Thermoluminescence properties of potassium fluoride:
- Authors: Ogundare, F O , Folley, Damilola E , Chithambo, Makaiko L , Arise, T O
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/160500 , vital:40451 , https://doi.org/10.1016/j.nimb.2020.09.009
- Description: This study is designed to examine the thermoluminescence characteristics of potassium fluoride for possible use as a thermoluminescence dosemeter. Thermoluminescence measurements were carried out at doses up to 20 Gy and heating rates between 0.2 and 4°C/s. The glow curve of the fluoride, readout at 1°Cs−1, exhibited two peaks at 130 and 250 °C. In addition, two shoulder peaks appeared at 70 and 200°C.
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Optically stimulated luminescence of ultra-high molecular weight polyethylene: a study of dosimetric features
- Authors: Chithambo, Makaiko L , Kalita, Jitumani M
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/110035 , vital:33217 , https://doi.org/10.1016/j.radmeas.2018.06.006
- Description: We report the dosimetric features of ultra-high molecular weight polyethylene (UHMWPE) using luminescence optically stimulated using 470 nm blue light. Samples irradiated to between 1 and 1000 Gy produces luminescence that increases with irradiation dose to produce a linear dose response between 1 and 1000 Gy. The sample was determined not to be affected by pre-dose in tests using a pre-dose of 4000 Gy. This characteristic precludes the need for elaborate background erasing routines typical of dosimetry experiments. The signal has good reproducibility. We used this property to test recovery of ‘unknown’ doses with encouraging results. It was observed that luminescence can also be stimulated using 870 nm infrared light. The dose response, fading, pre-dose effect and the ability to optically stimulate luminescence from the polymer is discussed in terms of curing involving free-radicals.
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Thermoluminescence of the persistent-luminescence phosphor, BaAl2O4: a stuffed tridymite
- Authors: Pandey, A , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/113048 , vital:33693 , hhttps://doi.org/10.1016/j.radmeas.2018.01.004
- Description: BaAl2O4 is a stuffed tridymite used as a long-lasting phosphor. The thermoluminescence of BaAl2O4 prepared by solution-combustion is reported. Analysis of the sample using X-ray diffraction shows that it formed as a single phase compound with a hexagonal structure following annealing at 1200 °C. A broad photoluminescence emission band between 300 and 650 nm was detected due to excitation at 248 nm. The phosphor showed a natural TL peak at 102 °C for measurement at 1 oCs−1 and, when beta irradiated to 100 Gy, two broad peaks at 123 and 318 °C also for heating at 1 oCs−1. The analysis of the main glow peak at 123 °C suggests that it is a combination of several collocated peaks, that is, peaks embedded within each other. We resolved four such components labelled peaks 1 to 4. The thermoluminescence decreases with heating rate in a way consistent with thermal quenching whose activation energy was determined as ∼0.65eV using peak 3. Interestingly, this value of the activation energy for thermal quenching for BaAl2O4, a stuffed derivative of silica, is similar to literature values for quartz (a silica), suggesting that the recombination centre in the two cases may be similar.
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Radioluminescence of annealed synthetic quartz
- Authors: Chithambo, Makaiko L , Niyonzima, P
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/115504 , vital:34150 , https://doi.org/10.1016/j.radmeas.2017.02.005
- Description: The radioluminescence of synthetic quartz annealed at various temperatures up to 1000 °C is reported. The amplitude of the emission bands increases with annealing temperature. In addition, when samples are annealed at temperatures exceeding 700 °C, the intensity of the radioluminescence increases with duration of annealing. The corresponding emission spectra show seven emission bands at 2.04, 2.54, 2.77, 3.04, 3.40, 3.75 and 3.91 eV. The change in dominant emission band with annealing is consistent with annealing-induced variations in lifetimes determined previously from time-resolved optically stimulated luminescence spectra in the same samples.
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Temperature dependence of optically stimulated luminescence of α-Al2O3: C, Mg
- Authors: Kalita, Jitumani M , Chithambo, Makaiko L
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/115708 , vital:34217 , https://doi.org/10.1016/j.radmeas.2017.08.009
- Description: Thermal assistance and thermal quenching are two independently acting thermodynamic phenomena that simultaneously affect the stimulation of luminescence. We have studied thermal assistance to luminescence optically stimulated from α-Al2O3:C,Mg. Since thermal assistance causes only a minor change in the luminescence intensity, measurements were made after the sample had been pre-exposed to stimulating light to reduce its intensity significantly, that is, in the slow component of its decay curve. The luminescence intensity was monitored as a function of measurement temperature between 30 and 130 °C. The intensity goes through a peak at 60 °C due to competing effects of thermal assistance and thermal quenching. The initial increase of intensity is attributed to dominant thermal assistance whereas the subsequent decrease of intensity is ascribed to dominant thermal quenching. The activation energy for thermal assistance was calculated for the main electron trap of an un-annealed sample as 0.324 ± 0.020 eV and in a sample annealed at 900 °C as 0.416 ± 0.028 eV. Implications of such differences in the value of the activation energy for thermal assistance are considered.
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Thermally-assisted optically stimulated luminescence from deep electron traps in α-Al2O3: C, Mg
- Authors: Kalita, Jitumani M , Chithambo, Makaiko L , Polymeris, G S
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/116133 , vital:34322 , https://doi.org/10.1016/j.nimb.2017.04.075
- Description: We report thermally-assisted optically stimulated luminescence (TA-OSL) in α-Al2O3:C,Mg. The OSL was measured at elevated temperatures between 50 and 240 °C from a sample preheated to 500 °C after irradiation to 100 Gy. That OSL could be measured even after the preheating is direct evidence of the existence of deep electron traps in α-Al2O3:C,Mg. The TA-OSL intensity goes through a peak with measurement temperature. The initial increase is ascribed to thermal assistance to optical stimulation whereas the subsequent decrease in intensity is deduced to reflect increasing incidences of non-radiative recombination, that is, thermal quenching. The activation energy for thermal assistance corresponding to a deep electron trap was estimated as 0.667 ± 0.006 eV whereas the activation energy for thermal quenching was calculated as 0.90 ± 0.04 eV. The intensity of the TA-OSL was also found to increase with irradiation dose. The dose response is sublinear from 25 to 150 Gy but saturates with further increase of dose. The TA-OSL dose response has been discussed by considering the competition for charges at the deep traps. This study incidentally shows that TA-OSL can be effectively used in dosimetry involving large doses.
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Thermoluminescence of α-Al2O3: C, Mg: kinetic analysis of the main glow peak
- Authors: Kalita, Jitumani M , Chithambo, Makaiko L
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/119844 , vital:34788 , https://doi.org/10.1016/j.jlumin.2016.10.031
- Description: The kinetic analysis of the thermoluminescence of aluminium oxide doped with carbon and co-doped with magnesium (α-Al2O3:C,Mg) is reported. Measurements were made at 1 °C/s following beta irradiation to 1 Gy. The glow curve consists of a dominant peak at a peak-maximum Tm of 161 °C and six secondary peaks of weaker intensity at 42, 72, 193, 279, 330 and 370 °C. Kinetic analysis of the main peak, the subject of this report, was carried out using initial rise, whole glow peak, peak shape, curve fitting and variable heating rate methods. The order of kinetics of the main 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 ~1.36 eV and the frequency factor of the order of 1014 s−1. The peak area changes with heating rate in a manner that shows that the peak is affected by thermal quenching. The activation energy of thermal quenching was evaluated as 0.99±0.08 eV. A comparison of analytical results from the main peak before and after correction for thermal quenching show that the kinetic parameters of the main peak are not that affected by thermal quenching.
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