An optical self-powered neutron detector using nuclear pumping

Based on the nuclear pumped laser technique, an optical self-powered neutron detector is now being investigated, in the JAERI Advanced Science Research Center. The first experiment has been made using lasing gas cells with three components of He-3 gas (1140 mmHg), Ne gas (588 mmHg) and H₂ gas (206 mmHg or 412 mmHg), or Ar gas (206 mmHg) instead of H₂ gas in a thermal neutron flux of about 10⁹n/cm² sec. For this irradiation, optical light of 585.3 nm from the transition of Ne 3P₁→3S₂ has been observed clearly from those gas cells. The optical light output was increased according to the reactor power and the measurement of the optical attenuation coefficient of 585.3 nm in this gas has been made and is found to decrease for increasing neutron flux. From these results, the nuclear pumped laser can be expected to be in operation above a neutron flux of 10¹¹n/cm²·sec. The second experiment is now under preparation