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Differential cross sections for the elastic scattering of various hydrogen and helium isotopes have been measured using accelerated particles from the Los Alamos 42-inch cyclotron. The scattering of protons and deuterons from deuterons, tritons, and helium-three particles has been studied over an energy range of 5 to 14 Mev. The elastic scattering of ^10-Mev polarized protons has also been studied. In all cases nuclear emulsions were used as detectors.Proton-deuteron elastic scattering has been measured at 5.6 and 7.85 Mev. A comparison is made to results at nearby energies of both p-D and n-D scattering and to theoretical predictions. The scattering of 10-Mev polarized protons from deuterons has been measured and provides support for calculations using central force approximations.Measurements of p-T and />-He 3 elastic scattering at 6.5 and 8.34 Mev give angular distributions which are quite similar to those for p-D and p-Ke*. An encouraging agreement is found with resonating-group calculations with central-force approximations of the Serber type.Deuteron-deuteron scattering has been measured at 6.0, 8.2, 12.1, and 13.8 Mev. A preliminary theoretical treatment indicates that the process is predominantly hard-sphere scattering with no strong level splitting.Deuteron-triton and deuteron-helium three scattering has been measured over the energy range of 5 to 14 Mev.

The neutron spectra from the interaction of 14-Mev neutrons with a number of elements have been determined by nuclear plate techniques. The plates were exposed to neutrons from the bombardment of a Zr-T target by 200-kev deuterons when the target was as nearly as possible isolated from all scattering material and when the target was surrounded by a spherical shell of the element to be investigated. The variation of F(E n ), the number of emitted neutrons per unit energy interval with energy (E n ), appears to be Maxwellian in the region 0.5 to 4.0 Mev and may be represented by

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The neutron spectrum associated with the fission of U 235 induced by slow neutrons has been remeasured from 0.18 to 12 Mev. Two different experimental techniques were employed in this measurement: (1) the time-of-flight method covering the energy range from 0.18 to 2.7 Mev, and (2) the photographic plate method encompassing the energy range from 0.35 to 12 Mev. The combined results of these measurements fit the relation, N{E)^Ke^E' QMh sinh[(2.29£)»], where N(E) is the neutron flux, E is the neutron energy in Mev and K is a constant. The simpler expression, N(E) =KEh~°-17bE , also fits the data well for neutron energies below 9 Mev.f This work was performed under the auspices of the U. S.