Spur-track structure: LET scaling ρ_track ∝ LET; α/γ ≈ 2000/3

Spur theory (Samuel & Magee 1953, Mozumder-Magee 1966) partitions the primary radiation track into localised radical clusters of characteristic size and energy: (a) spurs — isolated events of ≈4 ion pairs, radius ~2 nm, produced by low-LET…