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

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

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

4. Position of the 3rd Harmonic System Optical Restraints 4 European XFEL MAC May 2010 T. Limberg Laser Heater Diagnostics Shielding Dogleg BC0Phase Shifter 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°

5. Position of the 3rd Harmonic System After Chromatic Optimization 5 European XFEL MAC May 2010 T. Limberg 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% LHBC0 DOGLEG

6. Position of the 3rd Harmonic System Laser Heater 6 European XFEL MAC May 2010 T. Limberg HorizontalVertical , m 4.6518.33  1.6-2.6 D, m0.030 ,  m 615271 Off-crest acceleration in ACC1  energy spread of 2% at the moment the best possible ratio Length, mm BL.1200 BL.2200 OTR, BPM300 UNDULATOR800 Total2600 Optics and beam parameters in the undulator Length of the elements in LH BL.1 BL.2 BL.1 OTR UNDULATOR 

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

8. Position of the 3rd Harmonic System Compression System Overview 8 European XFEL MAC January 2010 T. Limberg

9. Position of the 3rd Harmonic System Relation between rf sum shape and amplitudes and phases of fundamental and harmonic rf systems (normalized to beam energy) 9 European XFEL MAC January 2010 T. Limberg

10. Position of the 3rd Harmonic System Running fundamental on crest 10 European XFEL MAC January 2010 T. Limberg Control of third derivative (tail control) is lost For given energy a 1 in dogleg, energy p upstream of BC0 will vary for different working points (or otherwise) Beam-based rf feedbacks might get simpler

11. Position of the 3rd Harmonic System First checks (0.1 nC case) look o.k. 11 European XFEL MAC January 2010 T. Limberg Longitudinal phase space Current Profile

12. Position of the 3rd Harmonic System Effort and cost: Kryo Feedcap & endcap Knees for transfer line Tight installation (Very) rough estimate for extra kryo cost: 1 M€ 12 European XFEL MAC January 2010 T. Limberg

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

14. Position of the 3rd Harmonic System Summary for Shifting 3 rd Harmonic rf and Running First Module on Crest 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 14 European XFEL MAC January 2010 T. Limberg