Singh, Th Basanta

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,„JianJ. Phys. 75A (3). 229-232 (2001)U P  A— an international lournalComputerised glow curve deconvolution (CGCD) : the case of TLD-300Th Basanta Singh ;Depannient of Physics,- Manipur University, lmphal-795 |K)3, IndiaE-inail • basanta 123 <i3>rcdiff|com R e c e iv e d  I I  A uf> ust 2 0 0 0 , a c c e p te d  O c to b e r  2 0 0 0Abstract Computerised glow curve deconvolution (CGCD) in principle can provide meaningful and unique trapping parameters piovided oneuses the correct model in simulating the numerical glow peaks. In the absence ol the knowledge of the exact model, simple models like the one used in kindles formalism can still yield trapping parameters dcHncd at least semiquaniitalively. This has been shown by deconvoluting three glow curves (two line to Y and one due to a-irradiation) of TLD-300 (CaF, . Tin)The importance ol peak finding by second denvativc plot of the glow curve is demonstrated. It has been found that all the glow peaks do not follow fust order kinetics.Keywords Thermolumincsccncc (TL), activation energy, figure of merit (FOM) l*A(\S Nos. 78 60 Kn, 84 60 Bk1. Introduction( ompuleriscd glow curve deconvolution (CGCD) technique is now widely used in various areas of thermoluminescence (TL) studies and is well documented fl,2]. At the present state of ilevelopmcnt, CGCD in general, is performed in the framework nl kinetics formalism 13-5].In this paper, we would like to discuss the application of CTjCD in establishing the trapping parameters of TLD~300 (CaFj Tin). The selection of the material is based on the fact that a number of workers have applied CGCD to the glow peaks of this material [6 -8 ], Further, ever since its introduction to the family of TLDs [91, the material remains a candidate in mixed radiation field dosimetry on the ground that its major peaks, namely 3 and 5, show different response to linear energy transfer (LET: defined as dB/dl where dE is the energy loss by a charged particle travelling a distance dl, due to collisions) of the radiation.Our study is based on CGCD of two glow curves of 'FLD- ^00, one irradiated by y-rays and the other by a-rays. The data are taken from the paper of Olko [10]. We have performed CGCDa glow curve of Bos and Dielhof [8 ] as well, not only to check <^ur deconvolution technique but to establish the trapping parameters of the glow peaks at least semiquantitatively. The COCD software used in the present work is essentially the one presented in the book of Chen and Kirsh [11]. The onlym odification incorporated is the selection of the peak temperature (Tm) within ± L'C. The criterion for the best fit with a specific set of the activation energy (E), the frequency factor (s), the order of kinetics (b) is judged from the minimum value ol the root mean square deviations.2. Results and discussionThe results of CGCD of the glow curves of TTD-300 arc shown in Figures 1 and 2. The goodne.ss of fit is checked by the value of the Figure of Merit (FOM) which is defined as follows :FOM:■yUj)xlO O,whereFOMJ  s ta rt ^  s to py(^/)Figure of Merit in per cent, first channel in fitting region, last channel in fitting region, content of channelvalue of fitting function in the middle of channel 7 ,the integral of the fitted glow curve.C>2(X)1 lACS230 Th Basanta SinghThe FOM first proposed by Misra and Eddy f 12] has become not only popular but acceptable by the community of CGCD workers where FOM values of a few percent is taken as an acceptable fit 113]. In both cases, the fitting is good in the senseIn an attempt to lend further support to our result wc h iv, plotted the second derivative of the Y‘in*adiated glovv cui\ which is supposed to reveal four negative peaks cao- corresponding to one of the four glow peaks. The result is sh)\u)Figure 1, CGCD results of Y-itradiatcd glow curve of TLD-3(K) of Olko 1101. The FOM value obtained is 0.03068% o o o Expemncnlal data. Best-fit glow peaks. ~~ Sum of best-fit glow peaksthat for y-irradiated glow curve the FOM = 0.03068% whereas that for a-irradiaicd one FOM = 0.01367%. The values of the trapping parameters for the best-fit deconvolutcd constituent peaks are presented in Table I. Unlike the case of Bos and Dielhof[8 ] our results show that not all peaks do follow first order kinetics.Table 1. CGCD result of TLD-300 (CaF, Tm)Figure 2. CGCD re.sulls o f fx-irradiated glow curve of TLI>-30() of ()||,„ flO]. The FOM value obtained is 0.01367%. o o o Experimenui ijjia — Bcsi fit glow peaks — vSuin ol best-tit glow peaksin Figure 3 along with the deconvolutcd bcst-fit peaks. Theic is a close agreement between the peak temperature with thai oi the negative peaks of second derivative plot of the glow ait\c This result provides physical basis to the location of glow pc\ik temperature (Tin), a point not checked in CGCD.GlowpeakT,„ C’C) E(eV) s(s-') Order of kineticsRcl Glow cui-ve1 088 00 0 740 1 4 X lO' 1 Bos Sc Dielhof f8]1.00 ± 0.07 1.0 X  10" *2 1 10 79 1 036 3 X lO'- 1 Bos & Dielhof [8J108 ± 0  09 .3 0 X 10" *171.38 1.198 .5.4 X  10" I Y-irradiated, Olko flO]3 170 48 1.186 4 1 X 10'-’ 1 5 a-irradiatecf Olko (lOJ\ 5 2  01 1 132 1.9 X 10"- 1 Bos & Dielhof [8|1.22 ± 0.04 (3 ± 2) X 10" ♦208 .86 I 051 1 0 X 10" 1 Y'irradiated. Olko [10]4 207 72 1.079 2 2  X 10" 1 a-irradiated, Olko [10]192.65 1 199 6 1 X 10" 1 Bos Sc Dielhof [8]1,37 ± 0.03 (7 ± 4) X  10" 0258.98 1 528 3.7 X 10" 1 5 Y'lrradiated, Olko [lOJ5 2.56 95 1.592 1.8 X 10" 1.5 a-irradiated, ('llko [lO]239.98 1.583 2 4  X 10" 1.5 Bos &  Dielhof 18]1.74 ± 0.04 (1 3 ± 0.6) X 10" 0295 .00 1 821 1.9 X 10" 1 Y-irradiated. Olko (lOJ6 291 .59 1.890 1.0 X lO'* 1 «-irradiated, Olko jlOJ275 .40 1 951 6 4  X  lO" 1 Bos & Dielhof |8]1.88 ± 0  02 (.5*3) X lO" 0• Result of Bos &. Dielhof [KJ (Various heating rates method)Computerised glow cun>e deconvolution (CGCD): the case ofTLD-300ii)231In order to lend further support to our CGCD results, we h ivc applied the technique to a glow curve of Bos and DielhofIn the process of fitting, the entire glow curve ol TLD-300 to first order peaks Bos and Dielhof (8 ] have failed to locate the exact glow peak temperatures. ITiis has resulted m the large discrepancy between the VHR and CGCD results for the 2nd and 6 th peak.6 - |2  H- 2  - 6  -JT("C)I ijiure 3. Scconil derivative plot of the glow curve (Figure I) aliing with’hr bc'Nt 111 glow peaks.1 K |  (figure 4). The results of the deconvolution are presented m Kible 1 for comparison. The results are in good agreement, fuiilicr. the plot of the second derivative of the glow curve along with the peak temperature of the best fit glow curves (asI'lRurc 4. CGCD result ;^ of y-irradiatcd glow curve of TLD*300 of Bos ‘inil Dielhof (8J The FOM value obtained is 0 02341%  o o o -  l^^pcmnental data — Best-fit glow peaks. — Sum of best-fit glow peaks'^hiained by us) shows very good correlation justifying the present analysis (Figure 5). In the same figure, the Tm's of the i i^cconvoluied peaks reported by Bos and Dielhof [8 ] are also biarkcd which shows that the location of the 2 nd and 6 th peak ^dier by 6 ^C and 17®C when compared to negative maxima of the second derivative plot.Conclusionfhus we conclude that0 Not all the glow peaks of TLD-300 follow first order kinetics.Figure 5. Second denvaiivc plot of the glow curve (Figure 4) along with peak tein{x:ru(urc (Tm) markers ^  ^  ^  - Tm's of present deeonvolulion •  • •  - Tin’s icpotled by Bos and Dielhof [8|lii) Hven when the fit between the experimental and numerically generated curve is deceptively prcci.se, CGCD docs not guarantee meaningful data.iv) The second derivative plot of a glow curve can guide one to locate the glow peak temperaturesv) Kinetics formalism may not be the exact model but it gives a fairly good mathematical description of the phenomena, use of which in CGCD can provide trapping param eters reliable at least semiquantitatively. Thus, one can measure the areas of peaks 3 and 5 accurately by resorting to CGCD which will provide valuable information on the radiation quality in mixed radiation fields.AcknowledgmentThe author is grateful to Prof. R. K. Gartia for suggesting the problem. This work is carried out under the DST, New Delhi Project "Seismic Hazard Evaluation in Manipur : An Application ofTL Dating in Paleoscismicity",R e f e r e n c e s|1J Y S Horowitz, and D Yossian R a d ia t  R io t.  D o .\im  60. 1 (1995)[2] S W S M cKeever, M M oscovitch and P D Townsend T h e n n n tu m in e s r m c e  D o s im e tr y  M a te r ia ls  . P r o p e r t i e s  a n d  U se s  { N u c le a r  T ech , P u b . A s h fo r d ,  Kent, England) (1995)[3] J T Randall and M H F Wilkins P r o c .  K o \  S o c  A184 366 (1945)(4J G F J Garlick and A F Gibson P r o c  P h y s  S o c .  60 574 (1948)[5] R Chen J  E l e c t r o v h e m  S o c .  t l6  1254 (1969)[6] J Azonn, C Furetta and A Gutierrez J. P h y s .  D 2 2  458 (1989)232 Th Basanta Singh|7] G Bacci, P Bcmardini, A  Di Domcnicc, C Furelta and B Rispoli Nuclear Instrum Meth, A286 295 (1990)[8] A  J J Bos and J B Dielhof Rndinf Proi. Dosim 37(4) 231 (1991)[9] A C Lucas and B M Kapsar Proc Fifth h i. Cimf. On Luminescence Dosimetry (Sao Paulo, Brazil) (FR G  Physikalischcs Institut., Giessen) p i31 (1977)110) P Olko Radial. Meas. 29 383 (1998)[11]  R Chen and Y  Kirsh in Amlysis of Thermally Stimulated /'m (O xford : Pergamon) p329 (1981)[12] S K Misra and N W Eddy Nucl. lustrum Meth I6ft 'll (1979)[13] R Chen and S W S McKcever Theory of Thermolumlll,'<.^^ .,|^and Related Phenomena (Singapore; World Scieniifiu r  (1997)

Computerised Glow Curve Deconvolution (CGCd) : The Case of TLD-300

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Computerised Glow Curve Deconvolution (CGCd) : The Case of TLD-300

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