EOSCOR III, a high energy solar neutron detector.

A lightweight high energy neutron detector has been developed for the observation of 20-150 MeV solar flare neutrons on a long duration Sky Anchor balloon flight. It consists of two 1-sq-m plastic scintillators separated by a 1 m time-of-flight path to detect the protons from n-p scattering and C-12(n, pX) interactions in the upper scintillator. Adiabatic isochronous light pipes view the scintillators. Time-of-flight and pulse height analysis are used to measure the proton velocity, to discriminate against albedo events, and to separate the slower moving protons from Compton electrons. The Monte Carlo efficiency calculations are compared with accelerator calibration results using mono-energetic neutrons. Some results from short duration high altitude balloon observations are presented.