1 | // |
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2 | // ******************************************************************** |
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3 | // * License and Disclaimer * |
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4 | // * * |
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5 | // * The Geant4 software is copyright of the Copyright Holders of * |
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6 | // * the Geant4 Collaboration. It is provided under the terms and * |
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7 | // * conditions of the Geant4 Software License, included in the file * |
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8 | // * LICENSE and available at http://cern.ch/geant4/license . These * |
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9 | // * include a list of copyright holders. * |
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10 | // * * |
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11 | // * Neither the authors of this software system, nor their employing * |
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12 | // * institutes,nor the agencies providing financial support for this * |
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13 | // * work make any representation or warranty, express or implied, * |
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14 | // * regarding this software system or assume any liability for its * |
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15 | // * use. Please see the license in the file LICENSE and URL above * |
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16 | // * for the full disclaimer and the limitation of liability. * |
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17 | // * * |
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18 | // * This code implementation is the result of the scientific and * |
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19 | // * technical work of the GEANT4 collaboration. * |
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20 | // * By using, copying, modifying or distributing the software (or * |
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21 | // * any work based on the software) you agree to acknowledge its * |
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22 | // * use in resulting scientific publications, and indicate your * |
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23 | // * acceptance of all terms of the Geant4 Software license. * |
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24 | // ******************************************************************** |
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25 | // |
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26 | // |
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27 | // This software was developed by Lawrence Livermore National Laboratory. |
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28 | // |
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29 | // Redistribution and use in source and binary forms, with or without |
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30 | // modification, are permitted provided that the following conditions are met: |
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31 | // |
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32 | // 1. Redistributions of source code must retain the above copyright notice, |
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33 | // this list of conditions and the following disclaimer. |
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34 | // 2. Redistributions in binary form must reproduce the above copyright notice, |
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35 | // this list of conditions and the following disclaimer in the documentation |
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36 | // and/or other materials provided with the distribution. |
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37 | // 3. The name of the author may not be used to endorse or promote products |
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38 | // derived from this software without specific prior written permission. |
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39 | // |
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40 | // THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED |
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41 | // WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF |
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42 | // MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO |
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43 | // EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
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44 | // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, |
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45 | // PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; |
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46 | // OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, |
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47 | // WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR |
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48 | // OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF |
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49 | // ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
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50 | // |
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51 | // Copyright (c) 2006 The Regents of the University of California. |
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52 | // All rights reserved. |
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53 | // UCRL-CODE-224807 |
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54 | // |
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55 | // |
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56 | // $Id: G4SmpTerrell.cc,v 1.2 2007/06/01 13:46:53 gcosmo Exp $ |
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57 | // |
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58 | |
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59 | #include <cmath> |
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60 | #include "G4fissionEvent.hh" |
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61 | |
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62 | #define TWOPI 6.283185307 |
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63 | #define SQRT2 1.414213562 |
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64 | #define BSHIFT -0.43287 |
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65 | #define WIDTH 1.079 |
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66 | |
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67 | G4double G4fissionEvent::G4SmpTerrell(G4double nubar) { |
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68 | /* |
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69 | Description |
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70 | Sample Fission Number from Terrell's modified Gaussian distribution |
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71 | |
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72 | method uses Red Cullen's algoritm UCRL-TR-222526 |
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73 | */ |
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74 | |
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75 | /* |
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76 | Input |
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77 | nubar - average number of neutrons per fission |
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78 | Output |
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79 | G4SmpTerrell - sampled multiplicity |
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80 | |
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81 | */ |
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82 | |
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83 | G4double width; |
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84 | G4double temp1, temp2, expo, cshift; |
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85 | G4double rw, theta, sampleg; |
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86 | |
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87 | |
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88 | if (nubar < WIDTH) G4fissionerr(6, "SmpTerrell", "fission nubar out of range"); |
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89 | |
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90 | width = SQRT2 * WIDTH; |
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91 | temp1 = nubar + 0.5; |
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92 | temp2 = temp1/width; |
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93 | temp2 *= temp2; |
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94 | expo = std::exp(-temp2); |
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95 | cshift = temp1 + BSHIFT * WIDTH * expo/(1. - expo); |
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96 | |
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97 | do { |
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98 | rw = std::sqrt(-std::log(fisslibrng())); |
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99 | theta = TWOPI * fisslibrng(); |
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100 | sampleg = width * rw * std::cos(theta) + cshift; |
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101 | } while (sampleg < 0.0); |
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102 | |
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103 | return std::floor(sampleg); |
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104 | } |
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