Solar Gamma-Ray Monitor

Description

This University of New Hampshire experiment monitored the solar high-energy photon (gamma-ray) spectrum from 0.3 to 10.0 MeV for intensity, time variation, and possible line emission, particularly during flares. In addition, special attention was paid to lines at 0.51 MeV, 2.22 MeV, 4.43 MeV, and 6.14 MeV, which indicate the production of positrons, neutrons, and excited nuclei in the solar atmosphere. The instrumentation consisted of a high-resolution, gamma-ray scintillation spectrometer mounted in the wheel section. The detector was a NaI(Tl) scintillation crystal viewed by a photomultiplier. It was surrounded by a CsI(Na) anticoincidence shield and photomultiplier array, which also provided directional sensitivity. Gamma rays were detected in 377 energy channels from 0.3 to 9.5 MeV by a pulse-height analyzer. For correlation purposes in the data analysis, a secondary system made up of a thin NaI(Tl) scintillation crystal and a photomultiplier was used for detecting X-rays from 7.5 to 120 keV. X-ray pulses were divided by a four-channel pulse-height analyzer. High-energy solar neutrons (energies greater than 30 MeV) could be identified from a study of the large energy loss events in the central detector, and their correlation was provided with a gain-change attenuator that could be controlled from the ground. For more details, see P. R. Hignie et al., IEEE Trans. Nucl. Sci., v. NS-19, p. 606, 1972.