In recent years, the study of materials using terahertz radiation—light that falls between the infrared and microwave energy ranges—has brought significant scientific advances in solid state physics and chemistry. Applications as diverse as semiconductor and high-temperature superconductor characterization, tomographic imaging, label-free genetic analysis, cellular level imaging, and chemical and biological sensing have thrust terahertz research from relative obscurity into the limelight. Near-lightspeed electron bunches, compressed to 100's of femtoseconds in duration, are the most intense sources of terahertz radiation known today. Conventional laboratory sources are typically limited to peak electric fields of the order of 1 MV/meter. In contrast, the fields surrounding these compressed near-lightspeed electron beams exceed 1 GV/meter. Such field strengths rival those experienced by valence electrons in materials (about 1 V over the size of an atom) and their application can therefore create new states of matter previously not observable.
FACET offers unique possibilities to undertake cutting edge research with terahertz radiation. In addition to the unique capability they provide for accelerator research and development, FACET's high-quality beams will generate high-intensity electric and magnetic fields. These fields, in fact, closely resemble half-cycle terahertz electromagnetic waves, but are orders of magnitude stronger than those created by laboratory tabletop sources. Such an intense source will open many new opportunities across a variety of solid state physics experiments. A terahertz fields may act like a DC field on the electron cloud of an atom, and may thus distort the atomic electron cloud and even cause atomic motions, which might be used to initiate chemical reactions. For these reasons, FACET beams will provide unique and exciting opportunities for new advances, with the most intense sources of terahertz radiation known today.