Predicted versus observed cosmic-ray-produced noble gases in lunar samples: improved Kr production ratios. [From excitation functions for proton spallation of Rb, Sr, Y, Zr at 10 MeV to 10 GeV]
New sets of cross sections for the production of krypton isotopes from targets of Rb, Sr, Y, and Zr were constructed primarily on the bases of experimental excitation functions for Kr production from Y. These cross sections were used to calculate galactic-cosmic-ray and solar-proton production rates for Kr isotopes in the moon. Spallation Kr data obtained from ilmenite separates of rocks 10017 and 10047 are reported. Production rates and isotopic ratios for cosmogenic Kr observed in ten well-documented lunar samples and in ilmenite separates and bulk samples from several lunar rocks with long but unknown irradiation histories were compared with predicted rates and ratios. The agreements were generally quite good. Erosion of rock surfaces affected rates or ratios for only near-surface samples, where solar-proton production is important. There were considerable spreads in predicted-to-observed production rates of /sup 83/Kr, due at least in part to uncertainties in chemical abundances. The /sup 78/Kr//sup 83/Kr ratios were predicted quite well for samples with a wide range of Zr/Sr abundance ratios. The calculated /sup 80/Kr//sup 83/Kr ratios were greater than the observed ratios when production by the /sup 79/Br(n,..gamma..) reaction was included, but were slightly undercalculated if the Br reaction was omitted; these results suggest that Br(n,..gamma..)-produced Kr is not retained well by lunar rocks. The productions of /sup 81/Kr and /sup 82/Kr were overcalculated by approximately 10% relative to /sup 83/Kr. Predicted-to-observed /sup 84/Kr//sup 83/ ratios scattered considerably, possibly because of uncertainties in corrections for trapped and fission components and in cross sections for /sup 84/Kr production. Most predicted /sup 84/Kr and /sup 86/Kr production rates were lower than observed. Shielding depths of several Apollo 11 rocks were determined from the measured /sup 78/Kr//sup 83/Kr ratios of ilmenite separates. 4 figures, 5 tables.
- Research Organization:
- California Univ., San Diego, La Jolla (USA); Washington Univ., St. Louis, MO (USA); Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 6182327
- Report Number(s):
- LA-UR-79-1582; CONF-790381-2; TRN: 79-017217
- Resource Relation:
- Conference: 10. lunar and planetary science conference, Houston, TX, USA, 19 Mar 1979
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
KRYPTON
COSMOCHEMISTRY
LUNAR MATERIALS
CHEMICAL COMPOSITION
PROTON REACTIONS
SPALLATION
RUBIDIUM
STRONTIUM 88 TARGET
YTTRIUM 89 TARGET
ZIRCONIUM
COSMIC RADIATION
EXCITATION FUNCTIONS
GEV RANGE 01-10
ILMENITE
ISOTOPE RATIO
KRYPTON ISOTOPES
MEV RANGE 10-100
MEV RANGE 100-1000
NUCLEOSYNTHESIS
SOLAR PROTONS
ALKALI METALS
BARYON REACTIONS
BARYONS
CHALCOGENIDES
CHARGED-PARTICLE REACTIONS
CHEMISTRY
CROSS SECTIONS
ELEMENTARY PARTICLES
ELEMENTS
ENERGY RANGE
FERMIONS
GEV RANGE
HADRON REACTIONS
HADRONS
IONIZING RADIATIONS
IRON COMPOUNDS
IRON OXIDES
METALS
MEV RANGE
NONMETALS
NUCLEAR REACTIONS
NUCLEON REACTIONS
NUCLEONS
OXIDES
OXYGEN COMPOUNDS
PROTONS
RADIATIONS
RARE GASES
SOLAR PARTICLES
SOLAR RADIATION
STELLAR RADIATION
TARGETS
TITANIUM COMPOUNDS
TITANIUM OXIDES
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
640101* - Astrophysics & Cosmology- Cosmic Radiation
640107 - Astrophysics & Cosmology- Planetary Phenomena
651615 - Nuclear Properties & Reactions
A=59-89
Theoretical- Nuclear Reactions & Scattering- (-1987)