LCLS-II: Accelerator Systems LCLS SAC Meeting P. Emma et al. April 23, 2010

LCLS-II: Accelerator Systems Page Å FEL Saturation at 65 m (of 112 m) This success motivates an extension of the capacity, capabilities, and quality of this revolutionary new light source. April 26, 2009

LCLS Beam Supports 25-keV (0.5 Å) FEL at 14 GeV increase undulator gap further  x,y = 0.4  m (slice) I pk = 3.0 kA  E /E = 0.01% (slice) 0.5 Å Same beam quality and energy as now 1.5 Å K = 1.65

Ultra-Short Pulses in Operation at LCLS BC2 4.3 GeV BC2 4.3 GeV BC1 250 MeV BC1 250 MeV L1S L2-linac L3-linac DL1 135 MeV DL1 135 MeV gun  wall undulator 4-14 GeV undulator 4-14 GeV 1.5 Å Et under- compressed  =  0.6º E tfullycompressed peak current monitor (CSR) gas detector (FEL power) Measurements at 20 pCEt over-compressed  =  0.5º 

Ultra-Short X-ray Pulse Simulations Suggest <10 fs FWHM 20 pC bunch charge 3 keV initial rms slice energy spread 0.23-mm initial rms bunch length X-ray pulse duration should be <10 fs (FWHM), but no measurement possible yet …now delivered to users fully compressed

LCLS-II Requirements Build new soft x-ray line from 200 to eV Extend hard x-rays out to ~20 keV Include seeding options for narrow BW Incorporate 2-pulse, 2-color schemes Provide polarization control Take advantage of 3-km SLAC linac to provide separate sources for independent FELs Explore multi-bunch operations Find ways to increase capacity (user access)! Build new soft x-ray line from 200 to eV Extend hard x-rays out to ~20 keV Include seeding options for narrow BW Incorporate 2-pulse, 2-color schemes Provide polarization control Take advantage of 3-km SLAC linac to provide separate sources for independent FELs Explore multi-bunch operations Find ways to increase capacity (user access)! LCLS-II: Accelerator Systems Page 6

X undulator L1 L2L3BC1BC2 RFgun-1 L GeV sector-10sector-20sector-24sector-14 existing LCLS enclosure exists at sector 10 und-hall sector-30 L3 XRFgun-2L1 L2BC1BC2 L0 Sector-20 wall 3-7 GeV e  bypass line 3-7 GeV new undulators LCLS-II: New Injector & Accelerator Use 2 nd km of SLAC linac (sector-10 to 20) – greater flexibility 3-7 GeV energy (no SLED) allows possible 360-Hz beam rate 2 nd injector, linac, & bypass line allows 2+ independent FELs serving 2 experiments simultaneously with flexible parameters Combining beams allows x-ray pump/probe with decoupled wavelengths, pulse width, energy, and timing Preserves possibility of GeV (and still 1 more km left!)

Phase-1 (2010) Å GW 3-15 GeV FEE-1 Existing 112-m Undulator ( Å) SHAB 30 m Å Shortened 80-m ( Å) FEE-2 SXR2 (36 m) 5 m full polarization control self-seeding option 6-60 Å adjust. gap 6-60 Å adjust. gap SXR1 (36 m) 3-7-GeV bypass 3-7-GeV SXR and 3-15-GeV HXR simultaneous op’s with bypass line 2-pulse 2-color No civil construction. Uses existing beam energy and quailty. ExistingPhase-2Phase-3EEHG*? 240 nm  6 nm Phased Enhancement Plan for LCLS-II FELs * G. Stupakov, Phys. Rev. Lett. 102, (2009) 5 m full polarization control Å Increased fixed-gap: 112 m ( Å) Å Å (54 m) Å (54 m Å (54 m) self-seeding HXR option (2 bunches) Å 1-2 GW H.-D. Nuhn

1.5 Å (and 0.5 Å), K = Å, K = 2.26 /2 /2 Fast Path to Producing FEL 2 nd Harmonic 16 keV = 0.75 Å (up to 20 keV at 15 GeV) Smaller  function in afterburner helps 2 nd harmonic after-burner 9 undulators LCLS undulator cross- section Replace shims for last 8-10 undulators (of 33) Z. Huang, S. Reiche existing LCLS undulator 2 nd harm. bunching 2 nd harm. bunching

10-m chicane 1 st undulator 2 nd undulator SASE FEL grating Seeded FEL grazing mirrors slit e  dump Self-Seeded SXR FEL in LCLS-II FWHM 3.1  10  4 FEL spectrum at ~26 m in 2 nd undulator for seed of 0.1 MW () and 0.01 MW (red). FEL spectrum at ~26 m in 2 nd undulator for seed of 0.1 MW (black) and 0.01 MW (red) MW 0.1 MW 10 MW 2 nd undulator Power on monochromator is amplified 1 st undulator 6 nm Power over 1 st undulator eeee J. Wu et al. (10% transmission)

LCLS-II: Accelerator Systems Page 11 The next 6 slides will graphically outline 6 LCLS-II operating modes… (thanks to H.-D. Nuhn) 1.Hard X-ray SASE 2.Soft X-ray SASE 3.Soft X-ray Self Seeding 4.Two-pulse, two-color soft x-rays (one e  bunch) 5.Two-pulse, two-color soft x-rays (two e  bunches) 6.Seeded soft x-ray FEL (‘Echo’) 7.Self Seeding of hard x-rays (two e  bunches)

FEE-1 FEE-2 SX2 (36 m) APU polarization control self-seeding option 6-60 Å adjust. gap 6-60 Å adjust. gap Sector-10 Gun 3-7-GeV Beam SX1 (36 m) 2-pulse 2-color 1. LCLS-II: Hard X-Ray SASE APU polarization control Sector-20 Gun GeV Beam APU SHAB ( Å) LCLS-I Undulator ( Å) 2 nd harmonic after-burner in 2010 ( Å, 1-2 GW) Open all 33 undulator gaps for LCLS-II ( Å, GW) Or (?) replace all with variable gap ( Å, >20 GW) Z. Huang, S. Reiche, FEL’04, 201, (2004). Larger Gap Undulator (112 m) ( Å)

FEE-1 polarization control Sector-20 Gun GeV Beam Larger Gap Undulator ( Å) APU SHAB ( Å) LCLS-I Undulator ( Å) FEE-2 SX2 (36 m) APU polarization control self-seeding option 6-60 Å adjust. gap 6-60 Å adjust. gap Sector-10 Gun 3-7-GeV Beam SX1 (36 m) 2-pulse 2-color 2. LCLS-II: SX2 (or SX1) SASE APU polarization control APU Simple use of new soft x-ray line: SASE from SX2 (or SX1) Full polarization control (fast at 80% or slow at ~100%) Y. Ding, Z. Huang, Phys. Rev. ST-AB 11, (2008).

FEE-2 SX2 (36 m) polarization control self-seeding option 6-60 Å adjust. gap 6-60 Å adjust. gap Sector-10 Gun 3-7-GeV Beam SX1 (36 m) 2-pulse 2-color 3. LCLS-II: Soft X-Ray Self-Seeding APU polarization control APU FEE-1 polarization control Sector-20 Gun GeV Beam Larger Gap Undulator ( Å) APU SHAB ( Å) LCLS-I Undulator ( Å) SX1 pulse passes monochromator and seeds SX2 pulse Narrow bandwidth pulse to <10  4 FWHM (6-60 Å) Can also use chirped bunch to generate short pulse (<50 fs) J. Feldhaus et al., Opt. Commun. 140, 341 (1997).

FEE-1 FEE-2 polarization control self-seeding option 6-? Å adjust. gap ?-60 Å adjust. gap Sector-10 Gun 3-7-GeV Beam SX1 (36 m)delay polarization control 4. LCLS-II: SX1 & 2 SASE, One-Bunch, Two-Color APU polarization control Sector-20 Gun GeV Beam Larger Gap Undulator ( Å) APU SX2 (36 m) One e  bunch produces 2 SXR pulses (0-15 ps separation) for pump probe Deliver both pulses to one experiment or split them to two SX2 pulse color (  ) must be longer wavelength than SX1 (  ) Angled SX2 suggested by J. Hastings and P. Heimann  

FEE Å adjust. gap 6-60 Å adjust. gap Sector-10 Gun 3-7-GeV Beam SX1 (36 m) 5. LCLS-II: SX1 & 2 SASE, Two-Bunch, Two-Color Sector-20 Gun GeV Beam Larger Gap Undulator ( Å) APU DC Dipole Magnet FEE-2 SX2 (36 m) Fast Kicker Magnet e  Dump color-1 color-2 Two e  bunches ns apart (no pump probe here) One fast kicker & one DC – each bunch lases in just one FEL Allows 2 SXR experiments simultaneously (user doubler) Two colors can be any value (6-60 Å) Suggested by J. Frisch and independently by R. Brinkmann et al.

FEE-1 polarization control Sector-20 Gun GeV Beam Larger Gap Undulator ( Å) APU SHAB ( Å) LCLS-I Undulator ( Å) FEE-2 SX2 (36 m) APU polarization control self-seeding option 6-60 Å adjust. gap 6-60 Å adjust. gap 2-pulse 2-color 6. LCLS-II: Echo Seeding of SX1 or SX2 polarization control APU External seeding (~30-60 Å) using Echo-Enhanced Harmonic Generation (EEHG*) – not in LCLS-II baseline at present Allows narrow BW and longitudinal coherence Under study now at NLCTA (SLAC) EEHG 240 nm  6 nm Sector-10 Gun 3-7-GeV Beam APU * G. Stupakov, Phys. Rev. Lett. 102, (2009) SX1 (36 m)

Planar + Helical Stable >90% polarization Slow switching Planar + Helical Stable >90% polarization Slow switching Planar + Crossed Planar May have fluctuations ~80% polarization Fast switching Planar + Crossed Planar May have fluctuations ~80% polarization Fast switching Planar + Crossed Pair at Stable ~90% Fast switching ~1% of fundamental power Planar + Crossed Pair at Stable ~90% Fast switching ~1% of fundamental power EPUEPU ~4L G helical operate near saturation EPUEPU APPLE planar mode ( y ) fast polarization control with pulsed phase shifter EPUEPU EPUEPU 2 crossed planar APPLEs at operate in saturation PlanarPlanar PlanarPlanar PlanarPlanar ~1.3L G for P x = P y Z. Huang

Peak Brightness of LCLS H.-D. Nuhn

LCLS-II Timeline, Compatible with Operations Annual 3 month summer downtime FY12 FY12 FY13 FY13 FY15 FY15 FY14 FY14 FY16 FY16 FY17 FY17 Phase-1 Installation Phase-2 Installation ED&IED&I FabricationFabrication FY11 FY11 R&DR&D CD 1 CD 2, 3a CD 3 CD 4 CDR InstallationInstallation FY10 FY10 CD 0 Facilities Installation FY18 FY18 LCLS-II: Accelerator Systems Page 20

LCLS-II Accelerator Summary Soft X-Rays: 2-pulse, 2-color, variable delay (6-60 Å) using 1 e  bunch or 2 Self-seeding for narrow bandwidth (~10  4 at 6-60 Å) Full polarization control in SASE and self-seeded modes (fast & slow) 3-7 GeV bypass line allows simultaneous soft and hard x-ray operations in two separate beamlines with completely independent parameters Single femtosecond near-transform limited spike in low-charge mode LCLS-II: Accelerator Systems Page 21 Hard X-Rays: Harder x-rays (0.62 Å) by modifying all undulators Few femtosecond pulses possible in low-charge mode Full polarization control Self-seeding with 2 electron bunches and short chicane (4 m) And… GeV still possible using both 1-km linacs (+ 3 rd km still open)