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Boris Keil, PSI DEELS Workshop 2014 13.5.14
The European XFEL Intra BunchTrain Feedback
Boris Keil For the PSI E-XFEL Team
Paul Scherrer Institut
Paul Scherrer Institut
13.5.14DEELS Workshop 2014
Boris Keil, PSI DEELS Workshop 2014 13.5.14
2E-XFEL IBFB Overview
SASE 1
e-beamLINAC
SASE 2
Digital Signals (Duplex Fiber Optic Cables)
- - - - - - - - - - - Analog Signals (Coax Cables) - - - - - - - - - -
IBFB UpstreamBPM Pickups
IBFB Kicker Magnets(Horizont. & Vertical)
IBFB DownstreamBPM Pickups
V1H1 H2 V2
IBFB Electronics
Daisy-Chain 2 of BPM Units
Daisy-Chain 1 of BPM Units
IBFB
• 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
3
*Worst-case estimate (DESY), 30m beta function at kicker & BPM, adding of peak values.
• 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.
Transverse Perturbations
Boris Keil, PSI DEELS Workshop 2014 13.5.14
4
• 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.
Aluminum vessel and strips (low weight, easy to fabricate)
DESY standard steel flanges
Ceramic spacers & RF feedthroughs allow thermal expansion of strip relative to vessel
(bakeout, tolerances, ...)
IBFB Kicker Magnet
Flexible RF feedthrough
Boris Keil, PSI DEELS Workshop 2014 13.5.14
5IBFB Kicker: S-Parameters
Boris Keil, PSI DEELS Workshop 2014 13.5.14
6IBFB Kicker: Diff. Impedance
Boris Keil, PSI DEELS Workshop 2014 13.5.14
7
Dump kickers
Baseline: 4 Kickers of 2m length for IBFB.
Reserved space for upgrade: Double number of kickers
and max. kick
Kicker Positions & Beam Optics
Boris Keil, PSI DEELS Workshop 2014 13.5.14
8
• 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).
Two AmplifiersTwo Amplifiers
IBFB Kickers: RF Power Amps
Boris Keil, PSI DEELS Workshop 2014 13.5.14
9
Prototype test at PSI: IBFB will most likely use 18MHz
amplitude-modulated sine or square wave.
TOMCO guarantees 3kW pulse power, but amp reached 6kW!
IBFB Kickers: RF Power Amps
Boris Keil, PSI DEELS Workshop 2014 13.5.14
10
Droop of kick voltage over bunch train (thermal
effects in MOSFETs, ...):IBFB digital electronics will
compensate droop
IBFB Kickers: RF Power Amps
Boris Keil, PSI DEELS Workshop 2014 13.5.14
11
GPAC3
6xADC 16-bit
BP
M6x
BP
M6y
BP
M6r
K1x
K2x
FPGA6
P0
RIO
RIO
RFFE6
6xADC 16-bit
BP
M5x
BP
M5y
BP
M5r
FPGA5
RFFE5
GPAC2
6xADC 16-bit
BP
M4x
BP
M4y
BP
M4r
FPGA4
P0
RIO
RIO
RFFE4
6xADC 16-bit
BP
M3x
BP
M3y
BP
M3r
FPGA3
RFFE3
GPAC1
6xADC 16-bit
BP
M2x
BP
M2y
BP
M2r
FPGA2
P0
RIO
RIO
RFFE2
6xADC 16-bit
BP
M1x
BP
M1y
BP
M1r
FPGA1
RFFE1
4xDAC 14-bit
PDCP0
6xADC 16-bit
K2y
K2y
32GFLOPSDSP
FPGA7 FPGA8
Ebe
am
K2y
Pfo
r
K2x
Pfo
r
K1y
Pfo
r
K1x
Pfo
r
to kicker amplifiers
upstream BPMs downstream BPMs undulator BPMs
Feedback/Feed-forward algorithm: Same FPGA board as BPMs, but with 0.5-1GSPS DAC
mezzanine to generate kicker
waveforms
IBFB: Electronics Topology
Boris Keil, PSI DEELS Workshop 2014 13.5.14
12
Control & Status
Registers
Processor Local Bus (PLB)
Kicker Linearization
+
Position & Angle Calculationx-y Plane
Decoupling
Adaptive Feed
ForwardTable
BP
M1x
BP
M1r
BP
M2x
BP
M2r
LatticeTransfer Matrices
x’2 x2x1
Feedback KickerControl
kickersignal
K1x
K2x
kicker signal from y plane
kicker signal from x plane
Timing Control
Adaptive Feed Forward Algorithm
x4
x3
x’4
RIO Linkfrom/to
control system
Data Acquisition
...
ADC, position, angle, control signals, etc.
DDR2 SDRAM
QDR2 SRAM
Position & Angle Calculation
BP
M3x
BP
M3r
BP
M4x
BP
M4r
x6
x5
x’5
Position & Angle Calculation
BP
M3x
BP
M3r
BP
M4x
BP
M4r
K1x Pfor
K2x Pfor
Ebeam
• 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.
IBFB: Algorithm
Boris Keil, PSI DEELS Workshop 2014 13.5.14
13IBFB: 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, …
Frequency (both resonators) 3.3GHz
Loaded Q (both resonators, desired mode) ~70
Q (uncoupled modes) typ. 200-300
Sensitivity 2.5V/(nC*mm)
Thermal noise (lossless cables & electronics, …) 65nm @ 20pC
Angle signal (90° to position signal. Cause: Misalignment) ~16mm * dx/dz
Similar to undulator type, slightly less resolution (~20%). Main differences: ~16x more angle signal (→ align 16x better), cavity spacing (→ crosstalk).
255mm
D. LipkaDESY
Prototype at SwissFEL Injector Test Facility
Boris Keil, PSI DEELS Workshop 2014 13.5.14
14
New: 63dB range, 0.5dB steps
• I/Q downconversion to baseband.• Active temperature stabilization (several sensors + heaters).• Works with or without external trigger & ref. clock.
Differential coax cabling from RFFE
to ADCs
DOOCS & Timing
Interface (SFP/Optical,
PCIe/Ethernet/..., up to 6.5Gbps)
RFFE
MBU Crate: Removable fan tray, redundant main
power supply, ...
IBFB: Cavity BPM Electronics
Boris Keil, PSI DEELS Workshop 2014 13.5.14
15ADC Sample Clock Phase Feedback
Digital ADC sampling clock phase alignment loop• Eliminates phase drift effects• Retains maximal S/N ratio• Monitors possible reference signal malfunctions & beam
arrival time changesPresent algorithm: Uses just
one ADC sample at top to calculate beam position.
Boris Keil, PSI DEELS Workshop 2014 13.5.14
16RFFE: Nominal vs. Measured Gain
Boris Keil, PSI DEELS Workshop 2014 13.5.14
17Gain Dependence of Phase Delay
Boris Keil, PSI DEELS Workshop 2014 13.5.14
18Cavity BPM ElectronicsTemp. Drift
Temperature drift scales with beam
offset. Active temperature
stabilization active: <100nm/°C drift at
1mm offset (0.01%/°C)
Boris Keil, PSI DEELS Workshop 2014 13.5.14
19GUI For Automated Lab Calibration
• 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
20Position Calculation in BPM FPGA
Boris Keil, PSI DEELS Workshop 2014 13.5.14
21SwissFEL BPM Test Area
Correlation of 3 E-XFEL Undulator Cavity BPMs
See IBIC’12, TUPA27, M. Stadler et al.
Only top sample used (so far ...), plus baseline subtraction
Histogram (X1+X3)/2 – X2
Sampled RFFE IQ Signals
Boris Keil, PSI DEELS Workshop 2014 13.5.14
22
Position Noise (RMS, 1 Bunch)
•Undulator cavity (Ø=10mm):~11μm @ 2pC (±5mm range)<0.5μm @ 100-1000pC (±1mm range)
•Transfer line cavity (Ø=40.5mm):~1μm @ 100-1000pC (±1mm range)
Charge Measurement RMS Noise (1 Bunch)
•Undulator cavity (Ø=10mm):<0.06% @ 100-1000pC<60fC @ 100pC<10fC @ 2pC
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)
IBFB: Cavity BPM Performance
Boris Keil, PSI DEELS Workshop 2014 13.5.14
23
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).
IBFB Status
Boris Keil, PSI DEELS Workshop 2014 13.5.14
24Team & 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
Boris Keil, PSI DEELS Workshop 2014 13.5.14
Paul Scherrer Institut
Thank you for yourattention!