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BEAMS, ACCELERATORS, AND COHERENT RADIATION SOURCES 98 glass lasers promises a high-average-power x-ray laser alternative to synchrotron sources at substantially reduced costs. Sources are envisioned with wavelengths between 100 and 150 Ã and bandwidths of 5 Ã 10-5, producing 1015 photons per pulse at 1 Hz, that will occupy physical footprints approximately 3 m by 6 m. X-ray laser researchers aim at achieving shorter and shorter wavelengths and high coherent output energy. Exploiting ultrashort, subpicosecond laser pulses, photoionization pumping schemes render plausible lasing at or near 14 Ã within 5 to 10 years. Harmonically generated x-rays from ultrashort-pulse laser-gas jet interactions are striving to achieve high efficiency at short wavelengths to go along with their inherent tunability and coherence. In turn, these sources can be envisioned to serve as drivers for further wavelengths down-conversion providing improved radiation sources in the spectral regime of the order of tens of keV, which would significantly broaden potential medical and industrial applications. The features of high power, narrow bandwidth, short pulse, and coherence make x-ray lasers attractive for future applications, such as biological microimaging, photoelectron spectroscopy, and probing of dense plasmas. (See Plate 4.) Given these scientific successes and potential applications and societal benefits, it is a serious deficiency that no federal agency has taken on the mandate to support x-ray laser research. Advances in this area are hampered by the presence of large capital- intensive synchrotron and inertial confinement fusion facilities that historically have either siphoned off the majority of potential funding support or programmatically relegated the research to a piggyback status. The multidisciplinary nature of the research complicates the effort to accrue the critical mass of funding that would support a robust program. CONCLUSIONS AND RECOMMENDATIONS Research and development on particle beams, accelerators, and coherent radiation sources offers a wide range of opportunities for technological advances of importance for our society. Examples include food sterilization; waste treatment; welding and materials processing; advanced accelerator development; and the development of new, intense radiation sources for a wide range of applications. In the past, much of the basic science and development in this area was driven by military applications. However, given recent changes in emphasis on military needs, there is a danger that opportunities will be lost unless research and development continue to be pursued in areas in which there are significant technological opportunities. As discussed elsewhere in this report, there is a general need for support for small-scale basic research. This also is true in the areas of beams, accelerators, and radiation sources.
BEAMS, ACCELERATORS, AND COHERENT RADIATION SOURCES 99 Given these considerations, the panel recommends the following: 1. Dual-use opportunities of defense-driven technologies should continue to be pursued. 2. Existing hardware and facilities no longer needed for ICF and SDIO applications should be made available for other scientific and technological applications. 3. Support should be given to small-scale basic research in these areas. 4. Particular attention should be given to the development of advanced concepts of particle accelerators and of new, intense radiation sources, such as x-ray lasers. 5. Where practical, the use of large facilities by outside users to pursue the scientific and technological goals described in this section should be encouraged.
