Technical Report: The Status of the Energy Recovery Linac Source of Coherent Hard X-rays at Cornell University

Synchrotron radiation research as a field is still in a growing phase because newer and more capable X-ray sources are presently under development. Advances in storage ring technology, as explained in the Guest Editorial for this special New Source issue by Kwang-Je Kim, is rapidly approaching the point of diminishing returns. It is expected that within a few years storage ring technology will have matured to the point where it will become exceptionally difficult and expensive to make further significant improvements to the X-ray beam quality. In contrast, linac-based sources such as energy recovery linacs (ERLs) and X-ray free electron lasers (XFELs) are at an early stage of development, and provide a clear path for dramatically improving X-ray beam qualities that is likely to continue for many years. ERLs promise to generate bright electron beams, and thus X-rays, with dramatically smaller emittances and pulse durations than those available from storage rings, the present workhorse technology for all existing hard X-ray synchrotron radiation sources. As described in the companion X-ray Free Electron Laser (XFEL) article, new opportunities also exist in a complimentary direction, namely, that of making a lower duty factor X-ray laser that will also generate exciting new science. Though both ERL1 Gruner S. M. and D. H. Bilderback, Energy Recovery Linacs as Synchrotron Light Sources. Nuclear Instrum. & Meth. A 500 25(2003); G. H. Hoffstaetter, I.V. Bazarov, D. Bilderback, M. Billing, S. Gruner, M. Liepe, D. Sagan, C. Sinclair, R. Talman, M. Tigner, ERL Upgrade of an Existing X-ray Facility: CHESS at CESR, Proceedings of EPAC 2004, Lucerne, Switzerland, 497 (2004); Cornell ERL http://erl.chess.cornell.edu/ [Google Scholar] and the XFEL technologies have considerable promise as future Xray sources, much development work and learning in both accelerator and X-ray technology will be required to realize their potential.