Transcript E-XFEL Intra-bunch train feedback
Paul Scherrer Institut
The European XFEL Intra Bunch Train Feedback
Boris Keil For the PSI E-XFEL Team Paul Scherrer Institut Boris Keil, PSI DEELS Workshop 2014 DEELS Workshop 2014
E-XFEL IBFB Overview
IBFB
Daisy-Chain 2 of BPM Units
SASE 2 LINAC
IBFB Upstream BPM Pickups IBFB Kicker Magnets (Horizont. & Vertical)
H1 V1 H2 V2
IBFB Downstream BPM Pickups e-beam - - - - - - - - - - - Analog Signals (Coax Cables) - - - - - - - - - Daisy-Chain 1 of BPM Units
SASE 1 IBFB Electronics
Digital Signals (Duplex Fiber Optic Cables)
• Low-latency (~1μs) beam position correction upstream of beam distribution.
• Can kick each bunch individually, using feedback + feed-forward algorithm.
• Uses undulator BPM data (latency 5-10μs) for fine-tuning of undulator orbit (to correct kicks between IBFB and undulators: Vibrations, distribution kicker, ...).
Boris Keil, PSI DEELS Workshop 2014 13.5.14
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Transverse Perturbations
• IBFB kickers should provide enough kick to correct perturbations, plus reserve.
• IBFB removes perturbations, but also adds noise to the beam (dominated by BPMs): Noise should not have negative impact on FEL performance → Low-noise BPMs (goal: <1μm RMS). Pickups: 3.3GHz cavity, same as TL.
• Feedback loop latency <1.5μs expected to be sufficient.
Spurious dispersion and 3% chirp Nonlinear dispersion and 3% chirp Spurious dispersion and 1e -4 energy jitter Nonlinear dispersion and 1e -4 energy jitter Wake fields Kicker Drift Kicker Jitter Quad Motion Power Supply Jitter Dispersion jitter Total kick x eff [μm] 15 15 0.5 0.15 25 0 1 28 12.6 2.5 Max. Freq. 1 kHz 1 kHz 1 kHz 1 kHz 5 MHz 1 kHz 5 MHz 10 Hz 10 Hz 10 Hz Plane x/y x x/y x x/y x x x/y x/y x/y Pertur bation Type repetitive repetitive random random repetitive repetitive random random random random X Kick [μrad] ±0.5 ±0.5 ± 0.01 ± 0.003 ±0.8 ±0 ± 0 ± 1.0 ± 0.4 ± 0.1 ±3.3 Y Kick [μrad] ±0.5 ±0 ± 0.01 ± 0 ±0.8 ±0 ± 0.03 ± 1.0 ± 0.4 ± 0.1 ±2.8
*Worst-case estimate (DESY), 30m beta function at kicker & BPM, adding of peak values.
Boris Keil, PSI DEELS Workshop 2014 13.5.14
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IBFB Kicker Magnet
• 50 Ohms stripline kicker (picture shows cut / only half).
• Kicker design by PSI (based on CTF3/Daphne design by F. Marcellini et al., INFN Frascati), supported by DESY (wakefield simulations, M. Dohlus).
• Tapered 2m long strips.
• Wakefield simulations: Kicker vessel needs no taper.
• Prototype built by company COMEB, RF test successful.
• DESY uses modified version (aperture, ...) for dump kickers.
Flexible RF feedthrough Ceramic spacers & RF feedthroughs allow thermal expansion of strip relative to vessel (bakeout, tolerances, ...) 3 DESY standard steel flanges Boris Keil, PSI Aluminum vessel and strips (low weight, easy to fabricate) DEELS Workshop 2014 13.5.14
IBFB Kicker: S-Parameters
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IBFB Kicker: Diff. Impedance
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Kicker Positions & Beam Optics
Baseline: 4 Kickers of 2m length for IBFB.
Reserved space for upgrade: Double number of kickers and max. kick 6 Dump kickers Boris Keil, PSI DEELS Workshop 2014 13.5.14
IBFB Kickers: RF Power Amps
• Commercial amplifiers from Company TOMCO (class AB solid state).
• Improved at request of PSI: Redundant power supply & amp modules to maximize MTBF.
• Two amplifiers purchased & tested extensively: Meet PSI specifications.
• Kick: > ±4μrad baseline (4 kickers), > ±8μrad upgrade (8 kickers).
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IBFB Kickers: RF Power Amps
TOMCO guarantees 3kW pulse power, but amp reached 6kW!
Prototype test at PSI: IBFB will most likely use 18MHz amplitude-modulated sine or square wave.
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IBFB Kickers: RF Power Amps
9 Droop of kick voltage over bunch train (thermal effects in MOSFETs, ...): IBFB digital electronics will compensate droop 13.5.14
Boris Keil, PSI DEELS Workshop 2014
IBFB: Electronics Topology
downstream BPMs undulator BPMs upstream BPMs RFFE1 6xADC 16-bit FPGA1 RFFE2 6xADC 16-bit P0 FPGA2 GPAC1 RFFE3 6xADC 16-bit FPGA3 RFFE4 6xADC 16-bit P0 FPGA4 GPAC2 RFFE5 6xADC 16-bit FPGA5 RFFE6 6xADC 16-bit P0 FPGA6 GPAC3 Feedback/Feed forward algorithm: Same FPGA board as BPMs, but with 0.5-1GSPS DAC mezzanine to generate kicker waveforms FPGA7 P0 32GFLOPS DSP PDC FPGA8 6xADC 16-bit 4xDAC 14-bit to kicker amplifiers Boris Keil, PSI DEELS Workshop 2014 13.5.14
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IBFB: Algorithm
K1x Pfor K2x Pfor ADC, position, angle, control ...
Data Acquisition kicker signal from y plane kicker signal from x plane Timing Control Kicker Linearization x-y Plane Decoupling Control & Status Registers + kicker signal Position & Angle Calculation x 1 x ’ 2 x 2 Position & Angle Calculation Feedback Kicker Control x 3 x ’ 4 x 4 Position & Angle Calculation DDR2 SDRAM QDR2 SRAM from/to control system RIO Link Processor Local Bus (PLB) Adaptive Feed Forward Table Ebeam Lattice Transfer Matrices Adaptive Feed Forward Algorithm x 5 x ’ 5 x 6 • Ultra-fast feedback removes random perturbations, e.g. beam offset of whole bunch train due to mechanical vibrations etc.
• Adaptive feed-forward corrects reproducible perturbations that are the same for each bunch train (or change very slowly).
• IBFB can use same FPGA carrier board as BPMs. Present version (Xilinx Virtex-5 FPGA, PowerPC) sufficient, new version (Artix-7/Kintex-7 FPGAs + DSP) under development, will simplify development of more complex algorithms for future operating modes.
Boris Keil, PSI DEELS Workshop 2014 13.5.14
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IBFB: Cavity BPM Pickups
Transfer Line Cavity BPM
• 3.3GHz, 40.5mm aperture.
• Used for: Transverse intra-train feedback, energy measurements, launch jitter control & correction (energy, BAM, linac entry, …), optics measurements, …
Prototype at SwissFEL Injector Test Facility 255mm Similar to undulator type, slightly less resolution (~20%). Main differences: ~16x more angle signal (→ align 16x better), cavity spacing ( → crosstalk).
Frequency (both resonators) Loaded Q (both resonators, desired mode) Q (uncoupled modes) Sensitivity Thermal noise (lossless cables & electronics, …) Angle signal (90 ° to position signal. Cause: Misalignment) 3.3GHz
~70 typ. 200-300 2.5V/(nC*mm) 65nm @ 20pC ~16mm * dx/dz
D. Lipka DESY
Boris Keil, PSI DEELS Workshop 2014 13.5.14
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IBFB: Cavity BPM Electronics
New: 63dB range, 0.5dB steps RFFE MBU Crate: Removable fan tray, redundant main power supply, ...
13 Differential coax cabling from RFFE to ADCs • I/Q downconversion to baseband.
• Active temperature stabilization (several sensors + heaters).
• Works with or without external trigger & ref. clock.
DOOCS & Timing Interface (SFP/Optical, PCIe/Ethernet /..., up to 6.5Gbps) Boris Keil, PSI DEELS Workshop 2014 13.5.14
ADC Sample Clock Phase Feedback
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Digital ADC sampling clock phase alignment loop
• Eliminates phase drift effects • Retains maximal S/N ratio • Monitors possible reference signal malfunctions & beam arrival time changes
Present algorithm: Uses just one ADC sample at top to calculate beam position.
Boris Keil, PSI DEELS Workshop 2014 13.5.14
RFFE: Nominal vs. Measured Gain
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Gain Dependence of Phase Delay
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Cavity BPM ElectronicsTemp. Drift
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Temperature drift scales with beam offset. Active temperature stabilization active: <100nm/ °C drift at 1mm offset (0.01%/ °C)
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Boris Keil, PSI DEELS Workshop 2014
GUI For Automated Lab Calibration
18 • Presently using commercial RF generator (pulsed) for automated lab calibration (gain & phase delay for each attenuator setting; IQ imbalance, ...).
• Developing low-cost test/calibration system (external "customers", ...).
Boris Keil, PSI DEELS Workshop 2014 13.5.14
Position Calculation in BPM FPGA
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SwissFEL BPM Test Area
Correlation of 3 E-XFEL Undulator Cavity BPMs
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Sampled RFFE IQ Signals
Boris Keil, PSI
See IBIC’12, TUPA27, M. Stadler et al.
DEELS Workshop 2014
Only top sample used (so far ...), plus baseline subtraction Histogram (X1+X3)/2 – X2
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IBFB: Cavity BPM Performance
Position Noise (RMS, 1 Bunch) • Undulator cavity (Ø=10mm): ~11 μm @ 2pC ( ±5mm range) <0.5μm @ 100-1000pC ~1μm @ 100-1000pC ( ( ±1mm range) • Transfer line cavity (Ø=40.5mm): ±1mm range) 2x improvement feasible by digital removal of angle signal (15x bigger than for undulator BPMs) – work in progress ...
20mm offset at 1nC: 50V signal! RFFE may need input protection via attenuator (4x worse low-charge resolution), or extra protection circuit (to be developed for IBFB) Charge Measurement RMS Noise (1 Bunch) • Undulator cavity (Ø=10mm): <0.06% @ 100-1000pC <60fC @ 100pC <10fC @ 2pC Boris Keil, PSI DEELS Workshop 2014 13.5.14
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IBFB Status
IBFB BPMs (Will Dominate IBFB Performance ...) • Using standard E-XFEL cavity BPM electronics (maybe with external RFFE input protection circuit (1nC & big beam offsets ...), necessity being investigated).
IBFB (Non-BPM) Electronics Hardware • Can use BPM FPGA carrier board also for IBFB signal processing.
• DAC mezzanine to driver kicker amps under development.
IBFB Firmware/Software • Feedback/Feed-forward algorithm & feedback network via multi-gigabit fiber optic links to be implemented (re-using building blocks from BPM firmware/software).
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Team & Acknowledgements
PSI:
• M. Stadler
(Cavity BPM RF front-end)
• M. Roggli, M. Gloor
(ADC/DAC Mezzanine)
• R. Baldinger, D. Engeler
(FPGA carrier board HW)
• G. Marinkovic, W. Koprek
(Firmware & software)
• C. Beard, F. Marcellini, M. Rohrer, D. Treyer,
(IBFB kicker magnet & RF power amps)
DESY:
• S. Vilcins, D. Lipka, D. Nölle
(Cavity BPM pickup)
• M. Dohlus
(Kicker wakefield simulations)
• N. Golubeva, W. Balandin, W. Decking
(Magnet lattice & beam optics) ... and all other supporters at PSI & DESY/E-XFEL
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Paul Scherrer Institut
Boris Keil, PSI
Thank you for your attention!
DEELS Workshop 2014 13.5.14