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

Abstract

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 and the XFEL2 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.