ABSTRACT
We report major element composition ratios for regions of the asteroid 433 Eros imaged during two solar flares and quiet sun conditions during the period of May to July 2000. Low aluminum abundances for all regions argue against global differentiation of Eros. Magnesium/silicon, aluminum/silicon, calcium/silicon, and iron/silicon ratios are best interpreted as a relatively primitive, chondritic composition. Marked depletions in sulfur and possible aluminum and calcium depletions, relative to ordinary chondrites, may represent signatures of limited partial melting or impact volatilization.
ABSTRACT
High-quality photon-production data from thermal-neutron-capture reactions are important for many applications, including oil-well logging, planetary gamma-ray spectroscopy, and environmental techniques. Radiation transport codes usually access photon-production data from the national U.S. nuclear database, ENDF/B. To improve the photon-production data for thermal-neutron capture, we have compiled and evaluated the energies and yields of gamma rays for most naturally occurring isotopes with Z < 31 and for a few heavier isotopes. The impact of improved photon-production cross sections for thermal-neutron capture in Cl is illustrated by comparing MCNP simulations and experimental measurements for a pulsed neutron oil-well logging instrument. The new compilation of photon-production data is being incorporated into the latest ENDF/B evaluations for each isotope and will be provided for future releases of the ENDF/B database.
