Gamma-ray Intensities Research Articles

A scintillator attenuation spectrometer for intense gamma-rays.

A new type of compact high-resolution high-sensitivity gamma-ray spectrometer for short-pulse intense gamma-rays (250keV to 50MeV) has been developed by combining the principles of scintillators and attenuation spectrometers. The first prototype of this scintillator attenuation spectrometer (SAS) was tested successfully in Trident laser experiments at LANL. Later versions have been used extensively in the Texas Petawatt laser experiments in Austin, TX, and more recently in OMEGA-EP laser experiments at LLE, Rochester, NY. The SAS is particularly useful for high-repetition-rate laser applications. Here, we give a concise description of the design principles, capabilities, and sample preliminary results of the SAS.

Valorization of hazardous glass wastes via geopolymer production utilized in gamma ray shielding applications: A comparative study with Portland cement

The main goal of this study is to fabricate low cost green binding material produced from the safe recycling of soda-lime glass waste (SLG), hazardous lead-rich glass waste (LRG) and slag (GGBFS). A comparative study was performed between OPC paste and five geopolymer pastes; alkali-activated slag (AAS), AAS-30%SLG, AAS-25%SLG-5%LRG, AAS-20%SLG-10%LRG and AAS-15%SLG-15%LRG. Low concentration of NaOH solution was used to fabricate geopolymer pastes. OPC paste has been cured under tap water while geopolymer pastes treated under high humidity up to 28 days. The compressive strength for six hardened pastes was measured at different curing times (1, 3, 14 and 28 days). Moreover, chemically combined water %, bulk density, total porosity % and water absorption % were measured at 28 days of curing. Linear attenuation coefficient (μ), half-value layer (HVL), mean free path (MFP), and transmission fraction (TF) were also determined as gamma ray attenuation parameters. Various techniques have been utilized to identify the formed hydrates/gels such as XRD, TGA/DTGA and SEM/EDX. It was found that, the geopolymer pastes, prepared at room temperature, have lower compression strength than the corresponding OPC pastes at all ages of curing. However; they have acceptable attenuation capacity, as compared with OPC, at different intensities of gamma rays (0.66, 1.17 and 1.33 MeV). It was found that, the linear attenuation coefficients of AAS and AAS-20%SLG-10% LRG hardened pastes increased by 10.7 and 9.6%, respectively than the corresponding value of OPC paste at 0.66 MeV. To achieve the same mechanical efficacy, all geopolymer pastes after 28-day of curing were thermally activated by heating up to 250 °C. From economic and environmental points of view, the production of these geopolymers minimized the energy consumption and CO2 emissions by 60 and 90%, respectively as compared with OPC.

A Study on the Radiation Shielding and Absorption Effects of Nonwoven Composites by Monte-Carlo Simulation Analysis

The purpose of this study was to investigate the radiation attenuation effect due to reflection and refraction that occurs when radiation passes through the composite material through simulation. The gamma-ray shielding ability of composites with different structures, such as layered composite, fibrous composite, and particle-added composites, was compared. For the layered composites, regardless of the thickness, the gamma-ray attenuation effect due to the structure of the layered composite could not be seen. The simulated attenuation coefficient was found to be different than the theoretical value, which increased with the content of inorganic materials. Assuming that the cesium ions absorbed on the nonwoven fabric are located in the center of the nonwoven fabric and the radioactive material absorbent is used in an appropriate amount, it is expected that more than 50% of gamma rays emitted from radioactive cesium can be shielded. If the nonwoven composites have such a shielding ability, it is expected that after adsorbing 137Cs, the intensity of gamma rays due to the adsorbed radioactive cesium can be partially attenuated, thereby contributing to radioactive waste treatment.

Identifying the principal factors controlling uranium enrichment: Semi-quantitative mineralogy and geochemistry of the sandstone-type Qianjiadian uranium deposit, northeast China

The Qianjiadian deposit is the first late Mesozoic–Cenozoic sandstone-type uranium deposit discovered in the Songliao Basin, northeast China. It remains uncertain whether high-temperature hydrothermal fluid or low-temperature groundwater dominated the mineralization process that led to uranium enrichment in this deposit. We investigated the gamma ray intensity and semi-quantitative mineralogical and geochemical characteristics of drill cores from the Qianjiadian deposit. A total of 60 gamma ray anomalies were identified; most of these anomalies are associated with negative Fe2O3 and Fe3+/Fe2+ anomalies, four are associated with positive total organic carbon (TOC) anomalies, and none are associated with positive carbonate (calcite + dolomite) anomalies. The absence of positive carbonate anomalies, together with low kaolinite crystallinities, rules out the influence of high-temperature fluid on uranium enrichment. The dominant negative Fe2O3 and Fe3+/Fe2+ anomalies and the occurrence of pyrite in thin section and gray-red sandstone and native sulfur in some U-rich drill cores indicate that redox reactions in low-temperature groundwater may have been the principal control on uranium enrichment. In addition, two gamma ray anomalies are associated with positive TOC, Fe2O3, and Fe3+/Fe2+ anomalies and another two are associated only with positive kaolinite anomalies, suggesting that carbonaceous debris and kaolinite could also cause limited uranium enrichment.

Simulation of cobalt-60 production in research reactors using OpenMC Monte Carlo code

Abstract Cobalt-60 is an artificial radioisotope with a wide range of applications in many industries for its high intensity gamma-rays and longer half-life. It may be produced in research reactors from the stable isotope cobalt-59 by neutron activation when a fission neutron is absorbed in the Co-59 nucleus. The ETRR-2 research reactor is designed with an in-core neutron flux trap that accommodates space for placement of an irradiation box, which makes it suitable for the production of radioisotopes as an in-core fixed facility. This simulation study compares the production yield of Co-60 for different Co-59 pencil configurations within the irradiation box inside the in-core neutron flux trap. IAEA reference for Co-60 specifications was used to set the comparison criteria for generating different configurations. Reactor geometry and calculations were carried out using OpenMC Monte Carlo code to obtain the effective multiplication factor Keff, the flux distribution, and the production yield of Co-60 with respect to time. Results show that the ETTR-2 is capable of producing Co-60 with a specific activity of 83.89 Ci g−1 in 263 ± 14 days following the placement of eight Co-59 pencils with 0.77 cm diameter, 32 cm in height, and 74.506 g each. It was also shown that a higher production rate may be achieved by decreasing the diameter of the pencils and increasing their number while Co-59 mass is kept constant.

Gamma-ray generation optimized by long and short pulses jointly driving double-layer target

In order to verify that the large-scale low-density plasma has a significant gain effect on the quality of the ultra-hot electron beam in ultra-strong ultra-short pulse laser interactions with matter, on the Shenguang-II upgraded laser facility, we carry out an experimental study on the optimization of relativistic electron beams that combine long and short pulse lasers to generate large-scale low-density pre-plasma. A nanosecond laser is used to ablate the thin hydrocarbon film. After a period of time, a large-scale low-density plasma is formed. The second picosecond short pulse laser then interacts with the formed low-density plasma, and accelerates the electrons to the relativity magnitude. Through the comparative analysis between different experimental conditions in the experiment, it is found that the existence of large-scale low-density plasma significantly increases the intensity of the relativistic electron beam along the laser propagation direction. In the comparative test of three shooting methods (long and short pulse combined driving double-layer target, short pulse driving double-layer target, short pulse driving single-layer target), we find that the energy bands above 1 MeV can be produced by the long pulse and the short pulse jointly driving double-layer target. The gamma-ray intensity is nearly twice that of the other two schemes. In addition, we also find in the experiment that when the time interval between nanosecond-picosecond pulses changes, the pre-plasma electron density and density scale length of the CH film irradiated by the nanosecond laser will be different. When the time interval is 0 ns, the expansion of the plasma is still insufficient, and the density distribution of the pre-plasma is steep. Part of the picosecond laser energy will be reflected at the critical density surface. Insufficient absorption of picosecond laser energy reduces the generation of relativistic electrons.When the time interval is 1 ns, the plasma state is more appropriate. The picosecond laser will form a self-focusing plasma channel in the plasma, thereby efficiently depositing energy, breaking through the energy limit of ponderomotive force acceleration, and obtaining more higher energy relativistic electrons. When the time interval is longer, such as 1.5 ns or more, the plasma can be fully expanded, the electron density becoming too low. Most of the picosecond laser will pass through the pre-plasma, affecting energy deposition and failing to generate more relativistic electrons.

Multi-Energy Gamma-Ray Attenuations for Non-Destructive Detection of Hazardous Materials

We present a non-destructive method (NDM) to identify minute quantities of high atomic number (Z) elements in containers such as passenger baggage, goods carrying transport trucks, and environmental samples. This method relies on the fact that photon attenuation varies with its energy and properties of the absorbing medium. Low-energy gamma-ray intensity loss is sensitive to the atomic number of the absorbing medium, while that of higher-energies vary with the density of the medium. To verify the usefulness of this feature for NDM, we carried out simultaneous measurements of intensities of multiple gamma rays of energies 81 to 1408 keV emitted by sources 133Ba (half-life = 10.55 y) and 152Eu (half-life = 13.52 y). By this arrangement, we could detect minute quantities of lead and copper in a bulk medium from energy dependent gamma-ray attenuations. It seems that this method will offer a reliable, low-cost, low-maintenance alternative to X-ray or accelerator-based techniques for the NDM of high-Z materials such as mercury, lead, uranium, and transuranic elements etc.

Refinement of optical/structural features and neutron/gamma-ray protecting capability of P2O5–Li2O–BaO phosphate glass system by adding Bi2O3

In this work, a new phosphate glass system with the nominal compositions 65P2O5 +10Li2O +(25-x)BaO + xBi2O3 was fabricated by using the conventional solid-state technique. Phosphate glasses were evaluated for their suitability in optical and radiation shielding applications. The amorphous nature of manufactured glasses was proved by utilizing an X-ray diffraction pattern. The density of glass samples was enhanced with rising Bi2O3 substitution ratio. UV–Vis absorption spectra were measured based on the concentration of Bi2O3 in PLBB glasses, optical energy band gap Eg for indirect and direct transitions were decreased from 3.43, 4.25 to 3.15, 3.95 eV with enhancing Bi2O3 substitution ratio respectively while urbach energy Eu was increased from 0.632 to 0.661 eV. The single oscillator energy (Eo) was found to decrease with increasing Bi2O3 however the average oscillator wavelength (λo) was increased. The Gamma-ray attenuation features of PLBB glasses were obtained via EpiXS program and MCNPX simulation codes. Mass attenuation coefficients (MAC) for PLBB0 and PLBB25 glasses were determined in the range of 14.995–0.0247 cm2/g and 43.912–0.0335 cm2/g, respectively. Outcomes obtained from MAC values and other photon shielding parameters such as MFP, HVL, Zeff, Nel, and EBF revealed that the replacement of Bi2O3 with BaO improves the capacity of PLBB glasses to reduce the intensity of gamma-rays. Furthermore, the macroscopic neutron cross section of PLBB25 glass with 25% Bi2O3 substitution is 0.133 cm−1 while it is 0.113 cm−1 for PLBB0 glass. The increase of Bi2O3 addition to the new phosphate glass system has remarkably improved both optical and nuclear radiation protecting properties.

Uluslararası Doğrusal Çarpıştırıcı Operasyonu için Gamma Işını Serbest Elektron Lazeri Salındırıcı Tasarımının Kısa Bir Gözden Geçirilmesi

In this paper, we make a review of the International Linear Collider design with regard to its positron source. The properties of the intense gamma ray undulator radiation of the dedicated free electron laser is reviewed. We review the discussions about the proposed undulator parameters to obtain an efficient operation of the positron source. The proposals and experimental results about the optimization of the positron beam yield, undulator properties, the injected electron beam energy, polarisation qualities of the produced gamma rays and the positron beam, are discussed. Alternative ideas and suggestions about the use of excess gamma rays in other nuclear energy experiments or the use of positrons in the undulator instead of electrons are also mentioned.

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).

Model independent approach to photodisintegration of 7 Li at the range of energies of interest to BBN

One of the elements that was synthesized primordially in the standard Big Bang Nucleosynthesis is lithium. Lithium, being fragile gets easily destroyed at relatively low temperatures in the mixing process between stellar surface and hot internal layers. So that, at the end of the stellar lifetime the lithium content is believed to be depleted. Series of experimental measurements on lithium isotopes were carried out at High Intensity Gamma Ray Source (HIGS) at Duke Free Electron Laser Laboratory. More recently experiments [1]-[2] were performed, to measure the differential cross section of the photo-neutron reaction channel in photodisintegration of 7 Li, where the progeny nuclei is in the ground state as well as in excited states. The purpose of present contribution is to study the reaction channel 7 Li + γ → 6 Li + n using linearly polarized photons. The model independent irreducible tensor formalism [3]-[5] will be used to study the differential cross section of the reaction. We study the angular dependence of differential cross section by expressing differential cross section in terms of legendre polynomials. In view of the several theoretical and ongoing experimental studies, a detailed theoretical study of the spin structure of the amplitudes in 7 Li + γ → 6 Li + n and their expansion in terms of ’electric’ and ‘magnetic’ amplitudes is needed to analyze the measurements of spin observables as well as differential cross section, which leads to a better understanding of the problem at astrophysical energies

Branching ratios for the three most intense gamma rays in the decay of 47Ca

A sample of 47Ca produced through isotope harvesting at the National Superconducting Cyclotron Laboratory was used to measure branching ratios of 7.17(5)%, 7.11(5)%, and 75.0(5)% for the 489.2, 807.9, and 1297.1 keV characteristic gamma rays, respectively. Based on these updated branching ratios, the ground state to ground state 47Ca to 47Sc beta decay branching ratio has been indirectly measured as 17.7(5)% and the ground state to 1297.1 keV excited state as 82.2(5)%. These values represent a greatly increased precision for all five branching ratios compared to the currently accepted values (Burrows, 2007). The measurements presented here were made relative to the ingrown 47Sc daughter in a47Ca sample and the well-established 159.4 keV gamma-ray branching ratio and the half-life for the decay of 47Sc (Reher et al., 1986; Meadows and Mode, 1968; Mommsen et al., 1980). These measurements were supported by verifying that the half-lives measured from characteristic gamma-ray peaks over multiple spectra for both 47Ca and 47Sc were consistent with previously reported values. Additionally, the half-lives of both 47Ca and 47Sc were independently measured with Liquid Scintillation Counting to reverify the previously reported values used in this study to find updated gamma-ray branching ratio values.

Changes of gross gamma-ray intensity in a submarine spring system due to a distant earthquake event on 30th of March 2019 at Itea, Greece

Changes of gross gamma-ray intensity in a submarine spring system due to a distant earthquake event on 30th of March 2019 at Itea, Greece

High-energy gamma-rays and neutrons observed in very impulsive solar flare on 2012 June 3

AbstractAn impulsive solar flare was observed on 2012 June 3 by the Geostationary Operational Environment Satellite. In this flare, a salient feature was recognized whereby high-energy ions were accelerated to a few GeV within one minute. Associated with this flare, high-energy gamma-rays as well as high-energy neutrons were detected by the Space Environment Data Acquisition equipment onboard the International Space Station. A remarkable feature found of this event was an exceedingly high n$/$γ-ratio observed between the intensities of high-energy neutrons and gamma-rays. To understand a high n$/$γ-ratio of about 600, the interaction processes between the accelerated ions and ambient solar atmosphere were simulated for various test cases, taking into account the magnetic field of the photosphere. The simulation was extended by using the GEANT4 code and it was shown that the observed results could be reproduced under certain conditions selected for the actual interaction process. The results suggest that helium and C, N, and O ions were predominantly accelerated in this flare, and that high-energy gamma-rays and neutrons were produced by interactions between the accelerated ions and the ambient gas. As a result, a high n$/$γ-ratio was produced.

Stochastic acceleration of electrons by chaotic electrostatic field in thundercloud

We investigate stochastic acceleration of electrons moving through a chaotic electrostatic field (CEF). Acceleration mechanism is based on irregular scattering of electrons experiencing random pulses in the CEF. Despite the fact that the pulses have random values and orientations, a specific stochastic acceleration of electrons occurs. This acceleration mechanism is analogous to the well-known second-order Fermi acceleration. It can act in various media, where random inhomogeneities create a chaotically distributed electric field. In this paper the phenomenon is investigated specifically for thunderclouds, where the CEF is formed by randomly distributed charged hydrometeors and ions. We show that acceleration process is threshold: the electron flux is accelerated, if the mean CEF value exceeds a certain threshold value, and decelerated otherwise. Accelerated electrons can form the avalanche of relativistic electrons, producing intense bremstrahlung gamma ray radiation. Proposed stochastic acceleration of electrons in the CEF complements second-order Fermi acceleration, expanding its application to static chaotic fields.

Organic glass scintillator (OGS) property comparisons to Stilbene, EJ-276 and BC-404

A new fast organic glass scintillator (OGS), recently developed at Sandia National Laboratories, has been proposed as a lower cost alternative to stilbene for detecting fast neutrons in intense gamma-ray fields, where excellent pulse-shape analysis (PSA) is required. In this paper we evaluate this proposition by measuring OGS’s scintillation properties and comparing them to three well known materials: stilbene, EJ-276, and BC-404. The measured properties were single photon light emission curves, coincidence time resolution (CTR), luminosity (photons/MeV), and figure of merit (FOM) for neutron/gamma PSA. From the light emission curves, we found that OGS has an 0.82 ns 10–90 risetime, close to EJ-276’s value of 0.81 ns and 25% faster than BC-404 and stilbene’s values at 0.96 and 1.01 ns, respectively. CTR values were measured from 75 to 325 keV, with OGS approaching 200 ps at 325 keV, compared to 250, 325 and 325 ps for BC-404, stilbene, and EJ-276, respectively. OGS had the highest luminosity, at 15,821 photons/MeV, compared to stilbene (13,054), BC-404 (8410), and EJ-276 (5522). For PSA, we studied neutron and gamma-ray pulse shapes as a function of energy and investigated various PSA algorithms, finding a properly selected tail/peak ratio to be generally best. OGS PSA FOM values were found to be twice as large as for EJ-276 and almost as good as stilbene’s – reaching 2.9, 1.5, and 3.2 at 1 MeVee respectively. Since OGS can be produced by lower cost casting techniques, this work supports further OGS development efforts.

Evaluation of gamma-ray transmission through rectangular collimator slits for application in nuclear fuel spectrometry

Gamma-ray spectrometry is widely applied in several science fields, and in particular in non-destructive gamma scanning and gamma emission tomography of irradiated nuclear fuel. Often, a collimator is used in the experimental setup, to selectively interrogate a region of interest in the fuel. For the optimization of instrument design, as well as for planning measurement campaigns, predictive models for the transmitted gamma-ray intensity through the collimator are needed. Commonly, Monte Carlo radiation transport tools are used for accurate prediction of gamma-ray transport, however, the long computation time requirements when used in low-efficiency experimental setups present challenges.In this work, the full-energy peak intensity transmitted through a rectangular collimator slit was examined. A uniform planar surface source emitting isotropically was considered, and the rate of photons reaching an ideal counter plane on the opposite side of the collimator was evaluated by analytical integration. To find a closed-form primitive function, some idealizations were required, and thereby parametric models were obtained for the optical field of view, dependent on slit dimensions (length, height and width) and source-to-collimator distance. It was shown that the count rate in the detector is independent of the collimator-to-source distance. For contributions from outside the optical field of view, where a closed-form expression cannot be found, instead fast numerical integration methods were proposed.The results were validated using the Monte Carlo code MCNP6.2. For the analytical method, deviations were larger, the shorter the collimator, with up to 25% of underestimation obtained for the shortest examined collimator of 10 cm length. However, the longer the collimator, the better the observed agreement. This accuracy is deemed to be sufficient for instrument design and measurement planning, where often the order of magnitude of the count rate is not a priori known. For the numerical method, the results showed an agreement within 3% for all evaluated collimator settings.The methods are planned for use in iterative optimization routines in the design of Gamma Emission Tomography devices, as well as for the prediction of gamma spectra obtained in the planning of fuel inspections. An application of the proposed method was demonstrated in spectrum prediction for a short cooling-time fuel rod test from the Halden reactor.

Experimental Method for Verification of Calculated 137Cs Content in Nuclear Fuel Assemblies

A method to determine the absolute activity of 137Cs in irradiated nuclear fuel is presented. Using a well-known point-like calibration source in combination with measurements of the gamma-ray intensity from the nuclear fuel and Monte Carlo calculations based on the nominal measurement geometry, the activity content can be determined without prior knowledge of the intrinsic detection efficiency of the gamma-ray detector. The presented method is tested using measurements of the 137Cs intensity from spent nuclear fuel of the pressurized water type at the central interim storage in Sweden. Using an assumption of homogeneous distribution of 137Cs throughout the fuel, we demonstrate a linear relationship between measured activity and the activity calculated by a state-of-the-art simulation code. For future studies, we suggest some factors that potentially can decrease the uncertainty in the correlation between measured and calculated activity.

Primordial black hole origin for thermal gamma-ray bursts

ABSTRACT A binary black hole (BH) astrophysical scenario where a mass-constrained (2.5 × 10−13M⊙) primordial black hole (PBH) undergoes a radial fall on to its heavier component (such as a supermassive black hole, SMBH) is described as an intense gamma-ray emission event. As the relativistic PBH approaches the Schwarschild SMBH event horizon, its Lorentz-boosted Hawking radiation progressively reduces to a near-zero emission cone resulting in a highly collimated thermal beam. Accordingly, our numerically calculated PBH flux density Sν and νSν fluence spectrum show a decreasing Planck-like spectral dependence consistent with the cooling behaviour of thermal-dominant gamma-ray bursts (GRBs). Our results might provide an alternative explanation for thermal GRBs based on PBH origin.

Monte Carlo analyses of the fusion neutron and gamma signals from the chromium self-powered detector.

To test the applicability of self-powered detectors (SPDs) for radiation monitoring in fusion reactor blankets, several irradiation tests have been undertaken with the ad hoc designed Cr-SPD, which presents the novelty of using chromium as the emitter material. This detector was exposed to an intense 60Co gamma-ray source, and to the 14MeV neutrons produced by the D-T fusion reaction. Detailed analyses of the measured signals have been done here using a Monte Carlo modeling technique. We describe the simulations of the fusion neutron and gamma tests of the Cr-SPD, and compare their results with the experimental ones. Keeping in view the difficulty in computational reproduction of the sophisticated nuclear-electrical phenomena behind low-level SPD signals, our model is found to perform well, giving correct electrical polarities and orders of magnitude of the signals, as well as valuable insights into their different components. Our experience has highlighted the deficits and the needed improvements for the traditional SPD simulation techniques for prompt signal analyses.