Speaker
Description
The PIP-II 800 MeV, CW-capable superconducting-RF H⁻ linac at Fermilab must deliver at least 1.2 MW to LBNF/DUNE while holding uncontrolled beam loss below the hands-on-maintenance limit of ~1 W/m, a challenge rooted in its deliberately non-equipartitioned, strongly space-charge-dynamics, where the transverse tune depression reaches η ≈ 0.65 in the HWR and SSR1 spoke sections and space charge drives emittance exchange, coherent-mode growth, and halo formation. We present a design-time screening-and-margin chain spanning nonlinear space charge, halo and emittance growth, and the uncontrolled-loss budget, developed in preparation for instrumented commissioning. The focusing and synchronous-phase profiles are shaped to steer the lattice clear of the parametric coupling that drives transverse-longitudinal emittance exchange, and a matched envelope is maintained throughout to suppress mismatch-driven halo. A corrected, iso-limit-validated anisotropic Hofmann coherent-mode solver screens the low-order modes (ℓ = 2, 3, 4ₑ) along the design trajectory, and on the mildly anisotropic lattice (ε_z/ε_x ≈ 1.5) only the weak ℓ = 2 envelope modes approach threshold, leaving a stability margin of at least 1.8× to the anisotropic-instability onset. Probabilistic margin contours and a calibrated machine-learning surrogate make the screen reproducible for commissioning-time use and, together with precomputed fault-recovery redistribution maps, provide a basis for ML-based dynamic retuning against unexpected beam behavior and single-element faults. Independent particle-in-cell and tracking simulations with full 3D space charge confirm emittance growth below 5%, bounded halo, and 100% transmission, and the resulting H⁻ loss budget places intra-beam, residual-gas, and Lorentz stripping individually below the limit, yielding actionable collimation, aperture, vacuum, and matching specifications for PIP-II commissioning.