Jefferson Lab free-electron laser upgrade could induce completely new phenomena in materials

What questions will it answer; what opportunities will it offer?

History doesn’t record the moment when fully conscious humans asked the first question. The incessant push of human curiosity has nevertheless changed the world. Even so, despite the seemingly inexorable march of science and technology into the current century, questions don’t seem in short supply. Gwyn Williams, basic research program manager for Jefferson Lab’s Free-Electron Laser (FEL), suspects some important answers may be forthcoming as a result of the FEL upgrade currently underway.

“The FEL is such a powerful light source that it induces completely new phenomena in materials,” Williams says. “All kinds of unexpected properties emerge. Creating carbon nanotubes [for electronics and super-strong structures] comes as a result of exciting graphite, for instance. This upgrade gives us a window with a whole new view. We’re beginning to truly understand how the world works at the level of a single atom.”

Should such an enhanced understanding emerge, scientists and engineers could custom-design materials atom by atom. This prospect, embraced by those in the field known as nanotechnology, could begin a large-scale products revolution unprecedented in human history. First, however, researchers must significantly deepen their understanding of the submicroscopic. Williams points out that because of its power and precision, FEL light can help do just that, illuminating these smallest of realms: a kind of ultra-fast camera that will freeze-frame even the most complex physical or chemical reactions.

With the exception of density, a property of matter constrained and described by the nucleus within atoms, the physical properties of all materials are primarily determined by the way electrons act. Everyday technology, from lamps to laptops, is controlled by the behavior and flow of electrons, and is manifested in such properties as hardness, conductivity and materials-energy flow. Observing specific electron behavior, however, is difficult. Scientists who conduct such observations need an intense light source — and now have one, in the form of the FEL.

FEL research falls into three broad categories: photo-induced chemistry, biology and materials. Before beginning the upgrade, some 20 formal proposals had been made for FEL-focused research. Seventeen of these proposals were given FEL beam time before the FEL shutdown in November. These will be prioritized and will carry forward once the upgrade is complete.

Among the areas under investigation will be the function of protein molecules within human cells as well as the mechanisms that determine and degrade materials purity, such as the silicon that comprises many computer components. Scientists will also study the effects of new surface compounds, produced when metals bathed in nitrogen are exposed to FEL light, and explore novel areas such as “spintronics,” which concerns the properties of next generation semiconductor designs that optimize performance using newly discovered properties of electrons.

The addition of ultraviolet-light (UV) capability will further augment the FEL’s utility by enabling experiments that assess the nature and extent of the human health risk arising from increased ultraviolet light. Further, because of the nature of its construction and operation, the FEL accelerator’s electron beam can produce light with a frequency in the range of thousands of trillions of cycles per second. This “terahertz” capacity could conceivably lead to imagers that could quickly detect biological agents, such as anthrax, and hunt for concealed land mines.

“As scientists and as people, we want to improve the quality of life,” Williams says. “This machine, already the most powerful in the world, is getting even better. It should enable us to make important progress in the next several years.”

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