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10.66 MAXAMP—A collimating element that sets the maximum transmitted particle amplitudes for all following elements, until the next MAXAMP.

A collimating element that sets the maximum transmitted particle amplitudes for all following elements, until the next MAXAMP.
Parallel capable? : yes
GPU capable? : yes
Back-tracking capable? : yes

Parameter NameUnitsType Default

Description

X_MAX M double 0.0

x half-aperture

Y_MAX M double 0.0

y half-aperture

ELLIPTICAL long 0

is aperture elliptical?

EXPONENT long 2

exponent for boundary equation in elliptical mode. 2 is a true ellipse.

YEXPONENT long 0

y exponent for boundary equation in elliptical mode. If zero, defaults to EXPONENT.
OPEN_SIDE STRINGNULL

which side, if any, is open (+x, -x, +y, -y)

GROUP string NULL

Optionally used to assign an element to a group, with a user-defined name. Group names will appear in the parameter output file in the column ElementGroup

This element sets the aperture for itself and all subsequent elements. The settings are in force until another MAXAMP element is seen. Settings are also enforced inside of KQUAD, KSEXT, KOCT, KQUSE, CSBEND, and CSRCSBEND elements.

This can introduce unexpected behavior when beamlines are reflected. For example, consider the beamline

...  
L1:  LINE=( ... )  
L2:  LINE=( ... )  
MA1: MAXAMP,X_MAX=0.01,Y_MAX=0.005  
MA2: MAXAMP,X_MAX=0.01,Y_MAX=0.002  
BL1: LINE=(MA1,L1,MA2,L2)  
BL:  LINE=(BL1,-BL1)

This is equivalent to

BL:  LINE=(MA1,L1,MA2,L2,-L2,MA2,-L1,MA1)

Note that the aperture MA1 is the aperture for all of the first instance of beamline L1, but that MA2 is the aperture for the second instance, -L1. This is probably not what was intended. To prevent this, it is recommended to always use MAXAMP elements in pairs:

BL1: LINE=(MA2,MA1,L1,MA1,MA2,L2)  
BL:  LINE=(BL1,-BL1)

which is equivalent to

BL:  LINE=(MA2,MA1,L1,MA1,MA2,L2,-L2,MA2,MA1,-L1,MA1,MA2)

Now, both instances of L1 have the aperture defined by MA1 and both instances of L2 have the aperture defined by MA2.

The default values of X_MAX and Y_MAX are 0, which causes the aperture to be ignored. This means one cannot use the MAXAMP element to simulate a completely blocked beam pipe.

MBUMPER

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