  Accelerator-based searches for dark matter are aiming for high sensitivity
and need an experimental setup with high luminosity. This field of research is
often called intensity frontier physics. One of the best motivated portals of
interaction between dark matter and ordinary matter is a dark photon which
could be observed as a resonance in the invariant mass of the decay products.
Electron-positron collisions are known to be the cleanest interaction for such
a study. In this paper we propose a scheme for a collider which allows for a
luminosity of a few orders of magnitude higher than could be obtained in a
conventional symmetric collider and with a few times higher accessible mass
than is possible using a positron beam and a fixed target approach. The key
concept is based on asymmetric energies: a high-energy circulating positron
beam and a low-energy high-intensity electron beam, and optimization of the
beam interaction region. We present here a configuration of a collision region
of 10 MeV electron and 4 GeV positron beams.
