1 | <!-- ******************************************************** --> |
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2 | <!-- --> |
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3 | <!-- [History] --> |
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4 | <!-- Changed by: Katsuya Amako, 4-Aug-1998 --> |
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5 | <!-- Changed by: Dennis Wright, 28-Nov-2001 --> |
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6 | <!-- Proof read by: Joe Chuma, 15-Jun-1999 --> |
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7 | <!-- Converted to DocBook: Katsuya Amako, Aug-2006 --> |
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8 | <!-- --> |
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9 | <!-- ******************************************************** --> |
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10 | |
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11 | |
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12 | <!-- ******************* Section (Level#1) ****************** --> |
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13 | <sect1 id="sect.HowToSpecMate"> |
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14 | <title> |
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15 | How to Specify Materials in the Detector |
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16 | </title> |
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17 | |
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18 | <!-- ******************* Section (Level#2) ****************** --> |
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19 | <sect2 id="sect.HowToSpecMate.GeneCons"> |
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20 | <title> |
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21 | General Considerations |
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22 | </title> |
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23 | |
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24 | <para> |
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25 | In nature, general materials (chemical compounds, mixtures) are |
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26 | made of elements, and elements are made of isotopes. Therefore, |
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27 | these are the three main classes designed in Geant4. Each of these |
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28 | classes has a table as a static data member, which is for keeping |
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29 | track of the instances created of the respective classes. |
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30 | </para> |
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31 | |
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32 | <para> |
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33 | The <emphasis>G4Element</emphasis> class describes the properties of the |
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34 | atoms: |
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35 | <itemizedlist spacing="compact"> |
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36 | <listitem><para> |
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37 | atomic number, |
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38 | </para></listitem> |
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39 | <listitem><para> |
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40 | number of nucleons, |
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41 | </para></listitem> |
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42 | <listitem><para> |
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43 | atomic mass, |
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44 | </para></listitem> |
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45 | <listitem><para> |
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46 | shell energy, |
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47 | </para></listitem> |
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48 | <listitem><para> |
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49 | as well as quantities such as cross sections per atom, etc. |
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50 | </para></listitem> |
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51 | </itemizedlist> |
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52 | </para> |
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53 | |
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54 | <para> |
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55 | The <emphasis>G4Material</emphasis> class describes the macroscopic properties |
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56 | of matter: |
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57 | <itemizedlist spacing="compact"> |
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58 | <listitem><para> |
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59 | density, |
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60 | </para></listitem> |
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61 | <listitem><para> |
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62 | state, |
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63 | </para></listitem> |
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64 | <listitem><para> |
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65 | temperature, |
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66 | </para></listitem> |
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67 | <listitem><para> |
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68 | pressure, |
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69 | </para></listitem> |
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70 | <listitem><para> |
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71 | as well as macroscopic quantities like radiation length, mean |
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72 | free path, dE/dx, etc. |
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73 | </para></listitem> |
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74 | </itemizedlist> |
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75 | </para> |
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76 | |
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77 | <para> |
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78 | The <emphasis>G4Material</emphasis> class is the one which is visible to the |
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79 | rest of the toolkit, and is used by the tracking, the geometry, and |
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80 | the physics. It contains all the information relative to the |
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81 | eventual elements and isotopes of which it is made, at the same |
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82 | time hiding the implementation details. |
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83 | </para> |
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84 | |
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85 | </sect2> |
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86 | |
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87 | <!-- ******************* Section (Level#2) ****************** --> |
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88 | <sect2 id="sect.HowToSpecMate.DefSimpleMate"> |
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89 | <title> |
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90 | Define a Simple Material |
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91 | </title> |
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92 | |
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93 | <para> |
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94 | In the example below, liquid argon is created, by specifying its |
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95 | name, density, mass per mole, and atomic number. |
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96 | <example id="programlist_HowToSpecMate_1"> |
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97 | <title> |
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98 | Creating liquid argon. |
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99 | </title> |
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100 | <programlisting> |
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101 | G4double density = 1.390*g/cm3; |
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102 | G4double a = 39.95*g/mole; |
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103 | G4Material* lAr = new G4Material(name="liquidArgon", z=18., a, density); |
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104 | </programlisting> |
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105 | </example> |
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106 | </para> |
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107 | |
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108 | <para> |
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109 | The pointer to the material, <emphasis>lAr</emphasis>, will be used to specify |
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110 | the matter of which a given logical volume is made: |
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111 | <informalexample> |
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112 | <programlisting> |
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113 | G4LogicalVolume* myLbox = new G4LogicalVolume(aBox,lAr,"Lbox",0,0,0); |
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114 | </programlisting> |
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115 | </informalexample> |
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116 | </para> |
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117 | |
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118 | </sect2> |
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119 | |
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120 | <!-- ******************* Section (Level#2) ****************** --> |
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121 | <sect2 id="sect.HowToSpecMate.DefineMolecule"> |
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122 | <title> |
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123 | Define a Molecule |
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124 | </title> |
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125 | |
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126 | <para> |
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127 | In the example below, the water, <emphasis>H2O</emphasis>, is built from its |
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128 | components, by specifying the number of atoms in the molecule. |
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129 | <example id="programlist_HowToSpecMate_2"> |
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130 | <title> |
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131 | Creating water by defining its molecular components. |
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132 | </title> |
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133 | <programlisting> |
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134 | a = 1.01*g/mole; |
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135 | G4Element* elH = new G4Element(name="Hydrogen",symbol="H" , z= 1., a); |
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136 | |
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137 | a = 16.00*g/mole; |
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138 | G4Element* elO = new G4Element(name="Oxygen" ,symbol="O" , z= 8., a); |
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139 | |
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140 | density = 1.000*g/cm3; |
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141 | G4Material* H2O = new G4Material(name="Water",density,ncomponents=2); |
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142 | H2O->AddElement(elH, natoms=2); |
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143 | H2O->AddElement(elO, natoms=1); |
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144 | </programlisting> |
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145 | </example> |
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146 | </para> |
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147 | |
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148 | </sect2> |
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149 | |
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150 | <!-- ******************* Section (Level#2) ****************** --> |
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151 | <sect2 id="sect.HowToSpecMate.DefMixtureByFractionalMass"> |
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152 | <title> |
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153 | Define a Mixture by Fractional Mass |
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154 | </title> |
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155 | |
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156 | <para> |
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157 | In the example below, air is built from nitrogen and oxygen, by |
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158 | giving the fractional mass of each component. |
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159 | |
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160 | <example id="programlist_HowToSpecMate_3"> |
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161 | <title> |
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162 | Creating air by defining the fractional mass of its components. |
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163 | </title> |
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164 | <programlisting> |
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165 | a = 14.01*g/mole; |
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166 | G4Element* elN = new G4Element(name="Nitrogen",symbol="N" , z= 7., a); |
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167 | |
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168 | a = 16.00*g/mole; |
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169 | G4Element* elO = new G4Element(name="Oxygen" ,symbol="O" , z= 8., a); |
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170 | |
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171 | density = 1.290*mg/cm3; |
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172 | G4Material* Air = new G4Material(name="Air ",density,ncomponents=2); |
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173 | Air->AddElement(elN, fractionmass=70*perCent); |
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174 | Air->AddElement(elO, fractionmass=30*perCent); |
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175 | </programlisting> |
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176 | </example> |
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177 | </para> |
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178 | |
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179 | </sect2> |
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180 | |
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181 | |
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182 | <!-- ******************* Section (Level#2) ****************** --> |
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183 | <sect2 id="sect.HowToSpecMate.DefMateFromDatabase"> |
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184 | <title> |
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185 | Define a Material from the Geant4 Material Database |
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186 | </title> |
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187 | |
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188 | <para> |
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189 | In the example below, air and water are accessed via the Geant4 |
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190 | material database. |
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191 | <example id="programlist_HowToSpecMate_4"> |
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192 | <title> |
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193 | Defining air and water from the internal Geant4 database. |
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194 | </title> |
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195 | <programlisting> |
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196 | G4NistManager* man = G4NistManager::Instance(); |
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197 | |
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198 | G4Material* H2O = man->FindOrBuildMaterial("G4_WATER"); |
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199 | G4Material* Air = man->FindOrBuildMaterial("G4_AIR"); |
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200 | </programlisting> |
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201 | </example> |
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202 | </para> |
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203 | |
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204 | </sect2> |
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205 | |
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206 | <!-- ******************* Section (Level#2) ****************** --> |
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207 | <sect2 id="sect.HowToSpecMate.PrintMateInfo"> |
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208 | <title> |
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209 | Print Material Information |
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210 | </title> |
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211 | |
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212 | <para> |
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213 | <example id="programlist_HowToSpecMate_5"> |
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214 | <title> |
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215 | Printing information about materials. |
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216 | </title> |
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217 | <programlisting> |
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218 | G4cout << H2O; \\ print a given material |
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219 | G4cout << *(G4Material::GetMaterialTable()); \\ print the list of materials |
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220 | </programlisting> |
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221 | </example> |
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222 | |
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223 | In <literal>examples/novice/N03/N03DetectorConstruction.cc</literal>, you |
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224 | will find examples of all possible ways to build a material. |
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225 | </para> |
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226 | |
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227 | |
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228 | </sect2> |
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229 | </sect1> |
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