This paper describes the concept of a primary electron beam facility at CERN,
to be used for dark gauge force and light dark matter searches. The electron
beam is produced in three stages: A Linac accelerates electrons from a
photo-cathode up to 3.5 GeV. This beam is injected into the Super Proton
Synchrotron, SPS, and accelerated up to a maximum energy of 16 GeV. Finally,
the accelerated beam is slowly extracted to an experiment, possibly followed by
a fast dump of the remaining electrons to another beamline. The beam parameters
are optimized using the requirements of the Light Dark Matter eXperiment (LDMX)
as benchmark.Comment: 3 pages, 3 figure