No abstract

A neutron detector sensitive from 2 to 100 MeV is described. neutron/cm -sec at a counting rate of one per minute, the energy resolution is 12% at 15 MeV and 30% at 100 MeV. The angle between the incoming neutron and the recoil neutron is measured to ± 10 .

Additional calibrations of the University of California double‐scatter neutron detector and additional analysis corrections lead to the slightly changed neutron fluxes reported here. The theoretical angular distributions of Merker (1975) are in general agreement with our experimental fluxes but do not give the peaks for vertical upward and downward moving neutrons. The theoretical neutron escape current J2π (Merker, 1972; Armstrong et al., 1973) is in agreement with the experimental values from 10 to 100 MeV. Our experimental fluxes agree with those of Kanbach et al. (1974) in the overlap region from 70 to 100 MeV.

The altitude dependence of atmospheric neutrons from ground level to 5 g/cm² of residual atmosphere at neutron energies of 10–100 MeV is reported. Ground level measurements were taken at Cape Girardeau, Missouri, on September 18, 1972. The other measurements were made during ascent and float on launch from Palestine, Texas, on September 26, 1971. The intensity of both the downward‐ and the upward‐moving neutrons is maximum at about 100 g/cm² of residual atmosphere. Neutron angular distributions are reported from 20° to 80° and 100° to 160° for 10‐ to 100‐MeV neutrons. Omnidirectional fluxes at altitudes of 5, 50, 100, and 200 g/cm² of residual atmosphere are in good agreement with recent theoretical calculations of Armstrong et al. in the three energy intervals of 10–30, 30–50, and 50–100 MeV.

The energy and flux measurement of D–D and D–T fusion neutrons provides a nonperturbing probe of plasma performance. In particular, ion temperature distribution of the plasma can be determined. This information can distinguish neutron production mechanisms, i.e., knock-on or thermonuclear in origin. To perform a fast neutron measurement, a high data rate double scatter spectrometer has been developed. This allows for a definitive measurement of the flux, energy, angle, and time distributions of neutrons from within the plasma. In addition, x-ray discrimination can be achieved from the time-of-flight information. The specific design issues and performance of the spectrometer will be described.