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1<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
2<html xmlns="http://www.w3.org/1999/xhtml">
3<head>
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8  <title>PTC_TRACKLINE</title>
9  <style>
10  </style>
11</head>
12<body ="" bgcolor="#ffffff">
13<div style="text-align: center;">
14<center> EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH
15<img src="http://cern.ch/madx/icons/mx7_25.gif" align="right">
16<h1>PTC_TRACKLINE</h1>
17<h2>PERFORMS A PARTICLE TRAJECTORY TRACKING WITH ACCELERATION USING PTC</h2>
18</center>
19</div>
20<div class="madxdocContent">
21<!--  ##########################################################              -->
22<!--  ##########################################################              -->
23<!--  ##########################################################              -->
24<h3 style="margin-top: 0cm; text-align: left; text-indent: 0cm;"
25 align="center"> <span> USER MANUAL </span>
26</h3>
27<!--  ##########################################################              -->
28<h4>SYNOPSIS</h4>
29
30<pre><big>
31
32PTC_TRACKLINE,
33turns         [integer, 1, 0 ] ,
34onetable      [logical, false, true ],
35everystep     [logical, false, true],
36tableallsteps [logical, false, true],
37gcs           [logical, false, true],
38file          [string, "track", "track" ],
39rootntuple    [logical, false, true],
40extension     [string, "", ""];
41</big></pre>
42   
43<table cellpadding="2" cellspacing="2" border="0" width="100%">
44   <tbody>
45
46     <tr>
47       <th valign="Middle" width="150"  align="Center">             Parameter Name    </th>
48       <th valign="Top"    width="100" align="Center">    Type              </th>
49       <th valign="Middle" width="300"  align="Center" colspan="2"> Default value     </th>
50       <th valign="Middle" align="Center">             Description       </th>
51
52     </tr>
53
54     <tr>
55       <th valign="Middle" align="Center">   </th>
56       <th valign="Middle" align="Center">   </th>
57       <th valign="Middle" align="Center" width="150" >   Not present </th>
58       <th valign="Middle" align="Center" width="150" >   Present, but value not specified </th>
59       <th valign="Middle" align="Center">           </th>
60
61     </tr>
62
63     <tr>
64       <td valign="Top" align="center">  turns       </td>
65       <td valign="Top" align="Center"> integer      </td>
66       <td valign="Top" align="Center">    1         </td>
67       <td valign="Top" align="Center">  -           </td>
68       <td valign="Top" align="Left">  Number of turns     </td>
69     </tr>
70
71     <tr>
72       <td valign="Top" align="center">  onetable  </td>
73       <td valign="Top" align="Center">  logical   </td>
74       <td valign="Top" align="Center">   false    </td>
75       <td valign="Top" align="Center">   true     </td>
76       <td valign="Top" align="Left">   If false, tracking data are written to a single table
77                                          for each track for each observation point. Table names follow
78                  the naming <i>filename</i>.obsMMMM.pNNNN, where <br>
79                  <i>filename</i> is settable prefix with <b> file </b> parameter (see below),<br>
80                  MMMM is observation point number and <br>
81                  NNNN is track number <br>
82                  <p>
83                  If true, all data are written to single table called onetable </td>
84     </tr>
85
86     <tr>
87       <td valign="Top" align="center">  file    </td>
88       <td valign="Top" align="Center">  string  </td>
89       <td valign="Top" align="Center">  "track" </td>
90       <td valign="Top" align="Center">  "track" </td>
91       <td valign="Top" align="Left">  Name of file where track parameters are written,
92                                         see description of onetable switch above
93                                         </td>
94     </tr>
95
96     <tr>
97       <td valign="Top" align="center">  rootntuple  </td>
98       <td valign="Top" align="Center">  logical     </td>
99       <td valign="Top" align="Center">  false       </td>
100       <td valign="Top" align="Center">   true       </td>
101       <td valign="Top" align="Left">  Stores data to ROOT file as ntuple.
102                                         Accessible only if RPLOT plugin is available.
103                 i.e. only if madxp is dynamically linked
104                 and RPLOT plugin is present
105                 </td>
106     </tr>
107
108
109     <tr>
110       <td valign="Top" align="center">  everystep </td>
111       <td valign="Top" align="Center">  logical   </td>
112       <td valign="Top" align="Center">    false   </td>
113       <td valign="Top" align="Center">    true    </td>
114       <td valign="Top" align="Left">  Switches on track parameters recording every integration step.
115                                       Normally tracking data are stored only at the end of each element.
116                           Everystep mode allows the user to get finer data points.
117                                       It implies usage of the so called node (thin) layout.
118                           <p>
119                                       Track parameters are stored for each step in thintracking_ptc.txt file.
120                                       Storage of parameters in a table for each step might be very memory
121                           consuming. To switch it off use <b>tableallsteps</b>
122                           <p>
123                           Collective effects can be taken to the account only using this mode
124                           (this feature of PTC is not interfaced into MAD-X).
125
126       </td>
127     </tr>
128
129
130     <tr>
131       <td valign="Top" align="center">  gcs  </td>
132       <td valign="Top" align="Center">  logical     </td>
133       <td valign="Top" align="Center">  false       </td>
134       <td valign="Top" align="Center">   true       </td>
135       <td valign="Top" align="Left">  Instructs the code to store track parameters in
136                                       Global Coordinate System - normally it starts at the
137                           entrance phase of the first element.
138                 </td>
139     </tr>
140
141
142  </tbody>       
143</table>
144
145<!-- <font color="#ff0000"><b>Non existing.</b></font> -->
146
147
148<h4> Description </h4>
149
150<p>This MAD-X command performs ray tracking that takes to the account
151acceleration in traveling wave cavities. It must be invoked in the scope of
152correctly initialized <a href="../ptc_general/ptc_general.html"> PTC
153environment</a>, i.e. after <a href="../ptc_general/ptc_general.html">
154PTC_CREATE_UNIVERSE and PTC_CREATE_LAYOUT commands </a>
155and before corresponding <a href="../ptc_general/ptc_general.html">
156PTC_STOP </a>.
157All tracks that are spawned with
158<a href="../ptc_track/ptc_track.html"> PTC_START </a>
159commands beforehand PTC_TRACKLINE command is issued are tracked. Track
160parameters are dumped at every defined observation point
161(see <a href="../ptc_track/ptc_track.html"> PTC_OBSERVE command</a>).
162Please note that MAD-X always creates observation point at the end of a
163sequence. Depending on value of onetable switch, all output information
164is stored in one table (and also file), or in one table per track per
165observation point is written if the switch is false. The user must note
166that track parameters plotting (see <a href="../plot/plot.html"> PLOT
167command</a>) is only possible if onetable switch is set to false
168(status as for Feb. 2006).
169This unfortunate solution is the legacy of the regular MAD-X track
170command, that is designed for
171circular machines where the user usually tracks a few particles for
172many turns rather then many particles for one turn each. </p>
173
174<p>Tracks that do not fit in aperture are immediately stopped.
175</p>
176
177<p>Behavior of PTC calculations can be adapted with
178<a href="../ptc_auxiliaries/PTC_SetSwitch.html"> PTC_SETSWITCH command </a>
179and with appropriate switches of
180<a href="http://cern.ch/madx/ptc_general/ptc_general.html">
181PTC_CREATE_LAYOUT command</a>.
182</p>
183
184<!--  ##########################################################              -->
185<h4> Command parameters and switches </h4>
186<div>
187<dl>
188  <dt><b> turns </b></dt>
189  <dd> 
190    <i> integer, default value 1, no default value if value explicitly not specified </i>
191    <p> Number of turns around sequence. If layout is not closed then its value is enforced to 1. </p>
192  </dd>
193
194  <dt><b> onetable </b></dt>
195   <dd> 
196    <i> boolean, default value false, if value explicitly not specified then true </i>
197    <p> If true then only one table is created and one file is written
198        to disk. If false one file per track per observation point is written.
199        File format is filename.obsNNNN.pMMMM, where NNNN and MMMM are numbers
200        of observation point and track, respectively. Filename is defined by
201        the switch described below.
202    </p>
203  </dd>
204
205  <dt><b> file </b></dt>
206  <dd> 
207    <i> character string, default is "track" </i>
208    <p> name of file where track parameters are written, see description of onetable switch above. </p>
209  </dd>
210</dl>
211</div>
212
213<!-- ############################################################ -->
214<!-- ############################################################ -->
215<!-- ############################################################ -->
216
217<h3> PROGRAMMERS MANUAL </h3>
218
219The routine PTC_TRACKLINE is implemented in file madx_ptc_trackcavs.f90
220Its single parameter is the number of observation points.
221
222<p>The call sequence from MAD-X interpreter is the following <br>
223exec_command in madxp.c; <br>
224pro_ptc_trackline in madxn.c; This routine creates appropriates tables
225where the track parameters are stored, and after execution of the
226Fortran routine dumps filled table(s) to files.<br>
227w_ptc_trackline_ in wrap.f90; Just interface to the appropriate Fortran
228module <br>
229ptc_trackline in madx_ptc_trackline.f90
230</p>
231
232<p>The key routine that enables appropriate calculation of beam and
233track parameters in the presence of traveling wave cavities is
234setcavities. </p>
235
236<p>Firstly, the ptc_trackline routine finds out which are the
237observation points.
238For this purpose array of integers observedelements is allocated. Its
239length is equal to the number of elements in the sequence.
240All elements are zero by default. If an element with an index n is an
241observation point
242then observedelements[n] is equal to 1. This solution enables fast
243checking if track parameters
244should be sent to a table after a given element. </p>
245
246<p>Further <a href="../ptc_auxiliaries/PTC_SetCavities.html">setcavities subroutine</a>
247is called if it was not executed yet before. </p>
248
249<p>PTC_TRACKLINE reads the track initial parameters from the table with
250the help of gettrack
251function (implemented in C in file madxn.c). For the performance
252reasons gettrack creates a two dimensional array and buffers there all
253the initial track parameters upon first call. The array is destroyed
254with a call of deletetrackstrarpositions function that is performed at
255the very end of ptc_trackline subroutine.
256</p>
257
258<p>Tracking itself is implemented in a doubly nested loop.
259The external one goes over all initiated tracks,
260and the internal one performs tracking of a given track element by element.
261The key PTC routine is called TRACK. It propagates a track described by
262an array of 6 real numbers, denoted as X in equations below.
263The important issue is that they are the canonical variables. In order
264to follow the standard MAD-X representation the values that are written
265to tables and files are scaled appropriately to the reference momentum
266for a given element. In the general case it changes along the line if
267traveling wave cavities are present.
268Hence, momenta xp, yp and zp are
269</p>
270
271<pre>     
272zp=sqrt((1+x(5))**2 - x(2)**2 - x(4)**2) <br>     
273xp = x(2)/zp<br>     
274yp = x(4)/zp<br>
275</pre>
276
277where array x containing 6 elements is the track position in the PTC
278representation, i.e. x(1) is horizontal spacial coordinate, x(2) -
279horizontal momentum,
280x(3) - vertical spacial coordinate, x(4) - vertical momentum,
281x(5) - &delta;p/p<sub>0</sub>c, x(6) - longitudinal coordinate
282(caution, the exact meaning depends on the PTC settings, see
283<a href="../ptc_auxiliaries/PTC_SetSwitch.html"> PTC_SETSWITCH command </a>).
284
285</div>
286</body>
287</html>
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