STUDY OF SEMICONDUCTOR FAST-NEUTRON DOSIMETER FOR RANGE 0-50, 000 RADS.
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BATTELLE MEMORIAL INST COLUMBUS OHIO
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Results of a study of a semiconductor neutron dosimeter for the range 0 to 50,000 rads are presented. The dosimeter is a wide-base, conductivity-modulated, silicon p-n junction whose forward resistance increases upon exposure to neutrons, because of a decrease in excess carrier lifetime. The relationship between bulk properties of silicon, various processing steps, base width, and forward-current level on dosimeter performance was studied. The results of this study have led to development of an improved device for the required application. Advances in the dosimeter-fabrication process have led to increases in device uniformity. The need for adequate process control to prevent material contamination is emphasized. Lifetime degradation in the completed dosimeter and consequently higher response threshold has been attributed directly to the thermal-diffusion cycle, and a reduction in the temperature and time in this step is suggested to improve the sensitivity at lower neutron fluences. Present dosimeter response is accurate to plus or minus 25 percent at 50 rads tissue and improves rapidly at higher doses to plus or minus 2 percent at 50,000 rads tissue. Long-term annealing effects at room temperature are shown to be negligible for dosimeter application. Author
- Electrical and Electronic Equipment