A Modified Treatment Of Sources In Implicit Monte Carlo Radiation Transport
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A Modified Treatment Of Sources In Implicit Monte Carlo Radiation Transport
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Author :
language : en
Publisher:
Release Date : 2011
A Modified Treatment Of Sources In Implicit Monte Carlo Radiation Transport written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with categories.
We describe a modification of the treatment of photon sources in the IMC algorithm. We describe this modified algorithm in the context of thermal emission in an infinite medium test problem at equilibrium and show that it completely eliminates statistical noise.
Analytic Treatment Of Source Photon Emission Times To Reduce Noise In Implicit Monte Carlo Calculations
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Author :
language : en
Publisher:
Release Date : 2012
Analytic Treatment Of Source Photon Emission Times To Reduce Noise In Implicit Monte Carlo Calculations written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with categories.
Statistical uncertainty is inherent to any Monte Carlo simulation of radiation transport problems. In space-angle-frequency independent radiative transfer calculations, the uncertainty in the solution is entirely due to random sampling of source photon emission times. We have developed a modification to the Implicit Monte Carlo algorithm that eliminates noise due to sampling of the emission time of source photons. In problems that are independent of space, angle, and energy, the new algorithm generates a smooth solution, while a standard implicit Monte Carlo solution is noisy. For space- and angle-dependent problems, the new algorithm exhibits reduced noise relative to standard implicit Monte Carlo in some cases, and comparable noise in all other cases. In conclusion, the improvements are limited to short time scales; over long time scales, noise due to random sampling of spatial and angular variables tends to dominate the noise reduction from the new algorithm.
A Monte Carlo Primer
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Author : Stephen A. Dupree
language : en
Publisher: Springer Science & Business Media
Release Date : 2012-09-07
A Monte Carlo Primer written by Stephen A. Dupree and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012-09-07 with Science categories.
The mathematical technique of Monte Carlo, as applied to the transport of sub-atomic particles, has been described in numerous reports and books since its formal development in the 1940s. Most of these instructional efforts have been directed either at the mathematical basis of the technique or at its practical application as embodied in the several large, formal computer codes available for performing Monte Carlo transport calculations. This book attempts to fill what appears to be a gap in this Monte Carlo literature between the mathematics and the software. Thus, while the mathematical basis for Monte Carlo transport is covered in some detail, emphasis is placed on the application of the technique to the solution of practical radiation transport problems. This is done by using the PC as the basic teaching tool. This book assumes the reader has a knowledge of integral calculus, neutron transport theory, and Fortran programming. It also assumes the reader has available a PC with a Fortran compiler. Any PC of reasonable size should be adequate to reproduce the examples or solve the exercises contained herein. The authors believe it is important for the reader to execute these examples and exercises, and by doing so to become accomplished at preparing appropriate software for solving radiation transport problems using Monte Carlo. The step from the software described in this book to the use of production Monte Carlo codes should be straightforward.
Suppressing Nonphysical Overheating With A Modified Implicit Monte Carlo Method For Time Dependent Radiative Transfer
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Author :
language : en
Publisher:
Release Date : 2008
Suppressing Nonphysical Overheating With A Modified Implicit Monte Carlo Method For Time Dependent Radiative Transfer written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2008 with categories.
In this note we develop a robust implicit Monte Carlo (IMC) algorithm based on more accurately updating the linearized equilibrium radiation energy density. The method does not introduce oscillations in the solution and has the same limit as [Delta]t→∞ as the standard Fleck and Cummings IMC method. Moreover, the approach we introduce can be trivially added to current implementations of IMC by changing the definition of the Fleck factor. Using this new method we develop an adaptive scheme that uses either standard IMC or the modified method basing the adaptation on a zero-dimensional problem solved in each cell. Numerical results demonstrate that the new method alleviates both the nonphysical overheating that occurs in standard IMC when the time step is large and significantly diminishes the statistical noise in the solution.
Monte Carlo Methods For Radiation Transport
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Author : Oleg N. Vassiliev
language : en
Publisher: Springer
Release Date : 2016-10-17
Monte Carlo Methods For Radiation Transport written by Oleg N. Vassiliev and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016-10-17 with Science categories.
This book is a guide to the use of Monte Carlo techniques in radiation transport. This topic is of great interest for medical physicists. Praised as a "gold standard" for accurate radiotherapy dose calculations, Monte Carlo has stimulated a high level of research activity that has produced thousands of papers within the past few years. The book is designed primarily to address the needs of an academically inclined medical physicist who wishes to learn the technique, as well as experienced users of standard Monte Carlo codes who wish to gain insight into the underlying mathematics of Monte Carlo algorithms. The book focuses on the fundamentals—giving full attention to and explaining the very basic concepts. It also includes advanced topics and covers recent advances such as transport of charged particles in magnetic fields and the grid-based solvers of the Boltzmann equation.
Source Tilting Within The Difference Formulation For Radiation Transport
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Author :
language : en
Publisher:
Release Date : 2006
Source Tilting Within The Difference Formulation For Radiation Transport written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2006 with categories.
We apply a heuristic technique known as 'source tilting' to a Monte Carlo solution for radiation transport, in the difference formulation, that otherwise employs a piecewise-constant treatment of the material temperature. Source tilting improves the accuracy of the piecewise-constant treatment, reducing the excessive energy flow that occurs in the thick limit. An analysis of the cause of excessive energy flow suggests an interpolation scheme that removes this defect, obtaining the correct diffusion limit flux between zones. The results obtained with our interpolation scheme agree almost identically to those of a self-consistent piecewise-linear treatment of the difference formulation while avoiding its additional costs. The resulting method is capable of providing robust and accurate calculations for problems involving optically thick zones. We comment on the monotonicity issues that arise when employing this transport method.
Reduced Variance For Material Sources In Implicit Monte Carlo
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Author :
language : en
Publisher:
Release Date : 2012
Reduced Variance For Material Sources In Implicit Monte Carlo written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with categories.
Implicit Monte Carlo (IMC), a time-implicit method due to Fleck and Cummings, is used for simulating supernovae and inertial confinement fusion (ICF) systems where x-rays tightly and nonlinearly interact with hot material. The IMC algorithm represents absorption and emission within a timestep as an effective scatter. Similarly, the IMC time-implicitness splits off a portion of a material source directly into the radiation field. We have found that some of our variance reduction and particle management schemes will allow large variances in the presence of small, but important, material sources, as in the case of ICF hot electron preheat sources. We propose a modification of our implementation of the IMC method in the Jayenne IMC Project. Instead of battling the sampling issues associated with a small source, we bypass the IMC implicitness altogether and simply deterministically update the material state with the material source if the temperature of the spatial cell is below a user-specified cutoff. We describe the modified method and present results on a test problem that show the elimination of variance for small sources.
Use Of Implicit Monte Carlo Radiation Transport With Hydrodynamics And Compton Scattering
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Author :
language : en
Publisher:
Release Date : 1971
Use Of Implicit Monte Carlo Radiation Transport With Hydrodynamics And Compton Scattering written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1971 with categories.
The purpose of this note is to show that the combination of implicit radiation transport and hydrodynamics, Compton scattering, and any other energy transport or exchange mechanism can be simply carried out by a splitting procedure. This means that the contributions to material energy exchange can be reckoned separately for hydrodynamics, radiation transport without scattering, Compton scattering, plus any other possible energy exchange mechanism. The radiation transport phase of the calculation would of course be implicit and would be carried out in exactly the manner described in UCRL-7294 but the hydrodynamics and Compton portions would not, leading to possible time step controls. In any case, the time step restrictions which occur on radiation transfer due to large Planck mean absorption cross-sections would not occur.
Monte Carlo Methods For Particle Transport
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Author : Alireza Haghighat
language : en
Publisher: CRC Press
Release Date : 2020-08-09
Monte Carlo Methods For Particle Transport written by Alireza Haghighat and has been published by CRC Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2020-08-09 with Mathematics categories.
Fully updated with the latest developments in the eigenvalue Monte Carlo calculations and automatic variance reduction techniques and containing an entirely new chapter on fission matrix and alternative hybrid techniques. This second edition explores the uses of the Monte Carlo method for real-world applications, explaining its concepts and limitations. Featuring illustrative examples, mathematical derivations, computer algorithms, and homework problems, it is an ideal textbook and practical guide for nuclear engineers and scientists looking into the applications of the Monte Carlo method, in addition to students in physics and engineering, and those engaged in the advancement of the Monte Carlo methods. Describes general and particle-transport-specific automated variance reduction techniques Presents Monte Carlo particle transport eigenvalue issues and methodologies to address these issues Presents detailed derivation of existing and advanced formulations and algorithms with real-world examples from the author’s research activities
Scoring Methods For Implicit Monte Carlo Radiation Transport
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Author :
language : en
Publisher:
Release Date : 1981
Scoring Methods For Implicit Monte Carlo Radiation Transport written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1981 with categories.
Analytical and numerical tests were made of a number of possible methods for scoring the energy exchange between radiation and matter in the implicit Monte Carlo (IMC) radiation transport scheme of Fleck and Cummings. The interactions considered were effective absorption, elastic scattering, and Compton scattering. The scoring methods tested were limited to simple combinations of analogue, linear expected value, and exponential expected value scoring. Only two scoring methods were found that produced the same results as a pure analogue method. These are a combination of exponential expected value absorption and deposition and analogue Compton scattering of the particle, with either linear expected value Compton deposition or analogue Compton deposition. In both methods, the collision distance is based on the total scattering cross section.