Two phosphorous-diffused silicon di

Two phosphorous-diffused silicon diodes were used as small solid-state ionization chambers to map the earth's radiation environment. Counts were accumulated only when the detectors looked within 10 deg of the local magnetic field. The diode used to detect protons was mounted behind a 25-deg half-angle aperture collimator with an entrance aperture of 2-mm diameter. The outer shield was sufficiently massive to exclude protons less than 80 MeV and electrons less than 10 MeV. Magnets surrounding the diode effectively excluded electrons less than 300 keV. The detector responded to protons with energies between 1.8 MeV to 18 MeV, and had three pulse-height discriminator levels corresponding to protons which lost 1.8, 3.2, or 4.7 MeV in the detector. Although the instrument was designed to operate at three different bias modes (120, 20, and 5 V), only the highest returned useful proton data. The other two bias modes served to detect electron contamination of the counting rate. The electron detector, similar to the proton detector, had a collimator with a half-angle of 10 deg, aperture diameter of 2 mm, and sufficient shielding to exclude protons less than 60 MeV and electrons less than 6 MeV. (No magnetic shield was used on the electron detector.) The detection scheme employed pulse-height analysis to discriminate between 0.2- to 0.35-, 0.35- to 0.55-, 0.55- to 0.75-, and 0.75- to 1-MeV electrons. The basic measurement sequence required 12 s. Counts from each detector were accumulated for 10 s. Samples were telemetered each second during the accumulation time. The registers were then frozen, and one redundant reading (the 10th) was telemetered. For protons, this procedure was carried out three times for each bias mode, interspaced by a 12-s allowance for bias change. The entire sequence of three modes required 144 s. For electrons, the sequence was repeated every 12 s. NSSDC has all the data that now exist from this investigation.