Engineers plan to install a new injector that will produce twice the amount of electron beam than is currently possible. The FEL's upgraded "wiggler" will double the fraction of electron-beam energy converted to laser light. Two additional cryomodules will be added to the FEL linear accelerator line, effectively quadrupling system energy from the current 40 million electron volts, or MeV, to 160 MeV. Laser power will surge at least 10-fold, to 10 kilowatts, and may eventually peak near 20 kilowatts.
When all is said and done, nearly the entire FEL will consist of new or upgraded components. "It's basically 90 percent a new machine," Dylla says. "We're keeping the injector and one cryomodule. But the injector will be substantially modified. And the linac will be enhanced."
Perhaps most importantly, researchers will literally be able to turn a knob in order to select different frequencies of light. This "tunability" is of crucial importance for materials research, but also helps scientists better understand the behavior of particles at the atomic level and below.
"Tunability for exploration is what people want," says Gwyn Williams, FEL basic research program manager. "It's about finding out how materials behave at different wavelengths of light. Because atoms are joined by chemical bonds, they act like springs. Now we can make those springs bounce up and down. In effect, we can hit any note and then watch what happens when we do."
A variety of companies are interested in the FEL's commercial potential. Thus far, FEL proof-of-concept experiments have included investigations of chemical-vapor deposition, a technique used to produce high-quality coatings and thin films for electronics and metals, as well as the effects of FEL processing on nylon, polyester and a class of materials known as polyimides. The Lab's FEL has also been able to create in bulk ultrasmall but very strong structures known as carbon nanotubes, which could eventually be the heart of minuscule next-generation computers, as well as structural components for aircraft and automobiles. The FEL can also be used to change the surface properties of food packaging, making it more resistant to microbes and food spoilage.
Another key enhancement will be the addition of an ultraviolet "sidetrack": a portion that will be capable of producing UV light for experiments. When complete, the sidetrack will enable the production of one kilowatt of UV light — 1,000 times the capability of the one-watt devices commonly in use at other laboratories.
The bulk of the FEL upgrade funding is coming from the U.S. Navy — $13.5 million — and the U.S. Air Force — $4.9 million. Additional monies have been provided by the state of Virginia and NASA. Once fully operational, the FEL is expected to be supported by research grants from the federal and state governments and by projects commissioned by industrial interests.