Elias Métral, COULOMB’05, Senigallia (AN), Italy, September 12-16, /29 OBSERVATION OF OCTUPOLE DRIVEN RESONANCE PHENOMENA WITH SPACE CHARGE AT THE CERN PROTON SYNCHROTRON Invited talk (40 min, 29 slides) E. Métral M. Giovannozzi, M. Martini, R. Steerenberg (CERN), G. Franchetti, I. Hofmann (GSI) with  2 measurement campaigns:  October 2002  September 2003

Elias Métral, COULOMB’05, Senigallia (AN), Italy, September 12-16, /29 u Mechanism anticipated by G. Franchetti & I. Hofmann, which involves  Space charge tune spread  Nonlinear (octupole) resonance  Synchrotron motion INTRODUCTION Regime of loss-free core-emittance blow-up Regime where continuous loss occurs  Due to longitudinal motion See Giuliano’s talk on Tuesday

Elias Métral, COULOMB’05, Senigallia (AN), Italy, September 12-16, /29 EXPERIMENTAL SETUP Time [ms] Injection 1 st profile measurement with a Fast Wire Scanner (20 m/s) Last profile measurement Powering of the octupole u 1 octupole pulsed with 310 u Profile measurement in H u Profile measurement in V

Elias Métral, COULOMB’05, Senigallia (AN), Italy, September 12-16, /29 OTHER BEAM AND MACHINE PARAMETERS ParameterValueUnit Circumference628m Horiz. / vert. beam pipe diameter14 / 7cm Superperiodicity10 Kinetic energy1.4GeV Vert. tune6.12 Horiz. tune6.24 < Q x < 6.32 # of bunches1 # of protons per bunch~ Bunch length (4σ)~ 180ns Horiz. / vert. normalised rms emittances~ 5 / ~ 2.5mm mrad Rms momentum spread~ 1.4  Horiz. / vert. rms beam sizes~ 7 / ~ 4mm Derived horiz. / vert. SC tune shifts~ / ~ Synchrotron period~ 1.5ms

Elias Métral, COULOMB’05, Senigallia (AN), Italy, September 12-16, /29 FIRST MEASUREMENT CAMPAIGN: OCTOBER 2002 (1/3) Loss dominated regime Emittance growth dominated regime G. Franchetti et al., PRSTAB, 6, (2003)

Elias Métral, COULOMB’05, Senigallia (AN), Italy, September 12-16, /29 Octupole ON (40 A) % of losses FIRST MEASUREMENT CAMPAIGN: OCTOBER 2002 (2/3)

Elias Métral, COULOMB’05, Senigallia (AN), Italy, September 12-16, /29 u 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 FIRST MEASUREMENT CAMPAIGN: OCTOBER 2002 (3/3)

Elias Métral, COULOMB’05, Senigallia (AN), Italy, September 12-16, /29 SECOND MEASUREMENT CAMPAIGN: SEPTEMBER 2003 (1/21) Vert. emittance equal (here only) to the horiz. one

Elias Métral, COULOMB’05, Senigallia (AN), Italy, September 12-16, / SECOND MEASUREMENT CAMPAIGN: SEPTEMBER 2003 (2/21) 6.25 G. Franchetti et al., ICFA workshop, Bensheim, Germany, October 2004

Elias Métral, COULOMB’05, Senigallia (AN), Italy, September 12-16, /29 Octupole ON Emittance growth dominated regime SECOND MEASUREMENT CAMPAIGN: SEPTEMBER 2003 (3/21)  1 standard deviation of 5 measurements Precision of the emittance measurements ~10%

Elias Métral, COULOMB’05, Senigallia (AN), Italy, September 12-16, /29 Octupole ON SECOND MEASUREMENT CAMPAIGN: SEPTEMBER 2003 (4/21)

Elias Métral, COULOMB’05, Senigallia (AN), Italy, September 12-16, /29 SECOND MEASUREMENT CAMPAIGN: SEPTEMBER 2003 (5/21) 180 ms 1200 ms

Elias Métral, COULOMB’05, Senigallia (AN), Italy, September 12-16, /29 SECOND MEASUREMENT CAMPAIGN: SEPTEMBER 2003 (6/21) 1 st profile and Gaussian fit

Elias Métral, COULOMB’05, Senigallia (AN), Italy, September 12-16, /29 SECOND MEASUREMENT CAMPAIGN: SEPTEMBER 2003 (7/21) Last profile and Gaussian fit

Elias Métral, COULOMB’05, Senigallia (AN), Italy, September 12-16, /29 Octupole ON Beam loss dominated regime SECOND MEASUREMENT CAMPAIGN: SEPTEMBER 2003 (8/21)

Elias Métral, COULOMB’05, Senigallia (AN), Italy, September 12-16, /29 Octupole ON SECOND MEASUREMENT CAMPAIGN: SEPTEMBER 2003 (9/21)

Elias Métral, COULOMB’05, Senigallia (AN), Italy, September 12-16, /29 SECOND MEASUREMENT CAMPAIGN: SEPTEMBER 2003 (10/21) 180 ms 1200 ms

Elias Métral, COULOMB’05, Senigallia (AN), Italy, September 12-16, /29 SECOND MEASUREMENT CAMPAIGN: SEPTEMBER 2003 (11/21) 1 st profile and Gaussian fit

Elias Métral, COULOMB’05, Senigallia (AN), Italy, September 12-16, /29 SECOND MEASUREMENT CAMPAIGN: SEPTEMBER 2003 (12/21) Last profile and Gaussian fit

Elias Métral, COULOMB’05, Senigallia (AN), Italy, September 12-16, /29 SECOND MEASUREMENT CAMPAIGN: SEPTEMBER 2003 (13/21) 180 ms 1200 ms Undershoot due to the measurement device

Elias Métral, COULOMB’05, Senigallia (AN), Italy, September 12-16, /29 SECOND MEASUREMENT CAMPAIGN: SEPTEMBER 2003 (14/21) 1 st profile and Gaussian fit Undershoot due to the measurement device

Elias Métral, COULOMB’05, Senigallia (AN), Italy, September 12-16, /29 SECOND MEASUREMENT CAMPAIGN: SEPTEMBER 2003 (15/21) Last profile and Gaussian fit Undershoot due to the measurement device

Elias Métral, COULOMB’05, Senigallia (AN), Italy, September 12-16, /29 SECOND MEASUREMENT CAMPAIGN: SEPTEMBER 2003 (16/21) From Gaussian fits of previous profiles Integrated intensity of previous profiles Octupole ON G. Franchetti et al., ICFA workshop, Bensheim, Germany, October 2004

Elias Métral, COULOMB’05, Senigallia (AN), Italy, September 12-16, /29 SECOND MEASUREMENT CAMPAIGN: SEPTEMBER 2003 (17/21)

Elias Métral, COULOMB’05, Senigallia (AN), Italy, September 12-16, /29 SECOND MEASUREMENT CAMPAIGN: SEPTEMBER 2003 (18/21) Debunched beam with octupole OFF Q x =6.315 Q x =6.245

Elias Métral, COULOMB’05, Senigallia (AN), Italy, September 12-16, /29 SECOND MEASUREMENT CAMPAIGN: SEPTEMBER 2003 (19/21) Q x =6.315 Q x =6.245 Debunched beam with octupole OFF

Elias Métral, COULOMB’05, Senigallia (AN), Italy, September 12-16, /29 SECOND MEASUREMENT CAMPAIGN: SEPTEMBER 2003 (20/21) 1 st profile and Gaussian fit Same kind of vertical distributions observed in the previous measurements (due to PSB and/or injection process)

Elias Métral, COULOMB’05, Senigallia (AN), Italy, September 12-16, /29 SECOND MEASUREMENT CAMPAIGN: SEPTEMBER 2003 (21/21) Last profile and Gaussian fit

Elias Métral, COULOMB’05, Senigallia (AN), Italy, September 12-16, /29 u By lowering the working point towards the resonance 4 Qx = 25, a gradual transition from a regime of loss-free core emittance blow- up to a regime dominated by continuous beam loss has been observed, as expected by Ingo&Giuliano u Emittance growth in good agreement with predictions u 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, with octupole OFF ~20% of maximum beam losses are already observed!  May explain the difference CONCLUSION