The 18th KEKB Accelerator Review Committee (2013)

Improvement of LLRF System~ KEKB LLRF Team ~T. Kobayashi, K. Akai, K. Ebihara,
A. Kabe, K. Nakanishi, M. Nishiwaki, J. Odagiri~ Mitsubishi Electric TOKKI System Corp. ~H. Deguchi, K. Harumatsu, K. Hayashi, J. Nishio,
J. Mizuno, M. Ryoshi,

The 18th KEKB Accelerator Review Committee (2013)

1 /17

Talk Outline
1. Overview the new LLRF System
2. Prototype Performance & Improvements- High power operation test results- Found problem and the solution projection- Improvement of thermal stability- The other improvement

3. Schedule & Summary
Recommendation ( the 17th KEKB Review Committee )1. Confirm the system performance with "out of the loop" measurements.
2. Demonstrate acceptable thermal stability with the revised version.
The 18th KEKB Accelerator Review Committee (2013)

2 /17

New LLRF System for SuperKEKB
Preset analog systems will be replaced by new digital ones step-by-step.

A prototype of1. new
LLRF system (α-version)
&LLRF%#!
hasuTCACPU(+HDD)%#!
been developed and the performance was
evaluated
last'Linux Server(tftp,year.
nfs, DHCP, ntp)
'FPGAConfigurationboot loader (3$(")

New LLRF System for one klystron(EIA-19” rack)
PLC
Linux-OS PC’s with EPICS

PM (Power Module)$(")
I/L Control  
  $("*& VSWR$("+
MonitorCavityFBControl
Tuner
Control 
  µTCA crate

uTCA-platform
FPGA Boards(AMC Card)

16-bit ADC x 4ch,
16-bit DAC x 2ch

Operate via CA
Down Converter

Arc Sensor

Discriminator

3
Each board has a CPU (PPC), and the EPICS-IOC      
on Linux-OS is embedded.

2010/11/25

KEKB_UG_LLRF-069B

EPICS control on FPGA core and PLC••This system consists of µTCA-based FPGA boards & PLC.
EPICS-IOC on Linux-OS is embedded in each of them. They
can be operated remotely via EPICS-Channel Access.

•Hardware is common for both of ARES & SC Cavity. (Alsoboth softwares are much the same.)Feb. 16, 2010

RF Overview (K. Akai)

The 18th KEKB Accelerator Review Committee (2013) •

Klystrons (LLRF) : Cavity unit = 1 : 1 (SuperKEKB)
3 /17

Block Diagram of FB&Tuner Cont. (ARES)

The 18th KEKB Accelerator Review Committee (2013)

4 /17

High Power Test of α-ver.
with ARES Cavity @D8D ( Nov. 2012 ）Op. - GUI (CSS-Boy)

Fuji D8 section

The 18th KEKB Accelerator Review Committee (2013)

5 /17

Strip-chart of Cavity Start-up Sequence
FB ref. param. wastrimmed manually.

Read Error？

KLY output power (100kW)
Raised-up slowly by
sequence program withcavity FB control.

KLY Phase
A-cav FB-loop
Cavity Phase
KLY FB-loop(Cav. FB-Off)
Cavity Level

3 deg.

S-Tuner Pos.
A-Tuner Pos.

10min

FB-OFF
Manually

Cavity start-up sequencer ran as expected.
FB control and auto tuning control also worked successfully.
The 18th KEKB Accelerator Review Committee (2013)/17

Stability Evaluation
by “out of the loop” Measurement

High Power Test

Divider

DBM
Oscilloscope
DPO4104B±2V ← ±9026dB Amp.

20dB Amp.

Cavity Pickup
Monitor

DC~100kHz
RF Detector
For the amplitude measurement, base-line voltage was off-set in the oscilloscope.
The 18th KEKB Accelerator Review Committee (2013)7 /17

High Power Test

Measurement Result of Stability
ARES 100kW driving with FB control.

Phase

Amplitude
0.2%

0.2 deg.

0.2%

0.2 deg.

rms: 0.02%

rms: 0.02 deg.

No difference between FB-gains was found in this measurement method.
The 18th KEKB Accelerator Review Committee (2013)8 /17

High Power Test

Klystron Phase Change
due to Anode Voltage Control

For efficiency optimization, the anode voltage is controlleddepending on klystron input power to reduce the collector loss.

Klystron Input-Output Characteristics

KLY Anode Voltage

80 deg.
Input PowerThe kly. output phaseshifts greatly in response
to input/output power.

This loop phase shift of 80 deg. might be criticalproblem for the cavity FB control, because for I/QFB technique, controllable loop phase change isonly +/- 90-deg. in principle.
In practical operation, acceptable phase change isabout +/- 60 deg. (depending on FB gain.)
The 18th KEKB Accelerator Review Committee (2013)This phase change is
unexpectedly-large.
Klystron Phase Lock Loop
(KLY-PLL) is necessary.
9 /17

Implementation of Klystron PLL(future plan)

FPGA - FB cont.

LO
IF

ADC
&IIR

a -b
b a

Cavity Pickup
LO
Klystron Output
IF

ADC
&IIR

I
a -b
b a
Q

Klystron Output

Cavity Pickup

SelectorQ

FF- I

Ref - I

-

I

-

RF
Rotationfor KLY-PLL+

PICont.

+Calib.

FF - QRef - QK
PLL-ON,LEVEL-OK?

ak -bk
bk ak

a -b
b a

DAC
DAC
IQ-Mod.

ac -bcbc ac

C  Δ ≡ K ⇐C

DriverAmp

ak=cosθ,bk=sinθKlyθ = ∑ −Sign (QΔ ) × ΔθΔθ：increment constantCavityCos and sin values are given by reference table in 2-deg. step and can beinterpolated by 1st-order approximation.
Required loop band : ~1kHz ( The anode voltage response : about 10Hz.)
The 18th KEKB Accelerator Review Committee (2013)10 /17

Time Domain

Simulation Result of the KLY-PLL

Cavity FB control with KLY-PLLKLY loop Delay=1us
Δθ=0.01 deg. @CLK40MHz

Pgain=2.5, Igain=2.0e5
Cavity Loop Delay=2us, Δω=0

In this simulation, the considerably faster response than the supposition is assumed.

w/o KLY-PLL

with KLY-PLL
Amplitude

Amplitude

Kly Out Amp.

Kly Out Amp.

A-Cavity Amplitude

A-Cavity Amplitude

Phase

KLY-PLLON

Phase
PLL-Cont. Phase(Kly Phase Change) 100 deg.

Kly Out Phase60 deg.
A-Cavity Phase

1ms A-Cavity Phase11
The 18th KEKB Accelerator Review Committee (2013)/17

Upgrade to β-Version
The second trial model (β-version) has been produced, and now under evaluation.
The high power test is planned in march 2013.
The fist prototype

α version

Discriminatorfor some RF signals I/L, which is independent of digital control.

Analogue comparators are used to detect abnormal.

DET
RF signal

to PLC AD module

+
-

x 8ch

RFSW-OFF

5 FPGA cards in uTCA

Threshold from PLC-DAC

β version
DET
RF signal
x 8ch
Optical Fiber

ARC
light
x 8ch

Detector outputs are A/Dconverted on FPGA at 10MHz.

FPGA
ADC

comp.

x 8ch 14bit ADC

PD

FPGA
ADC

β-version LLRF System

RFSW-OFF
Waveforms at I/L event canbe obtained via EPICS likean oscilloscope.
Ext. Trig. is also available.

comp.

RFSW-OFFx 8ch 14bit ADC

The 18th KEKB Accelerator Review Committee (2013)12 /17

Thermal Stability ( reported in the previous review. )Acceptable
0.1%/deg.C in Amplitude
Temp. Coefficient 0.1 deg./deg.C in Phase

Ref.

Measured
Result

LLRF System

LO & CLK Distributor

RF:508.9MHz

LO
Down
Converter

CLK

FPGA

519.5 MHz
I
Q

ADC

BPF

ch1

IF
ADC
IF
10.6MHz

RF:508.9MHz

Amplitude: 0.5 % / deg.C
Phase: 0.25 deg. / deg.C

I
Q

IQ-Mod.

Δ

PI
Cont.

DAC
DAC

ch2~4
ADC
ADC

RF:508.9MHz

10 BPF’s
CavityFrom the evaluation of each RF element device, it is found that the main factor is
BPF property in the downconverter for the temperature dependency.
The 18th KEKB Accelerator Review Committee (2013)/17

BPF Choice & Fine Tuning of temp. coefficient
Lumped Constant Circuit Type

α-ver.
β-ver.

!"#!$0$!12!03 /!"#!$0$!12!03

56789:;<
789:;<
2IJ<
!"#$
%&'(
$
%&'(
*+
).34+
).34+).2+

Cavity Type (K&L - 4FV50)

for good regularity in characteristics
betweenmanufacture lots.
!"#$%&<()*+,!"#$%&<()*+,!"#$%&<()*+,!"#$%&<()*+,:;<=%&'(%)*+,-./!"#$%&'(%)*+,-./:;<=%&'(%)*+,-./!"#$%&'(%)*+,-./

Amplitude

0.011 % / deg.C

0.017 % / deg.C!"#$%&'()*!"#$%&'()*!;98;
2"9;!1!
2%!910;0!
2%!910;0
04(14
04(14
016(3
/!"#!$##$:2##3!"#!$##$:2##3!"9#:
2"9;"112%!91;"#
1
2%!91;"#
56789:;<
789:;<!#9"1
2"9;#%#
2%!91!#8#
2%!91!#8
82IJ<
04(13
!"#$%&'()*+,!"#$%&'()*+,04(13
015(4
!"#$
%&'(
$!!9!"%&'(
2"9;#%8
2%!91%1<
8
2%!91%1<
After
Tuning:;<=%&'(%)*+,-./:;<=%&'(%)*+,-./
*+
).2+
).34+
!89!%
2"9;#!02%!91<0!
).34+./0/41211953/4/1257:;
02%!91<0!
./0/41211953/4/1257:;!%9#1
2"9;#1!
2%!9111#!
2%!9111#
04(34
04(34
015(3
!;9"%
2"9;!#1
2"9;!1! 2%!911!"
2%!910;02%!910;0
1!!;98;2%!911!"
04(14
04(14
016(3
!19#1
2"9;!%%
2"9;"11 2%!90#%82%!91;"#
2%!91;"#%1!"9#:2%!90#%8
04(33
04(33
012(4
!09#:
2"9;!""
2"9;#%# 2%!91<0:2%!91!#8
2%!91!#8"#!#9"12%!91<0:
04(13
04(13
015(4
!<9"1
2"9;!0;2%!908<<2"9;#%8
2%!91%1<
2%!91%1<;8!!9!"2%!908<<!:9"82"9;8"82"9;#!0 2%!90"!<
2%!91<0!
2%!91<0!
./0/41211953/4/1257:;012(3./0/41211953/4/1257:;
80!89!%2%!90"!<
04(>4
04(>4
8"9!"
2"9;!1<
2%!90#!8!%9#1
2"9;#1!
2%!9111#!
2%!9111#<2%!90#!8
04(34 6353
04(34
5424
5323
2414
2313
14 015(3
13 63
54
8;9#!
2"9;8<#
2"9;!#1 2%!91#!"
2%!911!"63
2%!911!"#1!;9"%2%!91#!"%"98;
2"9;8!0?@AB(%789
2"9;!%% 2%!9%!%#2%!90#%82%!90#%8
Temperature[deg.C]?@AB(%789
0%!19#12%!9%!%#
04(33
04(33
012(4
!;988
2"9;#10
2"9;!"" 2%!91;"%
2%!91<0:2%!91<0:0"!09#:2%!91;"%?@A-,/,,R),/,,AA
2"9;!0;2%!908<<);!<9"12%!908<<,/,,AA
The
18th
KEKB
Accelerator
Review Committee (2013)
BC$D
BEF$D
!:9"8
2"9;8"82%!90"!<
8
2%!90"!<
D
BEF$D
04(>4
04(>4
012(3

+,-.%&'/* +,-.%&'/*!"#!$##$#%!"#!$##$#%&'()*)+,-.
&'()*)+,-.

024

Additionally, fine tuning was applied
to!"#$%&<()*+,all BPF’s.
023!"#$%&<()*+,!"#$%&'()*!"#$%&'()*+,-.%&'/* +,-.%&'/*

Amplitude[dB]+,-.%&'/*+,-.%&'/*

>?@AB
>?@AB
!"9:0
2"9;"!82%;90088
82%;90088
04(14
04(14
024
/!"#!$0$!12!03!"#!$0$!12!03!;9<;
2"9;"80
2%!9;%;#
0
2%!9;%;#
56789:;<
789:;<!09"82"9;";02%#9<1<80
2%#9<1<8
82IJ<
04(13
!"#$%&<()*+,!"#$%&<()*+,!"#$
%&'(
04(13
023
$!09<:%&'(
2"9;"0!
2%#9!0%;./0/412111;3/4/1257::!
2%#9!0%;./0/412111;3/4/1257:::;<=%&'(%)*+,-./:;<=%&'(%)*+,-./
*+
).2+
).34+
).34+
!<9:8
2"9;#"!
2%"9;<;;!
2%"9;<;;
8"9#"
2"9;":"
28:9:%1#"
28:9:%1#
04(34
04(34
014
!"9:0
2"9;"!82%;90088
8"9<:2"9;#<<
28:9!%%:
82%;90088<
28:9!%%:
04(14
04(14
024
2"9;"80 28<9;;%%2%!9;%;#
8#9:"
2"9;#8%2%!9;%;#%0!;9<;28<9;;%%
04(33
04(33
013
8!9<"
2"9;"00
2"9;";0 2809<::1
2%#9<1<8
0!09"82809<::1
2%#9<1<8
04(13
04(13
023
889<1
2"9;#1"2809!"%!
!09<:
2"9;"0!
2%#9!0%;./0/412111;3/4/1257::!
2%#9!0%;./0/412111;3/4/1257::"
2809!"%!
Before Tuning
8%9<!
2"9;":;
2"9;#"! 2819;"18
2%"9;<;;
2%"9;<;;;!!<9:82819;"18
04(>4
04(>4
034
8;9<#
2"9;#8:28;9<;0!
8"9#"2"9;":"
28:9:%1#"
28:9:%1#:
28;9<;0!
04(3404(34 63
6353
5424
5323
2414
2313
14 01413
54
63
2"9;#<< 28!98%!;
28:9!%%:%#9#"2"9;!"%
28:9!%%:%<8"9<:28!98%!;)*%7892"9;#8%28<9;;%%?@A-,/,,,0,/OA3,)*%7890%8#9:"28<9;;%%,/OA3,
04(33
04(33
013
8!9<"
2"9;"00
2809<::1
02809<::1
BC$D
BEF$D
D
BEF$D
2"9;#1"2809!"%!
"889<12809!"%!
2"9;":;
2819;"18;8%9<!2819;"18
04(>4
04(>4
034
8;9<#
2"9;#8:28;9<;0!
:28;9<;0!
!"#!$##$:2##3 /!"#!$##$:2##3
6353
5424
5323
2414
2313
14
13
54
63
2"9;!"%
28!98%!;63%%#9#"28!98%!;56789:;<
789:;<
2IJ<)*%789)*%789!"#$%&'()*+,-,/,,,0 %&'(,/OA3,
0 %&'(,/OA3,!"#$!"#$%&'()*+,$?@A:;<=%&'(%)*+,-./
BC$D
BEF$D
D
BEF$D
*+
).2+
).34+
:;<=%&'(%)*+,-./
).34+

[dB]
+,-.%&'/*+,-.%&'/*Amplitude!"#!$##$#%!"#!$##$#%&'()*)+,-.
&'()*)+,-.

Phase[deg.] !"#$%&'()*!"#$%&'()*>?@AB!"#$%&'(%)*+,-./!"#$%&'(%)*+,-./
014
024

Phase
013
023

sample data./0/128#63/4/=;2;##./0/128#63/4/=;2;##

Before Tuning034
54 01463 53

013

54 24

53 23

24 14
23 13
14
13
)*%789)*%789./0/128#63/4/=;2;##./0/128#63/4/=;2;##0.67 deg. / deg.C

034
63 53
54

54 24
53 23
24 14
23 13
)*%789)*%789!"#$%&'()*+,!"#$%&'()*+,!"#$%&'(%)*+,-./!"#$%&'(%)*+,-./

14

13

016(3

Phase [deg.]!"#$%&'()*!"#$%&'()*>?@AB./0/1211##3/4/562785./0/1211##3/4/562785
015(4After !"#$%&'()*+,Tuning!"#$%&'()*+,!"#$%&'(%)*+,-./!"#$%&'(%)*+,-./
015(3
016(3

0.008 deg. / deg.C

012(4
015(4

012(3
54015(36353

012(4
012(3

./0/1211##3/4/562785./0/1211##3/4/562785
5424

5323

2414
2313
)*%789)*%789Temperature[deg.C]

1413

14 /17

Improved Thermal Stability of the System(measurement results)
α-ver.

Amplitude

Phase

α-ver.
Lumped Circuit Type BPF

0.09 dB2 deg.C

2 deg.C-0.52 % / deg.C

0.5 deg.C

β-ver.
-0.25 deg. / deg.C

0.01dB = 0.115%

β-ver.
8 deg.C

Cavity Type BPF& Fine Tune

Case of compensation withthe reference channel.

-0.06 % / deg.C
0.04 dBPhase

0.09 deg. / deg.C
8 deg.C

8 deg.C

0.16 deg

0.7 deg

0.02 deg. / deg.C

The 18th KEKB Accelerator Review Committee (2013)15 /17

Schedule of Production and Installation
FY2012FY2012
FY2012FY2012
4 5 6 7 8

9 10 11 121

FY20133 4 5 62

7

8

9 10 11 121

FY20143 4 5 62

7

8

9 10 11 12

1

2

3

Acc. Operation
Total Operation Test
Beam Commissioning
MR LLRF System
α-version

α-ver. HP Test@D8

β-version Production & Setting up
Evaluation & Tune-up

HP Test@D4

Practical system

Quantity Production ( 8 Systems )Installation & Op.Test @ D5&D4

Damping Ring LLRF (3-cavity control)
Test model
uTCA Test Model Manufacture
Practical system

The other stations depend on the budget.
Evaluation
Production
Installation & Op. Test

Reference Distribution
Opt. Transceiver System Test Model Manufacture

Opt. Cables

Evaluation
Production of Opt. Transceiver System
Installation & Op. Test
Installation of Opt. Cable• High-power (HP) test of the α-version was performed last year, then the result was reflected into β-version.
The HP test of the β-version is scheduled in march 2013.

• 8 new systems (actual operation model) will be produced and installed in D5 & D4 station in FY2013.
For the DR, uTCA test model will be evaluated soon, and the practical production will also start in FY2013.

• Optical transceiver system and cables will be also installed in FY2013 for the reference distribution.
The 18th KEKB Accelerator Review Committee (2013)16 /17

Summary• High power test of the prototype system (α-version) was performed, and
FB control and auto tuning control worked successfully.

• Very good FB stability was obtained in “out of the loop” measurement.
(0.02% in amp. & 0.02 deg. in phase)• Large klystron phase shift, depending on input power, was found due tothe efficiency optimization. This loop phase shift might be critical problem
for the I/Q FB control, therefore KLY-PLL function should be implemented
into the FPGA as the future issue.

• Thermal stability was improved by BPF tuning, then acceptabletemperature coefficient was achieved (0. 06%/deg.C in Amp.
deg.C in Phase)

0.02 deg./• Most of the practical system will be produced and installed in FY2013.

The 18th KEKB Accelerator Review Committee (2013)17 /17

Thank you for your attention !

The 18th KEKB Accelerator Review Committee (2013)18 /17

Followed by Backup Slides

The 18th KEKB Accelerator Review Committee (2013)19 /17

Low-level RF for KEKB Superconducting cavity

KEKB-LLRF System (Present)interlocks

from RFreference line

Phase Lock Loop
combiner for klystron

klystron circulator

Tuning Control Loop

SW
out

out

FBC
ref.

out

FBC

FBC

FB

ref.

φ det.

FB

ref.

FB

φ det.

FBC

Tuner
Controller

FB

klystron out

tuner

out

FBC

Present LLRF
System of the KEKB
( for one klystron )

KLY
cont.
Gain
Controlfor klystron
Lop

outK. Akai et al. / Nuclear Instruments and Methods in Physics Research A 499 (2003) 45–65

ref.
offsetφ det.

DL

beam

FB

Vc setcavityDirect RF
RF Feedback
DirectFeedack
SW

pick up (Vc)

Amplitude
Amplitudecont.
Control Loop
for VcFig. 2. RF station for the SCC cavities.

Phase Lock Loop for Vc

Phase Lock Loop

RF input

S-cav

A-cav

coupling
accelerating
cavitycavitystorage cavity

ARES Tuner Control
Configuration

c-dampers-tuner

BPF

beam signal

BPF(RF ON)a-tuner
BPF

BPF

BPF

φsg
φsb

(RF OFF)φac

for ALC and PLL

The 18th KEKB Accelerator Review Committee (2013)

Fig. 3. Tuning control.

20 /17

The -1 mode feedback• Beam current was limited due to the -1 mode
instability at 1 A in LER and 1.2 A in HER, much
lower current than expected.
• The -1 mode digital feedback selectively reduces
impedance at the driving frequency.
• After the -1 mode feedback was installed, thebeam current could be successfully increased.

1600
1400
1200
1000

Stored beam current

800
600
400
200
0

Feedback off
3:30 PM
03.6.30

Feedback on

3:45 PM

4:00 PMDate

FB OFFƒrf - ƒrev-40

ƒrf - ƒrev + ƒs

(a)

-0.97

-0.95

-60
-80
-100
-120

-1

-0.99

-0.98

-0.96

Frequency Δƒ/ƒrev

-1 mode sideband

FB ON
ƒrf - ƒrev

-40

(b)

-60

ƒrf - ƒrev + ƒs

-80
-100
-1

The 18th KEKB Accelerator Review Committee (2013)

-0.99

-0.98

-0.97

-0.96

Frequency Δƒ/ƒrev

-0.95

21 /17

Bode Plot of ARES FB cont.
QL=27000Δω = 0Loop Delay = 2us

Klystron band = 100kHz(Q0=110000, Coupling=3)

Amplitude @dBD
10

10k

Pgain=2.5, Igain=2.0e50Pgain=2.5, Igain=0.5e5

-10
-20

100k

Frequency @HzD
Pgain=2.5, Igain1M=4.0e5

Open Loop(Cavity Band)-30

Gain Margin :~20dB@100kHz
Pmax ~ 5-40

The 18th KEKB Accelerator Review Committee (2013)22 /17

Discrete Fourier Transformof the stability measurement in the page 8

0.005

Amplitude

0.005

0.004

0.003

0.003

0.002

0.002

-100dB

0.001

0.001

0.000

Phase

0.004

0.000
0

0

500

1000

1500

250
Frequency [kHz]

2000

500

0

0

500

1000

1500

250

2000

500

Frequency [kHz](Δf = 250Hz)

The 18th KEKB Accelerator Review Committee (2013)23 /17

Thermal Stability (2012)
for acc. gradient+/- 1% in Amplitude+/- 1 deg. in Phase

Required Stability
Our target value of the stability

for LLRF System+/- 0.3% in Amplitude+/- 0.3 deg. in Phase(pk-pk)Ambient Temperature Change : about +/- 2 deg.C

Acceptable
Temp. Coefficient

0.1%/deg.C in Amplitude
0.1 deg./deg.C in Phase
LLRF system total

Measured Result
The 18th KEKB Accelerator Review Committee (2013)

Amplitude: 0.5 % / deg.C
Phase: 0.25 deg. / deg.C
Requirements are not satisfied.

24 /17

Phase Difference between two Vectors
⎡ IK
K=⎢
⎢⎣ Qk

Q


K

φ

θ

ΔI =

I c I K + QcQk
I c2 + Qc2


Δ

⎤
⎥
⎥⎦

⎡ I Δ ⎤ ⎡ cos ( −φ ) − sin ( −φ ) ⎤ ⎡ I K
⎥⎢
⎥=⎢
Δ≡⎢
⎢⎣ QΔ ⎥⎦ ⎢⎣ sin ( −φ ) cos ( −φ ) ⎥⎦ ⎢⎣ Qk


C

θ
φ
ΔQ =

⎡ IC
C=⎢
⎢⎣ QC

⎤
⎥
⎥⎦

cosφ =

Ic⎤⎥⎥⎦, sin φ =2

I c2 + Qc

Qc
I c2 + Qc2

I−Qc I K + I cQk
I c2 + Qc2

Δ Q −Qc I K + I cQk
tan θ ==ΔI
I c I K + QcQk
The 18th KEKB Accelerator Review Committee (2013)25 /17