Start-to-End Simulation of Beam Dynamics in SASE FELs M. Borland¹, Y.-C. Chae¹, P. Emma², J.W. Lewellen¹, V. Bharadwaj², W.M. Fawley³, P. Krejcik², C. Limborg², S.V. Milton¹, H.-D. Nuhn², R. Soliday¹, M. Woodley² ¹Argonne National Laboratory ²Stanford Linear Accelerator Center ³Lawrence Berkeley National Laboratory Start-to-End Simulation of Beam Dynamics in SASE FELs May 6, 2002 M. Borland
� � � ✁ ✁ � Outline Why do start-to-end (S2E) simulations? Simulation methods and codes LCLS simulations Discovery of the CSR microbunching instability Simulation of pulse-to-pulse X-ray output Conclusions and suggestions Start-to-End Simulation of Beam Dynamics in SASE FELs May 6, 2002 M. Borland
Simplified SASE FEL Schematic undulator drive laser linac linac rf gun bunch compressor Start-to-End Simulation of Beam Dynamics in SASE FELs May 6, 2002 M. Borland
spatial and temporal pulse shape undulator drive laser linac linac rf gun wakes & wakes & bunch emittance rf curvature rf curvature compressor energy spread space charge, aberrations, energy emittance comp, ISR, & CSR beta match & photoemission trajectory Start-to-End Simulation of Beam Dynamics in SASE FELs May 6, 2002 M. Borland
Simplified SASE FEL Schematic power supplies Timing spatial and temporal pulse shape klystrons klystrons undulator drive laser linac linac rf gun wakes & wakes & bunch emittance rf curvature rf curvature compressor energy spread space charge, aberrations, energy emittance comp, ISR, & CSR beta match & photoemission trajectory FEL is critically affected by interplay of physics details. Start-to-End Simulation of Beam Dynamics in SASE FELs May 6, 2002 M. Borland
� � � ✁ ✁ ✁ Methodology of S2E Simulations Don't try to write a single code that does everything Do try to preserve as much information as practical in going from one code to the next Do develop a way to use existing codes together efficiently Standardized file format ("SDDS") for data exchange Standardized data processing tools (SDDS toolkit) Script-based automation Start-to-End Simulation of Beam Dynamics in SASE FELs May 6, 2002 M. Borland
� ✁ � ✁ ✁ ✁ ✁ � Codes for S2E PARMELA (L. Young, LANL) Photoinjector simulations Space charge, rf curvature, nonlinear transport elegant (M. Borland, ANL) Linac and bunch compressor CSR, ISR, wakefields, rf curvature, nonlinear transport GENESIS (S. Reiche, UCLA) 3D FEL simulation Start-to-End Simulation of Beam Dynamics in SASE FELs May 6, 2002 M. Borland
� � � � � ✁ GENESIS simulations Full time-dependent simulation requires millions of particles and is impractical for jitter simulation FEL codes and accelerator codes require very different particle loading Our solution Perform slice analysis with 136 slices ( ) L slice L slippage Simulate each slice independently in steady-state mode Start-to-End Simulation of Beam Dynamics in SASE FELs May 6, 2002 M. Borland
Components of S2E Simulations Photoinjector SDDS file: PARMELA Translator run parameters & phase-space L. Young (LANL) J. Lewellen (ANL) SDDS Toolkit Graphics Analysis Borland et al (ANL) Start-to-End Simulation of Beam Dynamics in SASE FELs May 6, 2002 M. Borland
Components of S2E Simulations Linac/Bunch Compressors Photoinj. elegant Linac phase-space phase-space file file M. Borland, ANL SDDS Toolkit CSR wakes simple FEL Graphics evaluation slice analysis moments vs Analysis vs distance distance Borland et al (ANL) Start-to-End Simulation of Beam Dynamics in SASE FELs May 6, 2002 M. Borland
Components of S2E Simulations FEL Simulation Start-to-End Simulation of Beam Dynamics in SASE FELs May 6, 2002 M. Borland
LCLS Schematic 06Dec00 Design (P. Emma) 4.54 GeV 250 MeV 150 MeV 14.35 GeV σ z ≈ σ z ≈ σ z ≈ 0.022 mm σ ≈ 0.83 mm 0.022 mm 0.19 mm z σδ ≈ 0.76 % σδ ≈ 1.8 % σ δ ≈ 0.10 % σδ ≈ 0.02 % RF gun L0 LX undulator ≈ L2 L3 L1 L 120 m BC1 BC2 DL2 R 56 ≈− 36 mm ≈− R 56 22 mm CSR simulations with gaussian beams and low longitudinal resolution predicted 5% projected emittance growth, but ... Start-to-End Simulation of Beam Dynamics in SASE FELs May 6, 2002 M. Borland
Emittance Growth in LCLS 06Dec00 Design requirement BC1 BC2 DL2 Emittance is average of values for 20 slices Start-to-End Simulation of Beam Dynamics in SASE FELs May 6, 2002 M. Borland
CSR Microbunching Instability 06Dec00 Design Microbunch spacing is ~3 µ m Power drops from ~15 GW to ~5 GW due to CSR instability Start-to-End Simulation of Beam Dynamics in SASE FELs May 6, 2002 M. Borland
� � � � � Explanation of the Instability CSR wake looks like the derivative of the longitudinal density Any density clump causes a local derivative-like feature in the CSR wake Head of clump is accelerated, tail is decelerated A particle that gains (losses) energy in a dipole falls back (moves ahead) Thus, the clump is amplified, which amplifies the CSR wake, ... Start-to-End Simulation of Beam Dynamics in SASE FELs May 6, 2002 M. Borland
Slice Analysis Start-to-End Simulation of Beam Dynamics in SASE FELs May 6, 2002 M. Borland
� � � � � Revised LCLS Design 07Nov01 Design (P. Emma) Replace double-chicane compressors with single-chicane compressors Add superconducting wiggler upstream of BC2 to increase incoherent energy spread Reduces size of current spikes generated in compression Reduces gain of CSR instability Reduced DL2 angles by 50% Start-to-End Simulation of Beam Dynamics in SASE FELs May 6, 2002 M. Borland
Emittance Growth in LCLS 07Nov01 Design requirement BC1 BC2 DL2 Emittance is average of values for 20 slices Start-to-End Simulation of Beam Dynamics in SASE FELs May 6, 2002 M. Borland
CSR Microbunching Instability 07Nov01 Design Power increases to ~7 GW Start-to-End Simulation of Beam Dynamics in SASE FELs May 6, 2002 M. Borland
Slice Analysis Start-to-End Simulation of Beam Dynamics in SASE FELs May 6, 2002 M. Borland
� � � � � � S2E Jitter Simulations of LCLS "Jitter" refers to any error that we can't correct with alignment, tuning, feedback, etc. We assume that the machine is tuned to ideal performance on average We simulated jitter, including drive laser timing and energy photoinjector and linac rf voltages and phases bunch compressor power supplies Start-to-End Simulation of Beam Dynamics in SASE FELs May 6, 2002 M. Borland
Assumed Input Jitter Levels Quantity Rms Jitter Quantity Rms Jitter Level Level laser phase 0.5 deg-S L2 phases (28) 0.07 deg-S laser energy 1.00% L2 voltages (28) 0.07% gun phase reference L3 phases (48) 0.07 deg-S gun voltage 0.1% L3 voltages (48) 0.05% L0 phase (1) 0.1 deg-S BC1 dipoles 0.02% L0 voltage (1) 0.10% BC2 dipoles 0.02% L1 phase (1) 0.1 deg-S DL dipoles 0.01% L1 voltage (1) 0.10% Wiggler dipoles 0.02% X-band phase (1) 0.3 deg-X Tweaker quads (4) 0.1% X-band voltage (1) 0.25% Start-to-End Simulation of Beam Dynamics in SASE FELs May 6, 2002 M. Borland
✁ ✁ ✁ ✁ ✁ ✁ ✁ ✁ ✁ ✁ ✁ ✁ � ✁ � � ✁ � Results of Jitter Simulations Correction Current Bunch Frac. Norm. x Gain Wavelength Power Quads length mom. emit. Length On Spread µ m 10 -4 kA ps m A GW yes 3.32 0.185 0.817 0.791 3.44 1.4991 7.1 0.18 0.013 0.043 0.012 0.16 0.0013 1.4 no 3.27 0.188 0.806 0.789 3.53 1.4987 6.6 0.17 0.013 0.033 0.011 0.13 0.0012 1.0 Correction quads in chicanes remove dispersion-like correlations due to CSR and reduce projected emittance. 230 seeds used. Values are medians of central-80% core-slice-averages. Error bars give half the quartile range. Start-to-End Simulation of Beam Dynamics in SASE FELs May 6, 2002 M. Borland
Results of Jitter Simulations Centroid jitter results in more power jitter All quantities are core-slice averages Start-to-End Simulation of Beam Dynamics in SASE FELs May 6, 2002 M. Borland
Results of Jitter Simulations Beam current jitter is highly correlated with power variation All quantities are core-slice averages Start-to-End Simulation of Beam Dynamics in SASE FELs May 6, 2002 M. Borland
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