1 / 18

LCLS-II Transverse Tolerances

LCLS-II Transverse Tolerances. Tor Raubenheimer May 29, 2013. LCLS-II Accelerator Parameters. Tolerance Specifications. Transverse tolerances to minimize emittance dilution, optical errors and beam jitter

quilla
Télécharger la présentation

LCLS-II Transverse Tolerances

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. LCLS-II Transverse Tolerances Tor Raubenheimer May 29, 2013

  2. LCLS-II Accelerator Parameters

  3. Tolerance Specifications • Transverse tolerances to minimize emittance dilution, optical errors and beam jitter • Tolerances based on most stringent conditions – usually 10 pC with 0.17 mm-mrad emittance and over-compression with 0.5% DE/E • Sources include alignment errors, magnet harmonics, PS fluctuations, component vibration, and coupling from other sources • Jitter tolerances set to limit beam motion to 33% rms in undulator from all sources • All tolerance specifications are rms values • Full tuning / bump studies not completed

  4. Transverse Jitter Sources • Based on ge = 0.15 mm-mrad, N = 250 pC, sE/E = 0.5% and D/s<33% (DI/I = 15%)

  5. Comparison with LCLS-I Tolerances • LCLS-I quad jitter tolerances were specified to limit the beam expected amplitude to 10% of the rms beam size. • The amplitude is sqrt(2) larger than the rms offset • LCLS-II tol. are specified for 33% rms jitter from all sources • Although not specified, it looks like LCLS-I tolerances were specified for 1 mm-mrad versus 0.17 mm-mrad for LCLS-II LCLS-II total jitter budget is ~2x looser • Quadrupoles are small fraction of jitter budget  quadrupole jitter requirements are 1.7x tighter

  6. Current and Energy Jitter  Transverse • Beam current jitter couples to transverse jitter through transverse wakefields and CSR • Beam energy jitter couples to the transverse jitter through residual dispersion, coupling to wakefields in dispersive regions and changes in phase advance CSR Cancellation Septum kick for 250 pC, 3 kA Longitudinal Wakes for 250 pC, 3 kA

  7. Steering Correctors • Largest potential source of beam jitter at ~20% DX,Y/sX,Y • MCOR power supplies limited to ~1e-4 DI/I • LCLS-I specified 3e-5 toelrances for many dipole correctors • Sizes of MCORs reduced to balance corrector strength to reasonable values  ease tolerances • Used ‘reasonable’ maximum quadrupole alignment errors and compared to typical LCLS-I corrector strengths

  8. Steering Correctors (2) L1 / L2 values are < 10 G-mL3 values < 20 G-m BC2 values large

  9. Steering Correctors (3) • Maximum quadrupole misalignments for corrector sizing

  10. Steering Correctors (4) • Most correctors could correct a local large misalignment • In some cases, multiple (2) correctors will be required

  11. Steering Correctors (5) • Not showing Tables – look in PRD! • Most correctorsmuch weaker thanin LCLS-I specsbut similar to LCLS-I operatingvalues • L1 / L2 / L3 correctors are all much weaker thanSLAC linac • LTU sized at 60 G-m and dump correctors are 120 G-m

  12. Dipole Magnets (1) • Achromatic magnet strings should be largely insensitive to power supply fluctuations • In practice, magnets are only matched at 1% level and include +/- 1% trims to match magnets • Power supply regulation tolerances calculated to limit (1) change in path length, (2) transverse trajectory in achromat, and (3) transverse jitter due to 1% magnet mismatch • Dipole string PS are medium PS with 5e-5 regulation • Trim power supplies are standard MCORs with 2e-4 regulation

  13. Dipole Magnets (2) • Roll jitter tolerances vary between 1 and 10 urad • Dipole roll jitter is 2nd largest DY/sY jitter source • Roll alignment tolerance is set to limit dispersion errors and trajectory • Dipole roll alignment tolerances vary between 0.3 and 5 mrad • These may be overly tight and can iterate as needed

  14. Quadrupole Magnets (1) • Quadrupole vibration tolerances are the 3rd most important source of beam motion • Typical values vary between 100 and 50 nm • Quadrupole alignment set loosely by increase in projected beam sizes • Typical values rangebewteen 300 and 100 um • Without bumpsDe/e ~ 500%

  15. Quadrupole Magnets (2) • Quadrupole vibration tolerances tight in BC1, BC2, Bypass extraction and LTU – typical jitter contributions <1% magnet • May want to work on S20 quadrupole supports Vibration Tolerance [um] LTU BC1 BC2 S20 and Bypass extraction

  16. Quadrupole Magnets (3) • Quadrupole power supply regulation tolerances are calculated to minimize (1) Db/b, (2) Dh*sE/E, and (3) jitter due to trajectory errors: 3e-5 DI/I minimum tolerance • For jitter calculation assumed quadrupole center-to-trajectory of 100 um in BC2, Bypass ext. & Undulator; 200 um in BC1 & LTU; 1000 um in Bypass; 300 um elsewhere LTU Arc Bypass extraction

  17. Transverse TolerancesAlignment Tolerances • Alignment numbers provide guidance  beam-based tuning • Slice e impact is small(slice = 1% of sZ) • Projected e impact is large • Calculated for over-compressed case with 0.5% DE/E • Alignment: 300 um on rf structures and most quadrupoles; 200 um in BC1 and LTU; 100 um in BC2, Bypass and Undulator • X-band structure transverse wake is 40x larger than S-band yielding 30% projected De/e growth by itself (slice De/e are ~2%)

  18. Magnet Field Tolerances • Detailed magnet tables for all dipoles, quadrupoles and steering correctors • Multipole tolerances calculated using 250 pC (0.5 mm-mrad) over-compressed beam (0.5% DE/E) plus steering errors of 0.5 mm except 1 mm in injector, bypass and undulator • Multipole tolerances are relatively loose except where there is dispersion • Uncorrelated effect on beam core is small <5% De/e and<0.1% DK/K Partial table for SXR LTU quads

More Related