Beam Diagnostics
The 20th KEKB Accelerator Review
2015/2/24
M.Arinaga, J.Flanagan, H.Fukuma, H.Ikeda, H.Ishii,
S.Kanaeda, K.Mori, M.Tejima, M.Tobiyama

Contents• Overview• Beam Position Monitor System（BPM）• Photon Monitor System• Others• Schedule• SummaryInstrumentation at SuperKEKB
SystemQuantity
HER

LER

DR

Beam position monitor (BPM)

466

444

83

Displacement sensor

110

108

0

Transverse bunch feedback system

2

2

1

Longitudinal bunch feedback system

0(1)

1

0

Visible SR size monitor

1

1

1

X-ray size monitor

1

1

0

Beamstrahlung monitor

1

1

0

Betatron tune monitor

2

2

1

Beam loss monitor

207

34

DCCT

1

1

1

CT

1

1

0

Bunch current monitor

1

1

1

BPM
CABLESTBT MONITOR
LIBERADISPLACEMENT SENSORSVERTICAL COLLISION FEEDBACK

BPM system at Phase 1
Type

Function

Resolution

Repetition

Narrow-band system Closed orbit
from KEKB
correction, CCC,
optics measurement

3mm

0.25Hz109 (alreadyhave.)New narrow-bandwith 509MHz
detection

As above

2 to 3 mm

0.25Hz133

Gated turn by turnInjection tuning,
optics measurement

50 - 100mm

100kHz116

Medium-band

Measurement oforbit variation< 2 to 3 mm

10～100kHz

4

One narrowband detector covers four BPMs.

Number ofunits

Installation of BPM cables and displacement sensors

H.Fukuma•Installation of BPM cables will be finished by theend of March, except for seven in the arc section
near Tsukuba.
•131 displacement sensors have been installed.
68 will be installed after the alignment of
sextupoles, so as not to interfere with thealignment.
Cabling at a BPM head.

Restored displacement sensor.

Cable rack detouring the Belle detector.

M.Tejima

BPM 3DPKFLX Cable
40

Type-1a••

Shape of the insulator was changed to more securely
attach the insulation of the outside conductor of theconnector and the inner conductor.
The impedance at the terminal part was improved.

43

0°
5.
4

46

27

L=46+27+2+40+43=158

106

Type-1b
R 15

86
R 15

L=86+27+2+40+43=198

146

Waveform of TDR

M.Tejima

1.5D semi-rigid cable

Waveform of TDR

There is more outgassing with the 0.2 m cablewith SMA connectors (blue) than there is withthe 1 m cable with no SMA (red). We can use
the cable in the cryostat.

M.Tobiyama

Gated turn-by-turn monitors• Found soldering problems at BGA chips (FPGA and DDR3
memory).
– Re-heat and re-work around BGA patterns for all units.
– Installed DDR3 memory check code in FPGA FW.
• 509MHz CW calibration for all units.
– Convert ADC counts to power (dBm).
– Beam position conversion from power.
• Starting installation to local control rooms.
– L2 SW-HUBs and 1U servers are ready.
– 116 units will be installed (HER 58, LER 58).

M.Tobiyama

1421B Gated turn-by-turn monitor

FPGA, DDR3
SAW filters andLog Amplifiers,
ADC

Fast Gate Switch

M.Tobiyama

X-ray image of BGA soldering

NG ballM.Tobiyama

Calibration, position re-calculation• 7th polynomial fit for ADC.
• 3rd polynomial fit for position
calculation.

M.Tobiyama

RF distribution

Gated TbT

1U Linux Server

S.Kanaeda

Medium band monitor• We use 4 Libera Brillinace+.
• These monitors measure thebeam orbit:– To estimate verticaloscillation at IP,– To estimate verticalemittance growth due to
sextuple magnets.

10k
10k

Required specification
to a narrow band detector Repetition[Hz]BPMswitchLiberaControl
modulerevolution

Resolution[μm]10k to 100k(TbT)<5

S.Kanaeda

Orbit interlock monitor• We use re-modeled Libera brilliance+ by
Instrumentation Technologies.
– Evaluated latency < 4truns (threshold±10mm)• 2 in HER will be installed in Phase 1.

• 2 in LER are to be installed in Phase 2
because a new abort window will be
installed at this moment.
• These monitors will be used exclusively forthe orbit interlock.
• A TTL abort signal from Libera is converted
from electric to optical signal, then sent toan abort collection module.

BPM

copperLiberarevolution

E/O

optical fiber

Abortcollection
moduleSynchrotron oscillation
monitor

S.Kanaeda• The monitors will work at Phase 1.
• Re-use 508MHz IQ detectors, switches,
VME –based ADCs, timing modules,
NIM-based attenuators, phase shifters.
• A new NIM module which controls theswitch and attenuators was produced
last year.
• All the components have beenchecked.
• Read out of ADC data through EPICS
has been checked.
to a narrow band detector

BPM

ATT

switchI/Q
detector

sin
ADC
cos
timing control

RF
Control
modulePhase
Shifterset point

H.Fukuma

BPM displacement sensor(A talk requested in the ARC2014 report)•The movement of beam position monitors (BPMs) due to the thermal stress on
vacuum chambers has been observed in KEKB, even though they are fixed toquadrupoles.
•In order to correct the BPM data, displacement sensors were introduced at all
the BPMs near sextupoles, because orbit change at the sextupoles causes
vertical emittance growth and tune change.
LER

BPM

HER

BPM

supportsupport

H.Fukuma
Movement of arc BPMs relative to nearby
sextupoles at a beam abort in HERmm

HER Horizontal

Vertical tune change calculated from the
movement of sextupoles

mA

out

beam currentin

1 hourtime

x 10 sec•BPMs move 0.9mm (max.) horizontally and 0.1mm (max.) vertically.
•It takes 30 to 40 min. to reach steady state after the following injection.
•Movement of the BPM depends on beam current.
•Vertical tune change is well explained by the movement of sextupoles.

H.Fukuma

Gap detector
Specifications
detection methodchannels

electrostatic (capacitive)
2

range (mm)0.5 - 2.5

resolution (µm)

< 0.2nonlinearity (%)< ±0.3frequency response (Hz)0 - 100

temperature
coefficient (µm/deg.)< 0.2

sensor head

H.Fukuma

Displacement sensor for rotatable sextupole at SuperKEKB LER•In SuperKEKB, the displacement sensors used in KEKB will be reinstalled at the BPMs near the every sextupoles.
•Special sensor supports made of Metal Matrix Composites with low
thermal expansion coefficient of 3 10-6 /K are used for the sensors
near rotatable sextupoles in LER.
The support has a long pillar because it can not be mounted on the
movable sextupole.
BPM

sensors

Alignment tolerance of LER sextupole (r.m.s.) (H.
Sugimoto)

pillar

Evaluated based on vertical emittance growthTypeDX(um)

DY(um)

SF

100

60

SD

40

30

SL

40

20

Installed rotatable sextupoles :SL 8, SF 8, SD 8 total 24

rotatable
sextupole
Displacement sensor near a rotatable sextpole.
Currently 15 sensors are installed.

H.Fukuma

Data of vertical displacement
red : temp. of chamber, green : MMC temp at pillar top, blue : temp. in air

pink : vertical gap

H.Fukuma

Simple model

1
1+ τ ⋅ s

deformation

measured gap

First order lag
T(t) : temperaturea : temperature coefficientd(t) = a(T(t) − T(0))

Deformation

Output (measured gap)
Impulse responsec(t) = ∫ 0 d(u)⋅ g(t − u)du =
t

um

a

−

t −u

(T(t) − T(0))⋅ e τ du
∫
τ
t

0

um Temp. : Chamber

Temp. : Air

red : c(t) by simulation
green : measured (signis reversed.)

a=8.5um/K, τ=5min

a=8.0um/K, τ=40min.
min.

min.

•Gap change between the sensor and the target has strong correlation with the chamber
temperature. The mechanism of the deformation of a structure is not clear yet.

H.Fukuma

Simulation of vertical collision feedback(Work recommended in the ARC2014 report)•The simulation of the vertical collision feedback was done by Simulink using
time series of disturbance generated from simulated vertical oscillation of QC's.

PSD (QC1R, L)

radPhase (QC1R)

These parts areintentionallyadded toYamaoka's datato get the timeseries.

Hz

Simulated oscillation of QC by ANSYS by H. Yamaoka

H.Fukuma•Correlated time series are generated from the oscillation data of the quads.
FFT of generated time series (QC1R{E,P})
2 SQC1RE,QC1RE

red dot : FFT of generated time series
green line : data from which time series is generated.
2 SQC1RP,QC1RP

auto-correlation

auto-correlation

QC1RP

QC1RE

2 SQC1RE,QC1RP

cross-correlation

((

) (

θ = tan−1 Im SQC1RE,QC1RP /Re SQC1RE,QC1RP))cross-correlation(phase)•A macro electron and a macro positron are tracked by the 4x4 transfer matrix.

H.Fukuma•The particle is vertically kicked at QC1's and QC2's due to their position shifts.

yp*-ye*(m)Positron-electron orbit difference at IP

4.5secturn• This orbit difference is put into the Simulink model as disturbance.
• A model of TAKASAGO power supply is taken into account in the Simulink model.

H.Fukuma•Result of Simulink shows that r.m.s. amplitude is reduced to 1/4 by the feedback.

blue : disturbancer.m.s. : 29.3nm, p-p : 183nm±σ*y

red : reduced oscillation by feedback
r.m.s. : 7.5nm, p-p : 52nm

H.Fukuma

Power supply controller for IP orbit feedback•A power supply controller for IP orbit feedback is being developed.
It will be completed in FY2014.
•The controller has two control paths.
-Fast control from the vertical orbit feedback controller (update rate 32kHz) for vertical feedback-Slow control via EPICS channel access(CA) (update rate 1Hz) for horizontal feedback, verticaland horizontal DC bump
Fast and slow set values are added in the controller to get the set value to the power
supplies.
•Functions-Variable gain to adjust granularity.
-Adjustable delay for individual power supplies.
•Controller-Conforming to MTCA.4
RTM(Rear Transition Module), FPGA board, DAC on FMC(FPGA Mezzanine Card)-16bit DAC-EPICS IOC embedded.
-FPGA : Xilinx Zynq SoC

H.Fukuma•Response of a Takasago power supply was measured.
Scope

Tektronix TDS350P
200MHz, 1GS/s

search coilPower supply
Takasago BWS 40-7.5
Output voltage : +/- 40V
Output current : +/- 7.5A
reference

Function generator

Magnetic core : a corrector of KEKB
Coil : 120 turns in total

Tektronix AFG320

H.Fukuma•Step response of magnetic field excited by the power supply can be approximatedto 2nd order lag.
•The system is under-damped system.
Kω n2T(s) = 2
s + 2ζω n s + ω n2
 1 − ζ 2 −ζω n te
 1 − ζ 2 ω n t + ArcTan
V (t) = K 1 −sin
 ζ 
2


1−ζ





Raw data

fit

data

ζ = 0.401, ω n = 0.0137 × 10 6 rad /sec

100us

f n = 2.18kHz
Coil output was integrated to get
the magnetic field.
t(us)H.Fukuma•Disturbance rejection using the transfer function of 2nd order lag for the
power supply was calculated by Simulink.

The result below100Hz is almost same as that for the 1st order lag.
A resonance-like peak near 2kHz is enhanced.
This peak almost disappears if a transfer function of critical damping is used
for the power supply.

PHOTON MONITORS
SRM
XRM
LABM

Photon Monitors

J.Flanagan• SRM: Synchrotron Radiation Monitor– Visible light monitor. Interferometer, streak, gated camera,etc.
– σz, σx (σy)• XRM: X-ray Monitor– Pinhole, Coded Aperture mask, etc.
– σy (σx)• LABM: Large Angle Beamstrahlung Monitor (IR)– SR-like radiation from interaction point (~300-600 nm)– Can measure size ratios and relative offsets at collision point.

SR Source Bend Parameterεx

S-LER1(BSWFRP)
3.20E-09

S-HER(BSWOLE)
4.54E-09

κ

0.27%

0.25%

εy

8.64E-12

1.14E-11

m

βx
βy

8.86
30.71

10.17
26.92

m
m

σx
σy
Beam Energy
Bend effective length
Bend angle
Bend radius ρ
Observation wavelength λ

168.4
16.3

214.9
17.5

µm
µm

4
0.89
5.04
179.0
4.00E-07
1.0

7
2.90
5.00
580.0
4.00E-07
0.7

GeV
m
mrad
m
m
mrad

0.2
0.9
90%

mrad
mrad

Max. Visibility (H) γmax

0.2
0.8
90%

Max. Visibility (V) γmax

98%

98%

Min. measurable beam size σx min

164.1

157.4

µm

Min. measurable beam size σy min

15.7

15.0

µm

SR Opening angle θc (λ)
Slits opening angle D/F (H)Slits opening angle D/F (V)

Units
m

J.Flanagan

SRM: Interferometers•Resolution fundamentally limited bymeasurement wavelength and opening
angle between slits from beam (D/F).
•Max. slit separation determined by beam
spread and mechanical considerations.

•Will primarily use for horizontal beam size measurements•Vertical beam size measurement is possible with interferometers, though isnear the limit of the interferometer resolution, and single-shotmeasurement is not possible.
•But can be useful for cross-calibration purposes at larger beam sizes.
•To minimize deformation due to heat load, will use gold-coated diamondmirrors.

SRM: Extraction mirrors and chambers J.Flanagan

Diamond extraction mirror for visible lightbeam size monitor in holder

Extraction chamber installed in tunnel.
(Vac. Group)

Mirror mounted in extraction chamber.

•Diamond mirrors for visible light monitors
have been installed in extraction chambers
and aligned.

J.Flanagan

SRM: 2015 Plans• Optical transport lines from tunnel to surface
to be installed Summer 2015.
– Largely re-using KEKB components, with somemodifications to reach new chamber location.

• Above-ground optical components to bereconstructed by Phase 1 turn-on.
• From Phase 1 turn-on:– Commissioning of SRM.

XRM: X-Ray Monitor
Xray Source Bend Par. S-LER(BS2FRP.1)
3.20E-09εxκ
0.27%
8.64E-12
εy
50.0
βy
σy
Beam Energy
Effective length
Bend angleρ
Critical Energy
•

20.8
4
0.89
28.0
31.7
4.4

J.Flanagan

S-HER (BS2E.82) Units
4.60E-09
0.24%
1.10E-11
11.5
11.3
7
5.9
55.7
105.9
7.1

m
m
m
µm
GeV
m
mrad
m
keV

59-element Uniformly
Redundant Array mask pattern

Coded Aperture Mask:••

In-hand :•High-power, 59-element, 10 µm/element URA•
10 µm Au mask on 625 µm Si substrate•
Under development:•
20 µm Au mask on 500 µm CVD diamond (monocrystalline) substrate•
Substrates manufactured.
•
New pattern being designed for improved resolution (E. Mulyani)
Detector:•
64-pixel (Phase 1), later 128-pixel, 50 µm pitch linear array•
InGaAs detectors in hand (same type as used at CesrTA)•
Deep Si detectors in development for better detection efficiency at high energy (SLAC)

Simulated detector
response for various
beam sizes at
SuperKEKB LERXRM: Hardware•••

J.Flanagan

All vacuum components (beam pipes, optics box, Be filters and windows, beam
stopper and gate valve, etc.) have been delivered or ordered, except for screen
monitors for beam-based alignment.
64-channel prototype high-speed readout system and detector mount made (U.
Hawaii). Firmware under development.
High-energy detector wafers processed and diced, and detector andspectrometer chips undergoing leakage testing. (SLAC)– Chips from first wafer show high leakage currents. Second wafer chips being tested.
– Need for second wafer run to be evaluated based on yield.
– Heat-sinking and mounting design of detector to follow.

High-speed readout electronics for the X-ray
monitor, being developed by U of Hawaii.

Deep Si pixel detector and spectrometer chips
for the X-ray monitor, being developed at SLAC.

J.Flanagan

XRM: 2015 Plans• Finalize firmware and fabricate 2 production model
64-channel high-speed readout systems. (UH)• Production of final detector and spectrometer chips,
and mount and heat-sink detectors. (SLAC)• Install and align x-ray beam lines at SuperKEKB (MayJuly), integrate detectors and readout systems (Fall).
• Initial commissioning with first beam at SuperKEKB.

J.Flanagan

LABM: Large Angle Beamstrahlung
Monitor••

The radiation of the particles of one beam due to the bending force of the
EM field of the other beam.
Beamstrahlung POLARIZATION at specific azimuthal points provides
information about the beam-beam geometry.

G. Bonvicini

J.Flanagan

LABM: Vacuum and Optical Components• Construction of optics boxes completed. (Wayne)• Optics boxes, optical components, and opticalbeam line components shipped to KEK from
Wayne State. (Wayne)• Extraction chambers fabricated, and test-fittingof extraction mirror and window carried out.
(KEK)
• Extraction chambers installed at the IP. (KEK)

Test fit of LABM
extraction mirror(left) and extraction
window (right) on IR
beam pipe.

Inside view of LABM
extraction mirror
inside HOMprotection slot in IR
beam pipe.

J.Flanagan

LABM: 2015 Plans•••

Install LABM beam lines, optics boxes andelectronics around IP. (Wayne State, KEK)
Calibrate system. (Wayne State)
Systematics checks with first beam at
SuperKEKB.

LABM extraction chamber at IP, withplanned locations of optical beam line
supports marked on floor.

OTHERSFBBUNCH CURRENT MONITORLOSS MONITORFAST BEAM DECAY MEASUREMENT (DCCT)
CLEARING ELECTRODESDR

M.Tobiyama

Bunch feedback system• Installed most of the vacuum
components (except LKickers).
• Re-arrangement of the lowlevel components in the FB
local control room
– Network cables– Replacement of NIM
power supplies.
– Removal of old two-tap
FIR filters, installed newcomponents such as new
detectors.

Longitudinal kicker

M.Tobiyama

Bunch current monitor/Memory• 8-bit ADC(MAX108)• Spartan6 FPGA on SODIMM daughter card (Mars
MX1)• 128MB DDR2 memory• BCM : Block RAM• BOR : DDR2 memory– 4k, 8k, 16k x 5120
– 20M, 40M, 80M• 1.1ms to transfer 5k data to
IOC (BCM)KEKB(H=5120), PF(H=312), AR(H=640),
DR(H=230) supported
EPICS Device support readyM.Tobiyama

Sine wave fit

RMS 0.5 counts, MAX error 2.2 counts

M.Tobiyama

Large data transfer• BLT (D32 block transfer) supported.
20

6
Time(s)515

Time(s)Time(s)

4
10

3
2

5
1
y = 0.2445 + 0.22999x R= 0.99938
0

0

20

40

60

80

Size(MB)BOR to IOC ~4MB/s

y = 0.0005002 + 0.069268x R= 0.99943
100

0

0

20

40

60

80

100

Size(MB)IOC to NAS (GbE+10GbE)~14MKB/s

7s for 20MB data transfer (vs. 5 min. with old BOR).

Loss Monitor•Installation of LM cables andsensors has finished except for IR
region.
•Read-out modules (integrator +interlock module, ADC) areprepared and cabling in control
room will be done soon.

Ion Chamber

Photo-diodePhoto-diodeM.Tobiyama

Fast beam decay measurement system• Keysight 34410A DVM– Can transfer ~5ksps data to
the host without data gap.

• Calculate using EPICS
sequencer– Mean, Injection rate, Decay
rate, Injection counts.
– 1st order fit to get decay
slope.

• Good agreement with
the input signal.

H.Fukuma/M.Tobiyama

Power supply system of clearing electrodes for electron cloud
mitigation•Clearing electrodes are installed in Oho and Nikko straight sections to mitigate theelectron cloud effect. The number is 52 in Oho and 60 in Nikko.
•Each electrode is powered by individual power supply.
•Cabling and installation have almost completed.
•Development of control software has finished (EPICS device support, CSS operation panel,
Batch generation of database).
•Application of voltage will be tried in this spring.
Specification of power supplyDC
voltage

1kV(bipolar bymanual switch)

Current

100mA

Voltagestability<0.01%

Voltageripple<0.01%(r.m.s)

Control

optical link controlled
via Ethernet

Power supply system for clearing
electrodes in Nikko B4.

Operation panel

DR
•
•
•
•

Most of sensors, electronics and cables are readyfor BPM,FB,SRM,LM and DCCT.
Cabling between ground floor and tunnel will bedone in 2015.
Chamber installation of each monitor will be donein 2015 or 2016.
Preparation of special monitor (bunch current
monitor, tune meter, synchrotron phase monitor
etc…) starts in 2015.

ScheduleSummary• The installation of MR beam diagnostics
system is advancing smoothly.
• DR schedule depends on components of othergroups.

backupConfiguration of main BPM system

Gated TbT

•Super-heterodyne detectors in KEKB
BPM system are also main detectors inSuperKEKB.
•Detection frequency in LER is lowered to509 MHz due to the chamber cutoff
frequency of 989 MHz.
•Selected 270 BPMs have gated turn-byturn monitoring function.

Gated TbT

M.Tejima

Mapping of 90x220 ante-ＢＰＭ
90x220 mapping step 1mm
0.8

0.6

90x2200.4

4030

Y [mm]

20
10
0

Y1

-10

Bu

-20

Map

-30
-40

(V1+V2-V3-V4)/Sum(V)

50

0.2

0

-0.2

-50
-120

-100

-80

-60

-40

-20

0

20

40

60

80

100

120

-0.4

X [mm]

-0.6

-0.8
-0.8

-0.6

-0.4

-0.2

0

0.2

(V1-V2-V3+V4)/Sum(V)

0.4

0.6

0.8

M.Tejima

ＬＲ detection• 電極の出力電圧

90x220 mapping step 1mm

V1, V2, V3, V4

25• ＬＲ回路の出力• ノーマライズ
H=P1-P2-P3+P4
V=P1+P2-P3-P4

15
10
P1+P2-P3-P4 [dB]P1=20Log(V1)P2=20Log(V2)P3=20Log(V3)P4=20Log(V4)

20

5
0
-5
-10
-15
-20
-25
-25

-20

-15

-10

-5

0

5

P1-P2-P3+P4 [dB]

10

15

20

25

M.Tejima

Re-calculation for beam positions
Re-calculation
by polynominal approximation

20

20

15

15

10

10

5

5
Y[mm]

Y[mm]

Re-calculation
by Linear approximation

0

0

-5

-5

-10

-10

-15

-15

-20

-20

-20

-10

0
X[mm]

 X = 0.943 ⋅ H
Y = 0.970 ⋅ V

10

20

-20

-10

0

10

X[mm]

 X = 0.917 ⋅ H + 0.00013 ⋅ H 3 − 0.00038 ⋅ H ⋅ V 2
Y = 0.945 ⋅ V + 0.00013 ⋅ V 3 − 0.00036 ⋅ H 2 ⋅ V

境界要素法で得たマッピングデータを使って、最小二乗近似で係数を求めた

20

H.Fukuma

Power supply controller board (conforming to MTCA.4)µRTM

FPGA board

FMC DAC board

FPGA

fast control#1

kick angle
θ(fast)#8

optical link

#9

ADDER

#12

slow control(EPICS CA)

slow control#1

RJ45
GbE

PHY

limiter

ADDER

SerDes

EPICS
IOC

#8
#9

linux

#12

ARM

kick angle
θ(slow)

ADDER

ADDER

delay

DAC

p.s.#12
limiter

delay

hold

r
r
 IV 
 IV  IV : 8 column vector r  = (M ) r 
I  I  IH : 4 column vector H  out
 H  in

M:12x12 matrix

RTM : Rear Transition Module
p.s. : power supply

holdcoupling correction

SFP

p.s.#1conversion from θ to I

fast control(from DSP01)

16bit

FMC : FPGA Mezzanine Card

DAC

M.Tobiyama

EPICS device support related difficulties• We’ve found the command order (read and write) on the
VMEbus changed during the debugging process of the EPICS
device support of BCM board, which destroyed the data order.
– Out-of-order operation of CPU (PPC5500).
– Rather rare event (about 10-3): fairly difficult to find.
• Needed to insert special command to guarantee theoperation order.
– There should be command to suppress such nasty“optimization” for the whole bus operation– no suchcommand has been prepared on (current?) VxWork 6.8.3.
– I’m not confident whether other device supports are OK ornot.

M.Tobiyama

Bus access as written by code

Address reset

Data readM.TobiyamaWrong order

Data read

Address reset

Data readH.Fukuma

Simulink model

disturbance file
outputreference
PID

eddy current(1st order lag.,t=0.21ms)

BPM (LPF : Kaiser 27taps)

power supply (2nd order lag.)A model of the TAKASAGO power supply is taken into account.