Experiment of D-T neutron induced luminescence on window materials

A photon measurement system has been developed to analyze wavelength spectra of photons emitted from window material during D-T neutron irradiation, and the system consisted of a sample holder, a radiation-resistant optical fiber, a polychromator system and other electronic devices. High-purity silica glass, synthesized quartz and other optical materials were irradiated with D-T neutrons. The luminescence spectrum of the silica glass had a large peak around 450 nm, which was concerned with decay of self-trapped excitons in oxygen vacancies. The intensity of photon emission was proportional to the D-T neutron flux, though the neutron fluence was too low to damage the sample. 60Co γ-ray irradiation experiments were also performed with the same photon measurement system. The luminescence efficiency for D-T neutrons has been found to be 5±3 photons MeV−1 in visible range, while that for 60Co γ-rays to be 135±50 photons MeV−1. These data and the related discussions should be useful for the estimation of the photon-noise level on optical windows used for fusion plasma diagnostic systems.