LLRF-05 Oct.10,2005 1 Digital LLRF feedback control system for the J-PARC linac Shin MICHIZONO KEK, 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
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LLRF-05 Oct.10,20051 Digital LLRF feedback control system for the J-PARC linac Shin MICHIZONO KEK, High Energy Accelerator Research Organization (JAPAN)
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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
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.
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)
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.
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.