MOCB01	
BEAM INSTRUMENTATIONFOR THE SUPERKEKB RINGS	
M. Arinaga, J. W. Flanagan, H. Fukuma, H. Ikeda, H. Ishii, S. Kanaeda, 
K. Mori, M. Tejima, M. Tobiyama, KEK, Tsukuba, Japan	

G. Bonvicini, H. Farhat, R. Gillard, Wayne State U., Detroit, MI 48202 , USA 	

G.S. Varner, U. Hawaii, Honolulu, HI 96822, USA 	

International Beam Instrumentation Conference,
IBIC2012, Tsukuba, Japan, Oct. 1-4, 2012	

Introduction	
•SuperKEKB is an upgrade of KEKB B-factory.	

Major upgrades	

Very small vertical beam size with "nano-beam scheme"	 •New LER vacuum chambers	
Doubled beam current of KEKB	
40 times larger luminosity than KEKB.	
• The first beam is expected in the Japanese FY 2014.	
Ring
Energy (GeV)

HER(e-)
7

Circumference (m)Beam current (A)•New final focus system in theinteraction region (IR) 	
•New positron damping ring	LER(e+)
4
LER	

3016
2.6

Collision point (IP)	
BelleII	

3.6

Number of bunches

2500

Bunch separation (ns)4Bunch length (mm)(ante-chamber)	

5

Beta function @IP hor./ver. (mm) 25/0.30

HER	
632/0.27

Emittance (nm)

4.6

3.2

x-y Coupling (%)

0.28

0.27

Vertical beam size at IP (nm)59

48

Damping time trans./long. (ms)

58/29

43/22

LINAC	
e+ Damping Ring	Main Ring Instrumentations	

System	Quantity	Comments	

LER	

HER	

Beam position monitor (BPM)	

445	

466	

Closed orbit correction, slow orbit feedback,IR orbit feedback, optics correction	

Displacement sensor	

~100	

~100	

Measurement of displacement between the
sextupole and the BPM	Transverse bunch-by-bunch feedback	1	

1	

Suppression of beam instabilities	

Longitudinal bunch-by-bunch feedback	

1	

0	

Suppression of beam instabilities	

Visible light monitor	

1	

1	

Horizontal beam size, longitudinal bunch
profile	

X-ray light monitor	

1	1	

Vertical beam size measurement	Beamstrahlung monitor	

1	1	

Beam information at collision point (IP)	

Tune monitor	

1	1	

Loss monitor	

~300	

~300	

DCCT	

1	

1	

Reused from KEKB	Bunch current/fill pattern monitor	

1	1	

Revised from KEKB	

Ion chambers and PIN diodes	

Items colored orange are new in SuperKEKB.	

A luminosity monitor will be prepared by the Belle II group. 	

Beam Position Monitor System	
Button electrode for the LER	•Diameter : 6mm	•Flange type for easy replacement andfor removal during TiN coating of thechamber.	
•Pin-type inner conductor for tightelectrical connection.	
•Prototypes were sccessfully tested
at KEKB. 	

Button electrode	
BPM block (ante-chamber)	

1mA/bunch、1.5GHz scope, 50m cable	GdfidL simulation	

BPM Detectors	

•The KEKB detector was a 1 GHz narrowband superheterodyne detector module (VXI). 	

One narrowband detector covers four BPMs.	

•A main detector system of SuperKEKB follows that of KEKB in order to maximally use
KEKB system to reduce the cost. 	
•The narrowband detectors of SuperKEKB HER are reused from KEKB. 	

A new narrowband detector with a detection frequency of 509 MHz will be used for the
LER since the cutoff frequency of a new LER ante-chamber is below 1 GHz.	

•Additionally, turn by turn detectors will be installed at selected BPMs to measure theoptics during collision. 	
•Also, a special wideband detector is being installed for the BPMs closest to thecollision point (IP) for orbit feedback to maintain stable collision. 	
Type	Function	

Narrowband
KEKB	

closed orbit correction,
slow orbit feedback,optics measurement	

Resolution	

Repetition	

Quantity	

2µm 	

0.25Hz	117 	

(already we have.)	

New
as above	
narrowband	

2µm 	

0.25Hz	127	

Turn-by-turn	
 optics measurement
during collision	

50 - 100µm	
 100kHz	270	

IR feedback	

<1µm	

4	

collision feedback	

5kHz	509 MHz Narrowband Detector	
•Development of the 509 MHz narrowband detector is in final stage. 	
•Signal to noise ratio larger than 90 dB is achieved by 2048 points FFT andaveraging of 8 points with CW signal.	
S/N : 90 dB	

Resolution : 0.5µm	

•Final tuning to get better linearity and so on is in progress.	
•20 units will be produced in this FY as a pilot production.	
•Mass production of about 110 units is scheduled in the next FY.	
Superheterodyne detector (VXI module)	

BPM	

MUX 4:1	

Turn-by-Turn Detector with Fast Gate	
Purpose	1) Measurement of optics parameters during collision	•Detect oscillation of a non-colliding pilot bunch	•Calculate optics parameters such as beta functions and coupling
parameters from the bunch oscillation data	
•The pilot bunch is kicked by the bunch-by-bunch feedback system. 	
pilot bunch	

4 ns	

Bunch train	....	

~6 ns	

fast gate	2) Injection tuning	Block diagram of turn-by-turn detector	
•The detector has GaAs fast gates to select the signal of the pilot bunch. 	

Signals of remaining bunches are sent to the output port of the detector, which is connected to
the narrowband detector in order to enable the simultaneous measurement of the narrowband
detector and the turn by turn detector. 	
Fast gate	
glitch cancellation circuit 	
FPGA(Spartan6)	

Log amp & ADC	 Fast gate	Switch : Hittite GaAs MESFET, DC – 12GHz	
Log amp : ADL5513 (AD)	
ADC : ADS850 (TI)	

Glitch cancellation circuit (T. Naito)	
•A 0-π splitter and a combiner placed before and after the switches,
respectively, remove a common mode glitch of the switches. 	

glitch	

w/o glitch cancellation circuit	

gated with 6 ns pulse	•A test of the switches shows the isolation larger than 85 dB.	
•The detection by the narrowband detector connected to theturn-by-turn detector was not affected by the switches at alaboratory measurement. 	

with glitch cancellation circuit	IR Feedback Detector 	•Detect vertical orbit shift at BPMs by the beam-beam kick when
two beams collide with a vertical offset.	
Orbit shift at BPMs : 1.3 µm @ 0.1σy* offset at IP 	
•Steer the beam position and angle at IP to reduce the offset.	
•Main sources of orbit movement : vibration of quadrupoles
closest to IP	
Main frequency components : 3, 36, 53Hz (simulation)	
•Tentative specification for R&D of the detector	
Resolution< 1 µm	 Repetition

5kHz

	
 

Hz	

Bandwidth

1kHz 	
 Movement of QC1RP by a simulation (H. Yamaoka)	

a) Detector	

Prototype	•Down-covert 508.8MHz component tointermediate frequency (IF) of 16.9 MHz
with an analog mixer to reduce thedegradation of the SNR by the clock jitterof ADC.	

Analogue part	•AD conversion 	
•Digital filters (2 CICs, 1 FIR)	

µTCA	

analogue down converter	

Digital part	•Position calculation	

Digital processor board	
•The digital part is implemented ina µTCA board developed for
SuerKEKB LLRF system.	

•EPICS is embedded in the board.	

b) Performance of the prototype	

Phase noise of clock out	

•Analogue part	- Clock jitter 1.30 ps	

100dBc/Hz	

- Noise figure 14.3dB @ 16.9MHz	

- Temperature coefficient of IF signal-0.03dB/deg.	

•Frequency characteristics of the digital filter	

100kHz	

10Hz	

dB	

•Resolution (CW input)	
120 dB	y(nm)	

1 kHz	

Attenuation is as expected.	

σx=47nm	Hz	x(nm)	

σy=60nm	Chamber radius 10mm	

•First prototype had a group delay of 3.3 ms.	

A simulation shows that the group delay should be less than 1ms to getenough rejection gain against the disturbance (i.e. 10dB@50Hz). 	
The group delay will be reduced to less than 1 ms by reducing the taps of the FIR.	

Synchrotron Radiation Monitor	

We will install three kinds of synchrotron radiation monitor. 	
1)Visible Light Monitor	

•Streak camera ：longitudinal profile	•Interferometer ：horizontal beam size, (vertical beam size)	
Vertical beam size at source point：16µm(LER), 19µm(HER) 	

A vertical beam size measurement is near the limit of theinterferometer resolution.	

2)X-ray Monitor	

•Coded aperture imaging and pin hole：vertical beam size	
3)Large Angle Beamstrahlung Monitor	
•Measure relative offsets and size ratios of the beams at the collision point. 	

Visible Light Monitor	

a) Diamond mirrors	•Incident power on the extraction mirror : 280 W ~ KEKB HER.	
•Since the heat deformation was already a problem at KEKB, we are developing
a diamond mirror that would not deform as much under the same heat load.	

Quasi-monocrystalline diamond	Diamond mirror	

•Diamond surface is nearly a single crystal. Good surface smoothness
is expected (Ra ~ 2 nm, <~λ/50).	

(Surface: 3 µm Au)	•10 mm x 20 mm x 0.5 mm and 20 mm x 20 mm x 1 mm prototype completed.	

•Very good heat conductance and low thermal expansion coefficientmake apparent change in magnification smaller than that of Be mirrors
used at KEKB.	

Mirror	Surface Deformation (ANSYS simulation)	
m	

Holder	
2 µm	

•Heat deformation is being
measured.	

20 mm	m	
Be mirror	( 200W SR power)	

Diamond mirror	

( 400W SR power)	

To be presented in TUPB74. 	

X-ray monitor	
a) Coded aperture imaging	•Developed by X-ray astronomers.	
•Light from an object is modulated by a mask.	

1D Uniformly Redundant Array (URA) mask 	

•The resulting image must be deconvolved
through mask response including diffraction andspectral width by Kirchhoff integral over mask
to reconstruct the object. 	
•Large open aperture of 50 % gives high flux
throughput for bunch-by-bunch measurements
which will likely be needed for low-emittancetuning. 	

•The method has been successfully
tested at CesrTA.	
red : data	green : fit	•A heat-sensitive and flux-limiting monochromator is not needed. 	

object	mask	

reconstructedrecorded image	 reconstruction	
 object	

Measured and simulated image
at CesrTA (σy =~ 25 µm)	(J. W. Flanagan et al., IPAC’10）	

b) Simulation in SuperKEKB	
•Vertical beam size at source point：21µm(LER), 11µm(HER) 	

Red points : using a 64-pixel Fermionics detector	
Green points : using a hypothetical detector
with improved photon detection efficiency at
higher x-ray energies.	

Detected image or pattern in SuperKEKB	

Estimated single-shot resolutions
limited by photon statistics	
Resolution at true beam size of 10µm is±2.5µm with the Fermionics detector. 	

c) Mask	

•Tests at CesrTA show the URA mask gives predicted singleshot resolution.	

•A Si mask was successfully tested at SuperKEKB full current
power load in CesrTA.	

•A diamond substrate mask was also fabricated and installed at
CesrTA, and ready to be tested.	

Diamond+Au mask	
Minimum slit width 10µm	d) Detector and readout	

•The base line detector is the Fermionics photon
detector. 	
•A digitizer is STURM (Sampler of Transientsfor Uniformly Redundant Mask) ASIC for highspeed readout developed at U. Hawaii. 	
•A 64-channel system where a
Fermionics detector, a preamp board
and a STURM digitizer board are
integrated on a motherboard is being
developed for testing at ATF2. 	
To be presented in MOPB72. 	

Detector	

64-channel system	
Digitizer ASIC	

(STURM2)	

Large Angle Beamstrahlung Monitor(LABM)	
•Proposed by G. Bonvicini, then tested at CESR.	
•Beamstrahlung is the radiation of the particles of one beam due to thebending force of the electromagnetic field of the other beam.	

•Beamstrahlung polarization at specific azimuthal points provides
unique information about the beam-beam geometry.	

•The LABM for the SuperKEKB is being built
in the US, mostly at Wayne State University. 	

Beam	

Polarization	
U y /U 0

Observed at φ = 90º	€A positron is vertically deflected by the electron beam.	
M. Bassetti et al., PAC1983	

Null polarization	
U : Polarization vector	
 U x /U 0
G. Bonvicini et al., PRE 59 (1999). 	

€a) Setups	

Optical channel	

Optical Box	Tunnel floor	Optical box	• Light is transported through an opticalchannel to an Optical Box. 	
Optical Box	

2.0 X 2.8 mm2	•The monitor consists of four viewports. 	

•Light is separated into two transverse polarizations
and four different wavelength bands. 	

•At full SuperKEKB luminosity, the photon flux at the primary mirror is of theorder 1012 Hz, and a factor of 50-500 lower for each individual electronic channel. 	

Bunch-by-Bunch Feedback System	
Transverse feedback system	

•Since the horizontal tune is near the half integer, several turns are needed to observe
the orbit change at the monitor if the phase relation between the source of the kickand the monitor is not suitable. 	
Two sets of short stripline kickers which cover two feedback loops with 90
degrees phase difference will be installed in each ring. 	
•The design of the kicker is similar to that of a present KEKB kicker. 	

The shunt impedance of 10k ohm per kicker is expected. 	
•Power amps are old four 250W-amps and new four 500W-amps in each ring.	
pickup	
kicker	comb filter	

power amp	
digital filter	a) Pickup and Low noise front-end	

•The button electrode has a glass feedthrough sealing
with low relative dielectric constant of about 4 which
has good time and frequency response. 	
•The detection frequency is 2 GHz. 	
•A 2 GHz comb filter is used to cut low frequency noise
and to improve isolation between bunch signals. 	
•A difference signal is mixed with LO with frequency of 4 x RF
frequency, amplified to increase gain, fed to 600 MHz Bessel LPF
then amplified by a DC amp. 	

comb filter	

Test circuit	b) Digital filter	

•The iGp processor is a baseline system.	

•It was developed under US-Japan
collaboration (KEK-SLAC-INFN-LNF ).	

1.5GSPS 8 bit ADC, 600MSPS 12 bit DAC 	FPGA Vertex II	•Successfully tested for the transverse andlongitudinal system at KEKB androutinely used in longitudinal feedback at
KEK-PF.	

•The ADC is upgraded to 12 bits system
to extend dynamic range in order tocapture large offset signal due to thebeam-beam kick. 	

iGp processor	Longitudinal feedback system	

•A growth rate of the longitudinal coupled bunch instability due to theimpedance of ARES cavities in LER is 15 ms which is shorter than thelongitudinal radiation damping time of 22 ms.	
The longitudinal feedback system is indispensable in LER. 	
•Four DAFNE type kickers, with 2-input, 2-output ports
will be used to get larger capture range.	
•Two 500W- amps per kicker are used. 	
•The frontend electronics and the digital filters
are same as those of transverse system. 	
•The design of cavity has started. 	

So far the shunt impedance of 1k ohm at 1.15GHz and the
bandwidth of 225 MHz are obtained by a HFSS calculation. 	

HFSS model of the kicker	
kicker	Summary	
•The electron-positron collider KEKB B-factory is currently being upgradedto SuperKEKB. The first beam is expected in the Japanese FY 2014.	
•The BPM system will be equipped with the super-heterodyne detectors, theturn-by-turn log ratio detectors and the IR orbit feedback detectors.	
•New X-ray beam profile monitor based on the coded aperture imaging
method will be installed. 	

The large angle beamstrahlung monitor detecting polarization of thesynchrotron radiation generated by beam-beam interaction will be
installed near IP. 	

The diamond mirror for the visible light monitor is being developed.	
•The bunch-by-bunch feedback system will be upgraded using low noise
frontend electronics and new 12 bits iGp digital filters. 	
•The beam current monitor, the tune monitor and the loss monitor are
mostly reused from KEKB.	

Acknowledgments	
•The authors would like to thank the KEKB vacuum group for
manufacturing BPM chambers. 	
•They also thank Prof. J. Fox for valuable advices for the
instrumentation system of SuperKEKB. 	
•The authors thank staffs at Cornell University for their assistanceand efforts for development of the X-ray monitor at CesrTA.	
•They also thank Prof. T. Mitsuhashi for cooperation to test
the X-ray monitor at ATF2.