CESR Accelerator Upgrade

The CHESS-U upgrade will convert the south arc of the CESR accelerator to a double bend achromat (DBA) lattice that provide straight sections for up to 12 new insertion devices.

CHESS-U will operate at an energy of 6-GeV with a stored beam current of 200 mA to produce x-rays up to high energy (order 100 keV) for in situ and operando studies. The reduction of CESR beam emittance from the present 100 nm-rad at 5 GeV to around 30 nm-rad at 6 GeV achieved with DBA lattice conversion will enable x-ray flux densities into small apertures that are comparable to that from existing undulators at high energy sources.

Operating with a single beam instead of with counter-rotating electron and positron beams will eliminate many of the performance limitations associated with the present 2-beam operation, as well as enable all beam lines to be aligned to a single beam orbit. CHESS-U will begin operation with a positron beam to minimize the upgrade installation dark time, but will then switch to a more easily sourced and reliable electron beam (which will entail changing the polarities of magnet power supplies and modifications to the injection system).

CHESS-U is intended to fill a niche in performance in the light source world where this flux density and the ability to produce flat ribbon beams for various applications, coming with a relatively low cost, will be complementary to the high brightness and coherence being sought by the much more expensive 4th generation storage rings in construction or planning.