The "three pole factors" are POLE_FACTOR1, POLE_FACTOR2, and POLE_FACTOR3. My understanding of the manual is that adjusting these parameters might lead to beam trajectories that are neither straight nor on-axis inside the undulator. However, when I run elegant, the effect of the end poles on the electron beam trajectory seems really small.elegant manual wrote: The three pole factors are defined so that the trajectory is centered about x = 0 and x′ = 0 with zero dispersion. This wouldn’t be true with the standard two-pole termination, which might cause problems overlapping the laser with the electron beam.
Here is the call to LSRMDLTR:
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UND_LH.01: LSRMDLTR,L=0.48,BU=0.225,PERIODS=12,METHOD="non-adaptive",&
FIELD_EXPANSION="ideal",ACCURACY=0.001,N_STEPS=2000,LASER_WAVELENGTH=7.83e-07,&
LASER_PEAK_POWER=100.0e06,LASER_W0=0.000210,&
POLE_FACTOR1=1,POLE_FACTOR2=1,POLE_FACTOR3=1, &
TIME_PROFILE="laserMOD7.sdds=t+A"
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default (2nd to last line commented out) -> Cx: -3.0e-8 m, Cxp: 1.2e-8 rad
1,1,1 (as shown above in the code block) -> Cx: -4.3e-11 m, Cxp: -4.5e-7 rad
1,10,1 (grossly unmatched undulator) -> Cx: -3.9e-2 m, Cxp: -1.6e-1 rad
Am I missing something about how the end compensation works?
Edit:
I have just now tried LSRMDLTR with the following settings:
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0,0,0 (uncompensated?) -> Cx: -2.2 mm, Cxp: -9.0 mrad
Radia calculation -> Cx: 3.6 mm, Cxp: 10.6 mrad