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Position of the 3rd Harmonic System

Position of the 3rd Harmonic System. T. Limberg. Injector (with first Bunch Compression Stage). Injector Hall. XTIN: Length = 48m, accommodates Gun, ACC1, 3,9GHz, Laser Heater, Diagnostics, Dump Line. XSE: Length = 22.55m, accommodates Shielding, Dogleg. Start Linac Tunnel. Dogleg.

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Position of the 3rd Harmonic System

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  1. Position of the 3rd Harmonic System T. Limberg

  2. Injector (with first Bunch Compression Stage) European XFEL MAC May 2010 T. Limberg

  3. Injector Hall XTIN: Length = 48m, accommodates Gun, ACC1, 3,9GHz, Laser Heater, Diagnostics, Dump Line. XSE: Length = 22.55m, accommodates Shielding, Dogleg Start Linac Tunnel European XFEL MAC May 2010 T. Limberg

  4. Dogleg Phase Shifter Diagnostics Laser Heater Shielding BC0 Optical Restraints LH: - round and as stable as possible beam size required Diagnostics: - consists of TDS and 4 OTR screens - Optics at OTR screens is implemented by means of a 1.5 FODO cell with the phase advance of 76° - Fixed phase advance between TDS and OTR screens - Optics after LH is fixed. Entrance into the Diagnostics describes the boundary conditions for optics functions Shielding: - Concrete solid wall of 5.1m thickness with a spare place for the beam pipe. However two quadrupoles inside are needed to control the beta function. Dogleg: - Combination of two four cell arcs (8 cell system) - Provides a vertical displacement of the beam for a distance of 2,75m over the length of 20m. - First order momentum compaction r56 is zero. Phase Shifter: • Two 4m long FODO cells • Allows to adjust the phase advance by +-36° European XFEL MAC May 2010 T. Limberg

  5. LH DOGLEG BC0 After Chromatic Optimization Assumed: - ideal installation of the quadrupoles without any offsets. - Energy spread of the bunch is 2% RMS Results: • Emittance growth due to chromaticity effects over the first 80m is about 5-10% European XFEL MAC May 2010 T. Limberg

  6. BL.2 OTR UNDULATOR OTR BL.2 f=5,7° BL.1 BL.1 Off-crest acceleration in ACC1  energy spread of 2% at the moment the best possible ratio Laser Heater Length of the elements in LH Optics and beam parameters in the undulator European XFEL MAC May 2010 T. Limberg

  7. Avoid energy chirp in laser heater and dogleg: • Shift 3rd harmonic rf system downstream of dogleg • Provide chirp for compression with 3rd harmonic MAC Proposal European XFEL MAC January 2010 T. Limberg

  8. Compression System Overview European XFEL MAC January 2010 T. Limberg

  9. Relation between rf sum shape and amplitudes and phases of fundamental and harmonic rf systems (normalized to beam energy) European XFEL MAC January 2010 T. Limberg

  10. Running fundamental on crest • Control of third derivative (tail control) is lost • For given energy a1 in dogleg, energy p upstream of BC0 will vary for different working points (or otherwise) • Beam-based rf feedbacks might get simpler European XFEL MAC January 2010 T. Limberg

  11. First checks (0.1 nC case) look o.k. Longitudinal phase space Current Profile European XFEL MAC January 2010 T. Limberg

  12. Feedcap & endcap Knees for transfer line Tight installation (Very) rough estimate for extra kryo cost: 1 M€ Effort and cost: Kryo European XFEL MAC January 2010 T. Limberg

  13. Klystron will be installed underneath module LLRF system will be installed close to 3rd harmonic rf → no additional problems for these systems at the linac tunnel position RF and LLRF Issues European XFEL MAC January 2010 T. Limberg

  14. Plus: Relaxed conditions in dogleg and laser heater Might simplify beam-based rf feed-backs Minus: Reduced tunability of bunch compression system ~1 M€ extra cost Tight installation Independent and early commissioning not possible Summary for Shifting 3rd Harmonic rf and Running First Module on Crest European XFEL MAC January 2010 T. Limberg

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