Radiation Detection

Glass

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Nucsafe’s Guardian Glass is available in various forms, including: fiber, rods, discs, plates and tubes. The glass utilizes the neutron sensitivity of 6Li for the detection of neutrons. The nucleonic detection process is characterized by the6Li absorption of a thermal neutron and generation of an alpha particle and a triton: 6Li +n → α + Triton + 4.8 MeV.

The 4.8 MeV kinetic energy imparted to the alpha and triton excite the Ce3+ in the glass which in turn emits 395-432 nm wave length photons upon returning to the ground state. The efficiency of capture cross section for 6Li is a function of the neutron’s energy. Unlike isotopic gamma signatures that are mono-energetic, the isotopic neutron signatures are a spectrum. The graph below is representative of the 252Cf neutron spectrum response of the Guardian Glass. This graph shows that approximately 92% of the neutrons striking a 3.5 mm thick detector are captured. Most neutron sources have gamma rays associated with their neutron spectrum

This graph shows that approximately 92% of the neutrons striking a 3.5 mm thick detector are captured. Most neutron sources have gamma rays associated with their neutron spectrum

The Guardian Glass neutron detector provides good discrimination against gamma rays. The graph below illustrates the response of a Guardian Glass neutron detector to a 252Cf neutron source and a 60Co gamma ray source.