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APEX Schedule January 20, 2010

APEX Schedule January 20, 2010. 12x12 store AC dipole. 12x12 store. 12x12 store. ramps. 12x12 store. Start maintenance. Optics Measure AC dipole Bai Wang. Optics Measure AC dipole Bai Wang. Beta* squeeze +s* adjustment R-Demolaize. Nonlinear chromaticity Luo. Orbit

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APEX Schedule January 20, 2010

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  1. APEX Schedule January 20, 2010 12x12 store AC dipole 12x12 store 12x12 store ramps 12x12 store Start maintenance Optics Measure AC dipole Bai Wang Optics Measure AC dipole Bai Wang Beta* squeeze +s* adjustment R-Demolaize Nonlinear chromaticity Luo Orbit feedback Minty Marusic IR corrections octupole Zimmer 7pm 8pm 10pm 11pm 2am 5am 6 am AGS OFF 7am

  2. High Lights of APEX Studies • Failed first ramp with Blue beam only • Yellow main dipole stopped ramping at 60 seconds after accramp, feature of Yellow dipole feedback

  3. High Lights of APEX Studies • Beta* squeeze + s* adjustment + optics(Blue): • Guillaume, Gang, Mei • Main goal: use the effect of SC on emittance changes along a store to increase luminosity by dynamically reducing β* (i.e. keep the ratio ε/β* constant). • Tested dynamic beta* squeeze at STAR in both rings. • Optics in Blue were measured before and after beta* squeeze • Didn’t have chance to test s* adjustment

  4. High Lights of APEX Studies DECAY BACKGROUND IR STEERING ZDC RATE Blue IR6, Beta* = 0.675m Blue IR6, Beta* = 0.625m Yellow IR6, Beta* = 0.6m Yellow IR6, Beta* = 0.68m From GRD

  5. High Lights of APEX Studies • 2nd order chromaticity correction Au104: Yun, Dejan • able to bring | Q'' | ~ 500 for both rings in the measurement range. • Blue radial shift went up to 2mm while yellow around 0.5 mm. • small Q'' didn't give small beam decay during measurement for yellow. • Yellow vertical dispersion is about 2m in IR6. • Blue maximum vertical dispersion about 0.8m in IR8. • Blue loss during Q'' measurement located at IP • Yellow loss during Q'' measurement located at IP4 ( s=3195m ). Horizontal and vertical dispersion in IR6 and IR8 can be effectively corrected with small orbit angle bumps in those regions. But it did not provided obvious improvement in the momentum aperture

  6. High Lights of APEX Studies • High order non-linear resonance correction: Chris, Fulvia • Only had ~ one hour beam time • Minimized the horizontal tune shift from 10mm horizonatl bumps by adjusting IR octupoles. This helped to reduce the beam decay in each ring. Max beam decay for a horizontal 10mm bump now seems to be about ~20 percent. • Observed the increase of beam decay being by further minimization of the horizontal tune shift in some instances; needs more investigation • Didn’t get time to investigate vertical bumps to confirm that the major octupole effects have been minimized already. • Still more work to do to automate the technique of non-linear resonance correction using IR bumps

  7. High Lights of APEX Studies • Orbit correction feedback: Michiko, Al, Vadim, Rob, … • verified convergence of feedback at injection energy in all 4 planes • devoted some time to eliminating suspect BPMs – in particular discovered • model/application error concerning one dual-plane in the yellow ring • executed 2 ramps with feedback on in blue and yellow and in both planes • Worked! Vertical orbit rms went down from ~0.5mm to ~0.15mm • Very good reproducibility between the two ramps with feedback on • Beam was aborted late part of the ramp due to a sextupole trip

  8. Convergence Tests blue, X blue, X / Y yellow, X yellow, Y

  9. Ramp w. Orbit Feedback w.o. orbit feedback w orbit feedback Permit pull due to sextupole trip, unknown reason w.o. orbit feedback Manual orbit correction between ramps w orbit feedback

  10. APEX Schedule February 3, 2010 12x12 store 12x12 store AC dipole ramps injection Tune scan Momentum aperture Chromatic corrections Luo Schoefer Trbojevic Optics Measurements Chromatic beta functions Bai Wang Orbit feedback Minty Marusic Ptitsyn BBA Satogata Back 2 Physics 7am 11am noon 4pm 6pm 7pm

  11. Coming APEX Studies: Tune Scan • Tune scan+momentum aperture and chromatic correction in Yellow: Yun, Dejan • Ramp both beams to store with separation bumps • confirm the correction strengths found in last APEX session • dump blue beam, remove separation bumps • scan yellow working point along diagonal while checking Q'' with radial wiggling and observing the beam decay • if time permits, • try Dejan's local sextupole correction • ramp both beams to check rebucketing to see if it improves, i.e. less yellow losses

  12. High Lights of APEX Studies

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