Establishment of Ultra-Low Intensity High-Energy Electron Beams for Irradiation and Their Applications

这项工作是在大阪府大学高等科学技术研究所的18 MeV电子直线加速器上进行的。实验中使用的电子束能量约为10 MeV，不会对辐照样品造成严重的激活。为了建立用于辐照的超低强度束流，人们发展了测量束流电子电荷和传输束流的新方法。最终获得的束流最低电荷量为3fC/脉冲，可通过对加速器组件的微小调整而降低。已经建立了聚焦光束和扩展光束的辐照系统。在后一种情况下，辐照样品中的吸收剂量损失小于100μSv。这是首次建立具有这种低强度光束的系统。用于监测个人吸收剂量的热释光剂量计已被电子束辐照，以研究剂量计的特性。并与伽马射线辐照的结果进行了比较。利用该成像板作为高灵敏度剂量计，获得了二维吸收剂量分布。利用安装了模型缺陷的试板，对高能脉冲电子束射线照相技术进行了基础研究。实验结果表明，这些剂量计可用于测量超低强度电子束的剂量和剂量分布，并已用于研究生物效应。本工作开发的新技术有望应用于各个领域的研究。

The present work has been performed by using an 18 MeV electron linear accelerator at Research Institute for Advanced Science and Technology in Osaka Prefecture University. The energies of the electron beam used in the experiments are about 10 MeV, which does not cause serious activation of the irradiated samples. In order to establish ultra-low intensity beams for irradiation, new methods for measuring the electron charge of the beam and for transporting the beams have been developed. The lowest charge of the beam finally achieved is 3 fC/pulse, which can be made lower by small adjustment of the accelerator components. Irradiation systems for focused beams and widely expanded beams have been constructed. In the latter case the absorbed dose in the irradiated sample is loss than 100 μSv. This is the first establishment of the system with such low-intensity beams.The thermoluminescence dosimeter used for monitoring personal absorption doses has been irradiated with the electron beam for investigating the characteristics of the dosimeter. The results have been compared with those obtained by gamma-ray irradiation. Two-dimensional absorbed dose distribution has been obtained by using the imaging plate as high-sensitivity dosimeter. Basic research on radiography with high-energy pulsed electron beams has been made by using a sample plate in which model defects have been installed. The experimental results have indicated that these dosimeters can be used for measuring the dose and the dose distribution of the ultra-low intensity electron beams.The electron beams have been also applied to investigating biological effects. It has to be continued for the further investigation.The new technology developed in the present work is expected to be applied to the researches in a various fields.