Tooth enamel EPR dosimetry of neutrons: Enhancement of the apparent sensitivity at irradiation in the human head phantom

Induction of the EPR signal in tooth enamel at irradiation by the neutrons produced by a generator with maximal energy of 0.8 MeV in the air and in the human head phantom was investigated. Neutron and photon tissue absorbed doses in the mixed radiation field were determined experimentally and calculated using the Monte-Carlo method. It is shown that the EPR signal response of enamel to neutrons relative to the tissue dose is (2±2)%(2±2)% of the appropriate value for 60Co gamma radiation. At irradiation in the human head phantom, the EPR signal response relatively to the input neutron tissue dose near the surface of the phantom (apparent EPR sensitivity to neutrons) increases to (14±1)%(14±1)%. The observed EPR signal enhancement is caused by absorption in enamel of the secondary photons produced at H(n,γ)H2H(n,γ)H2, Eγ=2.23MeV reaction in the material of the phantom.