Charge-weighted quality factors based on LET for practical dose assessment of space radiation

We demonstrate a new charge weighted quality factor, noted Q*, based on the practical application of particle linear energy transfer (LET) and charge (Z)-dependent quality factors for LET-based radiation dosimetry in space. Z contribution factors are defined according to the energy spectra of galactic cosmic rays (GCRs). The Z-weighted quality factor depending solely on the LET (Q*) under solar minimum conditions in free space differs by only a few percent from values obtained with spacecraft shielding or during the solar maximum spectrum. Q* values based on various biological endpoints exhibit peaks at higher LETs than those defined in ICRP-60. The reduced contribution of GCR heavy components under Q*, compared to Q_ICRP of ICRP-60, suggests that current dose assessments may be overestimated. The proposed Q* approach is applicable to different LET- and Z-dependent quality factors, and provides practical dose evaluation using LET measurements.