Revision 1

Accepted · first revision · record

Title: Nuclear fragmentation cross sections for therapy beams
Plain: Heavy ions break up when they hit nuclei in tissue, creating lighter fragments that deposit dose past the tumour. The break-up probabilities are not measured well enough.
Precise: Measure and model partial charge-changing and isotopic production cross sections for projectiles of Z from 2 to 10 at 100 to 450 MeV per nucleon on hydrogen, carbon, nitrogen, oxygen and calcium targets, to about 5 percent, including fragment angular and energy distributions. An answer is a cross-section set that lets Monte Carlo transport reproduce measured depth-dose tails to within 1 percent of peak dose.
Settled by: Thin-target fragmentation experiments covering the therapeutic energy range, benchmarked against measured depth-dose and lateral profiles.
Kind: well-posed
Answer type: value
References: (empty)
Literature status: open
Status note: Dedicated campaigns since about 2020 have filled gaps, yet model spread in the fragment tail remained several percent in 2025.
Posed since: 1990