Radiation computer simulations

S. lida, Y. Aoki, K. Okitsu, Y. Sugita, H. Kawata, T. Abe. Microdefects in an as-grown Czochralski silicon crystal studied by synchrotron radiation section topography with aid of computer simulation. Jpn J Appl Phys Ptl 57 241, 1998. 

With time-dependent computer simulation and visualization we can give the novices to QM a direct mind s eye view of many elementary processes. The simulations can include interactive modes where the students can apply forces and radiation to control and manipulate atoms and molecules. They can be posed challenges like trapping atoms in laser beams. These simulations are the inside story of real experiments that have been done, but without the complexity of macroscopic devices. The simulations should preferably be based on rigorous solutions of the time dependent Schrddinger equation, but they could also use proven approximate methods to broaden the range of phenomena to be made accessible to the students. Stationary states and the dynamical transitions between them can be presented as special cases of the full dynamics. All these experiences will create a sense of familiarity with the QM realm. The experiences will nurture accurate intuition that can then be made systematic by the formal axioms and concepts of QM. 

Table II shows, as an example, the combinations of low and high levels for three factors selected by a design team for an accelerated test Involving photovoltaic solar cells. In column 2 the three factors are seen to be temperature T (50 C, 95 C), relative humidity RH (60%, 85%), and ultraviolet radiation UV (five suns, 15 suns). The eight combinations of the high and low levels are shown, together with the predicted months to failure for each combination. In this example the documentation to support each prediction is symbolically referenced as shown in the last column. The documentation includes assumptions, calculations, references to the literature, laboratory data, computer simulation results, and other related material. Such a factorial table is first completed by each scientist independently. Subsequently, the team alms to generate a single consensus factorial table has the same form as that shown in Table II.

Bartczak, W.M. Computer Simulation of Early Physico-Chemical Processes in Irradiated Media. In Properties and Reactions of Radiation Induced Transient Species, Selected Topics, Mayer, J., Ed. Polish Scientific Publishers Warsawa, 1999 101 pp. 

T o grasp the chemical condition of water in the pressure vessel, direct measurement is practically impossible because of high pressure, high temperature, and intense radiation. In order to predict the concentrations of water decomposition products, a computer simulation should be applied. This idea was found in 1960s [1-3]. To perform the simulation, both a set of G-values for water decomposition products and a set of reactions for transient species are necessary. For these two decades, much effort has been made in Sweden, Denmark, United Kingdom, Canada, and Japan to evaluate the G-values and rate constants of the reactions at elevated temperatures up to 300 °C, and now there are practically enough accumulated data. There are several reviews of water radiolysis at elevated temperatures [4-7] and examples of practical application of the radiolysis in reactors [8,9]. 

Thanks to Ron Rohrer, Larry Nagel, and all the students at the University of California, Berkeley, who worked hard in 1969 and 1970 to develop the first computer simulation software, Cancer (Computer Analysis of Non-Linear Circuits Excluding Radiation). This effort would result in the release of SPICE into the public domain in 1971. 

Ternary and Other Induced Spectra. Three-particle induced dipoles and the associated ternary collision-induced absorption spectra and dipole autocorrelation functions have been studied for fluids composed of mixtures of rare gases, and for neat fluids of nonpolar molecules — that is for systems that are widely thought to interact with radiation only by virtue of interaction-induced properties. A convenient framework is thus obtained for understanding the variety of experimental observations. The computer simulation studies permit an insight into the involved basic processes, but were not intended for direct comparison with measurements [57]. Methods have been developed for computer... 

In our opinion, this book demonstrates clearly that the formalism of many-point particle densities based on the Kirkwood superposition approximation for decoupling the three-particle correlation functions is able to treat adequately all possible cases and reaction regimes studied in the book (including immobile/mobile reactants, correlated/random initial particle distributions, concentration decay/accumulation under permanent source, etc.). Results of most of analytical theories are checked by extensive computer simulations. (It should be reminded that many-particle effects under study were observed for the first time namely in computer simulations [22, 23].) Only few experimental evidences exist now for many-particle effects in bimolecular reactions, the two reliable examples are accumulation kinetics of immobile radiation defects at low temperatures in ionic solids (see [24] for experiments and [25] for their theoretical interpretation) and pseudo-first order reversible diffusion-controlled recombination of protons with excited dye molecules [26]. This is one of main reasons why we did not consider in detail some of very refined theories for the kinetics asymptotics as well as peculiarities of reactions on fractal structures ([27-29] and references therein). 

The computer simulation makes it possible to calculate the spatial and energy distribution of ejected electrons and the distribution of ions and excited molecules at different distances from the axis of the track.12"14. Knowing the spatial and energy structure of the track, one can determine the features of primary radiation-chemical reactions in tracks of particles of different nature,15 as well as to describe the evolution of the track and to calculate the yield of radiolysis products.16... 

After 14 years on the faculty of Imperial College, Jacobs moved from London, England, to London, Ontario, where his research program focused on the optical and electrical properties of ionic crystals, as well as on the experimental and theoretical determination of thermodynamic and kinetic properties of crystal defects.213 Over the years his research interests have expanded to include several aspects of computer simulations of condensed matter.214 He has developed algorithms215 for molecular dynamics studies of non-ionic and ionic systems, and he has carried out simulations on systems as diverse as metals, solid ionic conductors, and ceramics. The simulation of the effects of radiation damage is a special interest. His recent interests include the study of perfect and imperfect crystals by means of quantum chemical methods. The corrosion of metals is being studied by both quantum chemical and molecular dynamics techniques. 

T. Diaz de la Rubia, G. H. Gilmer, and M.-J. Caturla, Computer Simulation of Radiation Effects in Solids. Proceedings of the Second International Conference on Computer Simulation of Radiation Effects in Solids, Santa Barbara, CA, July 24-29, 1994, in Nucl. Instrum. Methods Phys. Res., Sect. B, 102 (1-4), North-Holland, Amsterdam, The Netherlands, 1995. 

Chatterjee A, Holley WR. (1993) Computer-simulation of initial events in the biochemical-mechanisms of DNA-damage. Adv Radiat Biol 17 181-226. Goodhead DT, Leenhouts HP, Paretzke, HG, Terrisol M, Nikjoo H, Blaauboer 1C (1994) Track structure approaches to the interpretation of radiation effects on DNA. Radiat Prot Dosim 52 217-223. 

As mentioned above. Vineyard s group at Brokhaven was the first one to use computer simulations for radiation damage studies [3]. Their simulations showed that Frenkel pairs are produced in metals as a result of replacement collision sequences (RCS), where one atom replaces its neighbor in a chain of events that results in a separation of a few atomic distances between the vacant site and the interstitial atom. 

The study of radiation damage by J.B. Gibson, A.N. Goland, M. Milgram and G.H. Vineyard, Phys. Rev., 120 (1960) 1229-1253, employed computer simulation methods and, while not focusing on statistical mechanical aspects of the problem, did introduce methods that were similar to those used in later simulations of Eennard-Jones fluids. 

Nichipor, H., Dashouk, E., Yermakov A computer simulation of the kinetics of high temperature radiation induced reduction of NO. Radiat. Phys. Chem. 54(3), 307-315 (1999)... 

Many of the telescopes used by astronomers are earth-based, located in observatories around the world. However, only radio waves, visible light, and some infrared radiation can penetrate our atmosphere to reach the earth s surface. Therefore, scientists have launched telescopes into space, where the instruments can collect other types of electromagnetic waves. Space probes are also able to gather information from distant parts of the solar system. In addition to telescopes, scientists construct mathematical models and computer simulations to form a scientific account of events in the universe. These models and simulations are built using evidence from many sources, including the information gathered through telescopes and space probes. 

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