Undulator Fields at Dx 8 cm P' Emma Feb' 20, 2006

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Undulator Fields at Dx 8 cmP. EmmaFeb. 20,
2006

• Earths field effect
• y-trajectory shims
• Steering corrections (do not use quads?)

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Measured Bx field spike due to y-trajectory shim
(2/9/06)
?Bxds 750 G-cm
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Start with undulator extracted and 0.3-G Earths
field (Bx only)
Earths field (Bx 0.3 G) before steering
(no undulator focusing beyond FODO)
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Now steer using only dipole coils
1 random seed
?300 G-cm corrector limit
(0.3 G)?(132 m) 3960 G-cm (3960 G-cm)/33 120
G-cm
0.3-G Earths field only Steering coil settings
after steering
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Remove Earths field, but now include 10
y-trajectory shims per segment with Gaussian
random errors of 75 G-cm rms
10 random seeds
before steering
(assumes 150-G spikes are a 2s event in fact
spike was 750 G-cm!)
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Add back Earths field (0.3-G), and also include
10 y-trajectory shims per segment with Gaussian
random errors of 75 G-cm rms
10 random seeds
before steering
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One random seed with Earths field (0.3-G) and 10
y-trajectory shims per segment with Gaussian
random errors of 75 G-cm rms
1 random seed
before steering
after steering
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Steering coil settings after steering (Earths
field of 0.3-G and 10 y-trajectory shims per
segment)
1 random seed
?300 G-cm corrector limit
Steering coil settings go beyond maximum range
would need to move quads to steer (undesirable)!
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One random seed without Earths field, but 10
y-trajectory shims per segment with Gaussian
random errors of 75 G-cm rms
1 random seed
before steering
after steering
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Steering coil settings after steering (Without
Earths field, but 10 y-trajectory shims per
segment)
1 random seed
?300 G-cm corrector limit
Still need to move quads!
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y-trajectory after steering (Earths field of
0.3-G and 10 y-trajectory shims per segment)
1 random seed
mean accumulated phase error per segment at 1.5 Å
?Df? 26/segment
0.3-G Earths field 10 y-trajectory shims per
segment with 75 G-cm rms
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Conclusions

• With undulators extracted, Earths field and
  shims can kick electron beam
• Steering with Earths field at 0.3 G offsets
  corrector coils by 120 G-cm (40 of maximum)
• In order to keep undulator corrector coils in
  range with Earths field, we need to keep the
  peak shim-induced Bx spikes to lt30 G-cm