Swiss FEL Beam Dynamics Commissioning Group Sven Reiche

Swiss. FEL Beam Dynamics & Commissioning Group Sven Reiche – BK-Meeting 1. 4. 2011

The Beam Dynamics Group • • • Swiss. FEL Sven Reiche (Staff Scientist) – FEL Dynamics, Swiss. FEL Layout Frederic Le. Pimpec (Staff Scientist) – Collimator, Cathode Issue Bolko Beutner (Staff Scientist) – RF Tolerances, Bunch Compression, Emittance Measurement (FODO) Eduart Prat (Post. Doc) – EEHG Seeding, Emittance Measurement (Triplett), Transverse Optics Simona Bettoni (Post. Doc) – RF Gun, Emittance Compensation Potential addition within the next few months • • Sakhorn Rimjaem (GFA Fellowship) – Injector Commissioning, Bunch Compression Mark Guetg (Ph. D. Student) – Ultrawide Bandwidth Mode, Electron Slice Centroid Alignment 2 Sven Reiche – BK-Meeting 1. 4. 2011

Tools (Example 250 Me. V) Swiss. FEL Dipole Quadrupole Deflector 1 BPM+Screen bloks Deflector 2 1 cell S-band acc. structures FINSB 01 FINSB 02 FINSB 03 FINSB 04 5 cells X-band cavity Screen FINXB Compression FODO Cells RF gun FINSS Diagnostic section Astra, OPAL, Homdyn FEL: • Genesis MADX, Elegant Synergies: • Astra/CSRTrack • MADX/Elegant • Elegant/Genesis CSRTrack Astra, OPAL 3 Sven Reiche – BK-Meeting 1. 4. 2011

Swiss. FEL Design 4 Swiss. FEL Sven Reiche – BK-Meeting 1. 4. 2011

Injector Operation Swiss. FEL • All beam dynamic people are running shifts at the 250 Me. V injector • Development of procedures for measurements and operation of the injector: 1. Prototype measurements (single person expert interface) 2. Matlab interfaces (expert interface) 3. Integration in the control system by Controls Group (operator interface) • Current working places: – Beam Based Alignment + Transverse Feedback – Optics Measurements – Emittance Measurements – BC Configuration + Longitudinal Feedback – Online Model 5 Sven Reiche – BK-Meeting 1. 4. 2011

Emittance Measurement Swiss. FEL • Currently evaluating the preferred method to measure emittance: – FODO lattice: passive measurement with unchanged optics (B. Beutner) – Triplet quad scan: compact design with only one screen (E. Prat) 6 Sven Reiche – BK-Meeting 1. 4. 2011

Optics Measurement (in Development) Swiss. FEL • Cannot rely on FODO lattice for Swiss. FEL (matching has to be done in laser heater in Swiss. FEL) • Requires robust method with minimal diagnostics requirements • Masamitsu’s beamsize-free optics measurement • Still needs to be developed into a robust operator tool 7 Sven Reiche – BK-Meeting 1. 4. 2011

Online Model (in Development) Injector Specification (Holy List/CITI-DB) Injector Setvalues (EPICS) Lattice Generator Machine Calibration Swiss. FEL Beam Parameters (Charge, Emittance) Measurements Online Model Creation of injector model instance Input Generation Execution Output Analysis Access by API Work done by Masamitsu, currently using MADX for development. Elegant easy to implement, others will follow Operator Request 8 Sven Reiche – BK-Meeting 1. 4. 2011

Seeding Experiment BPM Profile monitor Swiss. FEL Courtesy of M. Pedrozzi and E. Prat Dipole magnet HHG 50 nm laser 260 nm seed laser (Ti Saph) U 40. Modulator 1 Ku= 1. 45, λu=40 mm (10 periods) U 15. Radiator Ku=0. 81, u=15 mm 4 m (266 periods) U 40. Modulator 2 Ku = 1. 45, u=40 mm (10 periods) Lattice unchanged up to the transverse deflector EEHG scheme implemented in 2. 5 FODO cells FODO period has been increased from 3. 0 m to 3. 2 m due to space constraints Vacuum chamber squeezed down to 8 -10 mm (same as Swiss. FEL) • Design to be finalized soon (E. Prat) • Guided by high “re-usability” of beam line elements in Swiss. FEL • Implementation foreseen for 2013/2014 (if not cancelled ) 9 Sven Reiche – BK-Meeting 1. 4. 2011

Work in Progress - Swiss. FEL Optics & Layout Bunch compression: Cross-check of our current optimization with the optimization strategy of DESY for the XFEL Optimization of matching section: Calculation of acceptance in beta and alpha for the various matching sections and a possible re-optimization of quadrupole number and position Optimized Optics for bunch compression: Best matching of optical function through BC 1 and 2. Kicker/Septum Design: Layout for the kicker and matching strategies New Layout of Swiss. FEL: Generation of the proto-Holy List New Operation Point: Studies for BC at 2. 5 Ge. V and switchyard right after Laser Heater Specs: Design of laser heater and laser requirement Projected Emittance Optimization: Mitigation of beam tilt/rotation in bunch compressor due to CSR with quadrupoles and sextupoles Athos seeding beam line: Optimization of the Athos beamline post switchyard, starting from the initial design Energy tuning of Athos: Replacement of the C-band deflecting cavity with C-band accelerating structures for fast energy tuning and removal of residual energy chirp Non-linear beam elements: Correction of non-linear compression in BC 1 and BC 2 with sextupoles and octupoles and a possible replacement for the X-band cavities Working point of BC 1: Study alternative working point of BC at 250 Me. V with only 4 S-band structures in the booster linac Tolerances Magnet fabrication and alignment tolerances: RF Tolerances for 200 p. C: Basic tolerance studies RF Tolerances for 10 p. C: Following the same tolerance calculation for the 10 p. C case, which has somehow less compression but is more sensitive to peak current fluctuation. RF Tolerances at large BW Mode: Studies for overcompressed bunch RF Tolerances for ultra-compressed mode: Studies for final compression in the energy collimator 10 Sven Reiche – BK-Meeting 1. 4. 2011

Work in Progress - Swiss. FEL Operational Aspects Quadrupole Sensitivity: Dependence of mismatch parameter for variations in quadrupole strength and a possible reoptimization to mitigate quadrupole strength Collimator design for Aramis: Layout and Performance/Acceptance of transverse and energy collimator. Collimation criteria for energy collimator. Collimation design for Athos: Layout and Performance/Acceptance of transverse and energy collimator. 2 Bunch operation: Tracking of second electron bunch including long-range wakefields, RF phase errors and error in RF deflector and septum magnet. Review of Diagnostic Configuration: Optimization of location and type of diagnostic with respect to expected performance (e. g. optimum screen position to measure optical functions) Tracking of optical function in linac 1 for 3. 4 Ge. V optics but 2. 1 Ge. V electron beam: Study of injecting a 2. 1 Ge. V into the Athos beam line with quads matched for 3. 4 Ge. V Dark current: Tracking of dark current along the machine, following the DESY approach to study radiation levels and beam losses along the linac. Orbit Correction: Strategy of implementing orbit correction into the control system Compression Stabilization: Strategy for a longitudinal feedback system and performance analysis Beam optics decoupling: Requirements for skew quadrupoles in linac due to coupled betatron motion by rolled dipoles in BC 1 and BC 2 Beam Optics: Strategy to measure beam optics function (e. g. orbit response matrix) Collective Effects + Instabilities Gain curve for microbunch instability: Growth of an initial current modulation and mitigation with the laser heater. Specification for the laser heater requirement (pulse energy etc) Fully consistent space charge calculation: Start to end simulation with Astra/Opal and CSR Track, following the DESY approach (They see significant difference in low charge mode) Sextupole Kick from Quadrupole Correctors: Tolerance for field strength of corrector magnets Undulator Wakefield Optimization: Calculation of undulator wakefield and optimizing diameter of intra-module vacuum chamber Wakefield in main linac: Total wakefield budget in linac (RF cavities, aperture changes etc. ) Wakefield in Athos beamline: Deliberately induced wakefields to remove residual energy chirp of electron beam 11 Sven Reiche – BK-Meeting 1. 4. 2011

Work in Progress - Swiss. FEL FEL Performance SASE Simulation for 4 modes of operation: Definition of design values, comparison with start-end results Coherence properties: Analysis of the transverse and longitudinal coherence and calculation of the illumination function for Aramis at 1 and 7 Angstrom Gap Tolerance: Study of gap variation within a module with a harmonic analysis and a realistic model. Undulator wakefield: Study of undulator wakefields with refined undulator module design and the compensation with taper Undulator Taper: Optimizing of taper and efficiency enhancement Undulator Driftsection: Studies of effect of driftlengt on FEL performance mainly for slippage reasons Point Stability: Translation of Laser jitter from electron beam jitter Phase Interface: Propagation of wavefronts from Genesis to user station 12 Sven Reiche – BK-Meeting 1. 4. 2011

Work in Progress - Injector Swiss. FEL 250 Me. V Injector Simulation support for commissioning: Cross check with measurement during commissioning (e. g. envelope along the machine) Matching strategy for the X-band section and post BC section: Finding a matching strategy rather than relying on the static quadrupole values from Y. Kim Online Model: integration of optics model into the control system and calibration of quadrupole currents with focusing strength of quadrupoles (k-values), similar to optics toolbox at DESY Phase 4 seeding beamline: New design of seeding beamline with a possible regular FODO lattice to allow both seeding and emittance measurement Start-end Simulation: Consistent start-end simulation, including space charge, using ASTRA/OPAL and CSR Track Emittance Measurement in Phase 2: Using the X-band triplet, study of performance of a possible emittance measurement Performance of diagnostic section: Emittnce measurement with the given non-optimal phase advance and a possible symmetric FODO lattice. Transverse Shaping of laser profile and electron beam: Effect of transverse shape on emittance Longitudinal Shaping of laser profile and electron beam: Effect on emittance Laser Tolerances: Study of tolerance in longitudinal and transverse uniformity Simulation support for diagnostic: Performance of diagnostic components (e. g. transverse deflector, slit scan with long transport distances) Gun model for the injector: Reference model for Astra/Opal. Gaining expertise in gun modeling and optimization Irregular beam distribution: emittance degradation by asymmetric laser spot size and irregular quantum efficiency with 3 D code Astra/Opal. BC Optimization: Optimization of optical function to minimize emittance degradation in bunch compressor Orbit Correction: Implementation into the control system Longitudinal Feedback: Development of a longitudinal feedback for the bunch compressor. RF Stability: Analysis of current fluctuation with full compression to measure RF stability Optics measurement: Strategy to measure the optical function with orbit response measurement, mismatch in FODO channel etc. Halo Simulation: Generation of Haloes due to different beam profiles. 13 Sven Reiche – BK-Meeting 1. 4. 2011