Overview of nuclear fragmentation models and needs.

Area of Science:

• Space radiation physics
• Nuclear astrophysics
• Materials science for space applications

Background:

• Accurate assessment of spacecraft shielding and astronaut radiation exposure from galactic cosmic radiation (GCR) necessitates precise characterization of radiation fields through thick absorbers.
• Key nuclear interactions include elastic/inelastic collisions, nuclear breakup (fragmentation), and electromagnetic dissociation (EMD), which significantly alter radiation field composition.

Purpose of the Study:

• To review theoretical models for heavy ion fragmentation used in cosmic-ray transport and shielding codes.
• To identify shortcomings in current theoretical models and propose necessary improvements for accuracy and generality.

Main Methods:

• Review of existing theoretical models for heavy ion nuclear fragmentation.
• Analysis of discrepancies between theoretical predictions and experimental data for fragmentation cross sections.
• Discussion of implications for cosmic-ray transport and shielding code input.

Main Results:

• Current theoretical models exhibit significant cross-section prediction errors (25% to a factor of two) for nuclear fragmentation.
• These cross-section errors directly translate to comparable inaccuracies in transported radiation flux, particularly for high linear energy transfer (LET) particles.
• Existing models lack the necessary accuracy and generality for all relevant collision pairs and energies in space radiation protection.

Conclusions:

• There is a critical need for improved theoretical frameworks to accurately predict nuclear fragmentation cross sections.
• Enhancing the accuracy and generality of these models is essential for reliable space radiation transport and shielding calculations.
• Further research and development are required to address the identified shortcomings and ensure astronaut safety in space environments.