Design of a Low Energy Proton Spectrometer

An instrument was designed to detect and analyze protons of energy between 100 keV and 6 MeV. Two totally depleted surface barrier detectors are used in an anticoincidence mode. Electronic logic (anti-coincidence) allows pulse height analysis only of a pulse from the first detector which is unaccompanied by a pulse from the second. The front detector is specially made with an extra thick film of aluminum coating in order to permit operation with the sun in the field of view. Sweeping magnets discriminate against electrons that might give erroneous pulses. A micro C Am 241 radioactive source is mounted on a rotary solenoid which swings into view automatically to put the instrument into a calibration made at preset intervals. Five instruments were made to be flown on satellites and one for back-up. One instrument has just flown on S3-2 satellite, two to be flown on S3-3 and two more on SOLRAD-HI A and B satellites.