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Energy Technology Data Exchange (ETDEWEB)

The results of this study show that Monte Carlo simulations of diffusion in homogeneous turbulence can be formulated in terms of the Eulerian space-time velocity autocorrelation function. Numerical results obtained using this approach agree with results obtained by Taylor (1921) using the Lagrangian autocorrelation function. Use was made of the equivalence of the Lagrangian and Eulerian Monte Carlo approaches to derive analytic relations between the Lagrangian integral time scale and the Eulerian integral space and time scales. These analytic results were verified by comparison to Monte Carlo simulations and to other theoretical results. They are in general agreement with many existing theories and semi-empirical relations.

Energy Technology Data Exchange (ETDEWEB)

Details of the interaction of photons with tissue phantoms are elucidated using Monte Carlo simulations. In particular, photon sampling volumes and photon pathlengths are determined for a variety of scattering and absorption parameters. The Monte Carlo simulations are specifically designed to model light delivery and collection geometries relevant to clinical applications of optical biopsy techniques. The Monte Carlo simulations assume that light is delivered and collected by two, nearly-adjacent optical fibers and take into account the numerical aperture of the fibers as well as reflectance and refraction at interfaces between different media. To determine the validity of the Monte Carlo simulations for modeling the interactions between the photons and the tissue phantom in these geometries, the simulations were ...

International Nuclear Information System (INIS)

Monte Carlo criticality calculations have been performed for over 50 years for reactor physics and criticality safety applications. With today's faster computers, these calculations are being carried out to greater precision (smaller uncertainties) in keff, and detailed distributions of power and reaction rates are being computed routinely. This paper provides a review of the fundamental theory of Monte Carlo criticality calculations, with guidance on practical methods for: (1) assuring convergence of both keff and the source distribution, (2) minimizing the bias in keff and reaction rate distributions, and (3) dealing with the under-prediction bias in uncertainties for keff and reaction rate distributions. (authors)

International Nuclear Information System (INIS)

We argue that the tachyons which exist in some string models are a signal of deconfinement. We compare the deconfinement temperature obtained from Monte Carlo calculations with some string models. (orig.).

Science.gov (United States)

... Peripherals: 1 VT100 terminal and 1 high-speed ... Customer in ASP time Queue data ME ... TREATMEN OF RANDOMNESS: Stochastic, Monte Carlo. ...

Energy Technology Data Exchange (ETDEWEB)

The Monte Carlo simulation method is applied to calculate the nucleon transfer part of the imaginary optical-model potential in colliding heavy ions. In the process of transfer of nucleons from one nucleus to the other, forward and backward neutrons and protons are treated separately by taking into consideration the effect of the Coulomb forces and the potential energy surfaces (driving forces). The Pauli exclusion principle is also incorporated properly in the calculation.

International Nuclear Information System (INIS)

Monte Carlo calculations performed to validate observed capture reaction rates of "1"2"9I and "2"3"7Np were in a reasonable agreement with experimental data obtained by the Joint Institute for Nuclear Research. The most significant discrepancy between the measurements and calculations (within a factor of 3) was observed for the NpO_2 sample and Pb target at 3.7 GeV proton energy

British Library Electronic Table of Contents (United Kingdom)

During the last few decades, accuracy in photon and electron radiotherapy has increased substantially. This is partly due to enhanced linear accelerator technology, providing more flexibility in field definition (e.g. the usage of computer-controlled dynamic multileaf collimators), which led to intensity modulated radiotherapy (IMRT). Important improvements have also been made in the treatment planning process, more specifically in the dose calculations. Originally, dose calculations relied heavily on analytic, semi-analytic and empirical algorithms. The more accurate convolution/superposition codes use pre-calculated Monte Carlo dose "kernels" partly accounting for tissue density heterogeneities. It is generally recognized that the Monte Carlo method is able to increase accuracy even furt...

International Nuclear Information System (INIS)

An ytterbium-169 high dose rate brachytherapy source, distinguished by an intensity-weighted average photon energy of 92.7 keV and a 32.015#+-#0.009 day half-life, is characterized in terms of the updated AAPM Task Group Report No. 43 specifications using the MCNP5 Monte Carlo computer code. In accordance with these specifications, the investigation included Monte Carlo simulations both in water and air with the in-air photon spectrum filtered to remove low-energy photons below 10 keV. TG-43 dosimetric data including S_K, D(r,#theta#), #LAMBDA#, g_L(r), F(r,#theta#), #phi#_a_n(r), and #phi#_a_n were calculated and statistical uncertainties in these parameters were derived and calculated in the appendix.

International Nuclear Information System (INIS)

A Monte Carlo simulation of the vacuum Bianchi type-IX (mixmaster) cosmology yields a significant correlation between large universe volume and high anisotropy. An analog of the model's chaotic classical behavior is seen in the break up of the universe wave function at large volume into fingers in the corners of the minisuperspace anisotropy potential.

UK PubMed Central (United Kingdom)

The reference medium for brachytherapy dose measurements is water. Accuracy of dose measurements of brachytherapy sources is critically dependent on precise measurement of the source–detector...Full Text Available

Energy Technology Data Exchange (ETDEWEB)

Initial results obtained with a Monte Carlo computer program designed to link initial physical events in irradiated liquid water with subsequent chemical and biological events are presented. 10 refs., 4 figs., 3 tabs.

UK PubMed Central (United Kingdom)

BackgroundPlotless density estimators are those that are based on distance measures rather than counts per unit area (quadrats or plots) to estimate the density of some usually stationary...Full Text Available

Energy Technology Data Exchange (ETDEWEB)

A method, which estimates the lightning performance of high voltage transmission lines based on the Monte-Carlo simulation technique, is described in this paper. The average number of faults which occur in a transmission line, dividing them in single-phase and three-phase faults, as well as the average grounding resistances of the transmission lines are calculated. The method is applied, on several operating Greek transmission lines, showing good correlation between predicted and field observation results. The proposed method can be used as a useful tool in the design of electric power systems, aiding in the right insulation dimensioning of a transmission line.(author)

International Nuclear Information System (INIS)

A Monte Carlo method called transient curve fitting method was developed to calculate a eigenvalues by first simulating the existing neutrons and precursors in the system, then calculating the Eigen-distribution of neutron flux and calculating the a eigenvalues using the transient results based on the Eigen-distribution by the code TMCC. The results of this method are tested by calculating Godiva Benchmark problems and they agree well with the benchmark results. Then the reasonable results of Subcritical Facility in Tsinghua University are given by TMCC, and the results are compared with the experimental results measured by Rossi-a method. Even in the deep subcritical cases, the method can give results consistent with experimental results. (authors)

Energy Technology Data Exchange (ETDEWEB)

This paper presents calculations of the {sup 252}Cf-source-driven noise analysis measurements for subcritical highly enriched uranium metal cylinders using the Monte Carlo code MCNP-DSP. This code directly calculates the noise analysis data from the {sup 252}Cf- source-driven noise analysis method for both neutron and gamma ray detectors. Direct calculation of experimental observables by the Monte Carlo method allows for the benchmarking of the calculational model and the cross sections and for determining the bias in the calculation.

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Real time neutron radiography has been used to study the dynamic behavior of two phase flow and measure the time averaged vapor fraction in a heated metal tube containing boiling steam water operating at up to 15 bar pressure. The neutron radiographic technique is non-intrusive and requires no special transparent window region. This is the first time this technique has been used in an electrically heated pressurized flow loop. This unique experimental method offers the opportunity to observe and record on videotape, flow patterns and transient behavior of two phase flow inside opaque containers without disturbing the environment. In this study the test sections consisted of stainless steel tubes with a 1.27 cm outer diameter and wall thicknesses of 0.084 cm and 0.124 cm. The experiments were carried out at the Pennsylvania State University 1 megawatt TRIGA reactor facility utilizing a Precise Optics neutron radiography camera. The inlet water temperature to the ...

International Nuclear Information System (INIS)

Real time neutron radiography has been used to study the dynamic behavior of two phase flow and measure the time averaged vapor fraction in a heated metal tube containing boiling steam water operating at up to 15 bar pressure. The neutron radiographic technique is non-intrusive and requires no special transparent window region. This is the first time this technique has been used in an electrically heated pressurized flow loop. This unique experimental method offers the opportunity to observe and record on videotape, flow patterns and transient behavior of two phase flow inside opaque containers without disturbing the environment. In this study the test sections consisted of stainless steel tubes with a 1.27 cm outer diameter and wall thicknesses of 0.084 cm and 0.124 cm. The experiments were carried out at the Pennsylvania State University 1 megawatt TRIGA reactor facility utilizing a Precise Optics neutron radiography camera. The inlet water temperature to the ...

Energy Technology Data Exchange (ETDEWEB)

Molecular simulation aims at simulating particles in interaction, describing a physico-chemical system. When considering Markov Chain Monte Carlo sampling in this context, we often meet the same problem of statistical efficiency as with Molecular Dynamics for the simulation of complex molecules (polymers for example). The search for a correct sampling of the space of possible configurations with respect to the Boltzmann-Gibbs distribution is directly related to the statistical efficiency of such algorithms (i.e. the ability of rapidly providing uncorrelated states covering all the configuration space). We investigated how to improve this efficiency with the help of Artificial Evolution (AE). AE algorithms form a class of stochastic optimization algorithms inspired by Darwinian evolution. Efficiency measures that can be turned into efficiency criteria have been first searched before identifying parameters that could be optimized. Relative ...

International Nuclear Information System (INIS)

The process of ensuring the quality of computer codes can be very time consuming and expensive. The Oak Ridge National Laboratory (ORNL) Monte Carlo codes all predate the existence of quality assurance (QA) standards and configuration control. The number of person-years and the amount of money spent on code development make it impossible to adhere strictly to all the current requirements. At ORNL, the Nuclear Engineering Applications Section of the Computing Applications Division is responsible for the development, maintenance, and application of the Monte Carlo codes MORSE and KENO. The KENO code is used for doing criticality analyses; the MORSE code, which has two official versions, CGA and SGC, is used for radiation transport analyses. Because KENO and MORSE were very thoroughly checked out over the many years of extensive use both in the United States and in the international community, the existing ...

Energy Technology Data Exchange (ETDEWEB)

This paper reports on three-dimensional continuous-energy coupled neutron-gamma Monte Carlo models of the Advanced Neutron Source (ANS) final preconceptual and conceptual reference core designs developed using the Monte Carlo Neutron and Photon transport code (MCNP) Version 3b. These models contain the reactor core with control rods, the heavy water reflector tank with shutdown rods and some beam tubes, and the outer light water pool. Eighty homogenized fuel zones per fuel element are used to represent the radial and axial {sup 235}U fuel distribution. These models are the most sophisticated, physically accurate reactor physics models of the ANS currently available. The use of MCNP methods and applications to the ANS are demonstrated. Beam tube studies, coolant voiding studies, and many criticality studies have already been performed, as have studies with variance reduction techniques. In comparison ...

Energy Technology Data Exchange (ETDEWEB)

The technical feasibility of the solar carbothermal reduction of ZnO has been successfully demonstrated in a pilot plant. The economics of this process is addressed by means of a single sensitivity analysis and a Monte-Carlo risk analysis. A medium-term and a long-term scenario have been investigated, each for a 5 and a 30 MW{sub th} plant. For a discount rate of 15% the zinc production costs vary between 482 and 245 $/t for the medium-term scenario and between 312 and 146 $/t for the long-term scenario, respectively. These costs do not account for the zinc oxide input material. In addition, a risk analysis was conducted for the 30 MW{sub th} long-term scenario. For each input parameter, a probability distribution was estimated and the probability distribution of the zinc production cost was calculated by means of a Monte-Carlo method. The expected mean zinc production costs vary from 95 $/t for a discount rate of 0%-286 $/t for a discount rate ...

CERN Document Server

We demonstrate the use of a variational method to determine a quantitative lower bound on the rate of convergence of Markov Chain Monte Carlo (MCMC) algorithms as a function of the target density and proposal density. The bound relies on approximating the second largest eigenvalue in the spectrum of the MCMC operator using a variational principle and the approach is applicable to problems with continuous state spaces. We apply the method to one dimensional examples with Gaussian and quartic target densities, and we contrast the performance of the basic Metropolis-Hastings algorithms with a ``smart'' variant that incorporates gradient information into the trial moves. We find that the variational method agrees quite closely with numerical simulations. We also see that the smart MCMC algorithm often fails to converge geometrically in the tails of the target density except in the simplest case we examine, and even then care must be taken to choose ...

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This study presents results from Monte Carlo radiation transport calculations aimed at characterizing a novel methodology being developed to detect partial defects in Pressurized Water Reactor (PWR) spent fuel assemblies (SFAs). The methodology uses a combination of measured neutron and gamma fields inside a spent fuel assembly in an in-situ condition where no movement of the fuel assembly is required. Previous studies performed on single isolated assemblies resulted in a unique base signature that would change when some of the fuel in the assembly is replaced with dummy fuel. These studies indicate that this signature is still valid in the in-situ condition enhancing the prospect of building a practical tool, Partial Defect Detector (PDET), which can be used in the field for partial defect detection.

CERN Document Server

An algorithm for creating synthetic telescope images of Smoothed Particle Hydrodynamics (SPH) density fields is presented, which utilises the adaptive nature of the SPH formalism in full. The imaging process uses Monte Carlo Radiative Transfer (MCRT) methods to model the scattering and absorption of photon packets in the density field, which then exit the system and are captured on a pixelated image plane, creating a 2D image (or a 3D datacube, if the photons are also binned by their wavelength). The algorithm is implemented on the density field directly: no gridding of the field is required, allowing the density field to be described to an identical level of accuracy as the simulations that generated it. Some applications of the method to star and planet formation simulations are presented to illustrate the advantages of this new technique, and suggestions as to how this framework could support a Radiative Equilibrium algorithm are also given ...

International Nuclear Information System (INIS)

The MCNPE-BO and MCNP4 Monte Carlo electron-photon codes were used to calculate the dose equivalent per unit fluence at various depths in tissue-equivalent slab phantoms for broad parallel beams of monoenergetic electrons with energies from 50 keV to 10 MeV. The study was carried out in the framework of the activities of a ICRP/ICRU Joint Task Group with the support of EURADOS WG4 (Numerical Dosimetry). Some preliminary results and comparisons as well as a general discussion on the performances of the codes are presented, demonstrating quite a satisfactory agreement among the results obtained using the two codes and those of other authors. (author).

International Nuclear Information System (INIS)

The aim of this work was to compare dose calculation algorithm results at orthovoltage energies for a phantom composed of a bone slab in water. The calculation methods investigated were: no correction, ETAR, Batho, convolution/superposition and Monte Carlo. All algorithms calculated depth dose curves in a water phantom within 4% of experiment. However in the bone phantom, differences of over 40% between the No Correction / ETAR / Batho / Convolution and Monte Carlo results in the 1 cm thick bone slab were observed. These differences are predominantly because the algorithms do not account for the differing atomic number of the bone compared to water The increased dose to bone and the tissue adjacent to the bone interface should be considered when treating with orthovoltage photons. Copyright (1998) Australasian Physical and Engineering Sciences in Medicine

International Nuclear Information System (INIS)

An integrated beam optics-nuclear processes framework is essential for accurate simulation of fragment separator beam dynamics. The code COSY INFINITY provides powerful differential algebraic methods for modeling and beam dynamics simulations in absence of beam-material interactions. However, these interactions are key for accurately simulating the dynamics of heavy ion fragmentation and fission. We have developed an extended version of the code that includes these interactions, and a set of new tools that allow efficient and accurate particle transport: by transfer map in vacuum and by Monte Carlo methods in materials. The new framework is presented, along with several examples from a preliminary layout of a fragment separator for a facility for rare isotope beams.

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The electrogeometric model cannot consider the influence of some parameters on the screening of the wire conductor of the H.V. lines. For analysing the influence of these parameters (the conductor potential, the influence of the distance from phase conductor to earth wire, the influence of the reducing factor of the striking earth distance, the earth slope, etc.), the Monte Carlo method is preferable. The influence of the earth slope on the screening effect of the wire conductor for different conditions is presented in this paper. (author)

Energy Technology Data Exchange (ETDEWEB)

Previous models and evaluation techniques based on the Monte Carlo simulation for the reliability assessment of mixed hydrothermal generation systems are extended. Models for reservoirs on multiple rivers and pumped storage plants are developed. Operating and water management policies are extended to include the relative economical effects of operating alternative sources of generation. These effects and the benefits are described and discussed using an extended IEEE reliability test system. (Author).

Energy Technology Data Exchange (ETDEWEB)

A Monte Carlo simulation of the vacuum Bianchi type-IX (mixmaster) cosmology yields a significant correlation between large universe volume and high anisotropy. An analog of the model's chaotic classical behavior is seen in the break up of the universe wave function at large volume into fingers in the corners of the minisuperspace anisotropy potential.

Science.gov (United States)

The Milstar communications satellite system will provide secure antijam communication capabilities for DOD operations into the next century. In order to accomplish this task, the Milstar system will employ precise timekeeping on its satellites and at its ground control stations. The constellation will consist of four satellites in geosynchronous orbit, each carrying a set of four rubidium (Rb) atomic clocks. Several times a day, during normal operation, the Mission Control Element (MCE) will collect timing information from the constellation, and after several days use this information to update the time and frequency of the satellite clocks. The MCE will maintain precise time with a cesium (Cs) atomic clock, synchronized to UTC(USNO) via a GPS receiver. We have developed a Monte Carlo simulation of Milstar's space segment timekeeping. The simulation includes the effects of: uplink/downlink time transfer noise; satellite crosslink time transfer ...

International Nuclear Information System (INIS)

The status of Monte Carlo system for the simulation of Bremsstrahlung in arbitrary decays and for the decay itself of #tau# -lepton is reviewed. During the last #tau# -lepton conference in 2010 several developments of the last two years have been presented: (i) For the TAUOLA Monte Carlo generator of #tau# -lepton decays, automated and simultaneous use of many versions of form-factors for the calculation of optional weights for fits was developed and checked to work in Belle and BaBar software environment. On-going work on alternative parameterizations of hadronic decays is presented too. (ii) The TAUOLA universal interface based on HepMC (the C++ event record) is now public. A similar interface for PHOTOS is now also public. (iii) Extension of PHOTOS Monte Carlo for QED Bremsstrahlung in decays featuring kernels based on complete first order matrix element are ...

International Nuclear Information System (INIS)

The purpose of this work was to study and quantify the differences in dose distributions computed with some of the newest dose calculation algorithms available in commercial planning systems. The study was done for clinical cases originally calculated with pencil beam convolution (PBC) where large density inhomogeneities were present. Three other dose algorithms were used: a pencil beam like algorithm, the anisotropic analytic algorithm (AAA), a convolution superposition algorithm, collapsed cone convolution (CCC), and a Monte Carlo program, voxel Monte Carlo (VMC++). The dose calculation algorithms were compared under static field irradiations at 6 MV and 15 MV using multileaf collimators and hard wedges where necessary. Five clinical cases were studied: three lung and two breast cases. We found that, in terms of accuracy, the CCC algorithm performed better overall than AAA compared to VMC++, but AAA ...

International Nuclear Information System (INIS)

The Monte Carlo transport codes LAHET and MCNP were used to calculate energy fluence spectra at three neutron therapy facilities. The results compare very favourably with measured data. Kerma spectra and the ratio of ICRU muscle tissue kerma to A-150 kerma, along the carbon to oxygen kerma ratio, were determined. Absorbed dose rate calculations are in reasonable agreement with measured values. Use of these codes to study modifications to existing therapy beams is briefly discussed. (author).

International Nuclear Information System (INIS)

We present our plans for a Monte-Carlo code simulating all possible combinations of (electromagnetic) interactions between colliding electron, positron, and both high-energy and laser photon beams, based, on the ABEL code for beam-beam interaction. The implementation and first results for the laser-e"- interaction are described.

Energy Technology Data Exchange (ETDEWEB)

The theory of neutron moderation and spectroscopy are briefly reviewed, and moderators that are useful for Bonner sphere spectrometers are discussed. The choice of the neutron detector for a Bonner sphere spectrometer is examined. Spectral deconvolution methods are briefly reviewed, including derivative, parametric, quadrature, and Monte Carlo methods. Calibration is then discussed. (LEW)

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A model has been developed to predict the chemical composition of lakes that form in pyrite-bearing open-pit mines. Pyrite oxidation in wall rock releases sulfuric acid and metals, which mix with ground waters in the lake. Aqueous metal concentrations are calculated using MINTEQA2.

International Nuclear Information System (INIS)

The Accelerator Transmutation Waste System is under development at the Los Alamos National Laboratory. The goal is to perform an independent verification of the feasibility of actinide and long-lived fission product burning in this system. The authors' work is divided into five tasks: (a) production of an actinide and long-lived fission product cross section library from JEF 2.2; (b) simulation using MCNP and KENO IV Monte Carlo codes, of the Accelerator Transmutation Waste System configurations existing in literature; (c) validation of HETC Monte Carlo code (production of spallation source); (d) validation of the cross sections by comparison of Keff and reaction rate results, calculated with MNCP and KENO IV, with experimental benchmarks and intercomparison between the authors' calculations of a PWR unit cell and the computations carried out with various codes and cross section libraries (NEACRP ...

CERN Document Server

One of the most active areas of physics in the last decades has been that of critical phenomena, and Monte Carlo simulations have played an important role as a guide for the validation and prediction of system properties close to the critical points. The kind of phase transitions occurring for the Betts lattice (lattice constructed removing 1/7 of the sites from the triangular lattice) have been studied before with the Potts model for the values q=3, ferromagnetic and antiferromagnetic regime. Here, we add up to this research line the ferromagnetic case for q=4 and 5. In the first case, the critical exponents are estimated for the second order transition, whereas for the latter case the histogram method is applied for the occurring first order transition. Additionally, Domany's Monte Carlo based clustering technique mainly used to group genes similar in their expression levels is reviewed. Finally, a ...

International Nuclear Information System (INIS)

We calculate parity-dependent level densities for the even-even isotopes "5"8","6"2","6"6Fe and "5"8Ni and the odd-A nuclei "5"9Ni and "6"5Fe using the shell model Monte Carlo method. We perform these calculations in the complete fp-gds shell-model space using a pairing+quadrupole residual interaction. We find that, due to pairing of identical nucleons, the low-energy spectrum is dominated by positive parity states. Although these pairs break at around the same excitation energy in all nuclei, the energy dependence of the ratio of negative-to-positive parity level densities depends strongly on the particular nucleus of interest. We find equilibration of both parities at noticeably lower excitation energies for the odd-A nuclei "5"9Ni and "6"5Fe than for the neighboring even-even nuclei "5"8Ni and "6"6Fe.

International Nuclear Information System (INIS)

High resolution Monte-Carlo simulations show that the neutron spectrum, fuel burnup and fuel temperature feedback effect of a PWR core loaded with Thoria-based fuel (Th/Pu-O_2) do not significantly differ from the MOX fuelled one due to the similar neutronic characteristics of both fertile materials (Th-232, U-238). The core physics of this fuel variant is characterized by an enhanced moderator/void temperature coefficient (by factor 2.4) and high incineration rate for Pu (approx. 60 %). A PWR core loaded with the Molybdenum-based inert matrix fuel (IMF) - in contrast to MOX-, shows a harder spectrum, resulting in small temperature coefficients of reactivity and particularly in a higher fuel depletion rate as well as an enhanced TRU reduction performance. The incineration of Pu amounts to 46 % resulting, in turn, in generation of minor actinides of about 10 % of the total Pu consumption. The higher excess reactivity resulting from the initial Pu contents is ...

Energy Technology Data Exchange (ETDEWEB)

A technique capable of measuring the electron energy fluence spectra in a scattering medium was designed. These measurements were performed by setting a bremsstrahlung conversion target on the surface of a phantom, at an intermediate depth, and at a depth equal to electron mean range. The bremsstrahlung produced by the deceleration of electrons in the target was passed through an air channel in the phantom and passed forward by a pinhole collimator into a Na(Tl) detector. The measured pulse height data were unfolded to correct for the distortion of the spectrometer system by using the FORIST unfolding code. The unfolded bremsstrahlung spectra represent the electron energy fluence spectra convolution with the bremsstrahlung produced in the target. To generate the electron energy fluence spectra, the unfolded bremsstrahlung spectra were deconvoluted by using the MAZE2 unfolding code. CYLTRAN, a coupled electron-photon Monte Carlo transport code, ...

International Nuclear Information System (INIS)

In this paper, we report kinetic Monte Carlo study on the diffusion behavior of boron in silicon crystal, more particularly on the transient enhanced diffusion (TED) of boron in silicon during implantation and annealing. Firstly, the accuracy of our KMC code was verified by investigating the time evolutionary behavior of interstitial (I) and vacancy (V) when a silicon substrate is implanted with silicon dose with an energy of 10 keV and with a dose of 1 X 10"1"4 ions/cm"2. To investigate the influence of native defects (I, V) on boron diffusion, a single and multi boron markers grown by MBE were employed. The simulation results revealed that the precursor of boron cluster (BI_2) is dominant at the initial stage of annealing, which explains the boron TED phenomenon in terms of the concentration of boron complexes and I, V clusters, respectively. The formation of #left brace#311#right brace# defects and dislocation loop were observed from the ...

CERN Document Server

Monte Carlo calculations using the codes PENELOPE and GEANT4 have been performed to characterize the dosimetric parameters of the new 20 mm long catheter based $^{32}$P beta source manufactured by Guidant Corporation. The dose distribution along the transverse axis and the two dimensional dose rate table have been calculated. Also, the dose rate at the reference point, the radial dose function and the anisotropy function were evaluated according to the adapted TG-60 formalism for cylindrical sources. PENELOPE and GEANT4 codes were first verified against previous results corresponding to the old 27 mm Guidant $^{32}$P beta source. The dose rate at the reference point for the unsheathed 27 mm source in water was calculated to be $0.215 \\pm 0.001$ cGy s$^{-1}$ mCi$^{-1}$, for PENELOPE, and $0.2312 \\pm 0.0008$ cGy s$^{-1}$ mCi$^{-1}$, for GEANT4. For the unsheathed 20 mm source these values were $0.2908 \\pm 0.0009$ cGy s$^{-1}$ mCi$^{-1}$ and ...

Science.gov (United States)

In this paper we consider the adsorption of argon on the surface of graphitized thermal carbon black and in slit pores at temperatures ranging from subcritical to supercritical conditions by the method of grand canonical Monte Carlo simulation. Attention is paid to the variation of the adsorbed density when the temperature crosses the critical point. The behavior of the adsorbed density versus pressure (bulk density) shows interesting behavior at temperatures in the vicinity of and those above the critical point and also at extremely high pressures. Isotherms at temperatures greater than the critical temperature exhibit a clear maximum, and near the critical temperature this maximum is a very sharp spike. Under the supercritical conditions and very high pressure the excess of adsorbed density decreases towards zero value for a graphite surface, while for slit pores negative excess density is possible at extremely high pressures. For imperfect ...

CERN Document Server

Brachytherapy is a radiotherapeutic modality that makes use of radionuclides to deliver a high radiation dose to a well-defined volume while sparing surrounding healthy structures. At the National Institute for Cancer Research of Genova a High Dose Rate remote afterloading system provides Ir(192) endocavitary brachytherapy treatments. We studied the possibility to use the Geant4 Monte Carlo simulation toolkit in brachytherapy for calculation of complex physical parameters, not directly available by experiment al measurements, used in treatment planning dose deposition models.

British Library Electronic Table of Contents (United Kingdom)

The present paper considers the evaluation of timber structures with the focus on robustness due to connection ductility. The robustness analysis is based on the structural reliability framework applied to a simplified mechanical system. The structural timber system is depicted as a parallel system. An evaluation method of the ductile behaviour is introduced. For different ductile behaviours, the system reliability is estimated based on Monte Carlo simulation. A correlation between the strength of the structural elements is introduced. The results indicate that the reliability of a structural timber system can be significantly increased due to the ductile behavior.

International Nuclear Information System (INIS)

Tests for the applicability of a CFD (Computational Fluid Dynamics) code for simulating activity transport in PNA (Pulsed Neutron Activation) fluid measurements have been performed. The CFD code was combined with a Monte Carlo code used for the calculation of the initial activity distribution. The results from the calculations show that it is possible to use CFD for calculation of the activity distribution in PNA. The mainly qualitative results in this work are encouraging and suggest further work. In the continuation of this work a response function for the gamma detector will be calculated so that a PNA time spectrum can be simulated. A more accurate comparison with experimental data can then be performed

International Nuclear Information System (INIS)

An important unresolved issue in outcomes analysis for lung complications is the effect of poor or completely lacking heterogeneity corrections in previously archived treatment plans. To estimate this effect, we developed a novel method based on Monte Carlo (MC) dose calculations which can be applied retrospectively to RTOG/AAPM-style archived treatment plans (ATP). We applied this method to 218 archived nonsmall cell lung cancer lung treatment plans that were originally calculated either without heterogeneity corrections or with primitive corrections. To retrospectively specify beam weights and wedges, beams were broken into Monte Carlo-generated beamlets, simulated using the VMC++ code, and mathematical optimization was used to match the archived water-based dose distributions. The derived beam weights (and any wedge effects) were then applied to Monte Carlo ...

International Nuclear Information System (INIS)

Organ and tissue doses and integral doses in patients due to diagnostic x-ray examinations of the chest and of the head will be presented. These data have been obtained by measuring the dose distributions in man phantoms by LiF-dosimetry. The data will be compared with data obtained by Monte-Carlo calculations. To obtain average organ doses for a special type of examination for the population or for a specified subpopulation in the variation of the exposure, data due to the different techniques used by the different radiologists has to be known. Such data will be presented. The results of the investigation will be discussed in connection with the concept of the 'somatic significant.

Energy Technology Data Exchange (ETDEWEB)

Recent developments in the physical model of 1 MeV to 100 TeV hadron and lepton interactions with nuclei and atoms are described. These include a new nuclear cross section library, a model for soft pion production, the cascade-exciton model, the dual parton model, deuteron-nucleus and neutrino-nucleus interaction models, detailed description of mu, pi and anti p absorption and a unified treatment of muon and charged hadron electromagnetic interactions with matter. New algorithms are implemented into the MARS13(98) Monte Carlo code and benchmarked against experimental data. The code capabilities to simulate cascades and generate a variety of results in complex media have been also enhanced.

British Library Electronic Table of Contents (United Kingdom)

The adsorption and corrosion inhibition behavior of three selected thiosemicarbazone derivatives, namely 3-pyridinecarboxaldehyde thiosemicarbazone (META), isonicotinaldehyde thiosemicarbazone (PARA) and 2-pyridinecarboxaldehyde thiosemicarbazone (ORTHO) at the nickel surface were studied electrochemically by Tafel and impedance methods and computationally by carrying out Monte Carlo searches of configurational space on nickel/thiosemicarbazone derivative system. Electrochemical measurements showed that the inhibition efficiency of these compounds increased with increase in their concentration. The recorded inhibition efficiencies of the three tested thiosemicarbazone increase in the order: META>PARA>ORTHO. Polarization studies showed that these compounds act as mixed-type inhibitors for n...

International Nuclear Information System (INIS)

The CyberKnife Robotic Radiosurgery System (Accuracy Incorporated, Sunnyvale, CA, USA) is used worldwide to treat tumors and neurological disorders anywhere in the body with sub-millimetre beam delivery accuracy. Accuracy has developed a number of new technologies in recent years to enhance the treatment of cancer patients. Such new technologies include a fast Monte Carlo Dose Calculation algorithm, Sequential Optimization dose planning, the IrisTM Variable Aperture Collimator, an 800 MU/min Linear Accelerator, and Optimized Path Traversal. These technologies enable physicists and physicians to plan treatments quickly and easily and deliver them with unrivalled accuracy and precision

Energy Technology Data Exchange (ETDEWEB)

The diamond norm measures the distance between two quantum channels. From an operational viewpoint, this norm measures how well we can distinguish between two channels by applying them to the input states of arbitrarily large dimensions. In this paper, we show that the diamond norm can be conveniently, and in a physically transparent way, computed by means of a Monte Carlo algorithm based on the Fano representation of quantum states and quantum operations. The effectiveness of this algorithm is illustrated for several single-qubit quantum channels.

CERN Document Server

We provide a both qualitative and quantitative comparison among different approaches aimed to solve the problem of non-linear diffusive acceleration of particles at shocks. In particular, we show that state-of-the-art models (numerical, Monte Carlo and semi-analytical), even if based on different physical assumptions and implementations, for typical environmental parameters lead to very consistent results in terms of shock hydrodynamics, cosmic ray spectrum and also escaping flux spectrum and anisotropy. Strong points and limits of each approach are also discussed, as a function of the problem one wants to study.

Energy Technology Data Exchange (ETDEWEB)

We made Basic designs of neutron guide, choppers, and detectors in order to optimize the design parameters of DC-TOF to be built in the HANARO Cold Neutron Guide Hall. In addition, we calculated the expected performance of DC-TOF using Monte Carlo simulations and evaluated the properties of neutron beam. Based on the results we obtained, we have compared the expected performance of the DC-TOF with those of existing instruments overseas. In conclusion, we believe that we will be able to construct the DC-TOF at HANARO as one of the best instruments of its kinds and it will become an invaluable instrument to researchers in the related field.

International Nuclear Information System (INIS)

We have developed a new type personal dosemeter by using a B-10 doped silicon p-n junction detector with a polyethylene radiator and a polyethylene moderator. The purpose of this study was to develop a real time neutron dosemeter with a nearly flat response in the energy range from thermal to 15 MeV and low angular dependence to the incident neutron direction. The neutron response of the dosemeter was obtained with the Monte Carlo calculation and the monoenergetic neutron experiment in a free air field and also under a condition attached on a phantom.

International Nuclear Information System (INIS)

Accurate modeling of system response and scatter distribution is crucial for image reconstruction in emission tomography. Monte Carlo simulations are very well suited to calculate these quantities. However, Monte Carlo simulations are also slow and many simulated counts are needed to provide a sufficiently exact estimate of the detection probabilities. In order to overcome these problems, we propose to split the simulation into two parts, the detection system and the object to be imaged (the patient). A so-called 'virtual boundary' that separates these two parts is introduced. Within the patient, particles are simulated conventionally. Whenever a photon reaches the virtual boundary, its detection probability is calculated analytically by evaluating a multi-dimensional B-spline that depends on the photon position, direction and energy. The unknown B-spline knot values that define this B-spline are fixed ...

International Nuclear Information System (INIS)

A Siemens Mevatron KV2 accelerator installed at the Royal Adelaide Hospital employs cylindrical solid-walled electron cones for some electron collimation. The cones being used at present result in treatment fields that do not always conform with the International Electrotechnical Commission (IEC) Standards (particularly at high energies). The aim of this project was to simulate the existing cones using Monte Carlo methods in order to evaluate potential cone modifications required to overcome the field irregularities. Simulations were performed using the EGS4 (Electron Gamma Shower version 4, distribution II) Monte Carlo code installed on a DEC Alpha workstation at the University of South Australia. To rigorously simulate the existing electron cones it was necessary to also simulate various components within the treatment head of the linear accelerator. Results of simulations for existing cones were ...

Energy Technology Data Exchange (ETDEWEB)

As for Wolsung NPP unit 1, radiation shielding analysis was performed by using neutron diffusion codes, one-dimensional discrete ordinates code ANISN, and analytical methods. But for Wolsung NPP unit 2, 3, and 4, two-dimensional discrete ordinates code DOT substituted for neutron diffusion codes. In other words, the method of analysis and computer codes used for radiation shielding of CANDU 6 type reactor have been improved. Recently Monte Carlo MCNP code has been widely utilized in the field of radiation physics and other radiation related areas because it can describe an object sophisticately by use of three-dimensional modelling and can adopt continuous energy cross-section library. Nowadays Monte Carlo method has been reported to be competitive to discrete ordinate method in the field of radiation shielding and the former has been known to be superior to the latter for complex geometry problem. ...

International Nuclear Information System (INIS)

The hard-sphere radial distribution functions, g_H_S(r/d,#eta#), for the face-centered cubic and hexagonal close-packed phases have been computed by the Monte Carlo method at nine values of the packing fraction, #eta#[=(#pi#/6)#rho#d"3], ranging from 4% below the melting density to 99% of the close-packed density. The Monte Carlo data are used to improve available analytic expressions for g_H_S(r/d,#eta#). By utilizing the new g_H_S(r/d,#eta#) in the Henderson and Grundke method [J. Chem. Phys. 63, 601 (1975)], we next derive an expression for y_H_S(r/d,#eta#) [=g_H_S(r/d)exp#left brace##beta#V_H_S(r)#right brace#] inside the hard-sphere diameter, d. These expressions are employed in a solid-state perturbation theory [J. Chem. Phys. 84, 4547 (1986)] to compute solid-state and melting properties of the Lennard-Jones and inverse-power potentials. Results are in close agreement with ...

Science.gov (United States)

In 2002 and again in 2003, an investigative journalist unit at ABC News transported a 6.8 kilogram metallic slug of depleted uranium (DU) via shipping container from Istanbul, Turkey to Brooklyn, NY and from Jakarta, Indonesia to Long Beach, CA. Targeted inspection of these shipping containers by Department of Homeland Security (DHS) personnel, included the use of gamma-ray imaging, portal monitors and hand-held radiation detectors, did not uncover the hidden DU. Monte Carlo analysis of the gamma-ray intensity and spectrum of a DU slug and one consisting of highly-enriched uranium (HEU) showed that DU was a proper surrogate for testing the ability of DHS to detect the illicit transport of HEU. Our analysis using MCNP-5 illustrated the ease of fully shielding an HEU sample to avoid detection. The assembly of an Improvised Nuclear Device (IND) -- a crude atomic bomb -- from sub-critical pieces of HEU metal was then examined via ...

International Nuclear Information System (INIS)

Using Monte Carlo simulation and the convolution/superposition algorithm, this work examines percent depth dose curves of the central axis in an acrylic phantom (20x20x20 cm"3) with variously sized air cavities (20x20x1.0, 20x20x2.0, 20x20x3.0, 20x20x4.0 and 20x20x4.95 cm"3 for study of longitudinal electron disequilibrium (ED) and 3.6x3.6x4.95, 4.5x4.5x4.95, 5.4x5.4x4.95 and 20x20x4.95 cm"3 for study of lateral ED). Radiochromic film samples are also measured to verify the Monte Carlo results. The Monte Carlo simulation is performed using OMEGA/BEAM and DOSXYZ codes, and the convolution/superposition calculation relies on an ADAC commercial treatment planning system. Underestimating the dose kernel expansion leads to overestimating the dose of what was found in the air cavity of ED using the convolution/superposition algorithm. Consequently, the dose in the ...

Science.gov (United States)

vibration Isolation system for the camera. ... to further define the response of the camera vibration isolation system. These ...

International Nuclear Information System (INIS)

The goal of this work is to present a systematic Monte Carlo validation study on the clinical implementation of the enhanced dynamic wedges (EDWs) into the Pinnacle"3 (Philips Medical Systems, Fitchburg, WI) treatment planning system (TPS) and QA procedures for patient plan verification treated with EDWs. Modeling of EDW beams in the Pinnacle"3 TPS, which employs a collapsed-cone convolution superposition (CCCS) dose model, was based on a combination of measured open-beam data and the 'Golden Segmented Treatment Table' (GSTT) provided by Varian for each photon beam energy. To validate EDW models, dose profiles of 6 and 10 MV photon beams from a Clinac 2100 C/D were measured in virtual water at depths from near-surface to 30 cm for a wide range of field sizes and wedge angles using the Profiler 2 (Sun Nuclear Corporation, Melbourne, FL) diode array system. The EDW output factors (EDWOFs) for square fields from 4 to 20 cm wide were measured in ...

British Library Electronic Table of Contents (United Kingdom)

Solar cavity receiver plays a dominant role in the light-heat conversion. Its performance can directly affect the efficiency of the whole power generation system. A combined calculation method for evaluating the thermal performance of the solar cavity receiver is raised in this paper. This method couples the Monte-Carlo method, the correlations of the flow boiling heat transfer, and the calculation of air flow field. And this method can ultimately figure out the surface heat flux inside the cavity, the wall temperature of the boiling tubes, and the heat loss of the solar receiver with an iterative solution. With this method, the thermal performance of a solar cavity receiver, a saturated steam receiver, is simulated under different wind environments. The highest wall temperature of the boi...

Energy Technology Data Exchange (ETDEWEB)

We present results from a kinetic Monte Carlo simulation of boron transient enhanced diffusion (TED) in silicon. Our approach avoids the use of phenomenological fits to experimental data by using a complete and self-consistent set of values for defect and dopant energetics derived mostly from {ital ab initio} calculations. The results predict that, during annealing of 40 keV B-implanted Si at 800{degree}C, there exists a time window during which all the implanted boron atoms are substitutional. At earlier or later times, the interactions between free silicon self-interstitials and boron atoms drive the growth of boron clusters and result in an inactive boron fraction. The results show that the majority of boron TED takes place during the growth period of interstitial clusters and not during their dissolution. {copyright} {ital 1998 American Institute of Physics.}

CERN Document Server

We study the finite temperature electroweak transition with non-perturbative lattice Monte Carlo simulations. We find that it is of first order, at least for Higgs masses up to 80 GeV. The critical temperature of the phase transition is found to be smaller than that determined by a 2-loop renormalization group improved effective potential. The jump of the order parameter at the critical temperature is considerably larger than the perturbative value. By comparing lattice data and perturbation theory, we demonstrate that the latter, for the computation of the vacuum expectation value of the Higgs field v(T) in the broken phase at given temperature, converges quite well, provided v(T)/T>1. An upper bound on the Higgs mass necessary for electroweak baryogenesis in the light of the lattice data is briefly discussed.

CERN Document Server

A new property which relies on the linear programming (LP) decoder, the approximate maximum-likelihood certificate (AMLC), is introduced. When using the belief propagation decoder, this property is a measure of how close the decoded codeword is to the LP solution. Using upper bounding techniques, it is demonstrated that the conditional frame error probability given that the AMLC holds is, with some degree of confidence, below a threshold. In channels with low noise, this threshold is several orders of magnitude lower than the simulated frame error rate, and our bound holds with very high degree of confidence. In contrast, showing this error performance by simulation would require very long Monte Carlo runs. When the AMLC holds, our approach thus provides the decoder with extra error detection capability, which is especially important in applications requiring high data integrity.

Energy Technology Data Exchange (ETDEWEB)

We point out that the occurrence of a large-distance ''Coulomb'' term in the static quark-antiquark potential is related to tachyons in the underlying string model. Thus, the tachyon contents determine the coefficient of the ''Coulomb'' term. For a scalar string, one has Luescher's result -(d-2) /24R, for a Neveu-Schwarz string one obtains -(d-2) /16R, whereas for the Ramond string (and strings without tachyons) the ''Coulomb'' term vanishes. Monte Carlo data for QCD prefers a ''Coulomb'' term. This is not inconsistent with the tachyonic origin of this term, since the large-distance behaviour of string models is consistent even with tachyons. Also, critical dimensions are not necessary at large distances.

Energy Technology Data Exchange (ETDEWEB)

We have studied, by a Monte Carlo simulation code ACAT-DIFFUSE, the fluence-dependence of the amount of retained helium atoms in tungsten carbide at room temperature under helium ion bombardment. The retention behavior may be understood qualitatively in terms of irradiation-dependent diffusion coefficient assumed and range. The emission processes from tungsten carbide under helium ion irradiation derived were compared with each other. We have discussed the retention curves for incident energy of 5 keV at incident angles of 0deg and 80deg and of 500 eV at 0deg. The energy spectra of helium atoms reflected from tungsten carbide for incident energy of 500 eV at 0deg and 80deg were compared with those from graphite and tungsten. (author)

Energy Technology Data Exchange (ETDEWEB)

In this report we present an update on the results from the Amanda-B10 detector which operated in 1997 at depths of 1500 to 2000 meters in the deep Antarctic ice. The goal of Amanda project is to search for extra-terrestrial neutrinos. As a precursor to such a search we have studied atmospheric neutrinos which act as a calibration source for the detector. The observation of atmospheric neutrinos at a rate consistent with Monte-Carlo predictions establishes Amanda-B10 as a neutrino telescope. The Amanda-B10 data has been searched for evidence of several classes of neutrinos and for magnetic monopoles. Searches for a diffuse high energy neutrino flux and for neutrinos in coincidence with gamma-ray bursts have been conducted. Preliminary data analyses show no excess of neutrinos has been found. (A.C.)

International Nuclear Information System (INIS)

New values of the factors required to convert the reading of a radiation dosemeter calibrated in terms of air kerma (or exposure) into absorbed dose to water for medium-energy x-radiation were given in a code of practice published by the International Atomic Energy Agency in 1987. These are not considered to possess sufficient support from other sources. It is therefore recommended that the F-factors given or codes of practice should continue to be used. Values of backscatter factors for low-energy x-radiation (below 140 kV) in Supplement 17 of the British Journal of Radiology appear to be inaccurate. New values based on Monte Carlo calculations, and supported by new experimental data, are given for use in radiotherapy. (author).

British Library Electronic Table of Contents (United Kingdom)

An energy transfer and conversion model for high-temperature solar cavity receivers has been developed using the transport behaviour of solar radiation as described by the spectral radiative exchange factors. A Monte-Carlo ray-tracing method coupled with optical properties was adopted, to predict radiation characteristics of the solar collector system by calculating radiative exchange factors. A cavity receiver with a plano-convexo quartz window was proposed, based upon the directional characteristics of the focal flux and the redistribution effect of the quartz window. Parametric studies on the windowed receiver provided a more uniform flux distribution, higher efficiency and lower loss than the windowless receivers. The predicted results serve as a design reference for the solar receiver...

Energy Technology Data Exchange (ETDEWEB)

The general objective of this workshop is to investigate and discuss methods by which uncertainties in mass balance models for toxics in the Great Lakes may be reduced. As described by the workshop prospectus, this paper is focused on problems of reducing (and quantifying) uncertainty as they relate to in situ field observations/system response measurements for the establishment of initial conditions, boundary conditions, calibration/confirmation data sets, and model post-audit data sets.'' I have taken this description to refer not only to the evaluation of uncertainty in the field observations themselves, but also to the uncertainty associated the analyses of in situ observations as they interact in the overall modeling process. Thus, I will be concerned here with quantification and reduction of uncertainty both (1) as they may be applied to descriptions of the system that is being modeled and (2) as they may be associated with model simulations.

CERN Document Server

Monte Carlo calculations of proton irradiation of permanent magnets for the TRADE experiment have been performed. An irradiation dose of about 4´106 Gy/yr/mA has been estimated due to beam losses in normal operating conditions. Existing experimental results indicate that this irradiation level may induce a considerable demagnetization: in fact, a dose of 6´107 Gy induces a remanence loss of 0.3 % on samples of Sm2Co17 magnets, which are the most resistant type. More detailed calculations with the final design of the magnets and of the beam line are suggested, to determine if the irradiation levels allowed a reliable operation of the permanent magnets for the entire duration of the TRADE experiment. Damage and gas production rates have also been calculated; the values obtained are very low, thus confirming that the demagnetization process is in great part reversible.

Energy Technology Data Exchange (ETDEWEB)

Analyses of pressure vessel damage resulting from neutron irradiation have primarily relied on two-dimensional transport calculations and a spatial-synthesis methodology to accommodate three-dimensional effects in the results of two two-dimensional calculations. In this paper, the authors report on calculations made on the Pool Critical Assembly (PCA) Benchmark, Configuration 12/13, using the three-dimensional, continuous energy Monte Carlo transport code, MCNP, and the three-dimensional, multigroup, diffusion accelerated discrete ordinates transport code THREEDANT. Neutron fluxes and activation rates as determined from these two calculations are compared to each other and to experimental results in the literature. The authors also draw some conclusions on the value of 3D calculations on the interpretation of experimental results.

International Nuclear Information System (INIS)

The basic relationships of the convolution/superposition dose calculation technique are reviewed, and a modelling technique that can be used for obtaining a satisfactory beam model for a commercially available convolution/superposition-based treatment planning system is described. A fluence energy spectrum for a Co-60 treatment machine obtained from a Monte Carlo simulation was used for modelling the fluence spectrum for a Rokus M machine. In order to achieve this model we measured the depth dose distribution and the dose profiles with a Wellhofer dosimetry system. The primary fluence was iteratively modelled by comparing the computed depth dose curves and beam profiles with the depth dose curves and crossbeam profiles measured in a water phantom. The objective of beam modelling is to build a model of the primary fluence that the patient is exposed to, which can then be used for the calculation of the dose deposited in the patient. (authors)

CERN Document Server

The possibility of radio galaxies being random sample of otherwise normal elliptical galaxies is tested. Starting with the observed optical luminosity functions for elliptical galaxies, it is shown that the probability of an elliptical forming a radio source is a continuous, increasing function of optical luminosity, precisely proportional to square of the optical luminosity of the galaxy. Once the probability function is fixed, the luminosity function of normal elliptical galaxies is used as input for Monte Carlo simulations that reproduce the distribution of radio galaxies in the radio-optical luminosity plane. Our results show that radio galaxies are luminosity biased, but otherwise random sample of elliptical galaxies. This unified view of radio and non-radio ellipticals also explains the well known difference of 0.5 mag in average optical luminosity between FRI and FRII radio galaxies as a simple selection effect. Specifically, FRII appear ...

International Nuclear Information System (INIS)

The present work summarizes efforts on the simulation of natural convection cooling within the IFMIF target and test cell. The simulations have been performed with the STAR-CD code using the k-#omega# high-Reynolds number turbulence model. A dedicated thermohydraulic model has been devised including Lithium loop components. Nuclear heat production has been calculated by the Monte-Carlo code McDeLicious for different parts of the target and test cell walls and was used as input for the STAR-CD simulations. Helium atmospheres at several pressures from 0.1 to 10"-"5 MPa have been investigated. In order to limit the maximum temperature of the concrete walls to 80 deg. C it was necessary to add thermal insulation layers to the hot Lithium loop surfaces and a conceptual system of two cooling layers in different depths of the concrete walls.

British Library Electronic Table of Contents (United Kingdom)

A model for risk and reliability analysis of complex multifunctional production process systems is presented. The model employs Monte-Carlo and Markov Chain algorithms that uses a weighted index to train and simulate the fuzzy hazard data sets which represents failure outcomes of risk component transient and non-transient systems. Early simulation results shows that hazard rates and the risk of containment loss from typical floating production and storage offloading (FPSO)-Riser system for the risk components in parallel or series increases exponentially with time and decreases as safety ratings fraction increases. The reliability value decreases with time and safety fraction (SFAC) for all fuzzy hazard classifications. The results of the computed mean time before repair (MTBR) show that t...

International Nuclear Information System (INIS)

A successful boron neutron capture treatment (BNCT) of a patient with multiple liver metastases has been first given in Italy, by placing the removed organ into the thermal neutron column of the Triga research reactor of the University of Pavia. In Finland, FiR 1 Triga reactor with an epithermal neutron beam well suited for BNCT has been extensively used to irradiate patients with brain tumors such as glioblastoma and recently also head and neck tumors. In this work we have studied by MCNP Monte Carlo simulations, whether it would be beneficial to treat an isolated liver with epithermal neutrons instead of thermal ones. The results show, that the epithermal field penetrates deeper into the liver and creates a build-up distribution of the boron dose. Our results strongly encourage further studying of irradiation arrangement of an isolated liver with epithermal neutron fields.

Energy Technology Data Exchange (ETDEWEB)

We consider low-energy nucleons at next-to-next-to-leading order in lattice chiral effective field theory. Three-body interactions first appear at this order, and we discuss several methods for determining three-body interaction coefficients on the lattice. We compute the energy of the triton and low-energy neutron-deuteron scattering phase shifts in the spin-doublet and spin-quartet channels using Luescher's finite-volume method. In the four-nucleon system we calculate the energy of the {alpha}-particle using auxiliary fields and projection Monte Carlo. (orig.)

International Nuclear Information System (INIS)

The Monte-Carlo transport code MCNP was used to evaluate possible arrangements of cores for the MIT Reactor using monolithic LEU fuel. Plate and moderator thicknesses were varied, and fixed absorbers and inner reflectors added in an effort to maximize available neutron fluxes at in-core and ex-core locations of experimental facilities. Addition of D_2O in the H_2O moderator was also evaluated. Comparisons of the fast, epithermal, and thermal fluxes were made at selected locations. Keff was also evaluated and critical blade heights compared with the existing HEU core. Results indicate that the LEU fluxes could approach HEU values with the use of a fueled in-core experimental facility, a fixed boron absorber spider and an inner beryllium reflector. (author)

British Library Electronic Table of Contents (United Kingdom)

Purpose - Burr distribution has been proved to be a useful failure model. It can assume different shapes which allow it to be a good fit for various lifetimes data. Hybrid censoring is an important way of generating lifetimes data. The purpose of this paper is to estimate an unknown parameter of the Burr type XII distribution when data are hybrid censored. Design/methodology/approach - The problem is dealt with through both the classical and Bayesian point of view. Specifically, the methods of estimation used to tackle the problem are maximum likelihood estimation method and Bayesian method. Empirical Bayesian approach is also considered. The performance of all estimates is compared through their mean square error values. The paper employs Monte Carlo simulation to evaluate the mean square...

British Library Electronic Table of Contents (United Kingdom)

In this paper, the effects of surface mediation on the adsorption isotherm and isosteric heat of adsorption on a graphite surface were investigated, as the surface mediation is known to affect the intermolecular interaction of adsorbed molecules close to the surface. Kim and Steele (Phys. Rev. B 45 (11) (1992) 6226-6233) and others have assumed that the surface mediation is confined only to the first layer. This will be tested in this paper with a combined experimental and Grand Canonical Monte Carlo (GCMC) simulation of adsorption of argon on graphitized thermal carbon black (GTCB) over a range of temperatures (77-95.25K). By matching the simulation results against the experimental data, we have found that the surface mediation is extended up to the fourth layer, rather than only the firs...

International Nuclear Information System (INIS)

Dissociative electron capture to CCl_4 is studied by measuring the angular and velocity distribution of Cl"- ions produced in collisions with velocity selected K(np) Rydberg atoms. Analysis of the data using a Monte Carlo collision code that models the detailed kinematics of the reaction indicates that the lifetime of the CCl_4"- intermediate formed by Rydberg electron capture is 7.5 #+-# 2.5 ps and that, upon dissociation, only a small fraction of the excess energy of reaction appears as translational energy of the Cl"- and CCl_3 fragments. The present approach is one of the few experimental techniques yet devised that can probe the lifetimes of collisionally-produced excited states on a picosecond timescale, and demonstrates that Rydberg atoms provide a unique tool with which to investigate the dynamics of dissociative electron attachment. Measurements are being extended to additional species, including CFCl_3.

Energy Technology Data Exchange (ETDEWEB)

An essential part of fire risk assessment is the analysis of fire hazards and fire propagation. In this work, models and tools for two different aspects of numerical fire simulation have been developed. The primary objectives have been firstly to investigate the possibility of exploiting state-of-the-art fire models within probabilistic fire risk assessments and secondly to develop a computationally efficient solver of thermal radiation for the Fire Dynamics Simulator (FDS) code. In the first part of the work, an engineering tool for probabilistic fire risk assessment has been developed. The tool can be used to perform Monte Carlo simulations of fires and is called the Probabilistic Fire Simulator (PFS). In Monte Carlo simulation, the simulations are repeated multiple times, covering the whole range of variability of the input parameters and thus resulting in a distribution of results covering what can ...

Energy Technology Data Exchange (ETDEWEB)

The spectrum of antiprotons from dark matter annihilation are calculated using the Lund Monte Carlo program, and simple analytic expressions for the spectrum and low-energy antiproton/proton ratio are derived. Comparing the results with recent upper limits on low energy antiprotons, it is concluded that the reported 4-13 GeV antiproton flux cannot be accounted for by dark matter annihilation. The new upper limits do not provide useful constraints on dark matter particles. They restrict the annihilation rate and imply that annihilation gamma ray and e(+) fluxes would be far below the fluxes produced by cosmic-ray collisions. It may be possible to look for a dark matter halo annihilation signal at antiprotons energies below 0.5 GeV, where the flux from cosmic-ray collisions is expected to be negligible. 32 references.

British Library Electronic Table of Contents (United Kingdom)

Air toxics from the industrial wastewater treatment plants (IWTPs) impose serious health concerns on its surrounding residential neighborhoods. To address such health concerns, one of the key challenges is to quantify the air emissions from the IWTPs. The objective here is to characterize the air emissions from the IWTPs and quantify its associated uncertainty. An IWTP receiving the wastewaters from an airplane maintenance facility is used for illustration with focus on the quantification of air emissions for benzyl alcohol, phenol, methylene chloride, 2-butanone, and acetone. Two general fate models, i.e., WATER9 and TOXCHEM+V3.0 were used to model the IWTP and quantify the air emissions. Monte Carlo and Bootstrap simulation were used for uncertainty analysis. On average, air emissions fr...

International Nuclear Information System (INIS)

We present results of multiple-time-scale simulations of 5, 10 and 15 keV low temperature ion implantation of arsenic on silicon (100), followed by high temperature anneals. The simulations start with a molecular dynamics (MD) calculation of the primary state of damage after 10ps. The results are then coupled to a kinetic Monte Carlo (MC) simulation of bulk defect diffusion and clustering. Dose accumulation is achieved considering that at low temperatures the damage produced in the lattice is stable. After the desired dose is accumulated, the system is annealed at 800 degrees C for several seconds. The results provide information on the evolution for the damage microstructure over macroscopic length and time scales and affords direct comparison to experimental results. We discuss the database of inputs to the MC model and how it affects the diffusion process.

British Library Electronic Table of Contents (United Kingdom)

Most active pharmaceutical ingredients (API) exhibit particle size distributions with some degrees of asymmetry deviating from log-normality. A new log-skew-normal (L-S-N) distribution model is proposed for a systematic comparison of the asymmetry effect on content uniformity. The new model originated from the S-N model used by Azzalini gives a close approximation to real API particle size distribution. Monte-Carlo method was employed to simulate the dosage potency distribution. A high risk of over potency is uncovered when either the dose is low or API particle size distribution is positively skewed. This is due to the formation of pseudo heavy tail in potency distribution that decays slower than exponentially. Nomographs of API particle size versus dosage strength were constructed with a...

CERN Document Server

We compare the metallicities of stars with radial velocity planets to the metallicity of a sample of field dwarfs. We confirm recent work indicating that the stars-with-planet sample as a whole is iron rich. However, the lowest mass stars tend to be iron poor, with several having [Fe/H]0.48) that contributes to but does not explain the mass-metallicity trend in the stars-with-planets sample. We use Monte Carlo models to show that adding an average of 6.5 Earth masses of iron to each star can explain both the mass-metallicity and the age-metallicity relations of the stars-with-planets sample. However, for at least one star, HD 38529, there is good evidence that the bulk metallicity is high. We conclude that the observed metallicities and metallicity trends are the result of the interaction of three effects; accretion of about 6 Earth masses of iron rich material, selection effects, and in some cases, high intrinsic metallicity.

British Library Electronic Table of Contents (United Kingdom)

We carried out theoretical analyses based on ab initio calculations that incorporate free energy of the vapor phase in order to determine the initial growth process of cubic GaN on GaN (001)-(4x1). The results suggest that a N-adsorbed structure appears at the initial growth stage and then Ga adsorbs on the N-adsorbed GaN (001)-(4x1) surface. Considering this process, we performed Monte Carlo simulations. The results suggest that the maximum point of Ga coverage after supplying a Formula Not Shown monolayer of atoms shifted toward a Ga-rich condition from V/III=1.0.

International Nuclear Information System (INIS)

This paper presents a trial of probabilistic simulation for performance assessment of high-level waste (HLW) disposal using the Monte Carlo method. Based on the Reference Case conceptual model in H12, a new integrated simulation system which allowed us to rapidly evaluate the effect of data uncertainty was developed. The doses to hypothetical exposure group were compared with the results of H12 that were performed by using a point-wise approach, in terms of maximum total dose. This study showed that H12 results were consistent with results of probabilistic simulation and also showed that transmissivity had a strong influence for the uncertainty of the system performance in all simulation time. (author)

Energy Technology Data Exchange (ETDEWEB)

A complete code based on the finite element method (FEM) is used to study the attenuation of gamma rays, of source energy 9 MeV, in simple homogeneous lead and water systems. The results are compared, in tables and graphs, with those produced by a Monte Carlo method of solution. In the comparison, particular attention is paid to the annihilation gamma rays generated by the pair production process, to energy deposition, and to the leakage spectra. A model, multilayer, slab shield, having a fission neutron source impinging on the left-hand face, is also solved by the FEM code, using data from a coupled neutron/gamma ray cross section library. The resulting neutron and gamma ray flux distributions, and the leakage spectra, are shown graphically. (author).

Energy Technology Data Exchange (ETDEWEB)

No abstract prepared.

Energy Technology Data Exchange (ETDEWEB)

Within the framework of the EFTTRA cooperation between CEA, ECN, EDF, FZK, IAM and ITU, six metallic {sup 99}Tc rods have been irradiated in the Petten HFR for 193 effective full power days. During this irradiation, more than 6% of the {sup 99}Tc has been transmuted to the stable {sup 100}Ru. At ECN, one of the six rods has been examined in the hot cell laboratory. The ruthenium concentration in the rod measured by Isotope Dilution Mass Spectrometry reaches 6.4% at 5 mm from the bottom of the rod and 6.0% at 5 mm from the top. Also the axial and radial distributions of the ruthenium have been measured by Electron Probe Micro Analysis. The ruthenium concentrations calculated by the three-dimensional Monte Carlo code KENO reach 6.1% at 5 mm from the bottom of the rod and 5.7% at 5 mm from the top. These values are in reasonable agreement with the measured ones. However, the calculated radial distribution of the ruthenium concentration is not in ...

Energy Technology Data Exchange (ETDEWEB)

The verification of the subcriticality is of utmost importance for the safe transportation and storage of nuclear reactor fuels. Transportation containers and storage facilities are designed such that nuclear fuels remain in a subcritical state. Such designs often involve excess conservatism because of the lack of relevant experimental data to verify the accuracy of Monte Carlo codes used in nuclear criticality safety analyses. A joint experimental research program between Oak Ridge National Laboratory, Westinghouse Safety Management Solutions, Inc., and the University of Missouri was initiated to obtain measured quantities that could be directly related to the subcriticality of simple arrays of Missouri University Research Reactor (MURR) fuel elements. A series of measurement were performed to assess the reactivity of materials such as BORAL, stainless steel, aluminum, and lead that are typically used in the construction of shipping casks. ...

International Nuclear Information System (INIS)

For the study of radiation biology and its application to radiotherapy, the double differential cross section of electron emission from water vapor induced by 6.0 MeV alpha particle beam is measured. The energy spectra of electrons ranging 7- 10000 eV are detected by the electrostatic analyzer and micro channel plate. The measurements are made at angles between 20 and 160 degrees. With use of this data set, the radial dose distribution in water is calculated by using KURBUC code. It is the Monte Carlo type code of the electron transport process, where the track of the electron is simulated through each individual interactions including elastic scattering, ionization cross section and total excitation cross section in case that electrons with certain energy are put in the liquid-density water. In order to understand the effect of radiation when the particle flux is injected in the human body like radiotherapy using accelerator beam, the dose ...

International Nuclear Information System (INIS)

We study the dynamical evolution of globular clusters containing primordial binaries, including full single and binary stellar evolution using our Monte Carlo cluster evolution code updated with an adaptation of the single and binary stellar evolution codes SSE and BSE from Hurley et al. We describe the modifications that we have made to the code. We present several test calculations and comparisons with existing studies to illustrate the validity of the code. We show that our code finds very good agreement with direct N-body simulations including primordial binaries and stellar evolution. We find significant differences in the evolution of the global properties of the simulated clusters using stellar evolution compared with simulations without any stellar evolution. In particular, we find that the mass loss from the stellar evolution acts as a significant energy production channel simply by reducing the total gravitational binding energy and ...

Energy Technology Data Exchange (ETDEWEB)

We have developed a kinetic Monte Carlo (kMC) simulator that links atomic migration and binding energies determined primarily from first principles calculations to macroscopic phenomena and laboratory time scales. Input for the kMC simulation is obtained from a combination of ab initio planewave pseudopotential calculations, molecular dynamics simulations, and experimental data. The simulator is validated against an extensive series of experimental studies of the diffusion of B spikes in self-implanted Si. The implant energy, dose, and dose rate, as well as the detailed thermal history of the sample, are included. Good agreement is obtained with the experimental data for temperatures between 750 and 950 C and times from 15 to 255 s. At 1050o C we predict too little diffusion after 105 s compared to experiment: apparently, some mechanism which is not adequately represented by our model becomes important at this temperature. Below 1050o C, the ...

Science.gov (United States)

Adsorption of ethylene and ethane on graphitized thermal carbon black and in slit pores whose walls are composed of graphene layers is studied in detail to investigate the packing efficiency, the two-dimensional critical temperature, and the variation of the isosteric heat of adsorption with loading and temperature. Here we used a Monte Carlo simulation method with a grand canonical Monte Carlo ensemble. A number of two-center Lennard-Jones (LJ) potential models are investigated to study the impact of the choice of potential models in the description of adsorption behavior. We chose two 2C-LJ potential models in our investigation of the (i) UA-TraPPE-LJ model of Martin and Siepmann for ethane and Wick et al. for ethylene and (ii) AUA4-LJ model of Ungerer et al. for ethane and Bourasseau et al. for ethylene. These models are used to study the adsorption of ethane and ethylene on graphitized thermal ...

International Nuclear Information System (INIS)

In clinical applications, it is very important to accurately determine the range of a proton beam in a patient. Recently, a prototype prompt-gamma scanning system, called a prompt-gamma scanner (PGS), has been constructed at Hanyang University in Korea with the collaboration of the Korean national cancer center (NCC), based on a series of Monte Carlo simulations. The PGS system is composed of a prompt-gamma collimator, a CsI(Tl) scintillation detector, a multi-channel analyzer (MCA), a precision movement system, and an integrated readout system. The prompt-gamma collimator is designed to effectively shield high-energy neutrons from the proton beam passage and subsequent capture gammas. The PGS system can be used to scan the distribution of the prompt gammas in the patient from the proton beam passage. The distribution of the prompt gammas can then be used to determine the proton beam range or the distal dose edge in the patient. In this study, ...

Energy Technology Data Exchange (ETDEWEB)

In large samples, the {gamma}-ray count rate of a prompt gamma neutron activation analysis system is a multi-variable function of the elemental dry composition, density, water content and thickness of the material. The experimental calibration curves require tremendous laboratory work, using a great number of standards with well-known compositions. Although a Monte Carlo simulation study does not avoid the experimental calibration work, it reduces the number of experimental calibration standards. This paper is part of a feasibility study for a PGNAA system for on-line continuous characterisation of cement raw material conveyed on a belt (Oliveira, C., Salgado, J. and Carvalho, F. G. (1997) Optimisation of PGNAA instrument design for cement raw materials using the MCNP code. J. Radioanal. Nucl. Chem. 216(2), 191-198; Oliveira, C., Salgado, J., Goncalves, I. F., Carvalho, F. G. and Leitao, F. (1997a) A Monte ...

Energy Technology Data Exchange (ETDEWEB)

The analysis of oceanographic lidar systems measurements is often carried out with semi-empirical methods, since there is only a rough understanding of the effects of many environmental variables. The development of techniques for interpreting the accuracy of lidar measurements is needed to evaluate the effects of various environmental situations, as well as of different experimental geometric configurations and boundary conditions. A Monte Carlo simulation model represents a tool that is particularly well suited for answering these important questions. The PREMAR-2F Monte Carlo code has been developed taking into account the main molecular and non-molecular components of the marine environment. The laser radiation interaction processes of diffusion, re-emission, refraction and absorption are treated. In particular are considered: the Rayleigh elastic scattering, produced by atoms and molecules with ...

Energy Technology Data Exchange (ETDEWEB)

Experiments with fresh PWR fuel assemblies were performed to assess the {sup 252}Cf-source-driven frequency analysis method for measuring the subcriticality of spent fuel. The measurements at the Babcox and Wilcox Critical Experiments Facility mocked up between 17x17 fuel pins (single assembly) and a full array of 4961 fuel pins (about 17 fuel assemblies) in borated water with a fixed B concentration. For the full array, the B content of the water was varied from 1511 at delayed criticality to 4303 ppM. Measurements were done for various source-detector-fuel pin configurations; they showed high sensitivity of frequency analysis parameters to B content and fissile mass. Parameters such as auto and cross power spectral densities can be calculated directly by a more general model of the Monte Carlo code (MCNP-DSP). Calculation-measurement comparisons are presented. This model permits the validation of neutron and gamma ray transport calculational ...

Energy Technology Data Exchange (ETDEWEB)

This paper is concerned with the validation of the 3D deterministic neutral-particle transport theory code EVENT for shielding applications. The code is based on the finite element-spherical harmonics (FE-P{sub N}) method which has been extensively developed over the last decade. A general multi-group, anisotropic scattering formalism enables the code to address realistic steady state and time dependent, multi-dimensional coupled neutron/gamma radiation transport problems involving high scattering and deep penetration alike. The powerful geometrical flexibility and competitive computational effort makes the code an attractive tool for shielding applications. In recognition of this, EVENT is currently in the process of being adopted by the UK nuclear industry. The theory behind EVENT is described and its numerical implementation is outlined. Numerical results obtained by the code are compared with predictions of the Monte Carlo code MCBEND and ...

Energy Technology Data Exchange (ETDEWEB)

The aim of this work is the evaluation of the quality of a chemistry-transport model, not by a classical comparison with observations, but by the estimation of its uncertainties due to the input data, to the model formulation and to the numerical approximations. The study of these 3 sources of uncertainty is carried out with Monte Carlo simulations, with multi-model simulations and with comparisons between numerical schemes, respectively. A high uncertainty is shown for ozone concentrations. To overcome the uncertainty-related limitations, a strategy consists in using the overall forecasting. By combining several models (up to 48) on the basis of past observations, forecasts can be significantly improved. This work has been also the occasion of developing an innovative modeling system, named Polyphemus. (J.S.)

International Nuclear Information System (INIS)

In the convolution/superposition method of photon beam dose calculations, inhomogeneities are usually handled by using some form of scaling involving the relative electron densities of the inhomogeneities. In this paper the accuracy of density scaling as applied to primary electrons generated in photon interactions is examined. Monte Carlo calculations are compared with density scaling calculations for air and cork slab inhomogeneities. For individual primary photon kernels as well as for photon interactions restricted to a thin layer, the results can differ significantly, by up to 50%, between the two calculations. However, for realistic photon beams where interactions occur throughout the whole irradiated volume, the discrepancies are much less severe. The discrepancies for the kernel calculation are attributed to the scattering characteristics of the electrons and the consequent oversimplified modeling used in the density scaling method. A ...

International Nuclear Information System (INIS)

The energy spectra of energetic confined alpha particles are being measured using the pellet charge exchange method [R. K. Fisher, J. S. Leffler, A. M. Howald, and P. B. Parks, Fusion Technol. 13, 536 (1988)]. The technique uses the dense ablation cloud surrounding an injected impurity pellet to neutralize a fraction of the incident alpha particles, allowing them to escape from the plasma where their energy spectrum can be measured using a neutral particle analyzer. The signal calculations given in the above-mentioned reference disregarded the effects of the alpha particles' helical Larmor orbits, which causes the alphas to make multiple passes through the cloud. Other effects such as electron ionization by plasma and ablation cloud electrons and the effect of the charge state composition of the cloud, were also neglected. This report considers these issues, reformulates the signal level calculation, and uses a Monte-Carlo approach to calculate the neutralization ...

CERN Document Server

Spatially resolved studies of star forming regions show that the assumption of spherical geometry is not realistic in most cases, with a major complication posed by the gas being ionised by multiple non-centrally located stars or star clusters. We try to isolate the effects of multiple non-centrally located stars on the temperature and ionisation structure of HII regions, via the construction of 3D photoionisation models using the 3D Monte Carlo photoionisation code MOCASSIN. We find that the true temperature fluctuations due to the stellar distribution (as opposed to the large-scale temperature gradients due to other gas properties) are small in all cases and not a significant cause of error in metallicity studies. Strong emission lines from HII regions are often used to study the metallicity of star-forming regions. We compare integrated emission line spectra from our models and quantify any systematic errors caused by the simplifying ...

CERN Document Server

We have performed multicanonical Monte Carlo simulations of C-peptide of ribonuclease A. It is known by CD and NMR experiments that this peptide has high alpha-helix content in aqueous solution and that the side-chain charges of residues Glu-2$^-$ and His-12$^+$ play an important role in the stability of the alpha-helix. In order to confirm these experimental implications, we have used two analogues of the peptide with charged and neutral side chains of Glu-2 and His-12. Two dielectric functions, distance-dependent and constant, are considered to study the effects of solvent contributions. All the simulations were started from random initial conformations. Various thermodynamic quantities such as average helicity as a function of residue number and average distance between two side chains as a function of temperature are calculated. The results are found to be in accord with the implications of CD and NMR experiments. The lowest-energy ...

Energy Technology Data Exchange (ETDEWEB)

We describe a stochastic inversion method for mapping subsurface regions where the electrical resistivity is changing. The technique combines prior information, electrical resistance data and forward models to produce subsurface resistivity models that are most consistent with all available data. Bayesian inference and a Metropolis simulation algorithm form the basis for this approach. Attractive features include its ability to: (1) provide quantitative measures of the uncertainty of a generated estimate and, (2) allow alternative model estimates to be identified, compared and ranked. Methods that monitor convergence and summarize important trends of the posterior distribution are introduced. Results from a physical model test and a field experiment were used to assess performance. The stochastic inversions presented provide useful estimates of the most probable location, shape, and volume of the changing region, and the most likely resistivity change. The proposed method is ...

Energy Technology Data Exchange (ETDEWEB)

An overview is provided of an evolving atomistic and kinetic model of semiconductor growth that unifies the main features of strain relaxation in low and high lattice misfit heteroepitaxy. The model reveals a kinetic pathway for dislocation formation during growth with little or no energy cost at low misfits, thus providing a way out of the longstanding dilemma of too high dislocation nucleation energies predicted by classical theories of the equilibrium behavior of a fixed number of particles at low misfits. The essential kinetic process underlying the model are identified on the basis of comparison of the predictions of kinetic Monte-Carlo simulations of growth with real-time or in-situ data obtained in such experiments as reflection high-energy electron diffraction (RHEED) and scanning probe microscopy (SPM). Relative significance of these atomistic kinetic processes is shown to naturally lead to strain relaxation via defect initiation at low misfits while ...

International Nuclear Information System (INIS)

This paper consists of shielding analysis of steel balls and water filled end shields of Indian Pressurized Heavy Water Reactors (PHWRs). The material composition inside lattice tube is entirely different neutronically as compared with the composition of end-shield. Due to variation of material composition in radial and axial directions and complex geometry, it is necessary to carry out 3-D analysis for reasonable prediction of neutron flux and gamma dose rates. In the present paper, shielding analysis of end-shield for 540 MWe PHWR has been carried out during reactor operating and shutdown conditions using Monte-Carlo code MCNP. Furthermore materials on the periphery and central portion of end shield are different. Therefore the analysis was carried out separately for annular portion and central portion of end shield. The dominating streaming paths through end shields were studied. Predictions compare well with the measurements at TAPS-4 reactor. (author)

Energy Technology Data Exchange (ETDEWEB)

A probability-based approach is presented as the integration of probabilistic methods and deterministic modelling based on the finite element method. An existing finite element software package was linked to an existing probabilistic package to analyse the complex mechanics that occur during the transient non-linear analysis of impact problems. This methodology is applied to a pipe whip analysis of a group-distribution-header, which results from a guillotine break, and subsequent impact with the adjacent building wall; this is a postulated accident for the Ignalina Nuclear Power Plant RBMK-1500 reactors. The uncertainties of material properties, component geometry data and loads were taken into consideration. The probabilities of failure of the impacted header and of the header support-wall were estimated given uncertainties in material properties, geometrical parameters and loading. The software ProFES was used for the probabilistic analysis and the finite element software NEPTUNE for ...

International Nuclear Information System (INIS)

The reduction of transient enhanced diffusion (TED) with reduced implantation energy has been investigated and quantified. A fixed dose of 1x10"1"4 cm"-"2 Si"+ was implanted at energies ranging from 0.5 to 20 keV into boron doping superlattices and enhanced diffusion of the buried boron marker layers was measured for anneals at 810, 950, and 1050 degree C. A linearly decreasing dependence of diffusivity enhancement on decreasing Si"+ ion range is observed at all temperatures, extrapolating to #approx#1 for 0 keV. This is consistent with our expectation that at zero implantation energy there would be no excess interstitials from the implantation and hence no TED. Monte Carlo modeling and continuum simulations are used to fit the experimental data. The results are consistent with a surface recombination length for interstitials of <10 nm. The data presented here demonstrate that in the range of annealing temperatures of interest for p-n ...

Energy Technology Data Exchange (ETDEWEB)

Purpose: calculation of conversion coefficients for the reconstruction of organ doses from entrance doses for abdomen radiographs of 0, 1, 5, 10, 15, and 30-year-old patients in conventional pediatric radiology for the radiographic settings recommended by the German and European guidelines for quality management in diagnostic radiology. Materials und method: using the commercially available personal computer program PCXMC developed by the Finnish Center for Radiation and Nuclear Safety (Saeteilyturvakeskus STUK), conversion coefficients for conventional abdomen radiographs were calculated performing Monte Carlo simulations in mathematical hermaphrodite phantom models describing patients of different ages. The possible clinical variation of beam collimation was taken into consideration by defining optimal and suboptimal radiation fields on the phantoms' surfaces. Results: conversion coefficients for the reconstruction of organ does in ...

CERN Document Server

Being able to distinguish light-quark jets from gluon jets on an event-by-event basis could significantly enhance the reach for many new physics searches at the Large Hadron Collider. Through an exhaustive search of existing and novel jet substructure observables, we find that a multivariate approach can filter out over 95% of the gluon jets while keeping more than half of the light-quark jets. Moreover, a combination of two simple variables, the charge track multiplicity and the pT-weighted linear radial moment (girth), can achieve similar results. While this pair appears very promising, our study is only Monte Carlo based, and other discriminants may work better with real data in a realistic experimental environment. To that end, we explore many other observables constructed using different jet sizes and parameters, and highlight those that deserve further theoretical and experimental scrutiny. Additional information, including distributions ...

CERN Document Server

We present very sensitive polarimetry of 55 Cnc and tau Boo in an attempt to detect the partially polarised reflected light from the planets orbiting these two stars. 55 Cnc is orbited by a hot Neptune planet (55 Cnc e) at 0.038 AU, a hot Jupiter planet (55 Cnc b) at 0.11 AU, and at least 3 more distant planets. The fractional polarisation of this star is very stable, with a standard deviation in the nightly averaged Stokes Q/I and U/I parameters of 2.2x10^{-6}. We derive upper limits on the geometric albedo, A_G and planetary radius using Monte Carlo multiple scattering simulations of a simple model atmosphere. We assume Rayleigh-like scattering and polarisation behaviour (scaled by the maximum polarisation, p_m at 90 degrees) and pressure insensitive extinction. Atmospheres in which multiple scattering plays only a small role have an almost linear relation between polarisation and A_G. In this case, the 4 sigma upper limits are ...

Energy Technology Data Exchange (ETDEWEB)

Current advanced CMOS source/drain engineering involves the use of amorphizing implants with 3D geometry. Upon annealing, the induced transient enhanced diffusion (TED) can only be accurately predicted if the amorphized region is correctly modeled, as well as the formation and evolution of extended defects, particularly 3 1 1's and dislocation loops. In addition to the extended defects, already modeled in the atomistic kinetic Monte-Carlo simulator DADOS, we have developed a physically based modeling approach for the implant-induced damage build-up, amorphization and recrystallization, suitable to handle device-size process simulation. It is based on amorphous pockets (3D, irregular shape agglomerates of an arbitrary number of interstitials and vacancies, plus trapped impurities) with a size-dependent activation energy for recombination. The model is able to reproduce experimental aspects like the crystal-amorphous transition temperature and the super ...

CERN Document Server

The traditional way of estimating the gravitational field from observed motions of test objects is based on the virial relation between their kinetic and potential energy. We find a more efficient method. It is based on the natural presumption that the objects are observed at a random moment of time and therefore have random orbital time phases. The proposed estimator, which we call "orbital roulette", checks the randomness of the phases. The method has the following advantages: (1) It estimates accurately Keplerian (point-mass) potentials as well as non-Keplerian potentials where the unknown gravitating mass is distributed in space. (2) It is a complete statistical estimator: it checks a trial potential and accepts it or rules it out with a certain significance level; the best-fit measurement is thus supplemented with error bars at any confidence level. (3) It needs no a priori assumptions about the distribution of orbital parameters of the test bodies. We test our estimator with ...

CERN Document Server

We test the hypothesis that radio galaxies are a random subset of otherwise normal elliptical galaxies. Starting with the observed optical luminosity functions for elliptical galaxies, we show that the probability of an elliptical forming a radio source is a continuous, increasing function of optical luminosity, proportional to L squared. With this probability function and the luminosity function of normal elliptical galaxies as input to Monte Carlo simulations, we reproduce the observed distribution of radio galaxies in the radio-optical luminosity plane. Our results show that radio galaxies are a luminosity-biased but otherwise random sample of elliptical galaxies. This unified view of radio-loud and radio-quiet ellipticals also explains the well known difference of ~0.5 mag in average optical luminosity between FRI and FRII radio galaxies as a simple selection effect. Specifically, FRII appear preferentially in smaller galaxies because both ...

Energy Technology Data Exchange (ETDEWEB)

This thesis consists of five chapters, each of which is a self-contained unit. The first chapter overviews methods for electronic-structure calculations. Chapter 2 introduces a new method to generate a rapidly converging configuration expansion. The approach iteratively combines (1) a least-squares fitting of a configuration expansion to a many-body wave function with (2) a transfer-matrix method for projecting out the ground state. Results are shown to be equivalent to multiconfiguration Hartree-Fock. Results from test calculations are given for a simple finite difference model of the helium atom. In Chapter 3 the use of the finite-element method in electronic structure calculations is discussed. Chapters 4 and 5 discuss developments in Monte Carlo methods based on Hubbard-Stratonovich transformations. Chapter 4 introduces a canonical ensemble formulation of the method, which is more appropriate than the usual grand canonical formulation for ...

CERN Document Server

For purposes of designing targeted cataclysmic variable (CV) detection surveys and interpreting results of other projects with many CV detections such as the ChaMPlane Survey, we have created a model of the CV distribution in the Galaxy. It is modeled as a warped, flared exponential disk with a gaussian vertical distribution. Extinction is based on a detailed Galactic dust and gas model. A luminosity function for CVs is also incorporated, based on a smoothed version of published data. We calculate predicted field detection rates as a function of the limiting magnitude expected for the detecting system (i.e. WIYN/Hydra or NOAO 4m/Mosaic). Monte-Carlo techniques are used to assess statistical fluctuations in these rates. We have created maps of the expected CV distribution for the full non-bulge Galactic plane (20

CERN Document Server

In a recent study of a search for enhancements from the galactic center with muons at sea level using the TUPI muon telescope, we have found several ground level enhancements (GLEs) as very sharp peaks above the count rate background. This paper reports a consistent analysis of two GLEs observed in December 2003 and detected after an up-grade of the data acquisition system, which includes a noise filter and which allows us to verify that the GLEs are not mere background fluctuations. The main target of this study is a search for the origin of the GLEs. The results show that one of them has a strong correlation with a solar flare, while the other has an unknown origin, because there is neither a satellite report of a solar flare, nor prompt X-ray emission, and nor a excess of nuclei during the raster scan where the GLE was observed. Even so, two possibilities are analyzed: the solar flare hypothesis and the gamma ray burst (GRB) hypothesis. We show, by using the FLUKA ...

Energy Technology Data Exchange (ETDEWEB)

The O({alpha}) electroweak radiative corrections to {gamma}{gamma}{yields}WW{yields}4f within the electroweak standard model are calculated in double-pole approximation (DPA). Virtual corrections are treated in DPA, leading to a classification into factorizable and non-factorizable contributions, and real-photonic corrections are based on complete lowest-order matrix elements for {gamma}{gamma}{yields}4f+{gamma}. Soft and collinear singularities appearing in the virtual and real corrections are combined alternatively in two different ways, namely by using the dipole subtraction method or by applying phase-space slicing. The radiative corrections are implemented in a Monte Carlo generator called Coffer {gamma}{gamma} - the computer code can be obtained from the authors upon request - which optionally includes anomalous triple and quartic gauge-boson couplings in addition and performs a convolution over realistic spectra of the photon beams. A ...

CERN Document Server

We present a showcase for deriving bounds on the neutrino masses from laboratory experiments and cosmological observations. We compare the frequentist and Bayesian bounds on the effective electron neutrino mass m_beta which the KATRIN neutrino mass experiment is expected to obtain, using both an analytical likelihood function and Monte Carlo simulations of KATRIN. Assuming a uniform prior in m_beta, we find that a null result yields an upper bound of about 0.17 eV at 90% confidence in the Bayesian analysis, to be compared with the frequentist KATRIN reference value of 0.20 eV. This is a significant difference when judged relative to the systematic and statistical uncertainties of the experiment. On the other hand, an input m_beta=0.35 eV, which is the KATRIN 5sigma detection threshold, would be detected at virtually the same level. Finally, we combine the simulated KATRIN results with cosmological data in the form of present (post-WMAP) and ...

Energy Technology Data Exchange (ETDEWEB)

This paper deals with electron flux densities and electron energy flux densities in positive column discharges. Recent kinetic calculations by Uhrlandt and Winkler have revealed the interesting physical phenomenon of radially inward directed energy flux densities in positive column plasmas. We have used a self-consistent positive column model, based on an accurate and highly detailed Monte Carlo code, to study this effect in more depth. The results of this study show a rather complex physical picture of electron particle and energy flux densities. Electrons with low energies usually exhibit radially outward directed particle and energy flux densities. At energies above the threshold for electronic excitation particle and energy flux densities are usually inward directed. Only close to the wall, at total energies above the wall potential energy, do these flux densities point towards the wall. The thickness of this 'wall loss ...

Energy Technology Data Exchange (ETDEWEB)

The sub-criticality monitoring system has been developed for criticality safety control in nuclear fuel handling plants. In the past experiments performed with the Deuterium Critical Assembly (DCA), it was confirmed that the detection of sub-criticality was possible to k{sub eff} = 0.3. To investigate the applicability of the method to more generalized system, experiments were performed in the light-water-moderated system of the modified DCA core. From these experiments, it was confirmed that the prompt decay constant ({alpha}), which was a index of the sub-criticality, was detected between k{sub eff} = 0.623 and k{sub eff} = 0.870 and the difference of 0.05 - 0.1{Delta}k could be distinguished. The {alpha} values were numerically calculated with 2D transport code TWODANT and monte carlo code KENO V.a, and the results were compared with the measured values. The differences between calculated and measured values were proved to be less than 13%, ...

Energy Technology Data Exchange (ETDEWEB)

In electron beam therapy, tissue overdose due to electrons backscattered from lead has been profusely studied. To quantify this dose enhancement effect, an electron backscatter factor (EBF) wasdefined as the ratio of dose at the tissue-inhomogeneity interface with and without the scatterer present. The dependence of the EBF on energy at the scatterer surface is not well known for energies lower than 3 MeV which is the most frequent clinical situation. In this work, we have done Monte Carlo calculations with the GEANT code to study EBF in lead at this energy range. The applicability of this code and the developed procedure for dose estimation has been experimentally verified. The dependence of the EBF on the beam energy incident on the scatterer has been studied for different nominal beam energies incident at the phantom's surface. The results show a trend of increase of EBF with the beam energy incident on the scatterer between 0.5 and ...

Energy Technology Data Exchange (ETDEWEB)

Yet designed to measure charged component of the cosmic rays, the foreseen Alpha Magnetic Spectrometer (AMS-02) could also release {gamma}-ray studies, in the energy range from GeV to TeV, using the tracker system, for {gamma}-rays converted in e{sup +}e{sup -} pair, and the electromagnetic calorimeter. In the first part of the thesis are described the calibrations and the performances of the engineering model of the calorimeter, obtained from the analysis of data taken during a test-beam performed at CERN in July 2002. In the second part of the thesis, the AMS-02 discovery potential for {gamma}-astrophysics is presented. While exposure maps of the {gamma}--sky are computed for one year of data taking with the {gamma}--detectors, the acceptance of the calorimeter is obtained from Monte-Carlo simulations. The AMS-02 potential is then estimated for signals from the Vela pulsar and for some supersymmetric signals from the Galactic Center. (author)

International Nuclear Information System (INIS)

While there have been many experimental and calculational investigations on absorbed dose distribution in the patient resulting from conventional X-ray procedures, such data for computerized tomography (CT) are still sparse. As this diagnostic procedure has shown a rapid increase in application during recent years, we have determined absorbed dose to body organs in a human phantom resulting from CT examinations. The exposure model consists of the heterogeneous MIRD-5 phantom and a suitable Monte-Carlo method to calculate absorbed dose to organs of interest. The exposure conditions are specified according to the exposure specifications of a CT-scanner currently in use. The calculations cover the range of body tissues of interest in terms of organ absorbed doses as well as a risk weighted absorbed dose. A detailed example showing the calculation of red bone marrow dose is given and a somatic effective dose equivalent Hsub(ES) is calculated for different conventional ...

CERN Document Server

The idea to couple the Treatment Planning System (TPS) to the information on the real boron distribution in the patient is the main added value of the new methodology set-up at DIMNP of University of Pisa, in collaboration with the JRC of Petten (NL). The methodology has been implemented in the new TPS, called BDTPS (Boron Distribution Treatment Planning System), which takes into account the actual boron distribution in the patient brain, while the standard TPS assumes a uniform boron distribution, absolutely far from the reality. Nowadays, Positron Emission Tomography (PET) is able to provide this in vivo information. The new TPS, based on the Monte Carlo technique, has been validated comparing the main BNCT parameters (thermal flux, boron dose, etc.) as measured during the irradiation of a special heterogeneous boron phantom (HEBOM), ad hoc designed, as calculated by the BDTPS and by the standard TPS SERA. An evident SERA overestimation of ...

Energy Technology Data Exchange (ETDEWEB)

A new atomistic approach to Si device process simulation is presented. It is based on a Monte Carlo diffusion code coupled to a binary collision program. Besides diffusion, the simulation includes recombination of vacancies and interstitials, clustering and re-emission from the clusters, and trapping of interstitials. We discuss the simulation of a typical room-temperature implant at 40 keV, 5{times}10{sup 13} cm{sup {minus}2} Si into (001)Si, followed by a high temperature (815{degree}C) anneal. The damage evolves into an excess of interstitials in the form of extended defects and with a total number close to the implanted dose. This result explains the success of the {open_quote}{open_quote}+1{close_quote}{close_quote} model, used to simulate transient diffusion of dopants after ion implantation. It is also in agreement with recent transmission electron microscopy observations of the number of interstitials stored in (311) defects. ...

International Nuclear Information System (INIS)

Kinetic Monte Carlo simulations are used to analyze the ripening and dissolution of small Si interstitial clusters and #left brace#113#right brace# defects, and its influence on transient enhanced diffusion of dopants in silicon. The evolution of Si interstitial defects is studied in terms of the probabilities of emitted Si interstitials being recaptured by other defects or in turn being annihilated at the surface. These two probabilities are related to the average distance among defects and their distance to the surface, respectively. During the initial stages of the defect ripening, when the defect concentration is high enough and the distance among them is small, Si interstitials are mostly exchanged among defects with a minimal loss of them to the surface. Only when defects grow to large sizes and their concentration decreases, the loss of Si interstitials through diffusion to the surface prevails, causing their dissolution. The presence of ...

Energy Technology Data Exchange (ETDEWEB)

Much of the current technology on 3D-prestack depth migration is based on the Kirchhoff method and the traveltime information needed for this purpose is obtained by the ray-theory approximation. The main motivation driving these options is to reduce computations but it can also have an adverse effect on the quality of results. Experience with real data indicates that the corresponding poststack data migrated by the reverse-time method often yields superior results. Considerable computational efficiency can be obtained by employing nonuniform coarse grid spacing during the reverse-time migration. We followed this strategy for developing a parallel scheme for doing 3D- prestack depth migration. However, we worked only on a small subset of shot gathers whose determined by the Quasi-Monte Carlo method. The results were indistinguishable from those obtained by using a much larger population of uniformly spaced shot gathers. We present examples of ...

Science.gov (United States)

We report here a new approach to introduce the effect of chemisorption in the Monte-Carlo simulation procedure for studying the segregation behaviour in bimetallic nanoparticles at low pressures. A coordination-dependent pair interaction energy is constructed in terms of partial bond energies and the exchange energy where the partial bond energy can be empirically calculated from the experimental values of dimer energy, the pressure-dependent surface energy and the bulk cohesive energy of the constituent metals. The advantage of this procedure is the ability to estimate the pressure-dependent surface composition of the nanoparticles. The method has been applied to oxygen-adsorbed Pd-Ag systems; and it is found that while Ag segregate in clean particles, at higher oxygen pressures Pd atoms segregate to the surface. The present technique has been argued to be suitable for higher pressures (>10-5Torr) when coverage cannot be accurately determined. At low-pressure ...

International Nuclear Information System (INIS)

We present a development of the use of the AAPM TG-43 dose formalism applied to "1"3"7Cs gynecological implant sources. The geometry factor, radial dose function, and anisotropy function of a "1"3"7Cs source modeled after the Nuclear Associates 67-809 series stainless steel jacketed tube source were derived following the AAPM TG-43 formalism. The dose rate distribution through the center of the source using the AAPM TG-43 dose formalism is calculated and compared with the calculations obtained using the Sievert summation and Monte Carlo simulation. The three methods resulted in an agreement within less than 5%, or an isodose rate line agreement within 2 mm. We demonstrate that the AAPM TG-43 formalism can be applied to "1"3"7Cs linear sources and is capable of serving as a "1"3"7Cs dose calculation algorithm that can be used for treatment planning purpose.

International Nuclear Information System (INIS)

Full text: The principal nuclear design tools available to the shielding designer include diffusion approximation, transport theory, and Monte Carlo techniques. Full transport theory or Monte Carlo methods are routinely used for shielding analyses, where penetration investigations are more sensitive to directional aspects. However, the aim of this paper is to illustrate the coupled neutron-gamma Albedo method particularly as applied to problems of shielding analysis. The multigroup Albedo method is applied to coupled neutron-gamma radiations considering 'n' neutron energy groups and 'g' gamma energy groups to estimate the probabilities of transmission through, absorption in, and reflection from shieldings composed by multiple material layers, 'm' slabs, in which no fission occurs. In this study, these energy groups were selected in order to minimize upscattering effects of the radiation from lower ...

Science.gov (United States)

We propose a novel surveillance system that uses hybrid camera network. The system contains a panorama camera and PTZ cameras to take the wide range images and face images at high enough resolution for identification tasks. The robust human detection methods include robust background subtraction method (RRC), skin color segmentation and face tracking method. First, the system detects persons from a panorama image, and then the detailed face images are obtained with the PTZ cameras. The PTZ cameras can track the faces using the four directional features and the relaxation matching. In addition, the system has automatic camera position calibration feature. Thus, the user can use the system without any troublesome settings.

International Nuclear Information System (INIS)

Full text: Radiotherapy treatment planning (RTP) relies heavily on medical imaging. Until recently, the most important planning tool was the treatment simulator. The kilovoltage radiographic capabilities in a treatment simulator enabled the boundaries of treatment fields to be visualized with respect to bony anatomic landmarks. Perhaps the most important advance in treatment planning in recent years is the ability to visualize the passage of the beams with respect to a more accurate geometrical representation of the tumor and other soft tissue structures. This 'virtual simulation' uses a computer-based representation of a patient to determine the extent of the disease and the location of radiation sensitive normal tissue. Computer tomographic (CT) imaging produces a high-resolution three-dimensional representation of anatomy that can be correlated with other image sets such as magnetic resonance images (MRI) of function. Positron emission tomographic (PET) imaging is beginning to be ...

International Nuclear Information System (INIS)

A number of procedures in diagnostic radiology and cardiology make use of long exposures to x-rays from fluoroscopy units. Although numerous studies have been performed to measure or calculate skin dose from these procedures, there have only been a handful of studies to determine the dose to the other organs. This thesis was focused on devising a method to calculate the absorbed dose to underlying tissues and organs. The work was performed in several stages. First, a commercial convolution/superposition-based treatment planning system used in radiation oncology was modified and complemented to make it usable with the low energies of x-rays used in diagnostic radiology. This required generation of energy deposition kernels in the kilovoltage energy range. The kernels were generated using the EGS4 Monte Carlo system of codes and added to the treatment planning system. The treatment planning system was then evaluated for its accuracy of ...

International Nuclear Information System (INIS)

Although low-energy ion radiation has been proven to have a wide range of biological effects and led to fruitful achievements as a new mutagenic source for genetic modification, there still exist some disputes about its mutagenic mechanisms because of its short-penetrating property. In present research, Arabidopsis thaliana transgenic for GUS recombination substrate was used to evaluate the genomic instability induced by irradiations of alpha particle (3.3MeV) and Low-energy-Argon ion (30 KeV). A pronounced effects of alpha particle irradiation to Arabidopsis thaliana seedlings and Argon ion irradiation to seeds on the somatic homologous recombination frequency (sHRF) were reported. The sHRFs increased 1.88-fold and 2.42-fold, respectively, which indicated that the short-penetrating radiation could effectively induce the plant genomic instability in either dry seeds or seedlings with active metabolism. The local alpha particle irradiation of root was performed. Result exhibited ...

Energy Technology Data Exchange (ETDEWEB)

A 2.45 MeV neutron time-of-flight spectrometer was designed and built for measurements of neutron energy spectra from the JT-60U Tokamak. The spectrometer consists of two fast plastic scintillators (50 cm{sup 2} and 1800 cm{sup 2}, thickness: 2 cm) where each detector is located on two constant time-of-flight spheres. The time-of-flight spheres have radius of 1 m which gives a neutron flight length of {approx}164 cm and a time-of-flight of {approx}92 ns for 2.45 MeV source neutrons. The calculated spectrometer efficiency and resolution are 2.8 x 10{sup -2} cm{sup 2} and 105 keV (4.3%), respectively. The energy resolution corresponds to a time resolution of 2.0 ns. The spectrometer will measure neutrons in a vertical line-of-sight, {approx}9 m from the plasma center. For a total neutron emission of 10{sup 16} n/s, the countrate in the first scattering detector, located in the neutron beam, is estimated to {approx}2.5 MHz. The useful countrate for this case is estimated to {approx}6 kHz ...

International Nuclear Information System (INIS)

In earlier works, the inelastic mean free path (IMFP) of electrons was determined by elastic peak electron spectroscopy (EPES) using Ni and Ag reference standard samples, but fully neglecting surface excitation. Surface excitation that is characterized by the surface excitation parameter (SEP), and may affect considerably the elastic peak for the sample and the reference material. The SEP parameters of selected conducting polymers (polythiophenes, polyaniline and polyethylene) were determined by EPES using Si and Ge reference samples. Experiments were made with a hemispherical analyzer of energy resolution 100-200 meV in the E = 0.2-2.0 keV energy range. The composition of the sample surfaces was determined by in situ XPS, their surface roughness by AFM. The experimental SEP parameter data of eight polymer samples were determined by our new procedure, using the formulae of Chen and Werner et al. in the E = 0.2-2.0 keV energy range. The trial and error procedure is based on the best ...

Energy Technology Data Exchange (ETDEWEB)

The mass generation in the Standard Model of Particles Physics relies on a spontaneous symmetry breaking mechanism. Its implementation is recalled, along with its constraints, both theoretical (Naturalness, Stability, Triviality, Unitarity) and experimental (limits of direct and indirect searches, prospects). Calculation techniques for observables evaluation in Perturbative Field Theory are described, particularly Helicity Amplitude method, which is given in details: fermions and vector bosons, massless and massive. Monte-Carlo integration, and structure functions approximations (which allows non-perturbative calculations) are also detailed. With these tools, a process giving to Physics beyond the Standard Model is studied: it leads to an experimental prediction for the LEP collision ring, taking the classical background into account. Technical aspects of a future photon linear collider are reviewed. The production of heavy vector bosons, either the classical Z for ...

International Nuclear Information System (INIS)

Single-crystalline nanostructures often exhibit gradients of surface (and/or interface) curvature that emerge from fabrication and growth processes or from thermal fluctuations. Thus, the system-inherent capillary force can initiate morphological transformations during further processing steps or during operation at elevated temperature. Therefore and because of the ongoing miniaturization of functional structures which causes a general rise in surface-to-volume ratios, solid-state capillary phenomena will become increasingly important: On the one hand diffusion-mediated capillary processes can be of practical use in view of non-conventional nanostructure fabrication methods based on self-organization mechanisms, on the other hand they can destroy the integrity of nanostructures which can go along with the failure of functionality. Additionally, capillarity-induced shape transformations are effected and can thereby be controlled by applied fields and forces (guided or driven ...

Energy Technology Data Exchange (ETDEWEB)

The resident bald eagles of the lower Columbia River have lower productivity and higher contaminant levels than other bald eagles of the Pacific Northwest. The primary population stressors are believed to be habitat loss, human disturbance, p,p{prime}DDE, PCBs, dioxins and furans. The primary effect of habitat loss is to reduce the carrying capacity of the region for nesting sites, and the primary effects of human disturbance and contamination by organic compounds are to reduce productivity. The purpose of this study was to quantitatively evaluate the effects of all of, these potential stressors on the bald eagle population dynamics. A model of the population dynamics was developed. The model structure includes a physiologically-based toxicokinetic (PBTK) submodel to estimate the degree of contamination, which is linked via a toxicology submodel to a population dynamics submodel. The PBTK submodel is time-variable, incorporating species-specific bioenergetics, as well as contaminant ...

Energy Technology Data Exchange (ETDEWEB)

An embodiment of a mercury-free fluorescent lamp combines a low pressure rare gas discharges with a phosphor having a quantum efficiency grater than one. The choice of the rare gas depends on a number of factors, one of which is the resonance transition energy. Less demand is placed the quantum efficiency of the phosphor for a lower energy resonance photon. Xenon has the lowest energy resonance transition of the stable rare gases at 8.5 eV (147 nm) and thus is a good candidate to study. The usefulness of a xenon-based discharge depends on the radiant emittance of the discharge at the resonance wavelength of 147 nm. The radiant emittance from a low pressure xenon positive column discharge is measured using two independent techniques. The first relies on the measurement of the resonance level density using absorption techniques. The effective decay rate of the resonance level is calculated using radiation trapping theory. The product of this density and trapped decay rate yields the ...

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We analyze the timing of photons observed by the MAGIC telescope during a flare of the active galactic nucleus Mkn 501 for a possible correlation with energy, as suggested by some models of quantum gravity (QG), which predict a vacuum refractive index {approx_equal}1+(E/M{sub QGn}){sup n}, n=1,2. Parametrizing the delay between {gamma}-rays of different energies as {delta}t={+-}{tau}{sub l}E or {delta}t={+-}{tau}{sub q}E{sup 2}, we find {tau}{sub l}=(0.030{+-}0.012) s/GeV at the 2.5-{sigma} level, and {tau}{sub q}=(3.71{+-}2.57)x10{sup -6} s/GeV{sup 2}, respectively. We use these results to establish lower limits M{sub QG1}>0.21x10{sup 18} GeV and M{sub QG2}>0.26x10{sup 11} GeV at the 95% C.L. Monte Carlo studies confirm the MAGIC sensitivity to propagation effects at these levels. Thermal plasma effects in the source are negligible, but we cannot exclude the importance of some other source effect.

Energy Technology Data Exchange (ETDEWEB)

Implanted B and P dopants in Si exhibit transient enhanced diffusion (TED) during annealing which arises from the excess interstitials generated by the implant. In order to study the mechanisms of TED, transmission electron microscopy measurements of implantation damage were combined with B diffusion experiments using doping marker structures grown by molecular-beam epitaxy (MBE). Damage from nonamorphizing Si implants at doses ranging from 5{times}10{sup 12} to 1{times}10{sup 14}/cm{sup 2} evolves into a distribution of {l_brace}311{r_brace} interstitial agglomerates during the initial annealing stages at 670{endash}815{degree}C. The excess interstitial concentration contained in these defects roughly equals the implanted ion dose, an observation that is corroborated by atomistic Monte Carlo simulations of implantation and annealing processes. The injection of interstitials from the damage region involves the dissolution of ...

Energy Technology Data Exchange (ETDEWEB)

This lectures aim at giving graduate students an introduction to a working knowledge of path integral methods in a wide variety of fields in physics. Consequently, the the lecture notes are organized in three main parts dealing with non-relativistic quantum mechanics, many-body physics and field theory. In the first part the basic concepts of path integrals are developed in the usual heuristic, non-mathematical way followed by the standard examples of quadratic Lagrangians for which the path integrals can be solved exactly. Applications include semi-classical expansions, scattering problems and the representation of Green functions as path integrals. In the last chapter of this part it is shown how (euclidean) path integrals can be treated numerically by Monte-Carlo methods with a program for the anharmonic oscillator as an explicit example. The second part deals with the application of path integrals in statistical mechanics and many-body problems. Various ...

Energy Technology Data Exchange (ETDEWEB)

Shielding calculations for neutron-gamma radiation are usually done by using the full Theory of Transport or the Monte Carlo Techniques. After some works based on the Albedo Method, the shielding calculations for neutron-gamma radiation have a reliable tool with great didactical value which shows its clarity and simplicity for the resolution of cases that involve neutrons and photon shielding in nonmultiplying media. The excellent results of these works have motivated the elaboration and the development of this study that will be presented in this dissertation. The balance of a neutronic current entering a shield of two layers considering the coupling neutron-gamma will be determined by the Albedo Method. The shield will be composed of a layer of iron and another one of manganese with 10 cm of thickness each. The arrays of the materials coefficients will be obtained from the ANISN code. ANISN is a one dimensional deterministic code that is ...

Energy Technology Data Exchange (ETDEWEB)

Volumetric properties of liquid mixtures of neon and hydrogen have been calculated using path integral hybrid Monte Carlo simulations. Realistic potentials have been used for the three interactions involved. Molar volumes and excess volumes of these mixtures have been evaluated for various compositions at 29 and 31.14 K, and 30 atm. Significant quantum effects are observed in molar volumes. Quantum simulations agree well with experimental molar volumes. Calculated excess volumes agree qualitatively with experimental values. However, contrary to the existing understanding that large positive deviations from ideal mixtures are caused due to quantum effects in Ne{endash}H{sub 2} mixtures, both classical as well as quantum simulations predict the large positive deviations from ideal mixtures. Further investigations using two other Ne{endash}H{sub 2} potentials of Lennard{endash}Jones (LJ) type show that excess volumes are very sensitive to the ...

Energy Technology Data Exchange (ETDEWEB)

Recent efforts to identify methods of modeling pitting corrosion damage of high-level radioactive-waste containers are described. The need to develop models that can provide information useful to higher level system performance assessment models is emphasized, and examples of how this could be accomplished are described. Work to date has focused upon physically-based phenomenological stochastic models of pit initiation and growth. These models may provide a way to distill information from mechanistic theories in a way that provides the necessary information to the less detailed performance assessment models. Monte Carlo implementations of the stochastic theory have resulted in simulations that are, at least qualitatively, consistent with a wide variety of experimental data. The effects of environment on pitting corrosion have been included in the model using a set of simple phenomenological equations relating the parameters of the stochastic ...

Energy Technology Data Exchange (ETDEWEB)

The central topic of this work is the study of the properties and the implementation of a Paul trap used for the measurement of the beta-neutrino angular correlation parameter in the decay of {sup 6}He. This coefficient provides a signature of the nature of the interactions involved in the weak interaction. The value of this coefficient can be deduced from the kinematical distribution of the decay events. An electromagnetic trap is used for the trapping of {sup 6}He{sup +} ions in a small volume. This trap has an open geometry that enables the detection in coincidence of the electron and the recoil ion emitted in the beta decay. A dedicated detection set up is used for the measurement of the electron energy, the ion time of flight and the position of the two particles for each event. A general description of the LPCTrap facility and of its performances is presented and shows that this set up is able to fulfill the proposed measurement. Especially, a comparison is made between the ...

International Nuclear Information System (INIS)

Full text: A Large Sample Neutron Activation Analysis (LSNAA) facility is under development at GRR-1 research reactor, NCSR 'Demokritos'. The LSNAA facility design incorporates sample irradiation in the reactor's graphite thermal neutron column and subsequent measurement of the activity induced at a gamma spectroscopy system with gamma ray transmission measurement options included. Monte Carlo neutron and photon transport code MCNP-4C was used to model the facility. Appropriate correction factors accounting for neutron field perturbation during sample irradiation, high purity germanium detector efficiency for the volume source and gamma ray self-absorption within the sample itself were derived. The results of the computations were experimentally verified by activation foil measurements for a set of known materials and a range of sample sizes extending up to 10 litters. Moreover, the special issue of large sample analysis of non-homogeneous ...

International Nuclear Information System (INIS)

In radiotherapy treatment planning, convolution/superposition algorithms currently represent the best practical approach for accurate photon dose calculation in heterogeneous tissues. In this work, the implementation, accuracy and performance of the FFT convolution (FFTC) and multigrid superposition (MGS) algorithms are presented. The FFTC and MGS models use the same 'TERMA' calculation and are commissioned using the same parameters. Both models use the same spectra, incorporate the same off-axis softening and base incident lateral fluence on the same measurements. In addition, corrections are explicitly applied to the polyenergetic and parallel kernel approximations, and electron contamination is modelled. Spectra generated by Monte Carlo (MC) modelling of treatment heads are used. Calculations using the MC spectra were in excellent agreement with measurements for many linear accelerator types. To speed up the calculations, a number of ...

Energy Technology Data Exchange (ETDEWEB)

This project investigated new techniques for improving seismic event locations derived from regional and local networks. The technqiues include a new approach to empirical travel-time calibration that simultaneously fits data from multiple stations and events, using a generalization of the kriging method, and predicts travel-time corrections for arbitrary event-station paths. We combined this calibration approach with grid-search event location to produce a prototype new multiple-event location method that allows the use of spatially well-distributed events and takes into account correlations between the travel-time corrections from proximate event-station paths. Preliminary tests with a high quality data set from Nevada Test Site explosions indicated that our new calibration/location method offers improvement over the conventional multiple-event location methods now in common use, and is applicable to more general event-station geometries than the conventional methods. The tests were ...

International Nuclear Information System (INIS)

We have constructed a Monte Carlo generator (the corresponding FORTRAN code can be obtained from the authors upon request) for lowest-order predictions for the processes #gamma##gamma##->#4f and #gamma##gamma##->#4f#gamma# in the standard model and extensions thereof by an effective #gamma##gamma#H coupling as well as anomalous triple and quartic gauge-boson couplings. Polarization is fully supported, and a realistic photon beam spectrum can be taken into account. For the processes #gamma##gamma##->#4f all helicity amplitudes are explicitly given in a compact form. The presented numerical results contain, in particular, a survey of cross sections for representative final states and their comparison to results obtained with the program package Whizard/Madgraph. The impact of a realistic beam spectrum on cross sections and distributions is illustrated. Moreover, the size of various contributions to cross sections, such as from weak ...

International Nuclear Information System (INIS)

The feasibility of using a multileaf collimator (MLC) for grid therapy is demonstrated in this study. Grids with the projected field openings of 10 mmx10 mm and 5 mmx5 mm were created using multiple MLC-shaped fields. The deposited doses were measured with films at different depths in a solid water phantom and compared to those of Cerrobend grid collimators of similar hole sizes and hole separations. At the depth of maximum dose (d_m_a_x), the valley-to-peak dose ratios of the MLC grids were found to be about 11% and 19% for the respective 10 mmx10 mm and 5 mmx5 mm grid openings, and those of the corresponding grid blocks were about 15% and 20%. To quantify the dose contributed by transmission in the blocked areas due to the limited leaf thickness, Monte Carlo simulations (based on convolution/superposition method) were performed to calculate the doses in the solid water phantom using an ideal MLC with no leakage and perfect divergence in both ...

International Nuclear Information System (INIS)

The Neutral Beam Test Facility (NBTF) to be realized in Padoa will test the Neutral Beam Injection (NBI), one of the Heating and Current Drive Systems foreseen for ITER. The NBI is based on the acceleration of hydrogen or deuterium negative ions up to 1 MeV. This work has been aimed at assessing the tritium release from the NBTF in order to provide data for the safety analysis. In particular, the diffusion of the tritium through the neutral beam target material (the CuCrZr alloy calorimeter panels) has been assessed by using literature data of the diffusion coefficient. The tritium generated inside the calorimeter panels moves into both the vacuum and water side: the tritium diffusion flux has been evaluated during the beam-on (200 deg. C) and the beam-off (20 deg. C) phases of the NBTF experiments consisting of an interim campaign and a final test. The penetration depth of the tritium through the 2 mm thick CuCrZr alloy material has been also evaluated by using a ...

Energy Technology Data Exchange (ETDEWEB)

Cross sections for some electro- and photoinduced spallation reactions on {sup 27}Al and {sup 51}V are measured in the energy region 130 MeV to 580 MeV with the activation method. Comparisons are made with calculations based on the Dalitz formalism for virtual photon spectra, and Monte Carlo calculations based on a cascade evaporation model, respectively. By use of Bremsstrahlung with end-point energies from threshold to 750 MeV, the yields for photo- production of{pi}{sup -}leading to ground and isomeric states in {sup 197}Hg are measured with the activation method. The activity from the Hg-isotopes were measured after a chemical separation of Hg from the target material. The yields and isomeric ratios are compared with impulse approximation calculations. For the photoproduction of {sup 195m}Hg and {sup 192}Hg from {sup 197}Au, the yields were measured. The experimental mean cross sections are compared with data from other experiments and with ...

Energy Technology Data Exchange (ETDEWEB)

The proton beam has a unique advantage over the electron and photon beams in that it can give very high radiation dose to the tumor volume, while effectively sparing the neighboring healthy tissue and organs. For the clinical application of the proton beam, it is very important to confirm the location of the proton beam in the patient, preferentially during the treatment. It has been suggested that the range of the proton beam in the patient can be determined by measuring prompt gammas from the proton beam passage. Recently, a prototype prompt-gamma scanning system has been constructed and tested using experimental and therapeutic proton beams. The measurement results for the proton beams of 70 . 230 MeV showed that a clear correlation exists between the distribution of the prompt gammas and the proton beam range. The scanning method, however, is not suitable for the upcoming 'spot scanning' technique. The 'spot scanning' technique provides ...

Energy Technology Data Exchange (ETDEWEB)

Mechanisms and associated energetics for adatom diffusion on the (100) and (110) surfaces of Ni, Cu, Rh, Pd, and Ag are investigated. Self-diffusion was studied on (100) and (I 10) surfaces of Ni, Cu, Pd and Ag using corrected effective medium method (CEM) and approximation to CEM used for molecular dynamics and Monte Carlo studies (MD/MC-CEM). Self-diffusion on Pd(100), Ag(100), Ni(110), Cu(110), Pd(110), and Ag(110) is accomplished by classical diffusion: the adatom hops from its equilibrium adsorption site over an intervening bridge site to an adjacent equilibrium site. Self-diffusion on Ni(100) and Cu(100) proceeds by atomic-exchange diffusion: the adatom on the surface displaces an atom in the first surface layer. Aside from explicit inclusion of the kinetic-exchange-correlation energy, it is critical to include enough movable atoms in the calculation to insure correct energetics. Distortions induced by these diffusion mechanisms, ...

International Nuclear Information System (INIS)

The field of neutron imaging has a broad scope of applications and has played a pivotal role in visualizing and quantifying hydrogenous masses in metallic matrices. The field continues to expand into new applications with the installation of new neutron imaging facilities. In this scope, a neutron imaging facility for computed tomography and real-time neutron radiography is currently being developed around 2.0 MW TRIGA MARK-II Reactor at Maamora Nuclear Research Centre in Morocco (CENM). The neutron imaging facility consists of a neutron collimator, a real-time neutron imaging system and imaging process systems. In order to reduce the gamma-ray content in the neutron beam, the reactor tangential channel was selected. For power of 250 kW, the corresponding thermal neutron flux measured at the inlet of the tangential channel is around 3.1011 n*cm2/s. This facility will be based on a conical neutron collimator with two circular diaphragms with diameters of 4 cm and 2 cm corresponding to ...

International Nuclear Information System (INIS)

A high resolution Compton telescope has been identified by the Gamma Ray Astronomy Program Working Group (GRAPWG) as the highest priority major mission in gamma ray astrophysics following GLAST. This mission should provide 25-100 times improved sensitivity, relative to CGRO and INTEGRAL, for MeV gamma ray lines. It must have good performance for narrow and broad lines and for discrete and diffuse emissions. Several instrumental approaches are being pursued to achieve these goals. We discuss issues relating to this mission including alternative detector concepts, instrumental configurations, and background reduction techniques. We have pursued the development of position-sensitive solid-state detectors (Ge, Si) for a high spectral resolution Compton telescope mission. A #approx#1 m2 germanium Compton telescope of position-sensitive germanium detectors was the basis for one of the GRAPWG concepts. Preliminary Monte Carlo estimates for the ...

International Nuclear Information System (INIS)

The response of MOS capacitors to low- and medium-energy x-ray irradiation is investigated as a function of gate material (TaSi or Al), oxide thickness, and electric field. Measured device response is compared with predictions based on discrete ordinates and Monte Carlo code simulations of dose enhancement effects, coupled with recent estimates of electron-hole recombination in MOS oxides. In comparisons of 10-keV x-ray and Co-60 irradiations of Al-gate MOS capacitors at an oxide electric field of 1 MV/cm, it is found that predictions and experiments agree to within better than 20 percent for oxide thicknesses ranging from 35 to 1060 nm. For capacitors having TaSi/Al gates, predictions and experiments agree to within better than 30 percent at 1 MV/cm, with the largest differences occurring for 35-nm gate oxides. At other electric fields, the disagreement between experiment and prediction increases significantly for both Al- and TaSi/Al-gate ...

Energy Technology Data Exchange (ETDEWEB)

The calibration of cylindrical detectors using different types of radioactive sources is a matter of routine. The most accurate method, that of experiment, is limited by several factors when the energy interval is broad, requiring a relatively large number of primary standards, implying considerable investment of money and time. Several other techniques can be used instead, including Monte Carlo simulations and semi-empirical methods. Calculations based on the first technique require good definition of the geometry and materials, including the dead layer and window thickness together with an accurate set of cross-sections. The second technique requires two different types of experimental input, the first being from use of sources emitting cascade {gamma} rays and the second from use of sources emitting isolated {gamma} rays in order to cover the wide energy range and provide coincidence-summing corrections, respectively. Here, we introduce a ...

Energy Technology Data Exchange (ETDEWEB)

Subcritical experiments using californium source-driven noise analysis (CSDNA) and Feynman variance-to-mean methods were performed with an alpha-phase plutonium sphere reflected by nickel shells, up to a maximum thickness of 7.62 cm. Both methods provide means of determining the subcritical multiplication of a system containing nuclear material. A benchmark analysis of the experiments was performed for inclusion in the 2010 edition of the International Handbook of Evaluated Criticality Safety Benchmark Experiments. Benchmark models have been developed that represent these subcritical experiments. An analysis of the computed eigenvalues and the uncertainty in the experiment and methods was performed. The eigenvalues computed using the CSDNA method were very close to those calculated using MCNP5; however, computed eigenvalues are used in the analysis of the CSDNA method. Independent calculations using KENO-VI provided similar eigenvalues to those determined using the CSDNA method and ...

Energy Technology Data Exchange (ETDEWEB)

The principal mathematical tools frequently available for calculations in Nuclear Engineering, including coupled neutron-gamma radiations shielding problems, involve the full Transport Theory or the Monte Carlo techniques. The Multigroup Albedo Method applied to shieldings is characterized by following the radiations through distinct layers of materials, allowing the determination of the neutron and gamma fractions reflected from, transmitted through and absorbed in the irradiated media when a neutronic stream hits the first layer of material, independently of flux calculations. Then, the method is a complementary tool of great didactic value due to its clarity and simplicity in solving neutron and/or gamma shielding problems. The outstanding results achieved in previous works motivated the elaboration and the development of this study that is presented in this dissertation. The radiation balance resulting from the incidence of a neutronic ...

Science.gov (United States)

The performance of intermolecular potential models on the adsorption of carbon tetrachloride on graphitized thermal carbon black at various temperatures is investigated. This is made possible with the extensive experimental data of Machin and Ross(1), Avgul et al.,(2) and Pierce(3) that cover a wide range of temperatures. The description of all experimental data is only possible with the allowance for the surface mediation. If this were ignored, the grand canonical Monte Carlo (GCMC) simulation results would predict a two-dimensional (2D) transition even at high temperatures, while experimental data shows gradual change in adsorption density with pressure. In general, we find that the intermolecular interaction has to be reduced by 4% whenever particles are within the first layer close to the surface. We also find that this degree of surface mediation is independent of temperature. To understand the packing of carbon tetrachloride in slit ...

Energy Technology Data Exchange (ETDEWEB)

This paper presents a stochastic model and estimation procedure for analyzing the failure process of a repairable system. We consider repairable systems whose successive interfailure times reveal a significant dependence while showing an insignificant trend. Neither the renewal process nor the non-homogeneous Poisson process are adequate for modeling such failure processes. Especially when the interfailure times show a cyclic pattern, we may consider a switching of the regimes (states) governing the lifetime distribution of the system. We propose a Markov switching model describing the failure process for such a case. The model postulates that a finite number of states governs the distinct lifetime distributions, and the state makes transitions according to a discrete-time Markov chain. Each of the distinct lifetime distributions represents a failure type that may change after successive repairs. Our model generalizes the mixture model by allowing the mixture probabilities to change ...

Energy Technology Data Exchange (ETDEWEB)

Selecting the best bit for an application is a difficult task because a large number of variables can influence bit performance, therefore upon a decision to run a particular bit type based solely on the average measurements of previous bit performances can lead to a very important impact on the drilling cost. Bits are designed with different concepts and that recent technological advances allow them to be used in a wider range of applications that could improve their drilling programs. Rather than a deterministic estimate, a more mature view of a bit performance is a presentation of possible outputs (bits longevity in drilled meters, rate of penetration, bit cost and cost per meter) in recognition of the uncertainty associated with drilling wells. An evaluation of a simple model based on the drilling cost equation indicates the sensitivity of each variable - described here by its probability distribution function - on the bottom line and can be a very effective decision tool to set ...

Science.gov (United States)

Jan 13, 2011 ... This 360-degree mosaic of images from the navigation camera on ... The Radiation Assessment Detector, shown prior to its September 2010 ...

Science.gov (United States)

Dec 4, 1998 ... throwing a single switch to as complex as the Spartan deploy and retrieve. ...... The camera, called the Acousto-Optic ...

Science.gov (United States)

(telescopes, cameras, mirrors, solar cookers); Explain to students that the Genesis spacecraft has a concentrator that collects special types of atoms from ...

British Library Electronic Table of Contents (United Kingdom)

In the autonomous unmanned helicopter landing problem, the position of the unmanned helicopter relative to the landmark is very important. A camera carried on the unmanned helicopter can capture an image of the landmark. In earlier research, it was reported that the camera position could be estimated by features extracted from the landmark image. However, it is necessary that the landmark image should be complete, or with only slight deficiencies, in order for this estimation process to be possible. In this article, we report on an innovative design for an estimation made from a camera position giving an incomplete single image of the landmark. An adaptive neuro-fuzzy inference system (ANFIS) is used to construct the mapping relation between the features of complete and incomplete landmark...

International Nuclear Information System (INIS)

The Polarized Gamma-ray Observer (PoGOLite) is a balloon-borne instrument that will measure gamma-ray polarization in the energy range 25-80 keV from astronomical sources such as pulsars, accretion discs and jets from active galactic nuclei. The two additional parameters provided by such observations, polarization angle and degree, will allow these objects to be studied in a new way, providing information about their emission mechanisms and geometries. The instrument measures azimuthal scattering angles of photons within a close packed array of phoswich detector cells (PDCs) based on coincident detection of Compton scattering and photoelectric absorption. Each PDC comprises three different scintillating components and combines photon detection, active collimation and bottom anticoincidence into one single unit. The three parts are viewed by a photomultiplier tube (PMT) and pulse shape discrimination is used to identify signals from dierent parts. Surrounding the detector array is a ...

Energy Technology Data Exchange (ETDEWEB)

The Fermi National Laboratory (Fermilab) operates the Tevatron proton-antiproton collider at a center-of-mass energy of {radical}s = 1.96 TeV, the is therefore the only collider which is today able to produce the heaviest known particle, the top quark. The top quark was discovered at the Tevatron by the CDF and D0 collaborations in 1995. At the Tevatron, most top quarks are produced via the strong interaction, whereby quark-antiquark annihilation dominates with 85%, and gluon fusion contributes with 15%. Considering next-to-leading order (NLO) contributions in the cross section of top-antitop quark production, leads to a slight positive asymmetry in the differential distribution of the production angle {alpha} of the top quarks. This asymmetry is due to the interference of certain NLO contributions. The charge asymmetry A in the cosine of {alpha} is predicted [14] to amount to 4-6%. Information about the partonic rest frame, necessary for a measurement of A in the observable cos ...

Energy Technology Data Exchange (ETDEWEB)

The measurement of thyroidal uptake of radioiodine using a gamma camera and computer is described. In 12 children there was good agreement with simultaneous measurements using a probe, while in a further 14 patients the uptake values were consistent with the clinical diagnosis. The technique should be especially useful for infants and small children.

International Nuclear Information System (INIS)

A real-time neutron radiography imaging system has been installed at the Texas A and M University Nuclear Science Center. The system employs a scintillating screen viewed by a low-light TV camera with a front surface mirror placed at 45deg to the neutron beam. The key components of the system are the neutron camera and the image capture and processing unit. The neutron camera uses an NE 426 scintillating screen (ZnS), front surface mirror, remote focus and zoom lens, intensified relay optics (IRO) and monochrome CCD television camera. The image capture and processing unit consists of an IBM PC AT-compatible computer, arithmetic frame grabber, frame processor and high-resolution color monitor. The neutron camera is similar to others using a silicon intensified target (SIT) television camera to provide a TV image of the low-level light from a NE 426 screen. The ...

International Nuclear Information System (INIS)

The results of experiments received on the plasma focus (PF) device with energy stored equal 4 kJ are represented. Photos of the current plasma sheath (CPS), pre-pinch, sphere-like plasma formations are produced with help of the electron-optical converter contained a gated micro-channel plate (MCP) and the CCD-camera imaging system in the visible region. The redial velocity of the CPS is about 107 cm/s. Neon plasma electron density measured with help of the interferograms in the visible region and the spectra in the soft X-ray region is equals to 3?1018 cm-3. Electron temperature is equal to about 200 eV. Discharge integral photos were obtained with help of the soft X-ray pinhole camera. Pictures with 2 ?s resolution of the plasma luminescence above PF anode region were made by CCD-camera.

International Nuclear Information System (INIS)

1 - Description or function: Continuous energy cross-section data library for the Monte Carlo program MCNP based on the JEF-2.2 evaluated nuclear data library (ACE Format). Format: ACE Number of groups: Continuous energy Nuclides (107): H-1, H-2, He-4, Li-6, Li-7, Be-9, B-10, B-11, C-nat, N-14, N-15, O-16, O-17, F-19, Na-23, Mg-nat, Al-27, Si-nat, Cl-nat, Ti-nat, Cr-50, Cr-52, Cr-53, Cr-54, Mn-55, Fe-54, Fe-56, Fe-57, Fe-58, Co-59, Ni-58, Ni-60, Ni-61, Ni-62, Ni-64, Zr-90, Zr-91, Zr-92, Zr-94, Zr-96, Zr-nat, Nb-93, Mo-92, Mo-94, Mo-95, Mo-96, Mo-97, Mo-98, Mo-100, Mo-nat, Tc-99, Ru-101, Ru-102, Ru-104, Rh-103, Pd-105, Pd-107, Ag-109, I-129, Xe-131, Cs-133, Pr-141, Nd-143, Nd-145, Pm-147, Sm-147, Sm-149, Sm-150, Sm-151, Sm-152, Eu-153, Gd-154, Gd-155, Gd-156, Gd-157, Gd-158, Gd-160, Hf-174, Hf-176, Hf-177, Hf-178, Hf-179, Hf-180, Pb-nat, Bi-209, Th-232, U-234, U-235, U-236, U-238, Np-237, Pu-238, Pu-239, Pu-239bis, Pu-240, Pu-241, Pu-242, ...