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OBSERVATION OF OCTUPOLE DRIVEN RESONANCE PHENOMENA WITH SPACE CHARGE

Invited talk (40 min, 29 slides). OBSERVATION OF OCTUPOLE DRIVEN RESONANCE PHENOMENA WITH SPACE CHARGE AT THE CERN PROTON SYNCHROTRON. M. Giovannozzi, M. Martini, R. Steerenberg (CERN), G. Franchetti, I. Hofmann (GSI). E. Métral. with. 14-18 October 2002 22-29 September 2003.

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OBSERVATION OF OCTUPOLE DRIVEN RESONANCE PHENOMENA WITH SPACE CHARGE

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  1. Invited talk (40 min, 29 slides) OBSERVATION OF OCTUPOLE DRIVEN RESONANCE PHENOMENA WITH SPACE CHARGE AT THE CERN PROTON SYNCHROTRON M. Giovannozzi, M. Martini, R. Steerenberg (CERN), G. Franchetti, I. Hofmann (GSI) E. Métral with • 14-18 October 2002 • 22-29 September 2003  2 measurement campaigns:

  2. INTRODUCTION • Mechanism anticipated by G. Franchetti & I. Hofmann, which involves • Space charge tune spread • Nonlinear (octupole) resonance • Synchrotron motion See Giuliano’s talk on Tuesday Regime of loss-free core-emittance blow-up Regime where continuous loss occurs  Due to longitudinal motion

  3. EXPERIMENTAL SETUP 180 310 170 300 1200 Time [ms] Powering of the octupole Injection Last profile measurement 1st profile measurement with a Fast Wire Scanner (20 m/s) • Profile measurement in H • Profile measurement in V • 1 octupole pulsed with

  4. OTHER BEAM AND MACHINE PARAMETERS

  5. FIRST MEASUREMENT CAMPAIGN: 14-18 OCTOBER 2002 (1/3) G. Franchetti et al., PRSTAB, 6, 124201 (2003) Loss dominated regime Emittance growth dominated regime

  6. FIRST MEASUREMENT CAMPAIGN: 14-18 OCTOBER 2002 (2/3) Octupole ON (40 A) 50% of losses 170 300 1200

  7. FIRST MEASUREMENT CAMPAIGN: 14-18 OCTOBER 2002 (3/3) • Conclusions of the data analysis by Ingo&Giuliano • Emittance growth in good agreement with predictions • Losses not yet completely explained  Re-do measurements in 2003  Use the “real” nonlinear model of the PS machine instead of the constant focusing approximation

  8. SECOND MEASUREMENT CAMPAIGN: 22-29 SEPTEMBER 2003 (1/21) Vert. emittance equal (here only) to the horiz. one

  9. SECOND MEASUREMENT CAMPAIGN: 22-29 SEPTEMBER 2003 (2/21) G. Franchetti et al., ICFA workshop, Bensheim, Germany, October 2004 6.265 6.25

  10. Emittance growth dominated regime SECOND MEASUREMENT CAMPAIGN: 22-29 SEPTEMBER 2003 (3/21) Precision of the emittance measurements ~10%  1 standard deviation of 5 measurements Octupole ON

  11. SECOND MEASUREMENT CAMPAIGN: 22-29 SEPTEMBER 2003 (4/21) Octupole ON

  12. SECOND MEASUREMENT CAMPAIGN: 22-29 SEPTEMBER 2003 (5/21) 180 ms 1200 ms

  13. SECOND MEASUREMENT CAMPAIGN: 22-29 SEPTEMBER 2003 (6/21) 1st profile and Gaussian fit

  14. SECOND MEASUREMENT CAMPAIGN: 22-29 SEPTEMBER 2003 (7/21) Last profile and Gaussian fit

  15. Beam loss dominated regime SECOND MEASUREMENT CAMPAIGN: 22-29 SEPTEMBER 2003 (8/21) Octupole ON

  16. SECOND MEASUREMENT CAMPAIGN: 22-29 SEPTEMBER 2003 (9/21) Octupole ON

  17. SECOND MEASUREMENT CAMPAIGN: 22-29 SEPTEMBER 2003 (10/21) 180 ms 1200 ms

  18. SECOND MEASUREMENT CAMPAIGN: 22-29 SEPTEMBER 2003 (11/21) 1st profile and Gaussian fit

  19. SECOND MEASUREMENT CAMPAIGN: 22-29 SEPTEMBER 2003 (12/21) Last profile and Gaussian fit

  20. SECOND MEASUREMENT CAMPAIGN: 22-29 SEPTEMBER 2003 (13/21) 180 ms Undershoot due to the measurement device 1200 ms

  21. SECOND MEASUREMENT CAMPAIGN: 22-29 SEPTEMBER 2003 (14/21) 1st profile and Gaussian fit Undershoot due to the measurement device

  22. SECOND MEASUREMENT CAMPAIGN: 22-29 SEPTEMBER 2003 (15/21) Last profile and Gaussian fit Undershoot due to the measurement device

  23. SECOND MEASUREMENT CAMPAIGN: 22-29 SEPTEMBER 2003 (16/21) From Gaussian fits of previous profiles Integrated intensity of previous profiles G. Franchetti et al., ICFA workshop, Bensheim, Germany, October 2004 Octupole ON

  24. SECOND MEASUREMENT CAMPAIGN: 22-29 SEPTEMBER 2003 (17/21)

  25. SECOND MEASUREMENT CAMPAIGN: 22-29 SEPTEMBER 2003 (18/21) Qx=6.315 Debunched beam with octupole OFF Qx=6.245

  26. SECOND MEASUREMENT CAMPAIGN: 22-29 SEPTEMBER 2003 (19/21) Qx=6.315 Debunched beam with octupole OFF Qx=6.245

  27. SECOND MEASUREMENT CAMPAIGN: 22-29 SEPTEMBER 2003 (20/21) 1st profile and Gaussian fit Same kind of vertical distributions observed in the previous measurements (due to PSB and/or injection process)

  28. SECOND MEASUREMENT CAMPAIGN: 22-29 SEPTEMBER 2003 (21/21) Last profile and Gaussian fit

  29. CONCLUSION • By lowering the working point towards the resonance 4 Qx = 25, a gradual transition from a regime of loss-free coreemittance blow-up to a regime dominated by continuous beam loss has been observed, as expected by Ingo&Giuliano • Emittance growth in good agreement with predictions • Beam losses now better explained than in 2002 (using the nonlinear model of the PS machine instead of the constant focusing approximation) • The observed maximum losses (~30%) are still larger than predicted (~8%) • HOWEVER, withoctupole OFF~20% of maximum beam losses are already observed!  May explain the difference

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