Betatron%20Tune%20Feedback - PowerPoint PPT Presentation

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Betatron%20Tune%20Feedback

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Gated Tune Measurement. Measured horizontal and vertical betatron tunes(HER) HER. HER ... Gated Tune Measurement (cont'd) Fourier spectrum calculated by Eq. ( 5) ... – PowerPoint PPT presentation

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Title: Betatron%20Tune%20Feedback


1
Betatron Tune Feedback
  • T. Ieiri, T. Kawamoto, M. Tobiyama, K. Oide,
  • H. Koiso, Y. Ohnishi
  • KEKB Accelerator Review Committee
  • 2007.Nov.30

Email yukiyoshi.onishi_at_kek.jp
2
Betatron Tunes of the Pilot Bunch
  • The pilot bunch (non-collision bunch)
  • Betatron tunes are measured with a swept-freuency
    method using a tracking analyzer and a gate
    module.

Details will be given by T. Ieiri
3
Gated Tune Measurement
  • Measured horizontal and vertical betatron
    tunes(HER)

HER
dot data red line fitted line
4
Gated Tune Measurement (cont'd)
Fourier spectrum calculated by Eq. (5). n 0.510
and w 0.001.
5
Dependence of Bunch Current
  • Tune shift depends on the bunch current.
  • head-tail wake effects, electron cloud
    effects(only for LER)?
  • Corrected tunes(_at_zero bunch current) are used for
    tune FB.

6
Dependence of Total Beam Current
  • Tune shift due to a quadupole field induced by
    resistive-wall of a chamber in HER. The cross
    section of the chamber is non-axisymmetric.
  • horizontal tune shift Dnx 0.026/ A
  • vertical tune shift Dny -0.037/ A

T. Ieiri et al., Proc. APAC2001
7
Tune Feedback System (online operation)
injection
injection
physics (Tune FB)
8
LER Tune Matching
QR123456, QDFRP, QV1234P, QI2345678P ?
Total 19 quadrupole magnets
  • Arc cell matching condition(ax, bx, ay, by at
    entrance and exit)
  • ax0, ay0 at midpoint,
  • phase advance of two injection kickers 90 deg.
  • Tunes(x,y)

9
HER Tune Matching
QM234567E, QX234567E, QI234567E ? Total 18
quadrupole magnets
  • Arc cell matching condition(ax, bx, ay, by at
    entrance and exit)
  • ax0, ay0 at midpoint, hx 0 at BX2E
  • phase advance of two injection kickers 90 deg.
  • phase and beta requirements from the BxB
    feedback system
  • Tunes(x,y)

Quadrupoles in the whole ring are used to adjust
tunes for the current dependence.
10
Performance of Tune Feedback
  • Residual tunes after the tune feedback

snx 1.3x10-4
snx 8x10-5
sny 2.2x10-4
sny 2.4x10-4
Tune feedback interval is about 30 sec. Since
HER injection rate is large, the tune feedback
can not keep the reference completely(see tails).
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