Slide 1

Update of the SPS transverse impedance model C. Zannini, G. Rumolo, B. Salvant Acknowledgments: H. Bartosik, O.Berrig, F. Caspers, E. Chapochnikova, G. Iadarola, E. Mtral, N. Mounet, V.G. Vaccaro, J. E. Varela Slide 2 SPS transverse impedance model Elements included in the database: 106 BPHs (CST 3D simulations) 96 BPVs (CST 3D simulations) 200 MHz cavities without couplers (CST 3D simulations) 800 MHz cavities without couplers (CST 3D simulations) Wall impedance that takes into account the different SPS vacuum chambers (analytical calculations) 19 kickers (CST 3D simulation) Broadband impedance of the flanges (CST 3D simulations) KickersBeam pipe BPH BPV TW 200MHz and 800MHz Flanges Slide 3 SPS transverse impedance model 3 Peaks due to the serigraphy of the extraction kickers Slide 4 SPS transverse impedance model 4 Broadband impedance from kickers, flanges and resistive wall Slide 5 SPS transverse impedance model 5 Peaks due to the RF system and BPMs Slide 6 SPS transverse impedance model Benchmark with beam measurements Tune shift Instability behavior Slide 7 Benchmark of the SPS impedance model: tune shift measurements 100 % 20 % 40 % 60 % 80 % The SPS impedance model explains more than 90% of the measured vertical coherent tune shift Vertical coherent tune shift: Measurements performed in September 2012 Slide 8 The SPS impedance model predicts a very small horizontal tune shift (almost flat) in agreement with the measurements Horizontal coherent tune shift: Measurements performed in February 2013 Benchmark of the SPS impedance model: tune shift measurements Slide 9 Benchmark of the SPS impedance model: instability behavior Two regimes of instability in measurements Fast instability threshold with linear dependence on l Slow instability for intermediate intensity and low l Very well reproduced with HEADTAIL simulations SPS impedance model includes kickers, wall, BPMs and RF cavities Direct space charge not included 9 H. Bartosik measurementsHEADTAIL simulations 4.5x10 11 p/b @ 0.35 eVs nominal Island of slow instability Slide 10 New elements to be added in the model Simulations are ongoing or must be finalized Septa Wire scanner Non standard elements (special transitions, valves) Update due to future installations and modifications New wire scanner New kicker for high bandwidth feedback system New MSI-V septum Serigraphy of the last MKE (7/8 were already serigraphed in the 2012) Slide 11 Thank you for your attention Slide 12 Evolution of the extraction kickers in the SPS 201488 Post-LS1 Slide 13 F. Caspers, T. Kroyer, M. Barnes, E. Gaxiola et al. 13 Serigraphy Seven out of eight SPS extraction kickers have been serigraphed Realistic models: SPS extraction kicker (MKE-L) Slide 14 Realistic models: MKE kicker with serigraphy Slide 15 f=44 MHz Comparing MKE with and without serigraphy Slide 16 The peak observed in the MKE with serigraphy is a quarter-wavelength resonance on the finger length Comparing MKE with and without serigraphy Slide 17 The trend of the vertical effective impedance along the last 10 years is in good agreement with the expected changing of the kicker impedance model Kickers play a major role in the SPS total impedance Evolution of the extraction kickers in the SPS: vertical tune shift Slide 18 The trend of the horizontal effective impedance along the last 10 years is in good agreement with the expected changing of the kicker impedance model Kickers play a major role in the SPS total impedance Evolution of the extraction kickers in the SPS: horizontal tune shift Slide 19 Intra-bunch motion:Q20 measurements HEADTAIL simulations Example for slow instability Example for fast TMC instability H. Bartosik Excellent agreement between measurements and simulation Slide 20 Broadband impedance of step transitions L2 The imaginary part of the transverse impedance is weakly dependent on the cavity length below 1 GHz For the main SPS cavity like structures the first resonating mode is above 1 GHz (r