PAC-2001, Chicago, IL Paul Emma SLAC SLAC Issues and R&D Critical to the LCLS UCLA LLNL

PAC-2001, Chicago, IL Linac Coherent Light Source (LCLS) 14.3-GeV electrons14.3-GeV electrons 1-  m emittance1-  m emittance 230-fsec FWHM pulse230-fsec FWHM pulse 2  peak brightness *2  peak brightness * over 3 rd -gen. sources10 10 over 3 rd -gen. sources * photons/sec/mm 2 /mrad 2 /0.1%-BW add bunch compressors install 120-m undulator in ‘FFTB’ hall new RF-gun at 2-km point produce intense x-ray SASE radiation at 1.5 Å 4 th -Generation X-ray SASE FEL Based on SLAC Linac

PAC-2001, Chicago, IL Other FEL-based sources being tested, built, or planned…  Source Development Laboratory (SDL) at BNL-NSLS  Electron beam testing  VISA experiment at BNL-ATF  Saturation achieved, March 2001  FEL’s under study in Japan, Italy, England and Germany (BESSY II)  X-ray TESLA FEL at DESY (associated with linear collider)  TDR written  Harmonic Generation (HGHG) successful at BNL-ATF  Low Energy Undulator Test Line (LEUTL) at ANL-APS  High gain and saturation observed at 390 nm  TESLA Test Facility (TTF) at DESY  Lasing with gain ~3000 observed at nm

PAC-2001, Chicago, IL  Design Study Report published 1998 (SLAC-R-521) led by Max Cornacchia  New LCLS project leader at SLAC is John Galayda (formerly of ANL/APS)  Critical Decision-0 (CD-0) approval was signed by DOE in June 2001 LCLS Project Update  Pre-engineering in 2003, construction in 2004, and operation in 2007  Published plan for first 5 experiments (femto-chemistry, atomic physics, warm dense matter, …), Sep. 2000

PAC-2001, Chicago, IL  Acceleration and Compression  Undulator  X-ray optics  Injector Requirements LCLS Issues and R&D    1  m at 1 nC and 100 A  Stability <1 psec timing & <2% charge   -preservation  ‘CSR’ and wakefields  RF stability of 0.1°, 0.1% rms  Design, precise fabrication, and thermal stability  Trajectory alignment to <5  m  Undulator wakefields

PAC-2001, Chicago, IL Booster linac: 150 MeV Emittance: 1  m Charge: 1 nC Current: 100 A Booster linac: 150 MeV Emittance: 1  m Charge: 1 nC Current: 100 A Courtesy of J. Clendenin, M. Hernandez, J. Schmerge, SLAC RF Photo-Cathode 1.6-cell S-band Gun fullcell halfcell e.g., Cu photocathode ‘QE’  5  10  5 ‘QE’  5  10  5 Designed by: D. Palmer (SLAC) R. Miller J.N. Weaver X.-J. Wang (BNL) I. Ben-Zvi, K. Batchelor C. Pellegrini (UCLA) J. Rosenzweig K.-J. Kim (ANL) Pulse: 10 ps FW UV Energy: 0.1 mJ Wavelength: 266 nm Pulse: 10 ps FW UV Energy: 0.1 mJ Wavelength: 266 nm GTF UCLA eeee ~120 MV/m

PAC-2001, Chicago, IL diagnostic room Courtesy of J. Schmerge, SLAC diagnostics 3-m linac RF gun (GTF) in SSRL Injector Vault Gun Test Facility GTF Laser room GTF control room Injector vault Quadrupole magnets YAG screen LCLS Injector R&D

PAC-2001, Chicago, IL Emittance measured at 30 MeV with ‘quad-scan’ on YAG screen, varying charge and bunch length Q/nC  /  m 2 ps FWHM 4 ps FWHM Quad-scans on YAG screen, no space charge correction 4 ps FWHM GTF Emittance Measurements: Spring 2001 S. Gierman, J. Schmerge, SLAC LCLS requires: 10 ps FWHM Q = 1 nC  = 1  m LCLS requires: 10 ps FWHM Q = 1 nC  = 1  m more work ahead… BNL/ATF result May 2001: Q  0.5 nC   0.84  m V. Yakimenko et. al., FEL2001 no temporal pulse shaping yet 2 ps FWHM

PAC-2001, Chicago, IL L  6 m R 56  36 mm L  24 m R 56  22 mm L  66 m R 56 = 0 L  120 m L  9 m  rf  38° L  330 m  rf  43° L  550 m  rf  10° Linac-0 L  6 m LCLS Acceleration and Compression undulator 150 MeV  z  0.83 mm    0.10 % 250 MeV  z  0.19 mm    1.8 % 4.54 GeV  z  mm    0.76 % GeV  z  mm    0.02 % SLAC linac tunnel undulator hall...existing linac new Linac-3Lin-1Linac-2 BC1BC2 DL2 Linac-X L  0.6 m  rf =  X  Emittance control given coherent synchrotron radiation in bends  Adequate machine stability (RF, charge, bunch-timing, …) RFgun 2-km point in SLAC linac double chicane reduces CSR

PAC-2001, Chicago, IL After BC1  z = 227  m Non-linearity limits compression… …and spike drives CSR After BC1  z = 200  m distribution unchanged S-band RF curvature and T 566 non-linearity After S-band  z = 840  m …linearizer also reduces bunch length sensitivity to timing jitter x X-band X-band Similar scheme used at TESLA: DESY (P. Piot, et. al.) energy-time correlation X-band compensation  20 MV, 0.6 m long

PAC-2001, Chicago, IL V = 22 MV f = 11.4 GHz P = 30 MW L = 0.6 m  = 250 MeV And… Linearizer allows analytical modeling of wakes (~uniform pulses) and therefore fast, automated LCLS parameter optimization 0.5-Meter X-Band RF Accelerating Structure

PAC-2001, Chicago, IL 6D-Tracking using Parmela to 150 MeV and Elegant* to undulator, including:  Space charge (to 150 MeV)  Misalignments (RF, quads, BPMs)  2 nd -order optics  CSR and ISR  Long. And Trans. Wakefields  Resistive-wall wakefields  Steering  Emittance correction TRACKING energy profile energy-timetemporaltransverse * Elegant, by M. Borland 150 MeV 250 MeV 4.54 GeV 14.3 GeV 22  m 195  m 830  m 22  m 0.02%

PAC-2001, Chicago, IL Start-to-End Simulations M. Borland, WPPH103 LCLS Twiss parameters x ‘slice’ emittance gain length per slice Ming-Xiemethod BC1BC2undulator Corrected Trajectories includes wakes, CSR, 2 nd order,… CSR model is critical S. Reiche, WPPH MeV 14.3 GeV Time-sliced beam is input to Genesis-1.3, including centroid and rms of each slice in 6D

PAC-2001, Chicago, IL Stability Studies Pulse-to-pulse ‘jitter’ estimates based on repeated tracking including parameter variations M. Borland, WPPH103 More studies including CSR and 6D tracking in… 22  3  m rms bunch length variation 0  109 fsec rms arrival time variation linac  phase  0.1 deg-S rmslinac  phase  0.1 deg-S rms linac  voltage  0.1% rmslinac  voltage  0.1% rms Gun timing jitter 0.9 psecGun timing jitter 0.9 psec Charge jitter 2% rmsCharge jitter 2% rms linac  phase  0.1 deg-S rmslinac  phase  0.1 deg-S rms linac  voltage  0.1% rmslinac  voltage  0.1% rms Gun timing jitter 0.9 psecGun timing jitter 0.9 psec Charge jitter 2% rmsCharge jitter 2% rms R. Akre, TPAH105 Track 100k macro-particles in long.-2D 2000 times with ‘jitter’…

PAC-2001, Chicago, IL LEUTL CSR Measurements (ANL) energy spread [%] rms bunch length [ps] emittance [mm-mrad]  over-compression RF phase [deg-S] M. Borland, RPAH001 minimum compression Elegantmodel 3-screen data At end of LEUTL bunch compressor chicane Courtesy M. Borland, J. Lewellen, ANL Q  0.3 nC Using line-charge CSR model of Saldin, et. al.

PAC-2001, Chicago, IL built in 1960’s (G. Loew…) P. Krejcik, WPAH116 P. Emma, J. Frisch, P. Krejcik, G. Loew, X.-J. Wang V 0  15 MV  z  22  m, E  6 GeV eeee zzzz 2.44 m cccc pppp   90° V(t)V(t)V(t)V(t) xxxxRF‘streak’ S-band Transverse RF Deflector for Bunch Length Measurement V 0 = 20 MV  y  250  m  z  22  m y-z streak generated by deflector

PAC-2001, Chicago, IL Undulator Hall (FFTB) Install 122-m long planar undulator in existing FFTB hall Near hall Far hall UndulatorUndulator SLAC looking west Inside FFTB hall

PAC-2001, Chicago, IL QFQDBPM space for x- ray diagnostics undulator section 3.42 m Vanadium permendu r poles Nd-Fe-B magnets Undulator (ANL/APS) Beam Pipe: 5-mm ID 120-m Length undulator line length 122m undulator period, u 30mm undulator parameter, K 3.71 undulator section length 3.42m magnetic gap height 6.0mm No. of undulator sections 33 break length (short) 0.19m break length (long) 0.42m 1-  m BPM  cavity and button-type in compact package (G. Decker, ANL) E. Moog, TOPA012 Quad-magnets and undulator sections on independent movers eeee Planar hybrid type vacuum pump

PAC-2001, Chicago, IL Titanium strong- back Va permendur poles Nd-Fe-B magnets Courtesy E. Gluskin, ANL LCLS 9-Pole Prototype Undulator (ANL) E. Moog, TOPA012 Al temperature- compensation plate 3.4-m section is under construction at ANL

PAC-2001, Chicago, IL Simulate alignment procedure with many realistic errors: BPMs, quads, poles, … RON simulation shows saturation length increase by <1-gain length (R. Dejus, N. Vinokurov) Undulator Beam-Based Alignment  x > 500  m  x  1.5  m   100° S/m trajectory after 3 rd pass of BBA uncorrected trajectory S/m Quadrupole positions BPM read-back True trajectory BBA used at TTF-FEL: DESY (P. Castro, et. al.) beam size:  30  m

PAC-2001, Chicago, IL  Undulator wakefields alter energy profile along bunch during FEL amplification  Resistive-wall and surface- roughness wakes are important  Limits are tight (  E/E<0.1% rms) study roughness character with atomic force microscope using SS “A5” finish (Stupakov, et. al.) S. Reiche, WPPH119 G. Stupakov, SLAC microscopic surface finish Wakefields in Undulator Simulate SASE gain with Genesis including roughness and resistive- wall wakefields…  = 1.1 mm, I pk = 3.4 kA, Q = 1 nC Simulate SASE gain with Genesis including roughness and resistive- wall wakefields…  = 1.1 mm, I pk = 3.4 kA, Q = 1 nC ‘long’ aspect ratio of surface roughness is important 186-nm rms roughness 100  m 0.5  m resistive wake z [m] P [W] Courtesy S. Reiche, UCLA no wakes (25 GW) long bumps (500:1) (16 GW) short bumps (50:1) (10 GW)

PAC-2001, Chicago, IL  Intense x-ray interaction with matter X-ray Optics R&D  Attenuation cell (1  10  4 )  Experimental station needs  Theory, modeling  component survivability  diffraction exp’t FY01  Gases (N, Ar, Xe, …)  Differential pumping  Mirror optics  Crystal optics  Temporal compression  Focusing optics LCLS device is even smaller x-ray collimating and focusing optics from smooth mandrel & sputtered W-Re

PAC-2001, Chicago, IL Radiation damage interferes with atomic positions and the atomic scattering factors Janos Hajdu Motivation for even shorter x-ray pulses  t /fsec Further e  compression difficult:  CSR in bends  Undulator wakefields Coulomb Explosion of Lysozyme (50 fs) Compress x-ray pulse with chirp & slicer (R. Bionta, LLNL) …or… …or…

PAC-2001, Chicago, IL Two-stage undulator for shorter pulse 52 m 43 m eeee 30 m SASE gain (P sat /10 3 ) SASE Saturation (23 GW) Si monochromator (T = 40%) time Energy C. Schroeder, WPPH121 time Energy  E FW /E = 1.0% time  t FW = 230 fsec x-ray pulse 1.0  10  4 time  t FW < 10 fsec Mitigates e  energy jitter and undulator wakes Also a DESY scheme which emphasizes line-width reduction (B. Faatz) UCLA

PAC-2001, Chicago, IL 4-m undulator in ATF at BNL for SASE R&D at 830 nm Wavelength 840 nm Pulse Energy vs Position 16 March 2001 VISA Preliminary results (unpublished) showing large gain (2  10 7 ) in SASE FEL radiation and evidence of saturation at 840 nm. Visible to Infrared SASE Amplifier LCLS Collaboration Data points taken along undulator Onset of saturatio n Wavelength840nm Average Charge170 pC Measured Projected Emittance:1.7  m Energy Spread0.07 % Gain Length18.7 cm Total Gain2×10 7 Wavelength840nm Average Charge170 pC Measured Projected Emittance:1.7  m Energy Spread0.07 % Gain Length18.7 cm Total Gain2×10 7 Pop-In Diagnostics BNL-LLNL-SLAC-UCLA eeee A. Tremaine, WPPH122 A. Murokh, A. Murokh, WPPH118

PAC-2001, Chicago, IL New proposal for:  LCLS accelerator and x-ray optics R&D  Ultra-short x-ray science program at SLAC 28 GeV Add 12-meter chicane compressor in linac at 1/3-point (9 GeV) Damping Ring (   30  m) 9 ps 0.4 ps 80 fs 50 ps SLAC Linac 1 GeV GeV FFTB RTL 30 kA 80 fsec FWHM 1.5% Short Bunch Generation in the SLAC Linac Compress to 80 fsec in 3 stages Existing bends compress to <100 fsec ~1 Å 10-m undulator P. Emma, P. Emma, FPAH165 Add to understanding of CSR and X-ray optics

PAC-2001, Chicago, IL  Emittance generation and preservation Summary of Key Issues  Stable operation  Undulator errors and trajectory control  Gun   1  m, repeatable at 120 Hz  Need better understanding of CSR  RF, laser, and feedback systems  Fabrication, alignment, and BPMs  Wakefields  SASE saturation at ~1Å