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Define Misalignments

Alignment errors are defined by the EALIGN command. The misalignments refer to a local reference system for a perfectly aligned machine, placed half-way through the element on the design orbit. Possible misalignments are displacements along the three coordinate axes, and rotations about the coordinate axes. Alignment errors can be assigned to all beam elements except drift spaces. The effect of misalignments is treated in a linear approximation.

Beam position monitors can be given read errors in both horizontal and vertical planes. Monitor read errors are ignored for all other elements. Each new EALIGN statement replaces the misalignment errors for all elements in its range, unless ERROR,ADD has been entered.

The elements to be misaligned must first be selected by the SELECT command. Alignment errors can then be defined by the statement


EALIGN,DX=real,DY=real,DS=real,DPHI=real,DTHETA=real,DPSI=real,
       MREX=real,MREY=real;

Its attributes are:

DX: The misalignment in the -direction for the entry of the beam element (default: 0 m). A positive value displaces the element in the positive -direction.
DY: The misalignment in the -direction for the entry of the beam element (default: 0 m). A positive value displaces the element in the positive -direction.
DS: The misalignment in the -direction for the entry of the beam element (default: 0 m). A positive value displaces the element in the positive -direction.
DPHI: The rotation around the -axis, (default: 0 rad). A positive angle gives a greater -coordinate for the exit than for the entry.
DTHETA: The rotation around the -axis (default: 0 rad) according to the right hand rule.
DPSI: The rotation around the -axis (default: 0 rad) according to the right hand rule.
MREX: The horizontal read error for a beam position monitor (default: 0 m). This is ignored if the element is not a monitor For a positive value the reading for is too high.
MREY: The vertical read error for a beam position monitor (default: 0 m). This is ignored if the element is not a monitor. For a positive value the reading for is too high.

Example:


EALIGN,QF[2],DX=0.002,DY=0.0004*RANF(),DPHI=0.0002*GAUSS();

See also:

**Figure 10.1:** Example of Misplacement in the -plane.
$\begin{figure} \begin{center} \begin{picture}(400,140)(0,30) \put(50,75){\line(1... ...line(0,1){4}} \put(230,67){\line(0,1){16}} \end{picture}\end{center}\end{figure}$

**Figure 10.2:** Example of Misplacement in the -plane.
$\begin{figure} \begin{center} \begin{picture}(400,140)(0,30) \put(50,75){\line(1... ...line(0,1){4}} \put(230,67){\line(0,1){16}} \end{picture}\end{center}\end{figure}$

**Figure 10.3:** Example of Misplacement in the -plane.
$\begin{figure} \begin{center} \begin{picture}(400,150) \put(204,75){\line(1,0){9... ...,-1){2}} \put(233,125){\makebox(0,0){ROT}} \end{picture}\end{center}\end{figure}$

**Figure 10.4:** Example of Read Errors in a monitor.
$\begin{figure} \begin{center} \begin{picture}(400,150)(0,20) \put(204,75){\line(... ...{50}} \put(70,100){\makebox(0,0)[r]{MREY}} \end{picture}\end{center}\end{figure}$

Next: Define Field Errors Up: Error Definitions Previous: Error Mode Contents Index

MAD User Guide, http://wwwslap.cern.ch/mad/