The Eighth KEKB Accelerator Review Committee Report
Introduction
The Eighth KEKB Accelerator Review Committee meeting was held on February 10-12, 2003.
The Committee welcomed one new member: Warren Funk from JLab. One member of theCommittee retired this year: Wolfgang Schnell from CERN. The Committee expressed its
appreciation for his efforts during all the previous Reviews, leading the evaluation of the RF
Systems for the Committee. Appendix A shows the present membership of the Committee.
The eighth Committee meeting followed the usual format of oral presentations by the KEKB
staff members and discussion by the Committee members. The Agenda for the meeting isshown in Appendix B. The younger members of the Group made many of the presentations
this year. The Committee was nevertheless impressed by the high standard of the talks, bothtechnically and the presentations themselves. The recommendations of the Committee were
presented to the KEKB staff members before the close of the meeting. The Committee wrote
a draft report during the meeting that was then improved and finalized by e-mail among theCommittee members.
Contents
A) Executive Summary
1) Forward2) Summary3) Comments
B) Findings and Recommendations
1) Overview of KEKB
2) Belle Status
3) Machine Performance since February 02
4) IP Vacuum5) Beryllium Chamber
6) Movable masks, HOM, etc.
7) RF System
8) ARES9) Superconducting Cavities
10) LER Blowup and HER transverse coupled bunch instability11) Simulation study of electron cloud12) Instability measured by streak camera
13) Transverse coupled bunch instability by electron cloud in LER
14) Fast beam loss monitor
15) Tune, bunch length, bunch-bunch position
16) Bunch by bunch feedback17) IR BPM
18) Progress in Linac: 2-bunch injection etc.
19) Beam size measurements at Linac
20) Magnet issues, circumference drift21) Progress in control system
22) “iBump” feedback tuning23) Facilities and operation
24) Beam-beam simulation and experiment25) Further luminosity upgrade
Page 1 of 2226) SVD227) Luminosity boost by head-on (crab) collision28) Crab Cavity R&D
29) Lattice design for Crab Cavity30) IR Design for SuperKEKB31) Dynamic aperture of SuperKEKB32) Impedance estimation
33) Vacuum chamber R&D
34) C-Band R&D
A) Executive Summary
1) Foreword
KEKB has made excellent progress in the year since the last Committee meeting. The peakluminosity has increased to a new world record of 8.26 x 1033 cm-2s-1 (at this time last year it
was 6.65 x 1033 cm-2s-1, the year before 2.5 x 1033 cm-2s-1). The BELLE detector has
accumulated 107.4 fb-1, another world record (56 fb-1 last year and 13 fb-1 the year before) andpublished 55 papers in refereed journals (23 the year before). KEKB also holds the world
records for most integrated luminosity in a shift, in a day, and in a month. In the two-day
meeting, most of the talks dealt with present status of KEKB showing the attention to detailthat has made KEKB such a success. The remainder covered the plans for upgrading KEKB
to a luminosity of 1035 – 1036 cm-2 s-1. The KEKB machine group had done an enormous
amount of work, and is to be congratulated on the impressive results that have been achieved.
2) Summary
KEKB has made spectacular progress over the last year, breaking all of the worldwide
luminosity records: highest peak luminosity: 8.26 x 1033 cm-2s-1, highest daily integrated
luminosity: 434 pb-1, highest 7-day integrated luminosity: 2.58 fb-1, and highest 30-day
luminosity: 8.78 fb-1 (PEP-II still holds the record for highest stored beam current). All ofthese records were set last October, just before a failure of the interaction region vacuum
chamber that stopped the operation for two months. After installing a replacement chamber,the BELLE detector group requested that the beam current not be increased until ananomalous temperature rise in the IP vacuum chamber has been understood, so there havebeen no further records. The KEKB team has made many hardware and tuning improvements
in order to reach this performance and they are to be congratulated on the excellent results.
The BELLE detector has now accumulated 107.4 fb-1, compared with 104 fb-1 logged by
BaBar. The BELLE detector is working extremely well and has had no major difficulties.
Backgrounds are low, and losses during beam injection are generally small; this will makecontinuous injection acceptable to the detector when some triggering problems have beensolved. Overall, the BELLE collaboration is extremely pleased with the quality and quantityof the beam being provided by the accelerator. Their only request (as usual) is for moreluminosity!

Page 2 of 22

3) Comments
The Committee has made recommendations throughout the different sections below.
They are collected here for convenience.
1. The Committee believes that improving the luminosity of KEKB is the highest priority,and experimental and theoretical studies to improve luminosity should be given
precedence. These studies should also include the design of a major luminosity
upgrade (SuperKEKB) aimed at a luminosity of 1035 – 1036 cm-2s-1. The Committee
endorses the direction of the present studies and recommends that they be continued.
2. The Committee recommends that high priority be given to understanding the cause of
the anomalous temperature rise in the IR vacuum chamber, which is presently limiting
the total circulating beam current.
3. The Committee strongly endorses the proposal to install a crab cavity in one ring assoon as possible, and recommends that a second cavity be installed in the other ring assoon as funds permit. In the meantime, detailed theoretical studies of the beam
dynamics of the ring with a single crab cavity should continue.
4. The Committee strongly encourages machine studies to develop continuous positron
injection, as this is the best way to increase the integrated luminosity when the beam
current is limited.
5. The Committee also encourages machine studies of 3-bucket spacing, as this is thebest way of increasing the luminosity if there are no beam current limitations.
6. The Committee recommends that studies that lead to high-current, short bunches
should be pursued, including a negative dispersion lattice.
7. The Committee supports continued simulation studies of the transverse wake from thetrapped cloud to assess its effect on the coupled-bunch instability.
8. The Committee encourages further efforts to find a configuration for electrostatic
clearing electrodes that can effectively clear the electron cloud in the magnet vacuum
chambers.
9. The Committee recommends that the experimental and simulation studies of theTransverse Coupled Bunch Instability (TCBI) should continue
10. The Committee recommends continued participation in the collaboration with SLAC
to develop a new digital signal processing system for the multi-bunch feedback system.
11. The Committee suggests that the turn-by-turn and bunch-by-bunch data from the
BPMs might be used as a tool to tune up the luminosity.

Page 3 of 22

B) Findings and Recommendations
1) KEKB overview
KEKB has made excellent progress in the year since the last Committee meeting. The peakluminosity has increased to a new world record of 8.26 x 1033 cm-2s-1 (at this time last year it
was 6.65 x 1033 cm-2s-1, the year before 2.5 x 1033 cm-2s-1). The BELLE detector has
accumulated a total of 107.4 fb-1, another world record (56 fb-1 last year and 13 fb-1 the year
before). This means that the accelerator has provided more than 50 fb-1 last year – animpressive result. In the period up through June 2002, the accelerator current was limited byheating of the masks and other components. These were changed out in the summer
shutdown and the luminosity increased steadily through October when all of the luminosity
records were set. In October, a failure of the interaction region vacuum chamber stopped theoperation for two months. The problem with the beryllium chamber was apparently due tocorrosion but it is still being evaluated (see Section 5 below). During the shutdown, moresolenoids were added to the LER so that there is now no blow-up of single beam currents up
to 1.6A and the threshold is now estimated to be 1.8A. High current operations are still a big
issue, despite a lot of improvements. The hardware issues are with the movable masks andheating of other components. The physics issues are the control of instabilities and improving
the feedback systems. It can be expected that both of these areas will continue to be thelimiting factors as the beam current increases.
The long-term future of KEKB is an upgrade to 1035 – 1036 cm-2s-1. The studies that are being
carried out on the present machine will not only serve to increase the luminosity in the shortterm but will serve as the basis of the upgrade. The Committee strongly supports thesestudies and endorses the direction taken.
Simulations indicate that an extremely high tune shift can be obtained if the collisions arehead-on using a crab crossing and with a horizontal tune close to the half integer. This makes
development of the crab cavities a high priority, with first tests foreseen in 2005. If
successful, this way of operating would provide a luminosity boost in 2006 with the present
beam current capability. It would also provide the basis for the upgrade.
2) BELLE Status
The BELLE detector has now accumulated 107.4 fb-1, compared with 104 fb-1 logged by
BaBar and has recorded >100 million B-meson decays and reached a sensitivity down to 10-8
branching ratio. One of the principal Physics goals of the detector is to find evidence for CP
violations in B-meson decays and to measure the CKM parameters precisely. The
measurements of sinφ1 at BELLE are a major contributor to the present world average. This
year, by studying the decay of B mesons to two π mesons, the first estimate of sinφ2 was made.
These are extremely important results which KEKB and BELLE were designed to obtain.
These results have been presented in a total of 55 papers that have been published in refereed
journals.
The BELLE detector is working extremely well and has had no major difficulties. The
replacement beryllium vacuum chamber exhibits some anomalous heating at one end. Until
the cause of this heating is understood, the detector physicists prefer not to push the beam
currents higher. Even though the chamber will be replaced this summer as part of the SVD2
Page 4 of 22

upgrade (see Section 26 below), they want to cautiously take data as long as possible with thepresent chamber. Understanding this problem should be given high priority as it restricts themachine development studies that will enable BELLE to make full use of the SVD2 detector.
Backgrounds are low, and losses during beam injection are generally small; this will makecontinuous injection acceptable to the detector when some triggering problems have beensolved. Because of the present beam current limitation from the beryllium chamber, theability to operate with continuous injection is extremely important.
3) Machine Performance since February 02
The improvement of KEKB over the past year has been very impressive. The luminosity has
increased by 25% to 8.26E33 cm-2s-1 that is now over 80% of the design value and remains
the world’s record. The integrated luminosity per month has increased by 15% to 8.78 fb-1 permonth that is very near the target goal set last year of 9 fb-1 per month. These performanceincreases are a testament to the dedicated teams of KEKB and the KEK Linac who havebrought this accelerator to the forefront of particle physics. There have been many accelerator
improvements over the past year resulting in these luminosity gains.
The Low Energy Ring LER has had several upgrades, including completing the complementof RF stations with 20 ARES cavities. The beam current has reached 1.8 amperes. Moresolenoid and permanent magnets covering about 50 m were wound or mounted over thevacuum system to successfully suppress further the Electron Cloud Instability (ECI). The totalsolenoid and PM magnet coverage is now 2275 m. With bunches every 4 RF buckets there isno blow-up of the positron vertical beam size up to a beam current of 1.6 amperes. Morestudies with bunch spacing of 2 and 3 buckets are suggested.
The High Energy Ring HER has now stored just over 1.0 ampere. This is a great achievement
as this is the first time that a 1 ampere current has ever been stored in superconducting RF
cavities. The HER will complete its full complement of RF stations with the addition of two
ARES stations this coming summer. With this complete RF complement, the design currentof 1.1 amperes will very likely be achieved.
The tuning of the interaction region has become very sophisticated with the use of iBumps,
tune corrections with current, dispersion and coupling knobs, circumference corrections, andtests of continuous injection. This collection of tools has brought the luminosity performanceof KEKB to it present record level.
The injection rate of positrons has now been doubled by the injection of two bunches per linac
pulse. This strong achievement is the culmination of considerable work by the Linac Groupover the past several years.
One disturbing event is the recent development of a vacuum leak in the IR beryllium vacuum
chamber. This chamber has recently been replaced with an older spare unit. This replacement
chamber is now limiting the peak performance of the KEKB collider. The cause of thevacuum leak(s) in the beryllium chamber is not known but is under active investigation. The
committee suggests that the cause of the leak be found as quickly as possible so that the newberyllium chamber that is to be installed this summer can be thoroughly checked for any
possible compromises.
Page 5 of 22

4) IP Vacuum
An abnormal pressure rise was observed in the IR section. The structure of IR beam chamberis coaxial, and the inner tube is made of beryllium of 0.5mm thickness. The pressure
increased by about two orders higher than observed in usual operation. Leak testing using ahelium gas spray was tried, but the vacuum group staff could not find any leak from outsideof the IR beam chamber. They observed the partial pressure of helium, and it gradually
increased. They understood that the leak had occurred not at the outside of the IR beamchamber but at the inside coaxial tube. They replaced the cooling gas from helium to argon,
and then nitrogen, and observed the appropriate partial pressure, and, in both cases, found anincrease in the partial pressure of the gas used for cooling. This was evidence that the leakoccurred from the beryllium pipe. The leak detection processes were carried out correctly
following the proper procedure. In the process, an increase of the hydrogen partial pressure
was observed, but the origin was not clear because the surface pumps that are used (NEG andion pumps) may have outgassed when they were switched off in the leak hunting process.
5) Beryllium Chamber
The IR beam chamber has a coaxial structure with a narrow passage between the inner andouter tube, through which helium gas flows to provide cooling. The vacuum side of the inner
beryllium tube was gold-plated to protect the tube from radiation damage. After the leak was
clearly demonstrated to be in the beryllium pipe, the staff disconnected the outer tube andfound that the outer surface of the inner tube was discolored. There were no cracks, either inthe beryllium tube itself or at the joints between materials. This indicates that a chemical
reaction occurred on the beryllium surface with water vapor contamination in the helium gas.
A bubble test was applied and bubbles were seen in the liquid indicating that the leak islimited to a very small hole or channel. These suggest that chemical reaction may not be thecause of the leak, but rather that grain boundary oxidation of the beryllium is more likely tobe the source of the leak. Further checking the dark spots on the gold plated surface may help
in understanding what happened.
In this coming summer shutdown a new IR beam chamber will be installed. The Committee
recommends that the beryllium material itself be checked and inspected and that a detailed
depth profile of the chemical components be obtained using SEM, AES and other inspection
techniques. These inspections should be completed before installation of the new IR beamchamber in the summer,. As a countermeasure to the oxidation of beryllium tube, additionalsurface protection is recommended on the outer surface of the inner tube.
6) Movable Masks
Peoples have continued to improve the movable masks from Versions 1 to 4, but, even so,
Higher Order Mode (HOM) (TE- modes) were excited at the mask head and penetrated into
the vacuum chamber with beam currents over 900mA stored in the HER. Simulation
indicates that the ramp length of the mask should be increased from 30mm to 400mm to
reduce HOMs. A new long movable mask was installed in the ring and was tested
successfully.

Page 6 of 22

In the LER, an abnormal pressure rise was observed and the most probable cause was that thehorizontal masks generate TE-mode HOMs. To absorb these modes, a winged HOM damper
was designed and installed near the horizontal mask. This reduced the pressure rise to lessthan one tenth of the previous value. Further operating experience in both rings should beobtained and simulation studies should be continued to confirm that these absorbers are
sufficient with higher beam current and for shorter bunches.
7) RF System
PEP II and KEKB have chosen different approaches to solving the problem of the coupledbunch instability driven by the fundamental mode impedance of the RF cavities. PEP II haselected to use a sophisticated and flexible array of feedback loops. KEKB reduces thedetuning needed to compensate for reactive beam loading by increasing the stored energy inthe accelerating cavities.
This has been done using a judicious combination ofsuperconducting single-cell cavities and copper 3-cell coupled cavities, operated in π/2-mode,
where the beam passes through only one of the cavities, and the high-field off-line cavity isdesigned for high stored energy with low losses.
Although the KEKB scheme has been demonstrated to be effective and sufficient for theconditions encountered to date, analysis of operating conditions at design intensity has shownthat it will be necessary to supplement it with feedback systems for the longitudinal coupled
bunch mode (n = –1 mode) in the LER. Furthermore, operation of SuperKEKB, where theLER beam will be increased from 2.6 to 9.4 A, will require implementation of feedback loops
for the –2 and –3 modes, as well.
To prepare for this transition, a fairly straightforward narrow-band, single side band, digital
feedback circuit has been designed and built. It has been successfully tested on the LER,
where two ARES cavities were detuned to excite the –1 mode. With a bandwidth of 1 kHz
and feedback gain of 15 dB, the system was shown to be effective in counteracting the
instability and achieving stable operation under conditions which led to beam abort in lessthan one second when the feedback loop was switched off.
The method and technology used is certainly the right one for the problem presently at hand
and the system is simple to set up and operate and cures the problem at minimum cost.
For significantly higher currents such as the 9.4 A foreseen for the Super KEKB, some further
developments in signal processing may be required as the growth rate of the –1 mode
approaches 104 s-1, a rate comparable to the synchrotron frequency itself. The presently usednarrow band filter will probably not be able to provide the required damping rate due to its
large group delay, but it may be more appropriate to use a wider filter acting on both +1 and –1 modes with a notch at the revolution harmonic to eliminate the spectral line caused by theunequal bunch population.
Additionally, feedback may be needed at more than one ARES station. The feedback phasewill probably also need to be programmed versus beam current as the phase shift at themodulation frequency from the drive signal to the cavity voltage will vary as function of beamloading and cavity detuning.

Page 7 of 22

8) RF Dielectric properties of SiC ceramic absorbers for the ARES cavity
Operation at the higher currents planned for Super KEKB will lead to substantial increases in
the amount of Higher Order Mode (HOM) power deposited in the cavities. Development ofsuitable absorbing materials and design of HOM dampers, for both ARES andsuperconducting cavities, based on those materials, is an essential activity, and the effort to do
this is well underway.
The work to date has been the characterization of two kinds of SiC absorbers and has given
reason to believe that mechanisms are available to control the material dielectric constant.
The Committee encourages the Laboratory to continue this effort, and in particular, to move
rapidly from simulation to testing of prototypes.
9) Superconducting Cavities for KEKB
The superconducting cavities installed as part of the scheme to counteract the impedance ofthe fundamental accelerating mode have continued to perform well. Operational experiencesince the last review was presented. The maximum operating current has increased from
870 mA to slightly over 1 Amp, while the maximum power transmitted to the beam has
remained at 380 kW. HOM power absorbed has increases slightly from 8 to 9 kW per cavity.
The problems experienced have been infrequent, and not indicative of any fundamental
problems for KEKB.
Operation of Super KEKB will require significant increases in fundamental power couplerand HOM damping capability, as has been discussed in previous reviews. In addition, amodest increase in normal operating gradient is needed. The desired gradients have been
demonstrated in the past, so there is little concern on that score and, although there have been
indications of a systematic drop in Q0, there seems to be sufficient refrigeration power
available to deal with it. New fundamental power coupler designs (generally based on
KEKB) being contemplated for other projects, call for substantially higher powertransmission than has been achieved here, and although these have been achieved on a test
stand (APT, SNS) and on a cold cavity (SNS), they have yet to be demonstrated on a cavity
with beam. There seems to be an inconsistency in the amount of HOM power anticipated (50– 80 kW during the previous review, 20 kW now) that needs to be resolved. Overall,
investigation of these issues has not progressed significantly, and the Committee renews its
recommendation that this be started as soon as possible.
10) LER Blowup and HER Transverse CBIGood progress was made on the control of the electron cloud effect. During last year, 266
short solenoids and 106 permanent C-yoke magnets were added to the LER. (A total of 350
permanent magnets are planned to cover all BPMs in the arcs.) As a result, 91% of drift
spaces and 78% of total length are now covered. At present, no ECI has been observed in the
LER if the beam current is below 1.6 A and with 4-bucket spacing, and the threshold is now
predicted to be 1.8 A.
Further studies of the ECI effects are continuing to yield more understanding of its physicalmechanism and hopefully potential cures. One study analyzed the beam spectrum observed
Page 8 of 22

with solenoids on and off, and concluded that the spectrum is consistent with the case whenan overwhelming portion of the electrons originate uniformly from the vacuum chamber pipe
walls. A second study performs a 3-D simulation of the electron dynamics and found thatelectrons can be trapped for a long time in quadrupoles and sextupoles. A third good way to
study the ECI mechanism uses a streak camera measurement looking for bunch-by-bunchshape differences. In particular, there was an intriguing observation of seemingly random
bursts lasting about 5 msec on individual bunches along the bunch train.
The Committee wishes to commend the ECI team for an excellent job done, and encourages
the continuation of these studies. It is also suggested that a means to examine the electron
trapping mechanism in quadrupoles and sextupoles be investigated.
The next important ingredient of pushing to higher luminosity will necessarily involve
reducing the bunch spacing. Presently there is little information for 3-bucket spacing under
the present LER conditions. The Committee feels that this step should be taken early to gain
the maximum benefit and recommends that the KEKB Management examine the possibilityof allocating machine development time to study the running of 3-bucket spacing. This study
should be done as soon as possible, even when there are strong reasons to continue production
running.
A horizontal coupled bunch instability has been observed in the HER. Its growth rate is
substantially higher than expected from a calculation of the resistive wall effect (the resistive
wall calculation agrees with the growth rate in the vertical plane). The instability is ofconcern because an extrapolation predicts a growth rate of 2000 s-1 at the design current. Thisrate will challenge the transverse feedback system. The mechanism of the instability has notbeen identified. If it turns out to be ions, then there will be implications for plans of future
upgrade scenarios.
11) Simulation study of electron cloud
Since the parameters of the electron cloud in an operating machine are hardly ever available
from direct measurements (if at all), simulation studies are of great importance forunderstanding the electron cloud impact on beam dynamics. The efforts of recent years
resulted in the development of versatile simulation tools for analysis of the electron cloudformation and also the interaction with the beam that often causes unwanted effects.
At KEKB, the previous cloud simulations supported the crucial decision to install thesolenoids around as much of the LER circumference as possible, and the present highluminosity performance of the machine is a successful outcome of this decision.
The 3D PIC code CLOUDLAND belongs to a new generation of electron cloud simulation
codes at KEKB, and provides plenty of information on the time-dependent 3D distribution of
the electron cloud and its energy spectrum, and their dependence on dozens of model
parameters. These include different configurations of the magnetic and/or electric field
applied to the cloud volume.
Among the new effects predicted by this code is trapping of electrons in fields withquadrupole and sextupole symmetry (e.g., those produced by the machine lattice elements).
As for the cloud in dipoles, this problem cannot be avoided in regular lattice magnets using
Page 9 of 22

cloud confinement by a solenoid field. Although the on-axis cloud density resulting from thetrapped portion is low, the average cloud density is far from negligible, particularly in the caseof the much higher beam currents required for SuperKEKB. An interesting feature of the newphenomenon is a very long density decay time after the end of the bunch train.
In this simulation, a dipole (or quadrupole) clearing electrode array introduced into thevacuum chamber of lattice dipole (or quadrupole, respectively) results in a drastic reductionof the electron cloud density.
The Committee recommends carrying out a simulation study of the transverse wake from thetrapped cloud in order to assess its effect on the coupled-bunch instability.
The Committee encourages further efforts aimed at finding an electrode configuration thatwould be efficient for clearing the electron cloud.
12) Instability Observations via Streak Camera and PMT
The new LER SR extraction chamber and reflective optics give significant improvement in
performance with much better stability and reduced heating. Optical axis feedback is nolonger needed in the LER*.
Preliminary streak camera observations (Jan 2003) show bunch lengthening in a single bunchfrom 5.8 mm at zero bunch current to 9.5 mm at 1.5 mA. In a bunch train, the bunches in the
tail show ~20% less bunch lengthening than the head.
Observations using a masked PMT signal and BPM oscillation monitor show random
coherent vertical blow-up events along the bunch train with a few tenths of a micron
amplitude. The frequency is shifted from the single bunch tune by as much as δQ = 0.055.
The coherent signal decays faster (1-2 ms) than the incoherent (measured with PMT only)(~10 ms).
At present this seems to be a curious phenomenon and its relation to luminosity performanceis uncertain, but further investigation would likely lead to a better understanding of beam
blowup phenomena.
The proposed correlation of streak camera and PMT/BOM
measurements should improve understanding of this phenomenon.
The Committee strongly encourages more studies with these diagnostics.
* The hysteresis reported last year in the observed beam size vs. current now seems to havebeen an instrumental effect.
13) Transverse coupled bunch instability by electron cloud in LER
In combination with simulations of the electron cloud formation and its long-range wake, theexperimental study of the Transverse Coupled Bunch Instability (TCBI) in LER proved to bean efficient tool for characterization of the electron cloud. In contrast to the vertical beam
blowup in LER that is no longer observable with all the solenoids on, TCBI mode spectra andPage 10 of 22

rise times can still be measured in both “solenoids on” and “solenoids off” modes, provided
that the transverse feedback loop is set open.
Shortly after switching the feedback loop off, the front-end of the transverse feedback system
detects the growth of the multi-bunch instability that eventually causes (partial) beam loss.
The Bunch Oscillation Recorder (BOR) samples the transverse beam offsets, bunch-by-bunch
and turn-by turn, and the bulky data stored in the BOR can be processed off-line. The
measurement does not require dedicated machine study time and could potentially become acloud-status monitoring technique.
The Committee applauds the efforts which led to consistency between the experimental
observations and the simulation results, and recommends further studies of TCBI, particularly
in finding a qualitative interpretation of the observed mode spectra and an explanation for theelectron production pattern which is uniform over the beam pipe surface.
14) Fast beam loss monitor
A fast beam loss monitor system was developed to reduce damage to the BELLE detector andbeam masks from uncontrolled beam losses. The beam abort kicker responds in 1 µs, and thetime delay from the input signal to beam abort is 60-120 µs (6-12 turns). Potential beam loss
trigger signals (PIN loss monitors, RF status) and beam current were monitored over a period
to assess the reliability and response times of various signals for beam loss triggers.
Mask PIN detectors must be vetoed during injection (3 ms) and the current loss trigger wastightened to provide some protection during this period. Operation of the system duringcontinuous injection should be evaluated.
Beam losses dominate aborts. They were found to be associated with coherent oscillations, orchanges in betatron tune. Operating procedures have been modified to reduce these incidents.
Mask damage has been eliminated and radiation damage to BELLE reduced, but monitoringof excessive false trips or missed beam losses should be continued. The fast beam loss
monitor appears to be effective and well implemented. Planning for upgrades, such ascontinuous injection and higher currents, should be undertaken soon if it is not already inprogress. The trip thresholds should be re-evaluated for the new IP chamber.
15) Tune, bunch length, bunch-bunch position
The gated tune-meter technique is known to provide important data on bunch-by-bunch tuneshifts caused by the electron cloud in the LER. At present, this technique is used to measure
the beam-beam tune shifts (closely related to the beam-beam parameter). The tunes ofbunches in collision are compared with those of off-collision pilot bunches, i.e., placed ineach beam of LER and HER so that they are close to the bunch subjected to the gated tune
measurement, but their partner bunches in the opposite beam are missing.
The observed beam-beam tune shifts are in qualitative agreement with the beam-beam
parameter value inferred from the luminosity monitor data. The estimated emittance exceedsthat calculated from the lattice analysis, presumably due to additional beam-beam focusing.
The Committee recommends pursuing this study because direct (and more accurate!)
Page 11 of 22

measurement of the beam-beam tune shift would be of vital importance for understanding thebeam-beam phenomena that limit the machine luminosity.
The bunch length measurements based on the bunch spectrum width showed a serious bunch
lengthening, roughly equal in LER and HER (in excess of 8 mm at 1.5 mA bunch current).
The current-dependent bunch lengths are measured at different values of momentum
compaction and effective peak voltage. More work is needed for quantitative understanding of
the observed data as well as for identification of sources of unexpectedly high impedance inboth rings, taking into account the contribution due to the movable masks.
Preliminary data from the turn-by-turn and bunch-by-bunch BPM showed the feasibility ofmeasuring the bunch-by-bunch orbit distortion and relating it to the beam-beam collisionconditions. The technique looks promising as a potential tool to tune-up the luminosity; that is
why the Committee recommends exploring this possibility, with the emphasis on evaluationof accuracy limits and the reproducibility of the measurement.
16) Bunch by bunch feedback
Transverse bunch-by-bunch feedback dampers work well, and raise the threshold fortransverse coupled bunch operation by more than a factor of 20 in both rings.
In additional, these systems provide a wealth of valuable diagnostic information: bunch
current monitors, global and gated betatron tune measurements, instability mode analysis andbunch oscillation monitor systems with beam abort triggers.
There is significant heating of the vacuum components of the transverse stripline kickers, andcooling is marginal up to the present maximum currents. An upgrade was made during thesummer of 2001 but nevertheless, a breakdown occurred in March 2002 due to an inadequate
mechanism of dealing with the thermal expansion of the kicker stripline. Since the summer of
2002, a third version with an improved BeCu flexible feedthrough has been installed and has
worked well so far.
Although the digital signal processing of the present systems is working well, the technology
is about 10 years old, and digital signal processing technology has been progressing fast interms of memory space and processing speed.
A new development of the next generation digital signal processing systems for transverseand longitudinal bunch-by-bunch dampers has started in collaboration with SLAC using thelatest high performance FPGA technology developed in industry.
Hopefully there will be some performance gain from this development. Will a 20 tap bunchby-bunch FIR filter perform better than a two-tap filter? In principle long filters have longer
group delays than shorter filters. Long group delays increase the sensitivity to tune changes(more difficult to operate) and impose an ultimate limit on the maximum damping rate thatcan be achieved.
The main function of the presently used two tap filters (with no DC response) is to filter out
the average bunch position and thus reduce kicker power, which enables higher gain. The
effective group delay of a two-tap filter system with a one-turn delay between pick-up andPage 12 of 22

kicker is a group delay of 1.5 turns. With a 20 tap filter, where the first tap gives the damping
kick, while the remaining 19 taps are set to give no DC response, the system group delay canbe reduced to about one turn, which in principle increases the ultimate damping rate by afactor of 1.5.
For phase control, it is more effective to use two pick-ups about a quarter wavelength apart(as is presently used in KEKB) than to use the filtering function in the signal processing. The
latter increases the group delay with the associated drawbacks discussed above.
17) IR BPM
The Octopos BPMs near the collision point were specially manufactured with 8 button
electrodes and were fitted into a very narrow space near the IP. The gain coefficients for eachelectrode were calibrated with position mapping data for single-beam operation. The Octopus
BPMs work well and have been very useful in physics running.
18) Progress in Linac: 2-bunch injection etc.
The Injector Linac Group reported on two subjects: two-bunch injection and pulse-coilbreakdown. Two-bunch injection has been a routine operation for positron beams to LER withan injection rate of 3.0 mA/sec, the same rate as for electron beams to HER. It made a great
contribution to KEKB operation by reducing the injection time by one-half. The Committee
congratulates the Injector Linac Group for its excellent performance last year. Since it would
take about 45 minutes to fill 2.6-Ampere current in LER, the final design goal, the Committee
recommends a further study of increasing the positron injection rate in the future, including
continuous injection operation. Continuous injection for the electrons should also be
evaluated, even though injection may be less frequent than for positrons.
Pulse-coil breakdown is considered to be one of possible events in practice. The breakdown
phenomena will be corrected for the new replacement coils, without any great designdifficulty. Since the injector linac is now very well stabilized for the complicated tasks ofproviding various beams to 4 different machines, the Committee praises the linac group for
their dedicated hard work.
19) Beam Energy Spread Monitor in the Linac
A non-interfering beam size monitor has been designed and constructed that uses the higherorder-multipole signals of a beam position monitor to extract the beam size in the KEK linac
to measure the beam energy spread in the J-Bend. This monitor uses a stripline position
monitor specially constructed for the linac with eight strips. The monitor extracts both second
order as well as third order moments. A careful data analysis of the signal moments obtainedwith a linac beam in this monitor was compared with similar data taken with an interferingprofile screen. The monitor was tested at the 1.7 GeV point in the linac J-arc with a beam-size
calibration obtained from beam images. Both data sets agree very well to within a precision oforder of a few percent. The Committee believes that the beam size measurements using thisstripline position monitor are most likely the best implementation of its kind in the world. It
will certainly be a very useful device for improving the injection efficiency to the rings. The
Page 13 of 22

Committee strongly encourages this kind of innovative diagnostic development.
Congratulations to the linac team.
20) Magnet issues, circumference drifta) KEKB magnet system
The KEKB magnet system works very well with the exception of two wiggler magnets that
had coil-layer short problems. No burnt spots have been found by using an impulse test at the
manufacturer. Further investigation into the location and causes of the problem is continuing.
Even though this problem did not have any major impact on KEKB operation, because theaffected pair of wiggler magnets could be temporarily bypassed, and the damaged coils
replaced with spare coils, it is recommended to check all the other wiggler magnets during themachine shutdown periods.
b) Tunnel level changes
Since June 1996 to August 2001, the tunnel level markers on the tunnel wall have beensurveyed 6 times. The results of these surveys show that the tunnel level has changed since
1996, and the changes are very similar as those occurring in the nine years of TRISTAN
operation. This change is not uniform for the whole ring. The largest drift of about 2.5mm/year is in south tunnel section but this has not created any major problem with KEKB
operation until now. The KEKB team has made a preliminary identification of the source ofthe largest drift; it is most likely due to the fact that the surrounding area is more heavily built
up and there are three wells in this section.
c) Circumference drift
The Circumference Closed Orbit Correction (CCC) program maintains the circumferences of
the rings within tolerance by changing the strength of chicane magnets in the LER and bychanging the RF frequency in the HER. Some qualitative analysis of the circumference drift
has been carried out by the KEKB team, such as correlating a long-term drift with the outside
temperature, and identifying the fact that Typhoon No. 21 on 10/1/2003 and the resulting
rapid atmospheric pressure drop caused a temporary circumference expansion, and so on. The
Committee endorses the KEKB team to continue quantitative studies of the contribution ofeach environmental variable to the circumference drift of the KEKB rings, even though it has
no real impact on operations.
21) Progress in the Control System
The Control System has continued to function with few problems. Recent hardware Upgrades
include upgrading the Ethernet network and buying additional servers. The primary software
upgrade is to provide additional capabilities for data archiving. About 800 GB per year ofdata is now archived in discs or NAS RAID5 storage. Further back-up storage is available in atape storage facility.

Page 14 of 22

The Controls group maintains strong collaborations with laboratories in China and Korea, as
well as being an active member of the EPICS collaboration.
There is a problem with VXWORKS, the operating system for the IOC front-end computers.
The manufacturer will no longer support VXWORKS on new HP platforms, so all of the
EPICS Collaboration members need to find a long-term solution. The KEKB Controls Groupis encouraged to develop a solution and implement it before this has an impact on operations.
22) iBump Feedback Tuning
Vertical steering at the IP is based on the beam-beam kick and works well. This is not the casein the horizontal plane, and maintaining optimum steering to maximize luminosity requires
significant operator skill and experience.
A clever and complex feedback system has been developed incorporating a large amount of
this experience into a software tool which can operate in several modes: i) injection, ii) directtuning, iii) lifetime feedback and iv) size feedback.
The Committee would like to congratulate the Operations Team from Mitsubishi Electric
Service Company on this remarkable achievement and encourages further development.
23) Facilities and operation
This is the first time that KEKB facilities and operation have been presented to the Committee.
The report is very impressive and interesting, not only in the reliable and stable operation of
the facilities, but also because of many practical operation data that were reported. To reduce
the KEKB construction budget, most KEKB facilities (including electricity, cooling water, airconditioning, building and the tunnel) made use of the existing TRISTAN facilities that havemore than enough capacity for KEKB operation. All of these facilities worked very well since
KEKB commissioning. However, since most of these facilities are already about 20 years old,
aging problems may appear in the near future. The Committee recommends that the KEKB
team prepare a long-range plan to upgrade the facilities, taking into account the needs of the
upgrade.
24) Beam-beam simulation and experiment
The beam-beam simulation presented uses a 3-D strong-strong model with longitudinal slices
to simulate the effects of the crossing angle and the variation of beta through the collision
region. Using an interpolated kick that depends on the longitudinal position of each particle
in its slice significantly reduces the number of slices needed to produce stable results. The
simulations are in good agreement with measurements with respect to variation of bunch
current, coupling, and operating tunes.
The prediction of an improvement in luminosity by a factor of 2-4 using crab compensation of
the crossing angle (presented in section 27) is very encouraging. It is reasonable to expect,however, that new disruptive phenomena may develop with flat beam ξY> 0.1.

Page 15 of 22

The Committee applauds the KEK staff on the development of this code and encourages
continued work with frequent comparison with experimental data.
25) Further luminosity upgrade
The spectacular increase in luminosity in KEKB over the past two years is a result of many
carefully organized changes to the operating parameters of KEKB including the reduction of
betay*, the increase in the number of bunches and current, the reduction of the electron cloud
effect, and the move of the horizontal tunes to near the half integer. These changes have beenscientifically studied and documented to make sure the optimum parameters have been chosen.
However, there are fewer choices to be used in the future to improve the luminosity andfinding the best path becomes a challenge.
One obvious path is to increase the number of bunches and, correspondingly, increase thebeam currents. Since all the buckets are used in the present “every fourth” bucket pattern, a
new pattern is needed. “Every third” pattern is likely the next. However, there is a fear thatthe electron cloud effect (ECI) may reappear with this pattern. Accelerator studies arerecommended to study if the “every third” pattern has ECI consequences.
Another method to increase the luminosity is to shorten the bunch length below theapproximate 9 mm at high currents. A shorter bunch would allow a slightly reduction of
betay*. The bunch length may possibly be reduced with a new low momentum compaction
lattice or possibly the “negative alpha” lattice. These possible lattices should be tested on thepresent accelerator.
The use of crab cavities to horizontally rotate the beams as they enter the collision point could
reduce or eliminate the adverse effects of the crossing angle on luminosity. The developmentof crab RF cavities at KEKB is now at a stage where an accelerator beam test would be very
timely and could potentially increase the luminosity significantly (20 to 50%). The
Committee recommends the rapid implementation of the first crab cavity in the HER, andthen the LER, as soon as possible.
Finally, the use of continuous injection could increase the integrated luminosity per day by
about 15 to 25 %. Continuous injection could eliminate the lost time due to injection and the
decay of luminosity with declining beam currents. Continuous injection tests have been triedon KEKB and the accelerator worked well. The BELLE detector had problems with event
triggering that are now, apparently, fixed. Thus, the Committee suggests that continuous
injection be tried again with the hope of increasing the integrated luminosity per day.
26) SVD2The SVD1 is scheduled to be replaced by a new SVD2 in the coming summer. In SVD2, theradiation hardness has been increased from 1 Mrad to 20 Mrad, the number of silicon layers
has increased from 3 to 4, and its IP chamber radius reduced from 2 cm to 1.5 cm. An
additional Tantalum shielding pipe is installed, while the SR masks are removed to avoid
HOM heating. These seem to be good innovative changes and should improve the robustnessof the SVD design.

Page 16 of 22

Careful studies were made to estimate the radiation dose as well as developing a heating load
budget of the SVD2 design. Radiation doses from particle background were estimated using
GEANT and TURTLE, while the SR background was simulated using EGS4. These dose
rates are found to be acceptable.
The weight stress of the beryllium pipe assembly was carefully checked by a 3-D finite
element analysis using SOLID and is judged to be acceptable.
The budget of the heat load from SR, direct beam current ohmic heating, and HOM heating
was estimated using MAFIA and ABCI. Heating on the IP chamber is found to be 70 W, apleasant factor of 5 reduction from SVD1.
The cooling system uses liquid (normal paraffin) flowing in a 0.5mm gap in a double walled
beryllium pipe. A corrosion test has been performed. The flow rate of 2 l/minute is high and it
is suggested that its turbulence effect be checked. Relief valves have been included.
27) Luminosity boost by head-on (crab) collision
The demand to boost the luminosity 10 or even 100 times in the SuperKEKB design means
searching for radical ways of raising the currently achieved beam-beam limit, provided that
other factors, which limit the bunch intensity, have eventually been overcome.
Preliminary results of the recent beam-beam simulation with a 3D PIC code have shown acritical influence of the crossing angle on the attainable beam-beam parameter and hence on
the luminosity limit. Both weak-strong and strong-strong models indicate a substantial
increase in the beam-beam parameter for the case of head-on collision with the SuperKEKB
design parameters, the latter shows a saturation at ξ = 0.11 for a bunch current of 1.5 mA, theformer does not show any beam-beam limit with ξ > 0.2. These values are adequate for theSuperKEKB design luminosities of 1035 and 1036cm-2s-1, respectively.
One possible explanation of the unusually high beam-beam parameters achieved for the flat
colliding beams in simulation and adopted in the new project is related to the uniqueexperience of the present KEKB machine which operates very close to the half-integer
resonance; the working point now is x/y = 0.51/0.56.
Implementation of the crab-cavity scheme gives a way of testing the head-on collisiongeometry at KEKB, which is important for the future upgrade. The Committee recommends
re-considering the current plan for the crab cavity installation in order to speed-up the
installation of the crab cavities in both HER and LER.
The Committee also recommends pursuing detailed studies of alternative ways to boost theluminosity. The Committee encourages further development of the 3D beam-beam simulation
at KEKB, benchmarking it against analogous codes at other labs as well as carrying out
systematic comparison of the simulation results with experimental results available frommodern high-luminosity colliders.

Page 17 of 2228) Crab Cavity R&D
Since the last review, there has been good progress in understanding the processes that limit
the cavity performance and testing has proceeded well.
At the previous review, it was proposed that the crab cavity would be fabricated from niobium
sputtered on a copper base, but during this review it was clear that work is focusing on aconventional sheet niobium construction. The second prototype cavity has been completed,and has achieved the desired gradient and Q0 performance, and work is proceeding on thedesign of the cryostat. The measured performance has been very consistent over multiple
tests of the two cavities, even when the unusual beam-line power coupler for ‘non-crab’
modes is installed. Cavity production processes, based on electropolishing, have been
established, and produce a modest margin of Q0 above the required value of 109, and acomfortable gradient margin.
A conceptual design of the cryostat has been prepared, and detailed design work is underway,
but this task is unusually difficult, given the complexity of the basic cavity geometry and theextremely cramped space into which it must be squeezed.
29) Lattice design for Crab Cavity
KEKB staff have presented the hardware changes necessary to provide a high horizontal beta
for the crab cavity in the HER as well as the required phase advance to the interaction point tofully compensate the crossing angle of the HEB. A target βX(crab cavity) of 200 m with zero
αX,Y was achieved while maintaining other important optics constraints in the HER. The
number of separate quadrupole power supply circuits must be increased from 8 to 18. The
new optics scheme provides ample flexibility (70m < βX (crab cavity) < 800m) and the phaseadvance to the IR may be varied by ±28 degrees. Dynamic aperture is unchanged from that ofthe present KEKB.
The Committee approves of this work and supports the development plan to assess crab cavity
dynamics and move ahead to designing LER crab cavity optics.
30) IR Design for SuperKEKB
Considerable work has been performed on the design of an upgraded interaction region for
KEKB with the aim of achieving a betay* of 3 mm. The design work so far has been excellent.
The new interaction region layout has incorporated a crossing angle of 15 mrad and has the
final quadrupole doublet moved closer to the collision point. The local high field solenoids
used to compensate the BELLE solenoidal field will now be superimposed on the field of thesuperconducting quadrupoles. The superconducting solenoid coils will be wound over thequadrupole windings with some additional dipole correction elements added. These magnet
designs seem reasonable and carefully estimated.
However, the forces on the superconducting magnets inside the BELLE solenoid are quite
large (several tons) and the containment of these forces must be carefully considered in thedesign of the supports, and include forces created due to current ramping or possible quenches.
Page 18 of 22

In the present KEKB interaction region, the outgoing beams have damaged downstream
vacuum chambers from high power synchrotron radiation. These heating problems have been
repaired on the present accelerator. However, special offset orbits are now used with the HER
and LER beams as they enter the interaction point to help reduce the downstream heating. The
purpose of these offset orbits should be investigated so that the reasons can be included in the
new interaction region design. The future interaction region must also deal with about ten
times the beam current. Therefore, the Committee suggests that the vacuum chamber design
be started with the aim of solving the synchrotron radiation heat loading downstream.
31) Dynamic aperture of SuperKEKB
A reasonable first lattice design has been made for SuperKEKB. The LER in this design
keeps half of the wiggler magnets as the present LER, and therefore maintains part of theflexibility in its emittance control. On the other hand, momentum compaction is sufficiently
flexible to allow a negative alpha lattice. It is suggested that some test of negative alpha lattice
be performed in the present KEKB to explore its effectiveness in reducing bunch length aswell as its limitations.
The dynamic aperture of the SuperKEKB was obtained by applying SAD 3-D tracking for1000 turns. So far only the bare lattice has been studied. The dynamic aperture found is quite
reasonable, and satisfies the injection and lifetime requirements. Momentum aperture is foundto be more than ± ½% with a reasonable Touschek lifetime of 230 min. This work should becontinued to included magnet errors and beam-beam effects.
32) Impedance estimation
Impedance estimation by calculation (with 2D code ABCI and 3D code MAFIA) is very
important for KEKB as transverse and longitudinal coupling impedances are important
limitations to machine performance. These limitations are due to excitation of coupled bunch
instabilities as well as HOM heating.
Beam based verifications of the total loss factor (synchrotron phase versus current) indicatesthat the integrated loss factor is larger than expected. On the other hand, numerous elements
installed in the machine have not been included in the impedance budget.
Also bunch lengthening versus current is much larger than expected although it is not clear
whether the bunch lengthening model is only based on potential well model or includes
turbulent bunch lengthening.
Good agreement was found by comparing measured HOM power levels with expected HOM
loads from calculated loss factors.
An approximate criterion for mesh size required for calculation of shallow tapers.
In view of the importance of impedance issues for further upgrades in beam currents andluminosity, the Committee recommends that this activity continues and that all elements
installed in the machine should be calculated and the calculations verified by experiments
Page 19 of 2233) Vacuum Chamber R&D
The presentation includes challenging ideas, especially the RF shield. The newly proposed
RF shield has teeth and grooves alternatively along the duct periphery. The gap clearance
between them is too narrow, so technical difficulties are predicted, but this ideal design is
expected to give good performance. It is recommended that a mock-up be built and installedin the KEKB ring as soon as possible. Based on the experience of manufacturing copper
ducts and of operation in a real machine, the proposed antechamber structure seems safe and asound design. The duct has cooling water passages that are arranged on the entrance slit
shoulders of the side channel; this is useful to protect the vacuum duct from high powerradiation generated by bad steering under high beam current conditions. Following the test of
the RF shield, it is planned to manufacture, install and test a new type antechamber in the
KEKB ring.
The Committee recommends that system-engineering studies of the new vacuum chamber be
carried out, including the fabrication tolerances and the new installation techniques that will
be required.
34) C-Band R&D
The development of the C-band equipment needed to increase the energy of the positron beamfrom 3.5 to 8 GeV is very advanced. The Committee was presented with information on allelements: modulator, driver klystron, RF window, accelerator guide, SLED cavities andwaveguide components. The Committee concludes from this that there is relatively little
technical risk associated with the linac upgrade.

Page 20 of 22

Appendix A
KEKB Accelerator Review Members
Andrew Hutton

JLabChairmanAlexander Chao

SLAC

Warren FunkJLabGeorg Hoffstaeter

Cornell (excused)

Won Namkung

PostechFleming Pederson

CERN

Eugene A. Perevedentsev

BINP

David Rice

CornellJohn Seeman

SLAC

Wang Shuhong

IHEP

Shin-ichi Kurokawa

KEK Secretary, Accelerator

Fumihiko Takasaki

KEK Secretary, BELLE

Page 21 of 22

Appendix B
Agenda of the Eighth KEKB Accelerator Review Committee
Feb. 10 (Mon.)
8:30- 9:00
9:00- 9:15
9:15- 9:35
9:35-10:05
10:05-10:20
10:20-10:40
10:40-11:00
11:00-11:20
11:20-11:40
11:40-12:00
12:00-13:00
13:00-13:20
13:20-13:40
13:40-14:00
14:00-14:20
14:20-14:40
14:40-15:00
15:00-15:15
15:15-15:35
15:35-15:55
15:55-16:15
16:15-16:35
16:35-16:55
16:55-17:15
17:15-17:35
17:35-17:55

Executive session
Introduction
BELLE status
Machine performance since Feb. 2002
Break
IP Vacuum- from the first anomaly to the final large Helium leak
Beryllium Chamber
Movable masks
RF System
ARES（RF Dielectric Properties of SiC Ceramics）
Lunch
SCC
LER blowup and HER transverse coupled bunch instability
Simulation study of electron cloud
Instability measured by streak camera
Transverse coupled bunch instability by electron cloud in LER
Fast beam loss monitor
BreakTune, bunch length, bunch/bunch position
Bunch by bunch feedback
IR BPM
Progress in Linac: 2 bunch injection, etc.
Beam size measurement at Linac
Magnet issues, circumference drift
Progress in control system“iBump” Feedback Tuning

18:00-18:45

Executive session

Feb. 11 (Tue.)
8:30- 9:00
9:00- 9:20
9:20- 9:40
9:40-10:00
10:00-10:20
10:20-10:40
10:40-11:00
11:00-11:20
11:20-11:40
11:40-12:00
12:00-13:00
13:00-13:20
13:20-13:40
13:40-14:00
14:00-14:20

Executive session
Facilities and operation
Beam-beam simulation and experiment
Further luminosity upgrade
Break
SVD2
Luminosity boost by head-on(crab) collision
Crab cavity R&D
Lattice design for crab cavity
IR design for SuperKEKB
Lunch
Dynamic aperture of SuperKEKB lattice
Impedance estimation
Vacuum chamber R&D
C-band R&D

14:30-18:00
18:00-20:00

Executive session
Working dinnerFeb. 12 (Wed.)
8:30-9:00
9:00-9:30

Interaction with KEKB staff members
Closing

Page 22 of 22

K. OideF. Takasaki
Y. Ohnishi
K. Kanazawa
S. UnoK. Shibata
S. Yoshimoto
Y. Takeuchi
S. Mitsunobu
H. Fukuma
L. F. Wang
J. Flanagan
S. S. WinH. Ikeda
T. Ieiri
S. Hiramatsu
M. Tejima
T. Kamitani
T. Suwada
M. Masuzawa
T. Nakamura
Y. Satoh

M. Yoshioka
M. Tawada
Y. Funakoshi
T. AbeK. OhmiH. NakaiA. Morita
N. Ohuchi
H. KoisoS. Stanic
Y. Suetsugu
S. Fukuda