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1<html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>5.7.  User Limits</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="ch05.html" title="Chapter 5.  Tracking and Physics"><link rel="prev" href="ch05s06.html" title="5.6.  Physics Table"><link rel="next" href="ch05s08.html" title="5.8.  Track Error Propagation"><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">5.7. 
9User Limits
10</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ch05s06.html"><img src="AllResources/IconsGIF/prev.gif" alt="Prev"></a> </td><th width="60%" align="center">Chapter 5. 
11Tracking and Physics
12</th><td width="20%" align="right"> <a accesskey="n" href="ch05s08.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.Ulim"></a>5.7. 
13User Limits
14</h2></div></div></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="sect.Ulim.Gene"></a>5.7.1. 
15General Concepts
16</h3></div></div></div><p>
17The user can define artificial limits affecting to the Geant4
18tracking.
19
20</p><div class="informalexample"><pre class="programlisting">
21G4UserLimits(G4double uStepMax = DBL_MAX,
22 G4double uTrakMax = DBL_MAX,
23 G4double uTimeMax = DBL_MAX,
24 G4double uEkinMin = 0.,
25 G4double uRangMin = 0. );
26</pre></div><p>
27
28</p><div class="informaltable"><table border="1"><colgroup><col><col></colgroup><tbody><tr><td>
29 <code class="literal">uStepMax</code>
30 </td><td>
31 Maximum step length
32 </td></tr><tr><td>
33 <code class="literal">uTrakMax</code>
34 </td><td>
35 Maximum total track length
36 </td></tr><tr><td>
37 <code class="literal">uTimeMax</code>
38 </td><td>
39 Maximum global time for a track
40 </td></tr><tr><td>
41 <code class="literal">uEkinMin</code>
42 </td><td>
43 Minimum remaining kinetic energy for a track
44 </td></tr><tr><td>
45 <code class="literal">uRangMin</code>
46 </td><td>
47 Minimum remaining range for a track
48 </td></tr></tbody></table></div><p>
49
50Note that <code class="literal">uStepMax</code> is affecting to each step, while all
51other limits are affecting to a track.
52</p><p>
53The user can set <code class="literal">G4UserLimits</code> to logical volume and/or
54to a region. User limits assigned to logical volume do not
55propagate to daughter volumes, while User limits assigned to region
56propagate to daughter volumes unless daughters belong to another
57region. If both logical volume and associated region have user
58limits, those of logical volume win.
59</p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="sect.Ulim.Proc"></a>5.7.2. 
60Processes co-working with G4UserLimits
61</h3></div></div></div><p>
62In addition to instantiating <code class="literal">G4UserLimits</code> and setting it
63to logical volume or region, the user has to assign the following
64process(es) to particle types he/she wants to affect. If none of
65these processes is assigned, that kind of particle is not affected
66by <code class="literal">G4UserLimits</code>.
67
68</p><div class="variablelist"><dl><dt><span class="term">
69 Limitation to step (<code class="literal">uStepMax</code>)
70 </span></dt><dd><p>
71 <code class="literal">G4StepLimiter</code> process must be defined to affected
72 particle types. This process limits a step, but it does not kill a
73 track.
74 </p></dd><dt><span class="term">
75 Limitations to track (<code class="literal">uTrakMax, uTimeMax, uEkinMin,
76 uRangMin</code>)
77 </span></dt><dd><p>
78 <code class="literal">G4UserSpecialCuts</code> process must be defined to affected
79 particle types. This process limits a step and kills the track when
80 the track comes to one of these limits. Step limitation occurs only
81 for the final step.
82 </p></dd></dl></div><p>
83</p><p>
84Example of <code class="literal">G4UserLimits</code> can be found in
85examples/novice/N02 : see <code class="literal">DetectorConstruction</code> and
86<code class="literal">PhysicsList</code>.
87</p></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ch05s06.html"><img src="AllResources/IconsGIF/prev.gif" alt="Prev"></a> </td><td width="20%" align="center"><a accesskey="u" href="ch05.html"><img src="AllResources/IconsGIF/up.gif" alt="Up"></a></td><td width="40%" align="right"> <a accesskey="n" href="ch05s08.html"><img src="AllResources/IconsGIF/next.gif" alt="Next"></a></td></tr><tr><td width="40%" align="left" valign="top">5.6. 
88Physics Table
89 </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"> 5.8. 
90Track Error Propagation
91</td></tr></table></div></body></html>
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