Response of MNOS Devices to Neutrons and Gamma Rays.
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OHIO SCHOOL OF ENGINEERING
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Metal-Nitride-Oxide-Semiconductor MNOS transistors were evaluated as radiation dosimeters in the neutron-gamma radiation field of a nuclear reactor as compared to their behavior when exposed to gamma rays from a calibrated 60Co source at 40.3 krads Si per hour. Their response to gamma rays confirmed the results of a previous study which showed that the change in the threshold voltage for conduction, Delta V sub I. For gamma irradiation, Delta V sub TMAX approaches about 5 volts at an exposure of about 4 Mrads Si. Response to reactor radiation follows the same relation except for an anomalous increase of approx. 20 in Delta V sub TMAX. When shielded with cadmium, Delta V sub T upon repeated irradiation is reproducible within 2 for four runs. When unshielded, a small parallel offset in Delta V sub T results. The devices have survived neutron fluences of 1.9 10 to the 16th power sq cm. After irradiation in the reactor, the responses of two devices to gamma rays were within 5 of pre-irradiation values. A simple schematic is given for the testing circuit along with procedures to follow to determine gamma ray doses from the MNOS device.
- Nuclear Instrumentation