Status of A Plan for an ERL Extension to CESR

We describe the status of plans to build an Energy-Recovery Linac (ERL) X-ray facility at Cornell University. This 5 GeV ERL is an upgrade of the CESR ring that currently powers the Cornell High Energy Synchrotron Source (CHESS) [1]. Due to its very small electron-beam emittances, it would dramatically improve the capabilities of the light source and result in X-ray beams orders of magnitude better than any existing storage-ring light source. The emittances are based upon simulations for currents that are competitive with ring-based sources [2, 4]. The ERL design that is presented has to allow for non-destructive trans port of these small emittances. The design includes a series of X-ray beamlines for specific areas of research. As an upgrade of the existing storage ring, special attention is given to reuse of many of the existing ring components. Bunch compression, tolerances for emittance growth, simulations of the beam-breakup instability and methods of increasing its threshold current are mentioned. This planned upgrade illustrates how other existing storage rings could be upgraded as ERL light sources with vastly improved beam qualities.