Cross sections have been measured for the emission of protons, deuterons, and alpha particles for 15-MeV neutrons on $^{54,56}\mathrm{Fe}$, $^{58,60}\mathrm{Ni}$, $^{50,52}\mathrm{Cr}$, and $^{63,65}\mathrm{Cu}$, as well as on natural iron, nickel, and chromium. A quadrupole spectrometer served to detect particles with energies as low as 1 MeV. For some of the targets, a substantial fraction of the charged-particle spectrum is at energies below the Coulomb barrier. Cross sections and spectra are compared with statistical and pre-equilibrium model predictions.NUCLEAR REACTIONS $^{50,52}\mathrm{Cr}$, Cr, $^{54,56}\mathrm{Fe}$, Fe, $^{58,60}\mathrm{Ni}$, Ni, $^{63,65}\mathrm{Cu}$, ($n$,$p$), ($n$,$d$), ($n$,$\ensuremath{\alpha}$), $E=14.8$ MeV; measured $\ensuremath{\sigma}({E}_{p},\ensuremath{\theta})$, (${E}_{d}$, $\ensuremath{\theta}$), (${E}_{\ensuremath{\alpha}}$, $\ensuremath{\theta}$), enriched and natural targets. Hauser-Feshbach analysis, deduced reaction mechanism.

Systems consisting of two or three magnetic quadropole lenses and detectors were developed for studying charged particles produced by 15 MeV neutrons. The lenses transport the charged particles from a radiator near the neutron source to the detectors located about 2.6 m away in order to reduce the neutron-induced background in the detectors.

Measurements were made of the hydrogen and helium production cross sections for both natural elements and separated isotopes which are constituents of metal under consideration for the first wall of fusion reactors. (MOW)

A spectrometer to measure neutron-induced charged-particle producing reactions was developed and yields data with greatly improved signal-to-background ratios. It consists of a magnetic quadrupole lens which focusses the charged particles onto a silicon surface barrier detector or a two-detector telescope which is more than 2 meters from the sample being irradiated. The efficiency of the spectrometer is calibrated experimentally and depends only on values for the (n,p) elastic cross section and the stopping power of polyethylene. Further development is underway to replace the surface-barrier ..delta..E counter with a proportional counter of larger area. This detector, combined with a larger E counter (surface barrier) could increase the effective solid angle by a factor of five. The results for (n,xp), (n,xd) and (n,x..cap alpha..) cross sections are summarized for the eight target materials studied so far. Measurements of the charged particle spectra have established that cross sections for production of protons below 2.5 MeV are significant for some targets; in fact protons as low as 800 keV have been detected from aluminum. These low energy protons would be quite difficult to measure with conventional counter telescope spectrometers.

The crystal blocking effect was used to study the time distribution of 5- MeV protons elastically scattered from a germanium crystal. The time delay associated with compound-elastic scattering is estimated and used to separate the direct and compound-nuclear contributions to the elastic cross section.

A determination free of the distortions arising from lead gamma-shielding has been made, using CsI(Tl) as spectrometer of protons from a polyethylene radiator in coincidence with two gas proportional counters. Gamma response was completely suppressed by the combination of coincidence selection and pulse height discrimination. The spectrum shape matches that computed from contributing cross sections, an agreement which includes a larger rising slope than has previously been observed. Structure above the main peak is identifiable with (α,n) transitions to the 4.43-MeV state in 12C. Comparison of the spectrum integral with moderated thick-target yields indicates that the low-energy contributions of 9Be(α,n)3α and photo-neutrons (not measured in this experiment) constitute 30% of the entire spectrum, in agreement with the a priori estimate.