- Email: [email protected]
Thermal quenching of thermoluminescence in TLD-200, TLD-300 and TLD-400 after β-irradiation
Physica B 406 (2011) 537–540
Contents lists available at ScienceDirect
Physica B journal homepage: www.elsevier.com/locate/physb
Thermal quenching of thermoluminescence in TLD-200, TLD-300 and TLD-400 after b-irradiation Vural E. Kafadar Department of Engineering Physics, University of Gaziantep, 27310 Gaziantep, Turkey
a r t i c l e in f o
abstract
Article history: Received 19 August 2010 Received in revised form 9 November 2010 Accepted 10 November 2010
The dosimetric characteristics of many TL materials are influenced by changes in location, size and shape of the glow curves due to changes in the heating rate. In this study, the effect of heating rate on the integrated peak areas of CaF2:Dy (TLD-200), CaF2:Tm (TLD-300) and CaF2:Mn (TLD-400) crystals have been investigated after b-irradiation. It was observed that the peak temperatures of all peaks shifted to the high temperature sides and the integrated peak areas decrease as the heating rate increases due to thermal quenching, whose efficiency increases as temperature increases. & 2010 Elsevier B.V. All rights reserved.
Keywords: Thermal quenching TLD-200 TLD-300 TLD-400
1. Introduction Thermoluminescence in solids is the emission of light from an insulator or semiconductor, which takes place during the heating of a solid, following an earlier absorption of energy from radiation [1,2]. In thermoluminescence (TL), the glow curve is affected by some experimental parameters. Heating rate is one of the most important experimental variables, which changes the glow curve shape [3]. In TL dosimetry, the absorbed dose and TL intensity are affected by changes in the heating rate [4,5]. Many investigations have been carried out by scientists in order to understand that how the TL glow curve changes under different heating rates [5–8]. Taylor and Lilley [5] pointed out that changes in intensity, caused by the change in heating rate, may have a bearing on the determination of trapping parameters E (trap depth) and s (frequency factor). As a result of many studies, a decrease in TL intensity was observed with increase in the heating rate. This phenomenon has been explained to be due to thermal quenching, whose efficiency increases as temperature increases [8].
2. Experimental procedure The samples used in this study were CaF2:Dy (TLD-200), CaF2:Tm (TLD-300) and CaF2:Mn (TLD-400) crystal chips (3.2 3.2 0.89 mm3) obtained from Harshaw Chemical Company, Ohio, USA. Before the experiment, the individual response of each crystal was determined. They were found to have nearly the same response. Any crystal having E-mail address: [email protected] 0921-4526/$ - see front matter & 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.physb.2010.11.032
discrepancies in the same batches were eliminated. The TLD-200 samples were annealed at 50071 1C for 1 h, TLD-300 samples were annealed at 40071 1C for 1 h and TLD-400 samples were annealed at 40071 1C for 30 min through the experiments to erase any residual information before subsequent irradiation and then cooled in air at approximately 75 1C/min to room temperature. All annealing treatments were carried out with a specially designed microprocessorcontrolled electrical oven, which is able to control the temperature within 71.0 1C. All irradiations were performed immediately after the standard annealing at room temperature with b rays from a 90Sr–90Y source (E0.04 Gy/s). Glow curves were obtained using a Harshaw QS 3500 Manuel type reader interfaced to a PC, where the TL signals were studied and analyzed. A standard clear glass filter was always installed in the reader. Glow curves were measured using a platinum planchet at different linear heating rates.
3. Experimental results In the past fifty years, thermoluminescent dosimeters (TLDs) have been investigated for routine applications in personnel and environmental dosimetry as well as in nuclear medicine. In general, the crystals that are usually used in routine personnel dosimetry and in nuclear medicine are LiF:Mg, Ti (TLD-100). However, calcium fluoride singly doped with dysprosium is another important TLD material, which is commercially available as TLD-200 from the Harshaw Chemical Company [9]. The sensitivity of this material is approximately 30 times higher than that of TLD-100 for g-rays. Therefore, it has found widespread use in the field of environmental and personnel radiation dosimetry despite some
538
V.E. Kafadar / Physica B 406 (2011) 537–540
transfer, LET). The ease with which P3 and P5 can be separated in the glow curve and their good stability make this TL detector particularly useful in certain applications, such as the estimation of radiation quality or dose measurements in mixed radiation fields in spite of its high Zeff ¼16.3. CaF2:Tm, first mentioned by Lukas and Kapsar (1977), has been receiving considerable attention ever since [10]. Fig. 2 shows some of the selected glow curves of CaF2:Tm (TLD-300) at linear heating rates between 1 and 30 1C/s. As seen from this figure the peak temperatures of all peaks shifted to higher temperatures when the heating rate increases as expected in the theory. It is also seen from this figure that the total peak area of the glow curves decreases as the heating rate increases. The total area of the glow curves were normalized to the low heating rate (1 1C/s) and it can be seen that the integrated area of the peaks decreases by about 50%. Thermoluminescence dosimeters (TLDs) based on CaF2 are highly attractive for radiation dosimetry in both natural (fluorite) and synthetic forms. Especially, Mn2 + -doped CaF2 has been used over the past four decades as an important thermoluminescent (TL) dosimeter due to its high sensitivity (compared to TLD-100) to doses as low as 50 mGy and a simple glow curve structure. Therefore, it has found widespread use in the field of environmental and personnel radiation dosimetry, despite some problems associated with batchto-batch irreproducibility, anomalous fading, and degradation during re-use, perennial zero dose problems and its poor energy response resulting from its high effective atomic number compared with tissue.
problems associated with batch-to-batch fluctuations, anomalous fading, complex glow curve structure and its poor energy response resulting from its high effective atomic number compared with tissue. Recently, Yazici et al. [9] found that the glow curve of this material has five peaks (P1E70, P2 E85, P3 E120, P4E150 and P5E180) between room temperature and 200 1C called low temperature peaks (LTPs) and four peaks (P6 E200, P7 E240, P8E310 and P9E390) between 200 and 500 1C called high temperature peaks (HTPs), at a linear heating rate of 1 1C/s. The behavior of the glow curves and the effect of thermal quenching due to the heating rate on the total peak area of glow curves were investigated at different linear heating rates between 1 and 30 1C/s. Fig. 1 shows some of the selected glow curves of CaF2:Dy (TLD-200) at linear heating rates between 1 and 30 1C/s. As seen from this figure the peak temperatures of all peaks shifted to higher temperatures with increase in heating rate, and the total peak area of the glow curves decreases as the heating rate increases as expected in the theory. The total area of the glow curves were normalized to low heating rate (1 1C/s) and it can be seen that the integrated area of the peaks decreases by about 30%. Thulium-doped calcium fluoride, CaF2:Tm (TLD-300), dosimeters may be obtained as single crystals, extruded rods and hot chips. The glow curve of these detectors consists of two well-separated peaks called P3 (E150) and P5 (E245), each exhibiting a different dependence on the ionisation density of the radiation (linear energy
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Heating Rate (°C/s) 90
Sr–90Y beta source at linear heating rates between 1 and 30 1C/s.
V.E. Kafadar / Physica B 406 (2011) 537–540
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4. Discussion and conclusion In this study, the effect of the heating rate on the glow curves and the integrated area of the peaks of CaF2:Dy (TLD-200), CaF2:Tm (TLD-300) and CaF2:Mn (TLD-400) crystals at linear heating rates between 1 and 10 1C/s has been investigated. Since doses are evaluated as fast as possible in personnel monitoring, reader systems having fast heating rates are employed to read out the
10
15
20
25
30
Heating Rate (°C/s)
Fig. 2. Glow curves and normalized TL peak area of TLD-300 crystals irradiated (12 Gy) with
The lack of tissue equivalence precludes its regular use as a personal dosimeter, but its high sensitivity make it an excellent environmental dosimetric material since exposure time in the field can be reduced accordingly [11,12]. The peak numbers in TLD-400 and their positions were determined by Drazic [13] with the experimental method based on annealing studies and it was confirmed that the main glow peak was composed of three peaks located at temperatures P1(2 5 5), P2(2 9 5) and P3(3 3 0) at a linear heating rate of 1 1C/s. Fig. 3 shows some of the selected glow curves of CaF2:Mn (TLD-400) at linear heating rates between 1 and 30 1C/s. As seen from this figure the peak temperatures of all peaks are shifted to high temperatures and the total peak area of the glow curves decreases as the heating rate increases. The total area of the glow curves was normalized to the low heating rate (1 1C/s) and a decrease in the integrated area of the peaks by about 60% can be seen.
5
90
Sr–90Y beta source at linear heating rates between 1 and 30 1C/s.
largest number of TLD cards in the shortest possible time with high intensity. Therefore, in TL dosimetric investigations, the routine personnel and environmental dosimetry uses heating rates higher than 10 1C/s to record the TL signals within a short time. The temperature of a TL peak shifts to higher values as the heating rate increases. Thus at low heating rates the TL peak may appear in a range where thermal quenching is minimal, whereas at high heating rates the peak temperature may be such that thermal quenching is strong [14]. Berkane-Krachai et al. [15] studied that heating rate effect on TL response and showed that the TL response decreases when heating rate increases and this reduction in TL sensitivity is well described using a Mott–Seitz theory. During the experiment, the measured temperature may be different from the sample temperature caused by a small temperature lag due to thermal contact of the heater and the sample. Therefore, there is a linear ramp in the sample with a temperature lag and so that Tm read from the glow curve will be systematically lower than its actual value. Consequently, the sample thickness has an important influence on the temperature gradient and temperature lag especially at high heating rates [16]. The heating rate effect on TL glow peaks has been largely discussed by Kitis et al. [17] who considers the heating rate as a dynamic parameter rather than a simple experimental setup variable. Other papers, not specifically dedicated to the effect of heating rate on the TL intensity, report experimentally results that are not always in agreement among
540
V.E. Kafadar / Physica B 406 (2011) 537–540
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Fig. 3. Glow curves and normalized TL peak area of TLD-400 crystals irradiated (12 Gy) with
them. His study has been carried out on single, well-separated glow peaks, considering the following experimental characteristics: i.e. Tm, full width at half maximum (FWHM), peak intensity and peak integral. The first thing to be considered is a possible delay between the temperature monitored by the thermocouple, fixed on the heating planchet, and the sample. Furthermore, the possibility of temperature gradients within the measured sample must be considered too. To avoid, totally or partially, these effects, special care has to be taken, i.e. the use of powder instead of solid samples diminishes greatly the gradient effects within the sample as well as between the heating planchet and the sample. It is well known that the dosimetric characteristics of many TL materials are influenced by changes in location, size and shape of the glow curves due to changes in heating rate. Thermal quenching was understood to be due to the increased probability of nonradiative transitions competing with the radiative transitions. Since the increase in heating rate resulted in an increase in the temperature of the TL glow peak, this shift in temperature was held responsible for the increase in the contribution of non-radiative transitions. Then, it was inferred that the glow peaks occurring at high temperatures must exhibit higher thermal quenching than those occurring at lower temperatures in any TLD material. Apart from the increased probability of non-radiative transitions at higher temperatures, the observed effects have also been assigned to the effects of heating rate on the migration of charge carriers released during the TL readout. The results of this study showed that the peak temperatures of all peaks shift to high temperatures
10
90
Sr–90Y beta source at linear heating rates between 1 and 30 1C/s.
and the integrated peak area of the curves decreases as the heating rate increases as expected in theory.
References [1] S.W.S. McKeever, Thermoluminescence of Solids, Cambridge University Press, USA, 1985, p. 374. [2] R. Chen, S.W.S. McKeever, Theory of Thermoluminescence and Related Phenomena, World Scientific Publishing Co. Pvt. Ltd., 1997. [3] F.O. Ogundare, F.A. Balogun, L.A. Hussain, Radiation Measurements 40 (2005) 60. [4] D.S. Betts, L. Couturier, A.H. Khayrat, B.J. Luff, P.D. Townsend, Journal of Physics D: Applied Physics 26 (1993) 843. [5] G.C. Taylor, E. Lilley, Journal of Physics D: Applied Physics 15 (1982) 2053. [6] T. Nakajima, Japanese Journal of Applied Physics 15 (6) (1976) 1179. [7] V.K. Jain, Journal of Applied Physics 17 (1978) 949. [8] N.A. Spooner, A.D. Franklin, Radiation Measurements 35 (2002) 59. ¨ [9] A.N. Yazici, Z. Ozturk, Nuclear Instruments and Methods B 174 (2001) 499. [10] B. Marczewska, P. Bilski, M. Budzanowski, P. Olko, V. Chernov, Radiation Measurements 33 (2001) 571. [11] A. Zarate-Morales, A.E. Buenfil, Health Physics 71 (3) (1996) 358. ¨ [12] R Kalchgruber, H.Y Goksu, E Hochhauser, G.A Wagner, Radiation Measurements 35 (2002) 585. [13] G. Drazic, U. Miklavzic, M. Mihelic, Radiation Protection Dosimetry 17 (1986) 343. [14] R. Nanjundaswamy, K. Lepper, S.W.S. McKeever, Radiation Protection Dosimetry 100 (2002) 305. [15] A. Berkane-Krachi, P. Iacconi, R. Bindi, S. Vinceller, Journal of Physics D: Applied Physics 35 (2002) 1895. [16] N.G. Kıyak, E. Bulus-, Radiation Measurements 33 (2002) 879. [17] G. Kitis, M. Spiropulu, J. Papadopoulos, S. Charalambous, Nuclear Instruments and Methods B 73 (1993) 367.
Contents lists available at ScienceDirect
Physica B journal homepage: www.elsevier.com/locate/physb
Thermal quenching of thermoluminescence in TLD-200, TLD-300 and TLD-400 after b-irradiation Vural E. Kafadar Department of Engineering Physics, University of Gaziantep, 27310 Gaziantep, Turkey
a r t i c l e in f o
abstract
Article history: Received 19 August 2010 Received in revised form 9 November 2010 Accepted 10 November 2010
The dosimetric characteristics of many TL materials are influenced by changes in location, size and shape of the glow curves due to changes in the heating rate. In this study, the effect of heating rate on the integrated peak areas of CaF2:Dy (TLD-200), CaF2:Tm (TLD-300) and CaF2:Mn (TLD-400) crystals have been investigated after b-irradiation. It was observed that the peak temperatures of all peaks shifted to the high temperature sides and the integrated peak areas decrease as the heating rate increases due to thermal quenching, whose efficiency increases as temperature increases. & 2010 Elsevier B.V. All rights reserved.
Keywords: Thermal quenching TLD-200 TLD-300 TLD-400
1. Introduction Thermoluminescence in solids is the emission of light from an insulator or semiconductor, which takes place during the heating of a solid, following an earlier absorption of energy from radiation [1,2]. In thermoluminescence (TL), the glow curve is affected by some experimental parameters. Heating rate is one of the most important experimental variables, which changes the glow curve shape [3]. In TL dosimetry, the absorbed dose and TL intensity are affected by changes in the heating rate [4,5]. Many investigations have been carried out by scientists in order to understand that how the TL glow curve changes under different heating rates [5–8]. Taylor and Lilley [5] pointed out that changes in intensity, caused by the change in heating rate, may have a bearing on the determination of trapping parameters E (trap depth) and s (frequency factor). As a result of many studies, a decrease in TL intensity was observed with increase in the heating rate. This phenomenon has been explained to be due to thermal quenching, whose efficiency increases as temperature increases [8].
2. Experimental procedure The samples used in this study were CaF2:Dy (TLD-200), CaF2:Tm (TLD-300) and CaF2:Mn (TLD-400) crystal chips (3.2 3.2 0.89 mm3) obtained from Harshaw Chemical Company, Ohio, USA. Before the experiment, the individual response of each crystal was determined. They were found to have nearly the same response. Any crystal having E-mail address: [email protected] 0921-4526/$ - see front matter & 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.physb.2010.11.032
discrepancies in the same batches were eliminated. The TLD-200 samples were annealed at 50071 1C for 1 h, TLD-300 samples were annealed at 40071 1C for 1 h and TLD-400 samples were annealed at 40071 1C for 30 min through the experiments to erase any residual information before subsequent irradiation and then cooled in air at approximately 75 1C/min to room temperature. All annealing treatments were carried out with a specially designed microprocessorcontrolled electrical oven, which is able to control the temperature within 71.0 1C. All irradiations were performed immediately after the standard annealing at room temperature with b rays from a 90Sr–90Y source (E0.04 Gy/s). Glow curves were obtained using a Harshaw QS 3500 Manuel type reader interfaced to a PC, where the TL signals were studied and analyzed. A standard clear glass filter was always installed in the reader. Glow curves were measured using a platinum planchet at different linear heating rates.
3. Experimental results In the past fifty years, thermoluminescent dosimeters (TLDs) have been investigated for routine applications in personnel and environmental dosimetry as well as in nuclear medicine. In general, the crystals that are usually used in routine personnel dosimetry and in nuclear medicine are LiF:Mg, Ti (TLD-100). However, calcium fluoride singly doped with dysprosium is another important TLD material, which is commercially available as TLD-200 from the Harshaw Chemical Company [9]. The sensitivity of this material is approximately 30 times higher than that of TLD-100 for g-rays. Therefore, it has found widespread use in the field of environmental and personnel radiation dosimetry despite some
538
V.E. Kafadar / Physica B 406 (2011) 537–540
transfer, LET). The ease with which P3 and P5 can be separated in the glow curve and their good stability make this TL detector particularly useful in certain applications, such as the estimation of radiation quality or dose measurements in mixed radiation fields in spite of its high Zeff ¼16.3. CaF2:Tm, first mentioned by Lukas and Kapsar (1977), has been receiving considerable attention ever since [10]. Fig. 2 shows some of the selected glow curves of CaF2:Tm (TLD-300) at linear heating rates between 1 and 30 1C/s. As seen from this figure the peak temperatures of all peaks shifted to higher temperatures when the heating rate increases as expected in the theory. It is also seen from this figure that the total peak area of the glow curves decreases as the heating rate increases. The total area of the glow curves were normalized to the low heating rate (1 1C/s) and it can be seen that the integrated area of the peaks decreases by about 50%. Thermoluminescence dosimeters (TLDs) based on CaF2 are highly attractive for radiation dosimetry in both natural (fluorite) and synthetic forms. Especially, Mn2 + -doped CaF2 has been used over the past four decades as an important thermoluminescent (TL) dosimeter due to its high sensitivity (compared to TLD-100) to doses as low as 50 mGy and a simple glow curve structure. Therefore, it has found widespread use in the field of environmental and personnel radiation dosimetry, despite some problems associated with batchto-batch irreproducibility, anomalous fading, and degradation during re-use, perennial zero dose problems and its poor energy response resulting from its high effective atomic number compared with tissue.
problems associated with batch-to-batch fluctuations, anomalous fading, complex glow curve structure and its poor energy response resulting from its high effective atomic number compared with tissue. Recently, Yazici et al. [9] found that the glow curve of this material has five peaks (P1E70, P2 E85, P3 E120, P4E150 and P5E180) between room temperature and 200 1C called low temperature peaks (LTPs) and four peaks (P6 E200, P7 E240, P8E310 and P9E390) between 200 and 500 1C called high temperature peaks (HTPs), at a linear heating rate of 1 1C/s. The behavior of the glow curves and the effect of thermal quenching due to the heating rate on the total peak area of glow curves were investigated at different linear heating rates between 1 and 30 1C/s. Fig. 1 shows some of the selected glow curves of CaF2:Dy (TLD-200) at linear heating rates between 1 and 30 1C/s. As seen from this figure the peak temperatures of all peaks shifted to higher temperatures with increase in heating rate, and the total peak area of the glow curves decreases as the heating rate increases as expected in the theory. The total area of the glow curves were normalized to low heating rate (1 1C/s) and it can be seen that the integrated area of the peaks decreases by about 30%. Thulium-doped calcium fluoride, CaF2:Tm (TLD-300), dosimeters may be obtained as single crystals, extruded rods and hot chips. The glow curve of these detectors consists of two well-separated peaks called P3 (E150) and P5 (E245), each exhibiting a different dependence on the ionisation density of the radiation (linear energy
4x107
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Temperature (°C) Fig. 1. Glow curves and normalized TL peak area of TLD-200 crystals irradiated (12 Gy) with
5
10
15
20
25
30
Heating Rate (°C/s) 90
Sr–90Y beta source at linear heating rates between 1 and 30 1C/s.
V.E. Kafadar / Physica B 406 (2011) 537–540
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4. Discussion and conclusion In this study, the effect of the heating rate on the glow curves and the integrated area of the peaks of CaF2:Dy (TLD-200), CaF2:Tm (TLD-300) and CaF2:Mn (TLD-400) crystals at linear heating rates between 1 and 10 1C/s has been investigated. Since doses are evaluated as fast as possible in personnel monitoring, reader systems having fast heating rates are employed to read out the
10
15
20
25
30
Heating Rate (°C/s)
Fig. 2. Glow curves and normalized TL peak area of TLD-300 crystals irradiated (12 Gy) with
The lack of tissue equivalence precludes its regular use as a personal dosimeter, but its high sensitivity make it an excellent environmental dosimetric material since exposure time in the field can be reduced accordingly [11,12]. The peak numbers in TLD-400 and their positions were determined by Drazic [13] with the experimental method based on annealing studies and it was confirmed that the main glow peak was composed of three peaks located at temperatures P1(2 5 5), P2(2 9 5) and P3(3 3 0) at a linear heating rate of 1 1C/s. Fig. 3 shows some of the selected glow curves of CaF2:Mn (TLD-400) at linear heating rates between 1 and 30 1C/s. As seen from this figure the peak temperatures of all peaks are shifted to high temperatures and the total peak area of the glow curves decreases as the heating rate increases. The total area of the glow curves was normalized to the low heating rate (1 1C/s) and a decrease in the integrated area of the peaks by about 60% can be seen.
5
90
Sr–90Y beta source at linear heating rates between 1 and 30 1C/s.
largest number of TLD cards in the shortest possible time with high intensity. Therefore, in TL dosimetric investigations, the routine personnel and environmental dosimetry uses heating rates higher than 10 1C/s to record the TL signals within a short time. The temperature of a TL peak shifts to higher values as the heating rate increases. Thus at low heating rates the TL peak may appear in a range where thermal quenching is minimal, whereas at high heating rates the peak temperature may be such that thermal quenching is strong [14]. Berkane-Krachai et al. [15] studied that heating rate effect on TL response and showed that the TL response decreases when heating rate increases and this reduction in TL sensitivity is well described using a Mott–Seitz theory. During the experiment, the measured temperature may be different from the sample temperature caused by a small temperature lag due to thermal contact of the heater and the sample. Therefore, there is a linear ramp in the sample with a temperature lag and so that Tm read from the glow curve will be systematically lower than its actual value. Consequently, the sample thickness has an important influence on the temperature gradient and temperature lag especially at high heating rates [16]. The heating rate effect on TL glow peaks has been largely discussed by Kitis et al. [17] who considers the heating rate as a dynamic parameter rather than a simple experimental setup variable. Other papers, not specifically dedicated to the effect of heating rate on the TL intensity, report experimentally results that are not always in agreement among
540
V.E. Kafadar / Physica B 406 (2011) 537–540
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20 °C/s 30 °C/s
6
2.0x10
6
1.5x10
1.0x106 5.0x105 0.0
TLD-400
0.9 0.8 0.7 0.6 0.5 0.4
50
100
150
200
250
300
350
5
400
Temperature (°C)
15
20
25
30
Heating Rate (°C/s)
Fig. 3. Glow curves and normalized TL peak area of TLD-400 crystals irradiated (12 Gy) with
them. His study has been carried out on single, well-separated glow peaks, considering the following experimental characteristics: i.e. Tm, full width at half maximum (FWHM), peak intensity and peak integral. The first thing to be considered is a possible delay between the temperature monitored by the thermocouple, fixed on the heating planchet, and the sample. Furthermore, the possibility of temperature gradients within the measured sample must be considered too. To avoid, totally or partially, these effects, special care has to be taken, i.e. the use of powder instead of solid samples diminishes greatly the gradient effects within the sample as well as between the heating planchet and the sample. It is well known that the dosimetric characteristics of many TL materials are influenced by changes in location, size and shape of the glow curves due to changes in heating rate. Thermal quenching was understood to be due to the increased probability of nonradiative transitions competing with the radiative transitions. Since the increase in heating rate resulted in an increase in the temperature of the TL glow peak, this shift in temperature was held responsible for the increase in the contribution of non-radiative transitions. Then, it was inferred that the glow peaks occurring at high temperatures must exhibit higher thermal quenching than those occurring at lower temperatures in any TLD material. Apart from the increased probability of non-radiative transitions at higher temperatures, the observed effects have also been assigned to the effects of heating rate on the migration of charge carriers released during the TL readout. The results of this study showed that the peak temperatures of all peaks shift to high temperatures
10
90
Sr–90Y beta source at linear heating rates between 1 and 30 1C/s.
and the integrated peak area of the curves decreases as the heating rate increases as expected in theory.
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