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Luminosity Optimisation Overview

Luminosity Optimisation Overview. Philip Burrows (QMUL) Introduction Tools Active component stabilisation Beam-based feedback Beam parameter diagnostics Summary. IP. 1. Introduction. Relative component displacement -> emittance blowup (linac, BDS) mis-steering (FF), esp. final quads

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Luminosity Optimisation Overview

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  1. Luminosity Optimisation Overview • Philip Burrows • (QMUL) • Introduction • Tools • Active component stabilisation • Beam-based feedback • Beam parameter diagnostics • Summary Philip Burrows MDI Workshop, SLAC 6-8/01/05

  2. IP 1. Introduction • Relative component displacement -> • emittance blowup (linac, BDS) • mis-steering (FF), esp. final quads • ‘static’ effects: • misalignments … • diffusive effects: • settling, hydrology … • ‘seismic’ motion: • earthquakes, ocean waves … • cultural/facilities noise: • traffic, pumps, water flow… • slow drifts: • temperature, pressure … Luminosity vs. beam offset 50nm: ~ 80% lost Philip Burrows MDI Workshop, SLAC 6-8/01/05

  3. Available solutions • Optimise site choice + civil/mech. engineering: • minimise (relative) component motion • Active component stabilisation: • compensate via (inertial/optical) feedback • Beam-based feedback/scans: • move beam(s) position/angle via feedback • Integrated system: • some/all of the above working in harmony Philip Burrows MDI Workshop, SLAC 6-8/01/05

  4. Issues for machine-detector Interface • Stabilisation of final doublets • Intra-train and pulse-pulse beam feedback • Beam parameter diagnostics • Terse summary/overview: hopefully raise issues for discussion Philip Burrows MDI Workshop, SLAC 6-8/01/05

  5. 2. Tools • Ground motion data/models • Facilities noise models • Linac -> IP beam transport • PLACET+MERLIN • DIMAD+LIAR • integrated Matlab environment: MatMERLIN, MatLIAR • Beam-beam interaction: luminosity, backgrounds • CAIN • GUINEAPIG • Materials/detector simulations: shower tracking GEANT3 -> GEANT4 • EGS Philip Burrows MDI Workshop, SLAC 6-8/01/05

  6. Site studies + ground motion CDR/TDR: more studies to bound problem? studies of specific sites? (Seryi) Philip Burrows MDI Workshop, SLAC 6-8/01/05

  7. Facilities Noise Not difficult to find noisy environments! Example: noise at SLD TDR: need to model for real engineered MDI design? Philip Burrows MDI Workshop, SLAC 6-8/01/05

  8. Engineering approach(Asiri) Select a Location (Representative Site) Good Geology and Quiet Select and Locate Near-Field (Cryo/compressors, pumps) Geotechnical Studies (Soil/Rock Classification) Attenuation Characteristics of Soil/Rock Estimate Near-Field Excitation (At Their Footings) Far-Field Excitation (Ambient Ground Motion Measurement) Estimate Vibration @ Invert of Beam Housing ( Response to Near and Far Fields Sources) Done O(1) for few sites Revisit for cold ILC Reestablish for cold ILC Acceptance Criteria Yes Adopt as a Concept Design Requirement No Philip Burrows MDI Workshop, SLAC 6-8/01/05

  9. 2. Tools • Ground motion data/models • Facilities noise models • Linac -> IP beam transport • PLACET+MERLIN • DIMAD+LIAR • integrated Matlab environment: MatMERLIN, MatLIAR • Beam-beam interaction: luminosity, backgrounds • CAIN • GUINEAPIG • Materials/detector simulations: shower tracking GEANT3 -> GEANT4 • EGS Philip Burrows MDI Workshop, SLAC 6-8/01/05

  10. Codes Database Pagehttp://hepwww.ph.qmul.ac.uk/~white/accodes/codedeb.htm Philip Burrows MDI Workshop, SLAC 6-8/01/05

  11. Example: GUINEA PIG Pagehttp://hepwww.ph.qmul.ac.uk/~white/accodes/guinea.htm Philip Burrows MDI Workshop, SLAC 6-8/01/05

  12. QMUL High Throughput Cluster (HTC) • 174 x 2 GHz cpus • 40 TB attached storage • GBit ethernet • Peak capacity: • 50k cpu-hours/week • 400k cpu-hours used for • LC simulations (9 mos.) • Another 2-300 ‘boxes’ • by Spring 06 Philip Burrows MDI Workshop, SLAC 6-8/01/05

  13. Linac to IP Simulation Results Repositoryhttp://hepwww.ph.qmul.ac.uk/lcdata/ Philip Burrows MDI Workshop, SLAC 6-8/01/05

  14. Output files Philip Burrows MDI Workshop, SLAC 6-8/01/05

  15. IP 3. Final quadrupole stabilisation • Passive: • ‘cushioned’ magnet supports • support tube connecting opposite sides of IR • Active: • inertial stabilisation • optical anchoring schemes • NB: details linked to final doublet technology (Parker et al), crossing angle … Philip Burrows MDI Workshop, SLAC 6-8/01/05

  16. Final doublet stabilisation: inertial(SLAC, CERN/CLIC …) SLAC: mockup of final quad girder: Non-magnetic inertial sensor CERN: stabilisation of CLIC quad: Sub-nm achieved > few Hz Philip Burrows MDI Workshop, SLAC 6-8/01/05

  17. Final doublet stabilisation: optical(UBC, SLAC, CERN, KEK …) Optical anchor concept 10kg mass: 90 -> 5 nm (ground) 4.5 -> 1.5 nm (isolated) UBC prototype Optical anchor system in development: NanoBPM project (ATF) Philip Burrows MDI Workshop, SLAC 6-8/01/05

  18. ‘Nano’ Project at KEK ATF System test: aim for optical-anchor stabilisation of pair of BPM triplets at nm level, with intra-train beam FB/FF Philip Burrows MDI Workshop, SLAC 6-8/01/05

  19. Possible ATF optical anchor scheme (Oxford):simulations in progress Urner Philip Burrows MDI Workshop, SLAC 6-8/01/05

  20. 4. Beam-based feedback • ‘slow’ upstream orbit feedbacks • IP pulse-pulse feedback (5 Hz) • IP intra-train (bunch-bunch) feedback: 3 MHz • Position and angle corrections: • most critical in vertical dimension Philip Burrows MDI Workshop, SLAC 6-8/01/05

  21. Beam-beam deflection GUINEAPIG simulations (White) Deflection curve depends on: Q, sigma-x, sigma-y, sigma-z … Philip Burrows MDI Workshop, SLAC 6-8/01/05

  22. Intra-train Beam-based Feedback Concept(same hardware for pulse-pulse FB) • Intra-train beam feedback is last line of defence against relative beam misalignment • Key components: • Beam position monitor (BPM) • Signal processor • Fast driver amplifier • E.M. kicker • Fast FB circuit TESLA TDR: principal IR beam-misalignment correction Philip Burrows MDI Workshop, SLAC 6-8/01/05

  23. Zero-degree crossing angle (TESLA TDR) FB BPM Upstream kicker(s) Philip Burrows MDI Workshop, SLAC 6-8/01/05

  24. ‘Large’ crossing angle (NLC) kicker FB BPM Philip Burrows MDI Workshop, SLAC 6-8/01/05

  25. Angle feedback: upstream in BDS Place kicker at point with IP phase. BPM at phase 90 degree downstream from kicker. Philip Burrows MDI Workshop, SLAC 6-8/01/05

  26. Angle feedback: locally near IP – crab cavity(IR with crossing angle) • Fast phase adjust • using a second klystron • and fast phase • difference. Needs careful integration into MDI design! Diagram by J. Frisch Philip Burrows MDI Workshop, SLAC 6-8/01/05

  27. IP Feedback model Linearise Beam-Beam Kick Curve Response Philip Burrows MDI Workshop, SLAC 6-8/01/05

  28. Feedback Algorithm • Proportional-Integral (PI) Controller: • Subtract uPI(k-1) to get recursive algorithm: • 2 free parameters: gains KP and KI : • KP provides fast response to error signal. • KI cancels steady-state error. • Iterate simulation to obtain optimum parameters to give fast correction and maintain collisions at 0.1sy level. Philip Burrows MDI Workshop, SLAC 6-8/01/05

  29. Illustration of Intra-train feedback performance (White/QMUL) (TESLA TDR) OPTIMAL LUMINOSITY y angle scan Excellent starting point: need to add further ‘reality’ … y position scan: optimise signal in pair monitor (+4%) y position FB: restore collisions within 100 bunches 1 seed: post-BBA + GM + wakes Philip Burrows MDI Workshop, SLAC 6-8/01/05

  30. Intra-train beam feedback prototypes and beam tests (QMUL, Oxford, DL, SLAC, KEK …) • FONT1 and FONT2 prototype intra-train FB • systems tested with beam at SLAC/NLCTA. FONT3/FEATHER beam tests at KEK/ATF summer 2005: micron-level stability of 1.3 GeV ATF beam (model of nm- level stability of ILC beam) Cold ILC: robustness, algorithmic control Full delay-loop feedback on: Latency 53ns Philip Burrows MDI Workshop, SLAC 6-8/01/05

  31. Continuing feedback hardware development • Short-term: FONT3 at ATF: aim for micron-level stability of 1 GeV beam • Long-term: • demonstrate robust intra-train FB system for ILC, based on digital signal processing, and ideally test with beam: • requires long bunchtrain with 337 ns bunch spacing • 2005-6: 3 (or 4) bunches x 100 ns at ATF would allow first tests: • stabilise last bunch at 100 nm level as part of Nano project • also feed-forward studies ring -> extraction line? > 2006: 20 bunches x 337ns at ATF/ATF2 would allow FB algorithm development Philip Burrows MDI Workshop, SLAC 6-8/01/05

  32. Backgrounds (QMUL) Feedback system incorporated into GEANT IR model Need to ensure: FB system performance OK, FB material does not cause additional backgrounds in detector. Considering experimental background tests at SLAC/ESA Philip Burrows MDI Workshop, SLAC 6-8/01/05

  33. Pulse-pulse IP beam deflection feedback(Hendricksen) Input GM models A, B, C: Linac->IP tracking + 5 Hz FB (TESLA) <Luminosity> Need for intra-train FB Need to integrate simulation of FBs: upstream slow, active stabilisation, 5Hz, intra-train … Philip Burrows MDI Workshop, SLAC 6-8/01/05

  34. SLC optimised ‘dither’ feedback at IP(Phinney) Deflection scans: 5 knobs/beam : x/y waist, x/y dispersion, coupling Old method: scan of beam size vs. single knob: New method: optimise lumi w. dither FB on each knob Poor resolution, lumi loss Increased lumi, eased ops. Philip Burrows MDI Workshop, SLAC 6-8/01/05

  35. 5. IP beam parameter diagnostics • Sigma x • Sigma y • Sigma z • Sigma x' • Sigma y' • x offset • y offset • x' offset • y' offset • x-waist shift • y-waist shift • Bunch rotation • N particles/bunch • Banana shape • … … • Luminosity What do you want to know?! Philip Burrows MDI Workshop, SLAC 6-8/01/05

  36. Available diagnostics • Transverse emittance: sigma x, sigma y, sigma x’, sigma y’ • laserwire etc. beam size monitors (probably upstream) • Bunch length: sigma z • electro-optic, ODR, Smith-Purcell etc. monitors • Bunch charge: • toroids • Beam position/angle offsets: • beam-beam deflections • Luminosity • Pair/beamstrahlung monitors Philip Burrows MDI Workshop, SLAC 6-8/01/05

  37. Beam diagnostics possibilities in IR limited Lumi mon. (Bhabhas) Forward BSR mon. IP BPM (beam deflections) Philip Burrows MDI Workshop, SLAC 6-8/01/05

  38. Beam parameters from beamstrahlung?(Stahl, White) Philip Burrows MDI Workshop, SLAC 6-8/01/05

  39. Observables/BeamParams List • Sigma x • Sigma y • Sigma z • Sigma x' • Sigma y' • E • E spread • x Offset • x' offset • y offset • y'' offset • x-waist shift • y-waist shift • Bunch rotation • N particles/bunch • Amount of y+y’ type-1 banana • Amount of y+y’ type-2 banana • Amount of y+y’ type-3 banana • E_tot • r moment • 1/r moment • Thrust Direction • Thrust Value • Angular Spread • E_out/E_in • L-R Asymmetry • T-B Asymmetry • Diagonal Asymmetry • N/E_tot • Forward + backward • calorimeters Each variable where appropriate exists for the mean of e- + e+ bunch and difference in obs/par between them. Philip Burrows MDI Workshop, SLAC 6-8/01/05

  40. Parameter Reconstruction • Compute Taylor matrices through multiple GP runs varying beam params-> use Grid computing at QM to do in finite time (have to stick to 2nd order calculations realistically). • For parameter reconstruction: Solve x for given f(x) using multi-parameter fit. Prob. no unique solution- choice of fit technique likely to be important. Philip Burrows MDI Workshop, SLAC 6-8/01/05

  41. Single-parameter analysis: sanity check Philip Burrows MDI Workshop, SLAC 6-8/01/05

  42. Initial results (Gaussian beams) (Stahl) Seems to be promising; MUCH more study needed … Philip Burrows MDI Workshop, SLAC 6-8/01/05

  43. Summary of collision optimisation/MDI issues • Active position stabilisation of final quads? • -> properly engineered design incl. laser tubes etc. • (through detector) • IP beam deflection feedback essential: intra-train and 5Hz • -> FB BPM, kicker, cables … need integrating into MDI design • -> understand background environment better • Crab cavity could be used for angle feedback? • -> needs integrating into real MDI design • Fast bunch-by-bunch lumi measurement vital input to FB • -> develop realistic prototypes of fast BSR/pair monitor • BSR/pair monitor offers potential for beam parameter determination • -> more simulation work needed • Need to develop integrated FB + scanning strategy: • -> intra-train + 5 Hz + dither + upstream slow + feedforward … Philip Burrows MDI Workshop, SLAC 6-8/01/05

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