Leader of the PAC

29 April 1999


This years’s Particle Accelerator Conference in New York City on 29 March – 2 April included news from several major new machines that are beginning to flex their muscles. Both of the new B-factories, PEP-II (SLAC, Stanford) and KEKB (KEK, Japan), had seen collisions and measured luminosities. They are both rolling in their detectors ­ BaBar and Belle respectively ­ and both foresee physics runs from May.

PEP-II has achieved 750 mA of electrons and 1171 mA of positrons, which are believed to represent the highest positron current ever stored, with a peak luminosity of 5 x 1032/sq. cm/s (design 3 x 1033) and an average luminosity of 2 x 1032 over substantial periods.

PEP-II’s goal for its May-August run is a maximum luminosity of 1033 and an average of 5 x 1032. KEKB has achieved 420 mA electrons and 380 mA positrons, with a maximum luminosity of 1.2 x 1031, on 25 March. Both KEKB and PEP-II observe dust trapping and reduced lifetime in a range of currents, and evaporation above, as well as pressure runaway as a result of electron multipacting. Both machines need feedback to stabilize the beams.

Linear optics in both agree well with models. There are no serious single-bunch instabilities and no multiple bunch instabilities related to modes in the RF cavities in KEKB.

The new RHIC heavy-ion collider had been hoping to provide headline news at PAC, but unfortunately it suffered a serious mechanical failure. Leak checks are now complete, but power supplies are still being installed. Cooldown has begun, first to 50 K then to 4 K. Beam commissioning is foreseen from 18 May, with shutdown from August to October and a 37 week physics run from November. Fermilab’s new Main Injector was reported as having achieved six of seven milestones. The last is 2 x 1013 protons/pulse resonant extracted.

The permanent-magnet recycler was completed in the week of the conference. The initial injection into the Tevatron will be followed by a fixed-target run. Proton­antiproton collider Run II is scheduled from February 2000. Its goals are a maximum luminosity of 5 x 1031, integrated luminosity of 2 inverse femtobarns by the end of 2002, and 3 x 1013 120 GeV protons on target every 1.9­2.9 s.

Frascati’s DAFNE phi factory had a circulating beam after the KLOE detector had been rolled in. It must make the beams flat by correcting the coupling caused by the detector solenoid. Before the shutdown for rolling in the detector, it achieved a maximum luminosity of 1031 with 13 bunches in each beam. J M Slater, a physician, spoke about the Loma Linda proton therapy machine. Under a fabrication contract between Loma Linda University and Fermilab, which was signed in 1986, the 250 MeV machine was installed in 1989. By now more than 4000 patients have been treated. The rate is 100 patients per day with 20 min per patient, 16 h a day, five days a week and 98% uptime. The cost was $125 million, but replicas could be built for half of that amount.

Slater gave a list of 17 future installations. His examples were mostly prostate cancer and some eye treatment. The operation needs more physicists and engineers, and about the same number of nurses and medical technicians, as other forms of treatment.

The conference session on linear colliders opened with a tribute to the late Bjoern Wiik and his work.

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