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BBQ and Other Developments

This presentation by Peter Cameron discusses recent advancements in measuring chromaticity and feedback mechanisms relevant to particle accelerators. It covers key concepts such as 60Hz harmonics, radial modulation, and multitone methods. The presentation highlights both advantages and drawbacks of various techniques, including phase modulation and continuous head-tail tests. The challenges of measurement quality, synchronization frequencies, and operational automation are also addressed, along with suggestions for alternative methodologies that may improve feedback accuracy in future experiments.

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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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