Commissioning of the FPGA-Based Transverse and Longitudinal Bunch-by-Bunch Feedbac

k System for Taiwan Light Source

Kuo-Tung Hsu

on behalf of the feedback team

NSRRCHsinchu 30076, Taiwan

May 2, 2006

BIW06, FNAL, May 1~4, 2006

I.Introduction

II. Feedback Processor

III. Transverse Feedback System

IV. Longitudinal Feedback System

V. Summary

Outline

BIW06, FNAL, May 1~4, 2006

I. Introduction

TLS is a 1.5 GeV light source.

Dedication in October 1993.

Instabilities are severe in the operation of last decade.

SRF upgrade in Dec. 2004.

Routine top-up operation is started from Oct. 2005.

FPGA-based transverse and longitudinal feedback system are deployed in Dec. 2005 and Feb. 2006.

BIW06, FNAL, May 1~4, 2006

II. FPGA Based Feedback Processor Adopted form the design of SPring-8.

Minor modification in FPGA code.

USB 2.0 interface is supported.

Up to 20 taps FIR filter is supported for transverse feedback.

Up to 50 taps FIR filter is supported for longitudinal feedback.

Up to 10 (20) decimation factor is supported.=> only useful for longitudinal feedback.

BIW06, FNAL, May 1~4, 2006

DD

R F

/FD

DR

F/F

DD

R F

/FD

DR

F/F

DD

R F

/F

12 Bit

12 Bit

12 Bit

12 Bit

12 Bit

Delay FIFO

Delay FIFO

X 4 PLL

499.65 MHz

4:1MUX

Delay FIFO

x2 to 249.83 MHz

4:1MUX

4:1MUX

DelayAdj.

DDR SDRAM, 128 Mega SamplesfRF/4 = 124.91 MHz

DAC500 MS/sec

ADC125 MS/sec FPGA: Xilinx VirtexII Pro XC2VP70-6FF1517C

FIR Filter*FIFO12 Bit

50-tap FIR Filter

20-tap FIR Filter

20-tap FIR Filter

FIR Filter*FIR Filter*FIFO

12 Bit

FIR Filter*FIFO12 Bit

FIR Filter*FIFO12 Bit

Structure of the Feedback Processor

BIW06, FNAL, May 1~4, 2006

Feedback ProcessorBunch

OscillationDetector

Back-endElectronic

andPower

Amplifiers

USB 2.0 Interface=> Register access=> Memory access

Control Network

Linux/PC :

* Feedback Processor Linux Driver support USB 2.0 access* Matlab interface

Control database interfaceFeedback processor register accessCaptured bunch oscillation data accessFeedback filter designData analysis

* Control console

Linux(CentOS Distribution)

TransverseKicker

Transverseand

LongitudinalPickup

LongitudinalKicker

Feedback System Environment

BIW06, FNAL, May 1~4, 2006

III. Transverse Feedback System

1995 Commissioning of the analog feedback system.* Only vertical instability is a problem.* Longitudinal instability is severe.

1996 Second tuner was introduced to RF cavities to shift HOM frequency.

* Longitudinal instability is still severe.* Transverse instability can be controlled by optimized position

of the second tuner.

2004.12 SRF put into operation. * Both horizontal and vertical instability are strong.

* Difficult control by over compensated chromaticity.

2005.04 Analog transverse feedback loop is put back into service again * Both plane instability was suppressed, however, tune

dependence is strong. It is not easy to operate the machine with 0.1% flux

stability.

BIW06, FNAL, May 1~4, 2006

2005.10.12 Start top-up operation @ 200 mA

2005.11.29 Commissioning of the new transverse feedback system.* To solve the sensitivity problem of tune dependence.* To provide better damping for high current operation.* Increase injection efficiency by reduce chromaticity.=> High injection efficiency is essential for top-up operation.

2005.11.30 New digital transverse feedback system commissioning and put into service immediately.

2005.12 Start top-up operation at 300 mA

BIW06, FNAL, May 1~4, 2006

Div

ider

A B

CD

ADC

ADC

20tapFIR

20tapFIR

ADC

ADC

20tapFIR

20tapFIR

DACs

BBFClock Generator

Clock/4 = 124.913 MHz

Clock/4 = 124.913 MHz

Div

ider

# A

# B

# B

FPGAClock124.913 MHz

fRF

499.654 MHz

250 W

AR 250A250

10 KHz ~ 250 MHz

Transverse Kicker

2 nsD

20 dB

20 dB

53 dB

53 dB20 dB

20 dB

156 MHzLPF

Block Diagram of the New Transverse Feedback System

2 Vp-p

LVDS

933 MHz LPF

B

D

Feedback Processor

ch 1

ch 3

ch 2

ch 4

4 ns

4 ns

20 dB

20 dB

46 dB

LNA

X 4

# 1, 5, 9, .. 197

# 3, 7, 11, .. 199

# 2, 6, 10, .. 198

# 4, 8, 12, .. 200

BIW06, FNAL, May 1~4, 2006

EPU5.6

U5SRF

SW6

W20

DCCT

Kicker

SWLS

IASW6A

U9

Stripline

Target Working Point (x, y) = (7.312, 4.168)

Tunability ~ 0.05

C = 120 mTrev = 400.2 nsFrev = 2.49827 MHz

Location x(m) y(m) x y x(m)

R5 BPM1 11.3 5.4 4.876 3.018 0.033 R5 Kicker 4.5 2.7 5.572 3.232 0.397

R5

R4

R3

R2

R1

R6

FeedbackElectronics

80 nsec

150 nsec

R5BPM1(B - D)

Kicker(B - D)

Layout of pickup & kicker

BIW06, FNAL, May 1~4, 2006

Response of the Prototype FIR

Filter

Parameter Value

Energy, E 1.5 GeV

RF frequency, fRF 499.654 MHz

Harmonic number, h 200

Revolution frequency, frev 2.49827 MHz

Momentum compaction factor

0.00067

Operating current, IB 302 mA (March 2006)

Betatron frequency, fx/fy ~ 760 kHz / 450 kHz

Betatron tune, x / y ~ 0.31 / 0.17

Down-sampling factor, D

1

Bunch sampling frequency

frev = 2.49827 MHz

Working frequency of the betatron oscillation detector

fRF

Taps of feedback FIR filter

up to 20

Parameters of the Transverse

Feedback System

Target Tune

Working tune bandwidth (change in arbitrary way)

x: 716 kHz ~ 822 kHz (7.285 ~ 7.328) => > 0.04y: 400 kHz ~ 480 kHz (4.16 ~ 4.192) => > 0.03

Negative chromaticity

Nominal setting (SF, SD) = (151 Amp, 124 Amp)=> (SF, SD) = (121 Amp, 114 Amp) => Beam is still stable=> (SF, SD) = (100 Amp, 100 Amp) => Beam is still stableHowever, beam loss suddenly when turn off the feedback loop

Feedback Loop Tunability

BIW06, FNAL, May 1~4, 2006

Beam spectrum observation – Feedback

OFF and ON Beam spectrum observation

(without longitudinal feedback)Feedback OFF

Feedback ON

BIW06, FNAL, May 1~4, 2006

Loop Closed

Loop Open

Snapshot of Synchrotron Radiation

Beam Profile(w/o Longitudinal

Feedback)

Grow/Damp test results @ 300 mA

0

5

10

50

100

150

2000

10

20

30

40

50

60

Time (ms)

a) Osc. Envelopes in Time Domain

Bunch No.

Arb

. U

nit

0

5

10

0

50

100150

0

2

4

6

8

Time (ms)

b) Evolution of Modes

Mode No.

Arb

. U

nit

0

5

10

50

100

150

2000

5

10

15

Time (ms)

a) Osc. Envelopes in Time Domain

Bunch No.

mm

0

5

10

0

50

100150

0

1

2

3

4

Time (ms)

b) Evolution of Modes

Mode No.

mm

0 50 100 150 2000

0.05

0.1

0.15

0.2

0.25

0.3

0.35

Mode Number

Rela

tive M

agnitude

Horizontal Plane

0 50 100 150 2000

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

Mode Number

Rela

tive M

agnitude

Vertical Plane

Horizontal

Vertical

VerticalHorizontal

ModalSpectrum

BIW06, FNAL, May 1~4, 2006

Stable operation have been achieved in users shift.

Better than 10-3 photon flux stability can be achieved routinely.

Various feedback filters will be tested in a short-term to probe the possibility to improve system performance.

Improve various components form operation point of views are under way.

Current Status of the Transverse Feedback System

BIW06, FNAL, May 1~4, 2006

IV. Longitudinal Feedback System

Longitudinal instability is serve during last decade operation of TLS.

Optimized the second tuner position and RF gap voltage modulation is the tools to deal this instability with the cost of large energy oscillation.

After SRF upgrade

Strength of the longitudinal is weaker than before. Mode pattern are much simple. Longitudinal feedback system are used to lift the residue instabilities.

2006.01 New longitudinal kicker installed.

2006.02.06 Longitudinal feedback system commissioning.BIW06, FNAL, May 1~4, 2006

Summary of Measured Longitudinal Kicker Performance

Modified from the DAΦNE and BESSY kickers (four ridged waveguide damper; nose cone) Center frequency @ 1375 MHz, BW > 250 MHz Highest shunt impedance ~ 1500 Ω A few higher order modes are trapped in the structure and are damped by a hybrid TE/TM coupler Successful operation of the SLS longitudinal kicker Easy adaptation to the TLS storage ring with minor modifications (nearly rectangular 28 x 88 mm beam pipe elliptical, 38 x 80 mm beam pipe) Variation of group delay across the operation bandwidth found (~ 600 ps) Symmetrical excitation to minimize transverse kick due to field non-uniformity

Adaptation of the SLS Longitudinal Kicker to the TLS LFB System

BIW06, FNAL, May 1~4, 2006

Parameter Value

Energy, E 1.5 GeVRF frequency, fRF 499.654 MHz

Harmonic number, h 200

Revolution frequency, frev 2.49827 MHz

Momentum compaction factor

0.00067

Operating current, IB 300 mA (March 2006)

Synchrotron frequency, fs 33.7 kHz

Synchrotron tune, s 0.0136

Down-sampling factor, D 4

Bunch sampling frequency

frev/4 = 625 kHz

Working frequency of the phase detector

3 fRF (or 6 fRF)

Phase detector range ± 30o (± 15o)

Taps of feedback FIR filter

up to 50

Parameters of the Longitudinal Feedback System

Response of the Prototype FIR Filter

BIW06, FNAL, May 1~4, 2006

EPU5.6

U5SRF

SW6

W20

DCCT

Kicker

SWLS

IASW6A

U9

Stripline

s ~ 0.0136

C = 120 mTrev = 400.2 ns

frev = 2.49827 MHzfs = frev/4 = 625 kHz

R5

R4

R3

R2

R1

R6

R5BPM4(A+B+C+D)

Longitudinal Kicker

Layout of pickup & kicker

Beam Position Monitor

(Energy Oscillation Detector)

Longitudinal Kicker(Energy Correct Kick)

Power Amplifier

Feedback Electronics

BIW06, FNAL, May 1~4, 2006

Block Diagram of the Longitudinal Bunch-by-Bunch Feedback System

A B

CD

ADC

ADC

50tapFIR

50tapFIR

ADC

ADC

50tapFIR

50tapFIR

DAC

FPGAClock124.913 MHz

499.654 MHz

200 W

53 dB30 dB

LVDS

I-Tech’sRF Front-End

499.654 MHz

SSBOr

QPSKModulator

Milmega AS0814-250R0.8 GHz ~ 1.4 GHz

20 dB

1500 MHz (SSB) or 1375 MHz (QPSK)

Buffer and Delay Module

8 ns

4 ns

2 ns

6 ns

Longitudinal Kicker

X 4

X 3

BBFClock Generator

Clock/4 = 124.913 MHz

Clock/4 = 124.913 MHz

# 1, 5, 9, .. 197

# 3, 7, 11, .. 199

# 2, 6, 10, .. 198

# 4, 8, 12, .. 200

BIW06, FNAL, May 1~4, 2006

SSB Modulator

RF Output

Monitor

I

Q

0o

90o

ExcitationOn/Off Control

Correction Signal

499.654 MHzFrequencyMultiplier

0o

90o

0o

Phase Shifter

QPSK Modulator

AD8131Differential Amplifier

MiniCircuits Amplifier

Sirenza STQ-2016 700-2500 MHz Direct Quadrature Modulator

USB or LSB Selection

PULSAR QE-14-44290o Hybrids (2~250 MHz)

Shut-down control

Beam Spectrum

BIW06, FNAL, May 1~4, 2006

Loop Open 40 msec

Temporal Behavior of Longitudinal Instability Build-up

Loop Open 100 msecLongitudin

al Instability

Signal

BIW06, FNAL, May 1~4, 2006

Beam Phase and Beam Spectrumwith Feedback Loop Open and

ClosedBeam Spectrum

(Open-Loop vs. Closed-Loop)

62.5 MHz peak is due to filling pattern with 16 nsec periodicity

2nd harmonicof 62.5 MHz

Filling Pattern

Beam Phasew/o LFB

Beam Phasew LFB

Beam SpectrumDetailsw/o and w LFB

BIW06, FNAL, May 1~4, 2006

Longitudinal Grow/Damp Experiments

0

5

10

50

100

150

2000

5

10

Time (ms)

a) Osc. Envelopes in Time Domain

Bunch No.

deg@

RF

0

5

10

0

50

100

150

0

1

2

3

4

5

6

Time (ms)

b) Evolution of Modes

Mode No.

deg@

RF

0 50 100 150 2000

0.5

1

1.5

2

2.5

3

3.5

4

4.5

Mode No.

Deg @

RF

0 2 4 6 8 10 120

1

2

3

4

5

6

7

8

Time (msec

Deg @

RF

Mode 61

Mode 106

@ 250 mA

BIW06, FNAL, May 1~4, 2006

Streak Camera Observation

Loop Open

Loop Closed

One Turn

One Turn

Loop Closed -> Open -> ClosedOne Turn

Loop Open

Loop Open

Snapshot of the Synchrotron

Radiation Beam Profile

Loop Closed

Loop Open

BIW06, FNAL, May 1~4, 2006

Current Status of the Longitudinal Feedback System

Stable operation have been achieved in users shift.

Increase the beam brilliance at the results.

Various feedback filters will be try to improve system performance.

Improve aspect form operation point of views are same as transverse feedback system.

BIW06, FNAL, May 1~4, 2006

V. Summary

Two major upgraded have been completed recently for the TLS.- SRF cavity- Top-up operation

Transverse feedback system upgrade from analog to digital system in late 2005. Longitudinal feedback system commissioning successful in early 2006. Both the transverse and longitudinal feedback loop adopt the same feedback processor - SPring-8SPring-8 designed feedback processor. Modified SLSSLS longitudinal kicker is used. SLACSLAC analysis code is adopted for transient signal analysis. Both systems put into service immediately after commissioning. Improved the system performance and functionality is on going.

BIW06, FNAL, May 1~4, 2006

Acknowledgements

Many peoples contributed to this project directly or indirectly. Thanks for their help.

T. Nakamura, K. Kobayashi (JASRI/SPring-8)M. Dehler (SLS/PSI)M. Tobiyama (KEKB)J. Fox, D. Teytelman, S. Prabhakar (SLAC)J. Seebek (SSRL),G. Strover, J. Byrd (LBNL)

Thank You for Your Attention !

BIW06, FNAL, May 1~4, 2006