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Abstract: A PACVD apparatus was designed and fabricated at Shizuoka University in order to prepare high-pure boron coating films. In the present study, some parameters, especially feeding gas concentration, substrate temperature and CVD input power, have been optimized to prepare pure boron coating films. It was found that the purity of boron coating film was controlled by the decaborane concentration of feeding gas and substrate temperature during the PACVD process, and each optimized values were 0.4 and 473K, respectively. The atomic composition of boron in the boron coating film under the optimized condition has been achieved to be 0.94. [Copyright &y& Elsevier]

Abstract: TDS analyses have been performed in order to examine helium irradiation effects for deuterium retention in boron coating films prepared by PACVD. It is clarified that the deuterium retention is reduced due to the irradiation prior to deuterium. There is no correlation between the retention variations of deuterium and helium, and thus the helium occupation seems hardly to contribute to the reduction. The third peaks in the TDS spectra shift on the high temperature side with the irradiation fluence. It is presumed that helium irradiation forms certain layers by knocking on boron atoms, in which deuterium retention is partly restricted, and trapped deuterium needs higher energy for the desorption. [Copyright &y& Elsevier]

Abstract: Depth profile and retention properties of hydrogen in the graphite armor tiles of JT-60 open-divertor used for HH discharge period were investigated by secondary ion mass spectroscopy and thermal desorption spectroscopy. Two tiles were investigated, one at the inner divertor area covered with the re-deposited layers of the largest thickness (70μm) and the other at the private flux region near the outer divertor striking point hardly covered with the re-deposited layers (only 1–2μm). In the former, hydrogen was retained uniformly in the carbon re-deposited layers with H/C of 0.03, which was significantly smaller than H/C observed in the re-deposited layers of other tokamaks. Such small hydrogen retention in the re-deposited layers is attributed to the temperature rise of the re-deposited layers during discharges due to their poor thermal contact to the substrate. The latter retained rather large amount of hydrogen only in the shallow surface layers and its depth profile decayed sharply to 1.3×10−4 in H/C of the bulk retention as expected from the very thin re-deposited layers and observed temperature rise above 900K. [Copyright &y& Elsevier]

Abstract: Retention profiles of hydrogen and deuterium in graphite tiles placed in the inner divertor region of JT-60U were analyzed by secondary ion mass spectroscopy (SIMS) and thermal desorption spectroscopy (TDS). The difference in hydrogen and deuterium retention behaviour is discussed considering the frequency of the strike-point hit and history of NBI heating power. It was found that most of hydrogen/deuterium was retained in the deposited layers, HH deposition layers/DD deposition layers or co-deposited with carbon. Owing to the higher heating power of DD discharges, the deuterium concentration in the DD deposition layers was much lower than that of hydrogen in the HH deposition layers. On the area showing no deposition, very shallow profile of deuterium dominated hydrogen profile. These results indicate that the tritium retention is strongly influenced by the history of discharge and temperatures. Tritium retention on graphite tiles and deposition layers could be significantly reduced with increasing the operation temperature. [Copyright &y& Elsevier]