LLRF-05 Oct.10,2005 1

Digital LLRF feedback control system for the J-PARC linac

Shin MICHIZONOKEK, High Energy Accelerator Research Organization (JAPAN)

•J-PARC linac•LLRF system•FPGA based Digital FB system•Performance

•During rf pulse•Tuner control•Running•Beam compensation

LLRF-05 Oct.10,2005 2

What’s J-PARC?

frontier science in particle physics nuclear physics, materials science life science and nuclear technology

J-PARC:Japan Proton Accelerator Research Complex

LLRF-05 Oct.10,2005 3

190 MeV normal conducting proton linac Operation frequency: 324 MHz Total 19 klystrons (max.3 MW) RF flat top: 650 us Requirements of cavity electric field stability +-1 ％ (amplitude), +-1deg. (phase)

LLRF requirements

Klystron gallery

Total 19 klystrons drive cavities

LLRF-05 Oct.10,2005 4

Digital LLRF feedback control system for the J-PARC linac

Shin MICHIZONOKEK, High Energy Accelerator Research Organization (JAPAN)

•J-PARC linac•LLRF system•Performance

•During rf pulse•Tuner control•Running•Beam compensation

LLRF-05 Oct.10,2005 5

J-PARC LLRF system

cPCI digital FB system • generates LLRF signal (12 MHz, 48 MHz, 312 MHz and 32

4 MHz)• delivers I/Q modulated rf signals to 2 cavities• recieves rf signals from cavities and down-converts to IFFast hardwire interlock is connected to Pulse Modulator (ou

tside cPCI).Analog fast FB will be used for klystron FB loop.Cavity-tuners are controlled from cPCI by way of PLC.

EPICS

ADC

RF&CLK324MHz

312MHz

312MHz

12MHz

48MHz

1 2M H z

PLL-VCOI/Q M

ADC

DAC

PI-Cont (FPGA)

I Q

I Q

I,Q set

CPU&I/O

Timing Signals

NIM/Timing

VME/ IOC

EPICS CTRL System

Arc

Arc

KLY PfPr

3dB

3stubPhaseShifter

20dB 20dB

40W

KLY FB Loop

Cavity FB Loop

FastInterlock

VSWR Meter KLY Pf, PrTank1,2 Pf, Pr

FA-Link

KLY ArcCirc ArcTank1,2 Arc

Arc Detector

Remote ControllableTrombone

LLRF PLC FA-LinkPC-Link D/I

I/QD

I/QD

I/Q M

Analog FB

KLY

Tank1 Mon.

Tank2 Mon.

PrPf

Pf Pr

M Drive

Tank1

Tan k2Arc

Arc

TunerM

MTuner

PID

TunerPLC

PulseMod

RF SW&

EPICS-LAN

Digital FB /cPCI

12MHzOpticalReference

P,I gain setFB-ON/OFF

LLRF PLC

cPCI FB system

LLRF-05 Oct.10,2005 6

cPCI digital FB system

CPU

I/O

DSP/FPGAMixer&I/Q

RF&CLK

Digital 　　 Analog

2-FPGAs (2x VirtexII 2000) are installed with 4x14bit-ADCs and4x14bit-DACs at 48 MHz sampling

DSP board enables to calculate complex diagnostics such as cavity control.

FPGAs are used only for fast feedback.

cPCI is adopted for the crate.

FPGA based digital FB systemFPGA: Mezzanine card of the commercial DSP board

LLRF-05 Oct.10,2005 7

FB algorism

IF signals are directly read by ADCs.The separated IQ signals are compared with set-tables and PI control is made with FF.

RF ： 324MH ｚLO ： 312MH ｚIF ： 12MH ｚSampling:48MH ｚ

LLRF-05 Oct.10,2005 8

Digital LLRF feedback control system for the J-PARC linac

Shin MICHIZONOKEK, High Energy Accelerator Research Organization (JAPAN)

•J-PARC linac•LLRF system•Performance

•During rf pulse•Tuner control•Running•Beam compensation

LLRF-05 Oct.10,2005 9

Vector Sum Control

Agrees well with simulation

0

1000

2000

3000

4000

5000

6000

7000

8000

0 50 100 150 200 250 300

Time [ms]

Set

val

ue

overdrive

50 100 150 200 2500

1000

2000

3000

4000

5000

6000

7000SDTL 6000

Time [ s]

160 180 200 220 2405900

5950

6000

6050

Time [ s]

measuredcalculatedset

measuredcalculatedset

Amplitude:6,000 and Phase 0 deg. (I=6,000, Q=0)Vector sum control

Set table is exponential function

LLRF-05 Oct.10,2005 10

External monitor

External monitors are assembled with commercial fast FPGA board.The amplitude and phase stability is +-0.15 ％ ,+-0.15deg.

Xtreme DSP board by Xilinx (commercial FPGA board with 66 MHz ADCs)Xtreme DSP board by Xilinx (commercial FPGA board with 66 MHz ADCs)

LLRF-05 Oct.10,2005 11

LLRF-05 Oct.10,2005 12

FB stability

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

4000 5000 6000

Am

p. S

tabi

lity[

+-%]

FB Amp.1FB Amp.2FB Amp.SumDetector Amp.1Detector Amp.2

00.020.040.060.080.1

0.120.140.160.180.2

4000 5000 6000

Pha

se s

tabi

ltiy[

+-de

g. ]

FB Phase 1FB Phase 2FB Phase SumMixer Phase 1Mixer Phase 1

Set value:6,000->5,000->4,000With same FB parameters.FB works well with the amplitude variation of >20%.

LLRF-05 Oct.10,2005 13

Digital LLRF feedback control system for the J-PARC linac

Shin MICHIZONOKEK, High Energy Accelerator Research Organization (JAPAN)

•J-PARC linac•LLRF system•Performance

•During rf pulse•Tuner control•Running•Beam compensation

LLRF-05 Oct.10,2005 14

Tuner control

A klystron drives 2 cavities.ADC_1,2:cavity field monitorsADC_3,4:cavity input monitorsDetuning is calculated from the difference between input and cavity by DSP.-> Tuner control is carried out by DSP.

>1deg. Detuning, tuner >1deg. Detuning, tuner control starts.control starts.

Stop tuning control Stop tuning control when the detuning when the detuning becomes <0.2deg.becomes <0.2deg.

Vector sum is stable Vector sum is stable even with 15 deg. even with 15 deg. detuning.detuning.Needs < 2 min. for Needs < 2 min. for controlcontrol

LLRF-05 Oct.10,2005 15

Digital LLRF feedback control system for the J-PARC linac

Shin MICHIZONOKEK, High Energy Accelerator Research Organization (JAPAN)

•J-PARC linac•LLRF system•Performance

•During rf pulse•Tuner control•Running•Beam compensation

LLRF-05 Oct.10,2005 16

Running data of J-PARC LLRF

Quite stable Quite stable

The trend of the average amplitude and phase (drift) The trend of the average amplitude and phase (drift) The small drifts (<.2%,.2 deg. ) are caused by the tempeThe small drifts (<.2%,.2 deg. ) are caused by the temperature dependence of the rf circuits.rature dependence of the rf circuits.These will disappear at the new version.These will disappear at the new version.

Internal monitorInternal monitor External monitorExternal monitorCavity 1Cavity 1Cavity 2Cavity 2Vector sumVector sum

±0.5±0.5 度度

±0.5±0.5 ％％

LLRF-05 Oct.10,2005 17

Digital LLRF feedback control system for the J-PARC linac

Shin MICHIZONOKEK, High Energy Accelerator Research Organization (JAPAN)

•J-PARC linac•LLRF system•Performance

•During rf pulse•Tuner control•Running•Beam compensation

LLRF-05 Oct.10,2005 18

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

0 200 400 600 800Time [us]

Am

plitu

de

Cavity Amp.Kly Amp.

- 15%

Beam loading test

Beam loading observed at FB monitorBeam loading observed at FB monitor

Beam loadingBeam loading

Beam gate signal modulate the rf Beam gate signal modulate the rf -> beam loading-> beam loading

LLRF-05 Oct.10,2005 19

Beam loading test (cont.)

Only FBOnly FBFB+ beam compensation FFFB+ beam compensation FF

+-5%

beam

+-2deg.

beam+-0.5%

+-0.5deg.

FB monitor Ext. monitor

Amplitude

[%pk-pk]

Phase

[deg.pk-pk]

Amplitude

[%pk-pk]

Phase

[deg.pk-pk]

FB only 8.6 3.5 9.7 3.9

FB+FF_beam 0.4 0.15 0.55 0.29

DAC output

0

1,000

2,000

3,000

4,000

5,000

6,000

0 200 400 600 800Time [us]

Am

plitu

de beam

Beam can be compensated with FF within +-0.3%,+-.15 deg.Beam can be compensated with FF within +-0.3%,+-.15 deg.

LLRF-05 Oct.10,2005 20

• Stability of <+-0.15%, +-0.15deg. is obtained during rf pulse with a SDTL test module.

• Tuner control works well even from 15 deg. detuning position.• Eighteen hours running show good stability.• Beam loading test box enables to test the beam loading effects and the stability

is ~+-0.3%, +-0.15deg. during beam pulse.

• Linac commissioning will start from June 2006.

Summary

LLRF-05 Oct.10,2005 21

Test cavity

Ql=6,800Ql=6,800

Test cavity is quite useful for developing FB algorism.Test cavity is quite useful for developing FB algorism.

0

500

1000

1500

2000

2500

3000

3500

4000

100 110 120 130 140 150

time [us]

IcompQcompQl=6800

Test cavityTest cavity

Step responseStep response

LLRF-05 Oct.10,2005 22

Tuner control (1)

Start: |error-set| > 3 deg.

Goal: |error-set| < 0.2 deg.

324 MHz

Cavity tuner: Response ~100-500 ms

Communication between LLRF PLC and DSP: every 2 sec. (100 ms during tuner control)

Cavity input phase -> measured through FPGA2 Cavity phase -> measured through FPGA1 Phase error : calculated at DSP If the detuning phase is far from set-phase

DSP will change the tuner through PLC until the detuning phase to be proper.

LLRF-05 Oct.10,2005 23

Tuner control (2)

Compare rf phase between cavity-input and cavity. (->detuning) Cavity tuner is controlled when the detuning is larger than set value (>

3 degree for common error and 1degree for relative error)

Absolute error 　 (common error < ±3deg.)

NG OK Good OK NG

-3 -0.2 0 +0.2 　 +3 (deg.) Tuner 1 (Δ1 ）

(stop) move (control start)Tuner 2 (Δ2 ）

(control start) move (stop)

Relative error (Δ1-Δ2 ）　 (relative error < ±1deg.)

Δ1-Δ2 　　　 -1 -0.2 0 +0.2 　 +1 (deg.)

(control start) move (stop)

LLRF-05 Oct.10,2005 24

Calibration

Vector sum

0

1000

2000

3000

4000

5000

6000

7000

100 200 300 400 500 600

Time [us]

Am

plitu

de

Cav1 Amp

Cav2 Amp

Sum Amp

Cav1 Det

Cav2 Det

Amplitude in detector output is calibrated by comparing with FB monitor and detector monitor.

y = 1.0981x - 2277.8R2 = 0.9995

y = 1.1531x - 2355.1R2 = 0.9996

0

1000

2000

3000

4000

5000

6000

3500 4000 4500 5000 5500 6000 6500 7000

Amplitude [ADC]

Wav

e de

tect

or

Cav1Cav2

(Cav1)線形 (Cav2)線形