  The CLIC (Compact Linear Collider) RF power source is based on a new scheme
of electron pulse compression and bunch frequency multiplication using
injection by transverse RF deflectors into an isochronous ring. In this paper,
we describe the modifications needed in the present LEP Pre-Injector (LPI)
complex at CERN in order to perform a low-charge test of the scheme. The design
of the injector (including the new thermionic gun), of the modified linac, of
the matched injection line, and of the isochronous ring lattice, are presented.
The results of preliminary isochronicity measurements made on the present
installation are also discussed.
