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Abstract A two-dimensional (2D) dosimeter has been developed using tissue-equivalent NaMgF 3 :Eu as a radiation-sensing material. The bulk compound shows optically stimulated luminescence (OSL) after irradiation in the form of 359 nm Eu2+ emission and where the OSL stimulation occurs at wavelengths above 400 nm. The OSL integrated intensity is shown to be linear up to at least 100 Gy when stimulated with 445 nm light. When the OSL is detected using a thermoelectrically cooled CCD camera, 2D X-ray images can be obtained and the measured intensity is proportional to the total radiation dose. NaMgF 3 :Eu can be incorporated into epoxy to produce imaging films and both the bulk compound and a film are characterised using the 2D setup. The noise equivalent dose in 2D for the bulk is determined to be 14 mGy. The modulation transfer function (MTF) is determined and the spatial resolution at MTF = 0.2 is 2.9 lp/mm for the bulk material and 1.25 lp/mm for the film. Our results show that NaMgF 3 :Eu has potential in the field of 2D dosimetry, where the response to radiation is linear to high doses, sensitive to low doses, and doses can be resolved with a spatial resolution below 1 mm. Highlights • A 2D dosimeter system has been demonstrated using NaMgF 3 :Eu. • OSL is observed after irradiation that is linear up to at least 100 Gy. • The 2D system can detect radiation doses as low as 14 mGy. • Both bulk crystals and films show spatial resolutions less than 1 mm. [ABSTRACT FROM AUTHOR]

Abstract Photoluminescence (PL) and radioluminescence (RL) were observed in both bulk polycrystalline and nanoparticle KMgF 3 (Eu). Eu2+ and Eu3+ emissions were detected in the PL of both samples. The nanoparticles had more Eu3+, more distorted Eu3+ sites, and a higher PL quantum efficiency when compared to the bulk compound. X-ray-induced valence conversion of Eu2+ to Eu3+ was observed in the bulk, while Eu3+ to Eu2+ was found for nanoparticles. The valence conversion was reversed for the bulk compound by UV bleaching (254 nm) and partially reversed in the nanoparticles by 330 nm stimulation. F 2 and F 3 -centre PL was observed in the bulk after X-ray irradiation but was absent in the nanoparticles. PL from other point defects occurred in both samples that is likely to be oxygen related. The PL from one of these defects in the nanoparticles changed with X-ray irradiation or UV illumination and the PL slowly recovered at room temperature. We propose this may be due to charge-transfer in O2--F+ pairs where this defect could potentially be used in a solar UV dosimeter. Optically stimulated luminescence was observed only from Eu2+ in the bulk material that can be used for dose monitoring after irradiation. It was absent in the nanoparticles, which may be due to the absence of fluorine related point defects. The bulk RL from Eu2+ and Eu3+ had significant dose-history dependence that could be corrected for. The nanoparticles had RL that was independent of dose history after ~ 4 kGy. Thus, bulk and nanoparticle KMgF 3 (Eu) may have potential application as an RL dosimeter. [ABSTRACT FROM AUTHOR]

The optically stimulated luminescence of a NaMgF 3 :Mn/epoxy composite has been used for two-dimensional X-ray dose imaging using a thermoelectrically cooled CCD camera to detect the luminescence. Exposing the material to ionising radiation filled defects that could be optically stimulated at 365 nm and that yielded Mn2+ emission at 590 nm. The optically stimulated luminescence intensity was directly proportional to radiation dose and was linear with dose from 20 mGy up to at least 2.9 Gy. Two-dimensional dose maps could be obtained in 2 s and the noise-equivalent dose was calculated to be < 10 mGy. The modulation transfer function (MTF) defined the spatial resolution of the system as 1.4 line pairs/mm at MTF = 0.2. Our results indicate that the NaMgF 3 :Mn/epoxy composite has properties that are promising for applications in two-dimensional dosimetry that include a linear response to radiation over a wide dose range and a high sensitivity to low doses. Coupled with a CCD readout system, images can be collected in short times on the order of seconds, and the system is capable of monitoring sub-millimetre dose variations. [Display omitted] • A two-dimensional optically stimulated dosimeter system has been developed. • The dose response of the NaMgF 3 :Mn/epoxy is linear from 20 mGy to at least 2.9 Gy. • The system is sensitive to spatial dose variations < 1 mm and doses < 10 mGy. • Two-dimensional dose maps can be measured in below 2 s [ABSTRACT FROM AUTHOR]

Abstract Luminescence measurements were made on NaMgF 3 :Mn before and after irradiation with X-rays over a wide Mn concentration range from x = 0.1%–5%. Photoluminescence (PL) is seen from distorted Mn2+ sites that saturate for x ≥ 1% and non-distorted Mn2+ sites. The non-distorted Mn2+ crystal field parameter and crystal field splitting are independent of Mn concentration and they are B = 779 ± 14 cm−1 and 10 Dq = 9250 ± 160 cm−1. F-centre/Mn complexes are seen for all concentrations with a PL emission at ∼670 nm. The complexes have perturbed Mn2+ energy levels that shift by less than 1630 cm−1 in the 320 nm–570 nm wavelength range. There is also a PL emission at ∼730 nm that is likely to arise from F 3 -centres perturbed by nearby Mn. The PL from these two perturbed centres is linear in dose up to 3.8 kGy when probed in the 550 nm–650 nm region and it can be repeatedly probed without bleaching. Optically stimulated luminescence (OSL) occurs for all Mn concentrations from the non-distorted Mn2+ site after X-ray irradiation. The OSL intensity is linear up to ∼270 Gy for 0.5% Mn and the trapped carriers can be selectively bleached. Radioluminescence (RL) is also observed in all samples from both Mn2+ sites. Not all Mn2+ displays RL and a larger fraction of distorted Mn2+ sites do not display RL, which may be due to a higher concentration of nearby non-radiative recombination sites. The ratio of the RL of the non-distorted Mn2+ to the distorted Mn2+ is nearly dose-history-independent after an initial predose for 0.1% Mn, and it is linear in dose up to 9.6 kGy for 5% Mn. Our results show that NaMgF 3 :Mn has great potential for real-time and total dose measurements where there are complementary methods available to obtain the dose rate, the dose-history, the dose after each irradiation, and the cumulative dose up to very high doses. Graphical abstract Image 1 Highlights • The luminescence of NaMgF 3 :Mn with different Mn concentrations was investigated. • The transition energies of the F-centre/Mn complexes were determined. • Optically stimulated luminescence of Mn2+ is linear to 270 Gy. • F-centre/Mn photoluminescence can non-destructively monitor doses up to 3.8 kGy. • Mn2+ radioluminescence can be used to monitor doses up to at least 11 kGy. [ABSTRACT FROM AUTHOR]

Infrared radiophotoluminescence was observed in NaMgF 3 :Tm from the X-ray-induced reduction of Tm3+ → Tm2+. The 4 f 13(2F 5/2) → 4 f 13(2F 7/2) Tm2+ emission only appeared after irradiation and peaked at 1130 nm where the emission energy was compressed by a factor of 1.15 times relative to isoelectronic Yb3+ in NaMgF 3 :Yb. The Tm2+ emission intensity increased monotonically with absorbed dose up to at least 360 Gy and the integrated intensity increased linearly up to at least 60 Gy. The Tm2+ photoluminescence could be probed non-destructively by exciting into the peak of the lowest energy 4 f 13 → 4 f 125 d 1 band at 450 nm, and destructively probed using stimulation at 280 nm, whereupon the photo-induced oxidation Tm2+ → Tm3+ occurred. Additionally, Tm3+ optically stimulated luminescence was observed after irradiation when stimulating into the F-centre absorption band at 340 nm. The optically reversible radiophotoluminescence and optically stimulated luminescence phenomena have potential applications in radiation dose monitoring and optical information storage. • Photoluminescence and radiophotoluminescence of Tm-doped NaMgF 3 is presented. • The X-ray induced reduction Tm3+.→ Tm2+ was observed via radiophotoluminescence • The Tm2+ emission intensity increased with total X-ray dose. • Tm2+ radiophotoluminescence could be non-destructively probed via 4 f 125 d 1 excitation. [ABSTRACT FROM AUTHOR]

Abstract: We report the results of optical, photo-luminescence and spatial resolution measurements on glass-ceramic and epoxy-composite X-ray storage phosphors. We find that the optical extinction coefficient at the stimulation and emission wavelengths is dominated by scattering for all the samples studied. However, the extinction coefficient is at least an order of magnitude lower in glass-ceramics when compared with the composites. Significantly reduced scattering is found in a composite due to the better match between the refractive indices of the epoxy and crystallite. We show that the spatial resolution using a confocal microscope readout in a glass-ceramic is below and hence this glass-ceramic has potential applications in high resolution radiation imaging. [Copyright &y& Elsevier]

Photoluminescence (PL) and radioluminescence (RL) measurements were made on both nanoparticle and bulk NaMgF 3 :Ce,Sm, before, during, and after X-ray irradiation. The relative concentrations of Sm3+ and Sm2+ were markedly different for the nanoparticle and bulk samples. Sm3+ dominated the PL in NaMgF 3 :Ce,Sm nanoparticles while the bulk sample showed Sm3+ and Sm2+ PL. Ce3+ PL and Ce3+ sensitisation of the Sm3+ PL emission was observed for nanoparticle and bulk samples. In both samples we observed the radiation-induced valence conversions Sm3+ → Sm2+ and Ce3+ → Ce4+, such that the PL intensities of each valence could be used to monitor radiation doses. A more intense PL from oxygen-related point defects was found in nanoparticles that decreased with radiation dose and hence may also be used for radiation dosimetry. Sm3+, Sm2+, and Ce3+ RL was seen in the bulk sample where the RL depended on the dose and the Ce3+ RL was independent of the dose above ~4 kGy. Only Sm3+ and Sm2+ RL was found in nanoparticles where the Sm3+ RL decreased by only 0.5%/kGy above 3 kGy. Our results show that nanoparticle and bulk NaMgF 3 :Ce,Sm can potentially be used as PL and RL dosimeters, where the signals from Ce3+, Sm2+, Sm3+, and the oxygen-related defect provide multiple means of measuring real-time and cumulative doses that may be useful for radiotherapy quality assurance. • Luminescence from Ce, Sm, and defects was seen in bulk and nanoparticle NaMgF 3 :Ce,Sm. • Sm3+ PL dominated in the nanoparticles while Sm3+ and Sm2+ PL occurred in the bulk. • Sensitisation of Sm3+ by Ce3+ was observed in both the nanoparticles and the bulk. • X-ray exposure caused the conversions Ce3+.→ Ce4+ and Sm3+ → Sm2+. • The RL of Sm2+ in nanoparticles and Ce3+ in bulk was constant after a priming dose. [ABSTRACT FROM AUTHOR]