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20050622 Kiyoshi KUBO (KEK)

Quality of extracted beam of ATF -Vertical emittance and Orbit jitters - Present status and possible plans of improvement for ATF2. 20050622 Kiyoshi KUBO (KEK). Vertical emittance of extracted beam. Extracted beam emittance is larger than in the damping ring.

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20050622 Kiyoshi KUBO (KEK)

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  1. Quality of extracted beam of ATF-Vertical emittance and Orbit jitters- Present status and possible plans of improvement for ATF2 20050622 Kiyoshi KUBO (KEK)

  2. Vertical emittance of extracted beam Extracted beam emittance is larger than in the damping ring. Unknown higher order fields in the kickers and the septum magnets are suspected. Cannot be explained by linear x-y or energy-y coupling. (Kicker will be replaced in this summer.) Vertical emittance vs. bunch population. Emittance in DR was measured by Laser wire, in extraction line by wire scanners.

  3. Transverse orbit stability in DR Fast jitter Smaller than present BPM resolution in DR (5~10 micron). Slow orbit change 50 and 100 Hz orbit change, amplitude ~ 10 micron, x and y (related to AC line  No effect to extracted beam.) Slower drift Vertical 1~2 micron at Laser wire region (beta 5m) period ~ a few minutes [Y.Honda, 8th ATF co.lab. mtg.]

  4. Energy jitter in DR (synchrotron oscillation) In 1999, Rms ~ 7.5E-5 (1/8 sE/E) (Amplitude ~ 2E-4) Recently, Rms 1~2E-4 Rms 7E-5 (with feedback)

  5. Pulse to pulse energy jitter in DR, evaluated from horizontal dispersion and measured positions at arc BPMs 0.04% K.Kubo, ATFinternal-99-11

  6. Horizontal orbit jitter in Extraction line. beam size: 50 – 100 micron T.Imai et.al. Horizontal jitter 1/10 – 1/5 of beam size. Main jitter source is not the kicker. (Double-kicker works.)

  7. Vertical position by cavity BPM. ~10 micron p-p. J.Frisch et.al., ATF-03-04

  8. Vertical orbit jitter in Extraction line Slow drift + fast jitter. Fast jitter ~ 2 micron (rms) M.Ross et.al., ATF-03-05

  9. Result from nano-BPM study in Dec. 2004 (M.Ross, et.al) At beta_x=2m, beta_y=3m (40% of nominal beam size) (60% of nominal beam size) ??? Result from cavity BPM study in 2005 (Y.Honda) At beta_y=2m, y jitter < 2 um  40% of nominal beam size (Depend on conditions.)

  10. Quality of extracted beam

  11. Possible plans for improvement Orbit Jitter and drift • Correction of second order dispersion • Extraction kicker replacement • Improvement of double-kicker tuning for precise compensation • DR to Extraction Line feed-forward • Intra-pulse feedback • Improvement of temperature stability of cooling water • etc. Vertical emittamce • Correction of second order dispersion • Extraction kicker replacement (better understood field) • Skew correction using improved beam size monitors • Skew correction with additional diagnostics region • etc.

  12. Simulation of coupling correction using proposed extended diagnostics region in “optimal” beam lineby Mark Woodley(Not completed)

  13. SQ SQ SQ SQ 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 1.3 1.3 1.3 1.3 WS WS WS WS WS – x – y 90° 90° 180° 90° 90° 90° 33° 57° 57° 33° 33° 57° 57° 33° 59.2 8.3 108.0 4.5 59.2 8.3 108.0 4.5 59.2 8.3 σ (μm) For MAD files see http://www.slac.stanford.edu/~mdw/ATF2/optimal M.Woodley

  14. Simulation Parameters • included • perfect beam from Damping Ring (εx=2×10-9 m, γεy=3×10-8 m) • perfect Final Focus (chicane to IP) • vertical dipole misalignments1: 100 μm (rms) • horizontal quadrupole misalignments: 50 μm (rms) • vertical quadrupole misalignments: 30 μm (rms) • quadrupole rolls: 0.3 mrad (rms) • BPM resolution: 5 μm (rms) • wire scanner rolls: -0.2°≤θ≤ +0.2° (uniform) • wire scanner beam size errors: σ = σ0(1+Δσrelative)+Δσabsolute • not included • quadrupole strength errors (ΔK/K) • BPM offsets • BPM rolls • tuning in FF 1some EXT dipoles are assumed to have nonzero sextupole components M.Woodley

  15. Simulation Results (5): γεy thin-lens skew quadrupoles in kicker #1, QM6R, QM7R, and septa |K1L| ≤ 0.015 6.4 ± 2.6 3.7 ± 0.6 perfect wire scanners (no measurement errors) were used during coupling correction 73% of seeds have emittance dilution < 30 % after coupling correction M.Woodley

  16. Simulation Results (6): γεy thin-lens skew quadrupoles in kicker #1, QM6R, QM7R, and septa |K1L| ≤ 0.015 6.4 ± 2.6 20.8 ± 72 wire scanner measurement errors: Δσrelative = 0.1 Δσabsolute = 1 μm |roll| < 0.2° 50% of seeds have emittance dilution > 100 % after coupling correction M.Woodley

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