Callens, Freddy

de Freitas Nascimento, Luana

Kusakovskij, Jevgenij

Lowie, Lars

Maes, Kwinten

Vrielinck, Henk

English

Ghent University Academic Bibliography

EPR STUDY OF LUMINESCENCE-BASED RADIATION DOSIMETERS1GHENT UNIVERSITY DEPARTMENT OF SOLID STATE SCIENCES, EMR RESEARCH GROUP2SCK•CEN BELGIAN NUCLEAR RESEARCH CENTRE, RADIATION PROTECTION DOSIMETRY AND CALIBRATION GROUPK. Maes1, L. Lowie1, J. Kusakovskij1, L. de F. Nascimento2, H. Vrielinck1, F. Callens1IntroductionElectron paramagnetic resonance (EPR) is a physical method to observe resonant absorption of microwave radiation by unpaired electron spins in a magnetic field. It is able to detect, identify and quantify free radicals, such as those present in irradiated materials. This makes it a reliable dosimetric technique  for retrospective/accident dosimetry, detection of irradiated food, e.g. using alanine, tooth enamel and sucrose. It finds applications in geology, chemistry, physics, medicine, environmental sciences, archaeology, and industrial irradiations. 1 In the present study, we discuss results on two classes of materials, i.e. LiF:Mg,Ti /LiF:Mg,Cu,P and Al2O3:C /Al2O3:C,Mg. These materials are used in thermoluminescence dosimetry (TLD) and Optically Stimulated Luminescence dosimetry (OSLD)/Radiophotoluminescence dosimetry (RPLD) respectively.2-4 In terms of dose sensitivity EPR cannot compete with these luminescence methods, but it can provide complementary insight into the defects and processes leading to luminescence. ContactKwinten MaesPhD assistantDEPARTMENT OF SOLID STATE SCIENCEEMR RESEARCH GROUPE kwinten.maes@ugent.beT +32 9 264 43 51www.ugent.beGhent University@ugentGhent UniversityReferences1. M. Ikeya, New applications of electron spin resonance: dating, dosimetry and microscopy. (World Scientific Publishing, 1993).2. E. G. Yukihara, and Stephen WS McKeever, Optically stimulated luminescene: fundamentals and applications. (John Wiley & Sons, 2011).3. M. J. Aitken, Thermoluminescence dating. (Academic press, 1985).4. L. F. Nascimento, M. Karampiperi, J. P. Oliveira and F. Vanhavere, Radiation Measurements (2017).5. R R Patil and S.V.Moharil, J. Phys.: Condens. Matter 7 (025), 9925-9933 (1995).AcknowledgementsThis work is, in part, supported by the Special Research Fund of Ghent UniversityAl2O3:C /Al2O3:C,Mg X-band EPR comparison, RTX-Band measurementsBoth systems were measured before andafter X-ray irradiation. Before irradiation, there was no significant EPR signal visible.After irradiation a broad isotropic signal appeared. Although the signal looks similarfor both, they are in fact slightly different:Al2O3:C,Mgg = 2,011 lwpp = 4,3 mTAl2O3:Cg = 2,008 lwpp = 5,3 mTX-band EPR dose dependence Al2O3:C, RTTheir intensities are also different. TheAl2O3:C,Mg EPR signal is smaller by a factorof around 2 for the same dose received.Dose dependenceOnly Al2O3:C is shown, Al2O3:C,Mggave similar results.Looking at the dose dependence there is a clear increase in intensity in function of dose received for both. Plotting the EPR intensity in function of                                    Fitted dose dependence Al2O3:Cdose gives an exponential curve from which we could derive an estimate of the saturation dose:Fit Al2O3:C,Mg:𝐼 = 𝐼0 ∗ (1 − 𝑒−𝐷58,8 𝐺𝑦)Fit Al2O3:C:𝐼 = 𝐼0 ∗ (1 − 𝑒−𝐷66,7 𝐺𝑦)For both samples the saturation dose is around 60 Gy, close to the OSL/RPL saturation dose. LiF:Mg,Ti X-Band EPR, RTX-Band measurements, RTMeasurements before irradiation did not reveal a significant EPR signal.After irradiation a signal appears, buteven for 1 kGy of dose, the intensity remainsvery low.g = 2,014 lwpp = 3,8 mTLiF:Mg,Cu,P Q-Band EPR, RTQ-Band measurementsFor this system a signal is present beforeirradiation.g┴ = 2,204  g// = 2,068  lw = 8,3 mT (Lorentzian)Irradiating the sample did not change the intensity of the signal, nor its shape.LiteraturePatil and Moharil 1995 5g┴ = 2,191  g// = 2,073   (X-band, RT)The signal is proposed Cu-related. Prediction g-values Cu2+Crystal Field Theory DFT calculationsdx²-y²: g// > g┴ > 2 g┴= 2,115 < g//=2,259d3z²-r²: g┴ > g// ≈ 2 g┴= 2,219 >g//=2,005 Q-band EPR + ENDOR, 5KCFT predicts that the unpaired electron iseither in dx²-y² or in d3z²-r² orbital. For theseorbitals theoretical g-values can becalculated. DFT calculations confirmed theCFT predictions. However, comparing this tothe experimentally derived g-values, neither really fit.Q-band ENDOR measurementsElectron Nuclear Double Resonance (ENDOR):Detecting NMR transitions via EPR.First results reveal signals at the Larmorfrequencies of 7Li and  19F from distant nuclei. Around νlarmor(19F) a signal is visible with a hyperfine coupling of 0,9 MHz due toa neighbouring F nucleus.Conclusions Al2O3:C and Al2O3:C,Mg have an EPR signal that is dose sensitive The EPR signal of Al2O3:C is more sensitive to radiation compared to the EPR signal of Al2O3:C,Mg The saturation dose is around 60 Gy, in agreement with OSL saturation dose LiF:Mg,Cu,P has an EPR signal present that is not dose sensitive The signal could be related to Cu2+, however more research is needed The first ENDOR spectra look promising330 335 340 345Intensity (arb. units)Field (mT) Al2O3:C 0Gy Al2O3:C 11Gy Al2O3:C 33Gy Al2O3:C 77Gy Al2O3:C 110Gy Al2O3:C 330Gy330 335 340 345Intensity (arb. units)Field (mT) Al2O3:C,Mg 330Gy Al2O3:C 330Gy325 330 335 340 345 350Intensity (arb. units)Field (mT) LiF:Mg,Ti 0Gy LiF:Mg,Ti 990Gy1050 1100 1150 1200Intensity (arb.units)Field (mT) LiF:Mg,Cu,P not irradiated LiF:Mg,Cu,P 110Gy0 50 100 150 200 250 300 350Intensity (arb.units)Dose (Gy)fitExp. data1042 mT1112 mT1146 mT1176 mT1224 mT

EPR study of luminescence-based radiation dosimeters

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EPR study of luminescence-based radiation dosimeters

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