KEKB Accelerator Review Report
Andrew Hutton
ChairmanKEKB Accelerator Review Committee

Committee Membership• The Eleventh KEKB Accelerator Review Committee
meeting was held on March 20-21, 2006.
• John Seeman from PEP-II was unable to attend andwas replaced by Yunhai Cai, an accelerator physicist
working on PEP-II• Dave Rice, Flemming Pedersen, and Shin-ichi
Kurokawa were also unable to attend this meetingKEKB Accelerator Committee Members
Andrew Hutton
JLab Chairman
Yunhai Cai
SLAC (replacing John Seeman)
Alexander Chao
SLAC
Warren FunkJLabOswald Gröbner
CERN (retired)Georg Hoffstaetter
Cornell
Won Namkung
POSTECH
Flemming Pedersen
CERN
Eugene Perevedentsev BINP, Novosibirsk
David RiceCornell (unable to attend)
John Seeman
SLAC (unable to attend)
Wang Shuhong
IHEP, Beijing
Katsunobu Oide
Shin-ichi Kurokawa

KEK Secretary
KEK Secretary (unable to attend)Overview of Performance• KEKB has made excellent progress since the lastCommittee meeting• Peak luminosity has increased to a new world recordof 1.627 x 1034 cm-2s-1• At this time last year it was 1.52 x 1034 cm-2s-1• Maximum integrated luminosity was 1.183 fb-1 in 24hours• KEKB was and was awarded the S-Equivalent ratingby the Council for Science and Technology Policy –the top rating• This rating was awarded both for the Physics output
and also explicitly for the machine performanceKEKB History

Last Review

Luminosity• KEKB continued to make steady progress• KEKB holds all of the worldwide luminosity records:• highest peak luminosity: 1.627 x 1034 cm-2s-1• highest daily integrated luminosity: 1183 pb-1
• highest weekly integrated luminosity: 7.36 fb-1
• highest 30-day luminosity: 29.02 fb-1
• The luminosity has improved only by ~10% since last year
• Probably close to saturation
No major improvement likely until crab cavities are installed
May take many months to tune crab cavities to see full benefit

Detailed Look at Luminosity• KEKB operated perfectly up to summer shutdown• New crab lattice was installed in summer shutdown• Optics change to prepare for hardware installation• This did not go well, took several months to recoverpeak luminosity• Luminosity still much more variable than before• Weekly and monthly luminosity still not recovered• Committee believes this is due to crab lattice• Probably less tolerant to off-momentum particles

Hardware• First evidence of damaged“standard” components• Significant cause for worry• Accelerator availability was
lower in 2005
• Caused by bad recovery
from summer shutdown• More downtime in October2005 than entire 2004!

The Committee is concerned about the damaged
standard components but does not believe that
this is an immediate problem

Belle Detector• The Belle detector has accumulated 563 fb-1, anotherworld record• 365 fb-1 last year
• “Oide Scenario” predicted 550 fb-1 at this time
• Extraordinarily accurate prediction!
• The Belle detector is working extremely well except fora period after the operating system was updated

Based on
Crab Cavities

Official Goal

We are here.

••

550 /fb will be reached before the Crab Cavity Installation.
The Official Goal (=1 /ab) will be achieved before Summer
2007.

Crab Cavity• Progress in crab cavity has been excellent• Most components ready to go• Minor “bump in the road” recently• Problems with assembly of coaxial coupler• Heavy piece (~100kg)• Must be inserted with sub-millimeter tolerances• The Committee examined the process in detail andendorses the present design• Made suggestion for improved fixtures

Repeat Recommendations (3rd time)
1. The Committee strongly endorses the plan toassemble, test, install and commission one crab
cavity in each ring in the summer shut down of 2006
Reminder – this will be the first time that crab
crossing has been attempted
2. The Committee endorses the studies to design amajor luminosity upgrade (SuperKEKB) aimed at aluminosity of 2-4 x 1035 cm-2s-1 and recommends thatthey be continued

Repeat Recommendations ( 2nd time)
3. The Committee strongly endorses the plans for
simultaneous injection in all four rings
4. The Committee recommends continuing the studies
of a movable mask which is ‘electrically invisible’(rod with ceramic support) and has a much lower loss
factor• A significant amount of R&D remains todemonstrate a reliable, operational movable maskwith a reduced loss factor
5. The Committee feels that HOMs is one of the limiting
factors in increasing the current. Detailed studies ofthe vacuum components including proper damping
and component cooling should be continued

New Recommendations
6. The Committee supports the present approach tocoaxial coupler assembly, and recommends that
continued efforts be made to improve the alignment
fixtures, rather than searching for a new assembly
approach
7. The Committee is agreed that the cavities should beinstalled in the rings at the earliest possible time, andcommissioned, so that the benefits and limitations
associated with them can be determined
8. The Committee recommends that both cavities
should be cryogenically tested with the complete RF
system before any installation is started

New Recommendations
9. While the Committee believes that the crab cavity
program will be successful, it requests that the KEK
management create a road map for KEKB operations
under two different scenarios:• The crab cavity is successful and KEKB
operations continue at ~400 fb-1 per year
• If after considerable effort, the crab cavity is
unsuccessful, KEKB operations continue at~200 fb-1 per year.
It would also be extremely helpful for planning andoptimizing operations if the KEK management could
provide an indication of the kind of information thatwould influence a decision on SuperKEKB (e.g. newphysics found at Upsilon 3S or 5S)

New Recommendations
10. The Committee recommends studying carefully thetolerances of the new crab lattices to check if they
are more susceptible to errors, such as the orbit drift
and identify the causes of the luminosity fluctuation
11. The Committee recommends measuring thenonlinear dispersion as an additional check of theoptics model
12. The Committee recommends that a close follow-up of
the failures of the standard vacuum components
should be made to establish critical operating
parameters and to put limits on themNew Recommendations
13. The Committee recommends studying the effect ofC-type magnets mounted on the antechamber, thesolenoid field, and of a reduced secondary electron
yield (SEY) (by coating or surface treatment) insimulations of the electron cloud densities on thebeam axis
This is for SuperKEKB
14. The Committee expresses strong support for further
studies of low SEY coatings and for testing thesecoatings under machine conditions

New Recommendations
15. The Committee recommends that an effort be made tounderstand the mechanism of the sidebands, their role ofbeing a signature of the electron cloud instability onset, andtheir apparent correlation to the luminosity
16. The Committee supports the proposal by the KEKB team todirectly measure the photo-electrons in the quadrupoles; it
may give clearer information on the electron cloud in thequadrupoles. Refined simulations of this effect should also becontinued
17. The Committee recommends that efforts should be made toestimate the power deposited at the joints between different
parts of the coaxial coupler using the presently understoodmechanical tolerances

Personal Viewpoint• KEKB has made excellent progress• Luminosity is almost saturated now• Expect crab cavities to give large improvement –never been done, not easy
• SuperKEKB is still the long-term goal of the KEKB
accelerator physicists• KEKB should lay out a roadmap for the future of KEKB
• I am concerned that in a few years, LHC and BEPC
will be the only operating HEP colliders• ILC is a long way away

Summary• KEKB is still the world leader• Great team, motivated and dedicated• KEKB can expect to maintain lead for several years• Crab cavities should ~double luminosity• But - may reduce luminosity for several months
before improvement is seen
• Little improvement without crab cavities• SuperKEKB would be an excellent match to the KEKB
staff if the physics case justifies it