Summary of CERN/GSI Meeting on RF Manipulations and LLRF in Hadron Synchrotrons, March 20-21 2014
Summary of CERN/GSI Meeting on RF Manipulations and LLRF in Hadron Synchrotrons, March 20-21 2014
100 m
UNILACSIS 18
SIS 100/300
HESR
SuperFRS
NESR
CR
RESR
FLAIR
Radioactive Ion Production Target
Anti-Proton Production Target
Existing facility: provides ion-beam source and injector for FAIR
Existing facility: provides ion-beam source and injector for FAIR
New future facility: provides ion and anti-matter beams of highest-intensity and up to high energies
New future facility: provides ion and anti-matter beams of highest-intensity and up to high energies
Facility for Antiproton and Ion Research
Ring RF System Frequency Range [MHz]
Voltage per Cavity [kV]
DutyCycle
Length Qty
SIS18 Upgrade
Ferrite cavities, h=4Accel. h=2
Bunch Compression
0.85 ... 5.50.43 ... 2.8
0.8/1.2
1613.340
100%100% 0.05%
3 m1.2 m ≈1 m
231
SIS100 Accel. h=10 (Ferrite)Bunch Compression
Barrier Bucket Long. Feedback
1.1 ... 3.2 0.310 ... 0.560
broadband broadband
2040
2 x 15 (12)
100%0.05%20% 100%
3.0 m1.2 m1.1 m 1.1 m
14922
CR(storage ring
used for stochastic
precooling)
Debuncher (RIB, anti-protons,
incl. Bucket Generation)
1.10...1.25 (1.50)
40 (21) 0.05% 1.125 m
5
CRYRING(ion storage
ring)
Existing Swedish system, „new
controls“
0.01...2.4 ≈0.2 1
Overview on the LLRF System Architecture for FAIR
Harald Klingbeil
Control Aspects, LLRF Requirements
• CW systems (e.g. accelerating systems) vs. pulsed systems (e.g. bunch compressor)
• Cavities with "high" Q factor (e.g. accelerating systems, Q=5...10) vs. broadband cavities (e.g. barrier bucket, Q<1) → different response times
• Fundamental RF frequencies: 300 kHz...5.4 MHz (exception: NESR high harmonics, CRYRING 10 kHz), partly with higher harmonics, fast ramping
• Mutual synchronization of cavities required, also multi-harmonic
(requirement ±3°, note: 1° phase deviation @ 5.4 MHz ↔ about 500 ps)
• Mutual synchronization of synchrotrons (e.g. for bunch-to-bucket transfers)
• Longitudinal beam stabilization (beam phase control, longitudinal feedback), especially for high beam intensities
• Complex RF manipulations (barrier bucket, dual harmonic acceleration, bunch merging, etc.)
Bunch Merging Experiment 30./31.03.2012
-0.03
-0.02
-0.01
0
0.01
0.02
0.03
0.04
0.05
400 450 500 550 600 650 700 750 800 850 900FCT
Sign
al/V
Time
Segment 1000
Segment 2400
Segment 4500
This result that was obtained during the beam experiment. It is obvious that the bunches were merged in two steps as desired.
Waterfall plot of the beam phase monitor signal for measurement
Fully digital control Modular: motherboard + different types of daughtercards Several motherboards collaborate in real-time to implement DLLRF → low-
latency digital links between boards. Sweeping of tagged clock can be transmitted over optical fibres Digital + analogue RF trains available. Also MDDS RF train at high h. Extensive use of DSP (floating point) + FPGA (parallel) processing power.
FPGA: (mostly so far) infrastructure, to be setup but not modified DSP: customisation of the processing to board function & machine Remote FPGA/DSP configuration available
Experience & planning with digital low-level RF systems in small synchrotrons at CERN
Maria Elena Angoletta
Timings (now: firmware event triggered by counter) Reference functions (directly digital). Digital diagnostics (not black box!)
Digital signals from LLRF & digitized signals from other systems can be displayed in the same virtual scope.
Clock: loops sampling (constant, ~10 µs now) or RF (~fREV).
Digital LLRF overview in:
•LEIR•PSB •MedAustron •ELENA •AD
Ion-therapy and research centre in Wiener-Neustadt (Austria)
Proton & Carbon ion therapy, clinical + non-clinical research
Synchrotron currently under commissioning (protons)
Treatment of first patient expected in late 2015.
MedAustron: LLRF layout Current status: cavity servoloop closed & operational. Beam in the synchrotron within days. Being commissioned now.
Longitudinal dynamics in the future FAIR SIS-100: transition crossing
Sandra Aumon
Original Proton Scenario in SIS-100 Do not cross transition
Stable phase shift @ Transition
Longitudinal dynamics @ Transition
Crossing transition means……
Crossing transition energy in SIS-100
Constraint
h in transition crossing chosen
with bucket consideration
Phase and Amplitude Calibration of LLRF Components
Uta Hartel
Amplitude+phase calibration curve
Counter phase measurements to try to minimize the sum voltage of the two cavities
Result with CEL
A hardware family using VME VXS and FMC mezzanines for RF Low-level RF and Diagnostics applications in CERN's synchrotrons
John Molendijk
Digital LLRF Principle
Notes:DDS = Digital Direct SynthesizerDDC = Digital Down Converter
• FMC Modules
High Pin Count FMCs Developed ADC 16 bit 125 MS/s (DDC)• DAC 16 bit 250 MS/s (SDDS)• DDS (can be used as Master Direct Digital Synthesis)
Notes:DDC = Digital Down ConverterSDDS = Slave Digital Direct SynthesizerDSP= Digital Signal Processing
FMC FPGA Main FPGA DSP
FMCs
• FPGA
Main FPGA manages the communication with: VXS, FMC_FPGA, VME64x, DSP.
B-field
Velocity correction
*
Power suppy control
Magnet measurement
B-train
B → frev
Beam control
Beam control
Beam control
Frequency program • Generate the revolution frequency, frev based
on the following parameters:• B = Magnetic field strength of dipole
magnets• Particle type (charge Ze, mass m)
• B-field and revolution frequency information needed for various subsystems
• Especially important as reference for RF beam control
• Transmission protocol to be changed with renovation of B-train system
• PS chosen for first White Rabbit implementation
A New Frequency Program in the CERN Proton Synchrotron
Magnus Sundal
• Ethernet based time synchronous network• Sub-ns accuracy/precision for synchronization• Deterministic low-latency data transfer• Existing hardware implementation• «Backwards compatible» with standard Ethernet
White Rabbit Switch (WRS)18 ports, Gb/s, VLAN, HP MAC-address register,
deterministic low-latency, transparent
Old system:• Instant distribution of
Bdot (rate of change of B-field)
• 10 µT resolution
New flexible frequency program for the PS developed for protons and ions:
• Distribution of B, Bdot, G & S via White Rabbit
• 50 nT resolution• Data rate of 250 kframes/s
Successful validation of B-field distribution via
White Rabbit
Key point of WRS:
The Collector Ring Debuncher
Ulrich Laier
CR DB LLRF requirements
Collector Ring Debuncher System Overview
Digital Generation of Radio Frequency References for the FAIR Acceleration Complex
B.Zipfel
Test installation
BuTiS System=> synchronize the RF signal generated at different location connected with the White Rabbit (CERN Control and Timing Network )
BuTiS green line
BuTiS= Bunch Phase Timing System is the dedicated time synchronization system for the FAIR project -> Fixed frequency transmission (not sweeping clocks).
Existing bunch-to-bucket transfer schemes
Thibault Ferrand
Applications • Booster – PS and LEIR – PS • PS – SPS• SPS – LHC
Future applications • FAIR
Signal synchronisation• Re-synchronisation: one machine should synchronise on the second one or both
machines must synchronise on an external clock. In both case the reference signal must be re-synchronised.
• The different extraction, injection and instrumentation pulses are timed, taking into account the different hardware delays (kickers, pick-ups…)
PS – SPS :
Implementation and control of RF manipulations in the PS
• Recent LHC-type beams require more evolved RF manipulations
• Sequences of:• Bunch splitting and merging• Batch compression and expansion
• Buckets different during process Bucket number control
during both transfers PSB to PS
Bunches from PSB must be placed into the correct buckets Batch compression works only for even number of bunches
Heiko Damerau
1 turn
• Reduce number of control parameters involved simplify operational maintainability
New hardware to generate digital voltage program data for each cavity
• Flexible control matrix in software
Programming complexity reduced to the requirement of each beam
® LHC-type beams: typically 10+2 functions and 4 timings® Single bunch low-intensity beams: 4+2 functions and no
timing
• All cavities of group tuned to same frequency
Consequences of fixed tuning groups® Common harmonic number function per
group® Common relative phase function per group
• Voltage program group-to-cavity mapping
Mapping from groups to cavities
® voltage programs® gap relay timings
• Azimuthal position of 1st bunch ambiguous after RF manipulations: bucket/bunch number one?
• Phase and radial loops closed and act on all RF harmonics simultaneously
Spectral component of beam (WCM) along RF manipulation
hPL = 9/20 20/21
® For hRF = 9 10 20 21 phase loop at hPL = 9 20 21 sufficient
• Bunches must be displaced symmetrically for averaged phase loop
Ekin =
1.4
GeV
Pure h = 9
Pure h = 21 hPL
9/2020/21
frev marker from SPS
Bunch numbering convention PS-SPS
Beam signal from wall current monitor
Convention: 1st bunch at fixed time position with respect to frev ,SPS
® to switch between beams with different RF manipulations
® to debug beam transfer between PS and SPS
Digital local oscillator is programmable to any sequence of the harmonic number hPL
Settings Generation for the RF Systems in FAIR
David Ondreka
Control System Representation of RF Systems &
Settings Generation for FAIR
SIS 100 : generic prototype of RF manipulation
Merging from h=10 to h=5
Status of the Longitudinal Feedback Development for FAIR
Kerstin Groß
SIS 18SIS 100
Simulations for SIS 18
machine experiment with beam this summer
(@ fixed frequency with 2 bunches)
PS 10 MHz cavity feedback overview
AVC
1TFB
hn h200
Final Amplifier, 10 MHz Cavity,
Fast Wideband FB
DAC
ADC
DAC
Gap ReturnDrive
H
- Fast wide-band feedback around amplifier (internal) Gain limited by delay
- 1-turn delay feedback High gain at n frev
- Slow voltage control loop (AVC) Gain control at fRF
Vprog
Damien Perrelet
Why replace the existing feedbacks?
Þ Old 1-turn feedback fully realized in hardware ECL logic little flexibility
Þ Increase resolution of signal processing from 10 to 14 bits
Þ Suppress multiple clocks and avoid double sampling at 4 fRF and 80 frev
Þ Remove phase locked loops curing associated unlocking issues due to sweeping
Þ Problem for harmonics h=7 and 21 (LHC); remove need to start from h=8 (limitation in old system)
Þ Improve delay compensation by dedicated parameters for each RF harmonic
Þ Include a digital AVC in the firmware to replace the old analog hardware
Þ Use a unique and increased sweeping clock for the sampling and the processing, integer multiple of the revolution frequency → hs=200
Þ Digital FPGA-based design: → Improve flexibility, reliability, stability, reproducibility, drifts, …
Þ Low latency components and firmware needed for the 1 turn-feedback
Þ The system must follow the harmonic number provided by the control
Þ Demodulation of multiple harmonics with a single clock → non-IQ
Þ Variable automatic delay compensation during the cycle
Design choices and constraints
Summary
- New 1-turn feedback board is ready and meets expectations
- The two loops implemented 100% digital in the FPGA with more resolution
- Good results without and with beam before LS1 => Commissioning of the new system on the 11 cavities for the restart in 2014 => Final adjustments and eventual modifications during setting-up
- FPGA flexibility allows future new features like : => generation of RF multi-harmonics onboard, RF cavity phase loop, cavity phase compensation, studies to use higher sampling clock hs=256, ..
Electronic board EDA-02175-V2
Coupled-bunch feedback simulations and measurements in the Proton Synchrotron
Letizia Ventura
• In measurements done in 2013 before LS1 coupled-bunch feedback and the spare cavity have been used to excite and damp coupled-bunch oscillation.
• Demonstrated existing already feedback with detection and excitation at different harmonics
h=21 &
18 bunches
h=21 &
21 bunches
• 10 MHz cavities impedance
model implemented and crosschecked either with theory and 2013 measurements
• New feedback also to operate in the frequency domain, similar signal processing as existing feedback, but digital and covering all harmonics simultaneously based on hardware developed for the 1-turn delay feedback
• First test with the beam after the startup in 2014
• Frequency domain longitudinal feedback in the LCBC simulation code implemented and tested
SIS18 simulation at injection (40Argon18+, 11.4 MeV/u), with quadrupolar mode (m=2)
Tuning of longitudinal bunch length feedback for SIS18
Dieter Lens
Bunch length feedback at SIS18
Beam length:• Measure amplitude of beam current basic
harmonic• Feedback correction of gap voltage amplitude• Assumption: cavity dynamics sufficiently fast
Beam phase:• Measure phase difference between beam and gap
voltage• Feedback correction of gap voltage phase• Assumption: cavity synchronization sufficiently fast
Bunch phase and length feedback already successfully tested for stationary beams at SIS18 in 2007
Find feedback models to analyze stability and design different feedback algorithms
Analytic models for bunch length feedback for SIS18 using moments
Find analytic transfer function
Beam experiment of bunch length feedback
Beam length Beam phase
Comparison of models, simulations and experimental results
Summary
• Repeat the meeting every couple of year to exchange know-how and problem-solving and getting ideas from each other.
• Participate to each other experiments to exchange experience and experimental methods.
• Share knowledge on numerical tools and hard- and firmware design flow.
Similar machines & problems & implementation
• Link of 2014 meeting at GSI: https://indico.cern.ch/event/288809/
• Link of previous meeting in 2009 at CERN: http://indico.cern.ch/event/69118/