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

本研究的目的是发展测量中子核反应产生的痕量元素的浓度和/或同位素比的创新技术，以及利用共振电离光谱（RIS）在核工程中的新应用，其具有超高灵敏度和良好的元素选择性的基本特征。特别是，我们建议充分利用“共振激光烧蚀（RLA）”，它结合了激光烧蚀和RIS同时与一个单一的激光。为此，我们的研究课题大致分为两类：一类是从实验上了解RLA现象的基本过程，建立RLA的理论模型;另一类是研制一种适合于工程应用的可调谐二极管激光器RLA分析系统，特别是用于中子剂量学的分析系统。（1）系统地获得了几种核材料元素RLA现象的基本实验数据库。(2)建立了RLA的理论模型，定量地再现了实验结果。在此理论计算的基础上，建立了一种方法，以寻找一个最佳的条件下，激光功率检测的一个感兴趣的元素。(3)通过对14 MeV中子强辐照Al样品中的^<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可行性。(4)为可调谐半导体激光器-四极质谱计RLA分析系统的工程应用奠定了基础，明确了需要解决的技术问题。

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.