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Pr-doped BaTi4O9 crystals were grown by the floating zone method, and their optical and near-infrared (NIR) radioluminescence (RL) properties were investigated. The photoluminescence and RL properties observed comprised several sharp peaks around 630 nm due to 4f–4f transitions of Pr3+ ions. In the NIR range, strong emission peaks around 1100 nm were confirmed, and the RL intensity of 1.0% Pr-doped crystals was the highest among the prepared crystals. The minimum sensitivity of the detector was 0.3 Gy h−1 for the 1.0% Pr-doped crystal.

Purpose.In this study, spatio-temporal beam profiling for electron ultra-high dose rate (UHDR; >40 Gy s-1) radiation via Cherenkov emission and radioluminescence imaging was investigated using intensified complementary metal-oxide-semiconductor cameras.Methods.The cameras, gated to FLASH optimized linear accelerator pulses, imaged radioluminescence and Cherenkov emission incited by single pulses of a UHDR (>40 Gy s-1) 10 MeV electron beam delivered to the isocenter. Surface dosimetry was investigated via imaging Cherenkov emission or scintillation from a solid water phantom or Gd2O2S:Tb screen positioned on top of the phantom, respectively. Projected depth-dose profiles were imaged from a tank filled with water (Cherenkov emission) and a 1 g l-1quinine sulfate solution (scintillation). These optical results were compared with projected lateral dose profiles measured by Gafchromic film at different depths, including the surface.Results.The per-pulse beam output from Cherenkov imaging agreed with the photomultiplier tube Cherenkov output to within 3% after about the first five to seven ramp-up pulses. Cherenkov emission and scintillation were linear with dose (R2 = 0.987 and 0.995, respectively) and independent of dose rate from ∼50 to 300 Gy s-1(0.18-0.91 Gy/pulse). The surface dose distribution from film agreed better with scintillation than with Cherenkov emission imaging (3%/3 mm gamma pass rates of 98.9% and 88.8%, respectively). Using a 450 nm bandpass filter, the quinine sulfate-based water imaging of the projected depth optical profiles agreed with the projected film dose to within 5%.Conclusion.The agreement of surface dosimetry using scintillation screen imaging and Gafchromic film suggests it can verify the consistency of daily beam quality assurance parameters with an accuracy of around 2% or 2 mm. Cherenkov-based surface dosimetry was affected by the target's optical properties, prompting additional calibration. In projected depth-dose profiling, scintillation imaging via spectral suppression of Cherenkov emission provided the best match to film. Both camera-based imaging modalities resolved dose from single UHDR beam pulses of up to 60 Hz repetition rate and 1 mm spatial resolution.

Objective. Non-invasive light delivery into the brain is needed for in vivo optogenetics to avoid physical damage. An innovative strategy could employ x-ray activation of radioluminescent particles (RLPs) to emit localized light. However, modulation of neuronal or synaptic function by x-ray induced radioluminescence from RLPs has not yet been demonstrated. Approach. Molecular and electrophysiological approaches were used to determine if x-ray dependent radioluminescence emitted from RLPs can activate light sensitive proteins. RLPs composed of cerium doped lutetium oxyorthosilicate (LSO:Ce), an inorganic scintillator that emits blue light, were used as they are biocompatible with neuronal function and synaptic transmission. Main results. We show that 30 min of x-ray exposure at a rate of 0.042 Gy s−1 caused no change in the strength of basal glutamatergic transmission during extracellular field recordings in mouse hippocampal slices. Additionally, long-term potentiation, a robust measure of synaptic integrity, was induced after x-ray exposure and expressed at a magnitude not different from control conditions (absence of x-rays). We found that x-ray stimulation of RLPs elevated cAMP levels in HEK293T cells expressing OptoXR, a chimeric opsin receptor that combines the extracellular light-sensitive domain of rhodopsin with an intracellular second messenger signaling cascade. This demonstrates that x-ray radioluminescence from LSO:Ce particles can activate OptoXR. Next, we tested whether x-ray activation of the RLPs can enhance synaptic activity in whole-cell recordings from hippocampal neurons expressing channelrhodopsin-2, both in cell culture and acute hippocampal slices. Importantly, x-ray radioluminescence caused an increase in the frequency of spontaneous excitatory postsynaptic currents in both systems, indicating activation of channelrhodopsin-2 and excitation of neurons. Significance. Together, our results show that x-ray activation of LSO:Ce particles can heighten cellular and synaptic function. The combination of LSO:Ce inorganic scintillators and x-rays is therefore a viable method for optogenetics as an alternative to more invasive light delivery methods.

This study aims to demonstrate a low-cost camera-based radioluminescence imaging system (CRIS) for high-quality beam visualization that encourages accurate pre-treatment verifications on radiation delivery in external beam radiotherapy. To ameliorate the optical image that suffers from mirror glare and edge blurring caused by photon scattering, a deep learning model is proposed and trained to learn from an on-board electronic portal imaging device (EPID). Beyond the typical purposes of an on-board EPID, the developed system maintains independent measurement with co-planar detection ability by involving a cylindrical receptor. Three task-aware modules are integrated into the network design to enhance its robustness against the artifacts that exist in an EPID running at the cine mode for efficient image acquisition. The training data consists of various designed beam fields that were modulated via the multi-leaf collimator (MLC). Validation experiments are performed for five regular fields ranging from 2 × 2 cm2 to 10 × 10 cm2 and three clinical IMRT cases. The captured CRIS images are compared to the high-quality images collected from an EPID running at the integration-mode, in terms of gamma index and other typical similarity metrics. The mean 2%/2 mm gamma pass rate is 99.14% (range between 98.6% and 100%) and 97.1% (ranging between 96.3% and 97.9%), for the regular fields and IMRT cases, respectively. The CRIS is further applied as a tool for MLC leaf-end position verification. A rectangular field with introduced leaf displacement is designed, and the measurements using CRIS and EPID agree within 0.100 mm ± 0.072 mm with maximum of 0.292 mm. Coupled with its simple system design and low-cost nature, the technique promises to provide viable choice for routine quality assurance in radiation oncology practice.

The purpose of this study is to leverage radioluminescence imaging for the development of an automated high-dose-rate (HDR) brachytherapy quality assurance (QA) system that enables simultaneous measurements of dwell position, dwell time, wire velocity, and relative source strength in a single test. The system consists of a radioluminescence phosphor sheet (a mixture of Gd2O2S:Tb and PDMS) positioned atop a HDR needle applicator, a complementary metal-oxide-semiconductor digital camera used to capture the emitted radioluminescence signals from the scintillator sheet, and an in-house graphical user interface for signal processing. The signal processing was used to extract source intensity, location, and elapsed time, yielding the final measurements on dwell position, dwell time, and wire velocity. The source strength relative to the well chamber calibration (in unit of Air-Kerma strength, Sk ) is measured by establishing a calibration curve that correlates Sk with the detector response. Validation experiments are performed using three customized treatment plans. With these plans, the dwell position and dwell time are verified for a range of 110.0 cm–117.5 cm and 2 s–16 s, respectively, and the linear correlation with Sk is demonstrated for the source strength varying between 28 348 U (cGy cm2 h−1) and 41 906 U. The wire velocity, i.e. the speed of the radioactive source averaged over the distance in between dwell positions, is calculated for various distances ranging from 5 mm to 50 mm. Results show that the mean deviations of the measured dwell position and dwell time are 0.1 mm (range from 0 to 0.2 mm) and 32.5 ms (range from 0 to 60.0 ms) with respect to the planned values, respectively, and the system response is highly linear with Sk ( R2 = 0.998). Moreover, the measured wire velocities are comparable to previously reported values. Benefitting from the compact hardware design and image processing algorithms, the system provides a practical, reliable, and comprehensive solution for HDR QA.

Radioluminescence by protons and carbon ions of energy lower than the Cherenkov threshold (∼260 keV) in water has been observed. However, the origin of the luminescence has not been investigated well. In the present work, we imaged radioluminescence in water using synchrotron radiation that was of sufficiently lower energy (11 keV) than the Cherenkov threshold and we measured its spectrum using a high-sensitivity cooled CCD camera and optical longpass filters having 5 different thresholds. In addition, to determine effects of impurities in water, the water target was changed from ultrapure water to tap water. Monte Carlo simulation (Geant4) was also performed to compare its results with the experimentally obtained radioluminescence distribution. In the simulation, photons were generated in proportion to the energy deposition in water. As a result, the beam trajectory was clearly imaged by the radioluminescence in water. The spectrum was proportional to λ −3.4±0.4 under an assumption of no peaks. In the spectrum and distribution, no differences were observed between ultrapure water and tap water. TOC (total organic carbon) contents of ultrapure water and tap water as an impurity were measured and these were 0.26 mg l−1 and 2.3 mg l−1, respectively. The radioluminescence seemed to be attributable to water molecules not impurities. The radioluminescence distribution of the simulation was consistent with the experimental distribution and this suggested that radioluminescence was proportional to dose, which is expected to allow use for dose measurement.

A dosimetry system based on Al2O3:C radioluminescence (RL), and RADPOS, a novel 4D dosimetry system using microMOSFETs, were used to measure total scatter factors, (S(c,p))(f(clin))(det), for the CyberKnife robotic radiosugery system. New Monte Carlo calculated correction factors are presented and applied for the RL detector response for the 5, 7.5 and 10 mm collimators in order to correct for the detector geometry and increased photoelectric cross section of Al2O3:C relative to water. For comparison, measurements were also carried out using a micro MOSFET, PTW60012 diode and GAFCHROMIC(®) film (EBT and EBT2). Uncorrected (S(c,p))(f(clin))(det) were obtained by taking the ratio of the detector response for each collimator to that for the 60 mm diameter reference field. Published Monte Carlo calculated correction factors were applied to the RADPOS, microMOSFET and diode detector measurements to yield corrected field factors, Ω(f(clin),f(msr))(Q(clin),Q(msr)), following the terminology of a recent formalism introduced for small and composite field relative dosimetry. With corrections, the RL measured Ω(f(clin),f(msr))(Q(clin),Q(msr)) were 0.656 ± 0.002, 0.815 ± 0.002 and 0.865 ± 0.003 for the 5, 7.5 and 10 mm collimators, respectively. This was in good agreement with RADPOS corrected field factors of 0.650 ± 0.010, 0.816 ± 0.024 and 0.867 ± 0.010 for the 5, 7.5 and 10 mm collimators, respectively. Both RL and RADPOS total scatter factors agreed within approximately two standard deviations of the GAFCHROMIC film values (average of EBT and EBT2) of 0.640 ± 0.006, 0.806 ± 0.007 and 0.859 ± 0.09. Corrected total scatter factors for all dosimetry systems agreed within one standard deviation for collimator sizes 10-60 mm. Our study suggests that the microMOSFET/RADPOS and optical fibre-coupled RL dosimetry system are well suited for total scatter factor measurements over the entire range of field sizes, provided that appropriate correction factors are applied for the collimator diameters smaller than 10 mm.

Photoluminescence (PL) and radioluminescence (RL) measurements were made on NaMgF3:Sm before, during and after exposure to high doses of ionising radiation. Magnetic measurements prior to irradiation showed that approximately 10% of the total Sm concentration was in the divalent state. The RL from Sm3+ was found to increase while the Sm2+ RL decreased with increasing x-ray dose before reaching steady-state values for high doses. This behaviour is opposite to that previously reported for Sm3+ and Sm2+ PL. We show that this apparent discrepancy can be accounted for by a RL model where there is a hole trap, an electron trap, and direct x-ray induced carrier recombination at Sm2+ and Sm3+. Furthermore, a good fit to the dose-dependence of all of the Sm RL emissions can be obtained by assuming that the relevant electron and hole traps are close to Sm3+. Our model accounts for F3-centre production during irradiation that affects some of the Sm3+ RL emissions via reabsorption of the RL by the F3-centres. Thus, the rate of F3-centre production can be conveniently monitored by the RL intensity ratio, I RL(567 nm)/I RL(650 nm). Additionally, the Sm2+ RL emissions may be expressed as [1.94 × I RL(721 nm)] - I RL(695 nm) to determine the real-time dose rate, independent of dose history.

The impact of the V-pits covering layer (VCL) position on the optoelectronic performance of InGaN-based green light-emitting diodes (LEDs) was investigated. It is found that earlier covering of V-pits will hinder the hole injection via the sidewall of V-pits, and then result in less quantum wells (QWs) participating in radioluminescence. The current-voltage characteristics show that the LEDs with earlier covering of V-pits have higher operating voltage at room temperature, and a more dramatic voltage rise with the reduction of temperature. Meanwhile, more manifested emission peaks for sidewall QWs and deeper QWs near to n-type layer was observed in the sample with earlier coveing of V-pits at cryogenic temperatures, for the reason that the holes being injected via V-pits sidewall have higher kinetic energy and could transport to deeper QWs.

The characteristics of radioluminescence of Nd3+ : Y3Al5O12 crystals and laser glasses under excitation by plutonium-239 (239Pu) α-particles, as well as by α-particles and spontaneous fission fragments of californium-252 (252Cf), are studied. The radioluminescence branching ratios βij for the transition from the 2F25/2 level to the 2S+1LJ levels in Nd3+ : Y3Al5O12 crystals are measured. Radioluminescence from the 2P3/2 level to low-lying levels is observed. The βij ratios for transitions from the high-lying 2F25/2, 4D3/2, and 2P3/2 levels are theoretically calculated. The lifetimes of metastable levels of Nd3+ excited by 252Cf fission fragments are measured. The efficiency of the conversion of energy of α-particles and fission fragments to the energy of optical radiation of Nd3+ : Y3Al5O12 crystals and laser glasses is determined.

A series of Pr-doped pyrosilicate crystals, Y2Si2O7 (YPS), Pr2Si2O7 (PrPS), Gd2Si2O7 (GPS), and Lu2Si2O7 (LPS), were synthesized by the floating zone (FZ) method to investigate whether the positive hysteresis phenomenon was observed or not. In all crystals, no impurity phases were observed in X-ray diffraction (XRD) analyses. In photoluminescence (PL) spectra, Pr3+ 5d–4f emission was observed from 270 to 400 nm in all the samples, and the PL decay times of them were around 10 ns. In radioluminescence (RL) spectra, they showed Pr3+ 5d–4f emission from 270 to 400 nm in all the samples, and the scintillation decay times were around 20 ns. When we irradiated with γ-rays from 137Cs, the scintillation light yields of YPS, GPS, and LPS were 8300, 1800, and 9700 ph/MeV, respectively. After these basic characterizations, we irradiated 0, 200, and 400 Gy γ-rays exposure by using 60Co. As a result, the positive hysteresis was not observed and YPS and LPS showed relatively high radiation resistivity.

Plastic scintillators containing Bi2O3 nanoparticles (NPs) were developed as detectors for X-ray synchrotron radiation. A hydrothermal method was used to synthesize the NPs that had average particle sizes of less than 10 nm. Higher NP concentration led to a higher detection efficiency at 67.4 keV. The light yield of the scintillator containing 5 wt % Bi2O3 NPs was comparable with or higher than that of the commercially available plastic scintillator, EJ 256. The time resolution of the developed scintillation detector equipped with each sample scintillator was approximately 0.6 ns. Dispersion of nanoparticles within plastic scintillators is generally applicable and has wide application as a method for preparation of plastic scintillators for detecting X-ray synchrotron radiation.

The effects of Mg co-doping on the scintillation properties of Ce:Lu2Gd1(Ga,Al)5O12 (LGGAG) single crystals with different Ga/Al ratios were investigated. Mg co-doped and non co-doped Ce:LGGAG single crystals were grown by the micro-pulling down (µ-PD) method and then cut, polished and annealed for each measurement. Absorption spectra, radioluminescence (RL) spectra, pulse height spectra, and scintillation decay were measured to reveal the effect of Mg co-doping. Ce4+ charge transfer (CT) absorption band peaking at ~260 nm was observed in Mg co-doped samples, which is in good agreement with previous reports for the Ce4+ CT absorption band in other garnet-based crystals. The scintillation decay time tended to be accelerated and the light yield tended to be decreased by Mg co-doping at higher Ga concentrations.

Luminescence and scintillation properties of Cs2HfBr6 and Cs2ZrBr6 crystals were investigated using photoluminescence (PL) and radioluminescence (RL) spectroscopies. In the PL spectra, emission bands were observed at 435 and 525 nm for Cs2HfBr6, and at 530 nm for Cs2ZrBr6. Corresponding emission bands were observed for RL spectra. The scintillation decay time constants of the Cs2HfBr6 and Cs2ZrBr6 crystals were smaller than those of the corresponding Cs2HfCl6 and Cs2ZrCl6 crystals. The scintillation light yields of Cs2HfBr6 and Cs2ZrBr6 were estimated to be 61,500 and 37,200 photons/MeV, respectively, which are much higher than those of Cs2HfCl6 and Cs2ZrCl6 crystals.

Nanosized, purified crystalline-phase cerium-doped lutetium aluminum garnet (LuAG:Ce) phosphors were prepared by the urea homogeneous precipitation method. The obtained phosphors showed much higher dispersivity, a fairly uniform size of about 30 nm, and higher luminescence intensity than those synthesized by a sol–gel combustion process. The radioluminescence spectrum of the phosphors consisted of two emission bands owing to the transitions from the lowest 5d excited state to the 4f ground state of Ce3+. The transmittance in the visible light region of the transparent ceramics fabricated at 1800 °C for 10 h under a higher vacuum of 1.5×10-3 Pa using the prepared powders reached 70% and the attenuation coefficient decreased to 0.116 mm-1, which caused much higher luminescence intensity. Compared with those reported previously, the optical properties of the LuAG:Ce transparent ceramics fabricated in the present work improved markedly.

The luminescence properties of Tb3+-doped fluoride crystals under excitation with ionizing irradiation have been studied in order to assess the feasibility of using them as crystal detectors for in vivo radiotherapy dosimetry. In particular, it has been found that the radioluminescence intensity from both CsY2F7 and CsGd2F7 doped with 15 at% Tb3+ is almost six times that from the commercial Al2O3 : C detector. The spectral composition of emitted light has been analysed in order to determine the function of the Tb3+ activator ion during ionizing radiation-induced luminescence. The thermally stimulated luminescence of the crystals has also been investigated.

Single crystals with the nominal composition of (Pr0.01,Lu0.99)3(Gax,Al1-x)5O12 (Pr:LuGAG) were grown by the micro-pulling-down (µ-PD) method with RF heating and their luminescence properties were characterized. Transparent and crack free crystals that were slightly yellowish green were obtained. Lattice constants and densities systematically increased with increasing of Ga concentration. The luminescence properties of Pr:LuGAG were characterized by photoluminescence spectra and decays, radioluminescence spectra and light yield measurements. 5d–4f luminescence was observed for the x≤0.6 samples. It was found that the 5d–4f emission of Pr3+ is quenched only slightly up to x≤0.4 whereas density systematically increased in the range of 0≤x≤1.0.

Key characteristics of a newly prepared tissue-equivalent, highly sensitive thermoluminescence dosimeter, Li2B4O7:Cu,Ag,P, are presented. The material was developed at the Institute of Nuclear Sciences, Belgrade, in the form of sintered pellets. A new preparation procedure has greatly increased the sensitivity of the basic copper activated lithium borate and the glow curve of Li2B4O7 : Cu,Ag,P consists of a well-defined main dosimetric peak situated at about 460–465 K with a sensitivity which is about four to five times higher than that of LiF : Mg,Ti (TLD-100). The exceptionally good response features of Li2B4O7 : Cu,Ag,P are attributed to the incorporation of Cu as a dopant. Both low and high temperature emission spectra are presented and the origins of the various emission bands are considered. Additional data are provided from electron paramagnetic resonance measurements.

The dosimetry of ionizing radiation fields plays an ever more important role in the safety and effective operation of nuclear systems. An optical dosimetry system composed of radiation-resistant optical fibres and radioluminescence materials has several advantages over a conventional electric dosimetry system. In particular, in a nuclear fusion system, the real-time diagnostics of intensity of radiation fields with a high time resolution is indispensable where electromagnetic noise is considerable and it is hard to find engineering solutions to satisfy the severe demands from plasma physics and engineering with a conventional electric dosimetry system. Erbium oxide (Er2O3) is found to emit radioluminescence in an infrared region where the radiation-induced degradation of the optical transmissivity of fused silica (SiO2) core optical fibre is marginal. Also, the intensity of the radioluminescence of erbium oxide in an infrared region is found not to decrease with increasing dose of ionizing irradiation. The optical dosimetry system with erbium oxide is applicable to the dosimetry of intense ionizing radiation fields.

The luminescence spectra and decay kinetics are measured within 80–300 K for the set of mixed YF3–GdF3 single-crystal fluoride hosts doped by the Ce3+ and Me2+ (Me = Mg, Ca, Sr, Ba) ions. For certain Ce and Me concentration ranges we observe creation of the Ce3+-distorted luminescence centre with the emission maximum around 380–390 nm. Energy migration through the Gd sublattice and a transfer to the Ce3+-distorted centre is evidenced and modelled using a simple Stern–Volmer approximation.

A possibility of applying a compact radiation dosimetry system to burning plasma machines, such as detecting high energy neutrons and gamma-rays with a wide dynamic range at elevated temperatures, has been studied, utilizing radiation resistant optical fibres and radioluminescence (radiation-induced luminescence) materials. Appropriate radioluminescence materials were found for dosimetry of each radiation field, namely, gamma-rays and neutrons. Especially, a high-energy neutron detection system utilizing optical fibres and radioluminescence materials will have several advantages, such as being compact and robust, and can be a strong candidate for diagnostics of fusion neutrons in a burning plasma machine.

Luminescence signals respond to phase transitions both of the host material and of impurities on the nanoparticle-size scale. During cathodoluminescence spectral measurements of many insulators, strong intensity changes (up to 100 times) have been recorded at ~170 K, which are here ascribed to the phase transitions of water that has diffused into the near-surface regions, or is trapped within the bulk material in nanoparticle quantities. The intensity step correlates with the ice transition between the cubic and hexagonal phases. In many materials there are also weaker features near 230 K which match the low-pressure ice-to-vapour transition. Some signals are apparent in radioluminescence data when the water is within the bulk material. The impurity phase changes can modify the emission spectra of the host. Examples are given for several insulators (Nd:YAG, zircon, MgO:Cr, PbWO4, strontium barium niobate) and a superconductor. The data have implications for quantitative luminescence analyses and underline the significant and influential presence of water contaminants. In many surface layers, such as surface optical waveguides or those of superconductors, the ice may significantly influence the behaviour of the host material.

In the last forty years, application of crystalline materials in ionizing radiation detectors has played a crucial role in the discovery of matter properties and promoted a continuous progress in the detecting technique. Further concepts of the detectors at HEP experiments will require an unique combination of the material features, particularly in case of collider experiments. Crucially important becomes a minimal level of radiation damage effects under the electromagnetic part of ionizing radiation and energetic hadrons as well: low deterioration of the optical transmission, low level of afterglow and low level of radioluminescence due to radio-nuclides being generated due to secondary nuclear reactions in the detector material itself. A systematic study of the radiation hardness of inorganic optical and scintillation materials have been performed. We concluded that both oxide and fluoride crystals which consist of atoms with atomic number less than 60 will be reasonably survivable in the irradiation environment of future experiments at colliders. In this study we focused on the study of cheap, capable for a mass production glass (BaO*2SiO2) and DSB: Ce glass ceramics obtained from this glass. We also made this glass more heavy by admixing gadolinium oxide into the matrix. Glass with Gd3+ admixture possesses two times larger light yield than pure (BaO*2SiO2) glass and glass ceramics. Both types of the materials were produced as fibre and blocks of larger volume.

The luminescence and scintillation properties of Tl- and Ce-doped Cs2HfCl6 crystals were investigated by photoluminescence and radioluminescence spectroscopy. In the photoluminescence spectra, emission bands of the activators were observed at 500 nm for Tl-doped Cs2HfCl6, and at 340 and 380 nm for Ce-doped Cs2HfCl6. The radioluminescence bands were observed at 405 and 430 nm for Tl- and Ce-doped Cs2HfCl6, respectively. Scintillation decay time constants for the Tl- and Ce-doped Cs2HfCl6 were smaller than those for the corresponding undoped crystals. Scintillation light yields for Tl- and Ce-doped Cs2HfCl6 were estimated to be 23,700 and 15,700 photons/MeV, respectively.

Nanoparticles are appealing materials because of their versatility in addition to the uniqueness of their properties enabling one to use them in different applications. Radiation detection with colloidal quantum dots (cQDs) is one of the domains where the nanoscience entered lately. The luminescent nanocrystals that are cQDs are of particular interest in scintillation dosimetry, where they could play the role of the fluorophore in a liquid scintillator. The study presented in this paper investigates the response of a cQD-based liquid scintillator to X-ray radiation in order to characterize the dose and cQDs concentration dependence of the radioluminescence (RL) signal. For a beam energy of 180 kVp, the latter was found to be linear as a function of dose, with a majority of the signal (~80%) coming from the cQDs and not the solvent, in this case hexane. Even with an ultra low concentration (μM), cQDs emit sufficient light to be detected. The RL intensity followed also a linear trend as a function of cQDs concentration, independently of the exposure time.

The low temperature TL spectra of undoped alkaline earth fluorides consistently show a continuous broad band emission around 280-300 nm. The origin of this emission is related to the relaxation of the self-trapped exciton (STE) in the form of an F-H pair. In doped samples, the broad emission is quenched in favour of emissions from the rare earth (RE) impurity sites. The degree of quenching varies between the REs. The spectral measurements showed that the temperature of the glow peaks below room temperature is to a large extent independent of the RE impurity, although some effects are related to the concentration. Additionally, the host material has minimal effect on the glow peak temperatures, Tmax. The scale of the observed differences in Tmax between the three hosts is similar to the differences in annealing temperatures of the Vk and H centres in these hosts. Above room temperature, the glow peaks are specific to the added RE ions and do not show common peaks.

The luminescence sensitivity of natural quartz is significantly enhanced if heated beyond the first and second crystal phase transitions, in the temperature range 500-1100 °C. This work employs a number of complementary spectroscopic methods to obtain a fuller understanding of the mechanisms of this sensitization process. Spectrally resolved radioluminescence is used to study the role played by hole trapping recombination sites. Linearly-modulated optically stimulated luminescence is used to probe a number of different optically active electron donor defects. Spectrally resolved thermoluminescence simultaneously monitors the processes of electron eviction from donor centres, and recombination at acceptor sites. Finally, high-frequency electron paramagnetic resonance is used to monitor changes in population and structure of defects present within the lattice, some of which partake (either directly or indirectly) in the emission processes of the samples. The work leads to the conclusion that luminescence is generally sensitized in quartz by the removal of oxygen vacancy E' centres (which act either as non-radiative recombination centres, or as luminescence centres emitting in the deep UV, beyond the range of our instrumentation). In some samples, further luminescence enhancement is accompanied by heat induced creation of donor defects. The spectral results show that, not only is there competition between the acceptors for recombining electrons, but also that the emission undergoes significant thermal quenching at elevated temperatures. Comparison of the radioluminescence and thermoluminescence measurements enables the quenching energies of two emission bands (360, 470 nm) to be obtained directly.

The infrared emission in radioluminescence of feldspar crystals determines the received irradiation dose. This recently discovered phenomenon can be used for dating the last light exposure of feldspar grains (e.g. sediments). From the physical point of view, there is particular relevance to the infrared optically stimulated luminescence, because both deal with the same light sensitive electron trap. Data from light stimulation experiments (ultraviolet to infrared) suggest that a localized transition is most likely to be responsible for the infrared optically stimulated luminescence and that this process is possible for only a relatively small proportion of trapped electrons. The infrared radioluminescence signal gives direct information about the trapped charge density of the electron trap. A new model, described in terms of a band scheme, has been successfully used to interpret the observed data.

In this paper we report measurements of x-ray- and vacuum UV-excited luminescence, luminescence excitation spectra and time profiles, low temperature thermoluminescence and isothermal decays as well as x-ray- and gamma-excited scintillation time profiles and scintillation light yields at various temperatures on BaF2:Ce and, for reference, on undoped BaF2, two well known scintillator materials. For the first time we find that all these results can be consistently interpreted in the frame of a model that includes Ce-related recombination centres and several charge `traps'. The charge trapping at most of these `traps' has its origin in self-trapping and trapping of holes at regular (Vk) and interstitial (H) fluorine sites. We have identified and characterized two different modes of thermally activated Vk release that precede radiative recombination at Ce sites. These two modes are responsible for a 7 ns rise time and a slower 114 ns components in the scintillation time profile at room temperature (297 K) that produce about 67% of the scintillation light detected within a 0.5 µs time window. The remaining 33% is due to a prompt component decaying with the Ce3+ radiative lifetime of about 30 ns that originates from the direct recombination of charge carriers at Ce3+ ions. We also estimate that scintillation light loss due to even slower components, at 23.1 µs (H centres), 1.1 ms and 7 ms (VkA and VkA' centres), exceeds at least threefold the amount of light emitted in the 0.5 µs time window. Therefore in addition to their well known role as defect centres actively participating in the formation of stable radiation damage centres these species are also involved in the radiative recombination process itself. The perspectives of improvements in performance of the BaF2:Ce scintillator are also briefly discussed.

Thermoluminescence (TL) and radio-thermoluminescence spectral analysis techniques have been applied to doped calcium sulphate samples designed for radiation measurements at elevated temperatures. CaSO4 :Dy, when co-doped with Ag, provides a TL dosimetric peak near 350 °C which is useful for radiation measurements at high temperatures. Dopants of Ce, Mn and Dy variously move the peak temperature from 400 °C to 200 °C. Each dopant ion gives a characteristic emission spectra, which for CaSO4 :Ce, Mn samples indicate that there is a systematic temperature difference of ~7 °C between the glow peaks from the Ce and Mn sites. The CaSO4 :Dy samples show a discontinuity in the emission wavelength from the Dy ions near T = 200 °C and a decrease in the radioluminescence fluorescence in the same temperature region. In each case it is proposed that the dopants form part of large, complex defects, instead of isolated trapping and recombination centres. The data offer further evidence for a localized phase transition of the defect complex at 200 °C. Low-temperature data, from 20 K, show similar differences in the peak temperature from the various dopants and additionally indicate reproducible discontinuities in the wavelength positions and intensities, for all samples, at T = 230 K. This again suggests structural phase adjustments of the defect sites.

Radiation-induced light emission (RLE) spectrum of pure silica core optical fiber is measured under intense γ-irradiation of a source 60Co. It is shown that the spectrum is subjected to deformation due to high degree of reabsorption caused by γ-induced color centers. The method of measurement and calculation of true spectrum of emission in optical fibers is created. The formula of true intensity I(λ) obtained within the method takes into account the optical losses coefficient from registered RLE intensity value and allows to plot the true spectrum. The true RLE spectra of pure-silica core fiber irradiated at different integrated doses are measured and plotted using this method. It is shown that the method can be used to obtain the true RLE spectra of optical fibers under various types of irradiation.

We developed a scintillator based on a Rb2HfCl6 crystal as a ternary halide crystal with intrinsic luminescence. In the photoluminescence spectra, two emission bands are observed at 383 and 434 nm. The 434 nm emission band for Rb2HfCl6 may be attributed to [HfCl6]2− complex ion or [ZrCl6]2− impurity, since the Rb2HfCl6 contained Zr as impurity at 0.62 mol %. The radioluminescence band is observed at 420 nm and can be attributed to the same origin as the photoluminescence band at 434 nm. The scintillation decay-time constants were 0.84 and 5.4 µs. The light yield was estimated to be 24,100 photons/MeV.

International audience; Cerium-doped silica glass has been prepared for ionizing radiation dosimetry applications, using the sol–gel route and densification under different atmospheres. In comparison with the glass densified under air atmosphere, the one obtained after sintering the xerogel under helium gas presents improved optical properties, with an enhancement of the photoluminescence quantum yield up to 33%, which is attributed to a higher Ce3+ ions concentration. Such a glassy rod has been jacketed in a quartz tube and then drawn at high temperature to a cane, which has been used as active material in a fibered remote x-ray radiation dosimeter. The sample exhibited a reversible linear radioluminescence intensity response versus the dose rate up to 30 Gy s−1. These results confirm the potentialities of this material for in vivo or high rate dose remote dosimetry measurements.

The photoluminescence and scintillation properties of Cs2HfCl6 and Cs2ZrCl6 crystals were investigated. Two emission bands in the photoluminescence spectra were observed at 375 and 435 nm for the Cs2HfCl6 crystal and at 440 and 479 nm for the Cs2ZrCl6 crystal. Similar spectra were observed for radioluminescence. The decay time constants were found to be about 2.2 and 8.4 µs for Cs2HfCl6 and 1.5 and 7.5 µs for Cs2ZrCl6. The scintillation light yields were estimated to be 27,500 and 25,100 photons/MeV for Cs2HfCl6 and Cs2ZrCl6, respectively.

We have investigated X-ray induced radioluminescence (XL) properties of Sm-doped fluorochlorozirconate (FCZ) glasses and glass-ceramics. The FCZ glass is a modified ZBLAN glass which shows a very high optical transmission over a wide spectral range. The glass matrix includes Sm3+-doped nanocrystals of BaCl2 after heat-treatment at temperatures above 250 °C. The glass-ceramic emits red light under UV and X-ray exposure. Since conventional Si-based photodetectors, e.g., CCDs, have the highest quantum efficiency to red light in general, the Sm-doped FCZ glass-ceramic plate can be a good candidate as a scintillator material for indirect radiation detection. Moreover, a very broad emission is present in the glass-ceramic around 300–500 nm, which is attributed to a self-trapped exciton (STE) emissions. The temperature dependence of X-ray induced luminescence and photoluminescence are very similar. The XL light yield is linearly proportional to the X-ray exposure rate for rates higher than 20 mR/s. For low exposure rates, emissions by Sm2+ are more sensitive than others, leading to a nonlinear response.

In the present study, nondoped CdS crystal with a size of 5 × 5 × 0.5 mm3 was investigated on the optical and scintillation properties. The optical transmittance was 70% at wavelength longer than 500 nm, and the absorption edge was around 490 nm. The photoluminescence emission peak appeared around 490 nm under 340 nm excitation with 6.6 ns fast decay time. In X-ray induced radioluminescence spectrum over the temperature range of 7–300 K, it showed four emission bands around 490, 500–540 with several peaks, 600, and 750 nm. Temperature dependences of each emission band were different. The scintillation decay time was reproduced by two exponential decay components of 8 and 67 ns, and that for X-ray induced afterglow was approximately 0.1% at 20 ms after switching of the X-ray irradiation.

Thermoluminescence (TL) and radioluminescence (RL) spectra have been recorded from a set of calcium fluoride samples doped with Neodymium. The dopant levels used were 1.0, 0.1 and 0.0130 and 400 degrees C, with spectra being taken both prior to heat treatments, and after heating to 500 degrees C for one hour and cooling at different rates. For the RL, each sample gave a UV/blue emission band near 300 nm which decreased with increasing Nd concentration. During thermoluminescence the Nd is the main recombination centre and shows characteristic line emission. However the spectra vary with concentration and thermal treatments. Models for the changes involve Nd defect clustering with non-radiative decay paths. At high temperature the TL spectra include other emission bands attributed to relaxed exciton decay.

Ca 100, 200, 500, 1000 and 3000 at. ppm co-doped (Ce0.01,La0.3Gd0.69)2Si2O7 single crystals were grown by the μ-PD method. Luminescence and scintillation properties such as radioluminescence spectra, light yield and decay time were evaluated. Expected Ce3+ 4f5d emission have been observed in 350-430nm peaking at 360nm. Emission intensity took maximum at the Ca 100at.ppm co-doped sample and decreased by increasing the Ca concentration. The Ca 100at.ppm co-doped sample showed the highest light yield of around 20,000 photons/MeV. Scintillation decay time was accelerated with increasing Ca concentration. Scintillation decay time of the Ca 0, 100, 200, 1000 and 3000 at. ppm co-doped samples were 66.5ns(21%) 468ns(79%) and 44.0ns(22%) 430ns(78%), respectively.

This paper reports on a study of the luminescence characteristics of KBe2BO3F2 (KBBF) and RbBe2BO3F2(RBBF) crystals in UV/visible spectral range. The KBBF crystals are very popular for their nonlinear optical properties, however they have a potential to be used as scintillators for neutron detection. To determine the effectiveness of KBBF scintillation we combine the results from measurements of optical absorption; radioluminescence; light yield; photoluminescence and decay kinetics in the temperature range 8-330 K. Temperature dependence of luminescence in KBBF crystals is discussed.

In the recent publication by Hospodková et al, the authors investigate III-N quantum well structures as potential fast scintillators (Hospodková et al 2014 Nanotechnology 25 455501). The InGaN/GaN quantum well structures are grown using metal organic vapour phase epitaxy on a sapphire substrate and the fast carrier decay times are characterized by time resolved photo and radioluminescence.