  We investigate optomechanical forces on a nearly lossless scatterer, such as
an atom pumped far off-resonance or amicromirror, inside an optical ring
cavity. Our model introduces two additional features to the cavity: an isolator
is used to prevent circulation and resonant enhancement of the pump laser field
and thus to avoid saturation of or damage to the scatterer, and an optical
amplifier is used to enhance the effective $Q$-factor of the counterpropagating
mode and thus to increase the velocity-dependent forces by amplifying the
back-scattered light. We calculate friction forces, momentum diffusion, and
steady-state temperatures to demonstrate the advantages of the proposed setup.
