Faster Tracks for Particle Accelerators Promoted by ODU Physicists
Promising research at Old Dominion University aimed at improving the efficiency of particle accelerators has resulted in an investment of nearly $600,000 by the U.S. Department of Energy (DOE) in a project headed by Leposava Vuskovic, Eminent Scholar and professor of physics.
The award was hailed by ODU administrators as evidence of the innovative work being done by the Center for Accelerator Science (CAS), which was launched three years ago by the university and the Thomas Jefferson National Accelerator Facility in Newport News. The Jefferson Lab falls under the purview of DOE.
Vuskovic, an experimental atomic physicist, is the prinicipal investigator for the three-year grant, which is titled "Plasma Processing of Superconducting Radio Frequency (SRF) Cavities for the Next Generation of Particle Accelerators." The research team includes two other ODU physicists, Alexander Godunov, associate professor, and Svetozar Popovic, research professor, as well as two researchers from Jefferson Lab, Larry Phillips and Anne-Marie Valente-Feliciano.
Their innovations include new and safer ways to keep tabs on and eliminate "bumps in the road" that can impede an accelerator's efficiency. In addition to its potential to improve existing accelerator technology, the work is expected to make it easier for scientists and engineers to design the next generation of accelerators.
"This is an important grant for ODU and the Center for Accelerator Science," said Chris Platsoucas, dean of the ODU College of Sciences. "I am extremely proud of Professor Vuskovic and her colleagues."
Vuskovic said the CAS "is already creating a vigorous research atmosphere," and added, "Everybody, Jefferson Lab, ODU and the wider particle accelerator community, likes it. This grant is the tip of the iceberg of the work to be done in development of technologies for construction and maintenance of next-generation accelerators. We expect a large amount of work to follow this grant."
The mile-long electron accelerator at Jefferson Lab is an example of the large colliders that are employed around the world to explore the fundamental nature of matter. But accelerators are also powerful sources of laser light and are becoming more and more useful in medical diagnostics, such as in the imaging of biological tissues or beam therapies to fight cancer. There are other emerging applications, as well, ranging from ion beam accelerators that can create semiconductor chips to advanced scanners that allow homeland security agents to monitor the contents of shipping containers.
In fact, the research and development focus in accelerator physics is on a new generation of relatively small accelerators that can power particles up to near the speed of light.
This acceleration of particles in advanced accelerators is typically done by SRF cavities. In large colliders, hundreds of them are connected end to end, each giving a slingshot-like boost to the electrons or other particles that are being accelerated. That boost comes from a cavity's ability to harness radio-frequency energy.
Most of these cavities are made from niobium, a sturdy metal that can withstand the energy involved. To reach the superconducting state, the vacuum cavities operate at about minus-450 degrees Fahrenheit, thanks to a liquid helium bath. The cold reduces electrical resistance to almost zero.
Still, energy can be subtracted from the particle beam by rough spots and other surface imperfections that develop on the cavity walls. These are the so-called bumps in the road.
Great care is taken to provide mirror-like, polished surfaces within new cavities, and great care is also needed to keep the surfaces in original condition. The surface-modification processes currently used involve wet etching technologies, and these often require powerful chemicals that are an environmental hazard.
Vuskovic and her colleagues have shown in initial tests that they can use plasma, the same kind of supercharged gas that lights up a television screen or a fluorescent bulb, to accomplish the processing. In this case, the plasma is a supercharged chlorine gas that the CAS tests have shown will etch the surfaces at about the same rate as the wet processes. The plasma process also is cheaper and results in no environmentally hazardous wet residue.
Just as importantly, the plasma processing used by the researchers seems to surmount uniform coverage problems encountered in wet etching, and is likely to be better suited to newfangled designs proposed for cavities in next-generation accelerators.
In arriving at ways to assess the results of their initial research, the ODU-Jefferson Lab team also laid the foundation for a plasma emission spectroscopy system that performs cavity surface diagnostics and enables the researchers to know which plasma parameter is best for each cavity job. Eventually, they hope to evolve these findings into the design and construction of a prototype plasma-processing apparatus for multiple cavity cells.
Vuskovic noted the interdisciplinary strength of the research team. Godunov is an expert in the modeling and simulation of plasma and Popovic is known internationally for his work in plasma physics. Also involved in the work is Filip Cuckov, a visiting assistant professor in electrical and computer engineering at ODU, who is a robotics expert able to help with cavity-processing diagnostics.
Phillips and Valente-Feliciano are well-known accelerator physicists who are affiliated with the Jefferson Lab's SRF Institute, which is devoted to the development of next-generation accelerators and light sources.
Vuskovic is known for her innovative thinking as an atomic physicist. She was elected a Fellow of the American Physical Society in 2002 "for important and sustained work on electron collisions with ground state and excited atoms by creating a number of remarkable experimental techniques." Before joining ODU in 1993, she directed the Atomic, Laser and High Energy Physics Division of the Institute of Physics at the University of Belgrade and served on the faculty of New York University.
The CAS is directed by Jean Delayen, who last year was awarded the United States Particle Accelerator School (USPAS) Prize for Achievement in Accelerator Physics. The ODU professor of physics was cited by USPAS "for conceiving and developing a variety of superconducting accelerating structures and for his work with young scientists in USPAS and elsewhere."
Delayen, who has several accelerator inventions to his credit, has major research support from DOE and has taken a leading role in the development of the next-generation accelerators.
The door has opened recently to a broad array of particle accelerator uses, which are described in detail in the DOE report "Accelerators for America's Future," released in 2010. "A beam of the right particles with the right energy at the right intensity can shrink a tumor, produce cleaner energy, spot suspicious cargo, make a better radial tire, clean up dirty drinking water, map a protein, study a nuclear explosion, design a new drug, make a heat-resistant automotive cable, diagnose a disease, reduce nuclear waste, detect an art forgery, implant ions in a semiconductor, prospect for oil, date an archaeological find, package a Thanksgiving turkey or discover the secrets of the universe," the report states.