  Project-X is a leading candidate of the next major accelerator construction
project at Fermilab. The mission need of Project-X is to establish an intensity
frontier for particle physics research, or more precisely, to build a multi-MW
proton source for neutrino and other particle studies. Coupled with an upgraded
Main Injector (MI) and Recycler, an 8 GeV superconducting RF (SRF) H-minus
linac meets this need [1]. However, a more cost effective approach would be a
hybrid design, namely, a combination of a 2 GeV SRF linac and an 8 GeV rapid
cycling synchrotron (RCS) in lieu of an 8 GeV SRF linac. This alternative
design also meets the mission need but at a lower cost since a synchrotron is
cheaper than a SRF linac. It retains the ability to use a 2 GeV SRF linac for
ILC technology development. It reuses the existing Debuncher enclosure and
Booster RF. The transport line of 2 GeV H-minus particles is shorter than the
present 8 GeV design since stronger bending magnets can be used. The blackbody
radiation stripping of H-minus particles will no longer be a problem and the
requirement of a cryogenic beam screen can be eliminated. The efficiency of
stripping foil is higher and injection loss (kJ) will be reduced by a factor of
4. This paper introduces this alternative design and describes briefly the
major components in the design.
