A surprisingly large concentration of radioactive 7Be was observed inthe upper atmosphere at altitudes above 320 km on the LDEF satellite that was recovered in January 1990. We report on follow-up experiments on Russian spacecraft at altitudes of 167 to 370 km during the period of 1996 to 1999, specifically designed to measure 7Be concentrations in low earth orbit. Our data show a significant correlation between the 7Be concentration and the solar energetic proton fluence at Earth, but not with the overall solar activity. During periods of low solar proton fluence, the concentration is correlated with the galactic cosmic ray fluence. This indicates that spallation of atmospheric N by both solar energetic particles and cosmic rays is the primary source of 7Be in the ionosphere.

The Radiation Detection Section of the Naval Research Laboratory (NRL) is sponsored by the Defense Nuclear Agency (DNA) to study the feasibility of using passive cosmic-ray induced neutron signatures as a method of treaty verification. The main thrust has been to use the neutron signature as a unique method for verification of the type of missile or other treaty limited item (TLI) inside a closed container. The detector for the experiments described consisted of nine 3He neutron proportional counter tubes that were three feet long and at a pressure of ten atmospheres. The object of the experiments was to use this neutron detector to measure the neutron signature of a semi-realistic mock-up of a generic missile. Clear variations in the neutron signal at different points over the mock-up are shown, demonstrating that measurable neutron signatures do exist

In 1990 an unexpectedly high concentration of Be-7 was discovered on the LDEF satellite surface, facing in the RAM direction. The search for an explanation of this high concentration of Be-7 which is in thermal equilibrium in the upper atmosphere, led the researchers to the hypothesis of Be-7 transport by vertical turbulent fluxes from deeper layers in the Earth's atmosphere, where Be-7 is produced as a result of nuclear reactions between solar energetic protons (which penetrated there after a solar flare) and terrestrial atmosphere elements. The experiments carried out during 1995-1999 on 'Resource F1' and 'Cosmos' satellites not only confirmed the existence of high Be-7 concentrations at altitudes of about 200 km, but also permitted to establish correlation between the concentration of Be-7 in the upper atmosphere and flare activity on the Sun. More detailed analysis of the whole set of experimental data on Be-7 measurements at satellite altitudes showed, that the appearance of high Be-7 concentrations in the upper atmosphere of the Earth is a more complicated phenomenon. Two more mechanisms , explaining the observed effect can be indicated. Firstly, the observed concentrations could be associated with direct penetration of energetic Be-7 nuclei, originating in flares, into the terrestrial atmosphere. Calculations show, that in solar cosmic rays the flux of Be-7 nuclei should be maximum in comparison to the fluxes of other Beryllium isotopes. Secondly, the high concentration of Be-7 in the upper atmosphere of the Earth could be explained by solar wind penetration through the polar zones. Theoretical analysis of active processes including flares, occurring in the solar atmosphere, leads to the conclusion, that radioactive Beryllium is constantly present in the solar atmosphere, and, possibly, is the main isotope of solar Beryllium.

A Compton camera was constructed using four individual high-purity germanium (HPGe) coaxial detectors in the front plane and four elements of a 15 element HPGe coaxial array in the back plane. 60Co, 133Ba, and 137Cs sources were used in configurations that included single sources in positions covering the intended field-of-view and multiple sources of both identical isotopes and different isotopes. Experiments were also conducted with sources in waste-container sized attenuating media. This proof-of-concept experiment was designed to demonstrate non-tomographic three-dimensional imaging for the characterization of mixed waste containers. The present analysis demonstrates three-dimensional imaging of multiple sources at multiple energies and the imaging of sources within a waste-container sized attenuating medium.