― 6 ―6

JeŠerson Lab.(E-mail: andrew＠jlab.org)

― 6 ―6

「加速器」Vol. 6, No. 1, 2009 (69)

J. Particle Accelerator Society of Japan, Vol. 6, No. 1, 2009

寄 稿

The KEKB Machine Advisory Committee

Andrew HUTTON

1. Introduction

On December 10, 2008, in Stockholm, YoichiroNambu, together with Makoto Kobayashi and Toshi-hide Masukawa, were awarded the Nobel Prize inPhysicsNambu ``for the discovery of the mechanismof spontaneous broken symmetry in subatomic phys-ics'', Kobayashi and Masukawa ``for the discovery ofthe origin of the broken symmetry which predicts theexistence of at least three families of quarks in na-ture.'' In the Presentation Speech, Professor LarsBrink, Member of the Royal Swedish Academy ofSciences and Member of the Nobel Committee forPhysics, declared: ``During the past decade, elementa-ry particle physicists have measured Kobayashi andMasukawa's theory with great precision and foundthat it really does ˆt the data.'' The Nobel Foundationelaborated: ``It is only in recent years that scientistshave come to fully conˆrm the explanations thatKobayashi and Masukawa made in 1972. They ex-plained broken symmetry within the framework of theStandard Model, but required that the Model be ex-tended to three families of quarks. These predicted,hypothetical new quarks have recently appeared inphysics experiments. As late as 2001, the two particledetectors BaBar at Stanford, USA and Belle at Tsuku-ba, Japan, both detected broken symmetries indepen-dently of each other. The results were exactly asKobayashi and Masukawa had predicted almost threedecades earlier.''

It was because of these conˆrming measurementsthat Katsunobu Oide, head of the KEKB Group, andFumihiko Takasaki, the ˆrst head of the BELLE De-tector Group, were invited to Stockholm to attend thepresentation ceremony. Jonathan Dorfan and DaveHitlin, representing the PEPII B-Factory at SLAC,

were also invited. The presence of these scientists atthat event underscores the importance of the researchcarried out at the B-factories. It also underscores whyparticipation on the KEKB international Machine Ad-visory Committee has been such an extraordinaryprofessional and educational experience for those of uswho have been privileged to serve.

2. The Beginning

Shin-ichi Kurokawa, the KEKB Project Leader, iswell known for his international outlook, for hisscientiˆc humanitarianism, for his involvement inSESAME, and for his scientiˆc travels. This states-man of science had long believed that a scientiˆc en-terprise of this scope and importance would need anadvisory Committee that was international, and Direc-tor General Hirotaka Sugawara agreed. Thanks toKurokawa-san and the Director General, that ˆrstmeeting in 1995 enabled the authorities in Japan to seehow such a Committee would work.

The earliest incarnation of the Committee ˆrst metin June 1995, chaired by the late Gustav-Adolph Vossof DESY, whose work had included leading the con-struction of PETRA, PIA, and the electron ring forHERA. Besides Chairman Voss and myself, the otheroriginal Committee members were Alex Chao ofSLAC, Dave Gurd of LANL, Susumu Kamada ofKEK, Hasan Padamsee of Cornell, Flemming Peder-sen and Wolfgang Schnell of CERN, John Seeman ofPEPII at SLAC, Dieter Trines and Anton Piwinski ofDESY, and, as Committee Secretaries, Shin-ichiKurokawa and Fumihiko Takasaki.

The executive summary that ˆrst year began, ``B-factories belong to a new generation of e＋e－ collidersthat exceed in many aspects known performance dataof existing electron positron colliding machines by

― 7 ― 7

Fig. 1 Katsunobu Oide in the control room withHaruyo Koiso

― 7 ― 7J. Particle Accelerator Society of Japan, Vol. 6, No. 1, 2009

The KEKB Machine Advisory Committee

large factors and present a real technical challenge.The desired luminosity of 1034 cm－2s－1 in B-factoriesis by a factor of 50 higher than that of the highest lu-minosity in presently existing e＋e－ storage rings.'' Itwent on to outline the challenges and to propose thatthe ``KEKB design approaches these challenges in abold and highly original way.'' The Committee alsooŠered what it called ``cautionary words,'' but con-cluded by expressing conˆdence ``that the design ob-jectives can be met.''

After a hiatus of a year and a half, it was decidedthat the international Machine Advisory Committee(MAC), would meet annually in February or March,with the ensuing reports to be used in KEK's annualperformance reviews. To make the Committee evenmore international, two Asian members were added:Won Namkung of Postech, Korea, and Wang Shuhongof IHEP, China, both of whom are still actively in-volved. This then was the Committee that oversaw theconstruction project, which lasted until 2000.

3. KEKB Construction

As in all such large, cutting edge projects, therewere many di‹cult decisions to be made and the Com-mittee evaluated the suggestions of the KEKB expertsand provided advice. We watched as TRISTAN wascleared out of the tunnel and the new components ar-rived, were measured and installed. Finally, the greatday arrived and commissioning of KEKB started onDec. 1, 1999. The ˆrst electron beam was stored in the8 GeV high energy ring only twelve days later, and onJan. 10, 2000 positrons were injected into the 3.5 GeVlow energy ring and subsequently stored. By the mid-dle of April 2000, 524 mA of e－ and 514 mA e＋ wereaccumulated and stored in the two KEKB rings. At thebeginning of May 2000 the BELLE detector wasmoved into place, and one month later the ˆrst hadron-ic events were produced in e＋e－ collisions and ob-served in BELLE. This rapid start-up showed howwell the KEKB team had done their job and gave an in-dication of the future performance.

4. Commissioning and Operation

At that time, most machine advisory Committeesclosed down when commissioning began becausefunding agencies no longer required them. But to the

credit of Kurokawa-san and the successive DirectorsGeneral, the KEKB MAC has continued, not only dur-ing commissioning, but into the period of operationand improvements.

The sixth KEKB Accelerator Review Committee in2001 was the ˆrst meeting without Dr. Gustav Voss,who had been the Chairman of all previous meetings. Itook over as Chairman, and the Committee member-ship was partially modiˆed to be able to focus on theissues of a running machine. It also coincided with thepromotion of Katsunobu Oide to become the head ofKEKB Operations (Fig. 1). It has been Oide-san whohas provided the inspiration and leadership for makingKEKB a world leading accelerator.

It's interesting to recall how encouraging the Com-mittee was able to be in the 2002 report (Fig. 2). TheCommittee wrote, ``KEKB has made spectacularprogress over the last year, breaking almost all of theprevious worldwide luminosity records: highest peakluminosity: 6.6×1033 cm－2s－1, highest daily integrat-ed luminosity: 329.5 pb－1, highest 7 day integrated lu-minosity: 2.06 fb－1, and highest 30 day luminosity:7.56 fb－1.''

Similar encouraging progress was highlighted in allof the Committee reports from 2003 to 2006 as the lu-minosity reached the design value of 1034 cm－2s－1 inMay 2003, the ˆrst electron collider to reach this mile-stone. The collider set the current world luminosityrecord of 1.71×1034 cm－2s－1 in November 2006.

― 8 ―8

Fig. 2 The KEKB Machine Advisory Committee at work

Fig. 3 Kenji Hosoyama, leader of the crab cavity con-struction with Committee members

Fig. 4 Committee members observing machine studiesin the control room

― 8 ―8 J. Particle Accelerator Society of Japan, Vol. 6, No. 1, 2009

Andrew HUTTON

5. Crab Cavities

In 2006, following more than a decade of develop-ment, two superconducting crab cavities were in-stalled to increase the luminosity even further basedon detailed simulations that predicted a small area oftune space where the luminosity would be enhanced.The construction of the crab cavities was extremelydi‹cult and required the combined skills of the KEKBstaŠ and even some useful advice from the Committeemembers for the ˆnal assembly (Fig. 3).

By November 2007, the KEKB experts hadmanaged to tune up the luminosity to 1.47×1034 cm－2

s－1, obtained with smaller beam currents, but had notmanaged to exceed the previous luminosity record. Itwas believed that the tuning algorithms were not ableto converge on the correct settings, so the Committee

was invited to a new type of meeting, to be held in thecontrol room. As the machine was brought up from anextended downtime, the KEKB experts explainedeach step that was to be carried out, and then invitedthe Committee to observe as the procedure was car-ried out, inviting suggestions for improvement (Fig.4). This showed a rare display of conˆdence in theCommittee: most of us involved in accelerators wouldnot have the courage to allow ``outsiders'' to see ourproblems in real time.

Following several days in the control room, theCommittee exited, vanquished. We had made manysuggestions, several of which were enacted immedi-ately, without being able to improve on the optimiza-tion procedures already developed by the KEKB ex-perts.

― 9 ― 9

Fig. 5 Yoko Hayashi and Andrew Hutton in discussion

― 9 ― 9J. Particle Accelerator Society of Japan, Vol. 6, No. 1, 2009

The KEKB Machine Advisory Committee

6. The Future

Preparations are now underway for the next phase,developing plans for SuperKEKB with an initial lu-minosity goal ten times that of KEKB. The Committeeis convinced that the KEKB accelerator experts willapproach this next adventure with as much boldnessand originality as they did for KEKB.

7. Acknowledgements

For those of us who have served for so long, thisCommittee has been an extraordinary experience. Wegained far more than we could give. This discussionwould not be complete without mentioning our won-derful organizer, Yoko Hayashi, who has been provid-ing organizational support since the very beginning(Fig. 5). In fact, many of us cannot imagine coming toKEK without Hayashi-san to look after our needs.

Appendix

Members of the KEKB Machine Advisory Committee

19952009 (in alphabetical order):Yunhai Cai (SLAC) [2006]Alexander W. Chao (SLAC) [19952009]Dave Cinabro (Wayne Univ.) [1997, 1998]Nikolay Dikansky (BINP) [19972000]Warren Funk (JLab) [20032009]Oswald Gr äobner (CERN) [20042009]Dave Gurd (LANL) [19952000]Heino Henke (Technische Univ. Berlin) [20052007]Georg HoŠstaeter (DESY) [20012006]Stephen D. Holmes (FNAL) [2001]Andrew Hutton (JLab) [19952009]Susumu Kamada (KEK) [1995,1997]Peter Kneisel (JLab) [2002]Masanori Kobayashi (KEK) [19982002, 2004]Shin-ichi Kurokawa [19951999, 2003, 20062008]Trevor Linnecar (CERN) [20052009]Won Namkung (Postech) [19992009]Katsunobu Oide (KEK) [20062009]Hasan Padamsee (Cornell Univ.) [19952000,]Fleming Pedersen (CERN) [19952009]Eugene A. Perevedentsev (BINP) [20012009]Anton Piwinski (DESY) [1995]David Rice (Cornell Univ.) [20012009]Wolfgang Schnell (CERN) [19952003]John T. Seeman (SLAC) [19952009]Wang Shuhong (IHEP) [19972009]Ronald Sundelin (JLab) [19992001]Fumihiko Takasaki (KEK) [1998, 1999, 2003]Dieter Trines (DESY) [19952000]Gustav-Adolf Voss (DESY) [19952000]Masanori Yamauchi (KEK) [2009]