We present a proposal for a future light dark matter search experiment at the Electron Stretcher
Accelerator ELSA in Bonn: Lohengrin. It employs the fixed-target missing momentum based
technique for searching for dark-sector particles. The Lohengrin experiment uses a beam of
electrons that is extracted from the ELSA accelerator and shot onto a thin target to produce mainly
Standard Model bremsstrahlung and possibly new particles coupling feebly to the electron. A well
motivated candidate for such a new particle is the dark photon. The dark photon is a new, possibly
massive gauge boson arising from a new gauge interaction in a dark sector and mixing kinetically
with the Standard Model photon. The Lohengrin experiment is estimated to reach sensitivity to
couplings small enough to explain the relic abundance of dark matter in various models for dark
photon masses between ∼1 MeV and ∼100 MeV.