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Walton et al. 1976
Walton, J.R., Heymann, D. and Yaniv, A. (1976). Production of He, Ne, and Ar isotopes and 236U in lunar materials by solar cosmic ray protons—production rate calculations. Journal of Geophysical Research 81. doi: 10.1029/JB081i032p05701. issn: 0148-0227.

A computer program has been written for calculating rates of formation of solar cosmic ray (SCR) proton-produced nuclides at 50 depths ranging from 0 to 25 g/cm2 in materials with the average atomic number Z=13. Production rates are presented for 2&pgr; isotropic irradiation of a semi-infinite plane surface for two incident SCR spectra of different spectral shapes: spectrum A, derived from data for the years 1959 and 1960, and spectrum B, derived from data for the years 1956, 1959, and 1960. For each spectrum, two cases are considered: (1) integration of the production equation from threshold energy to 45 MeV and (2) integration from threshold to 200 MeV. Data are presented which permit the calculation of the following production rates: (1) 3H, 3He, 3He&tgr;(≡3H+3He), and 4He in bulk lunar samples, (2) 20Ne, 21Ne, 22Ne, 22Na, and 22Ne&tgr;(≡22Ne +22Na) in lunar samples containing variable amounts of Mg, Al, Si, and Na, and (3) 36Ar, 37Ar, 38Ar, and 39Ar in lunar samples containing variable contents of Ca and, for 39Ar, also variable contents of Ti. In addition, 236U/238U saturation ratios in natural U are presented as a function of depth. Comparison of SCR production rates with production rates by galactic cosmic ray (GCR) protons for 3He&tgr;, 21Ne, and 38Ar shows that SCR production dominates overwhelmingly at 0.0 g/cm2 and remains at least comparable to depths of about 5--10 g cm2 for spectrum B. Isotopic ratios of He and Ne produced by SCR protons are distinctly different from those produced by GCR protons at all depths; the GCR value of 36Ar/38Ar, however, falls within the range of SCR-produced values.

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Journal of Geophysical Research
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