Nuclide production rates in stone meteorites and lunar samples by galactic cosmic radiation

Trivedi, B. M. P.; Goel, P. S.

doi:10.1029/jb078i023p04885

Cited by 26 publications

(8 citation statements)

References 33 publications

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“…Fm both the moon and meteoroids, the ratios of measured/calculated 3H activities were similar, about 1.4. The calculated 3H production profiles for meteorolds of various radii were similar in trend to those of Trivedi and Goel [1973], but were 4).5 of their absolute values. The neutron production profiles monotonically increased with depth for meteorolds having R < 70 g/cm 2 and mainly decreased with depth for R > 300 g/cm 2.…”

mentioning

confidence: 56%

Cosmogenic neutron‐capture‐produced nuclides in stony meteorites

et al. 1986

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The distribution of neutrons with energies below 15 MeV in spherical stony meteoroids is calculated using the ANISN neutron‐transport code. The source distributions and intensities of neutrons are calculated using cross sections for the production of tritium. The meteoroid's radius and chemical composition strongly influence the total neutron flux and the neutron energy spectrum, whereas the location within a meteoroid only affects the relative neutron intensities. Meteoroids must have radii of more than 50 g/cm2 before they have appreciable fluxes of neutrons near thermal energies. Meteoroids with high hydrogen or low iron contents can thermalize neutrons better than chondrites can. Rates for the production of 60Co, 59Ni, and 36Cl are calculated with these neutron fluxes and evaluated neutron‐capture cross sections and are reported for carbonaceous chondrites with high hydrogen contents, L‐chondrites, and aubrites. For most meteoroids with radii <300 g/cm2, the production rates of these neutron‐capture nuclides increase monotonically with depth. The highest calculated 60Co production rate in an ordinary chondrite is 375 atoms/min/g‐Co at the center of a meteoroid with a 250 g/cm2 radius. The production rates calculated for spallogenic 60Co and 59Ni are greater than the neutron‐capture rates for radii less than ∼50–75 g/cm2. Only for very large meteorpids and chlorine‐rich samples is the neutron‐capture production of 36Cl important. The results of these calculations are compared with those of previous calculations and with measured activities in many meteorites.

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confidence: 56%

Cosmogenic neutron‐capture‐produced nuclides in stony meteorites

et al. 1986

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“…Ouyang, 1981; G. Heusser, personal communication, 1982], The 22 Na activities in Jilin are fairly constant for these depths, unlike the predictions of Trivedi and Goel[ 1973], which show a strong drop with increasing depth for a meteorite of that radius. The a-versus-depth curves for these four cases are fairly well determined.…”

Section: Depthmentioning

confidence: 95%

“…The calculated production profiles for 'H and 22 Na are similar to those of Trivedi and Goe/[1973] for R < 100 g cm" 2 , but for larger radii, the profiles calculated here drop much slower with increasing depth than do theirs. The Trivedi and Goel [1973] profile for 22 Na gives a very poor fit to the 22 Na measured in Jilin (G. Heusser, personal communication, 1982). The Trivedi-Goel profile for 3 H in a meteorite of infinite radius DEPTH <fl cm-') Fig.…”

Section: Calculated Production Ratesmentioning

confidence: 99%

“…The isotope ratio Ne/ 21 Ne has been used for empirically determined, shieldingcorrected production rates (for example, Nishiizumi et al, [1980]), but this ratio does not uniquely determine the sample's exact exposure geometry or a nuclide's production rate. Trivedi and Goel [1973] calculated production rates for the radionuclides 3 H and 22 Na in stony meteorites as a function of size and depth by using the model of Kohman and Bender [1967] and thick target results for silicate targets. Nyquist [1969Nyquist [ ,1984 has extended the semiempirical model of Signer and Nier [1960] to chondrites for several noble-gas isotopes.…”

Section: Introductionmentioning

confidence: 99%

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A model for GCR‐particle fluxes in stony meteorites and production rates of cosmogenic nuclides

Reedy¹

1985

J. Geophys. Res.

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A model is presented for the differential fluxes of galactic cosmic ray (GCR) particles with energies above 1 MeV inside any spherical stony meteorite as a function of the meteorite's preatmospheric radius and the sample's depth. This model is based on the Reedy‐Arnold equations for the energy‐dependent fluxes of GCR particles in the moon and is an extension of flux parameters that were derived for several meteorites of various sizes. This flux model is used to calculate the production rates of many cosmogenic nuclides as a function of radius and depth. The peak production rates for most nuclides that are created by the reactions of energetic GCR particles occur near the centers of meteorites with radii of 40 to 70 g cm−2. The calculated production rates usually agree well with measurements of cosmogenic nuclides in most meteorites. Although the model has some limitations, it reproduces well the basic trends observed for the depth‐dependent production of cosmogenic nuclides in stony meteorites of various radii. Some of these production profiles are different from those of other calculations. The chemical dependence of the production rates for several nuclides varies with size and depth.

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“…Kohman and Bender (1967) derived a model for the production ofcosmogenic nuclides in iron meteorites from the analysis of production rates measured in simulation experiments during which stationary thick targets had been irradiated with highenergy particles. Trivedi and Goel (1973) extended this approach to stony meteorites and lunar samples. As discussed earlier (Michel et al, 1985), in all stationary thick-target experiments the measured production rates are dominated by proton-induced reactions which mostly are hiding the action of secondary neutrons.…”

Section: Introductionmentioning

confidence: 99%

On the production of cosmogenic nuclides in meteoroids by galactic protons

Michel¹,

Dragovitsch²,

Cloth³

et al. 1991

Meteoritics

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Abstract-A purely physical model is presented describing the depth-and size-dependence of the production of cosmogenic nuclides in meteoroids with radii up to 85 ern and in planetary surfaces by galactic cosmic ray protons. The model is based on Monte Carlo calculations of the intra-and internuclear cascades, by which depth-and size-dependent spectra of primary and secondary protons and of secondary neutrons are derived, and on experimental and theoretical thin-target cross sections of the underlying nuclear reactions. Model calculations are presented for production rates of "Mn, 26A1, 22Ne, and 21Ne in H-and L-chondrites and of "Mn and 26Al in lunar surface material and compared with experimental data. From the analysis of "Mn and 26AI in the Apollo 15 lunar drill core and in the L-chondrite Knyahinya GCR p-spectra and integral particle fluxes at I A.U. and in the meteoroid orbits averaged over the last 10 Ma are derived. An analysis of experimental depth profiles in four H-and L-chondrites demonstrates, that the new model is well capable of describing depth-and size-dependences of production rates of cosmogenic nuclides. Moreover, it is possible to determine exposure ages for these meteorites on the basis of the theoretical i'Ne production rates. The model calculations further explain the depth-and size-dependence of22Ne/ 21 Ne-ratios and the dependences on these ratios of 21Ne, 26AI and 5JMn production rates. The future requirements for model calculations of cosmogenic nuclide production rates in extraterrestrial matter are outlined.

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Nuclide production rates in stone meteorites and lunar samples by galactic cosmic radiation

Cited by 26 publications

References 33 publications

Cosmogenic neutron‐capture‐produced nuclides in stony meteorites

Cosmogenic neutron‐capture‐produced nuclides in stony meteorites

A model for GCR‐particle fluxes in stony meteorites and production rates of cosmogenic nuclides

On the production of cosmogenic nuclides in meteoroids by galactic protons

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