  The Fermilab Proton Improvement Plan II, or PIP-II, would enable the world's
most intense high-energy neutrino beam and would help scientists search for
rare particle physics processes. The PIP-II goal is to deliver 1.2 MW of proton
beam power from the Fermilab Main Injector, over the energy range 60 - 120 GeV,
at the start of operation of the LBNF/DUNE program. PIP-II provides a variety
of upgrade paths to higher beam power from the Main Injector, as demanded by
the neutrino science program and as recommended by the 2014 P5 report.
Delivering more than 2 MW to the LBNF target in the future will require a
replacement of the existing Booster. This report outlines a cost-effective
Booster replacement option and an upgrade path for the Fermilab Accelerator
Complex to attain 2.4-MW beam power on the LBNF target, as well as to retain
the capability to provide 8-GeV proton beams to the existing Fermilab Muon
Campus via the existing Recycler ring. Its cost-effectiveness is achieved by:
(1) using a small-diameter metallic vacuum chamber in the Booster replacement
and (2) reusing the existing Recycler ring. Reusing the Recycler ring may be of
particular advantage since it is presently employed to deliver 8-GeV beams to
the Muon Campus experiments. The present concept also retains such a
capability.
