Mechanism of Oxygen Effect on Solid State Nuclear Track Detectors

氧对固态核径迹探测器的影响机制

基本信息

批准号：
02680185
负责人：
MIYAKE Hiroshi
金额：
$ 1.28万
依托单位：
Kobe University of Mercantile Marine
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1990
资助国家：
日本
起止时间：
1990 至 1991
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-02680185/
关键词：
Track Detector Oxygen Effect Latent Track CR-39 Dissolved-Oxygen Concentration Diffusion Coeffcient Life Time of Radicals

项目摘要

Solid state nuclear track detectors, especially CR-39 plastic ones, are a useful tool to detect heavy charged particles and applied to many fields, such as radiation protection measurements, nuclear fusion study, space science, etc. However, the storage of these detectors in vacuum causes severe effects on the registration sensitivity. The oxygen dissolved in a detector plays an important role in the latent track formation. The purpose of this project is to clarify the mechanism of the "Oxygen Effect" and to develop improved detectors.The oxygen concentration and the diffusion coefficient in CR-39 plastic were measured, and the relation between the oxygen concentration and the sensitivity of the detector was ascertained. Outgas rates of oxygen and some other components from CR-39 sheets commercially available were measured at room temperature with a quadrupole mass specrometer. Diffusion coefficients and oxygen concentrations dissolved at atmospheric pressure were evaluated to be(4-9)x10^<-9>cm^2/sec and(1-8)x10^<19>molecules/cm^3, respectively. The reduction rates of etch rate ratios through the storage in vacuum were given by a function of local pressures of oxygen dissolved in CR-39. These results supported the "oxygen setting model", quantitatively.The life time of the radicals formed by alpha-particle irradiation in the sufficiently outgassed CR-39 was evaluated on the basis of the examination for etch pit recovery in radius due to the air exposure after the storage in vacuum. Radicals with a life time of about 40 minutes were found to be formed as well as radicals with a life time of less than a few minutes after irradiation. It was also found that the fractions of radicals with different life times depended on the lots of CR-39, the time of storage after production and the energy of incident particles.

固态核径迹探测器，特别是CR-39塑料探测器，是探测重带电粒子的有用工具，应用于许多领域，如辐射防护测量、核聚变研究、空间科学等。然而，这些探测器的存储在真空中会对配准灵敏度造成严重影响。溶解在检测器中的氧气在潜迹形成中起着重要作用。该项目的目的是阐明“氧效应”的机理并开发改进的探测器。测量了CR-39塑料中的氧浓度和扩散系数，以及氧浓度与探测器灵敏度之间的关系被确定。使用四极杆质谱仪在室温下测量市售 CR-39 片材中氧气和一些其他成分的脱气速率。扩散系数和在大气压下溶解的氧浓度分别评估为(4-9)x10^-9cm^2/秒和(1-8)x10^19分子/cm^3。通过真空储存的蚀刻速率比的降低速率由溶解在CR-39中的氧的局部压力的函数给出。这些结果定量地支持了“氧设定模型”。在充分除气的 CR-39 中通过 α 粒子照射形成的自由基的寿命是根据由于空气暴露而导致的半径中的蚀刻坑恢复的检查来评估的。真空保存后。发现在照射后形成了寿命约为40分钟的自由基以及寿命小于几分钟的自由基。研究还发现，不同寿命自由基的比例取决于CR-39的批次、生产后的储存时间和入射粒子的能量。