PROBLEM TO BE SOLVED: To provide an art improving the uniformity of a dose rate of radiation to be irradiated to a non-irradiation object on a tray without adversely affecting an object to be irradiated by reducing the non-uniformity of the dose distribution in the radiation field of an radiation irradiation apparatus.SOLUTION: The shape of an X-ray filter to be applied is formed according to a dose distribution in a radiation field that has a high dose rate at a ray central portion and becomes lower as approaching to a perimeter. In concrete terms, the X-ray filter is so formed that the thickness is formed thick near the X-ray center and formed thinner towards the perimeter of the radiation field.COPYRIGHT: (C)2010,JPO&INPIT【課題】放射線照射装置の照射野内の線量分布の不均一を低減し、被照射物に悪影響を与えずにトレイ上の非照射物体に照射される放射線の線量率の均一度を向上させる技術を提供する。【解決手段】線中心部分の線量が高く周辺に近づくほど線量が低くなる傾向にある照射野内の線量分布状態に合わせて付加するX線フィルタの形状を形成する。具体的には、X線フィルタの形状を、X線中心付近の厚みを厚くし、照射野周辺に向かって薄くなるよう形成する。【選択図】図4
