The effect of pre-dose on thermally and optically stimulated luminescence from α-Al2O3C, Mg and α-Al2O3: C
- Kalita, Jitumani M, Chithambo, Makaiko L
- Authors: Kalita, Jitumani M , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/111011 , vital:33363 , https://doi.org/10.1016/j.apradiso.2018.06.012
- Description: We report the effect of pre-dose on the thermoluminescence (TL) and optically stimulated luminescence (OSL) dose response of α-Al2O3:C,Mg and α-Al2O3:C. Before any luminescence measurement, the samples were irradiated with different doses, namely 100, 500 and 1000 Gy to populate the deep electron traps. This is the pre-dose. The results from TL and OSL studies are compared with results from samples used without any pre-measurement dose. The TL glow curves and OSL decay curves of α-Al2O3:C,Mg recorded after pre-doses of 100, 500 and 1000 Gy are identical to those from a sample used without any pre-dose. Further, the TL and OSL dose response of all α-Al2O3:C,Mg samples are similar regardless of pre-dose. In comparison, the TL glow curves and OSL decay curves of α-Al2O3:C are influenced by pre-dose. We conclude that the differences in the TL and OSL dose response of various pre-dosed samples of α-Al2O3:C are due to the concentration of charge in the deep traps. On the other hand, owing to the lower concentration of such deep traps in α-Al2O3:C,Mg, the TL or OSL dose responses are not affected by pre-dose in this material.
- Full Text: false
- Date Issued: 2018
- Authors: Kalita, Jitumani M , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/111011 , vital:33363 , https://doi.org/10.1016/j.apradiso.2018.06.012
- Description: We report the effect of pre-dose on the thermoluminescence (TL) and optically stimulated luminescence (OSL) dose response of α-Al2O3:C,Mg and α-Al2O3:C. Before any luminescence measurement, the samples were irradiated with different doses, namely 100, 500 and 1000 Gy to populate the deep electron traps. This is the pre-dose. The results from TL and OSL studies are compared with results from samples used without any pre-measurement dose. The TL glow curves and OSL decay curves of α-Al2O3:C,Mg recorded after pre-doses of 100, 500 and 1000 Gy are identical to those from a sample used without any pre-dose. Further, the TL and OSL dose response of all α-Al2O3:C,Mg samples are similar regardless of pre-dose. In comparison, the TL glow curves and OSL decay curves of α-Al2O3:C are influenced by pre-dose. We conclude that the differences in the TL and OSL dose response of various pre-dosed samples of α-Al2O3:C are due to the concentration of charge in the deep traps. On the other hand, owing to the lower concentration of such deep traps in α-Al2O3:C,Mg, the TL or OSL dose responses are not affected by pre-dose in this material.
- Full Text: false
- Date Issued: 2018
Thermoluminescence of α-Al2O3: C, Mg annealed at 1200° C
- Kalita, Jitumani M, Chithambo, Makaiko L
- Authors: Kalita, Jitumani M , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/111030 , vital:33365 , https://doi.org/10.1016/j.nimb.2018.03.003
- Description: Stimulated luminescence in α-Al2O3:C,Mg has thus far been studied for samples annealed at temperature no higher than 900 °C as can be seen by an examination of the literature. We report the thermoluminescence (TL) features of α-Al2O3:C,Mg annealed at 1200 °C. A glow curve measured at 1 °C/s from the samples annealed at 1200 °C shows eight peaks at 54, 80, 102, 173, 238, 290, 330 and 387 °C. Kinetic analyses show that the peak at 54 °C follows general order kinetics (b = 1.3) whereas the rest follow first order kinetics. The values of the activation energy of the peaks are between 0.77 eV and 1.90 eV and the frequency factors are of the order of 1010–1014 s−1. The intensity of the peaks at 54, 80, 102 and 173 °C increase with heating rate whereas those of the peaks at 238 and 290 °C decrease with heating rate. The decrease of intensity of the peaks at 238 and 290 °C with heating rate is due to thermal quenching whereas the increase of intensity of the peaks with heating rate indicates an inverse thermal-quenching-like behaviour. Interestingly this behaviour is observed only after annealing at 1200 °C. The activation energy for thermal quenching as calculated using the peaks at 238 and 290 °C are (1.02 ± 0.16) eV and (1.33 ± 0.15) eV respectively. Regarding the dosimetric features, the dose response of the peaks at 54, 80 and 102 °C are sublinear within 1–10 Gy and the peak at 54 °C saturates above 6 Gy. In contrast, the response of the peak at 173 °C is sublinear with 1–4 Gy and superlinear between 4 and 10 Gy. The peaks are found to fade at different rates and the rate of fading is also affected by annealing.
- Full Text: false
- Date Issued: 2018
- Authors: Kalita, Jitumani M , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/111030 , vital:33365 , https://doi.org/10.1016/j.nimb.2018.03.003
- Description: Stimulated luminescence in α-Al2O3:C,Mg has thus far been studied for samples annealed at temperature no higher than 900 °C as can be seen by an examination of the literature. We report the thermoluminescence (TL) features of α-Al2O3:C,Mg annealed at 1200 °C. A glow curve measured at 1 °C/s from the samples annealed at 1200 °C shows eight peaks at 54, 80, 102, 173, 238, 290, 330 and 387 °C. Kinetic analyses show that the peak at 54 °C follows general order kinetics (b = 1.3) whereas the rest follow first order kinetics. The values of the activation energy of the peaks are between 0.77 eV and 1.90 eV and the frequency factors are of the order of 1010–1014 s−1. The intensity of the peaks at 54, 80, 102 and 173 °C increase with heating rate whereas those of the peaks at 238 and 290 °C decrease with heating rate. The decrease of intensity of the peaks at 238 and 290 °C with heating rate is due to thermal quenching whereas the increase of intensity of the peaks with heating rate indicates an inverse thermal-quenching-like behaviour. Interestingly this behaviour is observed only after annealing at 1200 °C. The activation energy for thermal quenching as calculated using the peaks at 238 and 290 °C are (1.02 ± 0.16) eV and (1.33 ± 0.15) eV respectively. Regarding the dosimetric features, the dose response of the peaks at 54, 80 and 102 °C are sublinear within 1–10 Gy and the peak at 54 °C saturates above 6 Gy. In contrast, the response of the peak at 173 °C is sublinear with 1–4 Gy and superlinear between 4 and 10 Gy. The peaks are found to fade at different rates and the rate of fading is also affected by annealing.
- Full Text: false
- Date Issued: 2018
Features of an annealing-induced thermoluminescence peak in α-Al2O3: C, Mg
- Kalita, Jitumani M, Chithambo, Makaiko L
- Authors: Kalita, Jitumani M , Chithambo, Makaiko L
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/116013 , vital:34289 , DOI: 10.1016/j.optmat.2017.05.034
- Description: We report the thermoluminescence glow curves of beta irradiated single crystal α-Al2O3:C,Mg after annealing at 700 and 900 °C. A glow curve measured at 1 °C/s from samples irradiated to 1 Gy following annealing at 700 and 900 °C shows a high intensity peak at 163 °C and seven secondary peaks of weaker intensity at 43, 73, 100, 195, 280, 329 and 370 °C. Comparing the position of the peaks in the annealed samples with those in an un-annealed one, it is observed that the peak at 100 °C appears only after annealing at and above 700 °C. Kinetic analysis of this annealing-induced peak was carried out using the initial rise, whole glow peak, peak shape, curve fitting and variable heating rate methods. The order of kinetics of the peak was determined as first order using various methods including the Tm-Tstop technique and the dependence of Tm on irradiation dose. The activation energy of the peak is about 1.01 eV and the frequency factor of the order of 1012 s−1. The peak was found to be affected by thermal quenching in analysis based on change of peak intensity with heating rate. The activation energy of thermal quenching was evaluated as 1.06 ± 0.08 eV. We speculate that the annealing-induced peak is due to formation of a new electron trap after destruction of the F22+(2 Mg) centre when the sample is annealed at 700 °C. The annealing-induced peak fades with storage between irradiation and measurement. It was also concluded that electrons from traps corresponding to secondary peaks get re-trapped at the main electron trap.
- Full Text: false
- Date Issued: 2017
- Authors: Kalita, Jitumani M , Chithambo, Makaiko L
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/116013 , vital:34289 , DOI: 10.1016/j.optmat.2017.05.034
- Description: We report the thermoluminescence glow curves of beta irradiated single crystal α-Al2O3:C,Mg after annealing at 700 and 900 °C. A glow curve measured at 1 °C/s from samples irradiated to 1 Gy following annealing at 700 and 900 °C shows a high intensity peak at 163 °C and seven secondary peaks of weaker intensity at 43, 73, 100, 195, 280, 329 and 370 °C. Comparing the position of the peaks in the annealed samples with those in an un-annealed one, it is observed that the peak at 100 °C appears only after annealing at and above 700 °C. Kinetic analysis of this annealing-induced peak was carried out using the initial rise, whole glow peak, peak shape, curve fitting and variable heating rate methods. The order of kinetics of the peak was determined as first order using various methods including the Tm-Tstop technique and the dependence of Tm on irradiation dose. The activation energy of the peak is about 1.01 eV and the frequency factor of the order of 1012 s−1. The peak was found to be affected by thermal quenching in analysis based on change of peak intensity with heating rate. The activation energy of thermal quenching was evaluated as 1.06 ± 0.08 eV. We speculate that the annealing-induced peak is due to formation of a new electron trap after destruction of the F22+(2 Mg) centre when the sample is annealed at 700 °C. The annealing-induced peak fades with storage between irradiation and measurement. It was also concluded that electrons from traps corresponding to secondary peaks get re-trapped at the main electron trap.
- Full Text: false
- Date Issued: 2017
On the sensitivity of thermally and optically stimulated luminescence of α-Al2O3: C and α-Al2O3: C, Mg
- Kalita, Jitumani M, Chithambo, Makaiko L
- Authors: Kalita, Jitumani M , Chithambo, Makaiko L
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/119803 , vital:34784 , https://doi.org/10.1016/j.radmeas.2017.03.006
- Description: The luminescence sensitivity of α-Al2O3:C and α-Al2O3:C, Mg is of interest because of the contemporary use of these materials in dosimetry related applications. We report investigations concerning the change in sensitivity of thermoluminescence (TL) and optically stimulated luminescence (OSL) from α-Al2O3:C and α-Al2O3:C, Mg with re-use. The study was carried out on a set of un-annealed samples and others annealed at 700 and 900 °C. The TL and OSL sensitivity in α-Al2O3:C and α-Al2O3:C, Mg was found to increase with sample re-use whether the intensity was monitored as peak area or peak height for the main TL peak or, in the case of OSL, as the maximum intensity or the area under a decay curve. The fractional increase in area under either the main TL peak or the OSL decay curve exceeds that of the TL peak height or maximum OSL intensity when samples are re-used. However, when un-annealed samples are used, any increase in TL peak height or peak area per measurement is less than observed in annealed samples. It is also interesting to note that the change in maximum OSL intensity or OSL area is minimal for samples annealed at 900 °C. In general, the TL sensitivity in α-Al2O3:C increases more than that in α-Al2O3:C, Mg with re-use. On the other hand, the OSL sensitivity in α-Al2O3:C, Mg increases more than that in α-Al2O3:C with re-use. These findings suggest that it is advisable to take into account the fractional increase in sensitivity per measurement when one uses α-Al2O3:C as a TL dosimeter and α-Al2O3:C, Mg as an OSL dosimeter.
- Full Text: false
- Date Issued: 2017
- Authors: Kalita, Jitumani M , Chithambo, Makaiko L
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/119803 , vital:34784 , https://doi.org/10.1016/j.radmeas.2017.03.006
- Description: The luminescence sensitivity of α-Al2O3:C and α-Al2O3:C, Mg is of interest because of the contemporary use of these materials in dosimetry related applications. We report investigations concerning the change in sensitivity of thermoluminescence (TL) and optically stimulated luminescence (OSL) from α-Al2O3:C and α-Al2O3:C, Mg with re-use. The study was carried out on a set of un-annealed samples and others annealed at 700 and 900 °C. The TL and OSL sensitivity in α-Al2O3:C and α-Al2O3:C, Mg was found to increase with sample re-use whether the intensity was monitored as peak area or peak height for the main TL peak or, in the case of OSL, as the maximum intensity or the area under a decay curve. The fractional increase in area under either the main TL peak or the OSL decay curve exceeds that of the TL peak height or maximum OSL intensity when samples are re-used. However, when un-annealed samples are used, any increase in TL peak height or peak area per measurement is less than observed in annealed samples. It is also interesting to note that the change in maximum OSL intensity or OSL area is minimal for samples annealed at 900 °C. In general, the TL sensitivity in α-Al2O3:C increases more than that in α-Al2O3:C, Mg with re-use. On the other hand, the OSL sensitivity in α-Al2O3:C, Mg increases more than that in α-Al2O3:C with re-use. These findings suggest that it is advisable to take into account the fractional increase in sensitivity per measurement when one uses α-Al2O3:C as a TL dosimeter and α-Al2O3:C, Mg as an OSL dosimeter.
- Full Text: false
- Date Issued: 2017
Phototransferred thermoluminescence in α-Al2O3: C, Mg under 470 nm blue light stimulation
- Kalita, Jitumani M, Chithambo, Makaiko L
- Authors: Kalita, Jitumani M , Chithambo, Makaiko L
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/116026 , vital:34290 , https://doi.org/10.1016/j.jlumin.2017.04.059
- Description: Phototransferred thermoluminescence (PTTL) in α-Al2O3:C,Mg under 470 nm blue light has been investigated. Conventional thermoluminescence (TL) measured at 1 °C/s following irradiation to 10 Gy shows the main peak (labelled as III) at 163 °C and six secondary peaks I, II, IV, V, VI and VII at 45, 74, 200, 279, 328, 370 °C respectively. When a sample irradiated to 10 Gy is preheated to 220 °C at 1 °C/s to remove peaks I, II, III and IV and then exposed to 470 nm blue light for 100 s, it is found that three peaks I, II and III are reproduced under phototransfer. Kinetic analysis of the PTTL peaks shows that their kinetic parameters are similar to those of peaks I, II and III from conventional TL. Pulse annealing experiments, intended to study the dependence of PTTL peak intensity on preheating temperature, show that the electron traps corresponding to peaks V, VI and VII act as donor traps whereas the traps corresponding to peaks I, II and III act as acceptor traps. Further, it was found that no PTTL can be generated when all the traps corresponding to peaks I, II…VII are erased by preheating after irradiation. The primary conclusion here is that α-Al2O3:C,Mg does not have any deep traps beyond 400 °C sensitive to 470 nm stimulation or if there are any, their concentration is negligible. The PTTL for any of the PTTL peaks mentioned earlier increases with illumination time to a maximum within 400 s for measurements corresponding to doses between 6 and 15 Gy. The dose response of PTTL peaks II and III is linear within 1–15 Gy. Regarding fading, PTTL peak II fades to background level within 18000 s whereas in the same time, PTTL peak III fades down to 40% of its initial intensity.
- Full Text: false
- Date Issued: 2017
- Authors: Kalita, Jitumani M , Chithambo, Makaiko L
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/116026 , vital:34290 , https://doi.org/10.1016/j.jlumin.2017.04.059
- Description: Phototransferred thermoluminescence (PTTL) in α-Al2O3:C,Mg under 470 nm blue light has been investigated. Conventional thermoluminescence (TL) measured at 1 °C/s following irradiation to 10 Gy shows the main peak (labelled as III) at 163 °C and six secondary peaks I, II, IV, V, VI and VII at 45, 74, 200, 279, 328, 370 °C respectively. When a sample irradiated to 10 Gy is preheated to 220 °C at 1 °C/s to remove peaks I, II, III and IV and then exposed to 470 nm blue light for 100 s, it is found that three peaks I, II and III are reproduced under phototransfer. Kinetic analysis of the PTTL peaks shows that their kinetic parameters are similar to those of peaks I, II and III from conventional TL. Pulse annealing experiments, intended to study the dependence of PTTL peak intensity on preheating temperature, show that the electron traps corresponding to peaks V, VI and VII act as donor traps whereas the traps corresponding to peaks I, II and III act as acceptor traps. Further, it was found that no PTTL can be generated when all the traps corresponding to peaks I, II…VII are erased by preheating after irradiation. The primary conclusion here is that α-Al2O3:C,Mg does not have any deep traps beyond 400 °C sensitive to 470 nm stimulation or if there are any, their concentration is negligible. The PTTL for any of the PTTL peaks mentioned earlier increases with illumination time to a maximum within 400 s for measurements corresponding to doses between 6 and 15 Gy. The dose response of PTTL peaks II and III is linear within 1–15 Gy. Regarding fading, PTTL peak II fades to background level within 18000 s whereas in the same time, PTTL peak III fades down to 40% of its initial intensity.
- Full Text: false
- Date Issued: 2017
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