Improvements of the LLRF system at FLASH

Mariusz Grecki, Waldemar Koprekand LLRF team

Agenda

• GUN linearization• Adaptive feed-forward at ACC1• Beam load compensation at ACC1• Klystron nonlinearity compensation• Detuning measurement and Piezo control

Gun linearization

Where is the problem?

RF-Gun setup

High power chain linearizationPfor Q Pref I Pref QPfor I

Set-PointTable

Feed-ForwardTable

+

FeedbackGAIN

FPGA CONTROLLER

CalibrationOffset

DAC1 ADC5

RotationMatrix

RotationMatrix

I Q

I

Q

I

Q

I Q

I Q

I Q

I Q

DAC2

VECTOR MODULATOR

Timming & ControlModule

DigitalInput 1

DigitalInput 2

TIRGGER 1MHz

Offset

x

CalibrationOffset

ADC6

CalibrationOffset

ADC7

CalibrationOffset

ADC8

I Q

+

I Q

Filtery=N*xn+(1-N)*yn-1

I

Q

IntegratorGAIN

x

+

I

QI

Q

∫

-+

Linearization

VME

DOOCS SERVERFF table calculationAmplitude SP

Phase SP

Corr.tables

Measurement devices of GUN forward power

waveguide

Klystron

to RF-Gun

diode

A/φ detector

I/Q detector

PforPref

High power chain linearization based on amplitude detector measurement

phase [deg]

norm

aliz

ed k

lyst

ron

pow

er v

aria

tion

Temperature behaviour during linearization

High power chain linearization based on diode measurement

phase [deg]

norm

aliz

ed k

lyst

ron

pow

er v

aria

tion

Temperature behaviour during linearization

Temperature behaviour during linearization

Phase of diode vs forward power measured in SIMCON

norm

aliz

ed k

lyst

ron

pow

er v

aria

tion

phase [deg]

Phase scan of forward power

Rotation matrix

cos(α) -sin(α)sin(α) cos(α)=

I2

Q2

I1

Q1x

x

y

V1

V2

α

A11*cos(α) -A12*sin(α)A21*sin(α) A22*cos(α)=

I2

Q2

Iin

Qinx x

y

I1I2

Q1

Q2

Ir1 Ir2

Qr1

Qr2

Non-orthogonal I & Q

I

Qφ

Iout = Iin + Qin* sin(φ)Qout = Qin* cos(φ)

New DOOCS control panelsA11*cos(α) -A12*sin(α)A21*sin(α) A22*cos(α)=

Irot

Qrot

Iin

Qinx

Iout = Iin + Qin* sin(φ)Qout = Qin* cos(φ)

Input calibration panel Advanced input calibration panel

Phase scan of forward power

Before and after input linearization

Adaptive FF at ACC1

CAVITY 1-8

Set-PointTable

Feed-ForwardTable

Exceptiondetection

-

DAC

SIMCON 3.1 BOARD – FIRMWARE

ADC1-8

I/Q detector

RotationMatrix

VECTORSUM

Klystron correction tables

VECTOR MODULATOR

Timming & ControlModule

DigitalInput 1

DigitalInput 2

TIRGGER 1MHz

ExceptionHandling

BIS AND/OR RF GATE

Offset

DigitalOutput 1

Error signal

IRQ to VME

AFFtable+

MIMO+

Beam loadingcompensation

ADC9

+

TOROID

DAQ VME40 signals from SIMCON

Loop delay regulator

PowerPC

Averaging

Errortable

IRQ

Xilinx Virtex II Pro

AFF vs FB

FB, Gain=25, AFF OFF FB, Gain=5, AFF ON

AFF used for beam load compensation

AFF OFF AFF ON

AFF status

• implemented in FPGA and PowerPC• two versions of AFF tested• stable operation over minutes• control through virtual RS-232 port• DOOCS control panel not ready

Beam load compensation at ACC1

CAVITY 1-8

Set-PointTable

Feed-ForwardTable

Exceptiondetection

-

DAC

SIMCON 3.1 BOARD – FIRMWARE

ADC1-8

I/Q detector

RotationMatrix

VECTORSUM

Klystron correction tables

VECTOR MODULATOR

Timming & ControlModule

DigitalInput 1

DigitalInput 2

TIRGGER 1MHz

ExceptionHandling

BIS AND/OR RF GATE

Offset

DigitalOutput 1

Error signal

IRQ to VME

AFFtable+

MIMO+

Beam loadingcompensation

ADC9

+

TOROID

DAQ VME40 signals from SIMCON

Loop delay regulator

PowerPC

Averaging

Errortable

IRQ

Xilinx Virtex II Pro

20 ns

Sampling of toroid signal

70 nst

30 bunches measured by SIMCON

before – clock=50MHz – local clock after – clock=54MHz – clock from MO

Beam load compensation

Klystron nonlinearity compensation

(more general:High Power Amplifiers

nonlinearity compensation)

Current high power amplifiers diagnostic hardware status

GUN

Vector Modulator

LLRF amplif ier

20dBmax out 0dBm

Preampli fier

max out

400W

Klystr onDirec tional c oupler

LO

ADC

atten uator

LO

attenuat or

Direc tionalcoupler

LLRF CONTROLERDSP/FPGA

ADC

ADC DOOCS Servers

Power s pl itter

(3 dB)

attenuator

ADC

LO

attenuato r

ADC

LO

Circ ulator(~2dB)

Available DOOCS signals:TTF2.RF/ADC/KLY3_VM/CHANNEL.TDTTF2.RF/ADC/KLY3_PAMPL1/CHANNEL.TDTTF2.RF/ADC/KLY3_PAMPL2/CHANNEL.TDTTF2.RF/ADC/KLY3_OUT/CHANNEL.TD

Directional coupler

Current high power amplifiers diagnostic hardware status

Acc1

Vector Modulator

LLRF amplif ier

20dBmax out 0dBm

Preampli fier

max out

400W

Klystr onDirec tional

c oupler

LO

ADC

att

LO

att

Direc tionalcoupler

LLRF CONTROLERDSP/FPGA

ADC

ADC DOOCS Servers

Power s pl itter

(3 dB)

att

ADC

LO

Power spl itter

(3 dB)

att

ADC

LO

Circulator(~2dB )

Available DOOCS signals:TTF2.RF/ADC/KLY2_VM/CHANNEL.TDTTF2.RF/ADC/KLY2_PAMPL1/CHANNEL.TDTTF2.RF/ADC/KLY2_PAMPL2/CHANNEL.TDTTF2.RF/ADC/KLY2_OUT/CHANNEL.TD

Current high power amplifiers diagnostic hardware status

Acc2_3Available DOOCS signals (temporary location):TTF2.RF/ADC/ACC3.TOTAL/CH02.TD – DAC output ITTF2.RF/ADC/ACC3.TOTAL/CH03.TD – DAC output QTTF2.RF/ADC/ACC3.TOTAL/CH04.TD – after RF gateTTF2.RF/ADC/ACC3.TOTAL/CH05.TD – after 1 st preampTTF2.RF/ADC/ACC3.TOTAL/CH06.TD – after 2 nd preampTTF2.RF/ADC/ACC3.TOTAL/CH07.TD – after klystron

Vector Modulator

Power splitt er (3 dB)

LO

LLRF ampli fier

20dBmax out 0dBm

Preampli fiermax out

400W

Klys tronDirec tional

coupler

attenu ator

LO

ADC

at ten uator

LO

attenuator

Directional coupler

LLRF CONTROLERDSP/FPGA

ADC

ADC

ADC DOOCS Servers

Power spl itter (3 dB)

attenuator

ADC

LO

Current high power amplifiers diagnostic hardware status

Acc4_5_6 Available DOOCS signals (temporary location):TTF2.RF/ADC/ACC5.TOTAL/CH02.TD – DAC output ITTF2.RF/ADC/ACC5.TOTAL/CH03.TD – DAC output QTTF2.RF/ADC/ACC5.TOTAL/CH04.TD – after RF gateTTF2.RF/ADC/ACC5.TOTAL/CH05.TD – after 1st preampTTF2.RF/ADC/ACC5.TOTAL/CH06.TD – after 2nd preampTTF2.RF/ADC/ACC5.TOTAL/CH07.TD – after klystron

Vec tor Modulator

Power splitt er (3 dB)

LO

LLRF ampli fier

20dBmax out 0dBm

Preampli fiermax out

400W

KlystronDirectional

c oupler

attenuator

LO

ADC

attenuato r

LO

attenuator

Directional coupler

LLRF CONTROLERDSP/FPGA

ADC

ADC

ADC DOOCS Servers

Power splitter (3 dB)

attenuator

ADC

LO

TO BE INSTALLED

HPA AM/AM and AM/PM characteristics measurements.

• The set of amplitude-amplitude and amplitude-phase characteristics measurements have been done for the klystron 5 and klystron 2 during last two years.

• The constellation diagram method have been used for the characterization results visualization.

• Basing on achieved characteristics the correction coefficients have been calculated.

High power chain non-linearities characterization

Non-linearities and saturation phenomena:

• increasing the driving power ⇒non-linear amplifier behaviour

• constant increasing of driving power ⇒ saturation

• different saturation level for a different operation conditions

Complex representation of the HP chain devicesExample for kly. 5 (each axis unit is an ADC voltage)

Signal parameters:Pulse length – 1200 us,Number of steps – 50,Signal range – 0 up to max. available level

I

Qtime

I max

tp

Results example – klystron 5

Constellation diagram:Measurement for one phase (Q=0). Klystron output characteristics for different HV levels.

Constellation diagram:Grid measurement with 20 steps resolution

KLYSTRON 5

1st preamp 2nd preamp Klystron output

DAC output VM output

Results example – klystron 2

Constellation diagram:Grid measurement with 50 steps resolution

Constellation diagram measurement:Measurement for one phase (Q=0).Klystron output characteristics for different HV levels.

HPA's Linearisation algorithm principles.

linear char.

corr amp.

req amp

controler output signal

max amp.

real char.

Input amp.

Output amp.

max

Output phase[deg]

Input amp.max

controler out. signalcorr. amp

Phasecorrection

From the nonlinearity measurement the AM/AM (amplitude to amplitude) and PM/AM (phase to amplitude) of the high power chain can be achieved. NOTE!! The nonlinearity is only function of input amplitude.

Driving signal representation:Z = Id + Qd = |Z| * [cos(phi) + i * sin(phi)]

Correction signal:C = Ic +Qc = |C| * [cos(th) + i * sin(th)]

From the linearisation both amplitude and phase correction are achieved. Can be realised using the complex multiplication.

C*Z = Idc + i*Qdc C*Z = ||Z|*|C||*[cos(phi+th)+i*sin(phi+th)]

Linearization tool implementation in LLRF field controller (Simcon).

• The linearization tool realization is based on the set of look-up tables • The amplitude of the controller driving signal (calculated in the FPGA) is used for

addressing the look-up tables with correction coefficients for I and Q. There are 32 word 18bits tables with corrections calculated in the MATLAB from the characteristics achieved during the characterization. In order to minimize the tables size (save the FPGA resources) the tables with linear interpolation between the knots.

• The contents of the tables is updated – according to the changes of the HV level (for instance adjusted by an operator).

Amplitudecalculation

Rotationmatrix

I lin.

I corr. I corr. Rangetable

I curve slope range table

Amp. Range32 posit.tables

Proportional feedback controller

Q corr. Q corr. Rangetable

Q curve slope range table

Amp. Range32 posit.tables

I dQ d

Ic

Qc

Q lin.

Tool tests results in ACC2&3 and MTS.

• The set of in-situ tests were performed in the MTS and the FLASH in order to evaluate performance of different configuration of linearization tool.

• During the characterization phase the nonlinearities of the amplitude and phase characteristics have been determined for the different HV level of the klystron modulator.

• Achieved data was processed and used for the correction coefficients calculation. Depending on tested variant of configuration the tables with 4, 8,16 or 32 positions were up-loaded to the FPGA.

• Although the most often used configuration was 32 positions tables with linear interpolation, others were also possible but required the LLRF controller reconfiguration (recompilation).

Examples of tool tests results in MTS.

Study of the RMS error of vector sum error signal in function of LLRF feedback loop gain. Black traces – with linearisation blue and red trace – without linearization

Amplitude and phase characteristics of MTS HPC nonlinearities (blue trace) and linearized characteristics (red trace). Characteristics for modulator HV level 9,4kV

Klystron 5 HPC linearisation results• Linearisation test had been performed using Simcon(FPGA)

controler,• Correction tables were „on” • HV level – 10800 (value on PLC) about 110kV• Two iteration of the linearization were performed.

Current work – linearization tool implementation in ACC1 LLRF

feedback controller.• Linearization tool will be installed in the ACC1 LLRF

control loop controller. • Appropriate modification of the controller structure,

dedicated controller DOOCS server, and Matlab scripts have been done.

• The offline tests of the tool performance is planned for July and August 2007.

• In-situ tests before regular operation will be performed during August-September 2007 accelerator study period in FLASH.

Conclusions.

• Diagnostic setup installation ready for the high power chain amplifiers examination has been prepared for most of the FLASH modules.

• Linearization method that can be implemented in standard LLRF feedback loop controller have been developed and tested.

• Successful tests of the linearization tool have been performed in the MTS and the HPC of ACC2&3.

• Tool implementation in ACC1 field controller is in progress.

Detuning measurementand Piezo control

Detuning compensationcontrol system

FPGA

DAC

ADC

ADC

PIEZO DRIVER

PIEZO SENSOR

RF PROBES

ACTUATOR

PIEZO STACK

SENSOR

downconverter

Simcon3.1L

Detuning block

Detuning computation block

atan atan

Forwardcalibration

Probesignal

divisionsubstraction

Ampprobe Phsforwa

sincos

Phsforwa-Phsprobe Ampforwa/Ampprobe

detuning

6 clk

4 clk

4 clk

FIR

Phsprobe

substraction

1 clk

1 clk

3 clk

19 clk

Ampforwa

Data acquisition block

MT1 MT2

2 ms 98 msII readingDAQ recording

10 Hz of RF pulse repetition rate

Arbitrary access of II to DAQ internal memory

Measurements in ACC7/CAV6

0 500 1000 1500 2000 25000

5000

10000

15000

0 500 1000 1500 2000 2500-1.5

-1

-0.5

0

0.5

1x 105

0 500 1000 1500 2000 25000

000

000

000

000

000

000

000

000

000

000

0 500 1000 1500 2000 2500-14

-12

-10

-8

-6

-4

-2

0

2

4

6x 104

400 600 800 1000 1200 1400 1600 1800 2000

-1

0

1

2

3

4

x 104

amplitude and phaseForward power

amplitude and phaseProbe signal

Detuning

0.08 0.1 0.12 0.14 0.16 0.18 0.2 0.22-4000

-3000

-2000

-1000

0

1000

2000

3000

0.097 0.098 0.099 0.1 0.101 0.102 0.103 0.104 0.105

-1200

-1000

-800

-600

-400

-200

0

200

Probes debug Pulse debug

200 400 600 800 1000 1200 1400 1600 1800 2000

0

100

200

300

400

500

600

700

X: 544Y: 226.2

time[us]

detu

ning

[Hz]

ACC7/CAV6 - online detuning measure

X: 1205Y: 52.8

Detuning measurement

filling

flat

decay

FT detuningequals to 180 Hz

Amplitude and Phasemeasurement

0 500 1000 1500 2000 25000

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

time[us]

grad

ient

[MV

/m]

ACC7/CAV6 - Amplitude of probe signal

0 500 1000 1500 2000 2500-180

-160

-140

-120

-100

-80

-60

-40

-20

time[us]

degr

ees

ACC7/CAV6 - Phase of probe signal

Probe signalafter coodrinate conversion

Microphonics

100 200 300 400 500 600 700 800 900 1000

0.5

1

1.5

2

2.5

3

3.5

4

4.5

x 104

X: 131.3Y : 4.372e+004

X: 431.3Y : 1.486e+004

X: 731.3Y : 6241

freq [Hz]

ampl

itude

[a.

u.]

abs(fft)

mechanical cavity resonancearound 130 Hz

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35-295

-290

-285

-280

-275

-270

-265

time[s]

ampl

itude

[a.u

]

Piezo driver results (1)

0

20

40

60

80

100

120

0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 1,1 1,2

Umi [V]

Umo [V]

0,00

50,00

100,00

150,00

200,00

250,00

300,00

350,00

400,00

Imo [mA]Gu dla Cpiezo = 2,47uF Gu dla Cpiezo = 3,37uFGu dla Cpiezo = 5uF Imo dla Cpiezo = 2,47uFImo dla Cpiezo = 3,37uF Imo dla Cpiezo = 5uF

Half a sine

Piezo driver results (2)

y = 0,3067x2 + 0,909x + 26R2 = 0,9012

0

20

40

60

80

100

120

140

0 2 4 6 8 10 12 14 16 18

N

θ[°C]θ(N)2nd order polynomial aproximation θ(N)

rising number of pulsespiezo 5 uF

Imo = 510 mA

Piezo driver results (3)

A

B

C

A

B

C