Fermilab Redirects Accelerator Upgrades to Neutrino Program as US Collider Plans Stall

The arXiv preprint by M. Convery details ongoing reconfiguration of the Fermilab complex, including replacement of the 400 MeV linac with an 800 MeV superconducting PIP-II accelerator and reconfiguration of the Recycler and Main Injector for higher-intensity proton delivery. These changes directly support the Long-Baseline Neutrino Facility rather than any near-term collider program. The shift follows the 2023 P5 report recommendation to complete DUNE as the highest-priority domestic project before committing to new collider construction.

This trajectory reflects a broader US pivot away from energy-frontier colliders after the 2014 termination of the Tevatron and the absence of domestic follow-on machines. European and Asian programs continue to advance FCC-ee and CEPC concepts while US infrastructure investments concentrate on intensity-frontier neutrino physics. The Convery document makes explicit that beam power for neutrino experiments now drives magnet and RF upgrades previously scoped for collider compatibility.

The strategic consequence is a potential decade-long gap in US hadron collider capability. Without new civil construction or magnet R&D funding, Fermilab's complex will lack the infrastructure required for a multi-TeV muon or hadron collider even if international partnerships materialize. Current upgrades lock in a neutrino-optimized lattice that would require costly re-engineering for collider use.

Next milestones include PIP-II commissioning in 2028 and first DUNE beam in 2031. Any reversal toward collider priorities would require new P5 guidance and congressional appropriations exceeding current neutrino baselines.