A FREE ELECTRON LASER X-RAY SOURCE: DESCRIPTION AND SCIENCE. A. Bienenstock, Stanford Synchrotron Radiation Laboratory, Stanford Linear Accelerator Center, Stanford, CA 94305, USA.

SSRL/SLAC is proposing the development of an X-ray source which would provide 150 fsec pulses of 1.5 Å, fully transversely coherent, radiation with peak brightness ~10⁹ times, and time-averaged brightness ~10² times, 3rd generation synchrotron radiation sources. The Linear Coherent Light Source (LCLS) would operate on the principle of the free electron laser (FEL). but lasing would be achieved in a single pass of electrons accelerated to high energy (~15 GeV) by the SLAC linear accelerator. Since it does not employ the optical cavity resonator that is normally used in multi-pass, longer wavelength FELs, this approach is extendible to wavelengths below the region in which reflectors can be used to make such a cavity. Considerable R&D is required to achieve this goal. Since a FEL providing such radiation in the 30-100 Å presently seems feasible with existing technology and is an important step towards the LCLS, we are proposing to construct that first. The LCLS would advance a variety of experiments using coherent X-rays markedly. These include X-ray holography and time correlation (speckle) spectroscopy. Time resolved diffraction would be enhanced considerably, since a diffraction pattern could be obtained in a single 150 fsec pulse, which contains about 5x10¹² photons in a 0.1% bandwidth. The LCLS itself, its radiation properties and some of the experiments which could be performed with it and the 30 Å FEL will be discussed in this talk.