A Measurement of the Response to Fast Neutrons of Several Materials Dosemeters

• Published in: Radiation protection dosimetry 1986-12, Vol.17 (1-4), p.123-126
• Main Authors: Jones, L.T., Kitching, S.J., Lewis, T.A., Playle, T.S.
• Format: Article
• Language: English
• ISSN: 0144-8420; 1742-3406
• DOI: 10.1093/oxfordjournals.rpd.a079791

The measurement of the response to fast neutrons of several materials dosemeters, used in zero energy reactor experiments, is described. They are (a) silicon diodes, (b) beryllia, alumina and calcium fluoride TLDs, and (c) C/CO2 and C/Ar ionisation chambers. Silicon diodes are used for measuring fast neutrons whereas the others are used to measure ? exposure where the fast neutron response is typically less than 5% of the total signal, the demand for absolute accuracy is not high: the main requirement is that the calibration source of neutrons be free from ? radiation. For silicon diodes, ? radiation is irrelevant since they respond only to fast neutrons, but the response must be defined accurately since ultimately it represents the limit of precision. Also the response function has several resonances so that the calibration must be with a variable but essentially monoenergetic neutron source. Between 0.3 and 2.3 MeV the requirements for both classes of detector can be met simultaneously by accelerating protons onto a tritium target to produce ? free neutrons in defined energy bands. This was used for all devices. In addition, a thin lithium target was also used to produce more closely defined neutron energies in the range between 117 and 650 keV to identify the response threshold and principal resonance in the silicon diode response. This target was unsuitable for the other devices because of the ? radiation produced.