プラズマ診断は，プラズマプロセス中の荷電粒子の役割を理解する上で重要である．しかしながら，一般的なプラズマ診断は低圧の場合に限られているため，大気圧プラズマの特性を把握するためには新たな診断技術の開発が必要である．本論文では，ゲルディエンコンデンサーを用いた大気圧プラズマ診断を提案し，実用上十分な性能を有すことを実証した内容について報告している．さらに測定に影響を及ぼす要因についても調査した. / Plasma diagnostics plays an important part in understanding the role of charged particles during plasma processes. However, since common plasma diagnostic techniques are limited to low-pressure case, there is a need for the development of a new diagnostic method specifically for atmospheric pressure plasma characterization. In this dissertation, a diagnostic technique based on the Gerdien condenser theory is developed for laboratory-produced atmospheric pressure plasma. The Gerdien condenser, which is a classical instrument employed in atmospheric science, is capable in measuring the ion mobility and density from an obtained current-voltage characteristic. The factors that can affect the measurements are also investigated. / 博士(工学) / Doctor of Philosophy in Engineering / 同志社大学 / Doshisha University

The doctoral thesis presents methods for low-level measurements, which are exemplified by the general measurement of air ion concentration. Within the first section, the author progressively identifies certain critical effects influencing the concentration of air ions, and these effects are to be considered in evaluating the uncertainty of the measured concentrations. Thus, the thesis aims to provide a systematic description of the procedures and requirements related to low-level measurements; the proposed description then involves a discussion of the process reliability requirements, namely the factors of repeatability, elimination of errors, and definition and describability of measurement uncertainties. Such methodology facilitates, among other activities, the long-term monitoring of air ion concentration in extreme environments, including caves or spaces characterized by high temperatures and humidity. The use of common methods for determining the air ion mobility spectrum is accompanied by a number of disturbing effects, such as spurious fluctuation in the concentration of air ions in time. The experimental section of the thesis describes the testing of different configurations of the measuring device (a collecting electrode and a polarization capacitor); at this stage, we seek the most advantageous distribution of the electrostatic field in the sensor – a Gerdien tube. The systematic suppression of the influence of spurious fluctuations in air ion concentration during the measurement of saturation characteristics is carried out with the least-squares numerical method (as a supporting element), a hybrid technique to describe and evaluate the experimental model. In the second part of the thesis, the methodology of low-level measurement is complemented with procedures for the measurement of freezing potential. This latter domain, as an overall experimental approach applicable during phase changes of the sample, has hitherto not been sufficiently characterized from the metrological perspective, in an up-to-date manner; several subregions of the said domain remain somewhat obscured and deserve significantly more attention. In the given context, this thesis systematically considers a problem where comparable measurement results produced by multiple authors are not available. The measuring methodology proposed herein was utilized in applied research to facilitate the fabrication of an apparatus for the experimental measurement of freezing potential in pre-defined samples; the obtained results then lead us to conclusions with respect to the evaluation of effects that cause differences in the measured data, and the results can be further compared with those obtained by other researchers investigating the given segment of the problem.