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BBQ and Other Developments

BBQ and Other Developments. Peter Cameron. Outline. 60Hz harmonics - covered yesterday Chromaticity measurement/feedback slow (1Hz) radial modulation – the baseline slow (<0.5 fs) or fast (>>fs) phase modulation multitone continuous head-tail e-cloud tune shift along the bunch

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BBQ and Other Developments

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  1. BBQ and Other Developments Peter Cameron APEX Cameron BBQ 3Nov06

  2. Outline • 60Hz harmonics - covered yesterday • Chromaticity measurement/feedback • slow (1Hz) radial modulation – the baseline • slow (<0.5 fs) or fast (>>fs) phase modulation • multitone • continuous head-tail • e-cloud tune shift along the bunch • Central frequency measurement • two parameters – non-lin chrom and momentum offset • BTF • optimize (Wolfram) • BBTF for lumi,… • Monopole squid APEX Cameron BBQ 3Nov06

  3. Chromaticity Measurement and Feedback • Chrom feedback – the final step in ramp ‘automation’? • “Present measurement quality is questionable” – AD et al • Possible alternative techniques for continuous measurement (desirable for feedback) • phase modulation (SPS, Tevatron, RHIC) • advantage - does not stress tune tracker (mod freq beyond PLL BW) • disadvantages – frequency must avoid synchrotron frequency, possible beam loss, not clear S/N is better than slow radial • 3 tone method (Hermann’s suggestion – 100 tone) (SPS, RHIC?) • advantage – no momentum perturbation • disadvantages – additional excitation/emittance growth, complication of synchrotron satellites, requires knowledge of eta, bunch length,… • continuous head-tail (SPS, Tevatron, RHIC) • advantage – no momentum perturbation • disadvantage – no proper theoretical understanding (yet) APEX Cameron BBQ 3Nov06

  4. chrom - good results under sequencer control Summary of Chromaticity gt +5 Q' ramp 6380 -5 dp/p of +/-10-4 gives ~+/-100m radial modulation (RHIC&LHC) vert +5 Q' horiz ramp 6381 -5 gt in RHIC modulation is at 1Hz +5 Q' ramp 6382 -5 APEX Cameron BBQ 3Nov06

  5. Chromaticity Measurement and Feedback • Chrom feedback – the final step in ramp ‘automation’? • “Present measurement quality is questionable” – AD et al • Possible alternative techniques for continuous measurement (desirable for feedback) • phase modulation (SPS, Tevatron, RHIC) • advantage - does not stress tune tracker (mod freq beyond PLL BW) • disadvantages – limited to <~1/2 synchrotron frequency, possible beam loss, not clear S/N is better than slow radial • 3 tone method (Hermann’s suggestion – 100 tone) (SPS, RHIC?) • advantage – no momentum perturbation • disadvantages – additional excitation/emittance growth, complication of synchrotron satellites, requires knowledge of eta, bunch length,… • continuous head-tail (SPS, Tevatron, RHIC) • advantage – no momentum perturbation • disadvantage – no proper theoretical understanding (yet) APEX Cameron BBQ 3Nov06

  6. SPS testing Sep 2006 courtesy Ralph Steinhagen APEX Cameron BBQ 3Nov06

  7. so far – S/N poor for comparatively large dp/p APEX Cameron BBQ 3Nov06

  8. Chromaticity Measurement and Feedback • Chrom feedback – the final step in ramp ‘automation’? • “Present measurement quality is questionable” – AD et al • Possible alternative techniques for continuous measurement (desirable for feedback) • phase modulation (SPS, Tevatron, RHIC) • advantage - does not stress tune tracker (mod freq beyond PLL BW) • disadvantages – limited to <~1/2 synchrotron frequency, possible beam loss, not clear S/N is better than slow radial • 3 tone method (Hermann’s suggestion – 100 tone) (SPS, RHIC?) • advantage – no momentum perturbation • disadvantages – additional excitation/emittance growth, complication of synchrotron satellites, requires knowledge of eta, bunch length,… • continuous head-tail (SPS, Tevatron, RHIC) • advantage – no momentum perturbation • disadvantage – no proper theoretical understanding (yet) APEX Cameron BBQ 3Nov06

  9. courtesy C.Y. Tan APEX Cameron BBQ 3Nov06

  10. courtesy C.Y. Tan APEX Cameron BBQ 3Nov06

  11. Multi-tone method • Recent (yesterday) results from SPS • 3 tones – central lock plus 2 side tones • same kicker power at all 3 lines • 40Hz offset • PLL BW 20 Hz • fs ~100Hz to 200Hz • general statement - “good results” - no quantitative data yet • Difficult to implement at RHIC • varying synchrotron frequency on ramp, as low as ~10Hz at transition • PLL BW ~10Hz • just the same, it is worth studying, especially in light of…… • Hermann’s suggestion – 10 tone? 100 tone? • 3D AFE gives headroom on S/N before emittance growth becomes an issue • with FPGA-based BBQ it becomes somewhat trivial (at least from hardware/software point-of-view) to lock MANY loops on the beam • starts to look more like continuous BTF APEX Cameron BBQ 3Nov06

  12. Chromaticity Measurement and Feedback • Chrom feedback – the final step in ramp ‘automation’? • “Present measurement quality is questionable” – AD et al • Possible alternative techniques for continuous measurement (desirable for feedback) • phase modulation (SPS, Tevatron, RHIC) • advantage - does not stress tune tracker (mod freq beyond PLL BW) • disadvantages – limited to <~1/2 synchrotron frequency, possible beam loss, not clear S/N is better than slow radial • 3 tone method (Hermann’s suggestion – 100 tone) (SPS, RHIC?) • advantage – no momentum perturbation • disadvantages – additional excitation/emittance growth, complication of synchrotron satellites, requires knowledge of eta, bunch length,… • continuous head-tail (SPS, Tevatron, RHIC) • advantage – no momentum perturbation • disadvantage – no proper theoretical understanding (yet) APEX Cameron BBQ 3Nov06

  13. continuous head-tail APEX Cameron BBQ 3Nov06

  14. Rhodri Jones – continuous head tail 500 turn simulation results, phase difference between head and tail (settling time evident) APEX Cameron BBQ 3Nov06

  15. x ~ 2 head tail Marek and Rhodri x ~ 6 1 second x ~ 2 February 2006 RHIC Run 6 - continuous head-tail chromaticity measurement using BBQ (no momentum perturbation) mean = .758 lowpass filtered head x tail x ~ 6 mean = .283 APEX Cameron BBQ 3Nov06

  16. Chromaticity Measurement and Feedback • Chrom feedback – the final step in ramp ‘automation’? • “Present measurement quality is questionable” – AD et al • Possible alternative techniques for continuous measurement (desirable for feedback) • phase modulation (SPS, Tevatron, RHIC) • advantage - does not stress tune tracker (mod freq beyond PLL BW) • disadvantages – limited to <~1/2 synchrotron frequency, possible beam loss, not clear S/N is better than slow radial • 3 tone method (Hermann’s suggestion – 100 tone) (SPS, RHIC?) • advantage – no momentum perturbation • disadvantages – additional excitation/emittance growth, complication of synchrotron satellites, requires knowledge of eta, bunch length,… • continuous head-tail (SPS, Tevatron, RHIC) • advantage – no momentum perturbation • disadvantages • no proper theoretical understanding (yet – effort at both CERN and FNAL) • RHIC results not repeated at SPS • Marek is working on improved detector APEX Cameron BBQ 3Nov06

  17. Outline • 60Hz harmonics - covered yesterday • Chromaticity measurement/feedback • slow (1Hz) radial modulation – the baseline • slow (<0.5 fs) or fast (>>fs) phase modulation • multitone • continuous head-tail • e-cloud tune shift along the bunch – use 3D AFE? • Central frequency measurement • two parameters – non-lin chrom and momentum offset • BTF • optimize (Wolfram) • BBTF for lumi,… • Monopole squid APEX Cameron BBQ 3Nov06

  18. Outline • 60Hz harmonics - covered yesterday • Chromaticity measurement/feedback • slow (1Hz) radial modulation – the baseline • slow (<0.5 fs) or fast (>>fs) phase modulation • multitone • continuous head-tail • e-cloud tune shift along the bunch • Central frequency measurement • ‘two’ parameters – non-linearities and momentum offset • BTF • optimize (Wolfram) • BBTF for lumi,… • Monopole squid APEX Cameron BBQ 3Nov06

  19. Tune spread measurement methods from 23 Jan 04 BMX meeting • Sliding window fit to response to Artus kick • gives amplitude dependence of coherent tune • Schottky – difficult to get needed resolution • (upper b width + lower b width) - (2 x rev width) • gives tune spread due to octupole and higher, (plus beam-beam,…) • Zoomed Schottky • width of central line of incoherent betatron distribution • gives tune spread due to all contributions (sextupole, octupole, beam-beam,…) • Central Frequency - all contributions APEX Cameron BBQ 3Nov06

  20. LF Schottky at Injection • chrom = (lower - upper) / dp/p • tune spread = • (lower + upper) • (2 x rev) • gives tune spread due to octupole and higher, (plus beam-beam,…) APEX Cameron BBQ 3Nov06

  21. zoomed HF Schottky - revolution line • At store with storage RF on • central line ‘infinitely narrow’ • Synchrotron freq • ~ 250Hz APEX Cameron BBQ 3Nov06

  22. LF Schottky at injection - 9 Dec 03 BH ~ 41 Hz ~ .0005 BV ~ 29 Hz ~ .0003 YH ~ 81 Hz ~ .001 YV ~ 30 Hz ~ .0003 APEX Cameron BBQ 3Nov06

  23. APEX Cameron BBQ 3Nov06

  24. Data from Dec 03 RHIC BMX • Max beam lifetime was not at central frequency • At that time not obvious how to improve RHIC performance using this measurement • Steve Tepikian presentation a few weeks ago • effect of NL chrom on tune footprint, beta fcns,… • suggests why CF not optimal • A possible relatively simple APEX: • two knobs – amount beam is off-momentum, and non-lin corrector strength • explore this parameter space for beam lifetime APEX Cameron BBQ 3Nov06

  25. Outline • 60Hz harmonics - covered yesterday • Chromaticity measurement/feedback • slow (1Hz) radial modulation – the baseline • slow (<0.5 fs) or fast (>>fs) phase modulation • multitone • continuous head-tail • e-cloud tune shift along the bunch • Central frequency measurement • ‘two’ parameters – non-linearities and momentum offset • BTF • optimize (Wolfram) • BBTF for lumi,… • Monopole squid APEX Cameron BBQ 3Nov06

  26. Monopole squid • just a heads up • squid based monopole detector proposed to PAC by Chaudhari et al • committee recommendation was to get experience with squid in RHIC IP radiation environment – concern is spurious radiation-induced quantum flux jumps • test installation is in preparation for IP10 • will need ~1hr access at start of APEX to transfer helium to the dewar APEX Cameron BBQ 3Nov06

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