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A large increase in the atmospheric neutron flux was observed at balloon altitudes on September 3, 1966, during a solar proton event. The flux and energy spectrum of the solar particles are known with some precision from satellite detectors, as well as from our balloon measurements. From these data quantitative comparisons have been made with the predictions of Lingenfelter and Flamm (1964) on the production of neutrons in the atmosphere by p•oton interactions. The theory is in satisfactory agreement with the observations, although there is considerable uncertainty about the fraction of neutrons that leaked out of the atmosphere. The distribution of neutrons produced in the atmosphere by solar protons has been derived by Lingenfelter and Flarnm [1964a]. These authors [1964b] have also calculated the flux of albedo neutrons of energy less than 10 Mev resulting from solar protons. This work is important for the determination of the inject]on rate of geomagnetically trapped protons by the SPAND process (see, for example, Dragt et al. [1966]) and for estimates of the carbon-14 production rate during solar proton events. Tests of the theory of Lingenfelter and Flamm are complicated by an error in their calculations (R. E. Lingenfelter, private communication, 1968) that has the effect of approximately doubling the predicted values of all atmospheric fluxes, although it does not significantly affect the form of the altitude or energy distributions. The effect of this error on the leakage flux calculations [Lingenfelter and Flamm, 1964b] is unknown. Observations by balloon-borne detectors released from Bemidji, Minnesota (X --57øN) by Smith et al. [1962] tend to support the theory, but there is uncertainty of a factor of 5 in the interpretation of the observations because of lack of information about the cutoff rigidity at the time of the flight. Chupp et al. [1967] observed a large neutron flux increase with a moderated borcn tr[fiuoride counter in a rocket flight from a low-!atitude station during the solar-flare event of November 15, 1960. They found that the neutron flux was 10-15 times

2-1 SCIENCE AND INSTRUMENTATION AT THE SECOND TARGET STATION ENSURING US LEADERSHIP IN NEUTRON SCIENCESOak Ridge National Laboratory (ORNL) is a leading center for neutron science worldwide. It has the mission to ensure the United States is served with cutting-edge capabilities for undertaking research that addresses the needs of DOE as well as the broader community. As part of this mission, the Neutron Sciences Directorate has undertaken, in consultation with its sponsors and the research community, an indepth look at the major needs for neutron science and its areas of impact for the next decade and beyond. A central part of this process has been the formation of four high-level workshops to delineate the challenges ahead and the priority areas in which developments in neutron sciences are most needed.

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