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/