INVESTIGATION OF A FAST NEUTRON MONITORING SYSTEM USING SEMICONDUCTOR DETECTORS.
Abstract
Recommendations have been made for a solid state neutron monitor of maximum radiation endurance based on the use of low resistivity silicon counting diodes. Shallow diffused diodes of 10-20 ohm-cm p base silicon were used to obtain fission fragment spectra in-core after exposure to 4.6 x 10 to the 15th power nvt (greater than power 10 kev). Bias levels were 25 v maximum initially and 45 v maximum finally. Features of the radiation degradation were (a) a large increase in leakage current to greater than 100 microamperes, (b) a large decrease in a charge collection efficiency (about a factor of ten), (c) an improvement in ability to sustain bias without breakdown noise, and (d) a decrease in capacity. A voltage sensitive preamplifier based on an integrated circuit amplifier was used. It was designed also for radiation endurance and was virtually unaffected by exposure to 3 x 10 to the 13 power nvt. A number of preliminary measurements are reported using electron-irradiated low resistivity silicon solar cells as counters and californium 252 as a source of fission fragments. These experiments served to confirm the expected nature of the damage, and showed the lack of sensitivity to gamma background and to temperature changes. One diode each of GaAs and SiC were included in the first reactor tests but the good silicon results preempted any further work with other diodes.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1966
- Accession Number
- AD0487610
Entities
People
- Lawrence M. Epstein
- Richard R. Ferber