PAC05 Particle Accelerator Conference, Knoxville, Tennessee, USA, May 16-20, 2005 World Year of Physics 2005
"Imagination is more important than knowledge. Knowledge is limited. Imagination encircles the world." A. Einstein


The 2005 Particle Accelerator Conference, PAC05, took place on May 16-20 at the Knoxville Convention Center in Knoxville, Tennessee. The conference was jointly hosted by the Oak Ridge National Laboratory Spallation Neutron Source (SNS)—the largest accelerator construction project in the United States—and Thomas Jefferson National Accelerator Facility (JLab), Newport News, Virginia. The conference was held under the auspices of the Nuclear and Plasma Sciences Society of the Institute of Electrical and Electronics Engineers and the American Physical Society Division of Physics of Beams (DPB). The Program Committee was chaired by Swapan Chattopadhyay (JLab) and was cochaired by Gerry Dugan ( Cornell University), who also served as the DPB representative. The Local Organizing Committee was chaired by Stuart Henderson (SNS), with Kathy Rosenbalm (SNS) serving as conference coordinator. As usual, the conference covered new developments in all aspects of the science, technology, and use of particle accelerators. Unique to PAC05, however, was the special conference theme of the World Year of Physics. The United Nations declared 2005 the World Year of Physics in honor of the 100th anniversary of Albert Einstein’s “miraculous year,” when he published his three papers on light quanta, Brownian motion, and the special theory of relativity—discoveries that had, and continue to have, a remarkable impact on science.

With its exciting program, the conference attracted more than 1,400 accelerator specialists, making the event the second largest PAC ever. Geographically, 59% of the attendees were from the United States, 25% from Europe, 15% from Asia, and 1% from the Middle East, South America, and as far away as Australia. More than 1,400 papers where processed during the conference and are published on the Joint Accelerator Conferences Web Site (

Accelerators Present and Future

Phil Bredesen, governor of the state of Tennessee, was first to welcome delegates to the conference. A physicist with some background in accelerators from his student years before going on to pursue other interests, the governor talked about the importance of science as a driver of economy and wealth, as well as the importance of continuously supporting education. His address to PAC05 can be found at The governor was followed by Cecilia Jarlskog from Lund, whose colorful presentation included information about Einstein, the Nobel Prize, and accelerators. Barry Barish, chair of the International Technology Recommendation Panel for the proposed International Linear Collider (ILC), then explained the technology choice made last year for the machine (CERN Courier, October 2004, p. 5) and explained his role as the new director of the ILC Global Design Effort to design the accelerator while involving all regions of the world.

The Monday morning plenary session also included highlights from other accelerators, such as the luminosity records of the Tevatron at Fermilab, achieving more than 1 x 1032 cm-2 sec-1; the outstanding performance of Brookhaven National Laboratory’s (BNL’s) Relativistic Heavy Ion Collider, with its polarized beams; and the race between the B-Factories [KEKB in Japan and PEP II at Stanford Linear Accelerator Center (SLAC) in the United States]. The closing plenary session on Friday afternoon included talks on nuclear physics topics such as the Rare Isotope Accelerator proposed in the United States and the Facility of Antiproton and Ion Research project at GSI, as well as accelerator-based materials science research and neutrino and high-energy physics. The talks focused on projects that have paved the way to future accelerators that need to be built to address today’s pressing questions in all areas of science, and they demonstrated yet again how accelerators have become crucial research tools during the past 50 years.

Synchrotron light sources of all sizes and flavors once again dominated the papers presented, demonstrating the high pace at which this field is still growing, especially in the area of energy recovery linacs and short-pulse coherent light sources—that is, X-ray free-electron lasers (FELs)—including the use of self-amplification of spontaneous emission (SASE). Sixteen oral presentations and more than 100 papers were presented on these facilities alone. Vibrant research and planning for new projects are ongoing, with the Linac Coherent Light Source under construction at SLAC and the Euro FEL moving from planning to construction at DESY, as well as the Spring-8 Compact SASE Source in Japan.

World Year of Physics

Einstein was ever present throughout PAC05, as the conference celebrated the World Year of Physics, first with the conference web site, which incorporated an Einstein quotation on every page, and also with several special activities during the week. These events began with a violin and piano concert by Jack Liebeck and Inon Barnatan on Tuesday evening. Introduced by Brian Foster ( University of Oxford), the evening was a tribute to Einstein’s love of the violin (CERN Courier, January/February 2005, p. 41). On Wednesday afternoon, the U.S., Asian, and European Particle Accelerator Conference series joined forces in offering a special session, Einstein and the World Year of Physics, organized by Swapan Chattopadhyay (JLab). The session was chaired by Bill Madia (Battelle) and included four presentations relating present-day research to Einstein’s legacy. Presentations were made by Michael Turner from the National Science Foundation, Makoto Kobayashi of KEK, Yoichiro Suzuki of Tokyo, and Carlo Rubbia from CERN.

To draw the public’s attention to the World Year of Physics, an Einstein in the City festival followed that evening. Organized together with the City of Knoxville, the festival drew conference participants and several hundred additional people to the World’s Fair Park, outside the convention center. Part of the festival was a science fair for local high school students, with cash prizes between $200 and $5000 awarded to projects judged to be the best by a select team of conference participants. A special panel of four physicists, moderated by Bill Madia, answered science-related questions from the public for about an hour. Questions covered everything from “Why is science useful?” to “How many stars are in the universe?” to “What does an accelerator do?”. Other activities included an appearance by “Einstein the Bird,” a talking parrot from the local zoo, bluegrass music from a local band, as well as plenty of good food and drink.

Further Highlights

Another highlight of the conference was the prize session, which has become customary for PAC, where winners of several accelerator prizes are recognized and have the opportunity to report on their research. The session chair, Nan Phinney (SLAC), congratulated recipients individually and presented some of the awards. Among them was Keith Symon ( University of Wisconsin), winner of the American Physical Society’s prestigious Robert R. Wilson Prize “for fundamental contributions to accelerator science including the FFAG concept and the invention of the RF phase manipulation technique that was essential to the success of the ISR and all subsequent hadron colliders.” The other American Physical Society prize was for an outstanding doctoral thesis for Eduard Pozdeyev from JLab, who performed his doctoral work at Michigan State University. Ron Davidson ( Princeton University) and Tom Roser (BNL) were awarded the Institute of Electrical and Electronics Engineers Nuclear and Plasma Sciences Society Particle Accelerator Science and Technology Award (CERN Courier, June 2005, p. 39). Wim Leemans (Lawrence Berkeley National Laboratory) and Anton Piwinski (DESY) were presented with the U.S. Particle Accelerator School Prize for Achievement in Accelerator Physics and Technology.

Although PAC05 ended officially on Friday afternoon, about 400 participants extended their stay by one more day to visit the SNS site in Oak Ridge. SNS is in its last year before the first beam is scheduled to hit the mercury target and the first neutrons will be channeled to instruments. So far, beam has been commissioned to the end of the normal conducting linac, up to 157 MeV, and soon the superconducting linac will be turned on to boost the energy to 1 GeV. Later this year the compressor ring will be commissioned in preparation for user operation, to begin next summer. Tour participants were therefore among the last people to get a glimpse of what has been going on at the site over the past five years before much of the facility will be closed to visitors.

Norbert Holtkamp, PAC05 Chair