Tritium retention and erosion/deposition of first wall materials

本文研究了JT-60 U中氢同位素（H、D和I）的保留和在等离子体对碳材料中的侵蚀/沉积以及尘埃取样，并与JET的结果进行了比较。在JT-60 U等D-D放电装置中，由D-D反应产生的氚并没有完全失去其初始能量1 MeV，而是注入到等离子体对面壁面中超过1μm的深度。因此，氚保留曲线与碳沉积曲线分离。另一方面，在JT-60 U中，分流器区域中的H+D保留曲线与碳沉积曲线良好相关，并且沉积主导的内部分流器瓦显示出高保留，而侵蚀主导的外部分流器瓦显示出低保留。然而，在再沉积层中的保留量小于在JET中观察到的那些，这归因于再沉积层的温度升高，这可能是由于它们与衬底的热接触不良。等离子体上的碳沉积阴影 ...更多信息 区域和偏远地区，如抽水管道，是非常小的，只有少量的灰尘收集。JT-60 U中偏远区域的低沉积可归因于分流瓦的环形和极环形精确对准。偏滤器的几何形状对碳沉积和碳输运有很大的影响。本文还研究了JT-60开口偏滤器上共沉积层的脉冲激光诱导脱附。采用20 ps Nd：YAG激光器的基波（1064 nm）和四次谐波（266 nm）发射，研究了激光强度IL和波长λ对氢解吸的影响。氢脱附效率是指激光照射后脱附的氢数与烧蚀后保留的氢数之比，在C+发生强电离的区域，脱附效率最大，且在λ = 266 nm时激光光子可以切断C-H键，与λ=1064 nm时相比，脱附效率更大。对于氢的烧蚀去除，短波长和高功率的激光器是理想的。少

Retention of hydrogen isotopes (H, D, and 1) and erosion/deposition in plasma facing carbon materials as well as dust sampling in JT-60U and the results are studied and compared with those of JET. In D-D discharge machines like JT-60U, tritium produced by D-D reaction does not fully lose its initial energy of 1 MeV and is implanted into plasma facing wall more than 1μm in depth. Hence tritium retention profile is separated from carbon deposition profiles. On the other hand, in JT-60U, H+D retention profiles in the diverter region are well correlated with the carbon deposition profiles and the deposition dominated inner diverter tiles show high retention, while the erosion dominated outer diverter tiles show low retention. Nevertheless the retained amount in the redeposited layers is smaller than those observed in JET, which is attributed to temperature rise of the redeposited layers probably owing to their poor thermal contact to the substrate. Carbon deposition on the plasma shadowed … More area and remote area like pumping ducts is very small and only small amount of dust is collected. Low deposition in the remote area in JT-60U could be attributed to the precise alignment of diverter tiles both toroidally and poloidally. It is suggested that divertor geometry could have rather strong effects on carbon deposition or carbon transport.Pulsed-laser induced desorption of hydrogen from co-deposits on JT-60 open-divertor tile was also investigated. The fundamental (1064 nm) and fourth harmonic (266 nm) emission of a 20 ps-Nd: YAG laser were used, and dependences of hydrogen desorption on laser intensity IL and wavelength λ were studied. Hydrogen-desorption efficiency, defined as the ratio between the number of desorbed hydrogen by laser irradiation and that of hydrogen retained in the ablated volume, was largest in the region, where strong ionization of C+ occurred, and was larger for λ = 266 nm, in which a laser photon can cut C-H bond, compared with that for λ=1064 nm. For the ablative removal of hydrogen, a short-wavelength and high-power laser is desirable. Less