Trapping Phenomena of Tritium at Formation of Re-deposition Layer of Diverter Graphite

本研究利用本研究资助项目研制的射频氘等离子体反应器，对反应器中各位置的石墨再沉积量、再沉积石墨上捕获的氘量以及各等离子体参数进行了量化。观察到以下结果。在远离电极的位置，基底上沉积了更多的石墨。在远离电极位置的衬底上形成的石墨再沉积层中回收了更多的氘。Langmuir探针测得的电子温度约为3ev，偏置电压约为10ev。以上观察结果表明，由于偏置电压，当衬底放置在电极上时，会发生再沉积石墨的蚀刻。还可以观察到，本研究得到的D/C比值约为0.03，远小于D被C- h键捕获时的值。本研究的观察结果表明，如果等离子体温度较低，氚可能不会被C-H键捕获。

Using the RF deuterium plasma reactor made by this Grant-in-Aid, the amount of graphite re-deposited at the various position in the reactor, the amount of deuterium trapped to the re-deposited graphite and various plasma parameters were quantified in this study. The following results have been observed.1. More amount of graphite deposits on the substrate placed at the position far from the electrode.2. More amount of deuterium is recovered from the re-deposited layer of graphite formed on the substrate placed on the position far from the electrode.3. The electron temperature measured with a Langmuir probe is around 3 eV, and the bias voltage is around 10 eV.4. Above observations imply that etching of re-deposited graphite occur when the substrate is placed on the electrode because of the bias voltage.5. It is also observed that the D/C ratio obtained in this study, about 0.03, is far smaller from the value when D is trapped by C-H bonding. The observation in this study implies that tritium may not be trapped by the C-H bonding if the plasma temperature is low as used in this study.