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| 8 | <!-- Changed by: Katsuya Amako, 14-Jul-1998 --> |
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| 9 | <!-- Proof read by: Joe Chuma, 29-Jun-1999 --> |
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| 10 | |
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| 11 | <TABLE WIDTH="100%" > |
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| 12 | <TR> |
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| 13 | <TD> |
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| 14 | </A> |
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| 15 | <A HREF="index.html"> |
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| 16 | <IMG SRC="../../../../resources/html/IconsGIF/Contents.gif" ALT="Contents" HEIGHT=16 WIDTH=59></A> |
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| 17 | <A HREF="geometry.html"> |
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| 18 | <IMG SRC="../../../../resources/html/IconsGIF/Previous.gif" ALT="Previous" HEIGHT=16 WIDTH=59></A> |
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| 19 | <A HREF="electroMagneticField.html"> |
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| 21 | </TD> |
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| 22 | |
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| 23 | <TD ALIGN="Right"><FONT COLOR="#238E23"><FONT SIZE=-1> |
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| 24 | <B>Geant4 User's Guide</B> <BR> |
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| 25 | <B>For Application Developers</B> <BR> |
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| 26 | <B>Detector Definition and Response</B> </FONT></FONT> </TD> |
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| 27 | </TR> |
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| 28 | </TABLE> |
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| 29 | <P><BR> |
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| 30 | |
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| 31 | <CENTER><FONT COLOR="#238E23"><FONT SIZE=+3> |
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| 32 | <B>4.2 Material</B> </FONT></FONT> |
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| 33 | </CENTER> |
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| 34 | <BR> |
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| 35 | <BR> |
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| 36 | |
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| 37 | <HR ALIGN="Center" SIZE="7%"> |
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| 38 | <p> |
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| 39 | |
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| 40 | <a name="4.2.1"> |
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| 41 | <H2>4.2.1 General considerations</H2></a> |
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| 42 | |
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| 43 | In nature, materials (chemical compounds, mixtures) are made of elements, |
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| 44 | and elements are made of isotopes. Geant4 has three main classes |
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| 45 | designed to reflect this organization. Each of these classes has a table, |
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| 46 | which is a static data member, used to keep track of the instances of the |
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| 47 | respective classes created. |
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| 48 | <p> |
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| 49 | <dl><dl> |
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| 50 | <dt><i>G4Isotope</i> |
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| 51 | <dd>This class describes the properties of atoms: atomic number, number of |
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| 52 | nucleons, mass per mole, etc. |
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| 53 | </p> |
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| 54 | <p> |
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| 55 | <dt><i>G4Element</i> |
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| 56 | <dd>This class describes the properties of elements: effective atomic number, |
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| 57 | effective number of nucleons, effective mass per mole, number of isotopes, |
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| 58 | shell energy, and quantities like cross section per atom, etc. |
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| 59 | </p> |
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| 60 | <p> |
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| 61 | <dt><i>G4Material</i> |
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| 62 | <dd>This class describes the macroscopic properties of matter: |
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| 63 | density, state, temperature, pressure, and macroscopic quantities like |
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| 64 | radiation length, mean free path, dE/dx, etc. |
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| 65 | </p> |
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| 66 | </dl></dl> |
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| 67 | <p> |
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| 68 | Only the <i>G4Material</i> class is visible to the rest of the toolkit and |
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| 69 | used by the tracking, the geometry and the physics. It contains all the |
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| 70 | information relevant to its constituent elements and isotopes, while at |
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| 71 | the same time hiding their implementation details. |
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| 72 | </p> |
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| 73 | |
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| 74 | <hr> |
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| 75 | <a name="4.2.2"> |
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| 76 | <h2>4.2.2 Introduction to the Classes</h2></a> |
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| 77 | |
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| 78 | <b><i>G4Isotope</i></b> |
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| 79 | <p> |
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| 80 | A <i>G4Isotope</i> object has a name, atomic number, number of nucleons, mass |
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| 81 | per mole, and an index in the table. The constructor automatically stores |
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| 82 | "this" isotope in the isotopes table, which will assign it an index number. |
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| 83 | </p> |
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| 84 | <br> |
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| 85 | |
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| 86 | <b><i>G4Element</i></b> |
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| 87 | <p> |
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| 88 | A <i>G4Element</i> object has a name, symbol, effective atomic number, |
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| 89 | effective number of nucleons, effective mass of a mole, an index in the |
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| 90 | elements table, the number of isotopes, a vector of pointers to such isotopes, |
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| 91 | and a vector of relative abundances referring to such isotopes (where relative |
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| 92 | abundance means the number of atoms per volume). In addition, the class has |
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| 93 | methods to add, one by one, the isotopes which are to form the element. |
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| 94 | </p> |
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| 95 | <p> |
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| 96 | A <i>G4Element</i> object can be constructed by directly providing the |
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| 97 | effective atomic number, effective number of nucleons, and effective mass of |
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| 98 | a mole, if the user explicitly wants to do so. Alternatively, a |
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| 99 | <i>G4Element</i> object can be constructed by declaring the number of |
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| 100 | isotopes of which it will be composed. The constructor will "new" a vector |
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| 101 | of pointers to <i>G4Isotopes</i> and a vector of doubles to store their |
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| 102 | relative abundances. Finally, the method to add an isotope must be invoked |
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| 103 | for each of the desired (pre-existing) isotope objects, providing their |
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| 104 | addresses and relative abundances. At the last isotope entry, the system will |
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| 105 | automatically compute the effective atomic number, effective number of |
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| 106 | nucleons and effective mass of a mole, and will store "this" element in the |
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| 107 | elements table. |
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| 108 | </p> |
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| 109 | <p> |
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| 110 | A few quantities, with physical meaning or not, which are constant in |
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| 111 | a given element, are computed and stored here as "derived data members". |
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| 112 | </p> |
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| 113 | <p> |
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| 114 | Using the internal Geant4 database, a G4Element can be accessed by atomic |
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| 115 | number or by atomic symbol ("Al", "Fe", "Pb"...). In that case |
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| 116 | G4Element will be found from the list of existing elements or |
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| 117 | will be constructed using data from the Geant4 database, which is derived |
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| 118 | from the NIST database of elements and isotope compositions |
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| 119 | (http://physics.nist.gov/PhysRefData/Compositions/index.html). Thus, |
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| 120 | the natural isotope composition can be built by default. The same element |
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| 121 | can be created as using the NIST database with natural composition of isotopes |
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| 122 | and from scratch in user code with user defined isotope composition. |
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| 123 | </p> |
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| 124 | <br> |
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| 125 | |
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| 126 | <b><i>G4Material</i></b> |
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| 127 | <p> |
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| 128 | A <i>G4Material</i> object has a name, density, physical state, temperature |
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| 129 | and pressure (by default the standard conditions), the number of elements and |
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| 130 | a vector of pointers to such elements, a vector of the fraction of mass for |
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| 131 | each element, a vector of the atoms (or molecules) numbers of each element, |
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| 132 | and an index in the materials table. In addition, the class has methods to |
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| 133 | add, one by one, the elements which will comprise the material. |
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| 134 | </p> |
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| 135 | <p> |
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| 136 | A <i>G4Material</i> object can be constructed by directly providing the |
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| 137 | resulting effective numbers, if the user explicitly wants to do so (an |
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| 138 | underlying element will be created with these numbers). Alternatively, a |
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| 139 | <i>G4Material</i> object can be constructed by declaring the number of |
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| 140 | elements of which it will be composed. The constructor will "new" a vector |
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| 141 | of pointers to <i>G4Element</i> and a vector of doubles to store their |
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| 142 | fraction of mass. Finally, the method to add an element must be invoked |
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| 143 | for each of the desired (pre-existing) element objects, providing their |
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| 144 | addresses and mass fractions. At the last element entry, the system will |
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| 145 | automatically compute the vector of the number of atoms of each element per |
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| 146 | volume, the total number of electrons per volume, and will store "this" |
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| 147 | material in the materials table. In the same way, a material can be |
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| 148 | constructed as a mixture of other materials and elements. |
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| 149 | </p> |
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| 150 | <p> |
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| 151 | It should be noted that if the user provides the number of atoms (or |
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| 152 | molecules) for each element comprising the chemical compound, the system |
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| 153 | automatically computes the mass fraction. A few quantities, with physical |
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| 154 | meaning or not, which are constant in a given material, are computed and |
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| 155 | stored here as "derived data members". |
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| 156 | </p> |
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| 157 | <p> |
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| 158 | Some materials are included in the internal Geant4 database, which |
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| 159 | were derived from the NIST database of material properties |
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| 160 | (http://physics.nist.gov/PhysRefData/Star/Text/method.html). |
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| 161 | Additionally a number of materials frequently used in HEP is included |
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| 162 | in the database. |
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| 163 | Materials are interrogated or constructed by their <a href="materialNames.html"> |
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| 164 | <i>names</a></i>. There are UI |
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| 165 | commands for the material category, which provide an interactive |
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| 166 | access to the database. If material is created using the NIST database it will |
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| 167 | consist of elements with natural composition of isotopes. |
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| 168 | </p> |
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| 169 | <br> |
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| 170 | |
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| 171 | <b>Final Considerations</b> |
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| 172 | |
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| 173 | The classes will automatically decide if the total of the mass fractions |
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| 174 | is correct, and perform the necessary checks. The main reason why a fixed |
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| 175 | index is kept as a data member is that many cross section and energy tables |
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| 176 | will be built in the physics processes "by rows of materials (or elements, |
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| 177 | or even isotopes)". The tracking gives the physics process the address of |
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| 178 | a material object (the material of the current volume). |
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| 179 | If the material has an index according to which the cross section table |
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| 180 | has been built, then direct access is available when a number in such a |
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| 181 | table must be accessed. We get directly to the correct row, and the energy |
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| 182 | of the particle will tell us the column. Without such an index, every access |
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| 183 | to the cross section or energy tables would imply a search to get to the |
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| 184 | correct material's row. More details will be given in the section on |
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| 185 | processes. |
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| 186 | </p> |
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| 187 | <br> |
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| 188 | |
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| 189 | <hr> |
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| 190 | <a name="4.2.3"> |
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| 191 | <h2>4.2.3 Recipes for Building Elements and Materials</h2></a> |
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| 192 | |
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| 193 | Source listing 4.2.1 illustrates the different ways to define materials. |
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| 194 | <p> |
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| 195 | <center> |
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| 196 | <table border=2 cellpadding=10> |
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| 197 | <tr> |
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| 198 | <td> |
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| 199 | <PRE> |
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| 200 | #include "G4Isotope.hh" |
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| 201 | #include "G4Element.hh" |
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| 202 | #include "G4Material.hh" |
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| 203 | #include "G4UnitsTable.hh" |
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| 204 | |
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| 205 | int main() { |
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| 206 | |
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| 207 | G4String name, symbol; // a=mass of a mole; |
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| 208 | G4double a, z, density; // z=mean number of protons; |
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| 209 | G4int iz, n; //iz=nb of protons in an isotope; |
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| 210 | // n=nb of nucleons in an isotope; |
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| 211 | |
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| 212 | G4int ncomponents, natoms; |
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| 213 | G4double abundance, fractionmass; |
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| 214 | G4double temperature, pressure; |
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| 215 | |
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| 216 | G4UnitDefinition::BuildUnitsTable(); |
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| 217 | |
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| 218 | // |
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| 219 | // define Elements |
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| 220 | // |
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| 221 | |
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| 222 | a = 1.01*g/mole; |
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| 223 | G4Element* elH = new G4Element(name="Hydrogen",symbol="H" , z= 1., a); |
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| 224 | |
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| 225 | a = 12.01*g/mole; |
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| 226 | G4Element* elC = new G4Element(name="Carbon" ,symbol="C" , z= 6., a); |
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| 227 | |
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| 228 | a = 14.01*g/mole; |
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| 229 | G4Element* elN = new G4Element(name="Nitrogen",symbol="N" , z= 7., a); |
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| 230 | |
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| 231 | a = 16.00*g/mole; |
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| 232 | G4Element* elO = new G4Element(name="Oxygen" ,symbol="O" , z= 8., a); |
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| 233 | |
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| 234 | a = 28.09*g/mole; |
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| 235 | G4Element* elSi = new G4Element(name="Silicon", symbol="Si", z=14., a); |
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| 236 | |
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| 237 | a = 55.85*g/mole; |
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| 238 | G4Element* elFe = new G4Element(name="Iron" ,symbol="Fe", z=26., a); |
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| 239 | |
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| 240 | a = 183.84*g/mole; |
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| 241 | G4Element* elW = new G4Element(name="Tungsten" ,symbol="W", z=74., a); |
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| 242 | |
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| 243 | a = 207.20*g/mole; |
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| 244 | G4Element* elPb = new G4Element(name="Lead" ,symbol="Pb", z=82., a); |
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| 245 | |
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| 246 | // |
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| 247 | // define an Element from isotopes, by relative abundance |
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| 248 | // |
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| 249 | |
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| 250 | G4Isotope* U5 = new G4Isotope(name="U235", iz=92, n=235, a=235.01*g/mole); |
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| 251 | G4Isotope* U8 = new G4Isotope(name="U238", iz=92, n=238, a=238.03*g/mole); |
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| 252 | |
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| 253 | G4Element* elU = new G4Element(name="enriched Uranium", symbol="U", ncomponents=2); |
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| 254 | elU->AddIsotope(U5, abundance= 90.*perCent); |
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| 255 | elU->AddIsotope(U8, abundance= 10.*perCent); |
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| 256 | |
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| 257 | |
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| 258 | cout << *(G4Isotope::GetIsotopeTable()) << endl; |
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| 259 | |
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| 260 | cout << *(G4Element::GetElementTable()) << endl; |
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| 261 | |
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| 262 | // |
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| 263 | // define simple materials |
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| 264 | // |
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| 265 | |
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| 266 | density = 2.700*g/cm3; |
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| 267 | a = 26.98*g/mole; |
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| 268 | G4Material* Al = new G4Material(name="Aluminum", z=13., a, density); |
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| 269 | |
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| 270 | density = 1.390*g/cm3; |
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| 271 | a = 39.95*g/mole; |
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| 272 | G4Material* lAr = new G4Material(name="liquidArgon", z=18., a, density); |
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| 273 | |
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| 274 | density = 8.960*g/cm3; |
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| 275 | a = 63.55*g/mole; |
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| 276 | G4Material* Cu = new G4Material(name="Copper" , z=29., a, density); |
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| 277 | |
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| 278 | // |
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| 279 | // define a material from elements. case 1: chemical molecule |
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| 280 | // |
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| 281 | |
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| 282 | density = 1.000*g/cm3; |
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| 283 | G4Material* H2O = new G4Material(name="Water", density, ncomponents=2); |
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| 284 | H2O->AddElement(elH, natoms=2); |
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| 285 | H2O->AddElement(elO, natoms=1); |
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| 286 | |
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| 287 | density = 1.032*g/cm3; |
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| 288 | G4Material* Sci = new G4Material(name="Scintillator", density, ncomponents=2); |
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| 289 | Sci->AddElement(elC, natoms=9); |
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| 290 | Sci->AddElement(elH, natoms=10); |
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| 291 | |
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| 292 | density = 2.200*g/cm3; |
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| 293 | G4Material* SiO2 = new G4Material(name="quartz", density, ncomponents=2); |
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| 294 | SiO2->AddElement(elSi, natoms=1); |
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| 295 | SiO2->AddElement(elO , natoms=2); |
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| 296 | |
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| 297 | density = 8.280*g/cm3; |
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| 298 | G4Material* PbWO4= new G4Material(name="PbWO4", density, ncomponents=3); |
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| 299 | PbWO4->AddElement(elO , natoms=4); |
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| 300 | PbWO4->AddElement(elW , natoms=1); |
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| 301 | PbWO4->AddElement(elPb, natoms=1); |
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| 302 | |
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| 303 | // |
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| 304 | // define a material from elements. case 2: mixture by fractional mass |
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| 305 | // |
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| 306 | |
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| 307 | density = 1.290*mg/cm3; |
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| 308 | G4Material* Air = new G4Material(name="Air " , density, ncomponents=2); |
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| 309 | Air->AddElement(elN, fractionmass=0.7); |
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| 310 | Air->AddElement(elO, fractionmass=0.3); |
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| 311 | |
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| 312 | // |
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| 313 | // define a material from elements and/or others materials (mixture of mixtures) |
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| 314 | // |
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| 315 | |
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| 316 | density = 0.200*g/cm3; |
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| 317 | G4Material* Aerog = new G4Material(name="Aerogel", density, ncomponents=3); |
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| 318 | Aerog->AddMaterial(SiO2, fractionmass=62.5*perCent); |
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| 319 | Aerog->AddMaterial(H2O , fractionmass=37.4*perCent); |
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| 320 | Aerog->AddElement (elC , fractionmass= 0.1*perCent); |
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| 321 | |
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| 322 | // |
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| 323 | // examples of gas in non STP conditions |
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| 324 | // |
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| 325 | |
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| 326 | density = 27.*mg/cm3; |
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| 327 | pressure = 50.*atmosphere; |
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| 328 | temperature = 325.*kelvin; |
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| 329 | G4Material* CO2 = new G4Material(name="Carbonic gas", density, ncomponents=2, |
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| 330 | kStateGas,temperature,pressure); |
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| 331 | CO2->AddElement(elC, natoms=1); |
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| 332 | CO2->AddElement(elO, natoms=2); |
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| 333 | |
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| 334 | density = 0.3*mg/cm3; |
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| 335 | pressure = 2.*atmosphere; |
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| 336 | temperature = 500.*kelvin; |
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| 337 | G4Material* steam = new G4Material(name="Water steam ", density, ncomponents=1, |
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| 338 | kStateGas,temperature,pressure); |
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| 339 | steam->AddMaterial(H2O, fractionmass=1.); |
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| 340 | |
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| 341 | // |
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| 342 | // What about vacuum ? Vacuum is an ordinary gas with very low density |
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| 343 | // |
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| 344 | |
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| 345 | density = universe_mean_density; //from PhysicalConstants.h |
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| 346 | pressure = 1.e-19*pascal; |
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| 347 | temperature = 0.1*kelvin; |
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| 348 | new G4Material(name="Galactic", z=1., a=1.01*g/mole, density, |
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| 349 | kStateGas,temperature,pressure); |
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| 350 | |
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| 351 | density = 1.e-5*g/cm3; |
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| 352 | pressure = 2.e-2*bar; |
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| 353 | temperature = STP_Temperature; //from PhysicalConstants.h |
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| 354 | G4Material* beam = new G4Material(name="Beam ", density, ncomponents=1, |
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| 355 | kStateGas,temperature,pressure); |
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| 356 | beam->AddMaterial(Air, fractionmass=1.); |
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| 357 | |
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| 358 | // |
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| 359 | // print the table of materials |
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| 360 | // |
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| 361 | |
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| 362 | G4cout << *(G4Material::GetMaterialTable()) << endl; |
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| 363 | |
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| 364 | return EXIT_SUCCESS; |
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| 365 | } |
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| 366 | </PRE> |
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| 367 | </td> |
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| 368 | </tr> |
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| 369 | <tr> |
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| 370 | <td align=center> |
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| 371 | Source listing 4.2.1<BR> |
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| 372 | A program which illustrates the different ways to define materials. |
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| 373 | </td> |
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| 374 | </tr> |
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| 375 | </table></center> |
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| 376 | <p> |
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| 377 | As can be seen in the later examples, a material has a state: solid (the |
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| 378 | default), liquid, or gas. The constructor checks the density and |
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| 379 | automatically sets the state to gas below a given threshold (10 mg/cm3). |
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| 380 | </p> |
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| 381 | <p> |
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| 382 | In the case of a gas, one may specify the temperature and pressure. The |
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| 383 | defaults are STP conditions defined in <tt>PhysicalConstants.hh</tt>. |
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| 384 | </p> |
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| 385 | <p> |
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| 386 | An element must have the number of nucleons >= number of protons >= 1. |
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| 387 | </p> |
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| 388 | <p> |
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| 389 | A material must have non-zero values of density, temperature and pressure. |
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| 390 | </p> |
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| 391 | <p> |
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| 392 | Materials can also be defined using the internal Geant4 database. |
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| 393 | Source listing 4.2.2 illustrates how to do this for the same materials |
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| 394 | used in 4.2.1. There are also UI commands which allow the database to |
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| 395 | be accessed. <a href="materialNames.html"> |
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| 396 | <i>The list of currently available material names</a></i> is extended permanently. |
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| 397 | </p> |
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| 398 | <p> |
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| 399 | <center> |
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| 400 | <table border=2 cellpadding=10> |
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| 401 | <tr> |
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| 402 | <td> |
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| 403 | <PRE> |
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| 404 | #include "globals.hh" |
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| 405 | #include "G4Material.hh" |
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| 406 | #include "G4NistManager.hh" |
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| 407 | |
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| 408 | int main() { |
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| 409 | |
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| 410 | G4NistManager* man = G4NistManager::Instance(); |
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| 411 | man->SetVerbose(1); |
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| 412 | |
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| 413 | // |
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| 414 | // define elements |
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| 415 | // |
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| 416 | |
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| 417 | G4Element* C = man->FindOrBuildElement("C"); |
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| 418 | G4Element* Pb = man->FindOrBuildMaterial("Pb"); |
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| 419 | |
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| 420 | // |
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| 421 | // define pure NIST materials |
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| 422 | // |
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| 423 | |
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| 424 | G4Material* Al = man->FindOrBuildMaterial("G4_Al"); |
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| 425 | G4Material* Cu = man->FindOrBuildMaterial("G4_Cu"); |
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| 426 | |
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| 427 | // |
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| 428 | // define NIST materials |
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| 429 | // |
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| 430 | |
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| 431 | G4Material* H2O = man->FindOrBuildMaterial("G4_WATER"); |
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| 432 | G4Material* Sci = man->FindOrBuildMaterial("G4_PLASTIC_SC_VINYLTOLUENE"); |
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| 433 | G4Material* SiO2 = man->FindOrBuildMaterial("G4_SILICON_DIOXIDE"); |
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| 434 | G4Material* Air = man->FindOrBuildMaterial("G4_AIR"); |
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| 435 | |
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| 436 | // |
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| 437 | // HEP materials |
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| 438 | // |
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| 439 | |
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| 440 | G4Material* PbWO4 = man->FindOrBuildMaterial("G4_PbWO4"); |
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| 441 | G4Material* lAr = man->FindOrBuildMaterial("G4_lAr"); |
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| 442 | G4Material* vac = man->FindOrBuildMaterial("G4_Galactic"); |
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| 443 | |
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| 444 | // |
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| 445 | // define gas material at non STP conditions (T = 120K, P=0.5atm) |
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| 446 | // |
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| 447 | |
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| 448 | G4Material* coldAr = man->ConstructNewGasdMaterial("ColdAr","G4_Ar",120.*kelvin,0.5*atmosphere); |
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| 449 | |
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| 450 | // |
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| 451 | // print the table of materials |
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| 452 | // |
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| 453 | |
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| 454 | G4cout << *(G4Material::GetMaterialTable()) << endl; |
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| 455 | |
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| 456 | return EXIT_SUCCESS; |
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| 457 | } |
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| 458 | </PRE> |
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| 459 | </td> |
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| 460 | </tr> |
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| 461 | <tr> |
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| 462 | <td align=center> |
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| 463 | Source listing 4.2.2<BR> |
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| 464 | A program which shows how to define materials from the internal database. |
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| 465 | </td> |
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| 466 | </tr> |
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| 467 | </table></center> |
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| 468 | |
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| 469 | <hr> |
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| 470 | <a name="4.2.4"> |
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| 471 | <h2>4.2.4 The Tables</h2></a> |
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| 472 | |
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| 473 | <b>Print a constituent</b> |
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| 474 | <p> |
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| 475 | The following shows how to print a constituent: |
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| 476 | |
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| 477 | <PRE> |
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| 478 | G4cout << elU << endl; |
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| 479 | G4cout << Air << endl; |
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| 480 | </PRE> |
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| 481 | <p> |
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| 482 | <b>Print the table of materials</b> |
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| 483 | <p> |
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| 484 | The following shows how to print the table of materials: |
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| 485 | |
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| 486 | <PRE> |
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| 487 | G4cout << *(G4Material::GetMaterialTable()) << endl; |
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| 488 | </PRE> |
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| 489 | <br> |
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| 490 | <br> |
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| 491 | |
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| 492 | <hr><a href="../../../../Authors/html/subjectsToAuthors.html"> |
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| 493 | <i>About the authors</a></i> |
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| 494 | </p> |
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| 495 | |
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| 496 | </BODY> |
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| 497 | </HTML> |
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