boris keil, psideels workshop 201413.5.14 the european xfel intra bunch train feedback boris keil...

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


13.5.14DEELS Workshop 2014


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, ...).


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


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


5IBFB Kicker: S-Parameters


6IBFB Kicker: Diff. Impedance


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


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


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!



10

Droop of kick voltage over bunch train (thermal

effects in MOSFETs, ...):IBFB digital electronics will

compensate droop



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


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


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


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


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.


16RFFE: Nominal vs. Measured Gain


17Gain Dependence of Phase Delay


18Cavity BPM ElectronicsTemp. Drift

Temperature drift scales with beam

offset. Active temperature

stabilization active: <100nm/°C drift at

1mm offset (0.01%/°C)


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", ...).


20Position Calculation in BPM FPGA


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


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


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


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



Thank you for yourattention!

boris keil, psideels workshop 201413.5.14 the european xfel intra bunch train feedback boris keil...

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