clic and xfel study group@sinap

1. clic and xfel study group@sinap MengZhang, Chao Feng, QiangGu

2. Preliminary work on the XFEL • Recent progress • FEL parameters • 1D tracking using litrack • Future plans

3. FEL parameters – the baseline • Achievable normalized emittance is used for few hundred pCbeam. • A permanent magnet in-vacuum undulator with 15mm period is used for the radiator • The radiator length is less than 80m with the PMU and could be shorter with the cryo-PMU

4. 3D gain length optimization Peak current Emittance E=2GeV Energy spread Undulator period

5. Hard x-ray beam line • By changing the e-beam energy and using two beam lines with different period PMUs, the fully tunable hard x-ray could be achieved at the same time. E=6GeV E=4GeV

6. Soft x-ray beam line • By changing the e-beam energy and using two beam lines with different period PMUs, the 1nm – 4nm soft x-ray could be achieved at the same time. • Longer wavelength is limited by the extracting energy from the main linac. E=2GeV

7. 1D tracking – schematic layout

8. Baseline configuration • Compressing ratio = 12*8 • Double horn at the current profile and the none linear chirp at the energy profile are due to the x band linearizer and the wake from the TWS After BC1 Injector exit Before BC1 Before BC2 After BC2 Linac exit

9. Jitter budget for the baseline • Tolerance budget is quite critical for this baseline configuration, especially for the x band systems • Linacbaseline should be optimized on the view of system stability

10. Lower charge case • Lower charge and shorter length case could be achieved using the baseline configuration • Energy chirp is hard to be compensated by the TWS. The dechirper would be used. 100pC 20pC

11. Future plans - 1D • FEL • Detailed study on the radiator parameters optimization • Extraction energy for the soft x-ray beamline • The jitter requirement • Linac • Optimization on the jitter budget with different two stage compressing parameters by MOO method • 1D tracking for the soft x-ray case and the jitter budge study • Optimization of the operation modes with different charge and bunch length

12. MOO method example • Multi-objects f(1) = std(dE_E0(:,8)); % energy spread f(2) = std(zpos0(:,8))-7e-6; % 7um bunch length f(3) =E_barcuts0(end)-6; % 6GeV mean energy

13. Thanks for your attentionQuestions and comments please

14. Key requirements at the experiment station • Resolution • Longitudinal: time and energy • Higher time resolution -> shorter pulse • Higher energy resolution -> longer pulse, coherence along the pulse • Transverse: emittance • Power • Single short • Average power • Timing between FEL and user instrumentations • Wavelength • Shortest wavelength • Tunability

15. Key requirements on the XFEL • Operating scheme • Longitudinal coherence • Hard X-ray: SASE(incoherence), pSASE, self-seeding • Soft X-ray: pSASE, self-seeding, seeded scheme (EEHG, HGHG, cooled-HGHG) and their cascaded combinations • Transverse coherence: OK! • Power • ~E-beam power * pierce parameter • Stability • Wavelength • E-beam energy, the field and period of the undulator • Tunability of the Hard X-ray and Soft X-ray beamline

16. Key requirements on the e-beam • Emittance • Transverse • Initial emittance from the source • Conservation • Longitudinal • Low uncorrelated energy spread < pierce parameter • Stability • peak current • Energy jitter < pierce parameter • Timing jitter between the seeding laser and e-beam (important for seeded scheme • Power • Energy, current (charge and bunch length) • Flexibility • Bunch length: long bunch length -> high order energy chirp correction; short bunch length -> energy chirp compensation • Current: low current -> low pierce parameter; high current -> energy chirp compensation, wakefield