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Overview of CLIC BDS

Overview of CLIC BDS. Frank Zimmermann CLIC BDS Day 22.11.2005. BDS tasks. focus beams to nm spot size stably collide two beams deliver target luminosity dispose spent beam ensure adequate background conditions protect the machine against self-destruction preserve polarization

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Overview of CLIC BDS

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  1. Overview of CLIC BDS Frank Zimmermann CLIC BDS Day 22.11.2005 Frank Zimmermann, CLIC BDS Day, 22.11.2005

  2. BDS tasks • focus beams to nm spot size • stably collide two beams • deliver target luminosity • dispose spent beam • ensure adequate background conditions • protect the machine against self-destruction • preserve polarization • control spin orientation • function at different beam energies • handle multiple bunches and nominal intensity • … Frank Zimmermann, CLIC BDS Day, 22.11.2005

  3. schematic view of beam delivery system Frank Zimmermann, CLIC BDS Day, 22.11.2005

  4. modular layout betatron collimation energy collimation compact final focus IP switch? interaction region exit line dump Frank Zimmermann, CLIC BDS Day, 22.11.2005

  5. optics Raimondi FF ~0.5 km CCS length ~2.0 km final focus. only 1 stage momentum coll. betatron coll. with low bx,y nonzero D’ at IP F.Z., CLIC-NOTE-551 Frank Zimmermann, CLIC BDS Day, 22.11.2005

  6. beam delivery system & beam parameters 61% luminosity loss Frank Zimmermann, CLIC BDS Day, 22.11.2005

  7. IP distribution horizontal phase-space distribution at the IP calculated with Merlin for a nominal bunch particles are found even at amplitudes >1 mm, while the beam size is about 40 nm S. Redaelli et al, CLIC Note 577 (Nanobeam’02) Merlin, x>3sx: 6.7%, x>6sx: 2.3%, y>3 sy: 15.2%, y>6sy: 7.7%, large tail population → for recent studies see talks by T. Asaka & J. Resta Lopez Frank Zimmermann, CLIC BDS Day, 22.11.2005

  8. what is sx,y? S. Redaelli et al, CLIC Note 577 (Nanobeam’02) linear ideal beam sizes: sx=37.3 nm, sy=0.49 nm Gaussian fit ‘loses’ particles Frank Zimmermann, CLIC BDS Day, 22.11.2005

  9. CLIC BDS “footprints” at 3 TeV and 500 GeV F.Z., CLIC-NOTE-551 Frank Zimmermann, CLIC BDS Day, 22.11.2005

  10. compact FF à la Raimondi & Seryi advantages: larger free length l* from last quad to IP, wider momentum bandwidth, reduced beam tails drawbacks: tighter collimation in x, sextupoles near final doublet (tuning knobs) Frank Zimmermann, CLIC BDS Day, 22.11.2005

  11. luminosity performance luminosity losses: SR in bends →DL~-50% momentum spread →DL~-30% SR in final quad’s →DL~-10% simulated luminosity w/o pinch & w/o hourglass as a function of full-width energy spread with & w/o synchrotron radiationfor two different values of bx,y* and assuming gey=10 nm; L0=4.6x1034 cm-2 s-1 F.Z., CLIC-NOTE-551 Frank Zimmermann, CLIC BDS Day, 22.11.2005

  12. 28% luminosity loss from collimation system geometric luminosity without hourglass and without pinch (input distribution from PLACET for old linac pararameters, and taking bx=6 mm, by=70 mm) numbers refer to new beam parameters: 2.56e9, 150 Hz, 22 bunches/ train CLIC-NOTE-551 Frank Zimmermann, CLIC BDS Day, 22.11.2005

  13. spot-size limit from SR in final quadrupoles (Oide effect) O. Napoly CLIC Note 414, 1999 sx ~30 nm limit sy~1 nm limit for gey~20 nm dependence on e as sy~e5/7 Frank Zimmermann, CLIC BDS Day, 22.11.2005

  14. top view of CLIC IR crab cavity crab cavity CLIC-NOTE-551 R. Assmann Frank Zimmermann, CLIC BDS Day, 22.11.2005

  15. final quadrupole study by M. Aleksa & S. Russenschuck indicated preference for permanent magnet CLIC-NOTE-506 stability of magnetic center? asymmetric DT=1 K (9 kJ/m)→Dy=286 nm Frank Zimmermann, CLIC BDS Day, 22.11.2005

  16. or should we reconsider s.c. quadrupole? Frank Zimmermann, CLIC BDS Day, 22.11.2005

  17. synchrotron radiation in solenoid (fringe) field together with vertical dispersion due to crossing angle & solenoid causes vertical beam blow → crossing angle limited to 20 mrad D. Schulte, F. Zimmermann, CLIC-NOTE-484 Frank Zimmermann, CLIC BDS Day, 22.11.2005

  18. spent beam & exit line at 3 TeV wide energy spread D. Schulte, CLIC-NOTE-391 F.Z., CLIC-NOTE-551 conceptual layout of quadrupole- less exit line water dump at 4oC B. Jeanneret & E. Wildner, CLIC-NOTE-421 Frank Zimmermann, CLIC BDS Day, 22.11.2005

  19. polarization spin rotation angle ag~ 3404 times bend angle polarization vector must be matched into the BDS to ensure longitudinal polarization at the IP R. Assmann, F. Zimmermann, CLIC-NOTE-501 Frank Zimmermann, CLIC BDS Day, 22.11.2005

  20. collimation requirements: • remove beam halo to suppress detector background • arising from synchrotron radiation and beam loss • provide minimum distance from collimators to • collision point for muon suppression • ensure collimator survival and machine protection • against errand beam pulses • not be excessively long • not amplify incoming trajectory fluctuations via • collimator wake fields Frank Zimmermann, CLIC BDS Day, 22.11.2005

  21. SR fans with beam envelopes at 14 sx & 83 sy O. Napoly CLIC-NOTE-446 Frank Zimmermann, CLIC BDS Day, 22.11.2005

  22. surface of 20-mm gold-plated Ti-alloy collimator at the end of SLC linac after damage; CLIC beam is ~104 times more intense! collimator survival? Frank Zimmermann, CLIC BDS Day, 22.11.2005

  23. LC collimation concept: thin spoilers followed by thick absorbers [H. DeStaebler & D. Walz]; spoiler increases angular divergence, reduces risk of fracture and/or melting Frank Zimmermann, CLIC BDS Day, 22.11.2005

  24. nominal beam sizes at CLIC spoilers superposed on ‘FJP’ damage threshold diagram ‘FJP’ = S. Fartoukh, B. Jeanneret & J. Pancin CLIC-NOTE-477 Frank Zimmermann, CLIC BDS Day, 22.11.2005

  25. CLIC failure modes & machine protection • large betatron oscillations are not easily generated • from pulse to pulse; and in the linac they rapidly filament • & emittance increases by ~2 orders of magnitude • energy errors will occur much more frequently, e.g., • due to missing or mis-phased drive beams, injection • phase errors, or charge fluctuation • CLIC philosophy: demand passive survival for momentum • errors; but allow sacrificial betatron collimators (shorter length) failure mode study by Daniel Schulte & F.Z. at PAC2001 Frank Zimmermann, CLIC BDS Day, 22.11.2005

  26. simulated effective beam size sr=(sxsy)1/2 at 1st spoiler; error bar indicates minimum and maximum over 10 random seeds various failure modes CLIC-NOTE-492 Frank Zimmermann, CLIC BDS Day, 22.11.2005

  27. various failure modes simulated centroid betatron oscillation amplitudes at the first spoiler, norma- lized to unperturbed rms beam sizes; error bars show min. and max. over 10 random seeds these pulses would destroy the betatron collimators these pulses might destroy the betatron collimators tighten momentum collimation depth to intercept all dangerous pulses by the momentum spoiler! CLIC-NOTE-492 Frank Zimmermann, CLIC BDS Day, 22.11.2005

  28. transverse collimation depth: from synchrotron radiation & beam loss in final quadrupoles on incoming side only bx from SR fan in final doublet: about +/- 10 sx by from SR fan in final doublet: about +/- 80 sy momentum collimation depth: failure modes & machine protection d from linac failure modes: about +/- 1.5% Frank Zimmermann, CLIC BDS Day, 22.11.2005

  29. collimator parameters scattered beam size on d-absorber: sr ~1.1 mm!? should sr>r.l.? Frank Zimmermann, CLIC BDS Day, 22.11.2005

  30. muon background Geant-4 simulation for 10000 e- lost on first spoiler size of magnets matters! (H. Burkhardt) magnetized cyl. unmagnetized cyl. radius 20 cm unmagnetized cyl. & only 1st photon unmagnetized cyl. radius 50 cm (H. Burkhardt, Nanobeam 2002) Frank Zimmermann, CLIC BDS Day, 22.11.2005

  31. max. jitter enhancement from collimator wake carbon spoiler seems not acceptable; Be spoiler possible; absorbers from Cu-coated Ti & pure Cu both ok (Redaelli) 4 spoilers & 4 absorbers nominal CLIC-NOTE-579 Frank Zimmermann, CLIC BDS Day, 22.11.2005

  32. alternative nonlinear collimation system better optical performance reduced wake fields shorter? basic scheme → talks by A. Faus-Golfe & J. Resta Lopez Frank Zimmermann, CLIC BDS Day, 22.11.2005

  33. laser wire as beam-size monitor? energy distribution along old CLIC BDS from 1000 laser-wire Compton scatters total energy loss per bunch train along the CLIC BDS due to 0.1% flat halo backgrounds completely swamp laser-wire signal! G.A. Blair, BDSIM simulation, Nanobeam2002 Frank Zimmermann, CLIC BDS Day, 22.11.2005

  34. margins & overheads? S. Redaelli’s simulations indicate 25-30% luminosity loss due to fast ground motion 1996 NLC ZDR estimated 20% luminosity loss due to limited beam-based tuning precision for 16 important IP aberrations (Irwin et al) we could expect a total luminosity loss >50% due to these effects Frank Zimmermann, CLIC BDS Day, 22.11.2005

  35. Frank Zimmermann, CLIC BDS Day, 22.11.2005

  36. open questions & outstanding tasks • simulate luminosity performance with errors, ground motion, component jitter, feedback, and realistic tuning, and noisy diagnostics • integrated simulation, including realistic beam distribution from linac with its own errors and tails • improve performance of present system, especially collimation (→shorter, wider bandwidth, higher luminosity), characterize collimation efficiency • fully master design of compact final focus • Be spoilers acceptable? beam size at absorber? • wake field effects, electron cloud, etc. Frank Zimmermann, CLIC BDS Day, 22.11.2005

  37. thank you for your attention! Frank Zimmermann, CLIC BDS Day, 22.11.2005

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