Gamma-ray Beam Research Articles

The use of gamma rays in studying the homogeneity of the alloy (AL-Co-Ni) reinforced with chromium oxide

This research deals with the preparation number of composite materials by casting the base alloy (Al-Co-Ni) by adding chromium oxide (Cr2O3) as reinforcement material, by weight ratios of (5, 10, 15 wt%) for the base alloy, with heat treatment of the prepared alloys. The basic alloys and composite materials were prepared by using solution casting method and manual mixing method to disperse reinforcement grains in the base alloy floor and with pressure of 5 ton in purpose of forming. The materials were melted and poured into molds and suddenly cooled in cold water, after the molten samples were frozen. The attenuation factor of gamma rays was founded the prepared alloys and their homogeneity was examined by shining a narrow beam of single energy gamma rays emitted from the radiating source (137Cs) with different energies (511, 662, 1173, 1284, 1333) keV respectively, gamma ray system (UCS-20) was being used which bounded to NaI(Tl) scintillation detector. The homogeneity of base alloy and composite material was determined by studying the contrast of gamma ray intensity, the linear attenuation coefficient at seven different locations at any samples and the percentage standard deviation. The results showed that the highest value of the linear attenuation coefficient was 0.252 mm-1 for sample [5%Cr2O3+Al+Co+Ni] with the energy (511 keV) and that the lowest value for the ratio of linear attenuation coefficient was 0.062 mm-1 at the energy of sample [15%Cr2O3+Al+Co+Ni] with the energy (1333 keV) indicating that the homogeneity of the sample [15%Cr2O3+Al+Co+Ni] at energy (1333 KeV).

Electromagnetic-Ray Absorption Using B2O3-PbO-Na2O Glass Mixtures as Radiation Protection Shields

In this work, Lead Borate glass system doped with sodium is prepared and fabricated using the melt-quenching technique. The glasses are prepared based on the empirical formula of xPbO, (80-x) B2O3, 20Na2O (where x=0, 10, 20, 30, 40, and 50). The densities of the samples are measured with the Archimedes method by using Benzene as an immersion liquid. The radiation shielding parameters of the prepared glass samples have been measured experimentally and calculated theoretically. The experimental mass attenuation coefficients are obtained by using a shielded NaI(Tl) detector at photon energies 511, 662, and 1173 keV of the radioactive sources 22Na, 137Cs, and 60Co respectively, where collimators of aperture diameter 3 mm are used to ensure that the detector absorbs a narrow beam of gamma rays. The calculated mass attenuation coefficients (µm), half-value layer (HVL), mean free path (MFP), effective atomic number (Zeff), effective electron density (Neff), atomic cross-section (σa), electron cross-section (σe) radiation protection efficiency (RPE) are performed theoretically by using WinXCom and Phy-X/PSD computer programs in the energy range from 1 keV to 1 GeV. The calculated parameters of the investigated glasses have been compared with the measured experimental values

Effects of Gamma and Electron Beam Irradiation on FBG and DFB-FL

This paper reports the comparative experimental study concerning the irradiation effects of gamma-ray and electron beam on fiber Bragg grating (FBG) and distributed feedback fiber laser (DFB-FL). The obvious reflection wavelength shifts are observed for FBGs and DFB-FLs without evident changes in reflectivity and bandwidth under the current experimental irradiation condition, up to 60 kGy gamma radiation and 100 kGy electron beam radiation, respectively. Especially for DFB-FLs, evident attenuation in output power is observed and the rising tendency of the attenuation under increasing irradiation dose is demonstrated as well. Thus, the DFB-FLs are more suitable for radiation detection as compared to passive FBGs.

Precision measurements on oxygen formation in stellar helium burning with gamma-ray beams and a Time Projection Chamber

The carbon/oxygen (C/O) ratio at the end of stellar helium burning is the single most important nuclear input to stellar evolution theory. However, it is not known with sufficient accuracy, due to large uncertainties in the cross-section for the fusion of helium with 12C to form 16O, denoted as 12C(α, γ)16O. Here we present results based on a method that is significantly different from the experimental efforts of the past four decades. With data measured inside one detector and with vanishingly small background, angular distributions of the 12C(α, γ)16O reaction were obtained by measuring the inverse 16O(γ, α)12C reaction with gamma-beams and a Time Projection Chamber (TPC) detector. We agree with current world data for the total reaction cross-section and further evidence the strength of our method with accurate angular distributions measured over the 1− resonance at Ecm ~ 2.4 MeV. Our technique promises to yield results that will surpass the quality of the currently available data.

Numerical analysis of the alanine response using Monte Carlo: Correlation with experimental results

International centers based on research reactors (ICERR) project supported by IAEA, offers training and research in the application of advanced nuclear reactor technology. In this context of the project, alanine dosimeters were irradiated under mixed neutron/gamma irradiation in the core of the MINERVE research reactor at the CEA Cadarache. The integrated dose of the alanine was measured by electron spin resonance spectrometry with reference to an absorbed dose in water from a 60Co gamma-ray beam. Neutron and gamma dose components were calculated using the MCNP code. The neutron dose and relative effectiveness (REn) for neutrons was evaluated using FLUKA code and Track Structure Theory (TST) formulations of alanine response towards irradiations with ions produced by neutron interactions with alanine. REn values were found to be between 0.516 and 0.538. The measured dose was compared to the calculation results. The best agreement between the alanine integral measurements and model predictions (0.4%) was obtained by using the Cucinotta alanine detector response model.

The Monte Carlo simulation approach to verification of the attenuation factors k for isotropic gamma-ray sources commonly used in industry, medicine and science

An important problem, which is currently overlooked in radiological protection, is the omission of the contribution from low-energy photons when estimating the dose received by persons working in conditions of exposure to ionizing radiation. As shown in this study, this contribution cannot be omitted because it determines the dose in the workplace when an isotropic source of gamma rays (uncollimated beams) and thick shields are used. The omission of the contribution from low-energy photons causes that the gamma-ray attenuation factors, often marked in radiological protection with the letter k, as well as the transmission curves for isotropic gamma-ray beams resemble those for collimated beams without the typical features of uncollimated beams. This causes the estimated doses to be significantly underestimated. In this work the gamma-ray attenuation factors k were determined by Monte Carlo simulations for basic shielding materials, for commonly used isotropic gamma-ray sources. These factors are the basic parameters used to calculate the gamma-ray dose that a person who performs professional activities with gamma rays can receive. Accurate calculation of this dose translates into work safety. Justification for this research is the necessity to apply the exact k-factor values in radiological protection in Poland where doses at workplaces are calculated according to the procedure given in Gostkowska's book based on the old Polish norm (1987). The ground of this norm are transmission curves from NCRP Report 49 (1976) based on data obtained in the 1930's, 40's and 50's, unsuitable for isotropic sources. Although the obtained results refer to the Polish standard, the world's norms based on the NCRP Report 49 also need innovation, because the subsequent versions of this report published in 1991, 1994 and 1998 as well as the NCRP Report No. 151 considered as the new face of the NCRP Report No. 49 do not make the required correction. This work meets these requirements by using the Monte Carlo simulation method based on the GEANT4 code.

Thickness determination of material plates by gamma-ray transmission technique using calibration curves constructed from Monte Carlo simulation

This paper presents a new approach for determining the thickness of material plates by gamma-ray transmission technique using calibration curves obtained from simulated spectra through the Monte Carlo algorithm. The narrow transmitted gamma-ray beam from a collimated source of 137Cs (with the energy of 661.7 keV) for different thicknesses of the metal plates (aluminum, copper, and steel) was recorded by a NaI(Tl) detector. Besides, the Monte Carlo simulations of radiation transport in a model with the same geometry, source, and detector characteristics as in the real experiment were performed to obtain the transmission spectra. A good agreement between the experimental and simulated spectra was observed. The linear calibration curves of the value of ln(R) versus the thickness of material plates were constructed using Monte Carlo simulated data (R is the ratio of the area under a transmitted peak for measurement with sample relative to that for measurement without sample). The unknown thickness of a sample was determined by substituting the experimental value of ln(R) into the linear calibration curve corresponding to such sample. Besides, the range of measurable thickness with the desired accuracy was estimated for each material based on simulated data. The obtained results showed excellent quantitative values even without using any standard plate with known thickness for the calibration.

Deconvolution of thermoluminescence curves and its implications: The case of CaAl2O4:Sm3+

Deconvolution of thermoluminescence(TL) curve has evolved as a subject of its own merit and has attained a mature state. Unfortunately, even with the availability of multiple methods id analysis and numerous deconvolution software, the pitfalls are many. This paper presents a comprehensive deconvolution of TL curves of a typical phosphor, namely CaAl2O4:Sm3+ and once for all settle the prevailing myths on evaluation of intrinsic trap parameters (Activation energy, E and frequency factor, s) for crystalline phosphors. The TL curves are that of four different kinds of excitation (UV, x-ray gamma-ray and electron beam) as well as ten doses of gamma-ray excitation(0.5–50 Gy). Our results show multiple discrete trap levels within the bandgap of the CaAl2O4 lattice that are a potential source for developing novel afterglow phosphors and thermoluminescence dosimeters. Finally, we provide some simple guidelines to overcome the misconceptions that have been perpetually being propagated in the literature of TL and its applications.

Production of 120 MeV Gamma-ray Beams at Duke FEL and HIGS Facility

Production of 120 MeV Gamma-ray Beams at Duke FEL and HIGS Facility

Organic glass scintillator bars with dual-ended readout

Organic glass scintillator (OGS) bars (6 × 6 × 50 mm3) were melt-cast and characterized with dual-ended readout by silicon photomultiplier arrays. The results were compared to trans-stilbene bars of the same size. Energy resolution was measured via a 137Cs Compton-coincidence experiment. Time resolution was determined via a 22Na coincidence-timing experiment. Depth-of-interaction resolution was measured by moving a gamma-ray fan beam along the major axis of the bars. Pulse shape discrimination capability and neutron light output were determined via a time-of-flight measurement of a 252Cf source. The OGS bars exhibited better energy resolution at 478 keV (10.3±0.5% vs. 11.2±0.5%), better time resolution from 200–341 keVee (270ps vs. 340ps FWHM), slightly poorer depth-of-interaction resolution, poorer PSD performance, and higher neutron light output than the stilbene bars. The low cost, ease of manufacturing, brightness, and excellent time resolution make OGS a strong candidate for use in compact radiation imaging systems.

A comparative study on applicability and efficiency of machine learning algorithms for modeling gamma-ray shielding behaviors

The mass attenuation coefficient is the primary physical parameter to model narrow beam gamma-ray attenuation. A new machine learning based approach is proposed to model gamma-ray shielding behavior of composites alternative to theoretical calculations. Two fuzzy logic algorithms and a neural network algorithm were trained and tested with different mixture ratios of vanadium slag/epoxy resin/antimony in the 0.05 MeV–2 MeV energy range. Two of the algorithms showed excellent agreement with testing data after optimizing adjustable parameters, with root mean squared error (RMSE) values down to 0.0001. Those results are remarkable because mass attenuation coefficients are often presented with four significant figures. Different training data sizes were tried to determine the least number of data points required to train sufficient models. Data set size more than 1000 is seen to be required to model in above 0.05 MeV energy. Below this energy, more data points with finer energy resolution might be required. Neuro-fuzzy models were three times faster to train than neural network models, while neural network models depicted low RMSE. Fuzzy logic algorithms are overlooked in complex function approximation, yet grid partitioned fuzzy algorithms showed excellent calculation efficiency and good convergence in predicting mass attenuation coefficient.

Collimator system of SLEGS beamline at Shanghai Light Source

Shanghai laser electron gamma source (SLEGS) is an energy-variable gamma-ray source developed based on the inverse Compton scattering of 10640 nm photons from a 100 W CO2 laser on 3.5 GeV electrons from the Shanghai Light Source. It produces gamma-rays in the energy range of 0.4–21.7 MeV with a flux of 105–107 photons/s. A collimator system was designed to produce quasimonochromatic gamma-ray beams with a best possible bandwidth of 1.1%–4.4% and filter out the substandard gamma-rays. The collimator system composed of coarse and fine collimators, constitutes a critical component of the SLEGS. By Geant4 simulations, we show that the collimator system is effective in tuning beam bandwidths and regular dodecagonal beam spots at the target position.

Effect of Non-thermal Pasteurization on Minced Chicken Meat Based Pet Food and Its Quality Attributes through Gamma Ray and Electron Beam Irradiation

Effect of Non-thermal Pasteurization on Minced Chicken Meat Based Pet Food and Its Quality Attributes through Gamma Ray and Electron Beam Irradiation

Resonance photoproduction of pionic atoms at the proposed Gamma Factory

We present a possibility of direct resonance production of pionic atoms (Coulomb bound states of a negative pion and a nucleus) with a rate of up to $\sim10^{10}$ per second using the gamma-ray beams from the Gamma Factory.

Three-Dimensional Nondestructive Isotope-Selective Tomographic Imaging of 208Pb Distribution via Nuclear Resonance Fluorescence

Combining the nuclear resonance fluorescence (NRF) transmission method with computed tomography (CT) can be a novel method for imaging the isotope distributions, which is indispensable in nuclear engineering. We performed an experiment to reconstruct a three-dimensional NRF-CT image with isotope selectivity of enriched lead isotope rods (208Pb) together with a set of different rods, including another enriched isotope (206Pb), iron, and aluminum rods, inserted into a cylindrical aluminum holder. Using a laser Compton scattering (LCS) gamma ray beam with a 5.528 MeV maximum energy, 2 mm beam size, and 10 photon·s−1·eV−1 flux density, which is available at the BL1U beamline in the ultraviolet synchrotron orbital radiation-III (UVSOR-III) synchrotron radiation facility at the Institute of Molecular Science at the National Institutes of Natural Sciences in Japan, and we excited the Jπ = 1− NRF level at 5.512 MeV in 208Pb. An isotope-selective three-dimensional NRF-CT image of the 208Pb isotope distribution was experimentally obtained for the first time with a pixel resolution of 4 mm in the horizontal plane.

Simultaneous attenuation of gamma ray and neutrons in single layer concrete shield

The ability to create various compounds has made concrete one of the most suitable materials for constructing radiation shields. In this investigation, hematite and magnetite aggregates were used to replace ordinary aggregate, separately and completely in two stages. Boron carbide was also substituting cement at percentages of 2.5, 5, and 10 by mass. The density test, gamma irradiation with Co 60 and neutron irradiation with Am-Be 241 were performed. According to the results, the replacement of ordinary aggregates with hematite aggregates in concrete, improved the linear attenuation coefficient and macroscopic cross section by 17% and 73%, respectively. These parameters increased by 37% and 105%, respectively, by the use of magnetite aggregates. Moreover, with the addition of a maximum of 10% boron carbide to the concrete, the macroscopic cross-section increased by 120%, however, the linear attenuation coefficient decreased by between 5% and 8%. This means that it is possible to have a suitable attenuation of gamma ray and neutron beams in a single layer of concrete shield simultaneously. In addition, the results of the tests and Monte Carlo simulation were found to have good consistency.

Measurement of void fraction in pipes by nuclear transmission based techniques

In this study, the application of nuclear transmission based techniques to the measurement of two-phase flow was evaluated and the experiment setup was described. Because neutrons are appreciably affected by interaction with hydrogen atoms, techniques based on transmission of thermal and fast neutron are particularly suitable for use with water or any other hydrogenous fluids. Based on the effective of water for gamma-rays attenuation on mass basis, transmission technique based on measuring of total gamma-rays has been examined. The beams of fast neutrons, thermal neutrons and gamma-rays emitted from 252Cf neutron source of strength 1.3 × 107 n/s were used. Void fraction is measured for steady-flow regimes in a horizontal air–water flow. Results are evaluated and the strength and limitations for each technique are given and discussed.

Assessment of calibration coefficient ND, W in terms of absorbed dose-to-water of some ionization chambers

The absorbed dose-to-water calibration coefficients ND,W of some ionization chambers were determined in terms of the secondary standard chambers in 60Co gamma-ray beam based on the TRS-398 protocol. The reference absorbed dose-to-water Dw were measured using secondary standard ionization chambers of model NE 2781#0537 (0.60 cm3 volume) and NE 2771#1205 (0.69 cm3 volume) which are traceable to the dosimetry laboratory of the International Atomic Energy Agency (IAEA). This study mainly focuses on the comparative assessment of the determined ND,W coefficients of twenty cylindrical ionization chambers from various user groups. The determined ND,W coefficients were compared with the manufacturer provided ND,W coefficients. The observed percentage of deviation between the measured and the manufacturer’s ND,W coefficients among all the chambers were found to be in the range of 0.019% and -2.263% as the least and highest, respectively. The observed percentage of deviations for studied chambers were found within the IAEA’s acceptance limit of 1.5% with an exception for three chambers. This observed discrepancy with the IAEA’s acceptance limit for the three chambers out of the twenty chambers, indicates the calibration necessity before using chambers in routine reference dosimetry. In ND,W measurement, the uncertainty Uc is reported with the coverage factor k=1 that providing a level of confidence of approximately 68%.

Selective Isotope CT Imaging Based on Nuclear Resonance Fluorescence Transmission Method

The isotope selectivity of computed tomography (CT) imaging based on nuclear resonance fluorescence (NRF) transmission method using a quasi-monochromatic laser Compton scattering (LCS) gamma-ray beam in the MeV region was demonstrated at the Ultra Violet Synchrotron Orbital Radiation-III (UVSOR-III) Synchrotron Radiation Facility (Institute of Molecular Science, National Institute of Natural Science) for two enriched lead isotope rods ( <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">206</sup> Pb and <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">208</sup> Pb) implanted in an aluminum cylinder. Since these two rods show the same gamma-ray attenuation in atomic processes, it is impossible to differentiate between them using a standard Gamma-CT technique based on atomic attenuation of gamma rays. The LCS gamma-ray beam had a maximum energy of 5.528 MeV and an intensity of approximately 5.5 photons/s/eV at the resonance energy (J <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">π</sup> = 1 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sup> at 5.512 MeV in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">208</sup> Pb). A lead collimator with a hole diameter of 1 mm was used to define the size of the LCS gamma-ray beam at the CT target. The CT image of the <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">208</sup> Pb rod was selectively obtained with a 2-mm pixel size resolution, which was determined by the horizontal step size of the CT stage.

Conceptual Design of a High-flux Multi-GeV Gamma-ray Spectrometer

We present here a novel scheme for the high-resolution spectrometry of high-flux gamma-ray beams with energies per photon in the multi-GeV range. The spectrometer relies on the conversion of the gamma-ray photons into electron-positron pairs in a solid foil with high atomic number. The measured electron and positron spectra are then used to reconstruct the spectrum of the gamma-ray beam. The performance of the spectrometer has been numerically tested against the predicted photon spectra expected from non-linear Compton scattering in the proposed LUXE experiment, showing high fidelity in identifying distinctive features such as Compton edges and non-linearities.