64__+0.25 216-0+2-4 215-0 - - 3.34+0.25 176.7+2.8 180-0 - - 6.39+0.26 144.0+3.1 140.0 153.0 8.62__+0.27 118-0+3-4 112'0 120.0 10.79+0.28 90.0_+3.8 89.5 88.0 13.08 +- 0.24 62-0 _+ 4.0 65-0 57.0 15-26-+0.18 28-7___4-2 34-0 27-0 16.02-+0-11 11.3-+4.5 16.0 14.5
(a) Mukherji and Nayak (1979); (b) Northcliffe and Schilling (1970).
' I ~ } ' I
"3 ~ 23aU in M o k r o f o l -
N~" ~ ~ e V /
r -
IJ.I
0 80 180 240
Target thickness (~m)
Figure 3. The energy-Joss curve for 23a U in Makrofol-N. The initial energy (El) of the 23s U is 16.34 MeV/u.
E
" ~ or 0
o1 t- o rr~
| - 238 u
I
in
' I ' I ' I '
M a k r o f o l - N ~-"
/ , / /
/ . /
/ . S / . 4 1
/ /
/~ t / ExperimentQl ]~
/ " /
• f
.4r~" Theoreticol " - .... ( o )
l ) -"
/ - S I r 7
f'~
i I
4
G I I I I I I a
0 8 12 16 2 0
E n e r g y ( MeV/u )
F i g u r e 4. Measured range-energy data are shown along with the theoretical values obtained
from (a) Mukherji and Nayak (1979) and (b) Northcliffe and Schilling (1970).
In the last couple of years, several stopping-power measurements (Varley et al 1976;
Forster et al 1976; G f t t n e r et al 1977; Bimbot et al 1978, 1980, 1986; and Geissel et al 1982) have shown significant discrepancies with the calculated or tabulated values, particularly for heavy ions. F o r example, the tabulated stopping-power values of 84 K r in c a r b o n for 4 to 6 M e V / u obtained from Northcliffe and Schilling (1970) were f o u n d to be 30°,4 lower t h a n the measured values (Bimbot et al 1978) and thus resulted in overestimation of range values. On the other hand, the range values c o m p u t e d from stopping-power equations proposed by Mukherji and Srivastava (1974), Srivastava and Mukherji (1976) and Mukherji and N a y a k (1979) are in g o o d agreement (within 5%) with the measured track lengths for several heavy ions (Tripier et al 1974;
Dwivedi and Mukherji 1979 and Dwivedi et al 1986) in a few track detectors. Here, we c o m p a r e o u r measured ranges of 238U in M a k r o f o l - N with the corresponding theoretical values from Northcliffe and Schilling (1970) and Mukherji and N a y a k (1979). It has been observed that up to about 8 M e V / u the measured ranges are in
490 A t u l S a x e n a e t al
g o o d a g r e e m e n t w i t h t h e v a l u e s d e r i v e d f r o m d a t a t a b l e s o f N o r t h c l i f f e a n d S c h i l l i n g (1970) w h e r e a s a b o v e 8 M e V / u o u r results a r e f a i r l y c o m p a r a b l e w i t h the t h e o r e t i c a l v a l u e s f r o m M u k h e r j i a n d N a y a k (1979).
4. Conclusion
T h e p r e s e n t i n v e s t i g a t i o n offers a s i m p l e a n d f a i r l y a c c u r a t e m e t h o d for m e a s u r i n g e n e r g y - l o s s r a t e a n d r a n g e s o f a n y h e a v y i o n in a n y c o m p l e x m e d i u m u s i n g C R - 3 9 t r a c k d e t e c t o r . W e a l s o p r e s e n t o u r m e a s u r e d r a n g e v a l u e s o f 238U in M a k r o f o l - N u p t o 16.34 M e V / u . F r o m t h e s e results it is o b s e r v e d t h a t z 3 8 u i o n s w i t h e n e r g i e s a b o v e 10 M e V / i a a r e s u i t a b l e t o p r o d u c e m i c r o - f i l t e r s a n d s i n g l e - p o r e m e m b r a n e s u s i n g M a k r o f o l - N films. By c o m p a r i n g o u r m e a s u r e d r a n g e s w i t h t h e c o r r e s p o n d i n g t h e o r e t i c a l v a l u e s , it h a s b e e n f u r t h e r c o n f i r m e d t h a t s t o p p i n g - p o w e r e q u a t i o n s o f M u k h e r j i a n d N a y a k (1979) p r e d i c t m o r e r e l i a b l e r a n g e v a l u e s for h e a v y i o n s in c o m p l e x m e d i a e s p e c i a l l y a b o v e 8 M e V / u .
Acknowledgements
W e w i s h t o t h a n k D r R S p o h r , D r J V e t t e r a n d o t h e r staff m e m b e r s o f G S I , D a r m s t a d t (W. G e r m a n y ) for p r o v i d i n g i r r a d i a t i o n facilities at t h e U N I L A C . W e a l s o t h a n k D A A D ( B o n n , W . G e r m a n y ) a n d U G C ( N e w D e l h i , I n d i a ) for s p o n s o r i n g t h i s w o r k .
References
Bimbot R, Della Negra S, Gardrs D, Gauvin H, Fleury A and Hubert F 1978 Nucl. Instrum. Methods 153 161
Bimbot R, Gardrs D, Geissel H, Kitahara T, •rmbruster P, Fleury A and Hubert F 1980 Nucl. lnstrum.
Methods 174 231
Bimbot R, Gauvin H, Orliange I, Anne R, Bastin G and Hubert F 1986 Nucl. lnstrum. Methods B17 1 Dwivedi K K and Mukherji S 1979 Nucl. lnstrum. Methods 161 317
Dwivedi K K, Saxena A, Crombach P, Reichwein E and Fiedler G 1986 Nucl. Tracks Radiat. Meas. 12 241 Fischer B E and Spohr R 1983 Rev. Mod. Phys. 55 907
Forster J S, Ward D, Andrews H R, Ball G C, Costa G J, Davies W G and Mitchell I 1976 Nucl. Instrum.
Methods 136 349
Gamota G 1973 Phys. Rev. Lett. 31 517
Geissel H, Laichter Y, Schneider W F W and Armbruster P 1982 Nucl. lnstrum. Methods 194 21 Gfittner K, Hofmann S, Marx D, Miinzenberg G and Nickel F 1977 Nucl. lnstrum. Methods 146 413 Mukherji S and Nayak A K 1979 Nucl. lnstrum. Methods 159 421
Mukherji S and Srivastava B K 1974 Phys. Rev. !19 3708 Northcliffe L C and Schilling R F 1970 Nucl. Data tables A7 233
Roggenkamp H G, Kiesewetter H, Spohr R, Dauer U and Busch L C 1981 Biomedizinische Technik 26 167 Saxena A, Dwivedi K K, Reichwein E and Fiedler G 1985 Proc. Radiochem. and Radiat. Chem. Symp.
Kanpur, India 372
Srivastava B K and Mukherji S 1976 Phys. Rev. A14 718
Tripier J, Remy G, Ralarosy J, Debeauvais M, Stein R and Huss D 1974 Nucl. tnstrum. Methods 115 29 Varley G, Willmott J C and Kearns F 1976 Nucl. lnstrum. Methods 135 167
