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Earth / cosmic ray model

Earth / cosmic ray model. Source radiation: Castagnoli & Lal, 1980 Protons & alphas: 10 MeV/nucleon < E < 1 TeV/nucleon Isotropic source 550 MV solar modulation Current low latitude model cuts all particles at given cutoff rigidity and maintains isotropy… this is probably wrong

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Earth / cosmic ray model

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  1. Earth / cosmic ray model • Source radiation: Castagnoli & Lal, 1980 • Protons & alphas: 10 MeV/nucleon < E < 1 TeV/nucleon • Isotropic source • 550 MV solar modulation • Current low latitude model cuts all particles at given cutoff rigidity and maintains isotropy… this is probably wrong • Full set of particles transported and recorded • Neutrons, protons, pions, kaons, muons, alphas, tritons, He-3, deuterons • 100 km atmosphere, divided into >100 concentric shells • Planet shells finely spaced to achieve higher resolution near boundaries

  2. Deep atmospheric simulation • Artificially deep atmosphere to remove surface albedo bias (2,032 g/cm2 with a water planet below) • Tallies throughout atmosphere capture energy and angular distributions and flux • Attenuation length of high energy neutron flux decreases from peak of flux to the lower atmosphere

  3. MCNPX neutron flux results

  4. MCNPX proton flux results

  5. Production rates via flux & excitation functions • Excitation functions provided by Bob Reedy: • O(n,x) 10Be: Tuniz et al., 1984 • O(p,x)10Be: Evaluated, Nishiizumi+09 GCA • Si(n,x)10Be: T4N 6/20/83 • Si(p,x)10Be: Evaluated, Nishiizumi+09 GCA • O(n,n2p)14C: Imamura+'90<35-MEV, 7/9/97 • O(p,x)14C: R. C. Reedy (2007) Lunar Planet. Sci. 38, Abstract #1192 • Si(n,x)14C: Low E'S shift down 5 MEV XS times ~2 5/7/97 • Si(p,x)14C: R. C. Reedy (2007) Lunar Planet. Sci. 38, Abstract #1192 • Si(n,x)26Al: proton data with (p,a) part deleted • Si(p,x)26Al: Evaluated, Nishiizumi+09 GCA. • K(n,x)36Cl: 1/6/91 EXPTL (n,a) to 14 MeV, lower at high e • K(p,x)36Cl: Evaluated, Nishiizumi+09 GCA. • Ca(n,ap)36Cl: 1/6/91 revised to fit CA/FE=6, 0.8*LO-E • Ca(p,x)36Cl: Evaluated, Nishiizumi+09 GCA

  6. Free air production rate potentials • SiO2(n or p,x)10Be: 4.1 • SiO2(n or p,x)14C: 13.2 • SiO2(n or p,x)26Al: 29 Sea level, high latitude production rates (atoms g-1 yr-1) • Ca(n or p,x)36Cl: 39 • K(n or p,x)36Cl: 120

  7. Free air attenuation lengths

  8. Production ratios Production ratios for sea level - 450 g/cm2 • Ca - 36Cl / 10Be: 9.37 - 9.06 • K - 36Cl / 10Be: 29.3 - 28.4 • 14C / 10Be: 3.24 - 3.07 • 26Al / 10Be: 6.98 - 6.80

  9. Ratios normalized to sea level

  10. CRONUS (UW) calibration data

  11. Boundary effects: granite

  12. Boundary effects: preliminary basalt

  13. Neutron flux in granite

  14. Fine energy binning in granite

  15. Nuclide production in granite

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