source: PSPA/madxPSPA/doc/usrguide/Introduction/multipole.html @ 430

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1<head>
2<title>MULTIPOLE</title>
3<!-- Changed by: Chris ISELIN, 27-Jan-1997 -->
4<!-- Changed by: Hans Grote, 17-Jun-2002 -->
5<!-- Changed by: Frank Schmidt, 28-Aug-2003 -->
6</head>
7
8<body bgcolor="#ffffff">
9
10<h2>MULTIPOLE: General Thin Multipole</h2>
11
12<pre>
13label:   MULTIPOLE,LRAD=real,TILT=real,
14         KNL:={..,..,..}, KSL:={..,..,..};
15</pre>
16A MULTIPOLE is a thin-lens magnet of arbitrary order, including a dipole:
17<ul>
18<li>LRAD:
19A fictitious length, which was originally just used to compute synchrotron
20radiation effects.<br> A non-zero <b><font color="#ff0000"> LRAD </b></font> in conjunction
21with the <a href="../control/general.html#option">OPTION</a>
22<b><font color="#ff0000"> thin_foc </b></font> set to a <b><font color="#ff0000"> true </b></font> logical
23value takes into account of the weak focussing of bending magnets.
24<LI>TILT:
25The roll angle about the longitudinal axis (default: 0 rad).
26A positive angle represents a clockwise rotation of the multipole
27element.
28<p><b><font color="#ff0000"> 
29Please note that contrary to MAD8 one has to specify the desired TILT
30angle, otherwise it is taken as 0 rad. We believe that the MAD8
31concept of having individual TILT values for each component and on top
32with default values led to considerable confusion and allowed for
33excessive and unphysical freedom. Instead, in MAD-X the KNL/KSL
34components can be considered as the normal or skew multipole
35components of the magnet on the bench, while the TILT attribute can be
36considered as an tilt alignment error in the machine.
37</b></font>
38<li>KNL:
39The normal multipole coefficients from order zero to the maximum;
40the parameters are positional, therefore zeros must be filled in
41for components that do not exist. Example of a thin-lens sextupole:
42<pre>
43ms:multipole, knl:={0, 0, k2l};
44</pre>
45<li>KSL:
46The skew multipole coefficients from order zero to the maximum;
47the parameters are positional, therefore zeros must be filled in
48for components that do not exist. Example of a thin-lens skew octupole:
49<pre>
50ms:multipole, ksl:={0, 0, 0, k3sl};
51</pre>
52</ul>
53Both KNL and KSL may be specified for the same multipole.
54<p>
55A multipole with no dipole component has no effect on the reference
56orbit,
57i.e. the reference system at its exit is the same as at its entrance.
58If it includes a dipole component,
59it has the same effect on the reference orbit as a dipole
60with zero length and deflection angle K0L, being the first component
61of KNL above.
62<p>
63<address>
64<a href="http://www.cern.ch/Hans.Grote/hansg_sign.html">hansg</a>,
65<a href="http://www.cern.ch/Frank.Schmidt/frs_sign.html">Frank.Schmidt</a>,
66August 28, 2003
67</address>
68
69</body>
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