Photostimulable phosphors for neutron imaging

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As new photostimulable phosphors with low gamma-ray sensitivities, SrBPO5:Eu, SrBPO5:Ce, and CaBPO5:Ce based phosphors have been prepared and their photostimulated luminescence (PSL) characteristics by neutron irradiation were investigated. The PSL peak of SrBPO5:Eu was about 390 nm due to 5d-4f transition of Eu^<2+>. The PSL intensity was linearly dependent on E^<-1/2>, where E is neutron energy. The S_γ/S_n ratio of SrBPO_5:Eu phosphor was one order magnitudes lower than that of commercially available neutron imaging plates (NIPs), where S_n and S_γ are neutron and gamma-ray sensitivities, respectively. A collimated neutron beam image was obtained with a spatial resolution of 0.4 mm. The PSL characteristics of SrBPO5:Ce and CaBPO5:Ce were almost the same as those of SrBPO5:Eu. The peak and lifetime of PSL of these phosphors was 340nm and 23.5 ns, respectively. Moreover, the PSL intensity was significantly increased by introducing fluorine atoms. The detective quantum efficiency (DQE) of SrBPO5:Eu and CaBPO5:Ce can be more than 40 %, while that of commercially NIPS was less than 40%. Since the PSL peak of SrBPO5:Eu was the same as that of commercially NIPs, new NIPs made of SrBPO5:Eu was made and the image of imaging subjects was clearly obtained by using a conventional reader. The spatial resolution was 0.3 mm and the gamma-ray discrimination ability was better than that of commercially NIPs.