Simulation Of Radiation Effects Research Articles

Defects in Insulating Materials

AbstractThis issue of physica status solidi (c) is dedicated to papers submitted during the 2012 International Conference on Defects in Insulating Materials (ICDIM 2012), which was held in Santa Fe, NM USA on June 24–29, 2012. ICDIM 2012 is the 18th edition of a series that began in 1956 at Argonne, USA, with the meeting “Color Centers in Alkali Halides”. International conferences (ICDIM) take place every four years and are alternated with Europe‐specific conferences (EURODIM). The series is a broad international forum on the science and technology of defect‐related phenomena in crystalline and amorphous wide band‐gap materials. Recent ICDIM conferences were held in South Africa (2000), Latvia (2004) and Brazil (2008). ICDIM 2012 was held jointly with Computer Simulation of Radiation Effects in Solids (COSIRES), which is a biennial conference that focuses on advanced computer modeling of surface and bulk phenomena stimulated by all forms of irradiation. Both ICDIM and COSIRES were held at the Santa Fe Community Conventional Center, and the poster session was held jointly in order to promote cross‐pollination.ICDIM 2012 received 142 abstracts from 131 reg‐istered attendees (from 21 countries), in the areas of luminescence, scintillation, fundamental modeling, nuclear fuel, radiation damage, nanostructures as well as several on specific materials such as LiNbO3 and carbides, nitrides and diamond. Three keynote lectures were given during the first technical session of each day in order to provide a historical perspective and context for the oral presentations that followed. In addition to the keynote presentations, 13 invited and 52 contributed talks were presented. Young Researcher Awards were presented for best talk and poster to Qi Li (Wake Forest University) for his presentation “First principles calculations and experiment predictions for iodine vacancy centers in SrI2” [Phys. Status Solidi B 250, 233 (2013)] (sponsored by pss) and Yury Deshko (CUNY) for his presentation “Effects of planar geometry on the inhomogeneous broadening of zero‐phonon lines of optical centers in diamond” [Phys. Status Solidi B 250, 278 (2013)] (sponsored by New Mexico Consortium), respectively.We would not have been able to host ICDIM in Santa Fe without excellent organizational and technical support of the New Mexico Consortium and generous financial support from Los Alamos National Laboratory, Netzsch and Los Alamos National Bank.The International Committee has selected Canterbury, Kent in England as the site of EURODIM 2014, to be held July 13–19, 2014 and chaired by Dr. Maria Alfredsson and Dr. Serena Corr of the School of Physical Sciences, University of Kent, and advised by members of the International Committee, Professor Alan Chadwick (University of Kent) and Dr. Rob Jackson (Keele University). Furthermore, the International Committee has also selected the place for ICDIM 2016 as Lyon, France, which will be chaired by Prof. Christophe Dujardin and Dr. Marie‐France Barthe. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Simulation of radiation effects in ultra-thin insulating layers

The Monte Carlo simulations of charged particle transport are used to investigate the effects of exposing ultra-thin layers of insulators (commonly used in integrated circuits) to beams of protons, alpha particles and heavy ions. Materials considered include silicon dioxide, aluminum nitride, alumina, and polycarbonate - lexan. The parameters that have been varied in simulations include the energy of incident charged particles and insulating layer thickness. Materials are compared according to both ionizing and non-ionizing effects produced by the passage of radiation.

金属氧化物半导体场效应管长期辐射效应的数值模拟

金属氧化物半导体场效应管长期辐射效应的数值模拟

Simulation of laser radiation effects on low dimensionality structures

This paper presents a study on a system comprised of a low-dimensional structure (Ga1-xAlxAs and GaAs quantum well wire), an intense laser field and an applied magnetic field in axial direction, resulting in a modified structure by interaction with the laser field. A variation of the concentration of aluminum is considered. So, the characteristics of the semiconductor such as the effective mass and width of the forbidden band vary due to the aluminum concentration. The electronic Landé factor control by changing of both intensity and frequency of a laser field on cylindrical quantum well wire was also reported. We use the laser dressed approximation for the treated "quantum wire + laser" system as quantum wire in the absence of radiation but with parameter (electronic barrier height and electronic effective mass) renormalized by laser effects. We consider a magnetic field applied in the parallel direction of symmetric axis of the quantum well wire. We take into account non-parabolicity and anisotropy effects on the conduction band by Ogg-McCombe Hamiltonian.

Impact of uncertainties in atmospheric mixing on simulated UTLS composition and related radiative effects

The upper troposphere/lower stratosphere (UTLS) region plays an important role in the climate system. Changes in the structure and chemical composition of this region result in particularly large changes in radiative forcings of the atmosphere. Quantifying the processes that control UTLS composition (e.g., stratosphere‐troposphere exchange) therefore represents a crucial task. We assess the influence of uncertainties in the atmospheric mixing strength on global UTLS distributions of greenhouse gases (water vapor, ozone, methane, and nitrous oxide) and associated radiative effects. The study is based on multiannual simulations with the Chemical Lagrangian Model of the Stratosphere (CLaMS) driven by ERA‐Interim meteorological data and on a state‐of‐the‐art radiance code. Mixing, the irreversible part of transport, is controlled by the local horizontal strain and vertical shear of the atmospheric flow. We find that simulated radiative effects of water vapor and ozone, both characterized by steep gradients in the UTLS, are particularly sensitive to uncertainties of the atmospheric mixing strength. Globally averaged radiative effects are about 0.72 and 0.17 W/m2for water vapor and ozone, respectively. For ozone, the largest impact of mixing uncertainties is observed in the extra‐tropical lower stratosphere.

Control of the Flight Vehicle Cable over Wide Spectrum Radiation Effects Simulation Experiment Research

According to the aircraft is under complex work hard to electromagnetic environment performance analysis of the issue, a vehicle body and control lead in ultra-wideband high power microwave (UWS-HPM) under the irradiation of coupling effect and experimental study. Use back to lose signal simulator with the repetitive; the change control the length of the wire, radiation orientation, irradiation parts and other measures to make the experiment generality. The results of the study show that: aircraft in more than 25 kV/m of field UWS-HPM irradiation, interference and make its crash. Interference coupling mechanism is energy electromagnetic pulse through the control lead into the control box, and influence the formation of the control order. On the basis of experiment, this paper analyzes the interference with various factors coupling relation, which for electromagnetic protection equipment provides a theoretical basis.

The simulation of radiation effects to astronauts due to solar energetic particles in deep space

The exposure to interplanetary radiation poses a serious health risk to astronauts, especially for long-term missions. Protecting the astronauts from these particles has been the key issue to the manned space mission. High-energy space particles can penetrate the protective layer of a spacecraft, and probably cause deleterious effects to the astronauts. To estimate the size of these effects, a credible simulation of radioprotection is required. Using the Geant4 software toolkit, we have modeled the interaction processes and predicted the total energy deposit in a phantom (astronaut) as well as the similar information associated with secondary effects, due to Solar Energetic Particles (SEPs) at ∼1 AU caused by the large SEPs events in October 1989 and August 1972. In addition, we compared the characteristics of the energy deposit due to SEPs and Galactic Cosmic Rays (GCRs) and explained the differences between them by physical mechanism analysis.

Validation of nuclear reaction models of 180 MeV proton-induced fragmentation of 27Al

Kinetic energy, angular distribution, and isobaric cross section data for A = 7–25 fragments formed in p + 27Al reaction at bombarding energy of 180 MeV are compared with the calculations of the Binary Cascade Model (BIC), the Cascade Exciton Model (CEM), JQMD/PHITS, as well as the Statistical Model with Final State Interaction (SMFSI). For completeness, the kinetic energy spectra of light particles (n, p, α) formed in p + 27Al reaction at bombarding energy of 156 MeV are also presented. A general agreement between the data and predictions of these models is found. However, disagreement with the data for the yields of light-mass fragments as well as near-target fragments is also found and discussed. The importance of this comparative study to simulation and analysis of radiation effects on microscopic electrical components operating in space is also discussed.

Simulation of aerosol radiative effects over West Africa during DABEX and AMMA SOP-0

The regional climate model RegCM3 has been used to assess optical properties and clear-sky direct radiative forcing (DRF) of mineral dust and carbonaceous aerosols over West Africa for the period October 2005 to April 2006. Our results display a significant seasonal variation of the aerosol single scattering albedo (SSA) due to varying contributions from biomass burning (BB) and dust. During December-January, simulated SSA values dropped to around 0.81-0.83 at 440 nm and to 0.80-0.85 at 675 nm when absorbing aerosols from biomass burning dominate the mixture. During March and April, when mineral dust dominates, simulated SSA values increased reaching around 0.90-0.92 at 440 nm and 0.94-0.96 at 675 nm. The simulated aerosol optical thickness (AOT) was maximum over central Africa where it far exceeded estimates of AOT from satellite which showed the greatest AOT in the gulf of Guinea. This discrepancy was linked to an overestimation of BB emissions in central Africa and a possible underestimation of AOT over central Africa due a high occurrence of cloud and associated difficulties in cloud screening. The DRF calculations were extremely sensitive to aerosol optical properties and underlying surface albedo. Over dark surfaces, the sum of shortwave (SW) and longwave (LW) top of the atmosphere (TOA) direct radiative forcing averaged from December to February was negative (−5.25 to −4.0 W/m2) while over bright surfaces it was close to zero (−0.15 W/m2). Large differences between SW surface and SW TOA direct radiative forcing indicated that SW absorption had an important influence on the radiative budget. The SW radiative heating rate associated with the aerosol reached 1.2 K/d at local noon (diurnal mean of 0.40 K/d) over Niamey (∼13.5°N, 2°E) and peaked at altitudes of 2-4 km, corresponding to the BB aerosol layer.

Bacterial Virulence Activation And Impaired Gut Epithelial Healing: Integration Of In Vitro Mechanisms With An Agent-based Model

Introduction: Despite extensive investigation, disruption of intestinal anastomoses leading to leak and sepsis remains as a significant cause of surgical morbidity. While both host and microbial factors independently play roles in anastomotic failure, their dynamic bidirectional crosstalk may generate key response elements within the interacting systems (the interactome) that influence anastomotic healing. Spatial and temporal dynamics need to be accounted for, as pathogen-host interactions at the precise site of anastomotic failure produce local environmental cues leading to microbial phenotype transformation linked to epithelial injury and healing. Agent-based modeling, an object-oriented computational modeling tool, is well suited to capture and synthesize these dynamic interactions. Here we use an agent-based model (ABM) to integrate the mechanisms of by which P. aeruginosa, a microorganism often present during anastomotic failure, responds to the microenvironment of epithelial injury and healing incorporating data derived from in vitro experiments. Methods: An ABM of epithelial wound healing was constructed using NetLogo. Computational agents representing individual epithelial cells were used to populate an in silico analog of an in vitro cell culture model, which included the culture media and soluble factors in the background. Rules governing agent behavior were adapted from known mechanisms of epithelial wound healing in the literature. The in silico epithelial monolayer was then damaged as would be done using a traditional scratch assay. A second agent layer representing P. aeruginosa bacteria was introduced, and bacterial activation at the wound site was modeled based on a putative mechanism involving nitric oxide, hypoxia-inducible factor-1α and adenosine. Simulations of hypoxia and radiation effects were also performed. Results: The ABM accurately reproduced epithelial wound healing dynamics. Activation of epithelial cells via ERK-1/2 signaling and EGF-R expression led to cell migration and spreading in order to heal the damage. Wound closure speed was calibrated to the known data based on the presence or absence of various factors such as EGF in the media. Addition of P. aeruginosa to the system demonstrated patterns of bacterial adherence similar to in vitro results, with associated inhibition of epithelial migration and healing. Hypoxia augmented migration, while radiation inhibited migration and increased bacterial adherence. Conclusions: Awareness of the importance of the host-microbe interactome adds a new level of complexity in understanding differences in anastomotic healing. Addressing this complexity will likely require representation of multi-factorial interactions at a level of resolution not currently possible. Dynamic knowledge representation using agent-based modeling may provide a means of increasing our resolution in visualizing mechanistic hypotheses and integrating them into a clinically relevant context.

The Stable Stationary Value of the Earth's Global Average Atmospheric Planck-Weighted Greenhouse-Gas Optical Thickness

By the line-by-line method, a computer program is used to analyze Earth atmospheric radiosonde data from hundreds of weather balloon observations. In terms of a quasi-all-sky protocol, fundamental infrared atmospheric radiative flux components are calculated: at the top boundary, the outgoing long wave radiation, the surface transmitted radiation, and the upward atmospheric emittance; at the bottom boundary, the downward atmospheric emittance. The partition of the outgoing long wave radiation into upward atmospheric emittance and surface transmitted radiation components is based on the accurate computation of the true greenhouse-gas optical thickness for the radiosonde data. New relationships among the flux components have been found and are used to construct a quasi-all-sky model of the earth's atmospheric energy transfer process. In the 1948–2008 time period the global average annual mean true greenhouse-gas optical thickness is found to be time-stationary. Simulated radiative no-feedback effects of measured actual CO2 change over the 61 years were calculated and found to be of magnitude easily detectable by the empirical data and analytical methods used. The data negate increase in CO2 in the atmosphere as a hypothetical cause for the apparently observed global warming. A hypothesis of significant positive feedback by water vapor effect on atmospheric infrared absorption is also negated by the observed measurements. Apparently major revision of the physics underlying the greenhouse effect is needed.

Radiation effects on Gaia CCDs, Modelling to mitigate the threat

This paper describes the damage occurring in CCDs exposed to solar radiation and explains its implications for the Gaia measurements by focusing on the astrometric instrument. It introduces the strategy that will be used in the Gaia data processing to mitigate the radiation induced effects, and presents CEMGA (CTI effects Models for Gaia) a multi-purpose platform which hosts different models that simulate radiation effects on CCDs.

Musculoskeletal Changes in Mice from 20–50 cGy of Simulated Galactic Cosmic Rays

On a mission to Mars, astronauts will be exposed to a complex mix of radiation from galactic cosmic rays. We have demonstrated a loss of bone mass from exposure to types of radiation relevant to space flight at doses of 1 and 2 Gy. The effects of space radiation on skeletal muscle, however, have not been investigated. To evaluate the effect of simulated galactic cosmic radiation on muscle fiber area and bone volume, we examined mice from a study in which brains were exposed to collimated iron-ion radiation. The collimator transmitted a complex mix of charged secondary particles to bone and muscle tissue that represented a low-fidelity simulation of the space radiation environment. Measured radiation doses of uncollimated secondary particles were 0.47 Gy at the proximal humerus, 0.24-0.31 Gy at the midbelly of the triceps brachii, and 0.18 Gy at the proximal tibia. Compared to nonirradiated controls, the proximal humerus of irradiated mice had a lower trabecular bone volume fraction, lower trabecular thickness, greater cortical porosity, and lower polar moment of inertia. The tibia showed no differences in any bone parameter. The triceps brachii of irradiated mice had fewer small-diameter fibers and more fibers containing central nuclei. These results demonstrate a negative effect on the skeletal muscle and bone systems of simulated galactic cosmic rays at a dose and LET range relevant to a Mars exploration mission. The presence of evidence of muscle remodeling highlights the need for further study.

Numerical simulation of high-energy neutron radiation effect of scintillation fiber

Due to their low cost, flexibility, and convenience for long distance data transfer, plastic scintillation fibers (PSF) have been increasingly used in building detectors or sensors for detecting various radiations and imaging. In this paper, GEANT4 Monte Carlo simulation tool was used to obtain some radiation effects of PSF under high-energy neutron irradiation. BCF-20, a plastic fiber material, produced by Saint-Gobain, was used in the simulation. The fiber consists of a core scintillating material of polystyrene and an acrylic outer cladding. Incident neutrons produce energy deposition in fiber through neutron induced recoil proton events. The relationships between energy deposition efficiency and fiber length, fiber radius and incident neutron energy are presented. The variation with those parameters and parameter selection are also analyzed.

Multi-Scale Simulation of Radiation Effects in Electronic Devices

As integrated circuits become smaller and more complex, it has become increasingly difficult to simulate their responses to radiation. The distance and time scales of relevance extend over orders of magnitude, requiring a multi-scale, hierarchical simulation approach. This paper demonstrates the use of multi-scale simulations to examine two radiation-related problems: enhanced low-dose-rate sensitivity (ELDRS) in bipolar transistors and single-event effects (SEE) in CMOS integrated circuits. Examples are included that demonstrate how information can be passed from simulation tools operating at one level of abstraction to those operating at higher levels, while maintaining accuracy and gaining insight.

Biological responses to the simulated Martian UV radiation of bacteriophages and isolated DNA

Mars is considered as a main target for astrobiologically relevant exploration programmes. In this work the effect of simulated Martian solar UV radiation was examined on bacteriophage T7 and on isolated T7 DNA. A decrease of the biological activity of phages, characteristic changes in the absorption spectrum and in the electrophoretic pattern of isolated DNA/phage and the decrease of the amount of PCR products were detected indicating damage of isolated and intraphage T7 DNA by UV radiation. Further mechanistic insights into the UV-induced formation of intraphage/isolated T7 DNA photoproducts were gained from the application of appropriate enzymatic digestion and neutral/alkaline agarose gel electrophoresis. Our results showed that intraphage DNA was about ten times more sensitive to simulated Martian UV radiation than isolated T7 DNA indicating the role of phage proteins in the DNA damage. Compared to solar UV radiation the total amount of DNA damage determined by QPCR was about ten times larger in isolated DNA and phage T7 as well, and the types of the DNA photoproducts were different, besides cyclobutane pyrimidine dimers (CPD), double-strand breaks (dsb), and single-strand breaks (ssb), DNA-protein cross-links were produced as well. Surprisingly, energy deposition as low as 4–6 eV corresponding to 200–400 nm range could induce significant amount of ssb and dsb in phage/isolated DNA (in phage the ratio of ssb/dsb was ≈23%/12% and ≈32%/19% in isolated DNA). 5–8% of the CPD, 3–5% of the AP (apurinic/apyrimidinic) sites were located in clusters in DNA/phage, suggesting that clustering of damage occur in the form of multiple damaged sites and these can have a high probability to produce strand breaks. The amount of total DNA damage in samples which were irradiated in Tris buffer was reduced by a factor ∼2, compared to samples in phosphate buffer, suggesting that some of the photoproducts were produced via radicals.

Geant4 Physics Processes for Microdosimetry Simulation: Design Foundation and Implementation of the First Set of Models

New physical processes specific for microdosimetry simulation are under development in the Geant4 Low Energy Electromagnetic package. The first set of models implemented for this purpose cover the interactions of electrons, protons and light ions in liquid water; they address a physics domain relevant to the simulation of radiation effects in biological systems, where water represents an important component. The design developed for effectively handling particle interactions down to a low energy scale and the physics models implemented in the first public release of the software are described.

Tests of Monte Carlo Independent Column Approximation in the ECHAM5 Atmospheric GCM

Abstract The Monte Carlo Independent Column Approximation (McICA) method for computing domain-average radiative fluxes allows a flexible treatment of unresolved cloud structure, and it is unbiased with respect to the full ICA, but its flux estimates contain conditional random noise. Here, tests of McICA in the ECHAM5 atmospheric GCM are reported. ECHAM5 provides an interesting test bed for McICA because it carries prognostic variables for the subgrid-scale probability distribution of total water content, which allows us to determine subgrid-scale cloud variability directly from the resolved-scale model variables. Three experiments with differing levels of radiative noise, each consisting of ten 6-yr runs, are performed to estimate the impact of McICA noise on simulated climate. In an experiment that attempted to deliberately maximize McICA noise, a systematic reduction in low cloud fraction occurred. For a more reasonable implementation of McICA, the impact of noise is very small, although statistically discernible. In terms of the impacts of noise, McICA appears to be a viable approach for use in ECHAM5. However, to improve the simulation of cloud radiative effects, realistic representation of both unresolved and resolved cloud structures is needed, which remains a challenging problem. Comparison of ECHAM5 data with a global cloud system–resolving model dataset and with International Satellite Cloud Climatology Project data suggested two problems related to unresolved cloud structures. First, ECHAM5 appears to underestimate subgrid-scale cloud variability. This problem seems partly related to the use of the beta distribution scheme for total water content in ECHAM5: in its current form, the scheme is unable to generate highly inhomogeneous clouds (relative standard deviation of condensate amount >1). Second, it appears that in ECHAM5, overcast cloud layers occur too frequently and partially cloudy layers too rarely. This problem is not unique to the beta distribution scheme; in fact, it is more pronounced when using an alternative, relative humidity–based cloud fraction scheme.

Regional modeling of Saharan dust events using LM‐MUSCAT: Model description and case studies

A new regional model system was developed for simulation of emission, transport, deposition, and radiative effects of Saharan desert aerosol within the framework of the Saharan Mineral Dust Experiment (SAMUM). For this the mesoscale meteorological model LM, a dust emission scheme and a transport model were coupled. To test the model performance, two major Saharan dust outbreaks directed to Europe in August and October 2001 are simulated. Comparisons with sounding data and 10‐m wind speeds from north African sites show that the LM provides reliable meteorological fields to describe the emission and near‐source transport of dust. As shown by comparisons with satellite observations, lidar profiles, and Sun photometer measurements at selected stations, the spatiotemporal evolution of the dust plume is reasonably well reproduced by the model. The predicted dust interacts with the LM radiation at solar and thermal wavelengths. Saharan dust causes a negative effect on the net radiative budget at the top of the atmosphere in the source regions and accounts for a reduction in 10‐m wind speeds. Thus it is responsible for a reduction in the dust production of up to about 50% during the October 2001 event.

Simplified radiative models for low-Mach number reactive flows

We introduce a class of numerical models for the simulation of radiative effects in low-Mach number reactive flows. These models are based on simplified P N approximations for radiative heat transfer, low-Mach asymptotic in the compressible flow, and reduced four-step chemical reaction for reacting species. The models presented here remove on one hand, acoustic wave propagation while retaining the compressibilty effects resulting from combustion and on the other hand, simplify the integro-differential equation for radiative transfer to a set of differential equations independent of the angle variable and compatible to those used for modelling flow and combustion. We briefly discuss the basic discretization methodology for the combined equations and its implementation in a modified projection method. We present validation computations for a two-dimensional methane/air flame in which the computational results are compared for nongray participating media.