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This paper reports on a glass microdevice with a new patterned nanoparticle composite resin that detects and discriminates all species of radiation emitted from fissionable bombmaking materials. Tailored charge conversion nanoparticles doped into a fast-electron scintillating resin produce different optical pulses specific to the radiation species. These pulses exit since the nanoparticles are appreciably smaller than the wavelength of light. The resins are integrated into a glass substrate where deep cavities are made using microsandblasting, forming independent optical paths leading to fiber-optic attachments. Separate off-the-shelf photomultiplier tubes measure the light pulses. The beta detector was tested with a 90Sr source which produced 1470 cpm with the doped scintillator, while the same source produced 1500 cpm with an off-the-shelf Geiger counter. An Am/Be neutron source was used to test Gd-loaded detectors which exhibited an increase in count rates with an increase in Gd loading. The different nanoparticles used convert differing radiation species into electrons through independent physical mechanisms, including charge conversion (alpha), secondary electron (beta), photoelectron (gamma/X-rays), and an on-chip thermonuclear fusion reaction (neutron) to evaluate the specific isotope radiation signature. The four different detectors use four different methods to convert four different types of radiation into electrons; as a consequence, the measured pulses are characteristic to the radiation, allowing pulse height spectroscopy to be used.
Date of Publication: Oct. 2010