New PS one-turn delay feedbacksand further developments

Thanks to Alfred Blas, Heiko Damerau, Valentin Desquiens, Simone Gilardoni, Guido Sterbini, Letizia Ventura, and all involved people from sections BE-RF-FB, IS and CS

Damien Perrelet BE-RF-FB CERN

LIU-DAY 2014, 11 April 2014

Overview of the new feedback board

Current implementations:- PS 10 MHz 1-turn feedback and AVC digital loops- PS transverse damper

Future developments:- PS 1-turn feedback cavities 13/20/40/80 MHz- PS longitudinal coupled-bunch feedback - PSB/AD/LEIR transverse damper upgrade

Summary and outlook

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Content

The new hardware

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RF from BC

Gap Return

DRIVE IN

Power Combiner

1TFB TP

AVC TP

New PS feedback hardware

Power Combiner

CLK DWSTR1

FPGA Stratix II EPS2S90F1020C4

Clock Distri NODLYd UPSTR d nUPSTR d DWSTR1d DWSTR2

4 SERIAL LINKS VME + TRIGGERS

ADC2

ADC1

ADC4

ADC3

LP

LP

LP

LPDAC1

DAC2

DAC3

DAC4LP

LP

LP

LP

ADCs AD6645 DACs AD9754

G Ctrl

LMH6702 AD8009

G Ctrl

G Ctrl

G Ctrl

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Vprog Test

VGAP DET TP

VPROG TP

Spare

CLK DWSTR2

h200

BP1

SRAM

50 MHz

50 MHz

CLK UPSTR

4 ADC RF INPUT CHANNELS → FPGA → 4 DAC RF OUTPUT CHANNELS

Digital

Electronic board

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- Generic VME board- STRATIX II FPGA and external SRAM- 4 RF channels ADC and DAC, low latency, 14 bits and running at 105/125 MSPS- 2 multiplexed fine delay lines for glitch-free delay changes (DAC and FPGA clocking)- 4 serial links CVORB or fast 40 Mbit/s

PS 10 MHz loops

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PS 10 MHz cavity feedback overview

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AVC

1TFB

hn h200

Final amplifier, 2.8-10 MHz cavity, fast wideband FB

Gap returnDrive

H

- Slow voltage control loop (AVC) Gain control at fRF

Reduction of cavity impedanceseen by the beam:

- Fast wide-band feedback around amplifier (internal) Gain limited by delay - 1-turn delay feedback High gain at n frevVprog RF from BC

ADC

ADC

DAC

DAC

PS 1-turn delay feedback

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1-turn delay feedback

hn

NOTCH FILTER

COMB FILTER

AUTO DELAY

DACADCVGAP Detected

1TFB OUT to Drive

FPGA

VME INTERFACE

d UPSTR d DWSTR

RF CLK h200

NOTCH BYPASSVPROG

8/4/2014

Suppress the RF componentto not work against AVC

High gain at frev multiples

Cascade of notch + comb

hn

IIR fractional notch hn/hs Periodic comb at frev

Unique sampling clock h200 integer multiple of the revolution frequency

DPRAM

Fine delayed clock

Measurements with beam before LS1

frequency

FB off

10 db/div

FB on

10 db/div

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Filters only and closed loop transfer functions

Spectrum at cavity gap voltage of a single high intensity bunch 8 10∙ 12 ppb

Beam induced spectrum of four bunches during batch compression

h = 8 13 20

frequency

ampl

itude

h = 8

time

time

Feedbacksuccesfully

follows harmonic changes

PS digital AVC loop

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hn

AVC loop and AVC surveillance

3/21/2014

Gap return

Power amplifiers

-

Error[k]+ 

PIDcontroller

DAC 

ADC

Cavity10MHz

 ADCnon-IQ detection

CORDICI

Q

Detected gap voltage

Modulator

Drive

RF from beam control

Voltage program

H. Damerau, V. Desquiens, M. Haase, D. Perrelet

VetoRF-FB RF-IS

RF veto

Collaboration

® Amplitude loop only, future phase loop or move to IQ loop® Voltage detection using non-IQ algorithm at given harmonic hn

® High power hardware safety ensured by separate surveillance module

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Digital AVC loop measurement

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® Digital PID with adjustable parameters

® Regulation to full voltage without overshoot in about 15 turns

VprogVdet

ErrorRF drive 100 ms/div 10 ms/div

• Step response of the controller around a cable

500 ms test pulse voltage program Response with fast voltage rise

Error

Vdet

RF drive

Vprog

Error

15 turns

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Installation in the machine

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Four new VME crates installed in building 359 (one for each tuning group)

Example for tuning group B (cavities C56, C66, C76 and C81)

® Full commissioning of the new system during start-up 2014

PS transverse damper

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PS transverse feedback

Firmware: A. Blas

1) PU flight time compensation 2) Periodic notch filter for orbit offset suppression3) Hilbert filter for phase compensation at betatron frequencies4) Automatic delay to complete 1 turn

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PS transverse feedback

10 ns/div

PS TFB ON

10 ns/div

PS TFB OFF

→ Present PS TFB designed to damp 44 μm/turn at 1.4 GeV (BW 23 MHz).

A.Blas, S.Gilardoni, G.Sterbini

Damping of injection errorsDamping of head-tail instability

Damper to cure horizontal and vertical transverse instabilities

See talk by Raymond Wasef

New applications

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PS 1-turn feedbacks cavities 13/20/40/80 MHz

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1) Analog conversion to IF and IQ digital processing

→ Using existing and analog frequency conversion boards

or

2) Direct sampling

→ Modification of existing board to achieve higher sampling capabilities

or

→ Build a complete similar new and fast board

Thomas Truszczyński

Frequency conversion board

Mini-PCB to fast ADC adaptation

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PS longitudinal coupled-bunch feedback

Cross-damping: hdet + hkick = hRF = 21 → Detect at h = 13 and Damp at h = 8

H. Damerau, L. Ventura:

See talk by Letizia Ventura

ADC DACBeam(WCM)

Longitudinal kicker (Finemet)

→ Make a new digital coupled-bunch feedback for the Finemet cavity

• Demonstrated with measurements using existing feedback and the spare cavity

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Target to other machines:

- Upgrade of PSB, AD and LEIR transverse dampers

PS 10 MHz possible improvements:

- Cavity phase loop or IQ loop (Reliability of RF manipulations)

- Cavity phase compensation (More gain for 1-turn feedback)

- Multi-harmonic RF generation on-board and use of hs=256

Future developments

- New generic feedback board meets requirements → Complex design but easy to use and allows lots of features

- Two operational loops: PS 10 MHz 1-turn feedback and AVC → Fully digital and remote controlled → Commissioning during setting-up 2014

- New operational PS transverse damper → Good results and required for LIU beams

- Many future developments and projects using this hardware → FPGA gives reliability and flexibility for new ideas

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Summary and outlook

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Thanks for your attention

3/21/2014

Many thanks to people from sections RF/FB-CS and RF/FB/IS for collaboration and support :

Alfred Blas, Philippe Baudrenghien, Andy Butterworth, Heiko Damerau, Valentin Desquiens, Simone Gilardoni, Gregoire Hagmann, Matthias Haase, Wolfgang Hofle, Michael Jaussi, Gerd Kotzian, Tom Levens, Gérard Lobeau, John Molendijk, José Noirjean, Anthony Rey, Maarten Schokker, Guido Sterbini and Letizia Ventura.