Luminescent response from BeO exposed to alpha,beta and X radiations

This work presents the TL and OSL response of beryllium oxide detectors exposed to alpha, beta and X radiation beams. The samples were characterized, and they presented good reproducibility, good linearity interval, low energy dependence, and an acceptable fading. The luminescent response was better for the OSL technique.     

Assessing the impact of IR stimulation at increasing temperatures to the OSL signal of contaminated quartz

The purpose of the present study is to identify the effect of the increasing temperature IR stimulation to the component-resolved OSL luminescence signal of mixed quartz-feldspars material. Post IR OSL signals measured at 110 °C were analysed via only general order kinetic terms, while IR signals obtained at increasing temperatures were de-convolved using the sum of general order kinetics plus a tunnelling component. By increasing stimulation temperature, it was demonstrated that IRSL at temperatures above 50 °C does not only stimulate feldspar but also stimulates both fast and medium quartz OSL components. In the temperature range between 175 and 250 °C, the IRSL initial intensity is dominated by the fast OSL component. Estimated equivalent doses using either Post-IR₁₇₅.OSL₁₁₀ as well as IRSL₁₇₅ (with the indices indicating the measurement temperature) are in good agreement between each other, due to both stimulating quartz. Finally, the physical meaningfulness of the fitting parameters for the tunnelling component is also discussed.     

OSL and TL in TLD-100 following alpha and beta irradiation: Application to mixed-field radiation dosimetry

The optically stimulated luminescence (OSL) of LiF:Mg,Ti (TLD-100) following irradiation by beta and alpha particles was investigated by measurement of the excitation and emission spectra of OSL and comparison with thermoluminescence (TL) characteristics. The OSL excitation spectra of all the samples following both beta and alpha irradiation are very similar.Identical emission bands with very similar relative intensities following both beta irradiation and alpha particle irradiation have been recorded in the OSL induced in nominally pure LiF mono and TLD-100 polycrystals. The identical excitation and emission bands in the doped and pure crystals are strong evidence indicating that the observed OSL is due to an intrinsic trapping structure. The OSL has indeed been previously attributed to F₂ centers and F₃⁺ centers.The preferential excitation of OSL compared to TL following high ionisation density (HID) alpha irradiation is naturally explained via the identification of OSL with the “two-hit” F₂ or F₃⁺ center, whereas the major component of composite TL glow peak 5 is believed to arise from a “one-hit” complex defect. This discovery allows near-total discrimination between HID radiation and low ionisation density (LID) radiation and may have significant potential in mixed-field radiation dosimetry.     

Cross-calibration between beta and gamma sources using quartz OSL: Consequences of the use of the SAR protocol in optical dating

The radiation dose delivered by the ⁹⁰Sr beta source of a TL-OSL reader and the one delivered by a ¹³⁷Cs gamma source were compared using OSL dating techniques and tools. Three sets of quartz of different origins (rock, sediment and loess) were studied and measured by the SAR protocol (Single aliquot regenerative dose protocol) after irradiations carried out either by the ⁹⁰Sr source or by a ¹³⁷Cs source. Measurements show that the values obtained by the SAR protocol must be corrected in order to provide an acceptable cross-calibration of the beta and gamma source. Once applied, measurement sets become self-consistent and compatible with expected values. The consequences of the above mentioned observations on the methodology of OSL dating are discussed and suggest that a mixed protocol be used including both the SAR protocol and an added dose techniques close to the SARA protocol (Single aliquot regenerative and added dose protocol).     

Effects of radiations on the characteristics of alpha and fission tracks in CR-39 detectors

Abstract

The effects of neutron, gamma and alpha radiations on the alpha and fission fragment tracks registration and revelation properties of CR-39 detectors (CR-39 and CR-39(DOP) were studied. It was found that the ratio of the bulk etch rate of irradiated to unirradiated (V_G(irr.)/V_G(unirr.) detectors is linearly dependent on dose. An exponential decrease in fission track densities with increase in neutron fluence was observed. The ratio of V_G(irr.)/V_G(unirr.) was found to be high in CR-39 than that in CR-39(DOP) exposed to the same reactor neutron fluence. The decrease in fission track densities with increase in neutron fluence was observed to be faster in CR-39 than in CR-39(DOP). This indicates that doping with dioctyl phthalate improves the radiation resistance of CR-39 detectors. It was observed that in detectors exposed to an alpha flux of the order of 9.36 × 10⁶ / cm², the fission track density was reduced by 11% and thereafter it remained constant. The results also indicate that thermal neutron fluence up to 7.01 ×10¹¹ neutrons/cm² does not affect the alpha and fission track densities. I.R. spectra were also studied to find out the nature of chemical changes produced by these radiations on CR-39.     

Time resolved spectra of optical and electrical transient response induced by nanosecond laser pulses in amorphous AgInSbTe films

The phase transition dynamics of amorphous Ag₈In₁₄Sb₅₅Te₂₃ (AIST) thin films induced by single nanosecond laser pulses were studied by transient optical reflectivity and electrical resistance measurements with nanosecond resolution. Phase transition driven by nanosecond laser pulses can be achieved in a proper fluence range on AIST thin films. The results show that phase transition dynamics driven by nanosecond laser pulses was a multi-stage optical evolution process involving melt, solidification, recalescence, and recrystallion. However, it was found that the real-time responses of optical and electrical signals were quite different under the same irradiated condition. The recalescence process reflected by the second rising of optical reflectivity will not result in obvious changes in electrical resistance. The dependence of saturated time determined by optical and electrical evolution curve on laser pulse fluence was compared and analyzed. A two-dimensional percolation model was employed to explain the difference between electrical and optical transient responses.     

Radiobiological response of human hepatoma and normal liver cells exposed to carbon ions generated by Heavy Ion Research Facility in Lanzhou

Human hepatoma and normal liver cells were irradiated with ¹²C⁶⁺ ion beams (LET = 96.05 keV/μm) and γ-rays at Heavy Ion Research Facility in Lanzhou (HIRFL). The chromatid breaks and break types were detected using the premature chromosome condensation technique. Our experimental results showed that chromatid breaks seem to have a good relation with ¹²C⁶⁺ absorbed dose and ¹²C⁶⁺ are more effective to induce chromatid breaks as compared to the γ-rays. For ¹²C⁶⁺ ion irradiation the major break was isochromatid break, while chromatid breaks were dominant for γ-ray irradiation. We also observed that the Relative Biology Effectiveness (RBE) of ¹²C⁶⁺ ion is about 2.5 times higher than that of γ-rays.     

An alternative definition of the electron propagator in the superoperator form and its relation to linear response theory in a coupled-cluster framework

In this paper it is shown that (i) there exists an alternative definition of the superoperator resolvent for calculation of difference energy satisfying linked cluster theorem for a coupled-cluster choice of the ground-state function which may even be approximate; (ii) the pole-structure of this propagator-like function in superoperator form is shown to contain information similar to that contained in the conventional propagator. (iii) It is demonstrated that suitable “Killer conditions” and completeness of the “operator manifold”—essential for understanding the pole-structure of the propagator—can be established both for an exact and an approximate ground state function in a coupled-cluster form. (iv) It is also demonstrated that difference energies calculated with these propagator-like functions are identical to those obtained from a linear response theory in a coupled-cluster form put forward recently by Mukherjeeet al and Monkhorst.     

Nanodosimetric kinetic model incorporating localized and delocalized recombination: Application to the prediction of the electron dose response of the peak 5a/5 ratio in the glow curve of LiF:Mg,Ti (TLD-100)

A kinetic model combining both localized and delocalized recombination is described which is based on different filling rates as a function of irradiation electron energy of a spatially correlated trapping center/luminescent center (TC/LC) complex. Following irradiation and thermal de-trapping the locally trapped electron-hole configuration is assumed to give rise to peak 5a and the e-only configuration to peak 5 in the glow curve of LiF:Mg,Ti (TLD-100). The model is capable of simulating the linear/supralinear dose response of composite peak 5, the dependence of the supralinearity on photon energy and the ratio of the intensities of peak 5a to peak 5 as a function of dose. However, this is achieved only by invoking the presence of band-tail states which allow thermally induced hopping leading to semi-localized recombination in the recombination mechanism of the e-only configuration.