  Following the PIP-II 800 MeV Linac, Fermilab will need an accelerator that
extends from that linac to the MI injection energy of ~8 GeV, completing the
modernization of the Fermilab high-intensity accelerator complex. This will
maximize the beam available for neutrino production for the long baseline DUNE
experiment to greater than 2.5 MW and enable a next generation of intensity
frontier experiments. In this white paper, we propose an 8 GeV Linac for that
purpose. The Linac consists of an extension of the PIP-II Linac to ~2 GeV using
PIP-II 650 MHz SRF cryomodules, followed by a 2 -->8.0 GeV Linac composed of
1300 MHz SRF cryomodules, based upon the LCLS-II cryomodules developed at
Fermilab. The 8 GeV Linac will incorporate recent improvements in SRF
technology. The research needed to implement this Linac is described.
