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Abstract The paper strives to identify through geostatistical simulations the parameters which build up a correlation between radionuclide activity concentrations measured on core samples and corresponding in situ total gamma count rates measured into boreholes drilled within the contaminated soil. This numerical exercise demonstrates that a linear relationship should exist between logarithmic values of in situ count rates and logarithmic values of activity concentrations when the contamination is strongly structured through space. A sensitivity analysis to some parameters (geostatistical range of the contamination structure, core sampling method, soil water content, multiple gamma-emitter contamination, etc.) is undertaken to identify which situations may impede the use of such a correlation. Then this approach is applied on Chernobyl measurements undertaken in 2015 and compared to the co-kriging method which considers the localization of the measurements and the additional measurements. It appears that co-kriging is a better estimator than linear regression, but the latter remains an acceptable way of estimating activity from gamma emitters and presents better results than lognormal regression. Therefore, total gamma logging measurements performed into boreholes of porous media contaminated by gamma-emitting radionuclides can be used for characterizing contamination and dealing with its spatial variability with the use of co-kriging. Graphical abstract Image 1 Highlights • The correlation between 137Cs activity and gamma count rates exists as long as 137Cs activity is structured in space. • Lognormal transformation is the best way to build this correlation but the bias induced has to be corrected in the back transformation. • Linear regression to estimate 137Cs activity by gamma count rates remains acceptable but cokriging is the best option to do so. [ABSTRACT FROM AUTHOR]

Abstract In this paper the gamma irradiation effects on the structural and electrical properties of n-Si and Al/n-Si Schottky junctions are presented up to a cumulative radiation dose of 1500 kGy. The structural studies using XRD and Raman spectroscopic techniques showed no greater degradation in the crystallinity of the n-Si crystals due to the irradiation effects. However, considerable variations in the I–V characteristics of Al/n-Si Schottky junctions and its junction parameters such as Schottky barrier height (Φ B), ideality factor (n) and series resistance (R S) indicates the presence of gamma induced defect states in the interface as well as bulk of the crystal. The surface and interface analysis of the irradiated Al/n-Si Schottky junction revealed modification in the effective work function of Al and presence of different chemical states (AlO x SiO x) in the interface. The contribution of these interface trap states on the band bending properties and I–V characteristics are explained in detail by realizing the power law characteristics and energy band diagram of the Al/n-Si Schottky junction. [ABSTRACT FROM AUTHOR]

Abstract Lower Jurassic (Sinemurian–Pliensbachian) successions cropping out in onshore areas of the Lusitanian Basin provide detailed information of three well characterized organic-rich intervals: i) the Unit F from the Coimbra Formation, ii) the Polvoeira Member of the Água de Madeiros Formation, and the iii) Marly Limestones with Organic-rich Facies (MLOF) Member of the Vale das Fontes Formation. Despite decades of research, these source rocks have not yet been properly identified and characterized in terms of extension and thickness in the basin's offshore. This paper compares detailed gamma-ray (GR) profiles from onshore outcrops (Coimbra, Montemor-o-Velho, Figueira da Foz, Monte Real, São Pedro de Moel and Peniche regions) with seven offshore wells. Our objective is to recognise Lower Jurassic organic-rich intervals in offshore areas of the basin, highlighting their lateral extension and improving the overall stratigraphic definition of the Lower Jurassic in the Lusitanian Basin. GR field measurements indicate that the highest GR values and U contents are consistently observed in the organic-rich intervals, reaching up to 134 API and 9.0 ppm of U. In contrast, the lowest API and U contents were determined in dominantly calcareous units, ranging between 5-34 API and 0.1-1.4 ppm, respectively. Wireline gamma-ray logs show a good correspondence between field patterns and offshore well logs, recognizing the organic-rich intervals in offshore areas. The highest GR values are interpreted to be linked with the 2nd- and 3rd-order maximum flooding intervals previously recognised in the Sinemurian–Pliensbachian successions in the western Iberian margin. Detailed GR maps linked to maximum flooding intervals highlight the variation of the vertical and lateral distributions of the organic-rich units in offshore areas of the Lusitanian Basin. Highlights • Recognition of units enriched in organic matter through GR signatures. • Correlation of surface-subsurface based on GR record. • Stratigraphic reinterpretation of the offshore Lusitanian Basin Lower Jurassic. • Spatial distribution of the organic matter in the LB's offshore. [ABSTRACT FROM AUTHOR]

Highlights • Investigation of the influence of homogenization on nuclear heating and shielding. • Heterogeneous model with detailed description of the BSM cooling system. • Homogeneous model simplified by removing pipes and introducing mixed materials. • Nuclear heating was calculated for several components and on a fine mesh for both models. • Homogenization tends to underestimate the local heat deposition and overestimates shielding. Abstract The electron cyclotron-heating upper launcher (ECHUL) will be installed in four upper ports of the ITER tokamak thermonuclear fusion reactor. Each ECHUL is able to deposit 8 MW power into the plasma for plasma mode stabilization via microwave beam lines. These beam lines and other components needed for the guidance of the microwaves are mounted into the upper port plug. In order to protect these components and to mitigate radiation leaving the reactor, several shield blocks are also included in the port plugs design. The ECHUL components which are closest to the fusion plasma are heated by the gamma and neutron radiation and therefore will need to be actively cooled. This paper reports on the influence of material homogenization by comparing results obtained in the neutronic analyses performed for the cooling system of the ECHUL blanket shield module (BSM). A small reduction in shielding performance of the BSM was found in the case of a heterogeneous description of the BSM compared to the standard approach of homogenizing the materials of the BSM by removing pipes and cooling circuits for the neutronic analyses. [ABSTRACT FROM AUTHOR]

Abstract Self-absorption correction factors are fundamental in spectroscopy to correct the efficiency of the samples detection whose density is different from the radioactive standard. Mathematical simulations have been widespread as a tool to facilitate the procedure of correction factors calculation. In this paper, LabSOCS was used to calculate the self-absorption correction factor for some geometries and the values found were compared to those obtained in MCNP and experimental values. The percentage deviations found for the self-absorption correction factor calculated by LabSOCS were below 1.6% when compared to experimental values. Deviations were below 1.9% in the curve extrapolation of the experimental procedure found in literature. Results obtained show that the deviations increase proportionally to the difference between the density values of the radioactive standard and the sample. High percentage deviations were also noticed in simulations whose samples had high densities, complex geometries and low energy gamma-rays. Highlights • Great density differences between the sample and the radioactive standard should not be used. • It is noticed that percentage deviations increase with an increase in density and with an energy decrease. • Geometry complexity is a factor which increases the percentage differences of the self-absorption correction factor. • Must be careful when reproducing the same chemical compositions of the experimental procedure in a computational simulation. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Defective Cu doped TiO 2 powders were prepared by sol-gel route and gamma treatment. • Nanoscale analysis show evidence of internal doping by Cu2+ in the TiO 2 sublattice. • Catalyst surfaces defect sites improve significantly the photocatalytic efficiency. • (Cu2+, V O - ) cooperative effects promote the photoelectrochemical properties of TiO 2. Abstract The aim of this paper is to study the effect of gamma-rays on structural, physicochemical, optical and photocatalytic performance of TiO 2 nanoparticles doped with different concentrations of copper ranging from 0 to 6 at.%. The powders have been prepared by sol-gel technique and annealed at 400 °C. They were irradiated by gamma-rays with doses varying from 14 to 60 KGy. These investigations confirm the formation of anatase TiO 2 nanoparticles and Cu2+ ion substitution for Ti4+ sites within the TiO 2 structure. This study also shows that, once the TiO 2 structure is saturated with copper, a metallic copper segregation is formed at the crystallite surfaces. After gamma irradiation, samples present a crystalline core and a disordered shell structure as a result of the formation of oxygen vacancies. Such oxygen vacancies at the TiO 2 nanocrystal surface lead to a remarkable enhancement of the photocatalytic activity of Cu-doped TiO 2 catalysts. [ABSTRACT FROM AUTHOR]

Highlights • Proposed a novel enhancement strategy. • Designed an adaptive gamma parameter which is simple and easy implemented. • Proposed a correction factor to enhance weak structures of the detail image. Abstract Image structure information is a watershed that distinguishes the content of an image, so it is very important for image enhancement techniques to correct uneven intensity of low-contrast optical remote sensing images with both strong and weak structures preservation. In this paper, a novel enhancement scheme, called spatially adaptive gamma correction (SAGC), is proposed to improve the visualization of optical remote sensing images with structures especially weak structure preservation. The SAGC method includes the following four parts: Firstly, the base image with strong structures and the detail image with weak structures are obtained by the employment of the relative total variation (RTV) method. Secondly, the base image is enhanced by a proposed adaptive gamma correction method. Thirdly, an enhancement factor is proposed to correct the detail image with weak structures. Finally, the high-contrast optical remote sensing image is obtained by the enhanced base image with the combination of the corrected detail image. Both quantitative and qualitative results on real low-contrast optical remote sensing images demonstrate that the proposed image enhancement scheme outperforms the state-of-the-arts in terms of brightness improvement, contrast enhancement, and detail preservation. [ABSTRACT FROM AUTHOR]

Abstract The influence of Jahn-Teller (JT) distortion on the electrochemical behavior of LiMn 2 O 4 is not fully understood nowadays. This paper concerns the role that structural defects play in reducing the magnitude of JT distortion. Structural defects were induced in micrometric and nanometric LiMn 2 O 4 using 60Co gamma radiation. Techniques such as X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and magic angle spinning spectroscopy (7Li MAS NMR) were used to detect and investigate the defects created by 60Co gamma irradiation in micrometric and nanometric LiMn 2 O 4. Differential scanning calorimetry (DSC) was used to study the effect on the JT distortion enthalpy. Spectroscopic and microstructural modifications of LiMn 2 O 4 produced by the action of radiation are shown for the first time. The results revealed that partial and total edge dislocations are generated after the oxides are irradiated. In the formed dislocations, manganese and lithium ions modified their surroundings and coordination, while the atomic positions of oxygen atoms changed in the fcc structure. These modifications gave rise to a decrease in the magnitude of JT distortion in the micrometric oxides, while no distortion was detected in the nanometric oxides. Because of the defects in LiMn 2 O 4 caused by 60Co gamma irradiation, a minor distortion in the cell parameter (c/a) should be expected when this material is used as a cathode in lithium-ion batteries. Highlights • Structural defects such as partial and total edge dislocations were induced in LiMn2O4 oxide by 60Co gamma radiation. • In the formed dislocations manganese and lithium ions modified their surroundings. • The oxygen atomic positions changed in the FCC structure. • The induced structural defects decrease the cooperative JT distortion produced in the crystalline material. [ABSTRACT FROM AUTHOR]

Prototypic neutronic parameters of thermal reactors were emulated in materials testing assemblies located in a 600 MWth metallic-fueled sodium fast reactor. Part of the outer reflector is composed of a moderating material such as graphite; all of the test assemblies were located in this designated thermalized region. Possible options for flux shaping assemblies and materials irradiation test assemblies are described. Both active and passive test assemblies are described. This paper focuses on PWR and VHTR in-core conditions. It is possible to modify the fast spectrum streaming from the driver to softer spectrum regions. In all configurations considered, the suggested options lead to significant neutron fluxes supporting accelerated neutron-induced damage studies. [ABSTRACT FROM AUTHOR]

The use of simulation within the nuclear industry has been limited by the perceived cost and benefits that such tools offer. In this paper, we present the development of a simulator based on the use of master-slave-manipulators to dismantle a small research reactor core assembly. We discuss the design of the simulator hardware and the different software elements that make up the system. We show how this type of tool can be used to explore various options during the development of a nuclear decommissioning process. Finally, we discuss the benefits that have been observed from using the system to support the decommissioning of the CONSORT research reactor. [ABSTRACT FROM AUTHOR]

This paper presents an enabling technology for high-efficiency fast-neutron detection for the Transient Reactor Test (TREAT) Facility hodoscope. The hodoscope is currently outfitted with 25.4-mm long Hornyak buttons for fast-neutron detection. However, they require improvements, as they suffer from low detection efficiency, Ĉerenkov radiation contaminating the signal, and non-linearity of detector response at large transients. To address these issues, a layered ZnS:Ag device has been constructed. The layered design provides various advantages: it incorporates greater scintillation volume, Ĉerenkov background is significantly reduced by eliminating the need for additional light guides, and the detection process is simplified by achieving gamma-ray rejection using only pulse-height discrimination. The result is a greater number of fast neutron counts with reduced background noise contaminating the signal. On being irradiated with a 252 Cf source (whose neutron energy spectrum closely mimics a reactor fission spectrum), a 25.4-mm long layered device was found to exhibit an intrinsic fast-neutron detection efficiency of 8.1% for neutrons with an average energy of 2 MeV, while a 43-mm long device allows for a greater number of fast neutron to be detected, increasing the efficiency to 9.1%. Further lengthening of the device up to 20 cm has been numerically predicted to exhibit even higher efficiencies. The detectors can be mass-produced easily and inexpensively. [ABSTRACT FROM AUTHOR]

This paper presents a p-MOSFET latch-based nuclear event detector signal-processing circuit which is implemented using a commercial standard 0.35- μ m CMOS process. A positive-feedback loop consisting of a p-MOSFET with a common-source configuration and a photocurrent compensation MOSFET are used to offset the transient radiation effects. Additionally, a timer circuit containing an on-chip timer capacitor serves to reduce the response time. To mitigate the total ionizing dose effect, all n-MOSFETs are laid out using dummy gate-assisted n-MOSFETs. The measured response time of the fabricated chip is 12.2 ns. After measuring the electrical characteristics of the fabricated chip, the chip is exposed to 60 Co gamma rays at a dose of 1.14 Mrad (Si). Even after exposure to radiation, the performance of the irradiated chip is nearly identical to that of a non-irradiated chip. To evaluate the upset threshold with regard to the dose rate of the fabricated chip, the chip is also exposed to prompt gamma rays with different dose rates, and the measured dose rate upset threshold is found to exceed 1.9 × 10 7 rad(Si)/s. [ABSTRACT FROM AUTHOR]

The Compact High Energy Camera (CHEC) is a camera design for the Small-Sized Telescopes (SSTs; 4 m diameter mirror) of the Cherenkov Telescope Array (CTA). The SSTs are focused on very-high-energy γ -ray detection via atmospheric Cherenkov light detection over a very large area. This implies many individual units and hence cost-effective implementation, as well as shower detection at large impact distance, and hence large field of view (FoV), and efficient image capture in the presence of large time gradients in the shower image detected by the camera. CHEC relies on dual-mirror optics to reduce the plate-scale and make use of 6 × 6 mm 2 pixels, leading to a low-cost ( ∼ 150 k€), compact (0.5 m × 0.5 m), and light ( ∼ 45 kg) camera with 2048 pixels providing a camera FoV of ∼ 9 degrees. The CHEC electronics are based on custom TARGET (TeV array readout with GSa/s sampling and event trigger) application-specific integrated circuits (ASICs) and field programmable gate arrays (FPGAs) sampling incoming signals at a gigasample per second, with flexible camera-level triggering within a single backplane FPGA. CHEC is designed to observe in the γ -ray energy range of 1–300 TeV, and at impact distances up to ∼ 500 m. To accommodate this and provide full flexibility for later data analysis, full waveforms with 96 samples for all 2048 pixels can be read out at rates up to ∼ 900 Hz. The first prototype, CHEC-M, based on multi-anode photomultipliers (MAPMs) as photosensors, was commissioned and characterised in the laboratory and during two measurement campaigns on a telescope structure at the Paris Observatory in Meudon. In this paper, the results and conclusions from the laboratory and on-site testing of CHEC-M are presented. They have provided essential input on the system design and on operational and data analysis procedures for a camera of this type. A second full-camera prototype based on Silicon photomultipliers (SiPMs), addressing the drawbacks of CHEC-M identified during the first prototype phase, has already been built and is currently being commissioned and tested in the laboratory. [ABSTRACT FROM AUTHOR]

Monitoring of concentrations of radon ( 222 Rn) and gamma level in underground uranium mines is essential to minimise the radiation exposure of miners within the prescribed limits stipulated by regulatory agencies. This paper presents the quantitative assessment of concentrations of 222 Rn and gamma radiation level at the different working places being operated at various depths of Narwapahar mine. Equilibrium Equivalent Radon (EER) concentration was found to be in the range varying from 60 to 850 Bq m −3 with a geometric mean of 289 Bq m −3 and geometric standard deviation of 1.94. The average value of EER in the mine was estimated to be about 29% of action level of 1000 Bq m −3 recommended by International Atomic Energy Agency (IAEA). Gamma radiation was found to be in the range of 0.73–6.15 µGy/h with arithmetic mean of 2.52 µGy/h and standard deviation of 1.49 µGy/h. Its average was calculated to be 31% of the derived regulatory limit of 8 µGy/h for 8 h working period in the mine. Furthermore, comparisons of EER and gamma radiation at various working places reveal that concentrations of EER are poorly correlated with grade of uranium ore whereas gamma radiation levels depend on it. The total annual radiation exposure of miners to radon and its daughters and gamma radiation in Narwapahar mine was evaluated to be 4.06 mSv/y, which was about of 20% of the prescribed limit of 20 mSv/y recommended by International Commission on Radiological Protection (ICRP). Thus it may be concluded that working condition of Narwapahar mine is considered as safe due to good ventilation condition of the mine and other control measures. [ABSTRACT FROM AUTHOR]

This paper presents the total dose effects of gamma ray and swift heavy ion irradiation on silicon-germanium heterojunction bipolar transistors (SiGe HBTs). The direct current (DC) characteristics, such as forward-Gummel, reverse-Gummel and current ideality factors before and after irradiation are analyzed and used to quantify the dose tolerance. Experiment results show that the performance degradation depends on the dose rate and bias condition during gamma ray irradiation. Compared to gamma ray irradiation, more serious base current degradation exists in the transistors exposed to 25 MeV Si ion. The base current in forward- and reverse-Gummel mode are found to show a distinct sensitivity to gamma ray and swift heavy ion irradiation. An increase in emitter current appears in the reverse-Gummel test after heavy ion irradiation. The underlying physical mechanisms are analyzed and investigated in detail. [ABSTRACT FROM AUTHOR]

Abstract: This paper shows the possibility to improve DC and RF electrical performances of AlGaAs/InGaAs PHEMTs by using low gamma radiation dose. The drain–source saturation current and the DC transconductance increase when the devices are irradiated with a gamma dose of 42.8krad(GaAs) and then remain constant up to 0.85Mrad(GaAs). This improvement is attributed to a reduction of access resistances. In the same time, the Schottky diode and the current-gain cut-off frequency of these components are not degraded by the gamma irradiation. Moreover, the maximum output power density is improved by 18%. This paper demonstrates that it is possible to improve the component electrical performances by using an original method. [ABSTRACT FROM AUTHOR]

Abstract: Planetary radiation environment modelling is important to assess the habitability of a planetary body. It is also useful when interpreting the γ-ray data produced by natural emissions from radioisotopes or prompt γ-ray activation analysis. γ-ray spectra acquired in orbit or in-situ by a suitable detector can be converted into meaningful estimates of the concentration of certain elements on the surface of a planet. This paper describes the verification of a Monte Carlo model developed using the MCNPX code at the University of Leicester. The model predicts the performance of a geophysical package containing a γ-ray spectrometer operating at a depth of up to 5m. The experimental verification of the Monte Carlo model was performed at the FRM II facility in Munich, Germany. The paper demonstrates that the model is in good agreement with the experimental data and can be used to model the performance of an in-situ γ-ray spectrometer. [Copyright &y& Elsevier]

In this paper, five detectors (EJ-270 — single plastic scintillator, EJ-309B5 — single liquid scintillator, and 3 phoswich detectors: EJ-276+GS20, GS20+EJ-276, EJ-309+GS20) were studied in terms of simultaneous detection of gamma-rays and slow and fast neutrons. The measurements were carried out in a mixed field of neutron and gamma radiation from an intense (∼ 106 neutrons/s/4 π) PuBe source. The PuBe neutron source was placed in an 18 cm diameter paraffin ball in order to increase the number of slow neutron detections. This paper covers the measurements of the neutron/gamma discrimination, photoelectron yield and analysis of the light pulse shapes originating from events related to gamma-rays, slow neutrons and fast neutrons. Sensitivity to slow neutrons is also briefly discussed. A comparison of n/ γ discrimination for all of the tested detectors shows excellent performance of all phoswich detectors. Phoswich configurations tested within the scope of this study allow unambiguously resolve all three types of radiation and show superior performance in comparison with single loaded plastic or liquid scintillators. [ABSTRACT FROM AUTHOR]

Sensor technologies will play a key role in the success of Remote Maintenance (RM) systems for future fusion reactors. In this paper, three key types of sensor technologies of particular interest in the robotics field at the moment are evaluated, namely: Colour-Depth cameras, LIDAR (Light Detection And Ranging), and Millimetre-Wave (mmWave) RADAR. The evaluation of the sensors is performed based on the following criteria: the types of data they provide, the accuracy at different distances, and the potential environmental resistance of the sensor (namely gamma radiation). The authors review the progress in making these three types of sensor capable of operating in Fusion facilities and discuss possible mitigations. Experiments are performed to demonstrate the pros and cons of each type of sensor by collecting data from radar, colour-depth camera and LIDAR, simultaneously. The paper concludes with a performance comparison between sensors, as well as discussing the possibility of combining them, fostering redundancy in case of failure of any individual sensor device. [ABSTRACT FROM AUTHOR]

Abstract: The International Atomic Energy Agency (IAEA) coordinates the work of a world-wide network of analytical laboratories, the Analytical Laboratories for the Measurement of Environmental Radioactivity (ALMERA) network. A proficiency test for ALMERA members was organized in 2006 based on the determination of gamma-emitting radionuclides (54Mn, 60Co, 65Zn, 109Cd, 134Cs, 137Cs, 241Am and 210Pb) in three matrices: water, soil and grass. This paper presents the methodology applied in this proficiency test and discusses the results of the analytical performance evaluation for 38 participating laboratories. The paper also addresses some technical root causes, which could explain low performances in the determination of 109Cd and 210Pb. [Copyright &y& Elsevier]

Abstract: Primary nucleosynthesis is defined as that which occurs efficiently in stars born of only H and He. It is responsible not only for increasing the metallicity of the galaxy but also for the most abundant gamma-ray-line emitters. Astrophysicists have inappropriately cited early work in this regard. The heavily cited B 2 FH paper () did not effectively address primary nucleosynthesis whereas Hoyle () had done so quite thoroughly in his infrequently cited 1954 paper. Even B 2 FH with Hoyle as coauthor seems strangely to not have appreciated what Hoyle () had achieved. I speculate that Hoyle must not have thoroughly proofread the draft written in 1956 by E.M. and G.R. Burbidge. The clear roadmap of primary nucleosynthesis advanced in 1954 by Hoyle describes the synthesis yielding the most abundant of the radioactive isotopes for astronomy, although that aspect was unrealized at the time. Secondary nucleosynthesis has also produced many observable radioactive nuclei, including the first gamma-ray-line emitter to be discovered in the galaxy and several others within stardust grains. Primary gamma-ray emitters would have been even more detectable in the early galaxy, when the birth rate of massive stars was greater; but secondary emitters, such as 26Al, would have been produced with smaller yield then owing to smaller abundance of seed nuclei from which to create them. [Copyright &y& Elsevier]

Abstract: Generalized Gamma (GG) distribution is a generic model that covers many well-known fading distributions as special cases. This paper deals with the performance analysis of L-branch equal gain combining (EGC) receivers operating over GG fading channels. For these receivers and by using convergent infinite series approach, the probability of error can be formulated in the form of an infinite series. The coefficients of series can be derived by calculating complicated integrations over the fading envelope distribution. In this paper, it is shown that the required integrations for the case of GG distribution have a complex closed-form in terms of Meijer''s G function, and then, a new approximation method is developed for computation of them. The proposed method only needs mean and variance of the fading envelope; hence it has low complexity and eliminates the need for calculation of complex functions. The presented numerical examples show that the developed method can approximate the required parameters and also the individual coefficients accurately and this accuracy increases with the increase of L. The proposed method is applied to analyze the probability of error performance of the L-branch EGC receiver with both coherent phase shift keying (CPSK) and frequency shift keying (CFSK) modulation schemes under different GG channel conditions. Also the effect of gain unbalance between diversity branches on the probability of error is investigated. [Copyright &y& Elsevier]

Abstract: Strong fields of thermal and epithermal neutrons as used for Boron Neutron Capture Therapy (BNCT) show a relatively small gamma dose. However, for accurate dose estimation, both the neutron as well as the gamma component has to be considered. Different approaches have been studied with various thermoluminescence detectors (TLDs). As a result, CaF2:Tm detectors (TLD-300) are attributed to be most insensitive to thermal neutrons but not tissue-equivalent. In this paper we focus on the measurement of the gamma dose with TLD-300 in mixed irradiation fields. To overcome the disadvantage of being not tissue-equivalent, a study on energy compensation filters was performed. The paper comprises also calibrations of TLD-300 using energy compensation filters at the PTB-reference field for thermal neutrons, and first test experiments at the TRIGA Mainz including simulations. [Copyright &y& Elsevier]

Abstract: Two major causes of polymer failure are discussed in this paper: degradation by gamma radiation and the environmental stress cracking. Both phenomena are reasonably well established in the literature with many papers dealing with them separately. However, the combined action of gamma radiation and stress cracking is a novel topic described in this work. Injection moulded bars of poly(methyl methacrylate) (PMMA) were exposed to gamma radiation to different doses and tested for mechanical properties and molecular weight. The exposed bars were then put in contact with ethanol, a stress cracking agent of PMMA. The stress cracking effects were evaluated by solvent absorption, stress relaxation and mechanical testing during solvent exposure. The results confirmed the high deterioration of PMMA by both gamma radiation and the active fluid. When degraded PMMA was exposed to ethanol the stress cracking effects tended to be higher in comparison to the undegraded polymer. This was possibly a result of the lower molecular weight and the higher affinity to ethanol. A study of fracture surface topography using scanning electron microscopy revealed surprising dendritic features in gamma degraded PMMA exposed to ethanol. These features were more evident when lower crosshead speeds were used during stress–strain experiments. [Copyright &y& Elsevier]

Abstract: Quality and shelf life of non-irradiated and irradiated (2.5 and 5kGy) sea bass in ice conditions and stored at were investigated by measurement in microbiological, chemical sensory analyses. Microbial counts for non-irradiated sea bass samples were higher than irradiated fish. Among chemical indicators of spoilage, total volatile base nitrogen (TVB-N) values increased to 36.44mg/100g for non-irradiated sea bass during iced storage, whereas for irradiated fish lower values of 25.26mg/100g and 23.61mg/100g were recorded at 2.5 and 5kGy, respectively (day 17). Trimethylamine (TMA-N) values and thiobarbituric acid (TBA) values for irradiated samples were lower than that for non-irradiated samples. Acceptability scores for odour, taste and texture of cooked sea bass decreased with storage time. The sensory scores of sea bass stored in control and 2.5–5kGy at were 13 and 15 days, respectively. The results obtained from this study showed that the shelf life of sea bass stored in ice, as determined by overall acceptability of all data, is 13 days for non-irradiated sea bass and 15 days for 2.5kGy irradiated and 17 days for 5kGy irradiated sea bass. [Copyright &y& Elsevier]

Abstract: This paper develops the work of Cattle et al. [Cattle, B.A., Fellerman, A.S., West, R.M., 2004. On the detection of solid deposits using gamma ray emission tomography with limited data. Measurement Science and Technology 15, 1429–1439] by considering a generalization of the model employed therein. The focus of the work is the gamma ray tomographic analysis of high-level waste processing. The work in this paper considers a two-dimensional model for the measurement of gamma ray photon flux, as opposed to the previous one-dimensional analysis via the integrated Beer–Lambert law. The mathematical inverse problem that arises in determining physical quantities from the photon count measurements is tackled using Bayesian statistical methods that are implemented computationally using a Markov chain Monte Carlo (MCMC) approach. In a further new development, the effect of the degree of collimation of the detector on the reliability of the solutions is also considered. [Copyright &y& Elsevier]

Abstract: In conventional Compton camera systems, the image reconstruction is performed only in two-dimensional or three-dimensional spatial coordinates for a specific gamma-ray energy. By doing so, a priori knowledge of the incident gamma-ray energy is required, and usually an energy window is applied to select full energy deposition events. In some other applications, spectral-deconvolution algorithms were developed to estimate the incident gamma-ray spectrum by deconvolving the observed energy-loss spectrum. However, usually the spectral system response function of a non-spherical detector depends on the incident gamma-ray''s direction, which cannot be modeled by those spectral-deconvolution algorithms. In this paper, we propose a new energy-imaging integrated spectral-deconvolution method, which utilizes both the Compton imaging and the spectral-deconvolution techniques. In the new method, the deconvolution takes place in a integrated spatial and energy space. This technique eliminates the requirement of knowing the gamma-ray energy in the imaging part, and removes the directional dependence in the spectral-deconvolution part. The deconvolved result provides the image at any specific energy, as well as the spectrum at any specific direction. The deconvolution method is based on the maximum likelihood expectation maximization (MLEM) algorithm, which is popular in reconstructing photon-emission images. Since the ML solution estimates the true incident gamma-ray intensity, the deconvolved energy spectrum at the source location is free of Compton continuum. To truthfully reconstruct the source distribution from the observation data, the accuracy of the system response function , i.e. the probability for a photon from source pixel to be observed as event , is the most crucial information. Because of the large number of pixels in the energy-imaging integrated space, and the very large number of possible measurement events, it is impossible to pre-calculate the system response function by simulations. In this paper, an analytical approach is introduced so that the system response function can be calculated during the reconstruction process. In order to perform Compton imaging, gamma-ray detectors are required to have position-sensing capability. The energy-imaging integrated deconvolution algorithm is applied to a three-dimensional position-sensitive CdZnTe gamma-ray imaging spectrometer, which can provide not only the energy-deposition information, but also the position information of individual gamma-ray interactions. The results demonstrate that the technique is capable of deconvolving the energy spectrum and of reconstructing the image simultaneously. [Copyright &y& Elsevier]

Abstract: The aim of this paper is to describe a new and efficient method to determine drying and carbonation profiles in concrete by gammadensimetry. First, the paper focuses on density and density variation measurements. A direct calculation of porosity and moisture saturation rate is proposed. Then, the uncertainties of these measurements are assessed. The results obtained on several materials are finally analyzed and validated by comparison with classical test results. The porosity profiles agree with mercury intrusion porosimetry and carbonation results with depths obtained by pH-indicator spraying. Thus, it is shown that gammadensimetry enables to monitor the evolution of density according to depth and time. Moreover, the auscultation by gamma-ray makes it also possible to determine the water content during drying as well as the quantity of fixed carbon dioxide in concrete during the carbonation process. [Copyright &y& Elsevier]

Abstract: A new model for the automated analysis of X-ray and gamma-ray multi-channel pulse height spectra is presented. The goal of the algorithm is to efficiently and accurately converge on the background and elemental factors while limiting human influence to the a priori defined knowledge of the detector characteristics. This information includes generic estimates of the continuum with defined elemental response functions. The energy space of the spectrum is subdivided and each subspace is fit independently. By considering all possible elemental line combinations within each energy subspace an optimal line combination is determined from the minimal squared error over each reconstructed elemental line combination. In this paper, we briefly review the background issues and motivations for the present research. The paper will present the algorithms and discuss related issues for elemental analysis of actual integrated spectra obtained from the Mars Odyssey Gamma-ray spectrometer. [Copyright &y& Elsevier]

Abstract: Methods of estimating external radiation exposure of soil-dwelling organisms are currently of much research and regulatory interest. In this paper, we report the first in situ measurements of the sub-surface gamma dose rate for 137Cs contaminated land that quantify variation in dose rate with depth. Two contrasting sites have been investigated. The first site comprised a mineral type soil with a low percentage of organic matter and the second site chosen was in a peat-bog. The different soil compositions afford different 137Cs mobility and this results in variations in the measured gamma dose-rate with soil depth. For each site the paper reports the measured dose rates, the 137Cs activity depth profile, the 137Cs inventory and a description of the soil-characteristics. It is suggested that these data can be used to produce estimates of the sub-surface gamma dose rate in other sites of 137Cs contamination. [Copyright &y& Elsevier]

In this review, we have recalled the main test stages carried out, aimed at receiving the authorization for ionizing radiation treatment for deteriorated books and archive documents, as a physical means for their recovery from the most important biodeteriorating agents. The first radiobiological tests were carried out on the efficiency of the treatment against insects and micro-organisms; after, we carried out other tests to identify any damage caused by radiation to the constitutive material of books (i.e. cellulose and paper) and to the printing inks that could endanger the mechanical and physical properties of this material during the following conservation period, or even to facilitate the attack of the harmful deteriorating agents or strengthen their harmfulness. The whole field evidence leads to state that gamma radiation treatment, if carried out using the correct doses needed for the recovery of the material, does not cause any contra-indication for the material itself. A responsible cost–benefit analysis of the action indicates that the use of this treatment is a valuable option compared to the chemical substances used so far, which have proven to be toxic and harmful for men and environment.Research aims: The present work [describes and] summarizes the experimental research performed by the author on the effects of gamma radiation on organisms that damage books: insects and microscopic fungi (molds). Paying particular attention to the depolymerization of cellulose, the author investigated whether and to what extent this undesirable collateral effect of irradiation on the principal structural component of books represents a real obstacle to the introduction of a promising technology for sanitizing of infested material. [Copyright &y& Elsevier]

The choice a suitable crystal growth method and a reasonable x value is of profound importance in the preparation of high quality Cd1−xZnxTe crystals for x-ray and gamma-ray detectors. The present paper reviews the evolution and development of Cd1−xZnxTe crystal growth for x-ray and gamma-ray detectors. At the same time, emphasis is put upon finding the relationship between the x value and the quality of the Cd1−xZnxTe. Three sets of Cd1−xZnxTe ingots with different x values, specifically 0.10, 0.15, and 0.20 were grown by the vertical Bridgman method (VBM) and characterized. Their x specification was then correlated with their dislocation densities, Te precipitates, inclusions, IR transmission, resistivities, and impurity concentrations, respectively. It was found that VBM Cd0.85Zn0.15Te as grown in this paper possessed the best choice of qualities with respect to defects and impurities. [Copyright &y& Elsevier]

For some years, the IR laboratory of Onera (Office National des Etudes et Recherches Ae´ros-natiales) has carried out accurate electro-optical characterisation on IR detectors. This paper presents some work on IR detector radiation hardness measurements. Onera, in collaboration with DGA/CEG (Centre d’Etudes de Gramat), measured the effects of γ radiation on long wavelength IRCMOS. The test conditions satisfy operational constraints, particularly, during the radiation, detectors were cooled and operating. This paper reviews the results of component behaviour for dose rate from 107 to 1010 rad/s. The transient and permanent effects are presented. [Copyright &y& Elsevier]

This paper summarizes some of the recent advances in high-purity germanium (HPGe) detector technologies and their applications. These important advances were driven by the necessity to support the recent increase in applications, uses and requirements for germanium detectors. Performances of single and multi-element closely packed HPGe detector arrays are discussed for various applications. Some of the developmental work to further improve the packing density of both large and small germanium detectors by using monolithic segmentation technology is presented along with the results. Monolithically segmented large germanium detectors are described which have high efficiency and high-energy resolution. Such detectors supply both interaction position and energy information of incident high-energy photons thereby providing powerful tools for gamma-ray tracking, polarimetry studies, low-energy filtration, and low-energy background rejection, etc. Monolithically segmented small germanium detectors provide improved solid angle ratio in X-ray detection systems without sacrificing energy resolution or throughput. Advancements in this detector technology are required for the fourth-generation Synchrotron Light Sources that are at the planning stage. This paper also reports on a revolutionary monolithic structure that is believed to be the first ever fabricated on large HPGe crystal. [Copyright &y& Elsevier]

LiCaAlF 6 :Eu,Y (LCAF) possesses excellent dosimetry properties for gamma radiation. Presence of Li in this phosphor makes it sensitive to thermal neutron without any coating or doping of neutron sensitive elements. The thermal neutron response of LCAF is found to be 1.5 mGy equivalent of 137Cs gamma for 9 × 107 n cm−2. TL and OSL response of LCAF has been found to be linear up to studied dose of ∼50 mGy for the thermal neutron. In this paper the feasibility of using LCAF as thermal neutron OSL dosimeter has been investigated. An OSL badge containing combination of LCAF and α-Al 2 O 3 :C discs can be used to evaluate thermal neutron and gamma doses separately in the mixed gamma-neutron field. • LiCaAlF 6 :Eu,Y (LCAF) can be used as thermal neutron dosimeter. • LCAF is insensitive to fast neutrons. • LCAF can be used in mix thermal neutron-gamma radiation field. [ABSTRACT FROM AUTHOR]

The paper characterizes concurrent effects of gamma-irradiation and presence of water in Portland cement pastes. An extensive nanomechanical quantification (Young's modulus, hardness, and creep compliance) at two scales is performed after exposure to two gamma-ray doses and a wide range of relative humidities (RH 0%–100%). Competing microstructural mechanisms such as water radiolysis, hydration, carbonation and drying were identified and their effects de-coupled with the aid of nanoindentation and other supporting techniques. Maximum radiation resistance was found for samples in medium humidities (33%–57%). Samples irradiated below 11% RH exhibited compaction of C-S-H phases at the level of 100 nm, ∼ 25% increase of Young's modulus and decrease of creep compliance due to water radiolysis and drying. The compaction resulted in microcracking at higher paste scale and caused ∼ 17% decrease of elastic modulus. Samples irradiated in water showed large (∼ 26%) decrease of Young's modulus and increased creep compliance accompanied by 9%–10% Portlandite loss. • Nanomechanical properties of irradiated cement pastes studied at various humidities. • Medium humidity helps cement pastes best withstand gamma radiation. • Radiolysis and drying leads to cement paste microcracking but also C-S-H compaction. • Gamma-irradiation counteracts with the hydration process of cement paste. • Decreased paste stiffness but increased creep is caused by radiation in the water. [ABSTRACT FROM AUTHOR]

This paper presents the capabilities of a measurement setup built to measure the axial distribution of neutron emitters in spent fuel pins from nuclear power plants. The measurement system uses a custom gamma-blind detector based on a novel combination of silver-activated zinc sulfide scintillators and wavelength-shifting fibers for direct fast neutron detection while having a low sensitivity for gamma rays even in the strong gamma fields present during the inspection of spent fuel. A collimator with an opening of 2 cm is used to create axial resolved information. The system has been tested using UOX and MOX spent fuel samples with burn-ups between 40 and 90 GWd/t and with long cooling times (20–25 y). Measurements of the total neutron emission of the samples relative to each other achieved a 1 σ uncertainty of 2%. Absolute values were measured by comparison with a calibrated 252Cf source, achieving a 1 σ uncertainty of 5%. The neutron emission of the samples was previously measured using a thermal neutron detector. The results from that previous measurement agree within 2. 5 σ with the new results. The reconstruction of the axial neutron emission profile was performed for one of the samples. Based on the edges of the sample, the resolution of the reconstruction was estimated to be 2.5 cm. These promising results are the basis for future development of the measurement setup which should not only improve the accuracy of the results but also enable the measurement of spent fuel with much shorter cooling times of ∼ 1 y. • Neutron emission of spent fuel rods was measured with a novel detector. • Relative neutron emission was measured with a standard deviation of 2%. • Relative and absolute mission values agree with previous measurements. • Absolute neutron emission was measured with a standard deviation of 5%. • Axial resolution was estimated at 2.5 cm. [ABSTRACT FROM AUTHOR]

Nuclear materials characterization in 870 L cemented waste drums is challenging due to significant neutron and gamma ray attenuation. Among the existing non-destructive approaches, photon active interrogation is of particular interest. A LINAC accelerates electrons to energies greater than 10 MeV, leading to highly penetrating interrogating bremsstrahlung photons that can reach nuclear materials in the depth of the 870 L waste drum and allow the detection of delayed gamma rays emitted by photofission products. Because the interrogating photon and neutron fluxes are extremely high during irradiation, measurements with high purity germanium detectors are usually performed after a long irradiation time, for example by moving the detector or the waste drum. Therefore, such measurements are only sensitive to delayed gamma rays associated to photofission products having sufficient long half-life of at least tens of seconds, which cuts a valuable signal coming from fission products with a shorter half-life. In this paper, we report gamma rays measurements of very short lived photofission products using a 3 in × 3 in cylindrical LaBr 3 (Ce) fast scintillation detector. A depleted uranium sample was irradiated by a pulsed bremsstrahlung source with maximum energy 17.5 MeV in a macro pulsing mode (1 s irradiation, 2 s cooling). This allowed to acquire a strong delayed gamma signal within a time window of 2 s. A clear signature of nuclear materials was observed even in the depth of a concrete mock-up, with an excellent signal-to-noise ratio beyond 3.5 MeV where the background of nonnuclear activated materials is negligible. These results are compared to a semi analytical model that qualitatively agrees but underestimates the measurements by a constant factor 1.7, probably caused by a wrong beam intensity normalization. Indeed, in this work the LINAC pulse time structure (macro pulsing) was different from its nominal working point used to characterize the beam (usual pulsing mode). Since it allows direct calculations of the detector response to delayed gamma-ray photofission measurements, this model is a fast calculation alternative to time-consuming Monte Carlo simulations, in view of further studies that will follow this feasibility demonstration. [ABSTRACT FROM AUTHOR]

• Piezoelectric technology is suitable for working under ITER conditions, with a good behavior in radiation environments. • The tested piezo actuator can work after being irradiated, although its maximum speed has been reduced by around 12%. • The controller to drive the piezo actuator can be located up to 110 m away, to keep electronics away from radiation. The Wide Angle Viewing System (WAVS) for ITER is a major diagnostic for machine protection, plasma control and physics analysis. The diagnostic will measure the surface temperature of the plasma facing components by infrared thermography being one of its main roles to protect them from damage. It will also image the plasma emission in the visible range. The full system is composed of 15 lines of sights located in four equatorial ports (3, 9, 12 and 17). As part of the ex-vessel optics, the first element of the optical chain is the Optical Hinge (OH). It is constituted by two folding mirrors which face the port plug exit optical beam. The mission of this component is to compensate the differential motion between the vacuum vessel and the building, during normal operation and baking. This function will be performed by means of a piezo actuator coupled to the OH upper mirror (and a set of reference switches) to drive the vertical displacement of the mirror in order to get the desired alignment position of the optical beam. The piezo actuator has been identified as the main critical item of the OH what has motivated the fabrication of an OH prototype (for one line of sight) aimed at performing a set of tests to validate the piezo actuator under operation conditions. The tests have consisted in the characterization of the piezo actuator behavior with the nominal load after being irradiated to 272.40 kGy of total accumulated gamma dose, which is the dose expected in ITER. Moreover, additional tests have been conducted to find out the influence of the cable length from the piezo actuator to the controller in the performance. A description of these tests and the results obtained will be presented in the paper. [ABSTRACT FROM AUTHOR]

This paper reports the luminescence properties of nanocrystalline calcium fluoride doped with dysprosium (CaF 2 : Dy). The nanophosphor has been synthesized by the chemical co-precipitation technique and the dopant concentration has been optimized at 0.3 mol% using thermoluminescence (TL) intensity emitted post 50Gy gamma dose irradiation of samples doped with different dopant concentrations. X-ray diffraction shows the formation of crystalline particles with an average size of 49.233 nm. Photoluminescence (PL) emission spectrum shows the characteristic peaks at 455 nm, 482 nm, 573 nm corresponding to 4I 15/2 to 6H 15/2 , 4F 9/2 to 6H 15/2 and 4F 9/2 to 6H 13/2 Dy3+ transitions respectively. PL excitation spectrum shows a peak at 327 nm which corresponds to the Dy3+ transition of 6H 15/2 to 4L 19/2. Gamma (of 1.25 MeV) and low energy proton beam (of 30 keV) irradiated nanophosphor shows a variation in TL glow curve structure and peak position with an increase in radiation dose/fluence. However, the nanophosphor shows a wide linear dose response for 60Co gamma radiation in the range 10 Gy - 1.5 kGy and for low energy proton beam in the fluence range of 1012–1014 ions/cm2. Srim 2013 has been used to calculate the ion beam parameters including the range of protons in CaF 2 : Dy 0.3 mol%. The nanophosphor CaF 2 : Dy could be further investigated as a potential dosimeter for gamma rays and proton beam by studying its TL properties for different energies of these radiations. • CaF 2 : Dy nanophosphor was irradiated for the first time with low energy proton beam of energy 30 keV. • The nanophosphor showed a linear dose response from 10 Gy to 1.5 kGy of gamma rays from 60Co source. • PL emission spectrum for the nanophosphor showed characteristic Dy3+ transitions at 455 nm, 482 nm and 573 nm besides the defects in the material. • The nanophosphor showed a simple cubic structure with an average size of 49.23 nm favourable for good TL efficiency. [ABSTRACT FROM AUTHOR]

The High-Altitude Water Cherenkov (HAWC) observatory is a second-generation continuously operated, wide field-of-view, TeV gamma-ray observatory. The HAWC observatory and its analysis techniques build on experience of the Milagro experiment in using ground-based water Cherenkov detectors for gamma-ray astronomy. HAWC is located on the Sierra Negra volcano in México at an elevation of 4100 meters above sea level. The completed HAWC observatory principal detector (HAWC) consists of 300 closely spaced water Cherenkov detectors, each equipped with four photomultiplier tubes to provide timing and charge information to reconstruct the extensive air shower energy and arrival direction. The HAWC observatory has been optimized to observe transient and steady emission from sources of gamma rays within an energy range from several hundred GeV to several hundred TeV. However, most of the air showers detected are initiated by cosmic rays, allowing studies of cosmic rays also to be performed. This paper describes the characteristics of the HAWC main array and its hardware. [ABSTRACT FROM AUTHOR]

Radiation interaction parameters are important for exploring the technological relevance of materials in radiation environments. In this research paper, gamma-ray shielding efficacy of GeO 2 +B 2 O 3 +P 2 O 5 +ZnO magneto-optical glasses doped with Tb3+ and coded as GBPZT1-6 for Tb3+ doping concentrations ranging from 20 to 45 mol%, with a 5-mol% increment was investigated using theoretical and Monte Carlo simulation methods. The PHITS code and the Phy-X/PSD software was used to compute the mass attenuation coefficient (MAC) and other interaction quantities of the glasses for 0.015–15 MeV photons. Both methods' MAC data agree to within 2.90% of each other. At 0.015 MeV, the value of MAC is 59.9674 cm2/g, 64.1777 cm2/g, 67.6697 cm2/g, 70.6128 cm2/g, 73.1271 cm2/g and 75.2998 cm2/g for GBPZT1, GBPZT2, GBPZT3, GBPZT4, GBPZT5 and GBPZT6, respectively. The linear attenuation coefficients of the GBPZT glasses changed from 0.1340 to 247.5640 cm−1, 0.1490 to 286.8040 cm−1, 0.1650 to 326.6350 cm−1, 0.1790 to 365.7810 cm−1, 0.1990 to 413.9290 cm−1, and 0.2190 to 463.9450 cm−1 for GBPZT1, GBPZT2, GBPZT3, GBPZT4, GBPZT5, and GBPZT6. Comparatively, the photon attenuation abilities increase linearly as the density and Tb 2 O 3 content of the glass system increased. Hence, GBPZT6 has the highest mass and linear attenuation coefficients, while GBPZT1 has the least. The BPZT glasses have better photon absorbing capacities compared to ordinary concrete and some other conventional shielding materials, thus making them attractive choice in radiation protection functions. • Radiation shielding capacity of germinate glasses is estimated. • Monte Carlo simulations are carried out. • A good agreement between the theory and the simulation. • GBPZT6 glass system has a potential use in nuclear applications. [ABSTRACT FROM AUTHOR]

• FOCS will be used to perform current measurements in the ITER harsh environment, with the sensing fibre located directly on the vacuum vessel. • Samples of candidate FOCS optical fibres were exposed in neon atmosphere at 110 °C to Co60 gamma radiation up to 3 MGy, and then annealed at 210 °C, which is representative for service condition during ITER nuclear operation. • The fibre sequential ageing was addressed using gravimetry and microscopic optical inspection. • The applied stress is beyond the standard limits, but the fibres survived the exposure without critical degradation. • The results are attributed to the use of the inert atmosphere. ITER is expected to achieve new milestones on the way to commercial fusion energy production. This will be still a research machine where numerous diagnostic systems are deployed, both already used on existing tokamaks and developed specifically for burning plasma operation. One of the innovative diagnostics is the Fibre Optics Current Sensor (FOCS). This paper describes recent results of the ITER FOCS development, concentrating on the front-end design. The FOCS sensing fibre, likely acrylate coated, will be located directly on the external surface of the vacuum vessel. During operation, it will be exposed to temperatures of 100–110 °C and multi-MGy level total radiation doses, while during vacuum vessel baking intervals the temperature will be 200–210 °C with low levels of radiation. Such temperatures are outside the nominal range for acrylate coatings even for acrylate coatings specially designed for high temperature applications. We provide experimental results that indicate that acrylate coated fibres FOCS fibres nevertheless can survive ITER environment without critical degradation and attribute this to the system design, for which the fibre operates in an inert gas (neon) atmosphere. [ABSTRACT FROM AUTHOR]

In this paper (Paper II) we complete our discussion on the results of a comprehensive GEANT simulation of the scientific performance of the AGILE Gamma-Ray Imaging Detector (GRID), operating in the ∼30 MeV–50 GeV energy range in an equatorial orbit of height near 550 km. Here we focus on the on-board Level-2 data processing and discuss possible alternative strategies for event selection and their optimization.We find that the dominant particle background components after our Level-2 processing are electrons and positrons of kinetic energies between 10 and 100 MeV penetrating the GRID instrument from directions almost parallel to the Tracker planes (incidence angles θ≳90°) or from below.The analog (charge) information available on-board in the GRID Tracker is crucial for a reduction by almost three orders of magnitude of protons (and heavier ions) with kinetic energies near 100 MeV.We also present in this paper the telemetry structure of the GRID photon and particle events, and obtain the on-board effective area for photon detection in the energy range ∼30 MeV–50 GeV. [Copyright &y& Elsevier]

We present in this paper the results of a comprehensive GEANT simulation of the Gamma-Ray Imaging Detector (GRID) being developed for the AGILE space astrophysics mission. The GRID is designed to be sensitive in the ∼30 MeV–50 GeV energy range, with excellent imaging and timing capabilities, and with a very large field-of-view (∼3 sr). In this paper (Paper I) we present the GRID baseline geometry, a model for the charged particle and albedo-photon backgrounds for an equatorial orbit of 550–600 km altitude, and the main results of the first level (Level-1 Trigger) on-board data processing. Our simulations show that the GRID Level-1 data processing is expected to be capable of decreasing by a factor of ∼20 the charged particle background (from ∼2 kHz to below 100 Hz), and by a factor of ∼30 the albedo-photon background. The gamma-ray photon detection efficiency by the imaging GRID is simulated to be particularly efficient, varying between 39% and 17% depending on photon energies and incident directions. [Copyright &y& Elsevier]

One direct way to improve the gamma camera's sensitivity is using large-area gamma detectors. During construction of a large-area gamma camera, achieving high uniformity (including both spatial uniformity and events count map uniformity) across the entire active area is a major challenge. Another fabrication concern is that large-scale gamma sensors (mainly with reference to scintillators) and photoelectric converters such as position-sensitive photomultiplier tubes (PSPMTs) and silicon photomultipliers (SiPMs) are required. In this work, to design a large-area gamma camera with high uniformity, a 22 × 22 CsI(Na) array with a pitch size of 4.6 × 4.6 mm 2 is divided into four optically isolated 11 × 11 modules, where each module is coupled independently to an 8 × 8 SiPM array (6.13 × 6.13 mm 2 per channel) and is then read out using separate preamplifier electronics. The preamplified signals for each module are sampled independently via their respective analog-to-digital converters (ADCs) and the digitized signals are then processed in a single field-programmable gate array (FPGA). Extra dead zones and optical losses are avoided between the modules as a result of the optimal design used in the junction area for the four modules. This modular concept leads to a high counting rate capability. 2D flood field images of the 22 × 22 CsI(Na) array are obtained under uniform irradiation using 241Am. The counting rate measurements are performed using 137Cs under various attenuation conditions. The sensitivity is tested and compared with existing devices. The results show that high uniformity (1.43) and high counting rate capability (∼ 72% improvement) are achieved. Thanks to the large-area gamma sensor, the gamma camera developed in this paper achieves highest sensitivity among the listed devices (Locating 137Cs producing 0.6 ± 0. 02 μ Sv/h in < 10 s). The principles developed in this paper can be applied to the construction of large-area radiation detectors. [ABSTRACT FROM AUTHOR]

Abstract An innovative method for the determination of the depletion in research reactor fuel assemblies (FAs) based on gamma transparency was developed, tested, and presented. The basic concept is the assessment of the uranium content from the attenuation of gamma rays passing through the FA, which is placed between a gamma-emitting source and a spectroscopic detector. With increasing depletion, more uranium transforms into fission products, which causes a significant decrease in the gamma-rays attenuation at energies higher than ∼ 116 keV, thus increasing the count rate at the detector. The attenuation from the fuel assembly was compared to that of a fresh (highest known uranium content, most opaque to gamma-rays) and dummy (Aluminum-only; most transparent) fuel assemblies, and subsequently, a logarithmic interpolation to determine the current uranium content was performed. In this study, a low-energy gamma ray of 155 keV (emitted from 188Re) was used, which exhibited significant contrast between the attenuation through the uranium versus its fission products, while obtaining sufficiently high count-rate at the detector at relatively short count durations. The 188Re source was generated prior to the experimental campaign through the 187Re(n, γ) reaction by irradiation of natural rhenium in IRR1 (Israel Research Reactor 1, 5MW open-pool HEU MTR-type fuel, Soreq Nuclear Research Center, Israel). Five FAs of different irradiation histories previously used in the IRR1 reactor were studied. The determined depletions were found to be in the range of 47%–59%, with absolute uncertainties of 2%–3%. The axial distribution of the depletion along the FAs was determined with high resolution (20 axial points per FA) using the low-energy photons and found to be in good agreement compared to the axial distributions obtained from fission products such as 137Cs. Experimental results of the present study were also compared to results of a different experiment that used the traditional gamma ray spectroscopy technique (i.e., using 137Cs activity) for one of the studied fuel assemblies (FS-5), giving good agreement in both the axial depletion distribution, as well as the whole assembly depletion. Thus, the method described in this paper demonstrates improved accuracy compared to other non-destructive spectroscopy-based methods. Furthermore, we managed to obtain spectroscopic signatures of relatively short-lived fission products such as 140Ba (T 1 ∕ 2 = 12. 7 days) from an FA that was irradiated 65 days before the measurement. [ABSTRACT FROM AUTHOR]

The radiation levels from used nuclear fuel make their post irradiation examination very difficult. Handling material removed from assemblies is almost exclusively performed inside shielded hot cells. Neutron radiography provides a non-destructive option for examining the internal structure, location and integrity of irradiated fuel. This paper addresses the performance and stability of a neutron imaging detector comprised of microchannel plates (MCPs) and a Timepix readout in gamma and neutron radiation environments. The detector is being considered as an alternative to the currently used activation foils and photographic film measurement techniques. The MCP/Timepix detector was used in neutron radiography experiment on a beam line at the Neutron Radiography Reactor (NRAD) at Idaho National Laboratory (INL). The detector was installed ∼ 17.5 m from the reactor core with a line of sight view to the core, which results in a fast and epithermal neutron spectrum as well as high intensity gamma radiation. The gamma-ray dose rate in the beam line was 812 mSv/hr. Complementary measurements were made using 137 Cs and 60 Co isotopic sources at gamma dose rates in excess of 6 Sv/hr. The detector functioned normally over several hours in this environment. These conditions are comparable to planned radiography of irradiated nuclear fuel assemblies. Experimental results using ASTM sensitivity and beam purity indicators suggest that a spatial resolution of <100 μ m may be possible in neutron radiographic measurements using this detector for studies of irradiated nuclear fuel. Potential radiographic and tomographic applications are discussed. The results of present experiments are not limited to the studies of irradiated fuel assemblies, but rather are relevant to any experiment where imaging needs to be performed in a high radiation environment. [ABSTRACT FROM AUTHOR]

Abstract This paper reviews current understanding of the role of free radicals in the oxidation of polyethylene induced by high-energy irradiation (gamma or e-beam). To evaluate the reactivity, stability and mobility of different macroradicals, their reactions after gamma irradiation of different polyethylenes (LDPE, LLDPE, VLLDPE, HDPE, UHMWPE) are considered. Macroradicals are formed in all phases of PE (crystalline, amorphous and interphase). Their overall determination is possible only if both irradiation and detection are carried out at 100 K, or below. At this temperature, the most abundant macroradical formed is the secondary alkyl macroradical (R’’°). On gradually raising the temperature, the macroradicals decay with formation of vinylene double bonds and molecular hydrogen. At room temperature, the macroradical concentration is about 4% of the original quantity at 100 K for LDPE and around 15% for HDPE. In HDPE and UHMWPE; the macroradicals are mainly present in the crystalline phase and in short times (hours) they migrate to the amorphous phase. In LDPE and LLDPE macroradicals are mainly allylic, present in minimal amounts at the crystalline-amorphous interphase. In the nearly fully amorphous VLDPE no residual macroradicals can be detected at room temperature. The mobility of R’’° is variable and is a function of the mobility of the polymer backbone, slow in the crystalline phase, relatively fast in the amorphous phase. Kinetic stability, or persistence, is often more important than thermodynamic stability in determining radical lifetimes, in particular for radical processes in the solid phase. Alkyl macroradicals react with chain imperfections, additives and oxygen, in a cyclic process involving initiation, propagation and termination reactions. The initiation reactions form macroradicals by cleavage of the C-H bonds of PE, induced by irradiation or by photo- or thermal-scission of peroxides formed during processing of the polymer. Propagation involves the reaction of R’’° with vinyl or vinylidene double bonds, with the formation of a new radical, in competition with their reaction with oxygen to form various oxidation products (ketones, hydroperoxides acids, alcohols and esters). It is notable that the formation of ketones does not necessarily require decomposition of the hydroperoxides. In the presence of stabilizing additives, radicals react with the additive (ADH), with the formation of a more kinetically stable radical (AD°), which considerably decreases the propagation rate, but a termination reaction between R’’° and AD° may also be envisaged. It is observed that radiation-induced oxidation has a constant rate during irradiation. Post-irradiation, the oxidation occurs via transfer of the macroradicals from the crystalline phase and the interphase to the amorphous phase, where oxygen is available, and the rate decreases, approaching zero. The occurrence of termination is apparent. Termination must occur through the reaction of two macroradicals. The reaction between two R’’° is difficult, due to steric hindrance. The most probable reaction is that between peroxy macroradicals (ROO°), fixed in position on the polymer chain and R’’°, which migrate through the polymer bulk. This reaction is difficult to confirm experimentally because of the lack of reliable analytical methods for ROOR species in the presence of ROOH. The formation reactions of the different oxidation products are reported and the branching reactions occurring in thermal and photo-oxidation are also discussed. Highlights • All the oxidation products are formed by directly reaction between R’’° and d oxygen. • The formation of ketones does not necessarily require decomposition of the hydroperoxides. • The reaction between two R’’° is difficult, due to steric hindrance. • The most probable termination reaction is that between peroxy macroradicals (ROO°), and R’’. [ABSTRACT FROM AUTHOR]

Cu 2 ZnSnS 4 (CZTS) thin films have been synthesized by spray pyrolysis technique, deposited on glass substrates and then irradiated by high gamma radiations. Six gamma radiation doses have been applied: 10, 20, 30, 40, 50 and 100 kGy. The main objective of this work was to study the physical properties behavior of CZTS thin films under high gamma irradiation. Structural, optical and morphological properties of CZTS thin films were explored by X-ray diffraction, spectrophotometer and Scanning Electron Microscope, respectively. Structural analysis has shown that no noticeable changes have been occurred in the preferred orientation (112) or diffraction angles after gamma irradiation. Nevertheless, a significant increase in crystallite size from 52 to 79 nm has been observed after irradiation with 100 kGy gamma dose, which indicates a clear enhancement in crystalline structure. Certain optical parameters such as absorption and extinction coefficients (α(λ),K(λ)) have been only slightly affected, which indicate a radiation hardness of the CZTS thin films within the ionizing radiation range studied in this paper. Band gap energy of the irradiated thin films have been increased with the irradiation and reached 1.6 eV at 100 kGy gamma dose. Other optical parameters such as refractive index n(λ) and lattice dielectric constant (ε) have been determined and analyzed. All these experimental results clearly showed that structural properties of CZTS films have been improved by gamma irradiation while the optical properties have been slightly changed, which is favorable for optoelectronic applications working near nuclear environments or even for outer space solar cells and instrumentation for high-altitude flight, where gamma radiations are abundant. [ABSTRACT FROM AUTHOR]