A high-sensitivity portable spectrometer for ESR dosimetry

A portable ESR spectrometer using the permanent magnet, NEOMAX (Nd---B---Fe), has been developed to detect 2 × 1010 spins/0.1 mT by further improvements of the magnet, microwave and electric systems from previous spectrometer (SPIN-XX). The thermal stability of the NEOMAX was improved from 1200 ppm/°C to 35 ppm/°C. The magnetic circuit and a ceramic cavity are described with the applications to radiation dosimetry using an alanine dosimeter irradiated at CERN, a shell button for accident dosimetry and to dating of aragonitic corals.