Determination of the excited states of the electron centers and recording-readout processes in the X-ray storage material BaFBr

X射线存储材料BaFBr中电子中心激发态和记录读出过程的测定

• 批准号: 09450002
• 负责人: KONDO Yasuhiro
• 金额: $ 3.65万
• 依托单位: Tohoku University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 1997
• 资助国家: 日本
• 起止时间: 1997 至 1998
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09450002/
• 关键词: X-ray Imaging; Imaging Plate; Photo-Stimulated Luminescence; Phosphors; Luminescence; Electron trap centers; 2-D detectors; Detectior of InfraRed Light; 二次元検出器; 画像記録; X線; イオン結晶; 色中心; 発光分光; 励起状態; 赤外分光; 光物性

In the storage phosphor of the X-ray image material, the X-ray photons generate electrons and holes which are trapped at vacancies and Eu^<++> impurities in the micro crystals ofBaFBr : Eu^<++>(storage process) and photoexcitation of the trapped electron induces the recombination of the electrons and holes at Eu impurity, emitting the uv-luminescence. This uv-luminescence is recorded and is used to construct the X-ray image (readout process). Although the storage-readout mechanism described above has been proposed in the early stage of the invention of the imaging plate, the storage-readout process is still controversial at present. To establish the clear model for the mechanism, I tried to measured thermal stability of the excited state of the trapped electrons and also to clarify the recombination path of the electrons and holes. For this measurements, a system for the infrared luminescence was constructed. Results are summerized as follows.1) The temperature dependence of the luminescence intensity and its lifetime of the F center were measured and the thermal activation energy of the F centers in the excited state was obtained. This mechanism is identical to the that proposed by Takahashi.2) The F(F^-)-center luminescence in the IP was measured for the first time and it is also shown that F(Br^-) center does not emit any IR luminescence. These results shows that the electron center can migrate in the micro crystals in the IP and that the fading of the stored image might be induced by the migration of holes which are thermally activated in shallowly trapped hole centers.

In the storage phosphor of the X-ray image material, the X-ray photons generate electrons and holes which are trapped at vacancies and Eu^<++> impurities in the micro crystals ofBaFBr : Eu^<++>(storage process) and photoexcitation of the trapped electron induces the recombination of the electrons and holes at Eu impurity, emitting the uv-luminescence.记录了这种UV亮度，并用于构建X射线图像（读取过程）。尽管上述的存储阅读机制是在成像板发明的早期阶段提出的，但目前仍存在争议的存储阅读过程。为了建立机制的清晰模型，我试图测量被困电子激发态的热稳定性，并阐明电子和孔的重组路径。对于此测量，构建了红外发光的系统。结果如下。1）测量发光强度的温度依赖性及其在F中心的寿命，并获得了激发态下F中心的热激活能。该机制与高桥提出的相同。2）首次测量IP中的F（f^ - ） - 中心发光，还表明F（Br^ - ）中心没有发出任何IR发光。这些结果表明，电子中心可以在IP中的微晶体中迁移，并且在浅水捕获的孔中心中热激活的孔的迁移可能会引起存储图像的褪色。

项目成果

Yasuhiro Kondo, Kiyoshi Inoue, and Nobufumi Mori: "Luminuescence Study of F(Br-) and F(F-) Centres in BaFBr" Radiation Effects and Defects in Solids. 147(印刷中). (1999)

Yasuhiro Kondo、Kiyoshi Inoue 和 Nobufumi Mori：“BaFBr 中 F(Br-) 和 F(F-) 中心的发光研究”固体中的辐射效应和缺陷（1999 年）。

Yasuhiro Kondo, Kiyoshi Inoue, and Nobufumi Mori: "Luminescence Study of F (Br-) and F (F-) Centres in BaFBr" Radiation Effects and Defects in Solids. Vol.147 (in press). (1999)

Yasuhiro Kondo、Kiyoshi Inoue 和 Nobufumi Mori：“BaFBr 中 F (Br-) 和 F (F-) 中心的发光研究”固体中的辐射效应和缺陷。