DEVELOPMENT OF A HIGH-INTENSITY SOLID-STATE GAMMA-RAY DOSIMETER SYSTEM

Design, construction, and testing of an integrating gamma-ray dosimeter for high dose rates are discussed. The sensor is a silicon surface-barrier detector operating as a current device. The detector output current is integrated on a capacitor. When the voltage on the capacitor rises to a predetermined level corresponding to 10 rad-equivalent-air of gamma-ray dose, the capacitor is discharged and the instrument produces an output pulse to signal the event. The number of output pulses indicates integrated dose, and the pulse repetition rate indicates dose rate. The detector proper is cooled with a thermoelectric cooler to minimize and stabilize leakage current. The instrument is designed for operation in the dose-rate range of 10 to 100,000 rad-equivalent-air per second. The detector is constructed to make it function as a Bragg-Gray device over the gamma-ray energy range of 80 kev to 12 Mev. The detector is reasonably isotropic; cumulative errors due to all causes are less than plus or minus 30%. The electronics are insensitive to gamma-radiation transients for dose rates as high as 1,000,000 rad per second. Results of tests with radioactive sources, a fast-burst reactor, and bremsstrahlung pulses are given. (Author)