  Application of electron cooling at ion energies above a few GeV has been
limited due to reduction of electron cooling efficiency with energy and
difficulty in producing and accelerating a high-current high-quality electron
beam. A high-current storage-ring electron cooler offers a solution to both of
these problems by maintaining high cooling beam quality through
naturally-occurring synchrotron radiation damping of the electron beam.
However, the range of ion energies where storage-ring electron cooling can be
used has been limited by low electron beam damping rates at low ion energies
and high equilibrium electron energy spread at high ion energies. This paper
reports a development of a storage ring based cooler consisting of two sections
with significantly different energies: the cooling and damping sections. The
electron energy and other parameters in the cooling section are adjusted for
optimum cooling of a stored ion beam. The beam parameters in the damping
section are adjusted for optimum damping of the electron beam. The necessary
energy difference is provided by an energy recovering SRF structure. A
prototype linear optics of such storage-ring cooler and initial tracking
simulations are presented and some potential issues such as coherent
synchrotron radiation and beam break up are discussed.
