New Facilities, FELS, Accelerator Applications Highlight PAC 97
Andrew Sessler (left) being presented the APS Wilson prize by John Peoples.
Lynda Williams, the Physics Chanteuse, gives the PAC banquet attendees an easy way to remember Maxwell's equations.
Opening Plenary Session
The opening plenary session on Monday morning focused on the current status of various projects deemed vital to the future of particle physics, including the second operational run of the LEP collider at CERN and the first commissioning of the super photon ring-8GeV in Japan, a third-generation synchrotron radiation source for X-rays. In addition, C. Joshi of UCLA reported on the proposed use of lasers to accelerate particles to high energies in short acceleration lengths, using the very high electric fields associated with laser beams. Speakers at a Monday afternoon session provided status reports on upgrades to Fermilab's Main Injector and Recycler, construction of Brookhaven's Relativistic Heavy Ion Collider, and the Large Hadron Collider project scheduled for completion at CERN by 2005.
Free Electron Lasers
Free electron laser (FEL) research has proceeded during the last 25 years from marginal proof of principle experiments to the construction and operation of user-oriented devices. Among the major milestones are the first experimental results from the FEL facility at the Thomas Jefferson National Accelerator Facility, as well as the development of user facility at Duke University to explore the capability and application of high power, synchronized multiwavelength infrared, ultraviolet, and gamma ray FEL light sources.
John Madey of Duke University believes the size, cost, and capabilities of such facilities are well-suited to the resources and interests of multi-disciplinary research universities.
The TESLA FEL at DESY in Germany makes use of the high quality electron beam that can be provided by the superconducting linac to drive a single-pass FEL at wavelengths far below the visible region. In order to reach wavelengths of 6 nanometers, the TESLA Test Facility currently under construction is being extended to 1 GeV beam energy, using the principle of self-amplified spontaneous emission. According to DESY's Jorge Rossbach, the key prerequisite for such single-pass, high-gain FELs is a high intensity, diffraction limited electron beam to be generated and accelerated without degradation. Once proven in the micrometer to nanometer regime, this scheme should be applicable down to Angstrom wavelengths.
The study of the Inverse Free Electron Laser (IFEL) as a potential mode of electron acceleration has been pursued at Brookhaven National Laboratory for a number of years, according to Arie van Steenbergen. The studies focus on the development of a low energy, high gradient multistage linear accelerato. The BNL team recently completed a successful proof-of-principle experiment with a single module accelerator unit.
Historically, particle accelerators were developed initially for nuclear, then for particle physics research, eventually resulting in accelerator applications in medicine and industry. This includes the production of radio-isotopes for medical diagnostics and the production of electrons, protons or fast neutron beams for cancer therapy. According to Y. Jongen of Ion Beam Applications, research-oriented accelerators tend to be complex and expensive. In contrast, most accelerator applications are done with low to moderate energy protons or electrons, but with large average beam power, and tend to be simple and inexpensive to operate.
TRIUMF and Northrup Grumman have developed a new system for the detection of explosives and drugs, called the Contraband Detection System (CDS), based on the resonant absorption of gamma rays by nitrogen-14. According to TRIUMF's Bruce Milton, the collaboration has produced 3D images of the nitrogen regions which may be used to determine if small amounts of nitrogen-based explosives, heroin, or cocaine are present in scanned containers.
Bernhard Ludewigt of Lawrence Berkeley National Laboratory reported that accelerator-driven epithermal neutron sources are becoming an attractive alternative to nuclear reactors for Boron Neutron Capture Therapy (BNCT), designed to deliver a localized dose to tumors.
Closing Plenary Session
The focus was on the future of high energy and nuclear physics at Friday afternoon's closing plenary session, which included an overview of the recommendations of the 1996 Long Range Plan for nuclear science developed by the DOE/NSF Nuclear Science Advisory Committee. Brookhaven's W.T. Weng, who is chair of the next PAC meeting, CAP '99 in New York City, reported that the three to four orders of magnitude increase in both peak intensity and average flux gained in the last thirty years have made it possible to construct high intensity proton accelerators. Herman Winick of SLAC said that concepts and designs being developed for fourth-generation light sources that will increase the brightness and coherence of the radiation using storage rings.