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Anin situ measurement of the lunar neutron density from 20 to 400 g cm-2 depth below the lunar surface was made by the Apollo 17 Lunar Neutron Probe Experiment (LNPE) using particle tracks produced by the10B (n,a)7Li reaction. Both the absolute magnitude and the depth profile of the neutron density are in good agreement with theoretical calculations by Lingenfelter, Canfield, and Hampel. However, relatively small deviations between experiment and theory in the effect of Cd absorption on the neutron density and in the relative149Sm to157Gd capture rates reported previously (Russet al., 1972) imply that the true lunar157Gd capture rate is about one half of that calculated theoretically.

Anin situmeasurement of the lunar neutron density from 20 to 400 g cm-2depth below the lunar surface was made by the Apollo 17 Lunar Neutron Probe Experiment (LNPE) using particle tracks produced by the10B (n,a)7Li reaction. Both the absolute magnitude and the depth profile of the neutron density are in good agreement with theoretical calculations by Lingenfelter, Canfield, and Hampel. However, relatively small deviations between experiment and theory in the effect of Cd absorption on the neutron density and in the relative149Sm to157Gd capture rates reported previously (Russet al., 1972) imply that the true lunar157Gd capture rate is about one half of that calculated theoretically.