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4 | <!-- Changed by: Katsuya Amako, 21-Sep-1998 --> |
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5 | <!-- Changed by: Dennis Wright, 27-Nov-2001 --> |
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6 | <!-- Proof read by: Joe Chuma, 30-Jun-1999 --> |
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7 | |
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8 | <BODY> |
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9 | <TABLE WIDTH="100%"><TR> |
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10 | <TD> |
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11 | |
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12 | |
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13 | <A HREF="index.html"> |
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14 | <IMG SRC="../../../../resources/html/IconsGIF/Contents.gif" ALT="Contents"></A> |
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15 | <A HREF="hit.html"> |
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16 | <IMG SRC="../../../../resources/html/IconsGIF/Previous.gif" ALT="Previous"></A> |
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17 | <A HREF="persistency.html"> |
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19 | </TD> |
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20 | <TD ALIGN="Right"> |
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21 | <FONT SIZE="-1" COLOR="#238E23"> |
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22 | <B>Geant4 User's Guide</B> |
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23 | <BR> |
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24 | <B>For Application Developers</B> |
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25 | <BR> |
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26 | <B>Detector Definition and Response</B> |
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27 | </FONT> |
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28 | </TD> |
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29 | </TR></TABLE> |
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30 | <BR><BR> |
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31 | |
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32 | <P ALIGN="Center"> |
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33 | <FONT SIZE="+3" COLOR="#238E23"> |
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34 | <B>4.5 Digitization</B> |
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35 | </FONT> |
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36 | <BR><BR> |
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37 | |
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38 | <HR ALIGN="Center" SIZE="7%"> |
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39 | <p> |
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40 | |
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41 | <a name="4.5.1"> |
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42 | <H2>4.5.1 Digi</H2></a> |
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43 | |
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44 | A hit is created by a sensitive detector when a step goes through |
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45 | it. Thus, the sensitive detector is associated to the corresponding |
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46 | <i>G4LogicalVolume</i> object(s). On the other hand, a digit is |
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47 | created using information of hits and/or other digits by a digitizer |
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48 | module. The digitizer module is not associated with any volume, and |
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49 | you have to implicitly invoke the <tt>Digitize()</tt> method of your |
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50 | concrete <i>G4VDigitizerModule</i> class. |
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51 | <p> |
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52 | Typical usages of digitizer module include: |
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53 | <ul> |
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54 | <li>simulate ADC and/or TDC |
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55 | <li>simulate readout scheme |
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56 | <li>generate raw data |
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57 | <li>simulate trigger logics |
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58 | <li>simulate pile up |
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59 | </ul> |
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60 | <p> |
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61 | |
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62 | <B><i>G4VDigi</i></B> |
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63 | <P> |
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64 | <i>G4VDigi</i> is an abstract base class which represents a digit. |
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65 | You have to inherit this base class and derive your own concrete |
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66 | digit class(es). The member data of your concrete digit class |
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67 | should be defined by yourself. <i>G4VDigi</i> has two virtual methods, |
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68 | <tt>Draw()</tt> and <tt>Print()</tt>. |
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69 | <p> |
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70 | |
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71 | <B><i>G4TDigiCollection</i></B> |
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72 | <P> |
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73 | <i>G4TDigiCollection</i> is a template class for digits collections, |
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74 | which is derived from the abstract base class <i>G4VDigiCollection</i>. |
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75 | <i>G4Event</i> has a <i>G4DCofThisEvent</i> object, which is a |
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76 | container class of collections of digits. The usages of <i>G4VDigi</i> |
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77 | and <i>G4TDigiCollection</i> are almost the same as <i>G4VHit</i> and |
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78 | <i>G4THitsCollection</i>, respectively, explained in the previous |
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79 | section. |
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80 | <p> |
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81 | |
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82 | <HR> |
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83 | <a name="4.5.2"> |
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84 | <H2>4.5.2 Digitizer module</H2></a> |
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85 | |
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86 | <B><i>G4VDigitizerModule</i></B> |
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87 | <P> |
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88 | <i>G4VDigitizerModule</i> is an abstract base class which represents |
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89 | a digitizer module. It has a pure virtual method, <tt>Digitize()</tt>. |
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90 | A concrete digitizer module must have an implementation of this |
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91 | virtual method. The Geant4 kernel classes do not have a ``built-in'' invocation to |
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92 | the <tt>Digitize()</tt> method. You have to implement your code to invoke |
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93 | this method of your digitizer module. |
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94 | <p> |
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95 | In the <tt>Digitize()</tt> method, you construct your <i>G4VDigi</i> |
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96 | concrete class objects and store them to your <i>G4TDigiCollection</i> |
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97 | concrete class object(s). Your collection(s) should be associated |
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98 | with the <i>G4DCofThisEvent</i> object. |
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99 | <p> |
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100 | |
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101 | <B><i>G4DigiManager</i></B> |
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102 | <P> |
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103 | <i>G4DigiManager</i> is the singleton manager class of the digitizer |
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104 | modules. All of your concrete digitizer modules should be registered |
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105 | to <i>G4DigiManager</i> with their unique names. |
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106 | <pre> |
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107 | G4DigiManager * fDM = G4DigiManager::GetDMpointer(); |
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108 | MyDigitizer * myDM = new MyDigitizer( "/myDet/myCal/myEMdigiMod" ); |
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109 | fDM->AddNewModule(myDM); |
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110 | </pre> |
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111 | Your concrete digitizer module can be accessed from your code using |
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112 | the unique module name. |
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113 | <pre> |
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114 | G4DigiManager * fDM = G4DigiManager::GetDMpointer(); |
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115 | MyDigitizer * myDM = fDM->FindDigitizerModule( "/myDet/myCal/myEMdigiMod" ); |
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116 | myDM->Digitize(); |
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117 | </pre> |
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118 | Also, <i>G4DigiManager</i> has a <i>Digitize()</i> method which takes |
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119 | the unique module name. |
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120 | <pre> |
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121 | G4DigiManager * fDM = G4DigiManager::GetDMpointer(); |
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122 | MyDigitizer * myDM = fDM->Digitize( "/myDet/myCal/myEMdigiMod" ); |
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123 | </pre> |
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124 | <p> |
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125 | |
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126 | <B>How to get hitsCollection and/or digiCollection</B> |
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127 | <P> |
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128 | <i>G4DigiManager</i> has the following methods to access to the |
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129 | hits or digi collections of the currently processing event |
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130 | or of previous events. |
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131 | <p> |
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132 | First, you have to get the collection ID number of the hits or digits |
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133 | collection. |
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134 | <pre> |
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135 | G4DigiManager * fDM = G4DigiManager::GetDMpointer(); |
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136 | G4int myHitsCollID = fDM->GetHitsCollectionID( "hits_collection_name" ); |
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137 | G4int myDigiCollID = fDM->GetDigiCollectionID( "digi_collection_name" ); |
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138 | </pre> |
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139 | Then, you can get the pointer to your concrete <i>G4THitsCollection</i> |
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140 | object or <i>G4TDigiCollection</i> object of the currently processing |
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141 | event. |
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142 | <pre> |
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143 | MyHitsCollection * HC = fDM->GetHitsCollection( myHitsCollID ); |
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144 | MyDigiCollection * DC = fDM->GetDigiCollection( myDigiCollID ); |
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145 | </pre> |
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146 | In case you want to access to the hits or digits collection of previous |
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147 | events, add the second argument. |
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148 | <pre> |
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149 | MyHitsCollection * HC = fDM->GetHitsCollection( myHitsCollID, n ); |
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150 | MyDigiCollection * DC = fDM->GetDigiCollection( myDigiCollID, n ); |
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151 | </pre> |
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152 | where, <tt>n</tt> indicates the hits or digits collection of the <tt>n</tt><sup>th</sup> |
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153 | previous event. |
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154 | <p> |
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155 | |
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156 | <BR><BR> |
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157 | <HR> |
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158 | <A HREF="../../../../Authors/html/subjectsToAuthors.html"> |
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159 | <I>About the authors</I></A> |
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160 | |
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