Transport of light ions in matter

Abstract

A recent set of light ion experiments are analyzed using the Green's function method of solving the Boltzmann equation for ions of high charge and energy (the GRNTRN transport code) and the NUCFRG2 fragmentation database generator code. Although the NUCFRG2 code reasonably represents the _agmentation of heavy ions, the effects of light ion fragmentation requires a more detailed nuclear model 'qrancluding shell structure and short range correlations appearing as tightly bound clusters in the light ion nucleus. The most recent NUCFRG2 code is augmented with a quasielastic alpha knockout model and semiempirical adjustments (up to 30 percent in charge removal) in the fragmentation process allowing reasonable agreement with the experiments to be obtained.A final resolution of the appropriate cross sections must await the full development of a coupled channel reaction model in which shell structure and clustering can be accurately evaluated. Publishedby Elsevier Science Ltd on behalf of COSPAR.

Description of Transport Codes for Space Radiation Shielding

“…The nuclear cross sections needed for space radiation transport include nuclear absorption, heavy ion fragmentation, light ion scattering, and particle production cross sections. Nuclear absorption cross sections are well described by current models with accuracies of T5% for most collision pairs of interest (Tripathi et al 1998). Fragmentation cross sections for heavy fragments are known to about T25% accuracy (Cucinotta et al , 2007, with most of the error localized to a nearby fragment with a similar A, Z, and kinetic energy, thus reducing the impact of errors in estimating biological effects.…”

A procedure for benchmarking laboratory exposures with 1A GeV iron ions

“…(25). In the past, we have expanded the angular integral over X 0 asymptotically and implemented as a marching procedure (HZETRN, Wilson and Badavi, 1986), as a perturbation expansion (Wilson et al, 1984), and by non-perturbative approximation (Wilson et al, 1994a) resulting in three distinct methods to evaluate the firstorder asymptotic terms, all of which have had extensive experimental validation (Shavers et al, 1993;Wilson et al, 1998;Shinn et al, 1998). Independent of the method used to evaluate the lowest-order term, the first correction term is found by replacing the fluence in the integrand of Eq.…”

HZE ion fragmentation cross-section sensitivity and propagated errors in HZE exposure estimates

“…The solution of the Boltzmann equation depends on stopping power S j (E), nuclear total cross-sections j (E), and nuclear fragmentation cross-sections jk (E, E ). The stopping powers and nuclear total cross-sections are known to a high degree of accuracy (few percent, Tai et al, 1997;Wilson et al, 1998;Walker et al, 2005) but fragmentation cross-sections are more dependent on details of the nuclear process, are less investigated experimentally, and exhibit more uncertainty when tested experimentally (Wilson et al, 1995b(Wilson et al, , 1998Walker et al, 2005;Golovchenko et al, 2002). In the present paper, we investigate the sensitivity of the dose equivalent calculations due to fragmentation cross-section uncertainty using sensitivity analysis.…”