OSL dosimetric properties and efficiency of Brazilian natural calcium fluoride pellets

Optically Stimulated Luminescent Response of the LiMgPO4 Silicone Foils to Protons and Its Dependence on Proton Energy

Modern radiotherapy (RT) techniques, such as proton therapy, require more and more sophisticated dosimetry methods and materials. One of the newly developed technologies is based on flexible sheets made of a polymer, with the embedded optically stimulated luminescence (OSL) material in the form of powder (LiMgPO4, LMP) and a self-developed optical imaging setup. The detector properties were evaluated to study its potential application in the proton treatment plan verification for eyeball cancer. The data showed a well-known effect of lower luminescent efficiency of the LMP material response to proton energy. The efficiency parameter depends on a given material and radiation quality parameters. Therefore, the detailed knowledge of material efficiency is crucial in establishing a calibration method for detectors exposed to mixed radiation fields. Thus, in the present study, the prototype of the LMP-based silicone foil material was tested with monoenergetic uniform proton beams of various initial kinetic energies constituting the so-called spread-out Bragg peak (SOBP). The irradiation geometry was also modelled using the Monte Carlo particle transport codes. Several beam quality parameters, including dose and the kinetic energy spectrum, were scored. Finally, the obtained results were used to correct the relative luminescence efficiency response of the LMP foils for monoenergetic and spread-out proton beams.

Using the optically stimulated luminescence technique for one- and two-dimensional dose mapping: a brief review

In respect of radiation dosimetry, several applications require dose distribution verification rather than absolute dosimetry. Most protocols use radiological and radiochromic films and ionization chambers or diode arrays for dose mapping. The films are disposable which causes the precision of the results dependent on film production variability. The measurements with arrays of ionization chambers or diodes mainly lack spatial resolution. This review aims to provide an overview of the use of optically stimulated luminescence detectors (OSLDs) for one-dimensional (1D) and two-dimensional (2D) dose mapping in different applications. It reviews the ideas, OSL materials, and applications related to the assessment of dose distribution using OSLDs in the form of film or ceramic plate (BeO). Additionally, it reviews research published in the international scientific literature from 1998 to 2021. As an outcome, a table containing the main characteristics of each relevant paper is shown. The results section was divided by the type of OSL material, and we briefly described the principal findings and the significant developments of each mentioned study such as film production and OSL reader assembly. The purpose of this study was to present an overview of the main findings of several research groups on the use of OSLD in the form of film or plate for 1D and 2D dose mapping. Finally, the potential future development of dose mapping using OSLD films was outlined.

Thermoluminescence (TL), kinetic parameters and dosimetric features of Pakistani limestone

Thermoluminescence (TL), kinetic parameters and dosimetric features of Pakistani limestone (CaCO₃) is reported in this study. Both compositional and structural analyses reveal that the material has a crystalline nature with rhombohedral structure and non-uniform crystallite size having major content of CaCO₃. A powdered limestone sample of 30 mg is found to be the optimized weight for TL and other dosimetric studies. After irradiating the samples with a test dose of 100 Gy using a β source three composite glow peaks termed as P1, P2 and P3 are visible at 100, 230 and 330 °C respectively using a linear heating rate of 1 °C/s during the TL readout. The Coefficient of Variation (COV) is found to be about 4%. Kinetic parameters (i.e., frequency factor (f), activation energy (E), and the kinetic order (b)) are estimated using both first and second Order of kinetics using an in-house Computerized Glow Curve Deconvolution (GCD) software. The figure-of-merit (FOM) is found to be 2.12%. The distribution of continuum traps with activation energy in the range of 0.77-2.59 eV is observed in the kinetic parameter analysis of the glow peaks of the sample. The TL response in the dose range of 1-5 Gy (not reported previously) and linearity in the dose response in the dose range of 1-10 Gy is observed in samples of Pakistani limestone. The Minimum Detectable Dose (MDD) is 1.01 Gy clearly resembling the experimentally linear fitted results. After a fading study for a period of thirty days, only the first peak i.e., P1 majorly fades while no major change is observed in the amplitude of peaks P2 and P3. In addition, P1 is the main contributor fading by 92% within the first 24 h of irradiation while P2 fades by 30 %. However, P3 shows stability with a very minor fading of 0.05% within 24 h of irradiation. This study concludes that Pakistani limestone can be further assessed as a potential radiation dosimeter for various applications.

Correlation between thermoluminescence and optically stimulated luminescence responses of natural alexandrite

Luminescent properties of alexandrite crystals (BeAl₂O₄:Cr³⁺) are studied. Partial readouts of thermoluminescence (TL) and optically stimulated luminescence (OSL) signals were obtained to infer the relations of OSL and TL trapping centers. Four TL peaks were studied; their intensities decrease at different rates by illumination with blue OSL light. The OSL curve shows two-time components (exponential decay constants 3.15 and 28.4 s). The short time component is preferentially diminished when the sample is heated to temperatures from 363 to 513 K. About 50% of the whole TL intensity remains after a complete 300s OSL readout.

Response of TL and OSL passive personal dosimetry systems in poly-energetic and multi-directional photon radiation fields

The aim of this paper is to examine the energy and angular responses of thermoluminescent dosimeters containing either MTS-N (LiF:Mg,Ti) or MCP-N (LiF:Mg,Cu,P) detector materials, and of the InLight optically stimulated luminescent dosimeters containing Al₂O₃:C detectors. Ten radiation qualities, with mean energies ranging from 24 keV to 1.25 MeV, and five angles of incidence, between 0° and 80°, were used for this purpose. The dosimeter response measure of quality were the IEC 62387 requirements. The experimental results show that the MTS-N-based and the InLight dosimeters performed in line with the standard's criteria. On the other hand, the MCP-N-based dosimeters exhibited a pronounced under-response around the energy of 120 keV, which resulted in deviations from the standard's conditions for both the energy and angular responses.