1. LCLS-II Capabilities & Overview LCLS-II Science Opportunities Workshop Tor Raubenheimer February 10 th, 2015

2. Outline LCLS-II Science Opportunities Workshop, February 9-13, 2015 1.Overall machine goals and layout 2.Primary parameters Nominal X-ray wavelength and pulse energy curves X-ray power Bunch charge versus X-ray length Timing and energy stability 3.Simulations of performance 4.Future enhancements Talk largely consists of slides extracted from recent LCLS-II reviews and much more information can be found there. 2

3. LCLS-II Concept CW linac based on SCRF technology to complement LCLS CuRF LCLS-II Science Opportunities Workshop, February 9-13, 2015 SCRF offers advantages in terms of X-ray power, stability, and repetition rate Challenge is cost for high energy CW accelerator and achieving comparable peak brighness LCLS-II will benefit from best of both CuRF and SCRF Use CuRF for high peak brightness at short wavelengths Use SCRF for very high average brightness (>10 26 @ 1 keV) with high stability and uniform bunch spacing 3

4. LCLS-II 1.3 GHz Cryomodule Similar to EuFEL but modified for CW operation Total length ~12.2 m Nearly the final LCLS-II cryomodule design LCLS-II Science Opportunities Workshop, February 9-13, 2015 Cryomodules will be similar to EuXFEL with modifications for CW operation; cavities will be processed for high Q0 operation Baseline 16 MV/m with Q 0 = 2.7x10 10 CM allows 150 Watts max cooling  20 MV/m max gradient @ 2.7x10 10 or 16 MV/m @ 1.8x10 10 4

5. LCLS-II Concept Use 1 st km of SLAC linac for CW SCRF linac 5 LCLS-II Science Opportunities Workshop, February 9-13, 2015 with space for 7 GeV

6. Revised LCLS-II (Phase II) Baseline Deliverables  Self seeding between 1.2-4 keV requires x-ray optics development  Self seeding at high rep rate above 4keV will require ~4.5 GeV electron beam, not a baseline deliverable today Cu Self Seeded High Rep Rate SASE Self Seeded (Grating) Cu SASE Photon Energy (keV) 0510152025 SC Linac High Rep Rate Cu Linac Legend 4.0 GeV LCLS-II Science Opportunities Workshop, February 9-13, 2015 6

7. LCLS-II Accelerator Layout New Superconducting Linac  LCLS Undulator Hall LCLS-II Science Opportunities Workshop, February 9-13, 2015 Two sources: high rate SCRF linac and 120 Hz Cu LCLS-I linac North and South undulators can operate simultaneously in any mode UndulatorSC Linac (up to 1 MHz)Cu Linac (up to 120Hz) North0.20 - 1.3 keV South1.0 - 5.0 keVup to 25 keV higher peak power pulses Concurrent operation of 1-5 keV and 5-25 keV is not possible 7

8. FEL X-ray Performance LCLS-II FAC Review, February 5-6, 2015 SCRF linac can deliver ~1 MHz beam to either undulator Undulators limited to 120 kW electron beam power 100 pC at 300 kHz and 4 GeV or 33 pC at 900 kHz and 4 GeV Goal is to provide >20 Watts in SASE over wavelength range of 0.2 to 5 keV to experiments with good mirror figure -X-ray Transport is designed to handle up to 200 Watts -Maximum X-ray pulse energy is function of X-ray wavelength, e.g. 0.9 mJ at 200 eV; 1 mJ at 1 keV; 20 uJ at 5 keV Soft X-ray self-seeding will provide narrower bandwidth with pulses a few times transform-limit CuRF linac will deliver LCLS-like bunches and mJ-scale SASE X-ray pulses to >25 keV 8

9. 9 Possible Operating Modes Very flexible operation ConfigurationLinac ParametersSXRHXR High rate to SXR and HXR SCRF: 4 GeV, 0.929 MHz; 60 pC CuRF: off 50-200 W at 1 keV (120-450 uJ at 460 kHz) 20 W at 3 keV (43 uJ at 460 kHz) High rate to SXR and medium pulse energy at HXR SCRF: 4 GeV, 0.240 MHz; 100 pC CuRF: off 80-200 W at 250 eV (350-900 uJ at 210 kHz) 20 W at 1.5 keV (1 mJ at 20 kHz) Medium rate and pulse energy at SXR and HXR SCRF: 4 GeV, 0.080 MHz; 100 pC CuRF: off 20 W at 500 eV (1 mJ at 20 kHz) 20 W at 4 keV (0.4 mJ at 50 kHz) High rate to SXR and high pulse energy at HXR SCRF: 4 GeV, 0.410 MHz; 100 pC CuRF: 15 GeV, 120 Hz, 130 pC 200 W at 250 eV (500 uJ at 400 kHz) 0.5 W at 3 keV (4 mJ at 120 Hz) High rate to SXR and short wavelength at HXR SCRF: 4 GeV, 0.929 MHz; 30 pC CuRF: 15 GeV, 120 Hz, 130 pC 50 - 200 W at 1.2 keV (50-200 uJ at 920 kHz) 0.1 W at 25 keV (500 uJ at 120 Hz) LCLS-II Science Opportunities Workshop, February 9-13, 2015

10. CuRF Linac Driven X-ray Pulse Energy LCLS-II Science Opportunities Workshop, February 9-13, 2015 H-D Nuhn 10

11. X-ray Pulse Energy from SXR and HXR driven by SCRF Analytic estimates vs. simulation results LCLS-II Science Opportunities Workshop, February 9-13, 2015 G. Marcus SC linac + SXR 100 pC, ~50 fs FWHM 300 kHz, 4 GeV SC linac + HXR 100 pC, ~50 fs FWHM 300 kHz, 4 GeV SXR 3  (approximate) HXR 3  (approximate) 20 pC e-beam 20 fs FWHM 20 pC e-beam 20 fs FWHM 11

12. 12 Example: 100 pC IMPACT, HXR SASE, E γ = 2 keV E max ~ 655 μJ P avg ~ 10 GW Δt = 58 fs P avg ~ 10 GW Δt = 58 fs

13. Example: 20 pC IMPACT, HXR SASE, E γ = 5 keV LCLS-II Science Opportunities Workshop, February 9-13, 2015 E NT ~ 8 μJ E T ~ 25 μJ E NT ~ 8 μJ E T ~ 25 μJ Δt ~ 18 fs ΔE γ,FWHM ~ 2.1 eV ΔE γ,FWHM /E 0 ~ 4.2 x 10 -4 ΔE γ,FWHM ~ 2.1 eV ΔE γ,FWHM /E 0 ~ 4.2 x 10 -4 13

14. Example: 100 pC IMPACT, SXR SS, E γ = 500 eV, LCLS-II Science Opportunities Workshop, February 9-13, 2015 E ~ 113 μJ after 9 downstream undulator sections Δt mean ~ 20 fs ΔE γ,FWHM ~ 0.22 eV ΔE γ,FWHM /E 0 ~ 4.4 x 10 -4 ΔE γ,FWHM ~ 0.22 eV ΔE γ,FWHM /E 0 ~ 4.4 x 10 -4 14 5 more undulator segments for post-saturation taper if desired Working to understand pedestal

15. Self-Seeding with LCLS, measurement and simulation LCLS-II Science Opportunities Workshop, February 9-13, 2015 S2E simulations ASTRA/ELEGANT/GENESIS Phenomenological and wave optics simulation of mono. Shows excellent overall agreement both in energy and in spectrum D. Ratner, S. Serkez Soft X-Ray Self-Seeding insert

16. Bunch Charge and Pulse Length SCRF charge and rate determined by 120 kW limit LCLS-II Science Opportunities Workshop, February 9-13, 2015 LCLS-II SCRF linac will deliver same beam parameters to both undulators -Specified to operate with 10 – 300 pC bunch charge @ <120 kW -100 pC with 60 fs FWHM; 20 pC with 20 fs FWHM Baseline is 100 pC per bunch with roughly 60 fs FWHM X-ray pulse length (1 kA) at 300 kHz (120 kW) -Working on techniques to shorten X-ray pulse without changing charge or chirp etc – how rapidly are changes desired? -Pulse energy simply proportional to pulse length Low charge options include 10 and 20 pC at up to 929 kHz -Better performance (pulse energy/bunch charge) 16

17. Nonlinear Harmonic Generation and Harmonic Lasing LCLS-II Science Opportunities Workshop, February 9-13, 2015 Nonlinear harmonic generation produces third harmonic radiation at ~1% of the fundamental when K>1.5 Harmonic lasing can produce significant radiation with a narrow spectrum when the fundamental is suppressed -Investigating options for harmonic lasing -Should be reasonable to upgrade HXR undulator if needed Fundamental2 keV3 keV Bunch charge100 pC20 pC 3 rd harmonic6 keV9 keV Efficiency1%0.75% Energy/pulse1 uJ0.14 uJ 17

18. Stability Goals LCLS-II Science Opportunities Workshop, February 9-13, 2015 LCLS-II SCRF FEL will be more stable than LCLS Baseline specs for electron beam: -  E/E < 0.01% rms -  I/I < 4% rms -  t < 20 fs rms -  X/  X,  Y/  Y < 15% rms LLRF has been specified to provide stability in ‘worst’ case of correlated errors X-ray pulse has added intensity jitter from SASE and optics MHz beam rate should allow further stabilization with addition of fast feedback systems 18

19. Longer-Term Goals Can Provide Exceptional Stability LCLS-II Science Opportunities Workshop, February 9-13, 2015 ENERGY PEAKCURRENT ARRIVALTIME Now simulate the best case: 0.01% and 0.01 deg rms jitter and all uncorrelated Energy stable to 0.003% rms Peak current stable to 1.8% Timing stable to 5 fs * The gun timing error is compressed by 3.85 from gun to 100 MeV, due to velocity compression. Best Case Jitter Simulations in LiTrack P. Emma 19

20. LCLS-II Planned Undulator Layout Replace Existing LCLS Undulator with HXR and add SXR 32 HXU Segments Existing Diamond Crystal Self-Seeding System New SXR Self-Seeding System for High Power Loads 21 SXU Segments Space for future upgrades? Space for polarization upgrade? Considering vertical polarization of X-rays from HXR line LCLS-II Science Opportunities Workshop, February 9-13, 2015

21. Delta Undulator for Polarization Control installed on U33 21 LCLS-II Science Opportunities Workshop, February 9-13, 2015

22. Option for complete HXR self-seeding monochromator Possible layout options not fully explored Two-stage diamond wake-field monochromator seeding sections and a grating monochromator seeding section Seeding below 3 keV Both diamond systems are retracted Seeding above 3 keV Grating system is retracted Between 3 – 5 keV Both diamond monochromators in use using (111) crystals Above 5 keV with CuRF linac Only 2 nd diamond mono. in use with (400) crystal LCLS-II Science Opportunities Workshop, February 9-13, 2015 22

23. Enhanced Modes of operation (G. Marcus, July 31, LCLS-II Parameters Review) High rep-rate HXR SS External seeding HGHG EEHG ?SASE iSASE pSASE Harmonic Lasing Two-Color Split undulator and gain modulation Two-bunches FWM via selective amplification Short pulses low charge, beam spoiling, laser modulation, self-seeding / chirp Timing control Defined by laser Easy to adjust pulse duration Improved stability in photon energy and # Possibly near transform limited pulses Increase cooperation length Narrow spectrum Extend tuning range of FEL beamline X-ray pump & probe Four-wave mixing LCLS-II Science Opportunities Workshop, February 9-13, 2015

24. Summary LCLS-II Science Opportunities Workshop, February 9-13, 2015 Broad capability -High rate beam from 0.20 – 5 keV with >20 W X-ray power -High intensity pulses with LCLS-like characteristics to >25 keV SCRF linac will provide >10x better stability than CuRF -How best to take advantage of benefits? -What else is needed? Variable gap udulators allow flexible operation -Broad bandwidth coverage; Strong tapering; Rapid wavelength scans Broad spectrum of upgrade options -LCLS is pioneering many techniques that may be implemented in LCLS-II Please specify your X-ray goals -Opportunity to modify development plans but need strong science case 24

25. BACKUP LCLS-II Science Opportunities Workshop, February 9-13, 2015

26. LCLS-II versus LCLS performance at 120 Hz (LCLS-II Performance between 1 and 25 keV) HXR provides much shorter photon wavelength with comparable pulse energy H-D Nuhn, Y. Ding, G. Marcus, J. Wu Analytic calculations verified with S-2-E modeling 26 LCLS-II Science Opportunities Workshop, February 9-13, 2015

27. Baseline High Rate FEL Tuning Range (HXR between 1 and 5 keV; SXR between 0.2 and 1.3 keV) H-D Nuhn, Y. Ding, G. Marcus, J. Wu Analytic calculations verified with S-2-E modeling Normal operation at 4 GeV covers photon range of primary interest 2 GeV operation included for BBA 27 LCLS-II Science Opportunities Workshop, February 9-13, 2015

28. Upgrade Possibility: Superconducting Undulators Greater photon energy reach and high photon pulse power LCLS-II Science Opportunities Workshop, February 9-13, 2015 LCLS-II SCU Nb 3 Sn PMU In-Vac. PMU NbTi Superconducting undulators offer promise of high field at short period  higher E ph LCLS HXR SCU also could enable TW XFEL using CuRF linac