Miwa Okumura

Luminescence Properties of Rare Earth Ion-Doped Monoclinic Yttrium Sesquioxide.

Monoclinic Y2O3 phosphors doped with Eu3+ or Pr3+ are obtained for the first time by treatments in inductively-coupled thermal plasma. This paper reports the luminescence properties of these phosphor materials. The assumption proposed earlier by the authors, that the emitting levels of Pr3+ in Gd2O3 are determined by the distance between the Pr3+ ion and the surrounding oxygen ligands, is found consistent even when the monoclinic Y2O3:Pr and other oxides are included.

Preparation of spherical phosphors by thermal‐plasma treatment

Garnet-structured rare-earth oxysulfide and zinc sulfide phosphors were treated by thermal plasma in order to obtain spherically shaped phosphor particles. Although spherical particles of garnet phosphor and rare-earth oxysulfide phosphor were obtained, their luminescence properties were lowered. However, the properties could be partially restored by optimized heat treatment.

Development of x-ray detector for multislice CT with 0.5-mm slice thickness and 0.5-second revolution

The purpose of this study is to develop an x-ray detector system for multislice CTs with 0.5 slice thickness and 0.5- second revolution, and to evaluate clinical advantages. The detector adopts a newly developed ceramic scintillator having a high light-output efficiency as well as a high light-transmittance. By employing high precision machining technology to fabricate the detector, it is not necessary to mask the gap from incident x-ray in the longitudinal direction between neighboring cells. The scintillator properties and the geometry of the detector provide a high x-ray-to-light conversion efficiency, and realize a good low-contrast detectability for CTs. The detector structure allows 0.5 mm slice thickness. The afterglow intensity of the scintaillator is less than 0.1 percent at 3 ms, facilitating 1800 views per second for 0.5-second revolution. This detector improves the performance of CT scanners.