The LCLS X-Ray FEL and Related R&D at the SPPS TJNAF January 3, 24 P. Emma, SLAC Sub-Picosecond Pulse Source
Linac Coherent Light Source (LCLS( LCLS) 4 th -Generation X-ray SASE FEL Based on SLAC Linac new new RF-gun at at 2-km 2 point SASE radiation at at 1.5 1.5 Å new new bunch compressors 14-GeV electrons 1.2-µm m emittance 2-fsec FWHM pulse 2 1 33 peak brightness * 12-m m undulator in in research yard yard * photons/sec/mm 2 /mrad 2 /.1%-BW
Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center LCLS - Estimated Cost, Schedule $22M-$26M Total Estimated Cost range $265M-$315M Total Project Cost range FY25 Long-lead purchases for injector, undulator FY26 Construction begins FY27 FEL Commissioning begins September 28 Construction complete operations begins CD- CD-1 CD-2a CD-2b Title I Design Complete CD-3b XFEL Commissioning FY21 FY22 FY23 22 23 FY24 24 FY25 25 FY26 26 FY27 FY28 FY29 Construction Operation J. Galayda CD-3a CD-4
LCLS Current Layout and Future Expansion Capacity Transport Undulator Hall A Tunnel Hall B 3 Beams/mirror Expansion J. Galayda
Coulomb Explosion of Lysozyme (5 fs) Atomic and molecular dynamics occur at the fsec-scale scale J. Hajdu
Exploit Position-Time Correlation on e bunch at Chicane Center.1 mm (3 fs) rms 2.6 mm rms x,, horizontal pos. (mm) 5 µm Access to time coordinate along bunch z,, longitudinal position (mm) LCLS BC2 bunch compressor chicane (similar in other machines)
Add thin slotted foil in center of chicane y coulomb scattered e e unspoiled e coulomb scattered e 2 x x E/E t 15-µm m thick Be foil P. Emma, M. Cornacchia, K. Bane, Z. Huang, H. Schlarb (DESY), G. Stupakov, D. Walz, PRL
Track 2k macro-particles through entire LCLS up to 14.3 GeV 2 fs E/E
Genesis 1.3 FEL code z 6 m x-ray Power Power (GW) 2 fs fwhm
Micro-Bunching Instabilities FEL instability needs very cold cold e beams (small ε and E-spread) Such a cold beam is subject to other undesirable instabilities in the accelerator (CSR( CSR,, Longitudinal Space-Charge= Charge=LSC,, wakefields) current modulation Gain=1 1% 1% Z(k) t LCLS simulations (M. Borland) Saldin, Saldin, Schneidmiller, Yurkov Yurkov
How cold is the photo-injector beam? Parmela Simulation TTF measurement 3 kev H. Schlarb, M. Huening E/E measured simulation t (sec) 3 kev, accelerated to 14 GeV, and compressed 36 3/14 1 1 6 36 < 1 1 1 5 Too small to be useful in FEL (no effect on FEL gain when <1 1< 1 4 )
Laser Heater for Landau Damping 8 nm, 1.2 MW 1 cm 5 cm 2 cm θ 5.7º 1 per. undulator 1 cm ~12 cm Laser-electron electron interaction in undulator induces energy modulation (at 8 nm) 4 kev rms Inside weak chicane for laser access and time-coordinate smearing (Emittance growth negligible) Z. Huang, M. Borland (ANL), P. Emma, J. Wu, R. Carr, C. Limborg, G. Stupakov, J. Welch
laser spot much bigger than e spot +6 kev P = 37 MW w 3 mm large laser spot σ x,y 2 µm laser spot similar to e spot P = 1.2 MW w = 35 µm matched spot σ x,y 2 µm 6 kev 8 nm In In Chicane 8-nm structure then gets smeared by chicane: σ z x' 2 1/2 η x >> V kev 1.15.1.5 large spot small spot 4 kev rms 5 5 mc 2 kev
The GOOD (w = 35 µm, P = 1.2 MW), the BAD ( w = 3 mm, P = 37 MW), small spot double-horn Final long. phase space at 14 GeV for initial 15-µm, 1% seed no heater and the UGLY (no heater)
Sliced final energy spread in FEL at 14 GeV σ E /E ( 1 4 E /E ( 1 4 ) ) 18 18 16 16 14 14 12 12 1 1 8 8 6 6 λ = 15 µm, I/I = 1% (a) (a) 4 4 2 (b) 2 (b) (c) (c) 4 4 2 2 2 2 4 4 z z (µm) (µm) FEL Power Gain Length 6 5 4 1 2 3 4 Σ f 1 4 (a) No heater (b) w = 3 mm, P = 37 MW (c) w = 35 µm, P = 1.2 MW Ming Xie scaling to be published in PRSTAB
Short Bunch Generation in the SLAC Linac Damping Ring (γεγε 3 µm) σ z 6 mm RTL 1 GeV 1.1 mm σ z 5 µm 3 GeV σ z 12 µm add add 14-meter chicane compressor in in linac linac at at 1/3-point (9 (9 GeV) SLAC Linac FFTB E/ E /% σ / E =1.51% (FWHM: 4.33%) E 4 2 2.5 1 1.5 2 n/1 3 3 ka 8 fsec FWHM E/ E /% 2.1.2.3 z /mm σ = 28. µm (FWHM: 24.6 µm, Gauss: 11. µm) z I /ka E = 28.493 GeV, N = 2.133 1 1 ppb e 4 2 3 I = 3.631 ka pk 25 2 15 1 5.1.2.3 z /mm Existing bends compress to 4 fsec ~1.5 Å compression by factor of 5 P. Emma et al.,, PAC 1
δ /%.4.2.2 energy profile σ E / E =.8 %.8 % 2 4 n/1 3 E = 1.19 GeV, N e = 2.2 1 1 ppb.3 δ /%.2.1.1.2.3 phase space 1 1 2 z /mm I /ka.6.4.2 temporal profile σ z = 6. mm 2 2 z /mm 6 mm Particle tracking in 2D 1.19 GeV E/ E /% 3 2 1 1 2 3 σ E / E =1.16 % 1.2 % 1 2 3 n/1 3 E/ E /% E =1.189 GeV, N e =2.2 1 1 ppb 3 2 1 1 2 3 2 2 z /mm I /ka.6.4.2 σ z = 6. mm 2 2 z /mm 6 mm 1.19 GeV E/ E /% E/ E /% E/ E /% E/ E /% E/ E /% 2 1 1 2 6 4 2 2 4 6 6 4 2 2 4 2 2 4 2 2 σ E / E =1.71 % 1.1 % 1 2 n/1 3 1.6 % σ E / E =1.59 % 1.5 % σ E / E =1.59 % 2 4 n/1 3 σ E / E =1.561 % 1.6 % 1 2 3 n/1 3 σ E / E =1.515 % 1.5 % 1 2 n/1 3 1 2 n/1 3 E/ E /% E/ E /% E/ E /% E/ E /% E =28.492 GeV, N 4 e =2.133 1 1 ppb 3 E/ E /% E =1.189 GeV, N e =2.133 1 1 ppb 2 1 1 2 5 5 2 2 2 2 4 z /mm 2 2 4 z /mm.1.2.3 z /mm I /ka E =9.1 GeV, N e =2.133 1 1 ppb I /ka E =9.4 GeV, N e =2.133 1 1 ppb 4 2 2.2.4 z /mm I /ka I /ka.3.25.2.15.1.5.3.25.2.15.1.5 1 E =28.487 GeV, N =2.133 1 1 ppb e 4 1 2 2.2.4 z /mm I /ka 8 6 4 2 8 6 4 2 25 2 15 1 5 σ z = 1.158 mm 2 2 4 z /mm σ z = 1.158 mm σ z = 28. µm 1.2 mm 1.2 mm 2 2 4 z /mm σ z = 55.5 µm 5 µm.2.4 z /mm σ z = 55.5 µm 5 µm.2.4 z /mm 12 µm.1.2.3 z /mm 1.19 GeV 9 GeV 9 GeV 28 GeV 28 GeV
Linac and FFTB Hall SLAC linac add undulator to to FFTB hall at at end of of linac
Undulator, view upstream Dave Fritz, Soo Lee, David Reis Undulator parameters: L u 2.5 m, λ u = 8.5 cm, K 4.3, B.55 T, N p 3
Source comparisons Table top laser plasma ALS* (streak camera) Peak brightness** Pulse length (fsec) Average flux (photons/sec) Photons per pulse per.1% BW Rep. Rate (Hz) 1 11 9 5 1 11 6 1 1 11 4 5 1 17 4 1 4 2 1 8 2 1 4 1 11 4 ALS slicing (undulator) 1 11 17 (6 1 1 19 19 ) ESRF 1 11 24 SPPS 1 11 25 8 1 1 11 5 (3 1 4 ) 1 (3) 1 11 4 24 8 1 4 3 1 1 3 1 7 9 8 2 1 7 2 1 6 1 ** photons/sec/mm 2 /mrad 2 /.1%-bw * streak camera resolution 1 psec, dqe.1 J. Hastings * streak camera resolution 1 psec, dqe.1
UC Berkeley DESY Roger W. Falcone Jochen Schneider Aaron Lindenberg Thomas Tschentscher Donnacha Lowney Horst Schulte-Schrepping Andrew MacPhee APS Argonne Nat l Lab BioCARS ESRF ESRF F. F. Sette Sette SPPS Collaboration Dennis Mills Keith Moffat Reinhard Pahl MSD Argonne National Lab Paul Fuoss Brian Stephenson U. of Michigan SLAC David Reis Paul Emma Philip H. Bucksbaum Patrick Krejcik Adrian Cavalieri Holger Schlarb (DESY) Soo Lee John Arthur David Fritz Sean Brennan Matthew F. DeCamp Roman Tatchyn Jerome Hastings Kelly Gafney NSLS Copenhagen University D. Peter Siddons Jens Als-Nielsen Chi-Chang Kao Uppsala University Janos Hajdu Lund University David van der Spoel Jörgen Larsson Richard W. Lee Ola Synnergren Henry Chapman Tue Hansen Carl Calleman Magnus Bergh Chalmers University of Technology Gosta Huldt Richard Neutze Sub-Picosecond Pulse Source
R&D at SPPS Towards LCLS Wakefields of micro-bunch in RF structures Develop bunch length diagnostics RF phase and voltage stability of linac Emittance growth in compressor chicane (CSR)
Wakefield energy-loss used to confirm bunch length φ 1 (deg) K. Bane et al.,, PAC 3 Chicane energy constant to <5 MeV (.6%) rms
Bunch length confirmed with strong wakefield-induced induced energy loss of 187-m m of SLAC linac: σ zmin 5 µm.
Far-Infrared Detection of Wakefields from Ultra-Short Bunches Linac RF phase (chirp) H. Schlarb (DESY), et al.
Bunch length is also measured with transverse deflecting rf : σ z 5 to 7 µm 5 µm 28 GeV R. Akre et al.,, EPAC 2 deflector OFF deflector ON σ 2 y (arb) 62 µm m rms bunch length rf phase (deg)
P. Muggli, M. Hogan
8 fs rms (15 ka)
Linac Phase Stability Estimate Based on Energy Jitter in Chicane BPM SLAC Linac 1 GeV 9 GeV 3 GeV σ E /E.6% e Energy (MeV) φ 2 1/2 <.1 deg (1 fs)
Chicane Parameters 14.3 m L. Bentson et al.,, PAC 1
e 14-m m chicane in sector-1 of SLAC linac
Last Y-chamber Y was copper coated to limit resistive-wake. Small tweaker quads included to control residual x-dispersion. Vacuum chamber too large for CSR shielding (πσ z R 1/2 ) 2/3 8 mm << r
Dispersion is measured by energy variations correlated with BPM readings tweaker quads Z/m
Four wire-scanners within 6 m of end of chicane used to measure x- emittance. Emittance measured with precision of 2-4%, 2 over <1 hour. β x = 5 m
Horizontal beta function through chicane effects emittance growth has been matched and verified: β x (m) α x ζ x Design: 47.2 2.3 1. Measured: 5.6 ± 1.7 2.17 ±.8 1.2 ±.3
Residual x-dispersion (and its angle) is precision minimized using tweaker quads in the chicane Linear comb. of tweaker quads
CSR simulations with 1D model (unshielded) (good agreement with 3D-model studied by F. Stulle - DESY) 3.4 nc FWHM/2.35 35 µm.3 ka 9 ka
CSR simulations (1D) along chicane ~2% ~1% ISR = Incoherent Synch. Rad.
All 4 individual beam sizes with asymmetric-gaussian fits wire-1 wire-1 σ x = 263 µm σ x = 335 µm wire-2 wire-2 σ x = 8 µm σ x = 9 µm wire-3 wire-3 σ x = 25 µm σ x = 245 µm chicane-off chicane-on wire-4 wire-4 σ x = 113 µm σ x = 142 µm
Chicane OFF Chicane ON γε x = 27.6 ±.6 µm γε x = 34.2 ±.7 µm
Bend-Plane Emittance: Chicane ON and OFF Bend-plane emittance data is consistent with calculations and sets upper limit on CSR effect P. Emma et al.,, PAC 3
Concluding Remarks Emittance growth consistent with calculations, but no rad.. measurements SPPS will run until LCLS displaces the beamline in ~27 LCLS will begin operation at end of 28 Spontaneous device can be added to LCLS to allow Super-SPPS SPPS in long-term Thanks Alex and Lia for invitation