UW-Madison receives grant for superconducting electron gun

The University of Wisconsin–Madison has received a $4.5 million grant from the United States Department of Energy Basic Energy Sciences office. The award will fund a research and development project focusing on the fabrication and testing of what is called an electron gun for a free electron laser (FEL) — a several-football-fields-long light source, an immense instrument whose light would be used by researchers across a range of disciplines for their experiments.

The electron gun project will greatly enhance a UW–Madison initiative to build an FEL. This initiative, called WiFEL, or the Wisconsin Free Electron Laser, would be the brightest source of ultraviolet and soft X-rays in the world.

“Major advances in accelerator and laser technology have created this opportunity to construct a national light source facility based on free electron lasers. Here at UW–Madison, our team is pushing forward with development work as part of a new American FEL, hopefully to be located here. This award from DOE is a major first step toward WiFEL,” explains Joe Bisognano, director of the UW–Madison Synchrotron Radiation Center (SRC) and principal investigator on the project.

Since 1987, SRC has housed an electron storage ring, called Aladdin, which produces light by whirling electrons at nearly the speed of light around a circular track. Researchers use this light for a wide array of applications. A storage ring is just one of many ways to produce light. A free electron laser makes a laser beam of radiation that can produce super-short pulses of light measured in quadrillionths of a second. It all starts at the beginning of the machine at what’s known as the electron gun, and this is the focus of the current project — a research and development project to produce the best electron gun.

“An electron gun is actually a vacuum tube for producing a stream of electrons as is found in all older tube TVs,” explains electrical engineer Bob Legg, who spearheaded the design of this cutting-edge electron source. “The successful production of the photons by the FEL mechanism critically depends on the quality of the electron beam. 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.”

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 light source will enable advances in disease research, biofuels, solar cells, nanotechnology and more.

“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 Bisognano, who is also a professor of engineering physics in the UW–Madison College of Engineering. “With the FEL light sources, 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 it’s time for us at Wisconsin to be part of the adventure.”