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Alternate Lattice for LCLS-II LTU Y. Nosochkov LCLS-II Physics M eeting, March 21, 2012

Alternate Lattice for LCLS-II LTU Y. Nosochkov LCLS-II Physics M eeting, March 21, 2012. Goals.

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Alternate Lattice for LCLS-II LTU Y. Nosochkov LCLS-II Physics M eeting, March 21, 2012

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  1. Alternate Lattice for LCLS-II LTUY. NosochkovLCLS-II Physics Meeting, March 21, 2012

  2. Goals • The original LTU vertical separation scheme does not cancel the vertical dispersion resulting in several cm leaking dispersion downstream of the SXR LTU  Cancel dispersion by modifying the separation scheme and the optics • Several LTU magnets interfere with the LTU wall and LCLS-I  Reduce interference by changing magnet positions • Keep the number of magnets within the present budget Y. Nosochkov

  3. Original lattice HXR Undulator LTU Linac Bypass gun sd sd sd   sd  L0   µ 11-1 sd sz sd L1 L3 L2 sz sz  BC1 BC2 11-3 to 14-4 DL1 sd 14-7 to 20-4 DL2 HXR SXR sd Y. Nosochkov

  4. Original LTU HXR 2.4o 4-bend 4 wires, 4 collimators 45o FODO SXR -1.2o 2.4o 4-bend 1.2o 3 wires, 4 collimators Septum Y. Nosochkov

  5. Original vertical separation scheme Kicker strength = 0.07 kGm at 15 GeV P. Emma Y. Nosochkov

  6. Lambertson septum in the original scheme P. Emma Y. Nosochkov

  7. Kicker vertical dispersion is not canceled Y-orbit bump Y-dispersion in the LTUS Y-dispersion in LTUS through dump Y. Nosochkov

  8. Canceling the kicker dispersion • Dispersion correction cannot be delayed because of the downstream SXR diagnostic section. • Using 2 more correctors (2nd kicker + 3rd DC bend) results in large Y-orbit in quads (up to 20 mm) and large corrector strengths (up to 2.7 kGm). This is in part due to small vertical phase advance in the LTU triplet optics. septum Large orbit when Y-dispersion is canceled with 2 kickers and 3 DC bends • Various options were tried: adding quads to the triplet system, using 2 bumps (180° apart), FODO cells, doublet cells, horizontal separation. • The selected option: 1) Doublet DF-FD cells, 2) horizontal beam separation, 3) two 1.2° bends instead of four 0.6° bends (more free space and fewer quads), 4) SXR diagnostic with 90° FODO cells (fewer quads as compared to 45° cells). • Disadvantages: a little higher synchrotron radiation effect due to stronger bends, fixed R56 in the 2.4° arc (but an additional tuning chicane could provide adjustment). Y. Nosochkov

  9. Replace LTU triplet cells with DF-FD cells matched to 180o x-phase between bends. • Replace 4x0.6o bends with 2x1.2o bends for fewer arc quads and larger quad spacing. • Use horizontal separation, include the kicker orbit into the SXR reference trajectory. Y-kicker DC2 DC1 septum 2.4o 4-bend 1.2o 2-bend Original SXR LTU Long drift to maximize HXR/SXR separation Long drift to minimize wall interference X-kicker DC1 DC2 septum 2.4o 2-bend 1.2o 2-bend Alternate SXR LTU Low bx at bends Y. Nosochkov Kicker strength = 0.17 kGm at 15 GeV and Dx=-10mm

  10. Kicker orbit septum BX42 QDL43 QDL45 QDL46 QDL44 kicker X = -10 mm at septum Off-axis through QDL44,45,46 and BX42 Y. Nosochkov

  11. First look at the current sheet septum design for horizontal separation (C. Spencer) SXR HXR Assume 10 mm beam-to-beam separation, B=2.6 kG, L=2 m. Some HXR correction will be required to compensate for residual field. Y. Nosochkov

  12. Geometry: original 4-bend arc versus alternate 2-bend arc 19.6 cm Wall Original: some magnets interfere with the wall Alternate: only beam pipe interferes with the wall Y. Nosochkov

  13. SXR diagnostic and 2nd dogleg bend pair triplets 120ob-waist diagnostic Original w w cx,cy cx,cy w 2x90o FODO 90o FODO diagnostic Alternate cy cx cx cy w w w w Y. Nosochkov

  14. Normalized beam X-phase space at LTUS wires • Wire phase separation: • mx : 65°-25°-65° • x= 14 m • ax= ±1.43 Wire-1 Wire-4 Wire-3 Wire-2 Y. Nosochkov

  15. Normalized beam Y-phase space at LTUS wires • Wire phase separation: • my: 25°-65°-25° • y= 14 m • ay= ±1.43 Wire-4 Wire-3 Wire-1 Wire-2 Y. Nosochkov

  16. SXR dogleg geometry: original versus alternate 19.3 cm Y. Nosochkov

  17. Complete alternate LTU lattice 2.4° HXR 45° FODO diagnostic 2.4° 1.2° -1.2° SXR 90° FODO diagnostic Septum Y. Nosochkov

  18. Complete alternate LTU geometry Red -- bends, blue -- quads, green -- x-kicker, septum, DC bend V-bend HXR Panofsky septum SXR Panofsky Panofsky 1st Panofsky quad separation: 237 mm Downstream of the LTU the HXR/SXR geometry is matched to the original geometry Y. Nosochkov

  19. LTU wall: original lattice Interference: 3 quads + 2 bends + kicker Wall Y. Nosochkov

  20. LTU wall: alternate lattice End of wall No magnets Wall Magnets are placed outside of the wall interference region. Y. Nosochkov

  21. LTU parameters • LTU region is from muon wall to HSSSTART/SSSSTART. • Tunable R56 in the original 4-bend arc. • Non-tunable R56 in the 2-bend arc  Tuning could be achieved with an additional tuning chicane. DgeISR = 4∙10-8 ∙ I5 ∙ E6= 0.002 mm-radat I5 = 4.1e-9 and 15 GeV Y. Nosochkov

  22. Chicane option for R56 tuning J LB LBB Example: LBB = 2 m, LB = 1.5 m, DR56 = -1.004 mm  J = 12.94 mrad, B = 4.31 kG at 15 GeV Y. Nosochkov

  23. Back-up slides Y. Nosochkov

  24. Un-normalized beam X-phase space at LTUS wires Y. Nosochkov

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