The cross section for the Be 9 (n, t')Li 7 *-+L/ + y (0.477 Mev) reaction has been measured in the vicinity of 14 Mev by detecting the gam;ma-rays at scattering angles from 30 to 150 degrees. A time-of-flight technique was used to distinguish the gamma-rays from the high neutron background. The cross section drops_from 20mb at 13.6 Mev to 10mb at 14. 1 Mev and then rises to 30mb at 14.7 Mev.
Reversing the procedure of a number of years' work in the determination of the cross sections for production of • rays by 14-Mev neutrons interacting in pure elements, we have been studying the feasibility of applying our techniques to the remote chemical analysis of unknown materials. We have measured the spectra of • rays produced by neutrons in a large sandpile containing various known percentages of the elements O, Mg, A1, Si, and Fe.A general statement can be made that a 5 per cent abundance of any of these elements can be quantitatively determined to a precision of better than 10 per cent. The method, using fast gating and timing circuits to select only the • rays originating unambiguously from the neutron inelastic scattering process, appears so promising that a miniature, pulsed accelerator is now being tested and packaged. Applications to the analysis of the lunar surface, planetary atmospheres, and the earth's crust and mantle are discussed.
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