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ATF2 optics, tuning method and tolerances of initial alignment, magnets, power supplies etc.

ATF2 optics, tuning method and tolerances of initial alignment, magnets, power supplies etc. Andrei Seryi for the ATF2 optics design team. Optics Design of ATF2. ATF2 design & goals. Learn to achieve:. Beam. (A) Small beam size Obtain s y ~ 35nm Maintain for long time

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ATF2 optics, tuning method and tolerances of initial alignment, magnets, power supplies etc.

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  1. ATF2 optics, tuning method and tolerances of initial alignment, magnets, power supplies etc. Andrei Seryi for the ATF2 optics design team

  2. Optics Design of ATF2 ATF2 design & goals.Learn to achieve: Beam (A) Small beam sizeObtain sy ~ 35nmMaintain for long time (B) Stabilization of beam center Down to < 2nm by nano-BPM Bunch-to-bunch feedback of ILC-like train PAC 05 paper:

  3. Emphasis on the optimal layout • Extend diagnostics section New final focus

  4. Emphasis on the optimal layout

  5. Optimal layout • Better optics • Allow extension of diagnostics section • about 13m of additional space is possible • Better location • Avoids many issue • Give more suitable schedule for the international partners to find their contribution

  6. Coupling Correction and Emittance Diagnostics for the ATF2 Extraction Line, Mark Woodley • ideally • correction section with 4 independent skew quadrupoles, followed by • 2D (4 wire scanner) emittance measurement section • optics for orthogonal control of the 4 coupling phases • minimize εy once with each skew quadrupole • in present ATF extraction line • non-optimal optics in EXT straight section • wire scanners and skew quads interspersed • each wire scanner has x, y, and “u/v” (small angle, ~10°) wires + provide space for various experiments Coupling Correction / Emittance Diagnostics ATF Extraction Line FONT Compton / laserwire ODR nBPM nBPM

  7. “Ideal” skew correction / ε diagnostic section SQ SQ SQ SQ WS WS WS WS – x – y 90° 90° 180° 90° 90° 90° 45° 45° 45° 45° 45° 45° See http://www.slac.stanford.edu/cgi-wrap/getdoc/slac-pub-8581.pdf

  8. Existing extraction line diagnostic section WS WS WS WS WS SQ SQ SQ SQ – x – y L = 11.43 m 5° 8° 13° 20° 30° 36°

  9. “Ideal” skew correction / ε diagnostic section for ATF2 Mark Woodley SQ SQ SQ SQ 1.2 1.2 1.7 1.7 1.1 1.3 1.1 0.9 0.9 0.9 0.7 1.3 1.1 WS WS WS WS WS – x – y 32° 48° 51° 21° 32° 58° 58° 32° L = 20.58 m ΔL ≈ 10 m σWS > 5 μ

  10. Tuning of ATF2 final focus • Procedure for ATF FF would be based on methods implemented at SLC FFS and FFTB, developed further • beam-based alignment using, e.g., shunting method • verify first order optics with trajectories fits • fix the phase advance between sextupoles • set sextupoles to minimize chromaticity • use global tuning correctors (knobs) to tune both the first-order and the nonlinear corrections using beam size measurements • Extensive simulations of tuning for GLC/NLC and TESLA, but not always all possible sources of errors were included • e.g. position errors included but not field strength, or vice versa • Simulations of the ATF2 tuning procedure started by UK colleagues, James Jones et al.

  11. Tuning of NLC BDS, Yuri Nosochkov, Aug. 2002 Errors:

  12. Analysis of Multipole and Position Tolerances for the ATF2 Final Focus LineJames Jones, ASTeC, Daresbury Laboratory • Analysed tolerances for all multipole components up to 20pole -> will be used to optimize magnet designs • Start analysis of position tolerances, including the effects of orbit correction and tuning knobs -> jitter and static position tolerances

  13. Field Tolerances – Individual Quads Multipole Errors • Tolerance for 10% beam growth due to the multipole field in an individual magnet, in units of • Multipoles from: • Order 10 (20 pole) : Red.. • Order 5 (10 pole): Light Green.. • Order 2 (Quad): Orange Normal Skew

  14. Position Tolerances – effect of individual magnets 2% Increase in beam size OR 2% change in position[beamsize] 2% Increase in beam size ONLY • Global tolerances are be determined considering the combined effect of all elements, including capabilities of correction methods • The global tolerances will need to match the goals A and B of ATF2 • 30% beam jitter for goal A and 10% (or a bit more?) beam size increase • for goal B, rely on intra-train feedback to reduce jitter, or aim to reduction of beam jitter to ~5% by providing better stability? Tolerance [mm-1] Tolerance [mm-1]

  15. Effect of all quads (jitter) • Look at the results without the final doublet as these have the tightest tolerances • More likely to be specially mounted and aligned • Quadrupoles only (2% change of IP position) • X-plane: 14.5nm • Y-plane: 0.87nm • Roll Angle: 6.9rad • If we aim for 30%, this scales to ~12nm in verticalthe goal of 5% would corresponds to ~2nm • Feasibility of the latter, especially, need to be determined

  16. Position Tolerances  with correction • Assuming that the correction system will maintain the beam at the correct position, and looking only on beam size increase: • Quadrupoles only (2% increase) • X-plane: 585 nm • Y-plane: 197 nm • Roll Angle: 1.48 rad • Start developing tuning knobs (x, y, x waist , y waist ) and orbit correction and include them into procedure (no coupling correction yet) • Quadrupoles only (2% increase) • X-plane: 16 mm • Y-plane: 141 nm • Roll Angle: 3.5 rad • Procedure, knobs, orbit corrections, is being further optimized  final tolerances will be then determined

  17. “Strategy for Commissioning the Beam” chapter of ATF2 proposal Frank Zimmermann’s questionnaire and some answers • Are all magnets on movers?  yes • Are there dipole steering correctors?  yes, several. Optimal locations TBD • How many BPMs and are they tightly attached to magnets  attached to all quads, sextupoles and bends • Are there beam loss monitors and current monitors (toroids)?  Yes. Location? • Are all magnets on individual power supplies?  Yes. • Do we have conventional wire scanners and/or screens/profile monitors?  Yes. Locations and how many? • What other existing diagnostics may be suitable for the commissioning?  • Does the various diagnostics, including BPMs, read out bunch by bunch or single bunch or integrated over a train? 

  18. Other minor optics improvements needed • To make the design more construct-able: • change bends from sector bends to rectangular • use 0.8m bens (as used in ATF) instead of 1m for better field stability and more space • space near octupoles is too tight  modify • QM14 is the strongest quad, and is close to max field of BT quads  reoptimize

  19. Summary • Between now and BDIR workshop the team will concentrate on the optimal layout + extended diagnostics optics, continue development of the tuning methods and finalize the numbers for tolerances

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