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  • A comparison on three neutron-gamma discrimination methods used with NE213, UGLLT and UGAB scintillators
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2020-01-17
    Y. Lotfi; S.A. Moussavi-Zarandi; N. Ghal-Eh; E. Bayat

    Liquid organic scintillators are widely used in radiation measurements. NE213 (or its equivalent, BC-501A) in neutron-gamma discrimination (NGD) and two new scintillators, UGLLT and UGAB, in alpha-beta discrimination are two common examples. In this paper, the NGD capabilities of these three scintillators were studied and their figure-of-merits (FoMs) were measured for comparison. The three different NGD methods used in this study were zero-cross method (ZCM), charge integration method (CIM) and filtered charge integration method (FCIM), where ZCM was analog and the two other methods were digital. A 1.1 μCi point 22Na gamma ray source and 100 mCi cylindrical 241Am–Be neutron source (3.5 cm diameter by 5 cm length) were used for the energy calibration and the NGD, respectively. The FoM values for NE213, UGLLT and UGAB at 100 keVee discrimination bias (i.e., the preset threshold voltage, generally expressed in keVee unit, upon which the generated pulse-heights are recorded) using ZCM, CIM and FCIM methods were (1.060±0.037, 1.430±0.040, 1.70±0.054), (0.910±0.029, 1.270±0.018, 1.460±0.027) and (0.890±0.027, 1.200±0.020, 1.460±0.026), respectively. Although UGAB scintillator exhibits the least discrimination quality, one can choose an appropriate neutron-gamma discrimination method to improve its FoM. The low-temperature flammability, toxicity and high-evaporation properties of NE213 scintillator may motivate some researchers to use UGLLT and UGAB scintillators as alternatives to NE213, however, by selecting the most efficient discrimination method.

    更新日期:2020-01-17
  • Magnetic quenching of positronium studied by positron annihilation lifetime and Doppler broadening measurements
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2020-01-17
    J.D. Liu; J.Q. Guo; M. Luo; Z. Wang; H.J. Zhang; B.J. Ye; Z.Q. Chen

    Annihilation of positronium (Ps) in static magnetic fields is investigated by positron annihilation lifetime (PAL) and Doppler broadening (DB) measurements of γ-Al2O3 nanopowder. The properties of four eigenstates of Ps atoms (|1,1〉, |1,−1〉, |+〉 (long-lived eigenstate mixed from |1,0〉 and |0,0〉 due to Zeeman effect), and |−〉 (short-lived eigenstate mixed from |1,0〉 and |0,0〉 due to Zeeman effect)) were revealed from PAL and DB results. Thereafter, with magnetic field increasing from 0.105 to 0.760 T, clear and regular variation of Ps annihilation parameters are observed: (1) The mean lifetime of the three long-lived Ps states (|1,1〉, |1,−1〉, and |+〉) shows clear quenching effect; (2) The formation probability of each Ps eigenstate (|1,1〉, |1,−1〉, |+〉, and |−〉) keeps unchanged; (3) The intensity of the narrow component (derived from multi-Gaussian fitting) of DB spectrum exhibits a gradual increase which is in good agreement with the theoretical calculation from PAL results (2γ decay of |+〉 and |−〉 states, and pick-off quenching of long-lived Ps states); (4) The intensity of the low energy region of DB spectrum is diminished by the decrease of 3γ decay of |+〉 state. The quantitative correlations between magnetic field and o-Ps annihilation parameters will be helpful for the further understanding of complex Ps quenching effects, such as the effect mixed from orhto-para spin conversion and magnetic quenching.

    更新日期:2020-01-17
  • Structural analysis and luminescence studies of Ce3+: Dy3+ co-doped calcium zinc gadolinium borate glasses using EXAFS
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2020-01-17
    R. Rajaramakrishna; Y. Ruangtaweep; S. Sattayaporn; P. Kidkhunthod; S. Kothan; J. Kaewkhao

    Ce3+: Dy3+- codoped calcium zinc gadolinium borate glasses were synthesized by traditional melt quenching technique. These glasses after synthesizing they were characterized through density, molar volume, refractive index, FTIR, absorption spectra, photoluminescence properties, structural studies using XANES/EXAFS and life time profile analysis. XANES spectra of Gd LIII-edge and Dy LIII-edge for 20CaCO3 - 20 ZnO - 10Gd2O3 - 49.5B2O3 - 0.5Dy2O3 (C2) and 20CaCO3 - 20 ZnO - 10Gd2O3 – 49B2O3 - 0.5Dy2O3 - 0.5CeF3 (D) glass showed absorption edge at 7249.8 eV and 7795.7 eV respectively confirming the presence of Gd3+ and Dy3+ ions. Ce-LIII edge for D glass shows peaks at ∼ 5728 eV confirming the presence of Ce3+. The Judd-Ofelt (JO) theory investigations have been applied for Dy3+ ions to calculate the Judd-Ofelt (JO) intensity parameters and found that the trend follows Ω2> Ω4> Ω6. The ionic nature of RE3+-O were evaluated by using bonding parameter (δ) value for C2 and D glass and found to be -0.0076 and -0.0102. Radiative properties were subsequently estimated using JO parameters and investigated radiative transition probabilities (AR), stimulated emission cross section (σR) and branching ratio (βR). The photoluminescence and radio luminescence spectra exhibit two prominent emission peaks at 484 (blue) and 575 nm (yellow) that corresponds to the4F9/2 → 6H15/2 and4F9/2 → 6H13/2 transitions respectively. The chromaticity coordinates were evaluated and found that these coordinates positioned in the white region with (x, y) = (0.348 0.382) and (0.325, 0.353) values for C2 and D glasses. The florescence decay from the 4F9/2 level was measure by monitoring the intense 4F9/2 to 6H9/2 transition. The decay time is found to be bi-exponential when monitored at λexi = 387 nm. The results obtained in present work demonstrate that the present glasses could be potential candidate for use in white light solid state lighting applications.

    更新日期:2020-01-17
  • Influence of the number of alkali cation on the photo-induced CoIIIFeII↔CoIIFeIII charge transfer in Csx CoFe PBAs – A Co K-edge XANES study
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2019-02-05
    Amélie Bordage; Anne Bleuzen

    In CoFe Prussian Blue Analogs (PBAs), a small difference in the number of alkali cation per unit cell can lead to drastic differences in the properties of the PBA. We investigate the origin of this effect in order to be able to control it and design new functional materials for data storage devices. Here we characterize the Cs0.7Co4[Fe(CN)6]2.8.17 H2O and Cs2Co4[Fe(CN)6]3.3.11H2O PBAs by Co K-edge in situ XAS. For both PBAs, the photo-induced (PI) CoIIIFeII→CoIIFeIII charge transfer and the different involved states (room temperature, ground and PI) are described. In the case of the Cs0.7 PBA, the relaxation from the CoIIFeIII PI state towards the CoIIIFeII ground state is monitored and quantified. All the results, fully consistent with previous magnetometry and Co L3-edge XAS studies, are discussed with respect to the electronic structure of the Co ions in the different involved states.

    更新日期:2020-01-17
  • First steps towards online personal dosimetry using computational methods in interventional radiology: Operator's position tracking and simulation input generation
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2020-01-16
    Mahmoud Abdelrahman; Pasquale Lombardo; Filip Vanhavere; Alain Seret; Christophe Phillips; Peter Covens

    Interventional radiologists/cardiologists are repeatedly exposed to low radiation doses which makes them the group of the highest occupational exposure and put them at high risk of stochastic effects. Routine monitoring of staff is usually performed by means of passive dosimeters. However, current personal dosimeters are subject to large uncertainties, especially in non-homogeneous fields, like those found in interventional cardiology (IC). Within the PODIUM (Personal Online DosImetry Using computational Methods) research project, a user-friendly tool was developed based on MCNP code to calculate doses to the staff in IC. The application uses both the data of motion tracking system to generate the position of the operator and the data from the Radiation Dose Structure Report (RDSR) from the imaging device to generate time-dependent parameters of the radiation source. The results of the first clinical validation of the system show a difference of about 50% between simulated Hp(10) with MCNP and measured Hp(10) with electronic personal dosimeter worn above the lead apron.

    更新日期:2020-01-16
  • Gamma spectrometry and LabSOCS-calculated efficiency in the radiological characterisation of quadrangular and cubic specimens of hardened portland cement paste
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2020-01-14
    J.A. Suárez-Navarro; A.M. Moreno-Reyes; C. Gascó; M.M. Alonso; F. Puertas

    Pursuant to European Directive 2013/59, materials additioned with NORM waste must be characterised radiologically to determine their acceptability for use in construction. The radionuclides studied to judge that acceptability, 232Th, 226Ra and 40K, are normally measured with gamma spectrometry. Gamma detectors are calibrated by using standards as similar as possible in dimensions and chemical composition as the matrix in the samples to be measured. In light of the broad spectrum of chemical and physical characteristics of NORM samples, experimental calibration is often beyond the means of gamma spectrometry laboratories. As a result, Monte Carlo-based methods are deployed to simulate the experimental setup consisting in detector and sample, both geometrically and chemically. Canberra Industries’ LabSOCS (Laboratory Sourceless Calibration Software) is one of the tools available for such calculations. This study verified the accuracy and precision of the counting efficiency delivered by LabSOCS, both with the standard powder geometry and a new geometry consisting in a 5 cm cubic specimen of Portland cement paste. The findings showed that in both geometries the accuracy and precision of LabSOCS-calculated efficiency (by specimen height and activity), across an energy range from 45.64 keV (210Pb) to 1460.82 keV (40K) met the acceptability criteria routinely applied in environmental radioactivity laboratories. The geometry proposed yielded activity values for the end construction material closer to the true indices than the conventional method consisting in summing the partial activities of the unreacted components.

    更新日期:2020-01-14
  • Study on dynamic characteristics of activated products source term in secondary loop of integrated molten salt reactor
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2020-01-11
    Bo Zhou; Xiao-Han Yu; Ya-Fen Liu; Yang Zou; Pu Yang; Shi-He Yu; Xu-Zhong Kang; Gui-Feng Zhu; Rui Yan

    Source term analysis not only can provide the fundamental data for radiation shielding design, but also has a guiding significance for in-service inspection of the reactor. A numerical analysis model (MAST1.0) for activated products in the secondary loop system of the molten salt reactor (MSR) was developed. The deviation of the simulation results between MAST1.0 and ORIGEN-S are less than 7%, which indicates that they are in good agreements. The amounts of the activated products (16N, 20F and 19O) and the corrosion activated products (60Co, 55Fe, 54Mn, 51Cr, 59Ni, etc.) in the second loop were also obtained by MAST1.0, which show that the total activity of 16N, 20F and 19O is two orders of magnitude higher than that of the corrosion activated products in normal operating conditions. Flow rate has a significant effect on the distribution of 16N, 20F and 19O in the secondary loop. The total activity of 16N, 20F and 19O outside of the core increases monotonically with the increase of the flow rate. The concentration of 16N, 20F and 19O outside of the core tends to be stable, when the flow rate is greater than 1 × 106 cm3 s−1. Corrosion activated products show slowly increasing and decreasing trends in reactor startup and shutdown conditions, so they are the key radioactive sources for radiation protection after long-term shutdown of the reactor.

    更新日期:2020-01-13
  • Internal dosimetry of uranium workers exposed during the nuclear fuel fabrication process in Spain
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2020-01-13
    María Antonia López; Inmaculada Sierra; Carolina Hernández; Soledad García; Daniel García; Agustín Pérez

    Workers in the Juzbadoplant of ENUSA in Spain are exposed to intakes of low enriched uranium during the fabrication of nuclear fuel elements for Nuclear Power Plants. CIEMAT started in 2014 an individual monitoring program for ENUSA workers consisting in routine bioassay measurements of uranium in urine by alpha spectrometry and a methodology of dose assessment based on ICRP Publications 78/68, ISO 27048 standard and IDEAS Guidelines V2. The individual monitoring program is complemented with workplace monitoring using Static Air Samplers (SAS) at the Juzbado facility. Results of routine monitoring data of 24 h-urine samples of Juzbado workforce confirmed low level of chronic intakes of uranium oxides in the plant, combined with acute intakes associated to incidents. IMBA software allows the dose assessments in complex intake regimes of occupational inhalation of Type S uranium compounds. Uncertainties of monitoring data were evaluated using the Scattering Factor approach (ISO 27048) for the intake calculation in the defined internal exposure scenario. A total of 200 workers at risk of internal exposures in the Juzbado facility were included in routine, special, confirmatory or task-relatedmonitoring programs established by CIEMAT in agreement with ENUSA. Annual chronic intakes were assessed for 106 workers with monitoring results abovethe Minimum Detectable Activity (MDA = 0.50 mBq.sample−1 of 234U, 238U and 235U). Committed Effective Doses E(50) > 1 mSv/year were initially detected in 50% of these cases. Maximum annual intakes correspond to few cases of long term exposed workers with E(50) around 5 mSv/year. The preliminary study of the impact on the dose assessment using the new uranium model according to ICRP Publication 137 is presented here, showing a reduction of E(50) around a factor of 4 for workers exposed to uranium oxides re-defined as Type M/S materials (more soluble compounds, higher urinary excretion, lower dose coefficients than Type S uranium materials defined by ICRP Publications 78/68).

    更新日期:2020-01-13
  • Computer simulation of NOx removal from diesel engine off-gases under electron beam and wet scrubber system
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2020-01-13
    Y. Sun; A. Dobrowolski; A.G. Chmielewski; O. Roubinek; A. Pawelec; H. Nichipor

    NOx emission from diesel engine off-gases in marine transportation sector is still an environmental issue to be solved in present day. Electron beam (EB) followed by a seawater wet scrubber method to removal NOx has been experimentally studied (Chmielewski et al., 2018). In this work numerical simulation of NOx reduction using EB followed by a water scrubber system has been carried out. The first stage was to calculate NOx removal versus dose under EB irradiation. Computer code “KINETIC” and Gear method were used, the model has been improved based our previous work (Zwolinska E. et al., 2015) and verified by the experimental results. The calculation results of NOx removal efficiency was 4.9% at 10.9 kGy dose under EB irradiation, which was a little higher than experimental value (3.5%). Computer program MATLAB was used to study NOx absorption in water. The NOx removal efficiency was increased by 17.5% at 10.9 kGy dose for inlet concentration of NOx being 1333 ppm after EB-water absorption process. At the end, NOx reduction in the simulated marine off-gas using microwave plasma was simulated using computer program Chemical Workbench. Less than 20% NOx was removed from the off-gases in microwave plasma reactor even at 9000 kGy dose for the inlet concentration of NOx being 1500 ppm. EB is more energy efficient than microwave plasma for NOx removal.

    更新日期:2020-01-13
  • Inventorying the radionuclides in spent cartridge filters from the primary circuit of a nuclear research reactor by the dose-to-activity method
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2020-01-13
    Ana Paula Gimenes Tessaro; Leandro Goulart de Araujo; Roberto Vicente

    The high activity of spent cartridge filters from the cooling water polishing system of a nuclear research reactor precludes, in routine work of a waste characterization program, the usual method of radiochemical analysis of filter samples. For this waste, the dose-to-activity method, using a gamma spectrometer and a dose rate meter, is an alternative for the determination of the activities of the gamma emitters with acceptable accuracy. The ratio of photon peak-areas from different radionuclides, corrected by the detector energy-dependent efficiency, allowed estimating the proportions between the activities of the different radionuclides present. Finally, the simulation of the counting geometry, using the point-kernel method to estimate the air dose rate resulting from an arbitrary concentration of those radionuclides and the comparison of the calculated with the measured air dose rate has yielded the needed estimates of the activity concentrations. The aim of this paper is to report the development of the method applied for the determination of the concentration of the gamma-emitters present in cartridge filters from the IEA-R1 Nuclear Research Reactor.

    更新日期:2020-01-13
  • Use of gamma cameras for individual monitoring of photon emitting radionuclides based on urine samples in emergency situations
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2020-01-12
    Ämilie Louize Degenhardt Erbe; Ana Letícia Dantas; Wanderson de Oliveira Sousa; Bernardo Maranhão Dantas

    Introduction In nuclear and radiological accidents there is a risk of radioactive contamination and accidental intake of radionuclides. Therefore, the individual monitoring of internal exposures is essential for the prompt response to an emergency situation. Individual monitoring allows classifying and evaluating the accident, preventing the increase of contaminated areas and number of affected people and assessing the efficacy of the remediation actions and the decontamination procedures. This study evaluated the use of gamma cameras for individual monitoring of photon-emitting radionuclides incorporated into the human body based on urine samples to apply as a prompt response in emergency situations. Methods For this, a gamma camera available in a military public hospital located in the city of Rio the Janeiro was calibrated using standard liquid sources of 57Co, 22Na, 137Cs and 54Mn supplied by the National Laboratory of Metrology (LMNRI) of the Institute of Radiation Protection and Dosimetry (IRD), all in a 1 L bottle geometry, simulating an urine bioassay. “Efficiency vs Energy” curves at 5, 10, 15 and 20 cm source-to-detector distances were obtained. Based on the “Efficiency vs Energy” curves Minimum Detectable Activities, Minimum Detectable Intakes and Minimum detectable committed effective dose were calculated for 106Ru, 103Ru, 131I, 134Cs and 137Cs at the four source-to-detector distances. Results The results showed that the gamma camera presents Minimum detectable committed effective dose bellow 1 mSv for 103Ru, 131I, 134Cs and137Cs. For 106Ru the Minimum detectable committed effective dose calculated ranged from 1.84 to 3.40 mSv, which is acceptable in emergency situations. Conclusions It has been concluded that the equipment evaluated in this work shows enough sensitivity for use as screening method in accident situations involving intakes of such radionuclides.

    更新日期:2020-01-13
  • Radiation induced in-situ synthesis of membranes for removal of 2,4-dichlorophenoxy acetic acid from real water samples
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2020-01-12
    Meshude Akbulut Söylemez; Olgun Güven

    A molecularly imprinted membrane for specific removal of 2,4-Dichlorophenoxyacetic acid (2,4-D) was synthesized by γ-initiated polymerization using N-vinyl imidazole as functional monomer and ethylene glycol dimethacrylate (EGDMA) as a crosslinker in methanol:water (1:4 by volume) mixture at room temperature. Functional monomer to template molecule ratio was kept as 4:1. The binding capacity of molecularly imprinted membranes was obtained as 75% within 100 min for 5 mg/L 2,4-D solution (on 25 mg of imprinted polymer). Binding characteristics in various template molecule concentrations and pH values were studied. Furthermore, the selectivity of the imprinted membranes was evaluated by using structurally similar herbicides such as (R)-2-(2,4-dichlorophenoxy) propanoic acid (2,4-DP) and 4-chlorophenoxyacetic acid (4-CPA). The binding capacity of membrane was investigated by using real water samples. In order to investigate the free volume size of the membranes positron annihilation lifetime spectroscopy (PALS) experiments were carried out.

    更新日期:2020-01-13
  • Estimation of effective dose using two ICRP criteria, applied to radiation protection of personnel in an unshielded PET cyclotron facility
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2020-01-10
    Teresa Jakubowska; Magdalena Długosz-Lisiecka

    Neutrons have no charge, but ionize indirectly through secondary particles.Neutron radiation is a source of exposure to ionizing radiation for personnel working withcyclotronsthat produce isotopes forpositron emission tomography (PET) radiopharmaceuticals.During production of isotopes in cyclotron in nuclear reactions beside gamma radiation are created also neutrons. The new recommendations of the International Radiological Protection Commission (ICRP) −103 have changed the method of calculating the neutron radiation weighting factor and the tissue weighting factor value that were defined in earlier ICRP recommendations (ICRP, 2007; ICRP, 1991; ICRP, 1996). The aim of this work is to estimate how this change influencesthe calculation of an effective dose in neutron radiation with a complex energy spectrum. This spectrum consists of three regions: a plateau area for thermal neutrons, a peak in the area of fast neutrons with a sharp edge from the high-energy side, and a mild field of decline for intermediate and epithermal neutrons. The application of new recommendations reduces the calculated effective dose by more than 10 mSv. The effect of increasing the effective dose for the maximum fluence area, i.e. energy near 1 MeV,by using a higher value of wR is negligible. The study finds that the new recommendations are less restrictive, and this is of great practical importance becauseno modification to the used shields is required.

    更新日期:2020-01-11
  • Neutron and gamma-ray radiation fields characterisation in a 241Am–Be irradiator in view of its use as research testing tool
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2020-01-10
    N. Marchese; D. Fiore; D. Cottone; A. Parlato; E. Tomarchio

    A neutron irradiation facility based on four 241Am–Be sources, each one with an activity of 111 GBq, placed in Plexiglas pipes inside a tank filled with water used both as a moderator and a biological shielding, has been realized at the Engineering Department of Palermo University. In view of its use as a testing tool in various research activities, a characterisation of the irradiator has been carried out through the determination of neutron and gamma-ray flux profiles, the evaluation of the thermal to total neutron flux percentage ratio and of the epithermal neutron shaping factor. To this aim, results of a Monte Carlo (MCNP5 code) simulation based on a previously validated source model have been compared with the experimental results obtained from TLD dosimeters and activated gold foils. Experimental values show a good agreement with MCNP5 evaluations, highlighting a gradually decreasing of dose values as a function of the distance from the lying plane of sources. Maximum values of experimental neutron fluxes have been found to be (3.73 ± 0.38) × 104 cm−2 s−1 (thermal) and (2.13 ± 0.25) × 104 cm−2 s−1 (epithermal and fast), with a percentage of 64% of thermal to total neutron flux and epithermal neutron shaping factor equal to −0.16 ± 0.04. Both neutron and gamma fluxes for the most used positions inside the irradiation channel can then be provided and the main parameters for any irradiation plane can be easily established.

    更新日期:2020-01-11
  • Dosimetric utility of structural changes in gamma irradiated graphite-rich pencils
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2020-01-10
    S.F. Abdul Sani; S.S. Ismail; K.S. Almugren; M.U. Khandaker; D.A. Bradley

    9B and H grade carbon-based pencil (carbon concentrations approaching 81 and 62 wt respectively %) have been investigated for radiotherapy dosimetry applications, offering low dependence on photon energy and near soft tissue effective atomic number. Comparison has been made with highly oriented pyrolytic graphite (HOPG), a pure and ordered synthetic form of graphite. The samples were exposed to 60Co gamma ray doses from 0 to 20 Gy (encompassing the range of doses utilized in fractionated radiotherapy), structural interaction alterations resulting from the radiation doses being observed via Raman and Photoluminescence (PL) spectroscopy and X-ray diffraction (XRD). Among the most prominent features to be observed in Raman spectra are the so-called G and D peaks, appearing at 1578 cm−1 and 1348 cm−1 respectively. The intensity ratio ID/IG was used for further characterization of the dose-dependent defects produced in the graphitic materials. From PL measurement, sample average energy band gap values are observed to be within the region 1.114–1.116 eV, being considered direct bandgap-like semiconductors. The characteristic XRD crystal plane Miller index (002) peak was observed in order to calculate the atomic spacing, lattice constant and the degree of structural order of the irradiated samples.

    更新日期:2020-01-11
  • Dosimetric properties of thermoluminescent pellets of CaSO4 doped with rare earths at low doses
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2020-01-10
    L.A. Forner; C. Viccari; P. Nicolucci

    Thermoluminescent dosimeters are widely used in radiation dosimetry, including low dose applications such as personal dosimetry. This work aimed to manufacture thermoluminescent pellets using CaSO4:Tm; CaSO4:Dy,Tm; CaSO4:Dy, Tb and CaSO4:Dy, Eu phosphors and to study their dosimetric properties in comparison to commercially available CaSO4:Dy (TLD-900). The phosphors were synthesized by the slow evaporation route using a solution of sulfuric acid, calcium carbonate and the dopants. The pellets were manufactured using Teflon as aggregate agent. The glow curves of the different pellets were measured and the integral of the dosimetric peak was used as the dosimetric response for each material. The dose-response curves were measured in a dose range of 100 μG y to 50 mGy by 137Cs (γ-source) and X-rays (30 kVp up to 120 kVp). The energy dependence and fading of the pellets were also studied. Groups of 30 pellets were used to investigate the response homogeneity for the studied materials. The glow curves for all the studied materials (excluding CaSO4:Eu) showed the maximum luminescent emission at around 260 °C, but with different intensities. The CaSO4:Tm pellets showed the highest thermoluminescent emission among the studied materials. All the materials showed a linear response in the studied dose range, with CaSO4:Tm pellets showing the highest sensitivity at all radiation qualities. The highest energy dependence was found for the ISO N-40 beam quality (40 kVp X-rays) for all materials when compared to irradiations by the 137Cs source. A 7.7% fading for the CaSO4:Tm was found for a period of two months. All the manufactured pellets showed better dosimetric properties than the studied standard CaSO4:Dy.

    更新日期:2020-01-11
  • Comparison of neutron activation analysis (NAA) and energy dispersive X-ray fluorescence (XRF) spectrometry for the non-destructive analysis of coins minted under the early Piast dynasty
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2020-01-09
    Andrzej Bolewski; Marta Matosz; Władysław Pohorecki; Julio M. del Hoyo-Meléndez

    Surface enrichment of silver-copper alloys is a current subject of research in archaeometry, while its origin in cultural heritage objects remains unclear. Due to their low penetration depth, surface techniques may give misleading results if the objects analyzed show this enrichment behavior. To study this effect, the surface and bulk composition of a group of Polish coins minted in the X-XI centuries during the early Piast dynasty were investigated using energy dispersive X-ray fluorescence (XRF) spectrometry and neutron activation analysis (NAA). A comparison of the results obtained using these two techniques permitted to classify the coins in two groups. The first group exhibited similar bulk and surface compositions, while coins in the second one showed silver surface enrichment. In addition, a correlation between silver and gold was observed after evaluating the analytical results providing a first step in the determination of silver provenance.

    更新日期:2020-01-09
  • Online measurement of the intensity of keV positron beam
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2020-01-09
    Z.Y. Zhang; Y. Wu; S. Liang; Z.X. Ke; X.G. Xia; B.Y. Wang; P. Zhang

    The intensity of keV positron beam generated by 22Na slow positron beam device is weak (generally less than 106 e+/s). Therefore, the traditional method of obtaining beam intensity by Faraday cup is no longer applicable. Currently published methods of obtaining beam intensity are relatively deficient and insufficient. In this paper, a new method was developed to obtain the real-time intensity of positron beam, that is, the HPGe detector was used to collect the 511-keV photons emitted from the thick target bombarded by the positrons, combining with the experimental calibration value of HPGe detector for 511-keV photons as a22Na standard point source placed at the collision point of thick carbon target, and with the relevant parameters got by Monte Carlo simulation. Moreover, the method our group developed and the corrected method of others were both applied for online measurement of beam intensity of 4–9 keV positrons colliding with the pure thick targets (Al, Zn, Nb and Pb). Through comparative analyses, the method our group developed could measure positron beam intensity online more accurately.

    更新日期:2020-01-09
  • Localized extra focal dose collimator angle dependence during VMAT: An out-of-field Monte Carlo study using PRIMO software
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2020-01-08
    Firass Ghareeb; Alessandro Esposito; Joana Lencart; João A.M. Santos

    Purpose Patients undergoing 3DCRT on TrueBeam linac equipped with HD_120_MLC are subjected to localized extra-focal dose (LEFD) in a specific region out of the treatment field. The dose in this region is up to 160% of the mean transmitted dose through MLC. Although VMAT provides a more conformal dose to PTV and better sparing to OAR, it implies more monitor units and irradiating more healthy tissues outside the treatment field. One aims to investigate the dose distribution due to LEFD during VMAT and the collimator rotation angle optimization to minimize this extra dose. Methods Eight VMAT plans for a hypothetical abdominal tumor were contoured on an anthropomorphic pediatric phantom and calculated on Eclipse TPS. The plans were optimized to the same dosimetric objectives at PTV and OAR with different collimator rotation angles. They were also simulated using PRIMO Monte Carlo software. The dose out of the treatment field was evaluated in eight spherical structures distributed at different distances from the isocenter. To validate the results, QA verification plans were created for these plans, were measured by EPID and simulated in a virtual phantom of the EPID. Measured and simulated QA plans were compared using gamma-index methodology. Point dose measurements were also used to verify Monte Carlo simulations accuracy out of the treatment field. Results Both measured and simulated QA dose distributions showed that each treatment arc has two LEFD regions out of the treatment field which were not calculated by TPS. The simulated treatment plans showed LEFD as cylindrical dose distributions, 10 cm height, with the diameter of X-jaws aperture. At 0o rotation the two LEFD regions corresponding to the two-treatment arcs are superimposed. As rotation angle increases the two cylindrical distributions start to drift apart, but their intersection remains localized along the central axis until they are completely separated. Conclusion The LEFD can be avoided during VMAT without compromising the treatment plan objectives by increasing the collimator rotation angle to relocate LEFD out of the body.

    更新日期:2020-01-08
  • Irradiation effects on chemical and functional qualities of ready-to-eat Saengshik, a cereal health food
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2020-01-08
    Gui-Ran Kim; Sudha Rani Ramakrishnan; Kashif Ameer; Namhyeok Chung; Yu-Ri Kim; Joong-Ho Kwon

    Saengshik is an uncooked Korean meal comprising of more than thirty different ingredients of plant and animal origins. In Korea, to reduce the microbial loads in the product, electron-beam (EB) or gamma-ray (GR) irradiation at 5 kGy is permitted for its major cereal ingredients. But decontamination effects are not often satisfied. Considering the over-doses in commercial treatment, this study intended to investigate EB and GR irradiations up to 10 kGy on the physicochemical and functional qualities of prepackaged Saengshik. The reducing sugar and amino nitrogen were not significantly affected, whereas total chlorophylls, carotenoids, phenolics, and antioxidant activities were more sensitive to both types of irradiation. Total carotenoids and chlorophylls were reduced at high irradiation doses. In contrast, irradiation increased the free radical scavenging abilities that may be due to increase in total phenolic content (139.63–169.02 mg/100 g, EB; 139.63–168.56 mg/100 g, GR). Although there was slight decrease in the chlorophyll and carotenoid constituents of Saengshik, irradiation up to 10 kGy improved its antioxidant activity without affecting the reducing sugar and amino nitrogen. Dose escalation up to 10 kGy for the cereal product revealed stable reducing sugar and amino nitrogen contents with slight changes below 0.31% in total chlorophylls, carotenoids, phenolics, and antioxidant properties.

    更新日期:2020-01-08
  • Studies on the ontogenic radio-sensitivity in Callosobruchus species complex to establish a generic dose of phytosanitary irradiation as a post harvest quarantine treatment for disinfestation of pulses
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2020-01-08
    R.K. Seth; B.V. Patil; Mahtab Zarin; Zubeda Khan; S.G. Hanchinal; V. Rachappa; G. Akshatha; Ranjana Seth

    The effects of gamma radiation were observed on the metamorphosis and reproduction as key target features to be intercepted for disinfestation of the three major pest bruchid species, Callosobruchus maculatus (Fabricius), C. analis (Fabricius) and C. chinensis (Linnaeus) irradiated in the various ontogenic stages. The present study was aimed to determine an efficacious generic dose of phytosanitary irradiation (PI) for bruchid disinfestation in pulses. Callosobruchus chinensis was the most radio-resistant species among the present tested species, and male bruchids were more radio-resistant than the females in this species complex. In this complex of tested bruchid species, the gamma dose required to cause 100% metamorphic disruption in the most radio-resistant pre-imaginal stage (pharate adult) was 20–46% higher than the dose required to induce complete sterility in the most radio-resistant imaginal stage (4–5 day old). The effective dose inducing 99.9% impact (ED99.9) was 105 Gy for sterility induction but ∼181 Gy to induce metamorphic disruption in the most radio-resistant pre-imaginal pharate adult in C. chinensis, whereas the most radio-resistant imaginal stage (4–5 day old adult) of this species required 124 Gy for complete sterilization. Based on these results, 160–200 Gy as phytosanitary irradiation dose range was evaluated on a semi-large scale testing on the pigeonpea pulse seeds having mixed infestation of Callosobruchus species complex, which indicated that 200 Gy might be considered as a feasible generic dose of phytosanitary irradiation for bruchid disinfestation in pulses.

    更新日期:2020-01-08
  • Simultaneous intramolecular crosslinking and sterilization of papain nanoparticles by gamma radiation
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2020-01-08
    Gabriela N. Fazolin; Gustavo H.C. Varca; Lucas F. de Freitas; Bozena Rokita; Slawomir Kadlubowski; Ademar B. Lugão

    Papain-based nanoparticles were recently developed using radiation technologies and proven effective to generate nanosized crosslinked papain particles with preserved enzymatic activity. The applications of such nanostructured systems are expected to be similar to native papain with considerable biopharmaceutical advantages and concern drug loading among other biotechnological applications. The nature of such crosslinks and the possibility to provide simultaneous sterilization have been hypothesized but remain not totally clarified. This manuscript advances the discussion on the radiation-induced synthesis of protein nanoparticles by approaching the nature of the crosslinking and the possible contribution of bityrosine linkages and disulfide bridges to the overall nanoparticle assembly as well as the feasibility of the simultaneous sterilization process under the pre-established conditions of processing. Papain nanoparticles were synthesized and characterized according to size, proteolytic activity, bityrosine, cysteine content and molecular weight by SDS-PAGE upon sonication at 40 kHz. Bacterial identification and the sterility tests were performed in accordance with ISO 11737 prior to and after inoculating 106 CFU of Corynebacterium xerosis. Our experiments evidenced the crosslinking of rather intra- than intermolecular nature and a contribution of cysteine bridges and bityrosine linkages to the stabilization and formation of the papain nanoparticle assembly. The technique was effective to promote simultaneous crosslinking and sterilization at the established conditions of processing and may be validated in accordance with the ISO 11137.

    更新日期:2020-01-08
  • Use of biological dosimetry to confirm radiation exposure: Case study
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2020-01-07
    Octávia Monteiro Gil; João Oliveira Martins; Pedro Rosário

    The notification of a radiological accident/incident in Portugal is very rare. This study was conducted after a suspected occupational overexposure to ionizing radiation by a radiologist whose thermoluminescent dosimeter (TLD) had exceeded the value allowed by Portuguese legislation. After verifying the facilities a biological dosimetry study using the dicentric assay was performed using the dose-response curve for the Portuguese population. Cytogenetic dosimetry confirmed the TLD value and the worker's exposure to an accidental dose of ionizing radiation. The Portuguese Directorate-General for Health imposed health surveillance for the patient and he was excluded from further professional radiation exposure for 5 years.

    更新日期:2020-01-07
  • Co-60 gamma radiation influences on the electrochemical, physical and electrical characteristics rare-earth dysprosium oxide (Dy2O3)
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2020-01-07
    Umutcan Gurer; Ozan Yilmaz; Huseyin Karacali; Senol Kaya; Ercan Yilmaz

    Dysprosium Oxide (Dy2O3) gate dielectric layers were deposited by Electron-Beam evaporation onto p-Si (100) wafers. The effects of gamma irradiation on the physical, electrochemical, and electrical properties of Dy2O3/p-Si thin films were investigated in detail. The evolutions on the crystallographic and morphologic characteristics of the films under gamma irradiation were analyzed by X-ray diffraction (XRD) and Atomic Force Microscopy (AFM), respectively; while irradiation effects on the electrochemistry of the films were characterized by X-ray photoelectron spectroscopy (XPS). Furthermore, variations on the electrical characteristics of Dy2O3/p-Si thin films were also specified by Capacitance-Voltage (C–V) and Conductance-Voltage (G/ω-V) measurements. No significant changes on the crystallographic orientation were observed after gamma irradiation exposures. However, the grain size of the films was increased slightly due to the local heating aggregated the smaller grains into a bigger cluster. In addition, the surface roughness was increased after irradiation indicating that deforms the films’ surface morphology. The XPS analysis revealed that electrochemically two different phases exist in the virgin Dy2O3/p-Si thin films. These phases are Dysprosium sub-Oxide (DyxOy) and oxygen deficient in Dy2O3 films. After irradiation exposures, oxygen incorporation, vacancy, and interstitial defects formation were observed in the electrochemical characteristics of the films. On the other hand, the capacitance curves exhibit kinks in the region between depletion and accumulation due to the presence of the intermixing phases of Dy2O3 films. The capacitance of samples significantly increased with the increasing dose, which are correlated with the generated interface state density and/or improvement of dielectric characteristics of Dy2O3 owing to oxygen diffusion.

    更新日期:2020-01-07
  • Neutron activation analysis of meteorites at the VR-1 training reactor
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2020-01-07
    Milan Stefanik; Martin Cesnek; Lubomir Sklenka; Tomas Kmjec; Marcel Miglierini

    Samples of space objects were characterized using instrumental neutron activation analysis (NAA) combined with conversion electron Mössbauer spectrometry. Fragments of Moldavites, Muonionalusta meteorite and Sikhote-Alin meteorite were irradiated in the thermal neutron field of the low-power VR-1 training reactor operated by the Czech Technical University in Prague. Activated samples were investigated by means of nuclear gamma-spectrometry technique (semiconductor HPGe detector). Qualitative analysis revealed the occurrence of Na, Al, Mg, Cl, K, Ti, V, Mn, Fe, Sr, and Ba in Moldavites, Na, Cl, Mn, Fe, Co, Cu, Ni, As, and Au in Muonionalusta iron meteorite, and Ni, Co, Fe, and Mn in Sikhote-Alin iron meteorite. Employing the comparative NAA, the concentration of Na, Al, K, Ti, V, Fe, and Sr in Moldavite, concentration of Na, Fe, Ni, and Au in Muonionalusta meteorite, and concentration of Ni in Sikhote-Alin meteorite was determined. Moreover, Muonionalusta meteorite structure was investigated using the conversion electron Mössbauer spectrometry at room temperature, and α-(Fe, Ni) phase and γ-(Fe, Ni) phase were identified. The obtained results clearly show that the low-power VR-1 research reactor (80 W) is an excellent tool for NAA experiments, and that nuclear-analytical techniques can provide useful data for other scientific branches.

    更新日期:2020-01-07
  • Investigation of various concrete compositions with respect to gamma-radiation transmission properties of Cs-137
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2020-01-07
    F. Becker; D. Köhnke; M. Reichardt; H. Budelmann

    We investigated different concrete samples with respect to their gamma-radiation transmission properties of Cs-137. From results of gamma-spectroscopic measurements, respective half-value layers are presented for ordinary, hematite, and barite concrete. The outcomes are compared to literature values. In addition, CT scans were performed and analyzed to reveal structural impacts on shielding properties. Finally, Monte-Carlo simulations were performed to examine the reliability of theoretical predictions. As a result, precise specification of the concrete composition is essential to simulate shielding designs of new facilities, as accurate theoretical predictions are necessary to avoid excessive costs due to oversizing or rework.

    更新日期:2020-01-07
  • Ionizing radiation shielding properties of metal oxide impregnated conformal coatings
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2020-01-07
    Michael DeVanzo; Robert B. Hayes

    Conformal coatings provide environmental protection for sensitive military electronics. Preliminary MCNP6® modeling of metal oxide impregnated acrylic conformal coatings indicates a factor of 300 reduction in gammas below 10 keV and up to a 225% reduction in neutron displacement damage to Si-based electronics across the Watt spectrum. This work provides data which can allow an optimal overall shielding worth per total mass to be evaluated.

    更新日期:2020-01-07
  • Influence of structure on catalytic activity of nano - manganese oxide
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2020-01-06
    R. Puspalata; D. Mal; S. Amirthapandian; S. Rangarajan

    Nano-oxides of manganese synthesized from the radiolytic reduction of permanganate (MnO4-) medium at varying pH in ambient temperature showed differences in structural properties. In the present communication, we report the effect of variance in the structural morphology on the hetero-catalytic activity of manganese nano-oxides. Applications of these radiolytically generated manganese nano-oxides, as catalysts were tested by monitoring the decomposition of H2O2 and N2H4 solutions at room temperature and suitable mechanism has been proposed. The catalytic decomposition rates of H2O2 and N2H4 solutions increased in the presence of oxides formed from the radiolysis of alkaline permanganate solutions. The kinetics of the catalytic activity of the nano-oxides was correlated with their high surface area, large pore volume, adsorbed –OH groups, varying oxidation states of Mn, and their microstructures.

    更新日期:2020-01-06
  • Assessments of the characteristics of an extrapolation chamber for 60 to 200 kVp X-rays: Experiment and Monte Carlo simulation
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2020-01-06
    Seyed Milad Vahabi; Mojtaba Shamsaei Zafarghandi

    According to the principles of radiation protection, the patient and personnel dose should be decreased to a reasonably achievable level. Therefore, it is essential to use reliable dosimeters in the radiation dosimetry course. One of these dosimeters is an extrapolation chamber. It is a plane-parallel ion chamber (PPIC), which its sensitive volume can be varied. In this paper, the performance of an extrapolation chamber has been evaluated in 60–200 kVp X-rays. It was submitted to several necessary tests, and also simulated with MCNP code. All of the results were within the recommendations of the International Electrotechnical Commission (IEC). The chamber responses were linear with electrode separation. The comparison between experiment and simulation agrees in an overall sense within 5.4% in the worst case. The results indicated the usefulness of the chamber in this energy range. They show that the extrapolation chamber can also be used for computed tomography (CT) beams, considering that a primary standard system doesn't exist for these beams yet.

    更新日期:2020-01-06
  • Novel microporous surface and blue emission of argon ion implanted polyvinylacohol/bionanohydroxyapatite coatings
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2020-01-03
    K.R. Karthikeyan; K. Thanigai Arul; J. Ramana Ramya; P.Y. Nabhiraj; Ranjini Menon; J.B.M. Krishna; S. Narayana Kalkura

    PVA/HAp based bionanocomposite coatings (PHAp) are prepared by the microwave-assisted deposition technique. The surface of the coatings is modified using low energy (90 keV) argon (Ar9+) ions with various fluences 1×1014, 1×1015 and 1×1016 ions/cm2. A significant reduction in crystallite size attained at lower fluence (1×1014 ions/cm2) with a variation on functional groups of HAp and polymer. Microporous surface with an agglomerated particle size (4 to 5 μm) is attained at the lower fluence. The band gap and the in-vitro bioactivity of the coatings were enhanced on implantation. Photoluminescence analysis illustrated a blue emission at the lower fluence by the formation of new defect energy levels. Ion implantation tailors hydrophilic and weak hydrophobic surface of bionanocomposite coatings. Thus, from overall results demonstrated that the surface modified PHAp coatings shed light on optoelectronics field by tuning defect's energy levels. Besides it could also be useful in biomedical as well.

    更新日期:2020-01-04
  • Irradiated glass and thermoluminescence yield: Dosimetric utility reviewed
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2020-01-03
    D.A. Bradley; M.U. Khandaker; Abdulaziz Alanazi

    With numbers of efforts being made towards harnessing the thermoluminescence yield of doped glass media for dosimetric applications, predominantly in the radiotherapeutic regime, review is provided of the background to this, tracing developments leading to the present day. Included are an examination of the relative strengths of the various TLD currently on offer and that of glass fabrications, commercial Ge-doped optical fibre as well as novel fibres fabricated from Ge-doped glass. The demands that modern radiotherapeutic dose delivery systems are placing upon these passive forms of dosimetry are reviewed together with the various responses arising from current efforts. Also reviewed are the basis of the luminescence yield, citing the defect types occurring in silica, even in the absence of extrinsic dopants.

    更新日期:2020-01-04
  • Polysaccharides from Annona muricata leaves protect normal human epidermal keratinocytes and mice skin from radiation-induced injuries
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2020-01-03
    Eui-Baek Byun; Ha-Yeon Song; Woo Sik Kim

    Radiation-induced skin injuries are a common side effect of radiotherapy. Plant-derived polysaccharide is considered as an attractive cosmeceutical ingredient for skin damage therapy. This study was conducted to investigate the protective effects of Annona muricata leaf polysaccharide (ALP) on radiation-induced skin injuries by using in vitro and in vivo models. In normal human epidermal keratinocytes (NHEKs), ALP treatments reduced irradiation-induced apoptosis by increasing antioxidant enzymes activities, including superoxide dismutase (SOD) and catalase. Furthermore, ALP treatments decreased levels of interleukin-1β, nucleotide-binding domain and leucine-rich-repeat-containing family pyrin 3 (NLRP3), and cleavage of caspase-1 and caspase-3. Most importantly, the topical application of the ALP cream showed protective efficacy against irradiation exposure, including the reduction of epidermal thickening, as well as an increase in the number of apoptotic cells and antioxidant enzyme (SOD and catalase) activities in skin tissue. Our results indicate that ALP can be potentially used to treat radiation-induced skin injuries.

    更新日期:2020-01-04
  • Implementation of eye-lens dosimetry in Poland
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2020-01-02
    Agnieszka Szumska; Maciej Budzanowski; Izabela Milcewicz-Mika; Renata Kopeć

    It has been seven years from the ICRP Statement on tissue reactions containing the recommendations for an equivalent dose limit for the lens of the eye of 20 mSv per year for workers (ICRP, 2012), and has been 7 years since Laboratory of Individual and Environmental Dosimetry (LADIS) introduced in practice eye lens doses measurement. The reduction of the limit for occupational exposure for the lens of the eye needs adequate approaches for eye protection and eye dose monitoring. The most accurate method for monitoring the equivalent dose to the lens of the eye is to measure the personal dose equivalent Hp(3) with a dedicated dosimeter worn as close as practicable to the eye. To measure eye lens doses in terms of this quantity a dosimeter and the appropriate method has been introduced in the largest dosimetry service in Poland. This paper presents historically the introduction of eye-lens dosimetry in routine measurements and an analysis of the exposure results of the eye dose lenses. Results of measurements of Hp(3) from eye lens dosimeters (almost 5000 quarterly readouts), issued in the years 2012–2018 were reported. In measurements EYE-DTM dosemeter developed within ORAMED EU project (Vanhavere et al., 2011) and high-sensitivity MCP-N (LiF:Mg, Cu, P) thermoluminescence detectors were used. The frequency distribution of eye lens dose measurements performed using specially dedicated dosimeters, via their Hp(3) operational values, over 3-month periods, after subtraction of natural background in 74% cases are below 0.1 mSv. In the case of the new operational quantity, Hp(3) the number of workers, which exceed the new limit during 7 years monitoring period was 48 (1%). The study showed considerable uncertainties associated with the assessment of eye lens dose from the commonly used whole body dosimeters on the chest in terms of Hp(10) and ring dosimeters on the finger which measures skin doses in terms of Hp(0.07). Therefore, only monitoring of the eyes with specific dosemeters for yearly follow-up can provide accurate annual doses.

    更新日期:2020-01-02
  • A nano-microdosimetric characterization of a therapeutic carbon ion beam at CNAO
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2020-01-01
    D. Bortot; D. Mazzucconi; A. Pola; A. Fazzi; M. Pullia; S. Savazzi; P. Colautti; V. Conte; S. Agosteo

    A nano-microdosimetric tissue-equivalent proportional counter (TEPC) capable of measuring microdosimetric spectra of ionizing radiation in the range 500–25 nm was designed, constructed and deeply characterized in order to fill the gap between nanodosimetry and experimental microdosimetry. This work describes the first microdosimetric characterization at nanometric level of a 195.2 MeV/u carbon ion beam available at CNAO (National Centre for Oncological Hadron Therapy). The detector was properly placed at different depths in PMMA phantom across the depth-dose profile of the primary beam for measuring microdosimetric distributions for different simulated site sizes down to 25 nm at different depths. The acquired spectra show that this TEPC is capable of reproducing the beam slowing down, showing a shift towards higher lineal energies as the primary particles slow-down. Moreover, the distributions at different simulated site sizes for the same depth are influenced by secondary electrons: smaller site size spectra exhibit a shift towards higher lineal energies as the site decreases, while this is not the case for more distal positions, where the edge of the spectra is almost independent of the simulated site size. Monte Carlo simulations performed with the FLUKA code show a good agreement with the experimental results obtained in the present paper.

    更新日期:2020-01-01
  • Effect of borate glass network to electrochemical properties: Manganese-doped lithium borate glasses
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2019-12-31
    Amorntep Montreeuppathum; Pinit Kidkhunthod; Saroj Rujirawat; Rattikorn Yimnirun; Supree Pintsoontorn; Santi Maensiri

    Recent development of manganese-lithium borate glasses for applications as supercapacitor was reported. The glasses were prepared by melt-quench technique and characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), and Uv-visible spectroscopy (UV-VIS). The paramagnetism of synthesized glasses was observed at room temperature measured by vibrating sample magnetometry (VSM). The electrochemical properties were studied by cyclic voltammetry (CV). The specific capacitance of 0.2MnO2-0.8(Li2O-xB2O3) glasses were increase from 144 F g−1 to 196 F g−1 for x = 1 to x = 3 (mol%) with scanning rate of 5 mV s−1. However, the specific capacitance was decrease when x = 4. To understand the structure-function of these glasses, the x-ray absorption spectroscopy (XAS) was also used to study a local structure and oxidation state of Mn content in these glasses. Mixing of Mn2+/Mn3+ oxidation state was exhibited with the mean Mn–O bonding distance of approximately 2.0495 Å.

    更新日期:2019-12-31
  • Determination of a consensus scaling factor to convert a Co-60-based alanine dose reading to yield the dose delivered in a high energy electron beam
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2019-12-31
    Malcolm McEwen; Arne Miller; Ileana Pazos; Peter Sharpe

    An analysis of the published literature has been carried out to determine a consensus value for the scaling factor required to convert a dose determination using alanine based on a Co-60 calibration to yield the dose delivered in a high energy electron beam (≥6 MeV incident). Published data from the last 15 years were reviewed and combined to give a single, average, scaling factor. In carrying out this analysis, no attempt was made to deconstruct each experiment. The final results of each investigation were used as a coherent ensemble if independent determinations, irrespective of method or alanine dosimeter supplier. Experimental and Monte Calculations were considered separately and only the experimental data was used to determine the scaling factor. The results from six investigations were found to be consistent within their uncertainties and an overall conversion factor of 1.014 (standard uncertainty = 0.5%) was obtained. To be explicit, alanine doses determined from a Co-60 alanine calibration should be multiplied by this factor to yield the dose delivered in an electron beam. This scaling factor represents the consensus recommendations of the National Research Council, the National Institute for Standards and Technology, the Technical University of Denmark and the National Physical Laboratory. By adopting a common factor, it is hoped to improve the consistency of dosimetry at industrial dose levels using high-energy electron beams.

    更新日期:2019-12-31
  • Calibration of a SPECT-CT gamma camera with child and adult thyroid-neck phantoms for in vivo monitoring of radioiodine in the exposed population in case of nuclear emergency
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2019-12-30
    Juan Francisco Navarro; Begoña Pérez; María Antonia López; Rodrigo Plaza; Zulima Aza; Rafael Plaza

    The need to quantify the uptake of 131I in the thyroid of the exposed population or workers is one of the main concerns to take into account in case of nuclear or radiological emergencies. In such scenarios, due to the high volatility and rapid intake by inhalation of 131I, it is very important a rapid identification of the exposed individuals to know their level of internal contamination in order to establish action protocols and countermeasures. In vivo measurements of 131I in the thyroid by gamma spectrometry at Whole Body Counters (WBC) is the recommended technique, but it is difficult to manage in case of a large number of individuals potentially exposed. It is known that gamma cameras located in the nuclear medicine services are available at most hospitals and could be used as an alternative method in order to provide support in the emergency response. Thus, this work describes a methodology to calibrate this kind of equipment with anthropometric phantoms to carry out direct measurement of 131I in thyroid for the quantification of internal contamination of the exposed population. A Gamma Camera (GC) of a public hospital from Madrid, H.U. La Paz, was calibrated for such purpose taking into account that a realistic geometry (10 cm distance from GC to phantom) and a rapid screening (counting time of 300 s with collimators removed) of internally contaminated individuals is necessary at early stage response. The calibration factors obtained for 131I vary with thyroid size being in the range of 0.0459 to 0.0541 cps·Bq-1. The minimum detectable activity (MDA) also varies with the thyroid size of the phantoms being in the range of 67 Bq to 79 Bq. An estimation of minimum detectable effective dose for children (E(70)) and adults (E(50)) has been carried out, taking into account such MDA values. Results show that, assuming a scenario of acute inhalation of 131I by members of the public, this methodology allows estimating doses far below 1 mSv three days after the intake. Moreover, the validation of the methodology has been carried out by participating in an international intercomparison exercise (CATHYMARA project, EC-OPERRA 2016–2017) for the in vivo measurement of 131I in thyroid to the exposed population in emergencies.

    更新日期:2019-12-30
  • Laser induced breakdown spectroscopy methods and applications: A comprehensive review
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2019-12-30
    Syed Kifayat Hussain Shah; Javed Iqbal; Pervaiz Ahmad; Mayeen Uddin Khandaker; Sirajul Haq; Muhammad Naeem

    Laser induced breakdown spectroscopy has become an established analytical atomic emission spectroscopic technique. It has analytical and technical advantages over other existing techniques. It is a rapid, non-contact technique which is capable of providing qualitative and quantitative analytical information for any sample without any sample preparation. The instrumentation is simple, rebuts, compact and even provides remote analysis. The aim of the current study is to provide a critical review of “laser induced breakdown spectroscopy” in several aspects. First part focuses on the comparison of the “laser induced breakdown spectroscopy” with other well established techniques. In this section, the sensitivity, accuracy and sample preparation are compared and summarized. The second parts is a discussion on the experimental setup and instrumentation. In third part, a complete review of qualitative and quantitative analysis has been summarized. In addition, the effects of different experimental parameters and potential applications of “laser induced breakdown spectroscopy” in different fields of modern technologies have also been described in the current study.

    更新日期:2019-12-30
  • Scatter-to-primary ratio in cone beam computed tomography with extended source to image-receptor distance for image-guided proton beam therapy system
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2019-12-29
    Shu-Ju Tu

    Purpose The number for clinical systems of proton beam dedicated to the tumor irradiation therapy has been increasing in recent years. In particular, these new systems are likely added with an imaging unit of cone beam CT (CBCT) for image guidance to reduce patient positioning error. In these CBCT systems, the x-ray source to image-receptor distance (SID) of the CBCT unit mounted on the proton beam gantry may be extensively longer than that of CBCT units on linear accelerators. To characterize the scattering effect for these CBCT units with a long SID, we used Monte Carlo computer simulation to calculate the quantity of scatter-to-primary ratio (SPR). Materials and methods A general-purpose radiation transport code, PENELOPE, was used in our Monte Carlo computer simulation. Analytical uniform and non-uniform phantoms of different materials were used for SPR calculations, including adipose (density: 0.92 g/cm3, relative electron density: 0.49), water (1.00 g/cm3, 1), muscle (1.04 g/cm3, 1.043), and bone (1.85 g/cm3, 1.095). The phantom size was 50×50×20 cm3 in length, width, and height, respectively. The receiving area of flat-panel detector was 40×40 cm2. Cone angle was used to represent the maximum angle that the x-ray of cone beam can cover the entire receiving area of x-ray detector. Different SID geometries of 150, 220, and 300 cm with different cone beam x-ray energies were included in this work. Results In the phantom study with different materials, SPR decreased as either the x-ray energy increased, density of material decreased, or SID increased. The cone angle was 7.59° for 150 cm of SID; 5.19° for 220 cm of SID; 3.81° for 300 cm of SID. A negatively linear relationship was characterized between the cone angle and SID. Our Monte Carlo calculations showed that SPR decreased as the cone angle decreased. A positive correlation was shown between the SPR and cone angle.. Conclusions We used different CBCT systems to determine SPRs and SPR decreased for the CBCT unit with a longer SID..

    更新日期:2019-12-29
  • Compact shielding design for 740 GBq 241Am-Be neutron source transport container
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2019-12-29
    Pew Basu; R. Sarangapani; B. Venkatraman

    For transport and storage of neutron sources, shielding materials like polymers and multi layer shields are used. A compact shielding design for 740 GBq portable 241Am-Be neutron source transport container using Monte Carlo technique is presented. In the design, a polymer host material with lead and natural boron (NB) as fillers is chosen as the shielding medium. Monte Carlo simulation (MCS) is performed for optimizing the quantity of fillers in the polymer. The total dose rate (TDR) on the surface of the container due to neutrons and gamma rays emanating from source as well as polymer shield, is considered as the optimization criterion. MCS studies indicate that a polymer material with 5% of lead and 1% of NB as fillers is observed to give optimized composition of polymer (OCP). Statistical factorial design analysis (FDA) technique is employed for the first time in the shielding design to investigate the impact of fillers in the polymer. FDA studies reveal that the quantity of lead has more significant impact compared to NB in the polymer. MCS results are validated by carrying out shielding experiments with high density polyethylene (HDPE) and composite polymer (CP) based containers. The computed and experimental dose rates are observed to be within ±12%. A shielding container made of OCP for the transport of 740 GBq 241Am-Be source provides 25% reduction in volume as compared to HDPE and CP. The mass of the OCP container is lower by 18% and 26% compared to the containers made of HDPE and CP respectively. The surface dose rate of the OCP container adheres to the IAEA transport regulations.

    更新日期:2019-12-29
  • Numerical analysis of the irradiation and heating processes of thermoluminescent materials
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2019-12-28
    J.F. Benavente; J.M. Gómez-Ros; A.M. Romero

    The deconvolution of thermoluminescence (TL) glow curves into a sum of individual peaks described by First Order Kinetic (FOK) equations, implies that retrapping probability should be negligible compared with recombination during the readout (to avoid non-linearity) but not during irradiation (to allow the filling of the traps with the produced electron-hole pairs). In this contribution, some examples of TL glow curves simulated using a general model are discussed to show that FOK shape and deconvolution into individual glow peaks fitted by FOK equations is compatible with a non-negligible traps filling process during irradiation with the appropriate choice of kinetic parameters and probability factors.

    更新日期:2019-12-29
  • EPR studies of gamma irradiated poly(ether-urethane)s
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2019-12-28
    M. Walo; G. Przybytniak; J. Sadło

    In this work the effect of gamma irradiation on two commercial poly(ether-urethane)s of different hard segments, namely Pellethane and Tecoflex was investigated. Electron Paramagnetic Resonance (EPR) spectroscopy was used because it is the only technique appropriate for direct detection and identification of paramagnetic intermediates in the irradiated substances. Thermal annealing was applied to compare the relative stability of the detected radicals. It was found that the dominant component of EPR spectra is a doublet which was assigned to diphenylmethyl radical in Pellethane and dihexylmethyl radical in Tecoflex, formed by the abstraction of hydrogen atom from –CH2- group located between aromatic and cyclohexane rings, respectively. The other paramagnetic product present in the wide range of temperatures is alkyl radical –CH2-CH2• localized in both segments of polyurethanes, presumably formed by scission of C–O bond. The performed studies will allow to predict radiation susceptibility of polyurethanes designed in the future.

    更新日期:2019-12-29
  • XAFS investigation of Co/Zn based ZIFs after I2, Cl2 and Br2 adsorption
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2019-02-02
    Yulia S. Podkovyrina; Vera V. Butova; Elena A. Bulanova; Elena A. Reshetnikova; Alexander V. Soldatov; Carlo Lamberti

    This study investigates the impact of iodine, chlorine and bromine adsorption on the structure of bimetallic Co/Zn zeolitic imidazolate frameworks (ZIFs). The experimental Co and Zn K-edges XANES (X-ray Absorption Near Edge Structure) spectra of Zn0.5Co0.5C8H10N4 synthesized by microwave synthesis were measured before and after halogens treatment.

    更新日期:2019-12-27
  • Two-dimensional μXAFS analysis for accumulated uranium in kidneys of rats exposed to uranyl acetate
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2019-02-02
    Shino Homma-Takeda; Akihiro Uehara; Takanori Yoshida; Chiya Numako; Oki Sekizawa; Kiyofumi Nitta; Nobuaki Sato

    Kidneys are critical targets of uranium exposure, meaning that effective analytical methods for characterizing uranium accumulated in kidneys are required in toxicological studies of uranium. In this work, synchrotron radiation micro-X-ray fluorescence (SR-μXRF) imaging and two-dimensional μXAFS measurements were combined to analyze renal section specimens. By histochemical staining of the serial sections, the distribution of uranium chemical condition within the uranium-concentrated areas of the proximal tubules, which are toxic target sites of uranium, were obtained with 1 µm × 1 µm spatial resolution.

    更新日期:2019-12-27
  • Upgrade of SLRI BL8 beamline for XAFS spectroscopy in a photon energy range of 1–13 keV
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2019-02-02
    W. Klysubun; P. Tarawarakarn; N. Thamsanong; P. Amonpattaratkit; C. Cholsuk; S. Lapboonrueng; S. Chaichuay; W. Wongtepa

    Beamline 8 is a bending magnet beamline at Synchrotron Light Research Institute (SLRI) in Thailand and has been opened for synchrotron users to perform X-ray absorption fine structure (XAFS) spectroscopy since 2006. The beamline was originally equipped with a double crystal monochromator (DCM) using a vertical entrance slit in order to limit divergence of a white beam, thus optimizing photon energy resolution at a cost of photon flux. In 2016 the beamline was upgraded with a vertical collimating mirror to decrease beam divergence. The maximum photon flux is consequently increased to 3 × 1011 photons s−1 (100 mA)−1 at the phosphorus K-edge (2145.5 eV). This enhances beamline utilization for phosphorus speciation and analysis of local atomic structures in diluted samples (>50 mg/kg of phosphorus). Furthermore, the highest photon energy of the beamline has been extended from 10 keV to 13 keV, enabling several heavy elements such as lead to be studied while the lowest photon energy currently covers the sodium K-edge. To demonstrate improved XAFS performance, XAFS experiments were carried out on selected samples (NaCl, Na3PO4·12H2O, PbO, PbO4, PbCO3, PbS, soil, and historical paint); quality of the experimental spectra was evaluated in terms of signal-to-noise ratio and appearance of XAFS characteristic features.

    更新日期:2019-12-27
  • Polarization dependent X-ray absorption near-edge spectra of boron nitride nanotubes
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2019-01-25
    Peter Krüger; Yuya Maekawa; Adam Hitchcock; Carla Bittencourt

    We report polarization dependent, scanning transmission X-ray microscopy measurements of individual boron nitride nanotubes (BNNTs) and analyze them by means of first-principles calculations. X-ray absorption near-edge spectra of hexagonal boron-nitride (hBN) are calculated as a function of light polarization and layer stacking and best agreement with recent experimental data is obtained for the commonly assumed AA' stacking. Our experimental BNNT spectra show a pronounced polarization dependence which is qualitatively well reproduced in the calculations. We show that the BNNT has a mixed stacking sequence which may explain some of the differences seen between the hBN and BNNT line shapes.

    更新日期:2019-12-27
  • Ti K-edge XAFS investigation of lithium migration in lithium titanium oxide anode material under charge and discharge cycle
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2019-01-03
    Shinjiro Hayakawa; Atsunori Kaneda; Takuya Mori; Alvaro Munoz-Noval; Susumu Mineoi; Hirosuke Sumida

    Changes in Ti K-edge X-ray absorption fine structure (XAFS) spectra of lithium titanium oxide (LTO) during the charge discharge cycle of lithium ion battery were investigated by using a specially designed cell for in situ X-ray measurement. Thought LTO is famous for zero-strain lattice during the charge/discharge cycle, the significant spectral changes might be attributed to Li migration in the lattice. The experimental results were compared with the theoretical simulation, and the spectral changes were caused both by the slight changes in oxygen position parameter that affected titanium neighbors and Li migration.

    更新日期:2019-12-27
  • Treatment of disorder effects in X-ray absorption spectra beyond the conventional approach
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2018-12-30
    Alexei Kuzmin; Janis Timoshenko; Aleksandr Kalinko; Inga Jonane; Andris Anspoks

    The contribution of static and thermal disorder is one of the largest challenges for the accurate determination of the atomic structure from the extended X-ray absorption fine structure (EXAFS). Although there are a number of generally accepted approaches to solve this problem, which are widely used in the EXAFS data analysis, they often provide less accurate results when applied to outer coordination shells around the absorbing atom. In this case, the advanced techniques based on the molecular dynamics and reverse Monte Carlo simulations are known to be more appropriate: their strengths and weaknesses are reviewed here.

    更新日期:2019-12-27
  • Local structure of Cu(I) ions in the MOR zeolite: A DFT-assisted XAS study
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2018-12-28
    C. Buono; A. Martini; I.A. Pankin; D.K. Pappas; C. Negri; K. Kvande; K.A. Lomachenko; E. Borfecchia

    We combine in situ XAS and DFT to determine the local structure of Cu(I) ions in the Cu-exchanged mordenite (MOR) zeolite, one of the most promising materials for the selective oxidation of methane to methanol. Data analysis points to a quasi-linear coordination geometry in the MOR side pocket and suggests that ca. 20% of the Cu-ions exist as coupled di-copper(I) species, paving the way for more detailed structural refinements.

    更新日期:2019-12-27
  • EXAFS investigations of cobalt electrodeposition
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2018-12-28
    Dirk Lützenkirchen-Hecht; Damir Hamulić; Ralph Wagner; Ingrid Milošev

    X-ray absorption fine structure spectroscopy and scanning electron microscopy were used to study the atomic short range order structure, surface morphology and thickness of cobalt films electrodeposited from CoCl2 solutions on gold-coated Kapton. While the morphology on the electrodeposits strongly depends on the deposition time and thereby on the film thickness, the short range order structure deduced from the X-ray spectroscopic experiments suggests that pure metal films were formed, however with a slight relaxation of the Co-Co bond distances with increasing thickness, which may open new routes for the preparation of nanostructured Co-materials.

    更新日期:2019-12-27
  • Development of a high temperature diamond anvil cell for x ray absorption experiments under extreme conditions
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2018-12-28
    Yimin Mijiti; Angela Trapananti; Marco Minicucci; Matteo Ciambezi; Jean Coquet; Lucie Nataf; Francois Baudelet; Andrea Di Cicco

    X-ray absorption spectroscopy (XAS) is presently a powerful and established tool to investigate solid and liquid matter at high pressure and high temperature (HP-HT). HP-HT XAS experiments rely on high pressure technology whose continuous development has extended the achievable range up to 100 GPa and more. In high pressure devices, high temperature conditions are typically obtained by using internal and external resistive heaters or by laser heating. We have recently developed a novel design for an internally heated diamond anvil cell (DAC) allowing XAS measurements under controlled high temperature conditions (tested up to about 1300 K). The sample in the new device can be rapidly heated or cooled (seconds or less) so the cell is suitable for studying melting/crystallization dynamics when coupled with a time-resolved XAS setup (second and sub-second ranges). Here we describe the internally heated DAC device which has been realized and tested in experiments on pure selenium at the energy dispersive ODE beamline of Synchrotron SOLEIL. We also present results obtained in XAS experiments of elemental Se using a large volume Paris-Edinburgh press, as an example of the relevance of structural studies of matter under extreme conditions.

    更新日期:2019-12-27
  • MLFT approach with p-d hybridization for ab initio simulations of the pre-edge XANES
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2018-12-27
    E. Gorelov; A.A. Guda; M.A. Soldatov; S.A. Guda; D. Pashkov; A. Tanaka; S. Lafuerza; C. Lamberti; A.V. Soldatov

    Ab initio simulations of the pre-edge XAS spectra and other related resonance spectroscopies require taking into account 3d-4p hybridization on the 3d metal site. While the hybridization Hamiltonian could be parameterized on the basis of the symmetry of the system we introduce instead a set of 4p orbitals directly within the local Hamiltonian of the multiplet ligand-field approach. The maximally localized Wannier orbitals and 3d-4p hoppings are calculated then on the basis of band structure and total potential of the system. We show applicability of the method on the Fe3O4 structure with the Fe ions in different coordination and charge state in a single unit cell.

    更新日期:2019-12-27
  • Interpretation of the Cu K-edge EXAFS spectra of Cu3N using ab initio molecular dynamics
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2018-12-23
    Dmitry Bocharov; Andris Anspoks; Janis Timoshenko; Aleksandr Kalinko; Matthias Krack; Alexei Kuzmin

    Cubic copper nitride (Cu3N) has anti-perovskite structure, and its properties are strongly affected by anisotropic thermal vibrations of copper atoms. Ab initio molecular dynamics (AIMD) simulations were performed in the temperature range from 300 K to 700 K in order to probe the details of Cu3N lattice dynamics. The Cu K-edge extended X-ray absorption fine structure (EXAFS) spectrum of bulk Cu3N was used to validate AIMD simulations at 300 K. The AIMD results suggest strong anharmonicity of the Cu–N and Cu–Cu bonds, the rigidity of NCu6 octahedra and strong correlation in atomic motion within –N–Cu–N– atom chains as well as support anisotropy of copper thermal vibrations.

    更新日期:2019-12-27
  • X-ray Absorption Spectroscopy investigations of disordered matter
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2018-12-21
    Andrea Di Cicco

    X-ray Absorption Spectroscopy (XAS) is known to be an ideal technique for investigating matter lacking crystalline ordering. This work reports about present methods used for investigating disordered matter, discussing data-analysis and simulations strategies as well as several experimental techniques with applications. The current approach based on the comparison among multiple-scattering simulations associated with the n-body distribution functions and EXAFS (Extended X-ray Absorption Fine Structure) experimental data, including application of Reverse Monte Carlo methods, is discussed. Several studies of amorphous and liquid systems are presented, showing the potential of XAS in answering some important questions related to preferred local symmetries in liquid systems and presence of polymorphism in glasses and liquids. Experiments are presented discussing also the advances related to the performance of high-pressure and high-temperature experiments in disordered systems, highlighting the importance of combining XAS, x-ray diffraction and suitable diagnostics. XAS ability in measuring phase transitions and structure in undercooled metastable liquids is discussed. New possibilities offered by EXAFS measurements of light elements using inelastic scattering (x-ray Raman) are presented discussing the notable example of liquid water. Mention to new time-resolved applications at synchrotrons and free-electron lasers is also given.

    更新日期:2019-12-27
  • Controlled radiation-chemical synthesis of metal polymer nanocomposites in the films of interpolyelectrolyte complexes: Principles, prospects and implications
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2018-12-21
    Alexey A. Zezin; Dmitry I. Klimov; Elena A. Zezina; Kristina V. Mkrtchyan; Vladimir I. Feldman

    The radiation-chemical synthesis of metal nanoparticles embedded into polymer matrices is an effective tool for preparation of the composite materials with very useful functional properties. This paper presents a review of an original approach to a single-step production of such materials via the radiation-induced reduction of the interpolyelectrolyte complex (IPEC) films containing metal ions under heterogeneous conditions, including the most recent results, and analysis of the prospects of this approach and its implications. First, the properties of IPECs as precursors for nanocomposites are briefly considered. Particular impact is given to the mechanistic aspects and principles of control of the nanoparticle formation and assembling at different stages. A common procedure of the radiation-chemical synthesis of metal polymer nanocomposites in the IPEC matrices implies irradiation of swollen films in an aqueous – organic environment. The kinetics of ion reduction and formation of nanoparticles was monitored by EPR and optical spectroscopy, whereas the obtained nanocomposites were characterized by TEM and diffraction methods. Using IPEC matrices allows us to reveal different stages of formation of metal nanostructures over a wide range of absorbed doses. Furthermore, it is possible to manipulate the processes of nucleation and growth of nanoparticles using both physical and chemical factors. Different kinds of radiation (e-beams, γ- and X-rays) were used in the experiments. It was shown that the penetration depth, dose rate and total absorbed dose had strong effect on the effect on nanoparticle size and their spatial distribution. The most striking feature were found for the processes induced by X-ray radiation. Detailed studies of this particular case revealed a very interesting effect described as radiation-chemical contrast, which is manifested by local intensification of the radiation-induced processes in the vicinity of existing nanoparticles. In addition to metal nanoparticles of different transition and noble metals, it was possible to obtain the bimetallic nanostructures within the IPEC matrix. Such nanocomposites may be potentially used as optical and magnetic materials, sensors, bactericide and fungicide products. The possibility of variation of nanoparticle size and specific properties of the IPEC films is crucially important for particular applications.

    更新日期:2019-12-27
  • Development of in situ cell for simultaneous XAFS/XRD measurements at high temperatures
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2019-02-02
    Ken’ichi Kimijima; Toshiki Watanabe; Yasuo Takeichi; Yasuhiro Niwa; Masao Kimura

    A novel in situ cell was developed for simultaneous X-ray absorption fine structure and X-ray diffraction (XAFS/XRD) measurements at high temperatures up to 1773 K in a gas atmosphere such as air containing reactive oxygen, in which typical heat-resistant or environmental-barrier materials are used. This new cell can provide multimodal information by combining the following complementary information: (a) chemical states of a specific element and the short-range order (SRO) structure around the atoms, via XAFS measurements, and (b) the long-range order (LRO) crystal structure, via XRD. In situ observation of XAFS/XRD is essential to characterize materials under severe conditions, because reactions sometimes accompany metastable states, and quenching high-temperature states down to room temperature is quite difficult. The performance of the new cell was checked by in situ XAFS/XRD observation of the phase transition of TiO2 from anatase to rutile. Then, the developed technique was applied to a new type of environmental-barrier coating material, Yb2Si2O7, which was exposed to heat cycles up to 1773 K in air. The bulk structure maintained the chemical state of Yb3+ and the crystal structure of Yb2Si2O7, and no reaction phase was observed. The developed technique could provide fundamental information to understand the behaviors of materials used at high temperatures.

    更新日期:2019-12-27
  • 238U and 232Th isotopes in groundwater of Jordan: Geological influence, water chemistry, and health impact
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2019-12-25
    Ahmad Hussein Alomari; Muneer Aziz Saleh; Suhairul Hashim; Amal Alsayaheen; Ismail Abdeldin; Ahmad abukashabeh

    An extensive pioneer study was conducted to determine the activity concentration of 238U and 232Th in 94 groundwater samples to examine the influence of geological formations on the activity concentrations of 238U and 232Th and to investigate a relationship with the major chemical elements in groundwater. The study also aims to estimate the annual effective dose and health impact due to the intake of these radionuclides in the groundwater of Jordan. The mean activity concentrations of 238U and 232Th in groundwater were found to be 33 ± 5 mBq L−1 and 0.017 ± 0.002 mBq L−1, respectively. The highest mean of 238U and 232Th activity concentrations were found for lower Cretaceous geological formation, while Tertiary and Quaternary geological formations have the lowest mean 238U and 232Th activity concentration, respectively. The output of (ANOVA) and post hoc tests revealed the existence of significant influence of geological formations on 238U activity concentrations, while insignificant influence on 232Th activity concentrations was found in the groundwater of Jordan. The groundwater of Jordan was dominated by HCO3−1, Cl−1, Ca+2, and Na+1. The mean annual effective dose due to the ingestion of radionuclides 238U and 232Th in groundwater were found 1.143 μSv lower than recommended by WHO. The ingestion dose deduced is dominated by 238U of 99% where the average contribution from 232Th amounted to 1%. The results of the study will serve as a baseline data of 238U and 232Th activity concentrations in groundwater based on geological formations of Jordan.

    更新日期:2019-12-26
  • Temperature-induced valence transition in EuNi2(Si1–xGex)2 investigated by high-energy resolution fluorescence detection X-ray absorption spectroscopy
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2019-02-02
    Ryohei Shimokasa; Naomi Kawamura; Takayuki Matsumoto; Koki Kawakami; Taku Kawabata; Gen Isumi; Takayuki Uozumi; Akihiro Mitsuda; Hirofumi Wada; Masaichiro Mizumaki; Kojiro Mimura

    Electronic structures of the temperature-induced valence transition system EuNi2(Si1–xGex)2 with x = 0.70, 0.79, 0.82 have been investigated by means of high-energy resolution fluorescence detection X-ray absorption spectroscopy (HERFD-XAS). The HERFD-XAS spectra clearly change their intensities of Eu2+ and Eu3+ components which directly reflect the temperature-induced valence transition. For x = 0.70, gradual spectral change exhibits a continuous valence transition, while drastic changes for x = 0.79 and 0.82 indicate first-order valence transitions. High-energy resolution measurements made it possible to observe additional fine structures which are recognized more clearly below the transition temperature. Existence of these fine structures suggests that many-body effect plays an important role in the temperature-induced valence transition of this system. The variation of Eu mean valence estimated from the HERFD-XAS spectra for each x correlates with that of magnetic susceptibility.

    更新日期:2019-12-26
  • Radiation induced disordering in Cu3Au
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2019-12-24
    N.V. Proskurnina; V.I. Bobrovskii; B.N. Goshchitskii; A.Yu Volkov; V.I. Voronin

    In the work, a specially prepared powder of the model ordered Cu3Au alloy was used to investigate peculiarities of internal processes that take place in the ordered precipitates similarly to those occurring in austenitic reactor steel under irradiation with fast neutrons. It is shown that, unlike the thermal or deformation disordering, in the case of such impact, the dependence of the lattice parameter on the degree of long-range order presents a kink that testifies to the development under irradiation of competitive processes in the defect structure of the studied material.

    更新日期:2019-12-25
  • Alanine pellets comparison using EPR dosimetry in the frame of quality assurance for a Gamma Knife system in Romania
    Radiat. Phys. Chem. (IF 1.984) Pub Date : 2019-12-24
    C.S. Tuta; M.N. Amiot; L. Sommier; R.M. Ioan

    In the last decade, the use of alanine/Electronic Paramagnetic Resonance (EPR) system was extended to radiotherapy doses. In stereotactic radiosurgery, doses up to 70 Gy are delivered to the brain tumor preserving healthy tissues. This type of treatment is delivered using dedicated equipment, like Cyberknife or Gamma Knife. Alanine dosimeters are characterized by their small size (5 mm diameter) and by similarity with tissue. They are well adapted for this wide dose range for which the dosimeter response is linear, independent of dose rate and energy for the range around few MeV. Therefore Alanine/EPR system is a suitable method for accurate and stable dose measurements as passive dosimeters for narrow treatment beams, which makes it an excellent candidate for end to end testing of radiosurgery treatments using Gamma Knife. The present work describes the development of the alanine/EPR method at Horia Hulubei National Institute for Physics and Nuclear Engeneering (IFIN-HH) in Romania including the optimization of system parameters for the radiosurgery dose range in the frame of an IFIN-HH and the French national metrology institute Laboratoire National Henri Becquerel federated by the Laboratoire National de métrologie et d’Essais (LNE-LNHB) collaboration. Romanian alanine dose measurements capability is presented regarding a comparison of calibration curves between both National Laboratories using Bruker and Synergy Health alanine pellets.

    更新日期:2019-12-25
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