| 1 | <html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>4.5. Digitization</title><link rel="stylesheet" href="../xml/XSLCustomizationLayer/G4HTMLStylesheet.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.71.1"><link rel="start" href="index.html" title="Geant4 User's Guide for Application Developers"><link rel="up" href="ch04.html" title="Chapter 4. Detector Definition and Response"><link rel="prev" href="ch04s04.html" title="4.4. Hits"><link rel="next" href="ch04s06.html" title="4.6. Object Persistency"><script language="JavaScript">
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| 8 | </script></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">4.5.
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| 9 | Digitization
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| 10 | </th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ch04s04.html"><img src="AllResources/IconsGIF/prev.gif" alt="Prev"></a> </td><th width="60%" align="center">Chapter 4.
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| 11 | Detector Definition and Response
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| 12 | </th><td width="20%" align="right"> <a accesskey="n" href="ch04s06.html"><img src="AllResources/IconsGIF/next.gif" alt="Next"></a></td></tr></table><hr></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="sect.Digi"></a>4.5.
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| 13 | Digitization
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| 14 | </h2></div></div></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="sect.Digi.Digi"></a>4.5.1.
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| 15 | Digi
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| 16 | </h3></div></div></div><p>
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| 17 | A hit is created by a sensitive detector when a step goes through
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| 18 | it. Thus, the sensitive detector is associated to the corresponding
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| 19 | <span class="emphasis"><em>G4LogicalVolume</em></span> object(s). On the other hand, a digit is
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| 20 | created using information of hits and/or other digits by a
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| 21 | digitizer module. The digitizer module is not associated with any
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| 22 | volume, and you have to implicitly invoke the <code class="literal">Digitize()</code>
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| 23 | method of your concrete <span class="emphasis"><em>G4VDigitizerModule</em></span> class.
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| 24 | </p><p>
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| 25 | Typical usages of digitizer module include:
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| 26 |
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| 27 | </p><div class="itemizedlist"><ul type="disc" compact><li><p>
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| 28 | simulate ADC and/or TDC
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| 29 | </p></li><li><p>
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| 30 | simulate readout scheme
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| 31 | </p></li><li><p>
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| 32 | generate raw data
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| 33 | </p></li><li><p>
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| 34 | simulate trigger logics
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| 35 | </p></li><li><p>
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| 36 | simulate pile up
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| 37 | </p></li></ul></div><p>
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| 38 | </p><h5><a name="id431887"></a>
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| 39 | G4VDigi
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| 40 | </h5><p>
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| 41 | <span class="emphasis"><em>G4VDigi</em></span> is an abstract base class which represents a
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| 42 | digit. You have to inherit this base class and derive your own
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| 43 | concrete digit class(es). The member data of your concrete digit
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| 44 | class should be defined by yourself. <span class="emphasis"><em>G4VDigi</em></span> has two virtual
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| 45 | methods, <code class="literal">Draw()</code> and <code class="literal">Print()</code>.
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| 46 | </p><h5><a name="id431920"></a>
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| 47 | G4TDigiCollection
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| 48 | </h5><p>
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| 49 | <span class="emphasis"><em>G4TDigiCollection</em></span> is a template class for digits
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| 50 | collections, which is derived from the abstract base class
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| 51 | <span class="emphasis"><em>G4VDigiCollection</em></span>. <span class="emphasis"><em>G4Event</em></span> has a
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| 52 | <span class="emphasis"><em>G4DCofThisEvent</em></span> object, which is a container class of
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| 53 | collections of digits. The usages of <span class="emphasis"><em>G4VDigi</em></span> and
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| 54 | <span class="emphasis"><em>G4TDigiCollection</em></span> are almost the same as <span class="emphasis"><em>G4VHit</em></span> and
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| 55 | <span class="emphasis"><em>G4THitsCollection</em></span>, respectively, explained in the previous
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| 56 | section.
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| 57 | </p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="sect.Digi.DigMod"></a>4.5.2.
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| 58 | Digitizer module
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| 59 | </h3></div></div></div><h5><a name="id431976"></a>
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| 60 | G4VDigitizerModule
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| 61 | </h5><p>
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| 62 | <span class="emphasis"><em>G4VDigitizerModule</em></span> is an abstract base class which
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| 63 | represents a digitizer module. It has a pure virtual method,
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| 64 | <code class="literal">Digitize()</code>. A concrete digitizer module must have an
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| 65 | implementation of this virtual method. The Geant4 kernel classes do
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| 66 | not have a ``built-in'' invocation to the <code class="literal">Digitize()</code>
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| 67 | method. You have to implement your code to invoke this method of
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| 68 | your digitizer module.
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| 69 | </p><p>
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| 70 | In the <code class="literal">Digitize()</code> method, you construct your
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| 71 | <span class="emphasis"><em>G4VDigi</em></span> concrete class objects and store them to your
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| 72 | <span class="emphasis"><em>G4TDigiCollection</em></span> concrete class object(s). Your
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| 73 | collection(s) should be associated with the <span class="emphasis"><em>G4DCofThisEvent</em></span>
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| 74 | object.
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| 75 | </p><h5><a name="id432028"></a>
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| 76 | G4DigiManager
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| 77 | </h5><p>
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| 78 | <span class="emphasis"><em>G4DigiManager</em></span> is the singleton manager class of the
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| 79 | digitizer modules. All of your concrete digitizer modules should be
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| 80 | registered to <span class="emphasis"><em>G4DigiManager</em></span> with their unique names.
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| 81 |
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| 82 | </p><div class="informalexample"><pre class="programlisting">
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| 83 | G4DigiManager * fDM = G4DigiManager::GetDMpointer();
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| 84 | MyDigitizer * myDM = new MyDigitizer( "/myDet/myCal/myEMdigiMod" );
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| 85 | fDM->AddNewModule(myDM);
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| 86 | </pre></div><p>
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| 87 | </p><p>
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| 88 | Your concrete digitizer module can be accessed from your code using
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| 89 | the unique module name.
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| 90 |
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| 91 | </p><div class="informalexample"><pre class="programlisting">
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| 92 | G4DigiManager * fDM = G4DigiManager::GetDMpointer();
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| 93 | MyDigitizer * myDM = fDM->FindDigitizerModule( "/myDet/myCal/myEMdigiMod" );
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| 94 | myDM->Digitize();
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| 95 | </pre></div><p>
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| 96 | </p><p>
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| 97 | Also, <span class="emphasis"><em>G4DigiManager</em></span> has a <span class="emphasis"><em>Digitize()</em></span>
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| 98 | method which takes the unique module name.
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| 99 |
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| 100 | </p><div class="informalexample"><pre class="programlisting">
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| 101 | G4DigiManager * fDM = G4DigiManager::GetDMpointer();
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| 102 | MyDigitizer * myDM = fDM->Digitize( "/myDet/myCal/myEMdigiMod" );
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| 103 | </pre></div><p>
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| 104 | </p><h5><a name="id432095"></a>
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| 105 | How to get hitsCollection and/or digiCollection
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| 106 | </h5><p>
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| 107 | <span class="emphasis"><em>G4DigiManager</em></span> has the following methods to access to the
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| 108 | hits or digi collections of the currently processing event or of
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| 109 | previous events.
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| 110 | </p><p>
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| 111 | First, you have to get the collection ID number of the hits or
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| 112 | digits collection.
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| 113 |
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| 114 | </p><div class="informalexample"><pre class="programlisting">
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| 115 | G4DigiManager * fDM = G4DigiManager::GetDMpointer();
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| 116 | G4int myHitsCollID = fDM->GetHitsCollectionID( "hits_collection_name" );
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| 117 | G4int myDigiCollID = fDM->GetDigiCollectionID( "digi_collection_name" );
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| 118 | </pre></div><p>
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| 119 | </p><p>
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| 120 | Then, you can get the pointer to your concrete
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| 121 | <span class="emphasis"><em>G4THitsCollection</em></span> object or
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| 122 | <span class="emphasis"><em>G4TDigiCollection</em></span> object of the currently processing event.
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| 123 |
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| 124 | </p><div class="informalexample"><pre class="programlisting">
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| 125 | MyHitsCollection * HC = fDM->GetHitsCollection( myHitsCollID );
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| 126 | MyDigiCollection * DC = fDM->GetDigiCollection( myDigiCollID );
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| 127 | </pre></div><p>
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| 128 | </p><p>
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| 129 | In case you want to access to the hits or digits collection of
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| 130 | previous events, add the second argument.
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| 131 |
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| 132 | </p><div class="informalexample"><pre class="programlisting">
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| 133 | MyHitsCollection * HC = fDM->GetHitsCollection( myHitsCollID, n );
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| 134 | MyDigiCollection * DC = fDM->GetDigiCollection( myDigiCollID, n );
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| 135 | </pre></div><p>
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| 136 |
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| 137 | where, <code class="literal">n</code> indicates the hits or digits collection of the
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| 138 | <code class="literal">n</code><sup>th</sup> previous event.
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| 139 | </p></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ch04s04.html"><img src="AllResources/IconsGIF/prev.gif" alt="Prev"></a> </td><td width="20%" align="center"><a accesskey="u" href="ch04.html"><img src="AllResources/IconsGIF/up.gif" alt="Up"></a></td><td width="40%" align="right"> <a accesskey="n" href="ch04s06.html"><img src="AllResources/IconsGIF/next.gif" alt="Next"></a></td></tr><tr><td width="40%" align="left" valign="top">4.4.
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| 140 | Hits
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| 141 | </td><td width="20%" align="center"><a accesskey="h" href="index.html"><img src="AllResources/IconsGIF/home.gif" alt="Home"></a></td><td width="40%" align="right" valign="top"> 4.6.
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| 142 | Object Persistency
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| 143 | </td></tr></table></div></body></html>
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