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

利用该助学金研制的射频氚等离子体反应堆，定量研究了反应器内不同位置的再沉积石墨的量、再沉积石墨中的氢气捕获量以及各种等离子体参数。观察到了以下结果1.在远离电极的位置，衬底上沉积的石墨较多。在远离电极的位置，从衬底上形成的石墨再沉积层中回收了更多的氘。用朗缪尔探头测得的电子温度约为3 eV，偏压约为10 eV.上述观察结果表明，由于偏置电压的作用，当衬底放置在电极上时，重新沉积的石墨发生了刻蚀。还观察到，本研究得到的D/C比约为0.03，远小于D被C-H键捕获时的值。这项研究中的观察表明，如果等离子体温度很低，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.