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  • University of Wisconsin—Madison Awarded $4.5 million Department of Energy Grant for Fabrication and Testing of a Superconducting Electron Gun for Next Generation Light Source

    September 21, 2010

    UW Madison today took a major step in contributing to the future of American light sources with a grant awarded by the U.S. Department of Energy Basic Energy Sciences that will fund a research and development project focusing on the fabrication and testing of a superconducting electron gun for what is known as a “free electron laser”—a several football fields-long light source whose light would be used by researchers across a range of disciplines for their experiments. The total award for this project is $4.5-million over the next three years.

    Since 1987 UW Madison’s Synchrotron Radiation Center has housed an electron storage ring, called Aladdin, which produces light by whirling electrons at nearly the speed of light around a circular track. But a storage ring is just one of many ways to produce light and has limitations. In a free electron laser (FEL), an electron beam is sent through a long array of magnets (an undulator) that causes the beam to jiggle and emit light. If the electrons are close enough they will produce light in unison and make a laser beam of radiation. The resulting radiation can produce super-short pulses of light measured in quadrillionths of a second (femtoseconds), and it’s this light that will enable researchers to explore scientific problems that, until now, were impossible to pursue.

    “Synchrotron light sources such as Aladdin were the centerpieces of light-based research in the latter part of the 20th century. They explored much science—the science of how things are, but not how they got that way,” explains Joe Bisognano, director of the Synchrotron Radiation Center and principal investigator on this new project. “With the FEL lightsources, we'll be able to watch processes happen at the chemical level, at a size of a handful of molecules. FELs are the sources of the 21st century, and its time for us at Wisconsin to be part of the adventure.”

    “An electron gun is actually a vacuum tube for producing a stream of electrons as is found in all older tube TVs,” explains the electrical engineer, Bob Legg, who spearheaded the design of this cutting edge electron source. The difference between a TV and this electron gun is how the electrons exit the gun. A TV uses high voltage (up to 35,000 volts) to shoot the electrons out, while the proposed gun uses a tuned radio frequency (rf) field, like a TV transmitter, to shoot the electrons out. It can go to 4,000,000 volts with even higher peak values. This new electron gun will provide unprecedented performance because it is based on the superconductivity of the metal niobium at liquid helium temperature.

    “The successful production of the photons by the FEL mechanism critically depends on the quality of the electron beam,” Legg continues. “Higher energy electrons can be used to compensate for poorer quality electrons, but requires ever larger particle accelerators, whose cost is measured in hundreds of millions of dollars.  This is the issue our gun will address. In a well-designed machine, it determines the quality of the electrons at the end and can have a huge effect on the overall cost of the machine. That's one reason the gun is so important to the overall FEL design.”

    So, if you have ever wondered what enabled big steps in science and medicine, or even what is preventing solutions from being found for pressing problems, it undoubtedly comes down to limitations or advances in the tools available to pursue the science that might provide the answers. The science that is foreseen possible with a free electron laser spans many disciplines including atomic physics, condensed matter physics and materials sciences, femtochemistry, biology, and various fields of engineering. Such a lightsource will enable advances in disease research, biofuels, solar cells, nanotechnology and more.

    “In the latter part of the 20th century Wisconsin led the way in using synchrotron based light for scientific research.  It's time for Wisconsin to lead the way again, this time with free electron lasers,” encourages Bisognano.  

    Indeed, UW Madison is moving enthusiastically toward securing funding to enable this goal. Related to this current project, SRC also recently learned from NSF that the Division of Materials Research (DMR) approved a supplemental funding proposal, which ensures SRC continued operational funding through April 2011. Secondly, SRC also submitted to NSF a proposal for long-term, multiple-year funding, including extended operations of the Aladdin ring. Finally, SRC submitted to NSF in June an IMR-MIP (Instrumentation for Materials Research—Major Instrumentation Projects) proposal for a comprehensive research and development project for a free electron laser.

    Synchrotron Radiation Center, University of Wisconsin—Madison