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15 | <div><a href="../index.html">Home</a> > <a href="index.html">at</a> > getnusympmat.m</div> |
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18 | <td align="right"><a href="index.html">Index for at <img alt=">" border="0" src="../right.png"></a></td></tr></table>--> |
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19 | |
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20 | <h1>getnusympmat |
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21 | </h1> |
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22 | |
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23 | <h2><a name="_name"></a>PURPOSE <a href="#_top"><img alt="^" border="0" src="../up.png"></a></h2> |
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24 | <div class="box"><strong>GETNUSYMPMAT - Calculate the tune from a symplectic one-turn matrix</strong></div> |
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25 | |
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26 | <h2><a name="_synopsis"></a>SYNOPSIS <a href="#_top"><img alt="^" border="0" src="../up.png"></a></h2> |
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27 | <div class="box"><strong>function nu = getnusympmat(M44) </strong></div> |
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28 | |
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29 | <h2><a name="_description"></a>DESCRIPTION <a href="#_top"><img alt="^" border="0" src="../up.png"></a></h2> |
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30 | <div class="fragment"><pre class="comment">GETNUSYMPMAT - Calculate the tune from a symplectic one-turn matrix |
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31 | nu = getnusympmat(M44) |
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32 | |
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33 | INPUTS |
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34 | 1. M44 - 4 by 4 symplectic matrix |
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35 | |
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36 | OUTPUTS |
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37 | 1. nu - Tunes |
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38 | |
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39 | Written by Johan Bengtsson</pre></div> |
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40 | |
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41 | <!-- crossreference --> |
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42 | <h2><a name="_cross"></a>CROSS-REFERENCE INFORMATION <a href="#_top"><img alt="^" border="0" src="../up.png"></a></h2> |
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43 | This function calls: |
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44 | <ul style="list-style-image:url(../matlabicon.gif)"> |
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45 | </ul> |
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46 | This function is called by: |
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47 | <ul style="list-style-image:url(../matlabicon.gif)"> |
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48 | <li><a href="modelchro.html" class="code" title="function [Chro, Tune] = modelchro(varargin)">modelchro</a> MODELCHRO - Returns the AT model chromaticity</li><li><a href="modeltune.html" class="code" title="function [FractionalTune, IntegerTune] = modeltune">modeltune</a> MODELTUNE - Returns the model tune (2x1 vector)</li></ul> |
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49 | <!-- crossreference --> |
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50 | |
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51 | |
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52 | <h2><a name="_source"></a>SOURCE CODE <a href="#_top"><img alt="^" border="0" src="../up.png"></a></h2> |
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53 | <div class="fragment"><pre>0001 <a name="_sub0" href="#_subfunctions" class="code">function nu = getnusympmat(M44)</a> |
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54 | 0002 <span class="comment">%GETNUSYMPMAT - Calculate the tune from a symplectic one-turn matrix</span> |
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55 | 0003 <span class="comment">% nu = getnusympmat(M44)</span> |
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56 | 0004 <span class="comment">%</span> |
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57 | 0005 <span class="comment">% INPUTS</span> |
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58 | 0006 <span class="comment">% 1. M44 - 4 by 4 symplectic matrix</span> |
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59 | 0007 <span class="comment">%</span> |
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60 | 0008 <span class="comment">% OUTPUTS</span> |
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61 | 0009 <span class="comment">% 1. nu - Tunes</span> |
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62 | 0010 <span class="comment">%</span> |
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63 | 0011 <span class="comment">% Written by Johan Bengtsson</span> |
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64 | 0012 |
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65 | 0013 <span class="keyword">if</span> nargin < 1 |
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66 | 0014 <span class="keyword">global</span> THERING |
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67 | 0015 M44 = findm66(THERING); |
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68 | 0016 <span class="keyword">end</span> |
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69 | 0017 |
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70 | 0018 n = 4; |
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71 | 0019 |
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72 | 0020 M = M44(1:4, 1:4); |
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73 | 0021 M = M - eye(4); detp = det(M); M = M + 2*eye(4); detm = det(M); M = M - eye(4); |
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74 | 0022 b = (detp-detm)/16.0; c = (detp+detm)/8.0 - 1.0; |
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75 | 0023 th = (M(1, 1)+M(2, 2))/2.0; tv = (M(3, 3)+M(4, 4))/2.0; |
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76 | 0024 b2mc = b^2 - c; |
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77 | 0025 <span class="keyword">if</span> b2mc < 0.0 |
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78 | 0026 nu = [-1.0; -1.0]; |
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79 | 0027 disp(<span class="string">'** Getnu: unstable in tune'</span>); |
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80 | 0028 <span class="keyword">else</span> |
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81 | 0029 <span class="keyword">if</span> (th > tv) |
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82 | 0030 sgn = 1.0; |
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83 | 0031 <span class="keyword">else</span> |
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84 | 0032 sgn = -1.0; |
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85 | 0033 <span class="keyword">end</span> |
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86 | 0034 nu = [acos(sgn*sqrt(b2mc)-b)/(2.0*pi); acos(-b-sgn*sqrt(b2mc))/(2.0*pi)]; |
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87 | 0035 <span class="keyword">for</span> i = 1:n/2 |
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88 | 0036 j = 2*i - 1; |
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89 | 0037 <span class="keyword">if</span> (M(j,j+1) < 0.0) |
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90 | 0038 nu(i) = 1.0 - nu(i); |
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91 | 0039 <span class="keyword">end</span> |
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92 | 0040 <span class="keyword">end</span> |
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93 | 0041 <span class="keyword">end</span></pre></div> |
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94 | <hr><address>Generated on Fri 18-May-2007 17:13:39 by <strong><a href="http://www.artefact.tk/software/matlab/m2html/">m2html</a></strong> © 2003</address> |
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