A CaS:Ce,Sm-based dosimeter for online dosimetry measurement
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A film dosimeter based on optically stimulated luminescence (OSL) material of CaS:Ce,Sm was developed for online irradiation dosimetry measurement. The stimulation is provided by a laser with a wavelength of 980 nm, and the OSL luminescenceis collected by a photodiode. Using (60)Co gamma-rays, we investigated the dosimetry characteristic of the dosimeter at different dose rates and total doses. The real-time detection results showed that the OSL signals versus total ionizing dose exhibited a good linearity in a dose range of 0.1-185 Gy.Keywords:
Optically stimulated luminescence
The aim of this work is to propose a new methodological approach, using TLD400, to perform point dosimetry in medical physics applications. It investigates the possibility of using simultaneously the luminescence signals by optical stimulation with blue diode (OSL) and residual signals by thermal stimulation (ReTL), from TLD400, CaF2:Mn, for dosimetric purposes. Artificial irradiation was performed with 90Sr-90Y, calibrated beta sources delivering 6 Gy/min and integrated in the TL-DA-15 automated RisØ readers equipped with EMI 9235QA photomultipliers. In particular, for OSL measurements, to check the correct experimental conditions, the effect of the stimulation temperature during optical stimulation and the effect of the optical stimulation time were studied. For calibration curves from OSL and ReTL signals, a double Single Aliquot Regeneration (SAR) procedure was used, in which the "sensitivity-corrected" natural stimulated luminescence signal is compared with equivalent sensitivity-corrected signals regenerated by laboratory irradiation of the same aliquot. The double OSL and ReTL combined measurements allow to have a good accuracy coverage (⩽2%) in the whole dose range between 0 and 10 Gy.
Optically stimulated luminescence
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The current study was performed to investigate the influence of high temperature on the value of radiation dose measured by optically stimulated liminescence (OSL) dosimeter or radio photo luminescence (RPL) dosimeter (glass dosimeter) . Serial measurements of temperature in the car confirmed that it can rise to 80°C or higher in the area irradiated with sun beam. The relationship between the temperature and the radio dose measured by X-ray irradiated OSL dosimeter or glass dosimeter under the condition from 50°C to 90°C after the set of 3h. to 72h.The value measured by OSL dosimeter tended to be lower with higher temperature or longer setting time. On the other hand, those factors did not influence the value measured by glass dosimeter.
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This study investigated the feasibility of dosimetric measurements using Al2O3:C optically stimulated luminescence (OSL) dosimeters during fluoroscopy-guided procedures. The linearity and energy dependence of Al2O3:C OSL dosimeters were evaluated, and the air kerma rate at the operator's position was measured. The response of Al2O3:C OSL dosimeters to short, repetitive irradiations was compared to that of long uninterrupted irradiation. The change in response of the Al2O3:C OSL dosimeter under automatic exposure rate control (AERC) was evaluated with the use of various thicknesses of polymethyl-methacrylate (PMMA) plates (15-30 cm). The Al2O3:C OSL dosimeters could detect 5µGy and showed good linearity in doses of ≥10µGy (R2: 0.997-0.999,p< 0.001). The relative response of the Al2O3:C OSL dosimeter normalised to that of 36.8 keV was 0.828-1.101 at the energies investigated (30.6-46.0 keV). The air kerma rate at the operator's position was estimated to be 2.61-7.17µGy min-1depending on the heights representing different body parts. Repetitive short irradiations had no significant impact on the relative response of the Al2O3:C OSL dosimeters (p> 0.05). Despite a high energy dependence on the low energy beam used in fluoroscopy, the change in relative response of the Al2O3:C OSL dosimeter under AERC was within 5.7% depending on the thickness of the PMMA plates. Dosimetric measurement using Al2O3:C OSL dosimeters for patients and operators is feasible. However, one should be cautious about high standard deviations when measuring small doses of ≤20µGy using Al2O3:C OSL dosimeters. It is essential to perform intensive bleaching before measuring very small doses to minimise pre-irradiation counts.
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Optically stimulated luminescence
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The development of OSL dosimeter made from Al2O3:C turned out to be able to reduce the limitations of thermoluminescence dosimeter in terms of the heating process, the speed of analysis, and the ability to do a rereading.This study was conducted to obtain the characteristics of commercial OSL dosimeters which include linearity, fading effect, and reproducibility.Twenty eight environmental OSL dosimeters were annealed and divided into seven groups, each consisting of four dosimeters.Group 1 to 6 were irradiated with 137 Cs gamma at various doses, whereas group 7 was as control.Reproducibility testing was done by exposing ten dosimeters by 1 mSv of 137 Cs gamma.Results showed that after reading and analyzed, it was obtained the curve of the reading dose to the exposure dose with the equation of y = 1.0566x -0.2499 and the correlation factor R 2 = 0.9999.There was no fading effect obtained in the reading dose on the 31 st day.While the dose reading on the 70 th daywas obtained a decrease of 0.12 mSV and 0.34 mSv for exposure doses of 5 mSv and 10 mSv, respectively.The result shows that the average coefficient of dose variation for ten dosimeters that were read once was 9.7% and the average coefficient of variation for 1 dosimeter that was read ten times was 4.2%.The average coefficient ofdose variation was greater than the results of previous study which were 2.5% and 1.8%, respectively Kata kunci
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Secondary Standard Dosimetry Laboratory (SSDL) Department, of Malaysian Nuclear Agency (nuclear Malaysia) is responsible for monitoring radiation worker in Malaysia. All radiation workers in Malaysia is monitor using two kind of personal dosimeter either, film badge or thermo luminescent (TL) dosimeter .In the year 2015, SSDL Nuclear Malaysia plan to terminate all film badge services and switch to Optically Stimulated Luminescene (OSL) dosimeter. This OSL dosimeter is the new kind personal dosimeter in Malaysia. OSL dosimeter is sensitive to low dosage as low as 0.05 miliSievert (mSv) up to 10000 mSv. OSL can detect photon (x-ray and gamma ray), beta and neutron radiation. It can be re-read and very simple to maintain. OSL dosimeter can estimate and detect deep dose or personal dose equivalent in 10 mm tissue (Hp(lO)mSv), shallow dose or skin dose or personal dose equivalent in 0.07 mm tissue (Hp(0.07),mSv) and also can detect lens dose or personal dose equivalent in 3 mm in lens tissue (Hp(3),mSv). Radiation exposure in OSL dosiemeter is measure using Microstar Reader , this happen when by stimulating the detector that is aluminium oxide (A1203:C) crystal, with a green Light Emitting Diode (LED) array causing the luminescent phenomena which proportion to the amount of radiation absorbed. During the stimulation only some trapped electrons are released so the dosimeter can be re-read. Currently SSDL-Nuclear Malaysia already purchases nearly 2000 new OSL dosimeter. As a new dosimeter this OSL dosimeter need to undergo some type testing such as linearity response test, energy response test, angular response test and repeatability response test. This research project will use irradiation facility and OSL MICROSTAR READER situated in SSDL Nuclear Malaysia facility. This research proposal is to study the linearity of OSL dosimeter base on the response of shallow dose or skin dose or personal dose equivalent in
Optically stimulated luminescence
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Optically stimulated luminescence
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