  A conceptual design is presented of a novel ERL facility for the development
and application of the energy recovery technique to linear electron
accelerators in the multi-turn, large current and large energy regime. The main
characteristics of the powerful energy recovery linac experiment facility
(PERLE) are derived from the design of the Large Hadron electron Collider, an
electron beam upgrade under study for the LHC, for which it would be the key
demonstrator. PERLE is thus projected as a facility to investigate efficient,
high current (> 10 mA) ERL operation with three re-circulation passages through
newly designed SCRF cavities, at 801.58 MHz frequency, and following
deceleration over another three re-circulations. In its fully equipped
configuration, PERLE provides an electron beam of approximately 1 GeV energy. A
physics programme possibly associated with PERLE is sketched, consisting of
high precision elastic electron-proton scattering experiments, as well as
photo-nuclear reactions of unprecedented intensities with up to 30 MeV photon
beam energy as may be obtained using Fabry-Perot cavities. The facility has
further applications as a general technology test bed that can investigate and
validate novel superconducting magnets (beam induced quench tests) and
superconducting RF structures (structure tests with high current beams, beam
loading and transients). Besides a chapter on operation aspects, the report
contains detailed considerations on the choices for the SCRF structure, optics
and lattice design, solutions for arc magnets, source and injector and on
further essential components. A suitable configuration derived from the here
presented design concept may next be moved forward to a technical design and
possibly be built by an international collaboration which is being established.
