LCLS-II Capabilities & Overview LCLS-II Science Opportunities Workshop. Tor Raubenheimer (P. Emma) February 9 th, 2015

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1 LCLS-II Capabilities & Overview LCLS-II Science Opportunities Workshop Tor Raubenheimer (P. Emma) February 9 th, 2015

2 Outline 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 pulse 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

LCLS-II Concept CW linac based on SCRF technology to complement LCLS CuRF SCRF offers advantages in X-ray power, stability, and rep-rate Cost is the issue for a high energy, CW accelerator and

3 LCLS-II Concept CW linac based on SCRF technology to complement LCLS CuRF SCRF offers advantages in X-ray power, stability, and rep-rate Cost is the issue for a high energy, CW accelerator and achieving comparable peak brightness LCLS-II will benefit from best of both CuRF and SCRF Use CuRF for high peak brightness at short wavelengths Use SCRF for high average brightness with stable beam and uniform pulse spacing 3

LCLS-II 1.3 GHz Cryomodule (CM) Similar to EuFEL but modified for CW* 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.

4 LCLS-II 1.3 GHz Cryomodule (CM) Similar to EuFEL but modified for CW* operation Baseline 16 MV/m with Q 0 = 2.7x10 10 CM allows 150 Watts max cooling 20 MV/m max 2.7x10 10 or x10 10 * Continuous Wave = RF is always ON Total length ~12.2 m Nearly final LCLS-II cryomodule design CM s are similar to EuXFEL with modifications for CW operation; cavities will be processed for high Q 0 operation 4

5 LCLS-II Concept Use 1 st km of SLAC linac for CW SCRF linac with space for 7 GeV 5

6 Revised LCLS-II (Phase II) Baseline Deliverables Cu Linac SC Linac High Rep Rate 4.0 GeV Photon Energy (kev) Legend Cu SASE Cu Self Seeded High Rep Rate SASE Self Seeded (Grating) Self seeding between 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 6

LCLS-II Accelerator Layout New Superconducting Linac LCLS Undulator Hall Two e - sources: high-rate SCRF linac and 120-Hz Cu LCLS-I linac North and South undulators: can operate simultaneously in any

7 LCLS-II Accelerator Layout New Superconducting Linac LCLS Undulator Hall Two e - sources: high-rate SCRF linac and 120-Hz Cu LCLS-I linac North and South undulators: can operate simultaneously in any mode Undulator SC Linac ( 1 MHz) Cu Linac (up to 120Hz) North (SXR) kev South (HXR) kev up to 25 kev higher peak power pulses Concurrent operation of 1-5 kev & 1-25 kev not possible (same und.) LCLS-II Linac SCRF proposed FACET-II Sec LCLS-I Linac GeV Sec kev (0-1 MHz) 4 GeV 1-25 kev (120 Hz) 1-5 kev (0-1 MHz) SXU HXU 7

8 FEL X-ray Performance SCRF linac can deliver ~1 MHz beam to either undulator Each undulator limited to 120 kw electron beam power 100 pc at 300 khz or 30 pc at 929 khz (4 GeV) Goal to provide > 20-W SASE power over wavelength range of 0.2 to 5 kev to experiments with good mirror figure - X-ray Transport 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 (120 Hz) LCLS-II FAC Review, February 5-6,

9 Possible Operating Modes (flexible operation) Configuration Linac Parameters (<120 kw) SXR HXR High rate to SXR & HXR SCRF: 4 GeV, 0.93 MHz; 60 pc CuRF: off W at 1 kev ( uj at 460 khz) 20 W at 3 kev (43 uj at 460 khz) High rate to SXR & medium HXR pulse energy SCRF: 4 GeV, MHz; 100 pc CuRF: off W at 250 ev ( 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, 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, 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, 0.93 MHz; 30 pc CuRF: 15 GeV, 120 Hz, 130 pc W at 1.2 kev ( uj at 920 khz) 0.1 W at 25 kev (500 uj at 120 Hz) 9

10 CuRF-Linac-Driven X-ray Pulse Energy (in HXR) H-D Nuhn 10

11 Energy/pulse (J) X-ray Pulse Energy from SXR and HXR driven by SCRF Analytic estimates (curves) vs. simulation results (stars) SC-linac + SXR 100 pc, ~50 fs FWHM 300 khz, 4 GeV SC-linac + HXR 100 pc, ~50 fs FWHM 300 khz, 4 GeV 20 pc e-beam 20 fs FWHM 10-5 SXR 3w (approximate) HXR 3w (approximate) Photon Energy (ev) G. Marcus 11

Example: 100 pc IMPACT, HXR SASE, E γ = 2 kev Uses tracked particles through accelerator 10 4 2 kev, energy [ J] 40 P avg ~ 10 GW Δt = 58 fs

12 Example: 100 pc IMPACT, HXR SASE, E γ = 2 kev Uses tracked particles through accelerator kev, energy [ J] 40 P avg ~ 10 GW Δt = 58 fs E max ~ 655 μj E [ J] 10 0 P [GW] 20 2 I [ka] z [m] s [ m] 12

13 Example: 20 pc IMPACT, HXR SASE, E γ = 5 kev Uses tracked particles through accelerator E [ J] No taper Taper E NT ~ 8 μj E T ~ 25 μj P [GW] Δt ~ 18 fs s [ m] I [ka] x z [m] P(w) [a.u.] ΔE γ,fwhm ~ 2.1 ev E [ev] 13

Example: 100 pc IMPACT, SXR Self-Seeded, E γ = 500 ev 10 10 2 E ~ 113 μj after 9 downstream

s [ m] 10-2 10-4 0 20 40 60 80 z [m] 5 more undulator segments for post-saturation taper if

14 Example: 100 pc IMPACT, SXR Self-Seeded, E γ = 500 ev E ~ 113 μj after 9 downstream undulator sections monochromator P [GW] 8 Δt mean ~ 20 fs E [ J] s [ m] z [m] 5 more undulator segments for post-saturation taper if desired # /ev 6 x ΔE γ,fwhm 0.22 ev E [ev] Working to understand pedestal 14

15 Bunch Charge and Pulse Length (charge and rate determined by 120-kW dump limit) LCLS-II will deliver same beam parameters to both undulators - Specified to operate with pc bunch 120 kw 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/fel (120 kw) - Working on techniques to shorten X-ray pulse without changing charge or chirp etc how rapidly are changes desired? - Pulse energy is proportional to pulse length Low charge options include 10 and 20 pc at up to 929 khz - Better beam quality, shorter pulses, reduced pulse energy 15

16 Nonlinear Harmonic Generation and Harmonic Lasing Nonlinear harmonic generation produces third harmonic radiation at ~1% flux of fundamental when K > 1.5 HXR Fundamental 2 kev 3 kev Bunch charge 100 pc 20 pc 3 rd harmonic 6 kev 9 kev Efficiency 1% 0.5% Energy/pulse 1 uj 0.5 uj Harmonic lasing can produce significant radiation with a narrow spectrum when fundamental is suppressed - Investigating options for harmonic lasing - Might need to modify HXR undulator 16

17 Stability Goals LCLS-II SCRF FEL will be more stable than LCLS-I Baseline specs for electron beam: DE/E < 0.01% rms (photon is 0.02%) DI/I < 4% rms (FEL power ~2%) Dt < 20 fs rms DX/s X, DY/s Y < 15% rms e - energy (<0.01%) LLRF specified to provide stability in worst case of correlated errors (from RF amplifier to amplifier) X-ray pulse has added intensity jitter from SASE and optics MHz beam rate should allow further stabilization with fast feedback systems 17

Best Case Jitter Simulations in LiTrack Simulate best case: 0.01% and 0.

18 See PRD: LCLSII-2.4-PR-0041 Longer-Term Goals Can Provide Exceptional Stability ENERGY Best Case Jitter Simulations in LiTrack Simulate best case: 0.01% and 0.01 deg rms RF jitter and uncorrelated Energy stable to 0.003% rms Peak current stable to 1.8% Timing stable to 5 fs Possible outcome not spec. ARRIVAL TIME PEAK CURRENT * The gun timing error is compressed by 3.85 from gun to 100 MeV, due to velocity compression. P. Emma 18

Existing Diamond Crystal Self-Seeding System Space for polarization upgrade?

19 LCLS-II Undulator Layout Replace Existing LCLS Undulator with HXR and add SXR (adj. gap) 21 SXU Segments 32 HXU Segments Space for upgrades? Existing Diamond Crystal Self-Seeding System Space for polarization upgrade? Considering vertical polarization of X-rays from HXR line New SXR Self-Seeding for High Power (in baseline)

20 Enhanced Modes of operation (G. Marcus, July 31, LCLS-II Parameters Review) High rep-rate HXRSS External seeding SXR HGHG EEHG Modified SASE Timing control Defined by laser Easy to adjust pulse duration Improved stability in photon energy and # Possibly near transform limited pulses isase psase Harmonic Lasing Two-Color Increase cooperation length Narrow spectrum (~ 1/10) Extend tuning range of FEL beamline Split undulator and gain modulation Two-bunches FWM via selective amplification Short pulses X-ray pump & probe Four-wave mixing low charge, beam spoiling, laser modulation, self-seeding / chirp

21 Upgrade Possibility: Superconducting Undulators (greater photon energy reach - more efficient FEL) LCLS-II SCU Superconducting undulators offer promise of higher field at short period higher E ph LCLS HXR (1 T) Allows reach to 7 kev Enables TW-XFEL using CuRF linac Extensive R&D needed Vacuum gap 5 mm Photon energy 4 kev e - energy 6.6 GeV Emittance 0.4 m Peak current 4 ka

22 Summary Broad capability - High rate beam from kev with > 20-W avg. X-ray power - High intensity pulses with LCLS 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 undulators allow flexible operation - Broad bandwidth coverage; Strong tapering; Rapid wavelength scans Broad list of upgrade options - LCLS is pioneering many techniques that may be implemented in LCLS-II Please suggest your X-ray goals - Opportunity to modify development plans but need strong science case 22

23 BACKUP

10 torr - Differential pumping w/ 1st variable (impedance)

24 Must Use Gas Based Techniques for SXR Design concept similar to LCLS-I gas attenuator, but - Using Ar gas, 5 m long volume, up to 10 torr - Differential pumping w/ 1st variable (impedance) apertures to reduce conductance (beam size ~ 10 mm at 200 ev at location)

25 Impact of Intensity Fluctuations on Gas Attenuator Beam drills hole through gas Operating pressure ~ 2.5 torr, effective attenuation 5x10-4 ~ absorbed 200 W into gas detector T (K) Attn Achieved Intensity fluctuation induced inaccuracy in attenuation ~ 10% Intensity fluctuation induced baseline temperature variation ~ 200 K Y. Feng

26 See LCLSII-1.1-PR-0133 LCLS-II (SCRF) Baseline Parameters Parameter symbol nominal range units Electron Energy E f GeV Bunch Charge Q b pc Bunch Repetition Rate in Linac f b MHz Average e - current in linac I avg ma Avg. e - beam power at linac end P av MW Norm. rms slice emittance at undulator e -s m Final peak current (at undulator) I pk A Final slice E-spread (rms, w/heater) s Es kev Final bunch length (rms) t b m Avg. CW RF gradient (powered cavities) E acc 16 - MV/m Photon pulse length (FWHM) t xray fs Photon energy range of SXR (SCRF) E phot kev Photon energy range of HXR (SCRF) E phot kev Photon energy range of HXR (Cu-RF) E phot kev

27 External seeding modes EEHG mod1 mod2 radiator 16 fs rms 0.12 ev rms 9 fs rms 0.22 ev rms UV seeds ~ 2 x transform limit Allows long coherent pulses Highly sensitive to laser quality, less so to electron bunch HGHG mod1 rad1 mod2 rad2 Highly sensitive to electron bunch parameters Consistently poor spectrum QHG (with reviewers) relax conditions on harmonic jumps UV seed fresh bunch delay

28 External seeding performance and requirements EEHG Performance - Long, coherent pulses - Near Fourier transform limit (~ 2x 1nm) Requirements - Stable (amplitude and phase) 260 nm - 2 chicanes and 2 modulators HGHG Performance - Best for short pulses - Hard to control spectrum - Below 2 nm is pushing limits Requirements - 3 chicanes (one for fresh bunch), 2 modulators, intermediate radiator nm laser

29 Harmonic lasing using 100 pc, 1 ka e-beam slice properties fund. Ideal beam comparison 5 3 rd harm kev 6-7 kev photons become possible with attenuators P [W] Additional phase shifters needed z [m] HXR P [W] z [m] Tune first undulators such that 3 rd harmonic at desired wavelength Tune second undulators such that 5 th harmonic is at desired wavelength and equal to 3 rd upstream P [W] kev 4.1 kev 0.83 kev 2.5 kev 4.1 kev E,f ~ 4.1 kev P avg ~ 200 MW 10 2 SXR z [m]

30 Two-color generation: Some recent LCLS results Split undulator scheme 2 1+ K l 1,2 = l 1,2 w 2g 2 Gain modulation

Energy Energy Two-color generation: Two-bunch xfel

Splitter Photocathode Laser Pulse Double Pulse

X-Rays UNDULATOR Linac Electron Gun l 1,2 = l w 1+

31 Energy Energy Two-color generation: Two-bunch xfel demonstrated at LCLS Adjustable delay stage Splitter Photocathode Laser Pulse Double Pulse Bunch Compressor 1 Bunch Compressor 2 2-color X-Rays UNDULATOR Linac Electron Gun l 1,2 = l w 1+ K 2 2g 2 1,2 Few ps delay time time Few fs delay ~1% energy separation

32 FEL for FWM Control of Timing Color Angle of incidence Large bandwidth, coherent short (~1-2 fs) pulses Can be further compressed (~0.5 fs) Many additional components and significant R&D required Easily fits in SXR tunnel

Test Pulser Schematic of 1m kicker fill time = L total I where we will have 3 V

33 Ferrite Loaded Transmission Line Kicker Hardware testing has begun Loaded sections of ferrite and discrete capacitors simulate a transmission line. Test Pulser Schematic of 1m kicker fill time = L total I where we will have 3 V separate kickers for 1/3 fill time ~100ns. Recent measurements (7 out of 23) Integrated kick Individual magnets T. Beukers

34 Two-color performance and requirements Split undulator/gain modulation Performance - Peak power 5-10 x lower for both colors - Different source points - Only up to ~ 2.5 kev on HXR due to long saturation lengths Requirements - Chicane (SXR) Two bunch Performance - Both colors achieve saturation - Smaller photon tunability due to chromatic effects in transport, on order of 1-2% Requirements - Beam splitter for photocathode laser FEL for FWM Performance - Short pulses - Large bandwidth - Flexibility in timing, photon energy, angle of incidence Requirements - Two modulators, four small chicanes, single-cycle mid IR laser, beam splitter, delay stages

35 Parameter Sensitivities SXR is robust at 1.25 kev; HXR is limited at 5 kev H-D Nuhn

36 Using LCLS to Benchmark IMPACT S-2-E Simulations ubi effects will be important LCLS microbunching studies: 4GeV, 180pC, 1kA Measured final t-p phase space vs laser heater preliminary analysis of bunching factor D. Ratner, Y. Ding, et al.

37 New SCRF Linac (4 GeV) 1 st Dog Leg Bypass Line Beam Spreader LTU Transport undulators LCLS-II Layout (P. Emma, LCLS-II FAC Review) See PRD: LCLSII-2.5-PR-0134 (plan view - not to scale) LH BC1 BC2 L1 L2-Linac L3-Linac 0.93 m BC3 LCLS-I Linac Sec m D2 D10 LTUS 2.50 m SXU kicker -wall LTUH HXU glowing sections indicate these are not in the vertical plane of either linac LCLS-II Science Opportunities Workshop, February

Solid-State Amplifiers Simplify LLRF and offer better performance LCLS-II Linac SCRF proposed FACET-II Sec. 11-20 LCLS-I Linac 2.5-15 GeV Sec. 21-30 0.2-1.3 kev (0.

38 Solid-State Amplifiers Simplify LLRF and offer better performance LCLS-II Linac SCRF proposed FACET-II Sec LCLS-I Linac GeV Sec kev (0.1-1 MHz) 4 GeV 1-25 kev (120 Hz) 1-5 kev (0.1-1 MHz) SXU HXU Installing 3.8 kw SSA Need 2.6 kw with no f offset or overhead Need 3.8 kw with 10 Hz -phonic offsets, Linac Sec. V 0 (MV) 6% overhead for losses and 10 % tuning overhead - Same power allows operation at ~ 50% duty with 60 ua at 23 MV/m with 3 Hz max detuning, QL = 6e7 and the same overheads j (deg) Acc. Grad. * (MV/m) No. Cryo Mod s No. Avail. Cav s Spare Cav s L0 100 varies L HL L L Lf 202 ± Cav s per Amp.

39 High Level Photon Parameters Table 2 from Bill Schlotter s LCLS-II Introduction document Undulator Units SXR HXR Linac SC SC Cu Photon Energy kev > Max Repetition khz Rate Max Pulse Energy mj Max Power in FEE Max Power to End Station W W FWHM Pulse Duration fs 70 pc 10 pc 70 pc pc 25 pc

Tracking a 100, 300, and 20 pc Bunch Charge (with CSR, long.

6 ka Q = 100 pc e x =0.35 0.42 m (20%) heater = 5.5 kev rms j L1 = -12.7 deg V 3.

77 m (26%) heater = 11 kev rms j L1 = -14.0 deg V 3.9 = 58.0 MV j 3.

40 Tracking a 100, 300, and 20 pc Bunch Charge (with CSR, long. wakes, and separate injector runs ASTRA & Elegant) L. Wang 0.6 ka Q = 100 pc e x = m (20%) heater = 5.5 kev rms j L1 = deg V 3.9 = 64.7 MV j 3.9 = -150 deg R 56-BC2 = mm Q = 300 pc e x = m (26%) heater = 11 kev rms j L1 = deg V 3.9 = 58.0 MV j 3.9 = -150 deg R 56-BC2 = mm Q = 20 pc e x = m (44%) heater = 2.0 kev rms j L1 = deg V 3.9 = 55 MV j 3.9 = -165 deg R 56-BC2 = -62 mm

41 HXR Components THERMAL BARRIER WALL RAPID DIAGNOSTIC CHAMBER IMAGER DUMP WALL ADJ APER GAS ATTEN SOLID ATTEN K-MONO Beam Direction S UNDULATOR CENTER GAS MONITOR GAS MONITOR SXR Device Symbol HXR Count Notes Adjustable Aperture type 1 1 New Design Adjustable Aperture type 2 (mirror Slits) 1 Similar to LUSI Attenuators (Gas and Solid) 1 Modifications to the existing Gas attenuator New solid attenuator Design based on LUSI 2 No upgrades to the existing HOMS mirrors Flat Mirror New HOMS mirrors to cover SC energy range Gas Energy Monitor 2 Repurposed with upgrades High Resolution Imager 3 New design based on LUSI In line Spectrometer 1 Repurpose existing Mono 1 Repurpose existing Rapid Turnaround Diagnostics Station 1 Repurpose existing Stopper 1 New design B S BPHOTON BEAM STOPPER IMAGER HOMS1 (E) MIRROR IMAGER M2H (N) MIRROR ADJ APER M1H (N) MIRROR HOMS2 (E) MIRROR SPECTROMETER SHADOW WALL (E) FEE WALL DUMP AREA NEH WALL XRT & FEH FEE AREA NEH AREA HUTCH 1 AREA

42 IMAGER GAS ATTENUATOR END STATION 1 CENTER UNDULATOR GAS MONITOR RAPID DIAGNOSTIC ADJ APERTURE 1 ADJ APERTURE 2 IMAGER M1S1 MIRROR SHIELDING WALL IMAGER M2S1 MIRROR GAS ENERGY MONITOR IMAGER BEAM STOPPER THERMAL WALL DUMP WALL FEE WALL KBM1-VERTICAL KB MIRROR KBM1 HORIZONTAL KB MIRROR ARRIVAL TIME WAVE FRONT DUMP AREA FEE AREA NEH HUTCH-1 SXR Components B S LCLS Operations SXR Device Symbol SXR count Notes Adjustable Aperture type 1 1 New Design Adjustable Aperture type 2 (mirror Slits) 1 Similar to LUSI Attenuator (Gas) 1 New Gas attenuator, design similar to LCLS-I Flat Mirror 2 New System: very low figure error, water cooled Gas Energy Monitors 2 One repurposed system with upgrades, one new system with similar design to LCLS-I system High Resolution Imager 4 New System, design borrows elements from LUSI K-B mirrors 1 New System: Bender design leveraged on CXI system Rapid Turnaround Diagnostics Station 1 New System, use LCLS-I design Stopper 1 New Design B S

) Include bunch charge, gun laser, & chicane supplies uncorrelated rms jitter tols per cavity if jitter is correlated (cavity to cavity)

43 Verify RF Stability Tolerances by Tracking (P. Emma, LCLS-II FAC Review) Jitter Simulations in LiTrack ENERGY (<0.01%) (DE/E 0 ) rms = 0.008% OK Now verify by tracking 1000 times with random jitter Jitter may be correlated or uncorrelated (cav. to cav.) Include bunch charge, gun laser, & chicane supplies uncorrelated rms jitter tols per cavity if jitter is correlated (cavity to cavity) ARRIVAL TIME (<20 fs) Dt rms = 20 fs OK PEAK CURRENT (<4%) (DI pk /I pk ) rms = 3.8% OK * The gun timing error is compressed by 3.85 from gun to 100 MeV, due to velocity compression.

44 200 W Requirement on Photon Beamlines Will have impact but looks achievable Photon beamlines have been speced to operate at 20 W with good figure performance and 200 W The FEL s can deliver >200W over much of photon range The 200 W requirement is to provide headroom in operations and to allow for harmonics, 200 W requirement impacts stoppers, attenuators, and photon diagnostics Most issues have been resolved with small impact Some new challenges have been uncovered

45 100 pc, 1 ka: SXR SS simulation E γ = 1.24 kev typical run E ~ 1.5 μj Energy gain curve E ~ 200 μj Saturation after 16 out of 21 undulators [GW] P [GW] [W] Power (blue), Current (green) x FWHM ~ 65 fs I [ka] E [ J] s [ m] Spectrum Spectrum (blue), Filter (red) x z [m] ΔE FWHM ~ 64 mev ΔE FWHM /E 0 ~ 5.1 x 10-5 TBP ~ 4.3 ev-fs = 2.4 FTL G. Marcus /ev [N] # /ev [N] E [ev]

46 20 pc, 500 A: HXR SASE simulation E γ = 5.0 kev E ~ 27.4 μj 7 Power (blue), Current (green) FWHM ~ 20 fs Energy gain curve P [GW] I [ka] E [ J] s [ m] 10-4 Spectrum x z [m] Saturation after 24 out of 32 undulators ΔE FWHM ~ 3.5 ev ΔE FWHM /E 0 ~ 7.0 x 10-4 G. Marcus P(w) [a.u.] E [ev]

100 pc IMPACT e-beam slice properties, HXR head I ~ 720 A 4.02 4.01 60 40 5 4 E [GeV] 4 3.

5 5 4 3 2 1 I [A] s E [MeV] -40 0 10 20 30 40 50 0 s [ m] SXR 2shows larger fluctuations here, 5 σ E

47 100 pc IMPACT e-beam slice properties, HXR head I ~ 720 A E [GeV] I [ka] e n [mm-mrad] s [ m] 1 ϵ n,y ~ 0.42 mm-mrad I [A] s E [MeV] s [ m] SXR 2shows larger fluctuations here, 5 σ E but ~ 450 otherwise kev is comparable I [A] s [ m] ϵ n,x ~ 0.35 mm-mrad s [ m] 0

) Aiming for R = 10,000 L 0 br = 1.0 (25 per.

48 SXR self-seeded geometry (LCLS) λ u = 39 mm L u = 3.4 (87 per.) L br = 1.0 (25 per.) 7 undulator sections U8 removed λ u = 39 mm R = 5,000 (FWHM) L u = 3.4 (87 per.) Aiming for R = 10,000 L 0 br = 1.0 (25 per.) Gaussian filter 14 undulator sections 2% efficiency Will implement optical propagation that includes relevant spatio-temporal couplings Full 3D seed Amp E [ev] Phase

49 SS experience with LCLS, measurement and simulation 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

50 20 pc IMPACT e-beam slice properties, HXR head 10 I ~ 350 A E [GeV] I [ka] s [ m] s [ m] 0 e n [mm-mrad] I [A] 2 σ E ~ 450 kev s E [MeV] I [A] s [ m] ϵ n,x ~ 0.15 mm-mrad s [ m] 0

06 d = 2.15 30% difference in final energy 0.04 0.03 0.

51 Time-dependent S2E parameter scan (very time consuming), HXR E γ = 2 kev E TI ~ 470 μj ξ = 0.06 d = % difference in final energy E max ~ 655 μj ξ = 0.03 d = d

52 Pulse length control emittance spoiling Calculations indicate an emittance spoiler foil can withstand the full beam at high rep rate Dispersed bunch Energy chirped e-beam has x-t correlation in region of high dispersion Insert foil with triangular width to continuously tune the pulse duration Y X However, the increased load on the collimators might force operation at a low(er) rep rate

53 Emittance spoiling foil measurements at LCLS Y. Ding ~100 fs ~6 fs

54 Measured foil scan movie at LCLS Y. Ding

55 Pulse length control differential heating It is fairly easy to put a notch in the laser heater profile unspoiled heater spoiled heater Here we assume a 1 ps notch but you can get to a few 100 fs with no heroic efforts A. Marinelli

56 After compression and acceleration (S2E with ELEGANT, 100 pc) garbage few fs lasing core ~6 fs FWHM LCLS MD shifts will be dedicated to this study in the near future A. Marinelli

57 Self-seeding with a chirped e-beam for short pulses K0 K1 SASE undulator SXRSS Amplifier undulator A chirped e-beam generates a SASE signal λ1 λ1 Monochromator selects a narrow bandwidth and helps to control the seed pulse duration The seed is amplified only over a fraction of the bunch and dominates SASE Superradiance can possibly be used to further compress the pulse SASE BW chirp Mono BW Y. Ding

58 LCLS example K0 K1 SASE undulator SXRSS Amplifier undulator λ1 λ1 Power profile Power spectrum 13 fs 0.14eV ~7 fs 0.3eV

FEL SIMULATION AND PERFORMANCE STUDIES FOR LCLS-II

FEL SIMULATION AND PERFORMANCE STUDIES FOR LCLS-II G. Marcus, Y. Ding, P. Emma, Z. Huang, T. Raubenheimer, L. Wang, J. Wu SLAC, Menlo Park, CA 9, USA Abstract The design and performance of the LCLS-II