Beam Diagnostics
7 Feb. 2011, the 16th KEKB Accelerator Review Committee	

M. Arinaga, J. Flanagan, H. Fukuma, S. Hiramatsu, T. Ieiri, H.
Ikeda, H. Ishii, K. Mori, M. Tejima and M. Tobiyama 	

1. Introduction	

2. Beam Position Monitor	

3. Bunch by Bunch Feedback System	

4. Synchrotron Light Monitor	

5. Gated Measurement	

6. Loss Monitor and DCCT	

7. Damping Ring	

8. Construction Plan	

9. Summary	1. Introduction	
Parameters of SuperKEKB related to beam diagnostics	
HER	

LER	

Energy (GeV)	

7.007	

4.000	

Current (A)	

2.6	

3.6	

BPM, FB, SRM	Number of bunches	

2500	

2500	

FB, SRM	

Single bunch current (mA)	

1.04	

1.44	

BPM, FB, SRM	Bunch separation (ns)	

4	

4	

BPM, FB, SRM	Bunch length (mm)	

5	

6	

FB, SRM	

Emittance (nm)	

4.3	

3.2	

BPM, FB, SRM	x-y Coupling (%)	

0.24	

0.27	

BPM, FB, SRM	Vertical beam size at IP (nm)	

56	

48	

BPM, FB	

Transverse damping time (ms)	

53	

43	

FB	

reuse of KEKB
chambers	

ante-chamber	

BPM, SRM	

Vacuum chamber	

Much smaller beam size and larger beam current thanthose at KEKB.	

Relatedmonitors	

BPM : Beam position monitor	

FB : Bunch feedback	

SRM : Synchrotron radiation monitor	

Main ring diagnostics	

System	Quantity	Comments	

LER	

HER	

Beam position monitor (BPM)	

452	

475	

Closed orbit correction, slow/fast orbit feedback,
iBump feedback, optics correction	

Displacement sensor	

100*	

100*	

Displacement between a sextupole and a BPM	Transverse bunch by bunch feedback	1	

1	

Suppress beam instabilities, kick a pilot bunch	Longitudinal bunch by bunch feedback	1	-	Suppress beam instabilities	

Visible light monitor	

1	1	Transverse/longitudinal bunch profile, transverse
beam size	

X-ray light monitor	

1	1	

Precise beam size	

Beamstrahlung monitor	

1	1	

Beam information at IP	

Gated measurement	

1	1	Tune, position and phase of each bunch	Tune monitor	

1	1	

Loss monitor	

300*	

300*	

300 PINs in each ring, additional 100 ion chambers
common to LER and HER	

DCCT	

1	

1	

Reuse of KEKB system with modification of a circuit	

Bunch current/fill pattern monitor	

1	

1	

Items marked by orange are new in SuperKEKB.	

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

* Tentative number	2. Beam Position Monitor	

2.1 Consideration on system design	

A. Tentative specification	•Precise slow measurement	
Optics measurement at low beam current, slow orbit feedback	

Resolution : ~ 2µm, repetition rate : ~0.25Hz	

•Orbit measurement for fast iBump feedback	

To Maintain stable beam collision	

Resolution : ~ 1µm, repetition rate : ~1kHz	

•Turn by turn orbit measurement	

Optics measurement during physics by kicking a pilot bunch	Resolution : 50 to 100µm	

•Orbit measurement for fast orbit stabilizing feedback	
To avoid vertical emittance growth	

Resolution : ~ 3µm, repetition rate : ~1kHz	B. Assumption for system consideration	
1) LER vacuum chambers are replaced by ante-chambers. 	

Narrowband detectors of KEKB can not be used because cutoff frequency of theante-chamber is below their detection frequency.	

2) Most HER vacuum chambers in KEKB are reused.	

The narrowband detectors of KEKB will be used.	

3) The number of turn by turn BPMs are three per betatron wave length.	

4) BPMs for fast orbit feedback are placed around IR region.	

The number of the BPMs is not large, e.g. about 30 per ring.	

This condition, which was presented at an optics meeting last September, led tothe change of design of BPM system.	

C. Other factors affecting system consideration	
1) Larger beam currents than those in KEKB	
Large signal power to a detector, poor electrical contact of an electrode and a cableand movement of BPM due to thermal deformation of a chamber.	

2) Maximal use of present narrowband detection system to save the cost.	

D. Plan of BPM system	
1) Introduction of new detectors	
•Narrowband detector for 509 MHz detection	
The detector is a 509MHz version of a KEKB detector. 	

One detector covers four BPMs by multiplexing signals.	

The VXI system in KEKB can be used.	

Cost reduction	

•Turn-by-turn detector with a fast gate 	
•Mediumband detector for orbit stabilizing feedback	•Special detector for iBump feedback	2) Use of new button electrode	
Button with small diameter, pin type inner conductor 	

3) Use of displacement sensors to measure the movement of BPM due tothermal deformation of a chamber.	
About 200 displacement sensors are already installed in KEKB to measure the movement of
BPMs from nearby sextupoles (resolution < 0.2µm, range 0.5 to 2.5mm). 	

Need to develop special sensors near rotatable sextupoles for local chromaticity
correction and at QC2s in cryostats.	

Full BPM system	

Type	Function	

Narrowbandof KEKB	

closed orbit
correction, maintainorbit against slow
drift, optics
measurement	

Resolution	(tentative)	

Repetition	(tentative)	

The number ofunits	

2µm 	0.25Hz	115 (already wehave.)	

New
as above	
narrowband	

2µm 	

0.25Hz	110	

Turn by turn	
 optics measurement
during collision	

50 - 100µm	
 100kHz	

270	

Mediumband	 fast orbit feedback	

3µm	

1kHz	

60	

IR	

1µm	

1kHz	

4 to 8	collision feedback	

A narrowband detector covers four BPMs.	

E. Construction plan of BPM system 	

1. Narrowband BPM system and BPM for iBump feedback	

These are minimum systems which are to be prepared at T = 0. 	

2. Mediumband BPM for fast orbit feedback 	

Need detail evaluation of location, quantity and specification. 	

Also need evaluation of minimum quantity at T = 0. 	

Candidates of a detector are a detector for iBump feedback withmodification or a commercial detector. 	

3. Turn by turn BPM for optics correction during physics 	

Need evaluation of minimum quantity at T = 0. 	

(Correction scheme at KEKB might be possible at SuperKEKB for single beam.)	

4. The narrowband could be gradually replaced with the mediumband and the turnby turn after T = 0. 	

1) Complete R&D of the narrowband and the BPM for iBump feedback. 	

2) Continue R&D of the mediumband and the turn by turn.	

3) Determine system at T = 0 by the middle of 2012 based on study of
beam optics, R&D results, strategy of commissioning and budget. 	

4) Start construction of the detector system.	

2.2 Status of R&D works	

A. Button electrode	•A button electrode has been developed.	
◊Diameter : 6mm	◊Flange type for easy replacement
upon trouble and TiN coating	◊Pin-type inner conductor for tightelectrical connection	
◊Ceramic vacuum seal	

Temperature rise ~3deg @ 1.6A	

•Prototypes were tested at KEKB. Problem is
not found.	
•The electrode is ready for mass production.	

If the HER chamber and the 12φ electrode at KEKB arereused, signal power at the electrode is increased thanthat expected for the 6φ electrode.	

Analytic estimate : Pelectrode = 2.2W @ 2.6A 	

for KEKB electrode 	

The calculation needs to be compared by the EM code. 	

Beam signal	

B. Narrowband 509 MHz super-heterodyne detector	
•A narrowband super heterodyne
receiver is being developed based on a
detector of KEKB. 	

•Detection frequency is changed from
1GHz at KEKB to 509MHz because
the cutoff frequency of a chambers is
below 1GHz.	

Specification	

Detection frequency	

508.887MHz	

SNR at signal power of -60
dBm	

> 89.8 dB	

Noise figure 	< 7 dB	ADC (bits/sampling freq.)	

18 bits / 102.4 kHz	Max. input power	

-50 dBm	

FFT points (by DSP :SHARC)	

2N (N=4, 5, ...., 12)	Switch	

Down converter	B.1 Status of R&D 	

PIN	

1) Switch	

Switch-noise appeared at the end of a switch section.	

The switch was redesigned at KEK by replacing FETs to
PINs and removing decoupling capacitors between switches. 	

Switch	Preliminary results (test bench, CW input)	

New switch!

PIN	Old switch!

No.1!

No.2!

Transmission loss!

1.485 dB!

1.485 dB!

2.1 dB!

Isolation!

99.6 dB!

99.7 dB!

86 dB!

Difference of input/
output reflection coeff.
between channels!

0.0077!

0.0157!

0.04!

Down converter connected with switch 	

New switch!

Old switch!

A new switch	

No.1!

No.2!

S/N!

-92.46 dB!

-93.05 dB!

-83 dB!

S/N (ratio of voltages of
two channels)!

-93.21 dB!

-94.1 dB!

-93 dB!

1
1
σX ≈ K= 0.37 µm
2 (S /N)Apparent shift of beam
position for different
attenuator settings!

9µm!

30µm!

60µm!

for S/N=93dB and K=33mm	

Different down converters were used.	

€1) Switch (continued)	

•The change of apparent beam position may be caused by impedancemismatch between a switch section and a variable attenuator after the switch.	

•A new attenuator will be tried next fiscal year if budget is available. 	

2) Linearity	

•The measurement of gain error as a function of input power at a company showed
the gain error of +/- 0.2 % in the input range of 30dB before improving the switch.	

Position error is very sensitive to the gain error.	

Position error	
Δx = (K /4)⋅ ε , ε = ΔV/V (Gain error of an electrode), V : signal level	

Δx = 1µm	

ε = 0.012%, gain difference 1+ ε= 0.001dB	

Need very precise adjustment of signal level between four channels.	

€•A calibration method of input power is being checked at the company. 	

•Linearity will be measured with the new switch. 	

(K=33mm)	

C. Turn by Turn detector	

1) Original plan 	•To develop a detector which houses a mediumband circuit and a turn by turn circuit.	

2) Recent plan 	•Recent discussion suggests the required number of the mediumband circuit and the turn byturn circuit much differ, i.e. 60 for the mediumband and 270 for the turn by turn. 	

•Now we are developing a turn by turn detector which has a gate to divide signals
between the pilot bunch and other bunches. 	

•Just a signal of the pilot bunch is "stolen"
for the turn-by-turn measurement. 	

•Signals of remaining bunches are sent to
output ports of the detector connected toa narrowband or a mediumband detector. 	

•The mediumband detector needs no
special gates. (A commercial detector
can be a candidate of the detector. )	

•Simultaneous measurement by two
circuits is possible.	

•A bunch signal is detected by a log amp to savethe cost of the turn by turn detector. 	

Block diagram of a turn by turn detector	

Mediumband or
narrowband detector	

fast switch	

splitter	combiner	

log amp	

From BPM	

FPGA	

A prototype circuit will be tested in this spring.	

A glitch cancel circuit by T. Naito	D. BPM for iBump orbit feedback 	

D.1 Requirement (Y. Funakoshi's talk)	

1) Vertical positions of both beams are monitored for orbit feedback( "iBump
feedback") to maintain stable beam collision. For horizontal feedback, BPMs are
not used.	

2) Location of BPM	QC1RP, QC1LP, QC1RE, QC1RP	

3) Resolution	

1 µm (tentative)	

4) Repetition	

1kHz (tentative)	

e+	

QC2	

QC2	

QC1	

QC1	

BPM	

QC2	

BPM	

QC1	

IP	
BPM	

BPM	

QC1	

QC2	

e-	

D.2 Button electrode for IR BPM	•Reduce signal level at a feed through	

Small button size of φ1.8	

Estimated beam power	

Total power：about 10.4W	

508MHz component：about 6dBm	

•Fixing of a central conductor to a body of the
feedthrough is relatively weak, i.e. 1/10 ofOctopos. Improvement may be needed.	

D.3 Detector	

•Down-covert 508.8MHz component to intermediate frequency(IF) of 16.9 MHz with an analog mixer.	

•Convert IF to digital signal by a 16 bit ADC.	

•Detect position through digital filters (two CICs and a FIR).	

SNR is relatively insensitive to a clock jitter compared to directconversion though additional analogue RF circuit is needed.	

•A prototype module is being tested.	

•Digital processing uses a processor for LLRF system developed by
RF group. 	

Top view	

Specification	

Input level	

-10 ~ -3 dBm	

Detection frequency	

509MHz	LO frequency	

492 MHz	IF frequency	

16.9 MHz	ADC resolution 	

16 bits	

ADC sampling
frequency	

99.4 MHz	Sampling clock jitter(target value)	

<1ps	

CIC1	

5 stage, decimation 32	

CIC2	

5 stage, decimation 96	

FIR	

201 tap, decimation 7	

Noise figure	<20dB	

SNR	> 110dB@-2.65dBm
sinusoidal wave	

Control	

EPICS	

Performance of a prototype	a) Analogue section	

Clock jitter 1.30 ps (1 Hz < f < 20 MHz)	

Noise Figure 14.3dB @ 16.9MHz	

(Noise Figure =Si /N i)So /N oTemperature coefficient of IF out -0.03dB/deg.	

Analogue part works well.	

€Clock jitter < 2.3ps	

Phase noise of clock	

Temperature stability of clock jitter	b) Digital section	

Frequency characteristics of the digital filter	

Spectrum at the end of the digital filter	

Input : CW in front of ADC.	

Input level -1dBFS, input frequency 17MHz-10Hz(intentionally shift by 10Hz from IF freq.).	

Design	output level (dB)	

FFT of 4096 points	

Amplitude (dB)	

?	

124dB	

Measurement	frequency (Hz)	

SNR 100dB	

Frequency (Hz)	

Overall attenuation-characteristics was
confirmed by the measurement. 	

σy ≈ 40nm
for chamber radius of 10mm.	

Performance of the filter connected analogue section
with digital €section will be measured by the
beginning of March. 	

c) Latency	

CIC	

N⎛ 1 − z −RM ⎞ N ⎡RM −1 −k ⎤Transfer function	

 H(z) = ⎜
−1 ⎟ = ⎢ ∑ z ⎥
1
−
z
⎝
⎠
⎣ k =0 ⎦Order of right hand side	−(RM −1)N ≈ −RMN

Delay after decimation(RM/R)N=NM samples	€
1st stage : R=32, N=5, M=1 	
€2nd stage : R=96, N=5, M=1	R : decimation factor,	M : differential delay offor RM>>1	
comb filter	N : stage of CIC	delay : 5 samples = 1/(98.398M/32)x5=1.6 microsec	
delay : 5 samples = 1/(98.398M/32/96)x5=0.16 msec	

FIR (Kaiser window)	
N tap
1
200
group delay ≈⋅=⋅= 3.1ms
f clock 2
32kHz 2
1

fclock : clock rate of the filter, Ntap : the number of taps	
€CICs and FIR 3.26ms	

MATLAB calculation 3.27ms	

consistent one another	Measurement 3.26ms	

Latency will be reduced by decreasing decimation rate of the CICs, if necessary.	

E. Prototype of a detector for the damping ring	•A prototype VME module was produced.	

•Log ratio(L/R) method is used.	

◊Cheap	◊Relatively simple circuit	◊Large dynamic range and wide linear range	

◊Reasonable resolution and precision	

◊Applicable to optics and tune measurementwith single bunch	•Specification	

◊4ch 508MHz L/R detection (Filter : 506MHz,
BW24MHz)	

◊Sampling clock : 1 to several MHz	

◊Input level : -70 to 0 dBm	◊Memory length : 32k, 64k, 128k, 256k word	Performance	Linearity	◊Linearity of four channels is adjusted well. 	

◊SNR is 70dB. 	

◊Position resolution is about 18µm in x and y directions. 	

The module can be a prototype of a turn by turn detector in the main rings. 	

3. Bunch by Bunch Feedback System	
3.1 Transverse feedback system	
A. Requirements	
Growth time of Coupled bunch instability	

1) RF cavity	

2) Resistive wall 	

LER	

HER	

ARES (HOM)	

7 ms	

39 ms	

Super (HOM)	

---	

14 ms	LER (Cu)	

LER (Al)	

HER (Cu)	

3.6 ms	

2.8 ms	

3.1 ms	(Transverse radiation damping time : LER 43 ms, HER 53 ms)	3) Electron cloud instability (ECI) in LER	

0.5ms at the average/central electron density of 5 1010/1.1 1011 m-3 in drift space
without solenoid field (Y. Susaki at LER2010). The growth time will be increased ifsolenoids reduce the electron density. 	

4) Fast ion instability (FII) in HER	Simulated growth time 0.3 ms 	 (given at KEKB review 2010) 	

•Required feedback damping time 	LER : < 0.5 to 1ms, HER : < 0.3 ms 	

•Noise in transverse feedback system should be minimized to reduce the blowup of
the beam size during collision.	

B. System	

1) BPM with good time and frequency 5) Kicker 	

response.	

Two sets of a short stripline kicker per
ring which cover two feedback loops with
2) Low noise front-end electronics	

90 deg phase difference.	

3)Digital filter iGp	
Rsh=10kΩ per kicker, 500W
amp, 2 kickers 	4)Power amp	Vkicker=8.94 kV 	A( µm) /(τ damp /Trev ) = 6.4( µm)[HER], 11.2[LER]

Eight amps of 250 and 500 W perring.	

Damping time τdamp 0.31ms (HER), 0.18ms (LER) for
oscillation amplitude A of 0.2mm.	

€B.1 Monitor chamber	

•The present chamber will be replaced with a chamber of 50 mm φ. 	

Its higher cutoff frequency of 3.5 GHz is favorable for better detection for
precise position measurement.	

. 	

•The chamber will be equipped with twenty-four φ6 electrodes with a glass feedthrough.	

Present feedthrough	

Glass feedthrough 	Sharper signal	

Development has almost completed.	

B.2 New bunch detector	

•Comb filter at 2GHz or 3 GHz	To cut low frequency noise	To improve isolation between bunches	•Low Noise Amp with high IP3	•Bessel low pass filter	•DC amp	To improve transient response	

Test circuit	

The system will be built after decision of detection frequency.	

B.3 Digital filter	

•The iGp processor is a baseline system.	

•Developed under US-Japan collaboration (KEKSLAC).	

1.5GSPS 8 bit ADC, 600MSPS 12 bit DAC 	FPGA Vertex II	

•iGp was tested successfully for the transverse andlongitudinal system at KEKB and routinely used inlongitudinal feedback at KEK-PF.	

•iGp is ready for use.	
•Upgrade to 12 bits system is being discussed.	

◊Larger dynamic range 	
Large margin for offset	

◊Higher resolution 	◊Powerful FPGA (Vertex5)	

◊Large memory size 	B.4 Transverse kicker	
•Two sets of a short stripline kicker per ring	•Similar design with a present kicker	

•Planned improvement	

◊Change the feed through from 20D type to EIA-7/8 with low loss ceramics.	
◊Change high-power cables from 10D to 20D 	
◊The new feedthrough is under development.	

•A prototype of a kicker will be designed and made in next fiscal year if budget
is available.	

EIA-7/8 Feedthrough (bend type)	

The measurement of S parameters shows the feedthrough can be used for thetransverse feedback. 	

3.2 Longitudinal feedback system	
A. Requirement for the feedback damping time	
CBI growth time by cavity impedance	

LER	

HER	

ARES (HOM)	

12 ms	

59 ms	

ARES (0-π mode)	

20 ms	---	---	58 ms	

Super (HOM)	

(Longitudinal radiation damping time : LER 21 ms, HER 26 ms)	LER needs a feedback system with a damping time of about 10 ms.	

B. System	

2) Power amp	1) BPM, frontend electronics and digital filter	

Same as those of transverse system	
Four 500 W amps per kicker	
3) Kicker	
Two DAFNE type kickers with Q value of about 5	

Rsh=650Ω/kicker, amp. 500W x 4 / kicker, two kickers	

Vkicker=3.2kV 	

(ΔE / E) /(τ damp /Trev ) = 0.4 × 10 −6 [LER]

Damping time τdamp 10ms (LER) for oscillation amplitude ΔE/E of 4x10-4 .	

Space is reserved for additional two kickers.	

€A prototype of a kicker will be designed and made in next fiscal year if budget is available.	

4) Power cable, feedthrough and filter	

New power cables and connectors have been tested.	

An absorptive filter to reduce out-of-band power from the kicker will
be evaluated in this year.	

4. Synchrotron Light Monitor	
4.1 Visible light monitor	

A. Extraction Mirror	

•Heat load at high beam current causes mirror distortion.	

•A magnet of light source in LER will be a reused KEKB bend. 	

•Power on the extraction mirror in HER is slightly larger than that in KEKB.	

In order to reduce thermal deformation of the mirror further, we are developing a
new mirror made of diamond.	

Diamond mirror	

Single crystal diamond	•Au on surface	

•Good flatness of surface (< λ/50) is expected
because a plane of diamond surface coincides
with that of crystal. 	

•Good thermal conductivity reduces change ofapparent current-dependent beam size by 85%
compared with that of a present Be mirror. 	

Temperature distribution of adiamond mirror due to 200W
of SR power.	

diamond	Be	

Surface distortion of adiamond mirror due to 200W
of SR power.	

Calculated mirror surface distortion due to SR power of 200W
at the center of the mirror (Be and Diamond).	

ANSYS simulations	B. 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.	

•Vertical beam size measurement is possible with interferometers, though is near
the limit of the interferometer resolution.	

•Measurement wavelength needs to be lowered to fit beam size into dynamic range.	

	Also need to be able to measure 99% visibility (very difficult).	

•Limitation on slit separation is due to ante-chamber height (14 mm).	

Extraction mirror will be in ante-chamber for reduced impedance.	

Interferometers are used for measuring mainly horizontal beam size. 	

Vertical beam size is measured by a newly developed X-ray monitor. 	

4.2 X-ray Beam Size Monitors	

A. Coded Aperture Imaging	•Technique developed by x-ray astronomers using a mask tomodulate incoming light. Resulting image must be
deconvolved through mask response (including diffraction
and spectral width) to reconstruct object. 	

•Open aperture of 50% gives high flux throughput forbunch-by-bunch measurements. Heat-sensitive andflux-limiting monochromator not needed.	

Uniformly Redundant Array (URA)
for X-ray imaging to be used at
SuperKEKB. Pseudo-random patterngives relatively flat spatial frequency
response.	

•We need such a wide aperture, wide spectrum
technique for shot-by-shot (single bunch, single turn)measurements.	

Source distribution:	⎡⎤
K 2 / 3 (η)⎡ Aσ ⎤
3 ω
2
⎢
⎥
iX
γ
(1+ X )(−i)⎢ ⎥ =
K
(
η
)
⎢
⎥
A
1/ 3
⎣ π ⎦ 2π ω c⎣ 1+ X 2
⎦1ω
X = γψ, η =(1+ X 2 ) 3 / 2
2 ωc

Kirchhoff integral€ over mask	(+ detector response)	

€i⋅ Aσ ,π (source)t(y m ) i 2λπ (r1 +r2 ) cosθ1 + cos θ 2
e
(
)dy m
Detected pattern:	
Aσ ,π (y d ) =∫λ2Mask r1r2€

Simulated detector response forvarious beam sizes at SuperKEKB
LER.	

Coded Aperture tests at CesrTA	

Example of turn-by-turn size andposition data (one bunch out of train)	

Example of bunch-by-bunch data (electroncloud blow-up study data)	

Single-shot data average for each bunch	

Expect to be able to make similar
measurements at SuperKEKB	Bunch-bybunch position
spectra	

V. tune	Expected single-shot resolution	

Resolution of beam size	

(SuperKEKB full current）	

Beam to mask: 12 m	

Mask to detector: 36 m	

Red：assuming the same type of a detector
as that used in CesrTA	

Green：assuming an under-developed detector	

HER: 10 µm pitch coded aperture	Beam to mask: 8 m	Mask to detector: 32 m	

Resolution is calculated from statistical fluctuationof the number of detected photons in single-bunchand single turn. 	

LER: 10 µm pitch coded aperture	

URA Mask and window	
•Tests at CesrTA show URA mask gives better resolution thanFresnel zone plate or pinhole (as expected).	

•High-power mask needs to be tested.	

Thick Si mask installed at CesrTA for high-power testing.	

CesrTA at 5.3 GeV can duplicate power load expected at SuperKEKB. 	

Diamond substrate mask also under consideration.	

•Also may need a diamond window to separate detector box vacuum
and ring vacuum.	

Microscope's view of URA mask	

X-ray detectors and readout	• Fermionics InGaAs sensor array in use at CesrTA, also begun testing at ATF2.	

•Have also done some tests at KEK PF.	

• Determined that Fermionics detector efficiency too low at high x-ray
energies (such as will be seen at SuperKEKB).	

Need new detector. Studying new detector technologies:	

• Geiger-mode array of small photon-counting elements(various companies and labs).	

• 3D (deep but thin) silicon detector (SLAC/UH)(calorimeter style detector).	

•Compact-PCI based DAQ being developed.	

Signal flow diagram for x-ray monitor system	

Fermionics InGaAs detector array.	

Also being used at CesrTA (with Cornelldeveloped mount and readout).	

Illustration of two of the detector concepts to be
explored in next phase of x-ray detector
development. At left, a regular pattern of n and pelectrodes, at right, a trench structure, which
provides a more uniform drift volume.	

"Flanagan" in Japanese	

STURM2
Digitizer	

STURM ASIC for high-speed
readout (G. Varner).	

Ver. 1 tested at KEK PF,
March 2009.	

Ver. 2 fabricated. 	

Ver. 2 specs:	

Hawaii islands	

Testing at ATF2 for use at SuperKEKB	

4.3 Beamstrahlung Monitor	

•Developed by G. Bonvicini (Belle, Wayne State U.) originally for use at CESR.	

•Detection of the radiation of the particles of one beam due to the bending forceof the EM field of the other beam.	

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

A. Design of the SuperKEKB detector	

•Better signal to noise ratio due to strong beams at SuperKEKB. 	

•View port location at ±90 degrees minimizes backgrounds,
polarization measurement errors, and provides redundancy
against beam orbit errors.	

mirror and view port	

•To be located anywhere between 5 and 10 mrad fromthe beam direction at the IP.	

•Suggested mirror and window sizes:
2.83 X 2mm2 and 2.1 X 2.1 mm2.	

•Light is transported to optics boxes by means ofsimple black-anodized pipes and mirrors.	

•Device consists of achromatic telescope with pinhole
optics, polarization splitter, and two gratings
illuminating 4 PMT with filters.	

G. Bonvicini	transport line of light	5. Gated Measurement for Bunch-Tune, -Orbit and -Phase	

5.1 Development of a fast gate module	•A fast gate module has developed for a fast gate tomeasure the tune, orbit and longitudinal phase of eachbunch separated by 2ns.	

5.2 Fast and high resolution measurement of gated tune	

gated signal	An exciter of betatron oscillation was successfully
tested at KEKB. 	

The system is used in SuperKEKB to kick the pilot
bunch for the optics measurement and the tune
measurement.	

Measuring locked signal of a PLL loop
which tracks the tune enables precise
measurement of betatron frequency byreciprocal method.	

1 ns/div	

Gate Pulse
for Pilot
bunch
Pulse
Modulator

Counter	Frequency resolution is 10-6 for measurement
time of 2ms if error source is only counting
error. 	

fβ

feedback loop
Deflector

Variable
ATT

Pilot
bunch

10 - 50 kHz

PLL

phase control

TunableBPF

Bunch
Oscillation
Detector

bunch
train

Gate 1

PLL exciter	

FujiB4

6. Loss Monitor and DCCT	

6.1 Loss monitor	

•Sensors are ion chambers and pin diodes.	

•Electronics of KEKB are reused as much as possible.	

•The system parameters such as quantity, location,
density and so on, is decided after evaluation of beamloss by the commissioning group by this summer. 	

PIN diode	

6.2 DCCT	•Electronics of LER-DCCT will be modified to fit
the increased beam current of 3.6A. 	

•HER-DCCT can be reused without modification.	

LER	

DCCT	

7. Damping Ring	

Damping ring diagnostics	

System	Quantity	Comments	

BPM	

84	

Log Ratio detector	

Synchrotron light monitor	

1	

Streak camera, gated camera	

Transverse bunch by bunch feedback	

1	

Tune measurement isincorporated.	

DCCT	

1	

Reuse of DCCT at KEKB	

Beam loss monitor	

36 in the ring,
17 in BT	

Ion chamber and/or PIN	

Bunch current monitor	

1	7.1 BPM system	

•Recent calculation of CSR is affecting to the design of a vacuum chamber. 	

•Re-design of a BPM button and a feedthrough might be necessary.	

•A prototype of a log ratio detector has been developed as described. It will
be used in the damping ring with minor changes of a circuit to fit the gain
to the input level. 	

7.2 Transverse feedback system	

•Detector : 2GHz detection, same as that of the main ring. 	

•Digital filter : iGp with firmware matched with the damping ring.	

•Power amp : Use spares of KEKB, 250W x 4. 	

Chamber-center to electrode：16.8mm	

Characteristic impedance : 50 Ohm	Electrode : 2mm thick, SUS+Cu plating	

Kicker	7.3 Synchrotron radiation monitor (SRM)	

Layout	

Instruments	

source position	

Streak camera : longitudinal profile	

Gated camera : transverse profile	

Related parameters to SRM	unit	

Injection	Extraction	

Final	

Beam size σx	

2060	

385	

381	

μm	

Beam size σy	

3950	

121	

75	

μm	

Point Spread
Function	

25	

25	

25	

μm	

Smeared σx	

2063	

385	

382	

μm	

Smeared σy	

3948	

121	

77	

μm	

monitor room	Total length of light path : 10m	Resolution of the measurement is OK.	

8. Construction plan	

BPM"

Main Ring	

FY2011"

2012"

2013"

2014"

electrode"detector"
displacement
sensor"

NB,TBT,MD,IR	

NB,TBT,MD,IR"
QC2,local corr. SX"Orange :fabrication, instal-	

lation	

kicker"amp&filter"

filter"amp."

filter"FT&cable"
low level"SRmonitor"

Misc."

low noise frontend"
detector"

visible light beam line" reinforce floor under huts"transfer line"

extraction mirror"
X-ray beam line"

mask, window"

X-ray detector"

readout,sensor"

beamstrahlung mon."loss monitor"
DCCT"bunch current mon."gated meas."

more MD, TBT"Green : R&D 	

signal cable"

Bunchfeedback"

2015"

transfer line"

ext. mirror"
sensor"modification of circuit"

PLL excitor"Damping Ring	

FY2011"
BPM"

2012"

2013"

Green : R&D 	

Orange :fabrication, instal-	

lation	signal cable"

kicker"amp&filter"

filter"FT&cable"
low level"SRmonitor"visible light beam line"

FPGA firmware"chamber of ext. mirror"

iGp, detector"

transfer line"

extraction mirror"

Misc."

2015"

electrode"detector"

Bunch
feedback"

2014"

loss monitor"
DCCT"tune monitor"

sensor, readout"

9. Summary	

9.1 Beam position monitor	
A. Button electrode	•φ6 electrode has been developed and tested with beam. Mass production for
LER will start next fiscal year.	

B. Narrowband detector for slow orbit measurement	•A prototype shows resolution is OK. Now trying to reduce the change of offset.
Linearity may need to be improved.	

C. BPM for collision feedback	•A button electrode is under development.	
•A prototype of a detector has been made. Performance of analogue section is as
expected. Overall performance will be tested by this March.	

D. Turn by turn detector	

•A prototype log-ratio circuit including a fast switch will be tested in this year. 	

E. Mediumband detector for fast orbit feedback	•System requirements such as quantity, installed location, function, resolution etc.
should be fixed. A system design for fast orbit feedback including correction algorism,
magnet-control and network configuration should be started soon.	

F. Displacement sensor	

•The sensors in cryostats and at sextupoles for local chromaticity correction mightneed R & D. 	

9.2 Bunch by bunch feedback system	
A. Transverse feedback system	
•Two stripline kickers for each ring will be used.	

•Kickers with minor improvements of a KEKB kicker will be used inearly stage of operation. 	

B. Longitudinal feedback system	
•Two DAFNE type kickers will be used in LER.	

•New power cables and connectors have been tested.	

•An absorptive filter will be evaluated in this year.	

C. Common components for transverse and longitudinal system 	
•The iGp digital filter is ready for use.	
•Low noise frontend is being developed.	
•High power feedthroughs are successfully tested.	

9.3 Synchrotron light monitor	

A. Visible light monitor	
•Reuse present source bend locations.	

•σz measurement by the streak camera is OK, σx by the interferometer is OK. 	

σy measurement by the interferometer will be difficult to get required resolution.	

•Floors under huts will be reinforced to reduce vibrations.	

B. X-ray monitor	
•Source bends upstream of source bends for the visible light monitors.	

•σy measurement by the coded aperture mask (CAM) is OK.	

Single-shot (single-bunch, single turn) resolution is expected to be sufficient.	

•σx measurement by CAM is possible, if single-shot measurements are needed.	

•The system will start with vertical measurement.	

•Being developed in collaboration with Cornell U. and U. Hawaii.	

Testing at different components at CesrTA and ATF2.	

C. Beamstrahlung monitor	

•The system requires extraction windows and extraction mirrors.	

•Location of the mirrors and the windows are not decided yet.	

•R&D of an extraction mirror made of diamond will be tried in this or next year.	

•Components are being tested by a group of Prof. G. Bonvicini.