Radiation-induced Luminescence Research Articles

Radiation-Induced Luminescence from Quartz Grains to Evaluate Naturally Accumulated Radiation Doses

Radiation-Induced Luminescence from Quartz Grains to Evaluate Naturally Accumulated Radiation Doses

Effect of acoustic strain on the radiation-induced luminescence of pyrolithic boron nitride

A study is reported on the effect of ultrasound vibrations of an approximate frequency of 100 kHz on the radiation-induced luminescence generated in pyrolytic boron nitride by proton irradiation (8 MeV energy, 1.6×1012 p/cm2 s flux). The influence of ultrasound vibrations manifests itself at large strain amplitudes (∼10−4), where nonlinear, amplitude-dependent absorption of ultrasound is observed to occur. The data obtained are assigned to a radiation-induced change in the recrystallization kinetics, where low-angle boundaries disappear (radiation annealing).

Radiation-induced electrical and optical processes in materials based on Al2O3

The irradiation of dielectrics induces electric charging of microscopic regions in the bulk, which is associated with concentration inhomogeneities in the system of traps and the differences in characteristic diffusion lengths of free electrons and holes that are produced in ion tracks and collision cascades. Experimental data on radiation-induced luminescence (RIL) give evidence of the existence of three states of oxygen vacancies in Al2O3: an optically inactive (electrically neutral) vacancy, its excited state (known as F + center), and a negatively charged vacancy (F center). The formation of negatively charged regions under irradiation increases the intensity of the 415-nm band of F centers of RIL of Al2O3 single crystals. In Al2O3:Cr3+ ceramics, a radiation-induced negative charging of grain boundaries with respect to the bulk of grains takes place, which manifests itself as an increase in the intensity of the 690-nm band of RIL of Cr3+ ions, whereas the intensity of this band in Al2O3:Cr3+ single crystals remains unchanged. Using data on RIL, the local-charge density in grains of Al2O3:Cr3+ ceramics and the field produced by this charge are estimated.

Thermoluminescence Analysis for Detection of Irradiated Food—Effects of Dose Rate on the Glow Curves of Quartz

Thermoluminescence (TL) measurement is a means of discriminating between irradiated and non-irradiated food carrying small amounts of sand or dust. Silicate minerals are isolated and purified, and their radiation-induced luminescence is measured.When ‘pure quartz’ was studied by TL analysis, glow curves of different shape, position and intensity were obtained from various sources of radiation having different dose rates and beam energies. To study the effect of dose rate, ‘pure quartz’ was exposed to60Co-γ-rays from two sources at various dose rates (∼ 0.060 Gy/s or ∼ 0.0025 Gy/s). In addition, quartz powder and quartz sand of less purity were examined.Both total dose and dose rate influenced the TL behaviour. Only very slight differences among the TL glow curves of ‘pure quartz’ have been found at various dose rates of a dose of 0.2 kGy. At 1.0 kGy, however, greater differences in shape, position and intensity appeared. At 5.0 kGy, the differences in shape and position, but not in intensity, decreased.Glow curves of quartz powder, too, showed—though less pronounced—differences in shape and intensity at various dose rates. Quartz sand failed to produce such differences in its glow curves at different dose rates.

Thermoluminescence Analysis for Detection of Irradiated Food—Luminescence Characteristics of Minerals for Different Types of Radiation and Radiation Doses

Thermoluminescence analysis is used to detect radiation processing of foods which are contaminated with sand or dust. Silicate minerals are isolated, their radiation-induced luminescence is measured and compared to the thermoluminescence from a second measurement after exposure to a defined radiation dose (normalization). In the present study, the mineral mixture ‘sand’ and its main components feldspar and quartz were investigated for their thermoluminescence behaviour using different types of radiation, in order to determine adequate radiation sources for the purpose of normalization. The material was irradiated with types of ionizing radiation commonly used for commercial food irradiation, i.e. accelerated electrons with beam energies of 5 MeV as well as 10 MeV, and60Co- γ -rays. After thermoluminescence measurements, samples were re-irradiated using either accelerated electrons with beam energies of 2 MeV, 5 MeV or 10 MeV, or60Co- γ -rays,90Sr- β -rays or ultraviolet rays (200–280 nm). Evaluation of the first and corresponding second glow curve revealed that their shapes depend on the type of minerals in the mixture. The second radiation treatment (normalization) is satisfactory when accelerated electrons (2, 5 and 10 MeV) as well as60Co-γ -rays and90Sr- β -rays are employed. Normalization with ultraviolet rays, however, has only a limited range of use.

A new type of plastic scintillators with excellent radiation resistance

Radiation processes in plastic scintillators (PSs) are studied to establish that, first, macroradicals are the main quenchers of radiation-induced luminescence in the PSs, and, second, molecular oxygen initiates the decay of macroradicals. Based on these principles, PSs of a new type, whose radiation resistance is by an order of magnitude higher than that of standard polystyrene scintillators, were developed and synthesized. The special nanoporous morphology of the new PSs is a system of open pores and channels, which provide efficient penetration of molecular oxygen into the polymer bulk to produce the antirad effect.

Luminescence kinetics in proton-irradiated quartz glasses

It is experimentally demonstrated that the intensity of the radiation-induced luminescence (RIL) of KU-1 and KI quartz glasses at 450 nm increases more than ten times upon the proton irradiation (proton energy, 8 MeV; dose rate, 5×103 Gy/s; dose, up to 1.2×107 Gy) to a dose of 106 Gy. At a dose exceeding 106 Gy, the spectral efficiency of the ionizing radiation energy conversion reached ∼10−6 nm−1 in the maximum of the RIL band at 450 nm for all types of glasses. After preliminary low-rate γ-irradiation (below 0.5 Gy/s), the RIL intensity in the beginning of the proton irradiation and its variation with the proton dose depend on the concentration of impurities in the quartz glass. The RIL intensity buildup depends on the formation of positively and negatively charged microscopic regions in glasses.

Radiation-induced absorption and luminescence in specially hardened large-core silica optical fibers

Radiation-induced absorption and luminescence are measured in the visible spectral region in H/sub 2/-loaded and as-drawn fibers with KU and KS-4V silicas in the core in the process of /spl gamma/-irradiation (/sup 60/Co-source). The induced absorption in H/sub 2/-loaded fibers is shown to be much lower than in as-drawn fibers, at least up to 1.2 MGy. A 'blue' band prevails in the luminescence spectra of all the fibers. Its intensity is greater in a KS-4V fiber than in a KU fiber. It is also somewhat greater in H/sub 2/-loaded fibers than in unloaded ones, The luminescence lifetime in a KU fiber has been measured under excitation with a pulsed reactor to be 100 /spl mu/s at /spl lambda/=488 nm and 60 /spl mu/s at /spl lambda/=633 nm. It is concluded that the 'blue' radioluminescence cannot be attributed either to relaxation of the oxygen-deficient center or to Cerenkov emission. A fabrication technology of radiation-hardened H/sub 2/-containing fibers with a hermetic aluminum coating is reported. Such fibers appear to be the best candidates for various applications in radiation environments.

Characterization of Fundamental Luminescence Properties of the Mars Soil Simulant JSC Mars-1 and Their Relevance to Absolute Dating of Martian Eolian Sediments

This report explores the potential for luminescence dating techniques to provide absolute age determinations of eolian sediments on the surface of Mars, including those incorporated in the martian polar ice caps. Fundamental thermally and optically stimulated luminescence properties of bulk samples of JSC Mars-1 soil simulant are reported and their relevance to the development of dating procedures is discussed. The radiation-induced luminescence signals (both thermoluminescence, TL, and optically stimulated luminescence, OSL) from JSC Mars-1 are found to have a wide dynamic dose–response range, with the luminescence increasing linearly to the highest doses used (936 Gy), following irradiation with 90Sr/ 90Y beta particles. The signals are also susceptible to solar resetting, with the OSL signals decreasing to <10% of their original levels within the first 20 min of exposure to sunlight. The TL signal also decays rapidly, being reduced to ∼15% within the first 20 min, but reaches a stable, nonzero level at long bleaching times. Neither the TL nor the OSL signals exhibit fading (i.e., loss of signal after irradiation before TL or OSL readout), nor do they exhibit significant sensitivity changes upon repeated irradiation and readout. These three properties (wide dynamic range, solar bleaching, and signal stability) form a stable base for future investigation of the material for luminescence dating and form a preliminary step toward development of dating protocols for terrestrial analogs of Mars surface materials. We conclude that luminescence dating, properly developed, holds the potential to be a valuable tool for absolute dating of martian eolian sediments

Radiation-induced electrical and optical processes in materials based on Al 2O 3

Concentration inhomogeneities in the trap system have been shown to be responsible for radiation-induced electric charging of regions in the bulk of dielectrics under irradiation. Formation of electrically charged regions is caused by difference in hopping mobility of charge carriers over traps and does not violate general electric neutrality of the system. Formation of negatively charged regions during irradiation results in intensity increase for F-centres band (415 nm) in radiation-induced luminescence (RIL) spectra of single crystal Al 2O 3. In ceramic Al 2O 3:Cr 3+, the radiation-induced negative charging of grain boundaries with respect to grain bulk takes place which is revealed in the intensity increase of Cr 3+ ion RIL band (690 nm), in spite of a constant intensity of this band in single crystal Al 2O 3:Cr 3+ under similar conditions. The idea of the radiation-induced electric charging due to concentration inhomogeneities in the trap system allows one, using the RIL method, estimating local charge density in grains of ceramic Al 2O 3:Cr 3+ and associated electric field. Under 8 MeV proton irradiation (dose rate up to 5 × 10 3 Gy/s), excessive positive charge in grains of ceramic Al 2O 3:Cr 3+ exceeds 10 4 Q/m 3, and associated electric field exceeds 10 6 V/m.

Radiation-induced luminescence images and TL-property changes with thermal annealing treatment on Japanese twin quartz

Two-dimensional patterns of radiation-induced phenomena, including thermoluminescence (TL), after-glow (AG) and colour centre (CC) images, showed significantly different behaviour between the core and outer parts of a Japanese twin quartz slice. Intense smoky colouration and blue luminescence appeared in the core, giving a good inverse correlation with the distribution of aluminium impurity. In addition, there was a characteristic red AG in the outer parts of the crystal. The response to radiation of the blue TL (BTL) from the outer part of the as-received quartz slice segments revealed poor BTL sensitivity and a tendency to saturation at low doses. The outer part was especially characterized by high contents of both aluminium and OH impurity, although the annealing treatments greatly eliminated the OH concentrations as water vapour. The annealing treatment (50 hr at 1000°C) of the slice segments brought on a remarkable changes to the TL-property; the core part was converted from BTL having a broad peak around 480 nm at 230°C into a new BTL peak around 100°C, and broad spectrum ranging from BTL to red TL (RTL) at 300°C. The outer part was characterized by a change into a new single 100°C BTL peak from some weak peaks of the as-received segment. On the basis of these radiation-induced phenomena, a new formation mechanism for twin quartz is proposed. We propose that the core part was formed first and was followed by the formation of the out part from hydrothermal solution and with a higher aluminium concentration.

Influence of restraint stress on IL-1 β messenger RNA expression in the rat brain induced by peripheral lipopolysccharide injection

Single-mode optical fibres (SMFs) are required for ITER in-vessel applications as transport fibres to deliver the signal at wavelength λ = 1.55 µm from/to optical fibre sensors. The paper describes the first comparison study of radiation resistance of six pure-silica-core SMFs of different manufacturers performed in the process of fission-reactor irradiation in the conditions corresponding to the whole ITER lifetime (fast-neutron fluence, flux, γ-dose and dose rate of up to 1.8·1020n/cm2, 1.08·1014n/(cm2·s), 2.32 GGy and 1.39 kGy/s, respectively, temperature of 170–190 °C and vacuum pumping). Polyimide- and acrylate-coated SMFs failed mechanically during the irradiation; therefore, only metal-coated fibres can be considered for the in-vessel applications. Induced optical loss in all three metal-coated SMFs (copper- and aluminum-coated ones) at the fast-neutron fluence of 1·1020n/cm2 was found to lie in the range ~1.5–4 dB/m, the lower value of this range allowing the employment of at least 10-m-long transport fibre lengths in the in-vessel applications, assuming the dynamic range of 30 dB. The temperature-dependent microbending optical loss in metal-coated SMFs is discussed, of which the contribution to the total induced loss may be comparable in value to the radiation-induced absorption of light. Neither radiation-induced luminescence, nor Cerenkov emission was detected in the SMFs in the near-infrared range.

Luminescence studies on electron and structural states in dielectrics under irradiation

Spectra of radiation-induced luminescence (RIL) and photoluminescence (PL) of Al 2O 3 and BeAl 2O 4:Cr 3− single crystals and BN ceramics have been obtained. In Al 2O 3 under 8 MeV proton irradiation, the recharging of defects causing RIL has been shown to occur in the track vicinity of 10 −6 cm size. After neutron irradiation, an essentially non-equilibrium distribution of Cr 3+ impurities over structurally distinguishable sites in the crystal lattice of BeAl 2O 4 was registered by PL spectroscopy. An effective temperature characterising this distribution under neutron irradiation exceeds the melting point of the material. The RIL and PL of BN were caused by colour centres on grain boundaries. Radiation-induced structural transformations in BN ceramics under neutron and 26.7 MeV Ne ion irradiation principally occur on the grain boundaries but not in the bulk of grains.

Luminescence of Mn 2+ doped ZnS nanocrystallites

Optical properties of Mn 2+-doped ZnS colloids are reported. The band to band excitation energy transfer to Mn 2+ is more efficient compared to Mn 2+ direct excitation, which is different from the case for bulk ZnS: Mn. Aging effects and the radiation-induced luminescence enhancement (RILE) effect are reported and an explanation for this behavior is presented.

The Role of Core Levels in Scintillation Processes

ABSTRACTThe Auger decay of a core hole results in appearance of several strongly correlated excitations. This excited region strongly polarizes the lattice and thus the defect creation is possible. In all cases the core hole causes the strong local perturbation of electronic and lattice subsystems. The creation of such excited region with mutual relaxation of correlated electrons and holes can result in the increase of the efficiency of energy transfer to activators, acceleration of the luminescence kinetics, and the appearance of radiation-induced luminescence centers.

Radiation-induced luminescence from minerals

Radiation-induced luminescence from minerals

Radiation-Induced Energy Migration within Solid DNA: The Role of Misonidazole as an Electron Trap

The "in-pulse" luminescence emission from solid DNA produced upon irradiation with electron pulses of energy below 260 keV has been investigated in vacuo at 293 K to gain an insight into the existence of radiation-induced charge/energy migration within DNA. The DNA samples contained misonidazole in the range 3 to 330 base pairs per misonidazole molecule. Under these conditions greater than 90% of the total energy is deposited in the DNA. The in-pulse radiation-induced luminescence spectrum of DNA was found to be critically dependent upon the misonidazole content of DNA. The luminescence intensity from the mixtures decreases with increasing content of misonidazole, and at the highest concentration, the intensity at 550 nm is reduced to 50% of that from DNA only. In the presence of 1 atm of oxygen, the observed emission intensity from DNA in the wavelength region 350-575 was reduced by 35-40% compared to that from DNA in vacuo. It is concluded that electron migration can occur in solid mixtures of DNA over a distance of up to about 100 base pairs.

Radiation from oscillating dipoles immersed in a solid, and radiation-induced luminescence.

We have solved Maxwell's equations for a source, consisting of an oscillating dipole, located in a plane-bounded dielectric half space. Formulas are given for the radiation yield from this source in the region outside the dielectric. The medium is characterized by a local, complex dielectric function \ensuremath{\epsilon}(\ensuremath{\omega})=${\ensuremath{\epsilon}}_{1}$(\ensuremath{\omega})+i${\ensuremath{\epsilon}}_{2}$(\ensuremath{\omega}). The application of these formulas to the analysis of experimental data on luminescence from solids is discussed, and calculations are presented for aluminum, carbon, silver, copper, and gold.

Radiation-induced luminescence from “dry” and hydrated DNA and related macromolecules

The radiation-induced luminescence from three types of fibrous DNA and a series of polydeoxynucleotides was measured under vacuum or in the presence of oxygen at 77 and 293 K. The “in pulse” emission spectra, generated by electrons with energies <260 keV, have been investigated in order to obtain an understanding of the effects of direct energy deposition within DNA. From a comparison of the observed emission spectra from “dry” DNA samples with different A + T/G + C ratios with those for the polydeoxynucleotides, it is inferred that the A + T/G + C ratio of DNA is an important factor in determining the wavelength dependence of the emission. The “in-pulse” emission characteristics of DNA and the polydeoxynucleotides were found to be independent of both temperature and the presence of oxygen. Investigations were extended to study the effect of hydration of DNA upon the resulting radiation induced emission spectra. It is apparent that with DNA thin films (15–20 μm) containing >50% water by wt (1.2:1 w/w, H 2O|DNA), the “in-pulse” luminescence spectrum is similar to that of “dry” DNA. These findings are discussed in terms of energy or charge migration induced in DNA upon irradiation and the possible effects of conformational changes, caused by hydration, on charge migration.

Radiation-induced luminescence of ceramics

Radiation-induced luminescence of ceramics