Cosmogenic neutron-capture-produced nuclides in stony meteorites
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, while the location within a meteoroid only affects the relative neutron intensities. Meteoroids need to have radii of more than 50 g/cm/sup 2/ before they have appreciable fluxes of neutrons near thermal energies. Meteoroids with high hydrogen or low iron contents can thermalize neutrons better than chondrites. Rates for the production of /sup 60/Co, /sup 59/Ni, and /sup 36/Cl are calculated with evaluated neutron-capture cross sections and neutron fluxes determined for carbonaceous chondrites with high hydrogen contents, L-chondrites, and aubrites. For most meteoroids with radii < 300 g/cm/sup 2/, the production rates of these neutron-capture nuclides increase monotonically with depth. The highest calculated /sup 60/Co production rate in an ordinary chondrite is 375 atoms/(min g-Co) at the center of a meteoroid with a 250 g/cm/sup 2/ radius. The production rates calculated for spallogenic /sup 60/Co and /sup 59/Ni are greater than the neutron-capture rates for radii less than approx.50-75 g/cm/sup 2/. Only for very large meteoroids and chlorine-rich samples is the neutron-capture production of /sup 36/Cl important. The results of these calculations are compared with those of previous calculations and with measured activities in many meteorites. 44 refs., 15 figs., 1 tab.
- Research Organization:
- York Coll., Jamaica, NY (USA); Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Brookhaven National Laboratory (BNL), Upton, NY (United States)
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 5516326
- Report Number(s):
- LA-UR-85-1545; CONF-850760-1; ON: DE85012689
- Resource Relation:
- Journal Volume: 91; Journal Issue: B4; Conference: 16. lunar and planetary science conference, Bordeaux, France, 16 Jul 1985
- Country of Publication:
- United States
- Language:
- English
Similar Records
Exposure history of H5 chondrite Gujargaon
Cosmogenic {sup 36}Cl accumulation in unstable landforms 1. Effects of the thermal neutron distribution
Related Subjects
GENERAL PHYSICS
COBALT 60 TARGET
NEUTRON REACTIONS
METEOROIDS
NEUTRON TRANSPORT
CAPTURE
CHEMICAL COMPOSITION
COSMIC NEUTRONS
EXPERIMENTAL DATA
ISOTOPE RATIO
MEV RANGE 10-100
PARTICLE TRACKS
BARYON REACTIONS
BARYONS
COSMIC RADIATION
DATA
ELEMENTARY PARTICLES
ENERGY RANGE
FERMIONS
HADRON REACTIONS
HADRONS
INFORMATION
IONIZING RADIATIONS
MEV RANGE
NEUTRAL-PARTICLE TRANSPORT
NEUTRONS
NUCLEAR REACTIONS
NUCLEON REACTIONS
NUCLEONS
NUMERICAL DATA
RADIATION TRANSPORT
RADIATIONS
TARGETS
640101* - Astrophysics & Cosmology- Cosmic Radiation
640107 - Astrophysics & Cosmology- Planetary Phenomena