Refer to Guide E844 for the selection, irradiation, and quality control of neutron dosimeters.
Refer to Practice E261 for a general discussion of the measurement of fast neutron fluence rate with threshold detectors. The general shape of the 63Cu(n,α)60Co cross section is also shown in Fig. 1 (3, 4) along with a comparison to the current experimental databse (5). This figure is for illustrative purposes only to indicate the range of response of the 63Cu(n,α) reaction. Refer to Guide E1018 for descriptions of recommended tabulated dosimetry cross sections.
Note 1—The cross section appropriate for use under this standard is ENDF/B-VI release 8 library since it contains a covariance matrix. The ENDF/B-VII library has been released, but it does not contain a covariance matrix for this reaction. For dosimetry applications, an uncertainty metric expressed as a covariance matrix is required. See Guide E1018.
The chief advantages of copper for measuring fast-neutron fluence rate are that it has good strength, is easily fabricated, has excellent corrosion resistance, has a melting temperature of 1083°C, and can be obtained pure. The half-life of 60Co is long and its decay scheme is simple and well known.
The disadvantages of copper for measuring fast neutron fluence rate are the high reaction apparent threshold of 5 MeV, the possible interference from cobalt impurity (>1 μg/g), the reported possible thermal component of the (n,α) reaction, and the possibly significant cross sections for thermal neutrons for 63Cu and 60Co (that is 4.50 and 2.0 barns, respectively),(6) which will require burnout corrections at high fluences.