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November 16, 2001 | |
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Reaching
farther into the infrared |
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At a recent meeting of users of the Advanced Light Source, a workshop organized by Michael Martin and Wayne McKinney of infrared beamline 1.4 focused attention on current research and future prospects for infrared science at the ALS. Out of the discussion came a raft of ideas for a brand new infrared ring to be constructed under the ALS dome. "The current IR beamline is great for near-infrared microscopy and spectroscopy," says Martin, "but because the ALS was originally built for extreme ultraviolet and soft-x-ray light, it can't do much in the far infrared." For example, longer wavelengths are often eliminated by the geometry of existing beam ports.
A combination of factors suggests that a uniquely capable infrared facility could be built using the shielding structure of the existing booster ring as a foundation. The booster ring shielding is not constructed from blocks of concrete but was continuously poured as a single structure, eliminating many vibration problems. Electrons would be injected into the dedicated IR ring from the existing linac at long intervals, with no overlap or interference with the needs of the main ring. The IR ring would use extremely short bunches of electrons. Synchrotron radiation produced by electron bunches shorter than the wavelength of the radiation itself — in this case, long-wavelength infrared — is coherent, increasing brightness by many orders of magnitude. Extremely short pulses would open new research possibilities, such as observing rapid chemical changes in living cells in real time. Other areas of science that would benefit greatly from a bright far-infrared source and its vast increase in signal over existing lab methods include studies of high-temperature superconductivity, colossal magnetoresistance, and other aspects of the electronic structure of strongly correlated materials. Studies of the feasibility of a dedicated IR ring at the ALS, with 36 ports of which a dozen would be in use at any time, are currently supported by Berkeley Lab's Laboratory Directed Research and Development program. Integrating the new ring with existing facilities promises to make it remarkably economical — and is just one of numerous opportunities for keeping the ALS in the forefront of synchrotron radiation science. Additional information:
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