Neutrino Radiation Challenges and Proposed Solutions for Many-TeV Muon Colliders

TL;DR

Neutrino radiation poses significant challenges for many-TeV muon colliders, requiring large isolated sites to minimize human exposure, and influencing future collider site planning and design.

Contribution

This paper extends previous neutrino radiation dose predictions to many-TeV muon colliders, analyzing their implications for site selection and collider design.

Findings

Radiation doses increase less steeply than energy cubed at high energies.

Large isolated sites are necessary to mitigate human exposure to neutrino radiation.

Linear muon colliders have significantly reduced radiation constraints.

Abstract

Neutrino radiation is expected to impose major design and siting constraints on many-TeV muon colliders. Previous predictions for radiation doses at TeV energy scales are briefly reviewed and then modified for extension to the many-TeV energy regime. The energy-cubed dependence of lower energy colliders is found to soften to an increase of slightly less than quadratic when averaged over the plane of the collider ring and slightly less than linear for the radiation hot spots downstream from straight sections in the collider ring. Despite this, the numerical values are judged to be sufficiently high that any many-TeV muon colliders will likely be constructed on large isolated sites specifically chosen to minimize or eliminate human exposure to the neutrino radiation. It is pointed out that such sites would be of an appropriate size scale to also house future proton-proton and electron-positron colliders at the high energy frontier, which naturally leads to conjecture on the possibilities for a new world laboratory for high energy physics. Radiation dose predictions are also presented for the speculative possibility of linear muon colliders. These have greatly reduced radiation constraints relative to circular muon colliders because radiation is only emitted in two pencil beams directed along the axes of the opposing linacs.