LCLS Status and Micro-Bunching Workshop at LBNL. Torsten Limberg

Transcription

1 LCLS Status and Micro-Bunching Workshop at LBNL Torsten Limberg

2 Workshop Home Page

3 Workshop 0: S2E & Instabilities in Zeuthen 2003

4 Zeuthen 2003

5 Laser Heater

6 Gain Calculations Zeuthen 2003

7 More Gain Calculations Zeuthen 2003

8 Back to LBNL Workshop: Presentations Page

9 Talk Layout Tour Through the Workshop Program The LCLS COTR Problems and its Laser Heater LCLS Status

10 Program Microbunching Workshop II LBNL, 6-8 October, 2008 Semi-Final Program Schedule [last updated 2 October 2008] Monday, 6 October Introduction 9:00 9:20 9:00-9:05 Welcome, S. Gourlay, LBNL AFRD Head 9:05 9:20 Workshop Goals + Facilty Info. Nuts & Bolts, W. Fawley, LBNL Session I - Observations of Microbunching 9:20-12:30 Chairman: M. Cornacchia 9:20-9:50 Microbunching Observations at LCLS -- Z. Huang, SLAC 9:50-10:20 Microbunching Observations at FLASH -- B. Schmidt, DESY 10:20-10:50 Investigation of Microbunching Instability at the SCSS test accelerator -- K. Togawa, SPRING-8 10:50-11:40 Discussion & Coffee Service 11:40-12:10 Studies of fragmentation in electron beam energy spectra at SDL - T. Shaftan, BNL Laser pulse shaping and beam structures at SDL -- S. Seletskiy, BNL 12:10-12:40 COTR and SASE from Compressed Beams -- A. Lumpkin, FNAL

11 Program Session II - Theory and Simulation 14:00-18:00 Chairs: A. Zholents (pre-break) & G.Stupakov (post-break) 14:00-14:30 Overview and Recent Progress in ubi Theory and Simulation S. DiMitri, Trieste 14:30-15:45 Contributed talks on ubi Theory and Simulation: Modeling ubi Growth in the SPARX Configurations, C. Vaccarezza, INFN/Roma Nonlinear Correction to the Gain of the Microbunching Instability Seeded by Shot Noise, M. Venturini, LBNL Large-Scale Simulation of Microbunching Instability in the Berkeley FEL Linac Studies, J. Qiang, LBNL A Vlasov-Maxwell Solver to Study Microbunching Instability in the FERMI@ELETTRA First Bunch Compressor System, G. Bassi, Daresbury; J. Ellison, UNM; K. Heinemann 16:45-17:20 Contributed Talks on ubi Simulation + Modeling Existing Experiments: Wisconsin FEL Bunch Compressor Modeling, R. Bosch, U. Wis. Accelerator Design Concepts and Simulation Issues Relevant to the Microbunching Instability, Y. Kim, PSI Unrecognized Singularity in the Field of a 1-D Evolving Bunch, R. Warnock, SLAC LSC Microbunching from Shot Noise and Comparison with LCLS Results, D. Ratner

12 Program Session III - Cathode, Laser, & Injector Physics Relevant to ubi Initialization & Growth 9:00-12:30 Chairperson T. Limberg 9:00-9:30 Cathode Emission Physics and Origins of Non-uniformity K. Jensen, NRL 9:30-10:00 Laser Photocathode Physics & Observations Relevant to μbi -- D. Dowell, SLAC 10:00-10:30 Post-cathode Dynamical Evolution of E-beam Non-Uniformities -- P. Piot, NIU/Fermilab 11:15-12:30 Contributed talks on ubi Initialization & Growth in Cathode/Injector Regions: Possible Sources of Non-Uniform Emission,no, Velocity Bunching!, M. Ferrario, INFN/Frascati 3D Study of Effects from Inhomogeneities upon the Minimum Achievable Emittance, M. Quattromini, NEA/Frascati Microbunching Instability in Velocity Bunching, D. Xiang, SLAC Simulation of Propagation of Cathode Region Modulations in the FERMI Injector, G. Penco & P. Craievitch, Sincrotrone Trieste

13 Program Session IV - Diagnostics & Control 13:30-17:45 Chairpersons, D. Dowell (pre-break) & M. Ferrario (post-break) 13:30-14:15 Current state-of-art in OTR physics & diag. setup R. Fiorito, U Md., & A. Lumpkin, FNAL 14:15-14:40 LCLS OTR setup and COTR studies H. Loos, SLAC 14:40-15:05 COTR observations at FLASH B. Beutner, PSI LCLS Laser Heater plans P. Emma, SLAC FERMI Laser Heater plans S. Spampinati, Sincrotrone Trieste 16:00-17:15 Contributed talks on Diagnostics and Control: E-beam High-Frequency Content on the Bunch Length Measurement and Longitudinal Feedback, J. Wu, SLAC Two Stage, Single Shot IR CTR Spectrometer, S. Wesch, DESY Compressing Electron Bunches with Solenoids, A. Zholents, LBNL COTR Mitigation with a Tilted OTR Foil, G. Stupakov, SLAC 17:15-17:45 Discussion

14 Program Near-Term Future Plans at Different Labs 9:00-10:20 different labs including expt. verification/benchmarking of ubi theory & simulation, followed by open general discussion DESY FLASH & XFEL plans T. Limberg FERMI Plans -- Injector microbunching characterization using a low energy deflecting cavity BNL plans S. Seletskiy Frascati Plans - M. Ferrario ANL/FNAL Plans, A. Lumpkin Shanghai plans for ubi expt. studies Z. Huang, SLAC, speaking for D. Wong, Shanghai Microbunching Experimental Plans at the Upcoming PSI 250 MeV injector Y. Kim, PSI Daresbury Plans --- P. Williams

15 The LCLS COTR Problem OTR Screens downstream of dogleg not usable with design machine parameters No COTR Low gain COTR High gain COTR

16 Scanning the Dogleg Quad

17 The LCLS Laser-Heater P. Emma, for The LCLS Commissioning Team LBNL µ-bi Meeting Oct. 7, 2008 LCLS Layout and Design Status of Installation Commissioning Issues Experiments?

18 LCLS Injector Layout 6 MeV RF Gun Solenoid L0a L0b Gun Spectrometer Laser-Heater RF Deflector Commissioned Commissioned in in 0707 Emittance Screens/Wires OTR screens (7) YAG screens (7) Wire scanners (7) Dipole magnets (8) Beam stoppers (2) S-band RF acc. sections (5) Emittance Screen/Wires 2-km point in 3-km 3 SLAC linac 135-MeV Spectrometer L1S X-band RF acc. section BC1 TD11 stopper 135 MeV 250 MeV

19 LCLS Slice Energy Spread Tolerance FEL Power Gain Length FEL limit Σ Δf 10 4 ~40 kev at 1 nc operating point Z. Huang et al.,

20 The LCLS Laser Heater (135 MeV) suggested by Saldin et al.

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22 Laser Heater Simulations Z. Huang et al., FEL 04 Example of longitudinal phase space at 14 GeV with 8% initial modulation at 150-µm m modulation

23 Layout of the Laser Heater Optical System in the Laser Lab PH1 UV beam Waveplate & polarizer PC & polarizer Energy control PH2 Shutter Adjustment of the telescope changes the beam size in the heater-undulator Pulse 3 lens Stretcher Telescope To streak camera UV Conversion Unit IR Laser System to vertical transport tube Sasha Gilevich Path Length Adjuster

24 Layout of the Laser Heater Optical System in the Injector Vault 758 nm OTR screens e transport to the tunnel shutter VHC camera vacuum transport to LH MH4 photo diode MH3 wave plate MH4, MH3, MH2 - Motorized mirrors Sasha Gilevich power meter CH1 camera MH2 MH2 & MH3 are closed-loop loop control Waveplate and polarizer in front of both cameras

25 Injector Vault (Oct. 07) transverse RF deflector MeV booster linac RF gun (+ Dave) OTR screens & wire- scanners

26 Injector Vault (Oct. 08)

27 IR & UV Laser Vertical Transport in Vault

28 Laser Table in the Injector Vault

29 Laser Heater Table in the Vault MH3 VHC on motorized XY stage To powermeter CH1 WP CH1 WP VHC MH2

30 Laser Heater Table in the Vault From MH2 Waveplate To VHC MH1 50% beamsplitter

31 IR Beam at Center of Undulator ~Sep. 30, 2008

32 Matt Boyes Laser Heater Controls Panel

33 Damping of COTR? (1 nc, 40 kev rms heating) BC1: COTR suppression for: 2 2πσ E /E 0 R 56 >> λ 2π(40 kev)/(250 MeV) (39 mm) = 39 µm m >> 1 µm BC2: COTR suppression for: 2 2πσ E /E 0 C 1 R 56 >> λ 2π(40 kev)/(4.3 GeV) 4.5(25 mm) = 7 µm m >> 1 µm similar numbers at 250 pc with σ E = 20 kev

34 RF Gun Solenoid L0a L0b Gun Spectrometer Laser-Heater RF Deflector Emittance Screens/Wires OTR screens (7) YAG screens (7) Wire scanners (7) Dipole magnets (8) Beam stoppers (2) S-band RF acc. sections (5) Emittance Screen/Wires 2-km point in 3-km 3 SLAC linac 135-MeV Spectrometer L1S X-band RF acc. section BC1 TD11 stopper 135 MeV 250 MeV RF Deflector (LOLA) + special lattice configuration in spectrometer allows fine measurement of time-sliced energy spread (to <6 kev) σ E 6 kev rms (40 μm)

35 Laser Heater Commissioning Schedule All laser-heater systems will be ready by Nov. 3, 2008, except the LH-undulator (magnet vendor was late) LH-undulator will be installed in Dec. or Jan. FEL begins commissioning in March (must have LH ready) Ideas for reasonably well thought out experiments are welcome laser heater commissioning There is not limitless time available. Pressures to establish FEL arise quickly after March 15, 2009.

36 LCLS Commissioning Status P. Emma, for The LCLS Commissioning Team LCLS SAC Meeting October 20, 2008 LCLS Machine Performance Estimated FEL Power Present Stability Ultra-Short Pulse Possibilities

37 Linac Coherent Light Source at SLAC X -FEL based on last 11-km -km of existing linac X-FEL Injector (35º) at 2-km point Å Existing 1/3 Linac (1 km) (with modifications) New e Transfer Line (340 m) X-ray Transport Line (200 m) Undulator (130 m) Near Experiment Hall Far Experiment Hall

38 LCLS Accelerator Layout 6 MeV 135 MeV 250 MeV σ z 0.83 mm σ z 0.83 mm σ z 0.19 mm σ δ 0.05 % σ δ 0.10 % σ δ 1.6 % Linac-0 L =6 m rf gun L0-a,b Linac-1 L 9 9 m rf 25 ϕ rf Linac-X L =0.6 m rf = 160 ϕ rf Linac-2 L 330 m rf 41 ϕ rf 4.30 GeV σ z mm σ δ 0.71 % Linac-3 L 550 m rf 0 ϕ rf 13.6 GeV σ z mm σ δ 0.01 % beam parked here...existing linac DL1 L 12 m R b,c,d X BC1 L 6 6 m mm R 56 Commission Mar-Aug b 24-6d SLAC linac tunnel 25-1a undulator 30-8c BC2 L =130 m L 22 m mm undulator DL2 L =275 m Aug 2008 Nov R R 56 Commission Jan-Aug 2008 X-rays in spring 2009 research yard

39 Phase-II Commissioning Highlights (2008) Injector Commissioning: Apr-Aug, 2007 (DONE) Phase-II Commissioning: Dec-Aug, 2008 (DONE) Great drive-laser uptime (99%) and good performance Projected emittances μm at 0.25 nc, 10 GeV Routine 30-Hz e to 14 GeV (~24/7 with ~90% up-time) Bunch compression fully demonstrated down to 1-2 µm Many beam & RF feedback systems running well Electron bunch appears bright enough to drive 1.5-Å FEL 20-pC bunch with 0.14-µm emittance (& ~10 fs length?)

40 Laser Spatial and Temporal Shaping in R = 1.4 mm ps Spatial shape on cathode using iris Temporal shape (6.6 ps FWHM) 99% Drive Laser up time! S. Gilevich, G. Hays, P. Hering, A. Miahnahri, W. White

41 Design and Typical Measured Parameters (Aug. 2008) Parameter Final linac e energy symbol design measured unit γmc MeV Bunch charge Q nc Initial bunch length (rms) Final bunch length (rms) Projected emittance (injector) Slice emittance (injector) Projected emittance (linac end) z mm μm σ z0 σ zf 20 γε x,y μm γε s x,y μm γε L x,y μm Single bunch repetition rate f Hz RF gun field at cathode E g MV/m Laser energy on cathode u l μj Laser diameter on cathode 2R mm Cathode quantum efficiency QE

42 Projected Emittance <1.2 μm at 1 nc (135 MeV) γε x = 1.07 μm meets meets injector injector goals goals OTR screen 95% area cut Gaussian overlay not used γε y = 1.11 μm

43 Bunch Compression & CSR Measured after BC2 (0.25 nc) nominal σ z < 5 μm σ z 2 μm old screen used σ z > 25 μm L2 BC2 (4.3 GeV) TCAV (5.0 GeV) 550 m 4 wires BSY (14 GeV)

44 Laser & Electron-Based Feedback Systems Transverse Loops Stabilize: Laser spot on cathode Gun launch angle Injector trajectory X-band cavity position Linac trajectory (2) Undulator traj. (future) Laser Longitudinal Loops Stabilize: DL1 energy BC1 energy BC1 bunch length BC2 energy BC2 bunch length Final energy BPMs CER detectors Steering Loop gun V 0 δ 0 σ z1 σ z2 L0 L0 δ 1 δ 2 δ 3 ϕ 1 V 1 ϕ 2 V 2 V 3 D. Fairley, J. Wu L1 X L2 L3 DL1 BC1 BC2 DL2

45 Bunch Length & Energy Feedback Systems DL1 energy BC1 energy Mesh Filter Mesh Filter Mesh Filter Paraboloid Paraboloid Paraboloid Beam Splitter Beam Splitter Beam Splitter 0.03% rms BC2 energy 0.05% rms Final e energy Pyro Detector Pyro Detector Pyro Detector CSR-based bunch length monitor Charge feedback: Edge Radiation Edge Radiation Edge Radiation Beam Beam Beam Q = 0.25 nc 0.09% rms 0.03% rms bunch charge ΔQ 2 1/2 /Q = 1.5% 216 ± 12 A 2170 ± 217 A BC1 peak current BC2 peak current

46 Normalized phase space centroid jitter after BC1 (~4% of rms beam size) RMS A xn = 3.9% RMS A yn = 3.4% 1-σ beam size Stability is not so far from our goal (~10%) D. Ratner near end of linac (10-15% 15% of rms beam size) RMS A xn = 14% RMS A yn = 9% Thanks to Controls group for new BPM electronics! Q = 0.25 nc ΔE/E jitter 0.03% ΔQ/Q jitter 1.5%

47 Measuring Bunch Arrival Time Jitter e Q = 0.25 nc S-band (2856 MHz) V(t) BPM slope = 2.34 mm/deg BPM Y Position (mm) Now measure BPM jitter both with transverse RF OFF, and then ON (at constant phase) TCAV OFF TCAV ON Δt ±0.6 ps 9 μm m rms 110 μm m rms Timing Jitter (w.r.t. RF) = (110 μm)/(2.34 mm/deg) = deg 46 fsec rms

48 Emittance Near End of Linac Over Long Weekend γ(ε x ε y ) 1/2 = 1.04 μm long weekend run at 0.25 nc with no tuning (3.3 days) May 24, :01 to May 27 09:00

49 Beam Appears Bright Enough for FEL Saturation at 0.15 nm M. Xie method, with wakes FEL FEL Power Power 3D 3D Gain Gain Length Length Calculation based on measured end-of of-linac projected emittance values, measured peak current, and design undulator parameters (assuming undulator alignment and 0.01% rms slice energy spread not yet measurable)

50 Time-sliced x-emittance at Very Low Charge 0.14 µm TAIL (not same data) 20 pc, 135 MeV, 0.6-mm spot diameter, 400 µm m rms bunch length (5 A) Also measured at 0.6 µm m at 250 pc & 1.2-mm laser spot diameter (40 A)

51 Measurements and Simulations for 20-pC Bunch at 14 GeV σ z 1 μm m? LiTrack (no CSR) 8 ka? Photo-diode signal on OTR screen after BC2 shows minimum compression at L2-linac phase of deg. SIMULATED FEL PULSE 1.5 Å, photons I pk = 4.8 ka γε 0.4 µm Y. Ding Horizontal projected emittance measured at 10 GeV, after BC2, using 4 wire-scanners. LCLS FEL simulation at 1.5 Å based on measured injector beam and Elegant tracking, with CSR, at 20 pc.

52 z = 25 m Simulated 20-pC Bunch at 4.3 GeV: Approaching a Single Longitudinally Coherent Spike (power profile at z = 25 m varies from shot to shot due to noisy startup) 15 Å, z = 25 m, photons, I pk = 2.6 ka, γε 0.4 µm 1.2 fs Y. Ding LCLS FEL simulation at 15 Å based on measured injector beam and Elegant tracking, with CSR, at 20 pc.

53 2-Pulse Production with 2 slots 0.25 mm 0-66 mm 10 pulses not coherent fs LCLS BC2 bunch compressor chicane Power (GW) fs time (fs)

54 LCLS Installation and Commissioning Time-Line PEP-II run ends LTU/Und/Dump Install now PPS Cert. LTU/Dump FEE/NEH Install Und. Seg. Install First Light in FEE X-Rays in NEH FEH Hutch BO FEH Install First Light in FEH CD-4 (7/31/2010) JJ F M A M J J A S ON D J F M AM A M J J A S O N D J F M A M J J 2008 Down PPS Linac/BC2 Commissioning Re-commission Inj/BC2 to SL2 LTU/Und Comm. FEE Comm. NEH Operations/ Commissioning May 2, 2008