Environmental Amplification of Solid Deuterium Surface Frost: A Unified Solution to the Neutron Lifetime Puzzle

The persistent discrepancy between bottle and beam measurements of the free neutron
lifetime has narrowed following the December 2024 J-PARC electron-detection result (τn =
877.2±4.5 s), which agrees with magnetic bottle experiments and identifies a ∼ 10 s systematic
in proton-detection methods. However, residual scatter among bottle measurements (877–881
s) remains unexplained. We identify progressive surface degradation of solid deuterium (SD2)
ultracold neutron (UCN) converters as a source of systematic bias through spectral hardening
and marginally-trapped UCN contamination. Direct time-of-flight measurements at PSI doc
ument real-time spectral hardening consistent with frost accumulation over measurement-day
timescales. Marginally-trapped UCN with escape times of 10–100 s have demonstrated system
atic biases exceeding 200 s in NIST magnetic trap studies. Multi-site observations (PSI, LANL,
NCSU) confirm frost formation, yield degradation, and complete recovery with conditioning,
establishing reversibility. Environmental factors at LANL—including 2231 m altitude, large di
urnal temperature swings (15–25 K), and pulsed spallation heating—may accelerate degradation
relative to sea-level sources. We provide falsifiable predictions testable through archival analysis
and controlled experiments, including anti-correlation with ambient temperature, dependence
on source conditioning cycles, and campaign-sequence evolution.