2. Introduction to the High Bandwidth Transverse Feedback W. Hofle on behalf of HBTFB Team Proposed New System vs. Existing Feedback System Brief History of the Project Approach for Implementation

3. HBTFB - High Bandwidth Transverse Feedback Wideband feedback system (GHz bandwidth) for SPS Intra-bunch GHz transverse feedback system Help stabilize beam against Ecloud and TMCI effects Under development with LARP supported by: US-LARP (SLAC, LBNL) LNF-INFN (kicker study) CERN SPS LIU Project Analog Front End Analog Back End Signal Processing BPM Kicker Power Amp ADC DAC Beam transverse position pre-processed sampled position “slices” calculated correction data correction signal pre-distortiondrive signal

4. Existing SPS Transverse Feedback System operates between lowest betatron frequency and 20 MHz (V & H plane) handles large injection errors of the order of several mm Tetrode amplifiers with two tubes drives kicker plates in push-pull configuration (upgrades in 2001) 200 W drive power per tetrode 3 kHz to 20 MHz installed on surface Tetrode amplifier installed in tunnel under kicker tanks 2 vertical kickers @  =42 m each 1536 mm long, 38 mm gap Tunnel with kicker tank and tetrode amplifier in LSS2

5. Existing Transverse Feedback System kicker effective capacitance: C g +2C p = 122 pF not all circuit elements shown, e.g. matching at input 200 W drive power in 50 W 3 dB @ 4.5 MHz R A = 180 W, C eff = 200 pF Tube: RS 2048-CJC or TH561, max current 15A to 16A class AB operational RF voltage 2.6 kV Phase corrected  20 MHz 4.6 kV R A =180 kicker 45p 32p R A =180 L L f < 25 MHz series resonance with L at 37 MHz

6. Existing Feedback: Kick Strength +/- 2.6 kV @ 100 kHz, L=1536 mm, gap d=38 mm +/- 1.83 kV @ 4.5 MHz +/- 0.572 kV @ 20 MHz damps ~5 mm injection error (  =100 m) at 26 GeV/c in 20 turns (gain=0.1) 26 GeV/c: kick per turn 8.3  rad (  0.54 mm at  =100 m) regularly running at 0.5 ms damping time (20 turns) resistive wall growth rate for lowest mode: 0.5 ms to 1 ms G. Kotzian integrated kick strength over the entire structure  41.375 V (transverse) for +/-1 V on kicker plates

7. Comparison of Feedbacks BA2 Damper (only V-plane discussed) detects center of mass oscillations of bunches, feedback in “base-band” performance improving consolidation under way: - dedicated new standard SPS pick-ups (BPCR coupler) - updates for single bunch operation, Q20 and bunchlet scrubbing beam kHz to 20 MHz, high kick strength (good for mm’s of oscillation) 7.2x10 -4 eVs/m (100 kHz) to 1.58x10 -4 eVs/m (20 MHz) corresponding to 215 kV to 46 kV BA3 Proposed High Bandwidth Feedback (V-plane) New approach: Intra-Bunch System similar to stochastic cooling in some way advanced Digital Technology 4-8 GS/s ~10 MHz to >~ 1 GHz, not so high kick strength 10 -5 eVs/m to 10 -4 eVs/m [3 kV to 30 kV], may need several kickers (4x [2x5kW]) low noise receiver, efficient closed orbit rejection rejection of noise by processing extremely important (“processing gain”)

8. Power Requirements - New Feedback System Injection assume only dipolar error at injection (handled by existing feedback) instabilities kick in rapidly, but intra-bunch motion grows from noise noise floor and processing gain main ingredients for estimation of power Performance for given power 30 kV transverse volts kick strength at  =60 m  1.15  rad at 26 GeV/c, kick corresponds to 90  m at  =100 m  at 450 GeV/c: 5  m assume gain of 0.2 (damping time 10 turns)  saturation at 450 GeV/c at 25  m requires 4 kickers of 1 m (see J.Cesaratto) with ~2x5 kW each start with 1 kicker: saturation at 26 GeV/c: 34  m at 2x500 W reasonable approach for next stage design 1 kicker with 3 kV transverse kick for 26 GeV/c with 2x500 W; foresee higher power handling capability ?

9. Brief History - Simulations Ecloud vertical instability is a limitation in the SPS  G. Rumolo R&D: CERN / LARP (SLAC, LBNL) since 2008, LNF-INFN Initial simulations with Headtail code, Ecloud and feedback simulations aimed at 55 GeV/c, SPS injection frequency with PS2, Q26 optics rigid dipole feedback shown insufficient slice-by-Slice Higher Bandwidth feedback cures instability trade-off gain, bandwidth, < 1 GHz sufficient, 200 MHz not sufficient 2-tap Filter tested for the adjustment of the phase, shortest delay approach Subsequent simulations by WARP, CMAD and Headtail focus on Q26 @26 GeV/c in SPS ecloud modeling with bunch trains and feedback (J. L. Vay, WARP code) implementation of multi-tap FIR filters, amplifier models (J. Fox, M. Pivi, C. Rivetta, R. Secondo et al.) fitting of data with reduced models for controller design (C. Rivetta O. Turgut et al.) TMCI and switch to Q20 optics (Headtail, K. Li et al.)

10. Brief History – MD Program, Technology and Approach for Implementation Initial MDs understanding of intra-bunch motion and instrumentation (BPWA pick-ups, R. de Maria et al.) refurbishment for precision measurements (hybrids, cables, loads, U. Wehrle) 25 ns and single bunch, concentrate on single bunch MDs (more MD time available) Single Bunch demonstrator (SLAC) developed for 2012 MDs 4 x 100 W amplifiers on a BPWA PU used as kicker, ~0.5% of existing damper ADC, DAC @3.2 GS/s - 4 GS/s, FPGA processing for single bunch (J. Dusatko et al.) phase compensation (K. Pollack et al.) goal: demonstrate damping on a single bunch Main limitation: 200 MHz bandwidth limit from kicker (length of strip-line) Future options with demonstrator (between LS1 and LS2) extension of demonstrator to bunch trains (LS1) for 48+ bunches access to full bandwidth of demonstrator only with a new kicker kicker study also key for use at higher energy (kick strength !) Full function system commissioning: after LS2

11. Closure of Feedback Loop with Demonstrator Tune shift due to Beam loss Instability Feedback off Feedback active Instability single bunch, 26 GeV, charge ~1E11 These studies use a 200 MHz stripline pickup as kicker. Fractional Tune Turns (x1000) File: 130123_204924 File: 130123_204021 Feedback stabilizes the bunch ! clearly working for dipole mode confirms high sensitivity of receiver circuit confirms feedback possible with the very small kick strength of ~1 kV [transverse] Feedback switched OFF Chromaticity ramped down (close to zero) Chromaticity ramped down (close to zero)

12. THANK YOU FOR YOUR ATTENTION! HBTFB Team and current contributors CERN – H. Bartosik, W. Höfle, G. Iadarola, G. Kotzian, K. Li, E. Montesinos, N. Mounet, G. Rumolo, B. Salvant, D. Valuch, U. Wehrle, C. Zannini SLAC – J. Cesaratto, J. Dusatko, J. D. Fox, S. Johnston, J. Olsen, M. Pivi, K. Pollock, C. Rivetta, O. Turgut LNF-INFN – D. Alesini, A. Drago, S. Gallo, F. Marcellini, M. Zobov LBNL – S. De Santis, Z. Paret, H. Qian KEK – M. Tobiyama

13. Selected Bibliography 2009-2013 [1] J. R. Thompson et al., PAC’09, (2009), pp. 4713-4715. [2] J. D. Fox et al., PAC’09, (2009), pp. 4135-4137. [3] J.-L. Vay et al., IPAC’10, (2010), pp. 2438-2440. [4] C. Rivetta et al., PAC’11, (2011), pp. 1621-1623. [5] R. Secondo et al., IPAC’11, (2011), pp. 1773-1775. [6] M. Pivi et al., IPAC’12, (2012), pp. 3147-3149. [7] J. M. Cesaratto et al., IPAC’12, (2012), pp. 112-114. [8] K. Li et al., IPAC’13, WEPME042, (2013) [9] J. Dusatko et al., IPAC’13, WEPME059, (2013) [10] J. D. Fox et al., IPAC’13, WEPME60, (2013) [11] J. M. Cesaratto et al., IPAC’13, WEPME61, (2013)