Field measurement at IHEP

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Field measurement at IHEP

• Goal of the measurement
• Spot bad magnets
• Short layered
• Check multipole component
• Reference plate
• Take data to be used for beam operation
• Strength reproducibility when re-aseembled
• Not reliable

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Measured the same 4 reference magnet on
different days.
0.5 !!!
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Comments on the IHEP field measurement of the 1st
batch

• Mika Masuzawa
• B2 (main amp)
• Multipoles
• Re-assemble (Open-close) reproducibility
• Raw data

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b2 (main quadrupole)

• Required accuracy of b2 measurement is 5e-04 or
  better.
• Most of the quadrupole magnets will have their
  own power supplies.
• So differences in b2 amplitude do not matter too
  much. But the variations are larger than any
  other magnets that I have measured. Probably due
  to core shimming?

Q magnet
Power supply
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Core shimmed magnet

• B2 variation is large.
• Current dependence
• is large (ex.7). Why?

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Multipole components

• Core shimmed magnets look nice.

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b3 before after core shimming data from Prof.
Yin
No before Data 1
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Open-close reproducibility test (10 magnetnot
shim corrected ) Main amp
This implies Field measurement data can not be
reproduced after chamber installation!
A big jump. What happened?
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Open-close reproducibility test (10 magnet not
shim corrected) magnet center multipole
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Reproducibility of multipole components are
good. May be too good. I see rather
strong current dependence of b3. Why?
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Open-close reproducibility of KEKB magnetmain
amp b2 median plane
110-4
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Open-close reproducibility of KEKB magnetmagnet
center
50µm
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Ler_Q2 ???? mag. 525 bad reproducibility For
example Db22.510-4 b4 was becoming larger. We
found out that the key was not placed
correctly.
210-4
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Reproducibility test with 10 magnet is puzzling
because

• B2 changed by a large amount 0.1
• Magnet center also changed by 250µm in y.
• Bad alignment or magnet shape changed (enlarged
  vertically).
• Note that a bad alignment does not effect the
  main component. B2 and magnet center are
  independent.
• Can we explain (1) and (2) simultaneously?
• Shape changed? May be from to
• Then b4 should change. But I see no change in
  any multipole components.
• Mystery to me.

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Raw data (waveform data from PDI5025)

• Waveform from is not smooth. Very strange.
• Resolution can be improved.

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Waveform for 4 and 5 magnet
Fluctuation is VERY large. We (Egawa-san and
I) have not seen such signals. Connection? S/N? ?
?
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Comparison between PDI5025 (Integrator)_at_IHEPPDI50
25 _at_KEKB Please note that this plot is to
compare the integrator output, not magnets since
the data are from different magnets.
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Enlarged plot of the waveform, comparison between
IHEP and KEK PDI5025
I am concerned about the signal/noise of the
system. Mechanical noise? Electrical
noise? Please tell me that this is OK (convince
me that this is OK).
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IHEP raw data
2nd peak is smaller, indicating large
dipole component.
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Perfect quadrupole waveform (simulation) for one
rotation
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dipole waveform (simulation) for one rotation
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By adding quadrupole and dipole waveform, we can
make the 2nd peak smaller. Note that fft result
of the b2 is still 1
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• Explanation for
• Unsmooth waveform from PDI5025.
• Bad reproducibility
• Data for
• Core shimming
• Where? How?
• Before after core shimming
• Mechanical data?
• b2