Development of Neutron Dosimetry Technique Based on Resonant Laser Ablation with Tunable Diode Laser

本研究旨在发展具有超高灵敏度和良好元素选择性的共振电离光谱（RIS）技术在中子核反应中痕量元素浓度和同位素比值测量的创新技术，以及在核工程中的新应用。特别是，我们建议充分利用“共振激光磨蚀（RLA）”，它将激光烧蚀和RIS同时结合在一起。为此，我们的研究对象大致分为两类；一个是通过实验了解RLA现象的基本过程，建立RLA的理论模型；另一个是利用可调谐二极管激光器开发适合工程应用的RLA分析系统，特别是用于中子剂量测定。主要研究结果总结如下：(1)系统地获得了核材料中几种元素RLA现象的基本实验数据库。(2)建立了可定量再现实验结果的RLA理论模型。在此理论计算的基础上，建立了寻找探测感兴趣元素的最佳激光功率条件的方法。(3)通过对14MeV中子重辐照铝样品中^<27>Al (n, 2n) ^<26>Al反应的基础实验，证明了RLA作为一种新的中子剂量学技术的适用性。(4)获得了一些有益的发现，使可调谐二极管激光器和四极杆质谱仪组成的RLA分析系统的基本设计适合工程应用，并明确了有待解决的一些技术问题。

The present study is aiming at the development of innovative technique to measure the concentration and/or isotopic ratio of trace elements produced by nuclear reactions with neutrons and new application to nuclear engineering by using Resonant Ionization Spectroscopy (RIS), which has fundamental features of ultra high sensitivity and good elemental selectivity. In particular, we propose to make good use of 'Resonant Laser Abration (RLA)', which combines laser ablation and RIS simultaneously with a single laser. For this purpose, our research subjects are roughly classified into two categories ; one is to understand the basic process of RLA phenomena experimentally and to establish a theoretical model for RLA, and the other is to develop an RLA analytical system with a tunable diode laser, which would be suitable for engineering application, in particular for neutron dosimetry.The main results are summarized as follows ;(1) The basic experimental data base has been systematically obtained for RLA phenomena on several elements of nuclear nuaterials.(2) The theoretical model for RLA has been successfully developed to reproduce the experimental resuls quantitatively. Based on this theoretical calculation, the methodology was established to search an optimal condition on laser power for detection of an element of interest.(3) Through basic experiments to detect ^<27>Al (n, 2n) ^<26>Al reaction in an Al sample which was heavily irradiated by 14MeV neutrons, the applicability of RLA has been demonstrated as new neutron dosimetry technique.(4) Some useful findings have been obtained to make basic design of an RLA analytical system with a tunable diode laser and a quadrupole mass spectrometer suitable for engineering application, and athe technical problems to be solved have been also made clear.