Tritium retention and erosion/deposition of first wall materials

研究了等离子体表面碳材料中氢同位素（H、D、1）的滞留、侵蚀/沉积以及JT-60U的粉尘取样，并与JET的结果进行了比较。在JT-60U等D-D放电机中，D-D反应产生的氚在未完全失去初始1 MeV能量的情况下，被注入1μm以上的等离子体面壁。因此，氚保留剖面从碳沉积剖面中分离出来。另一方面，JT-60U引流区H+D保留剖面与碳沉积剖面具有较好的相关性，以沉积为主的内导流瓦保留较高，而以侵蚀为主的外导流瓦保留较低。然而，再沉积层中的残留量比JET中观察到的要少，这可能是由于再沉积层与衬底的热接触不良导致温度升高。更多的区域和偏远的区域，如抽水管道是非常小的，只有少量的灰尘被收集。JT-60U偏远地区的低沉积可归因于导流瓦的环形和多向精确排列。说明导流器的几何形状对碳沉积或碳输运有较强的影响。研究了脉冲激光对JT-60开导流瓦共沉积氢的解吸作用。利用20 ps nd: YAG激光器的基频（1064 nm）和四次谐波（266 nm）发射，研究了氢的解吸与激光强度IL和波长λ的关系。在C+发生强电离的区域，解吸氢效率最大，且在λ= 266 nm处，激光光子可以切割C- h键，解吸氢效率比λ=1064 nm处更大。对于烧蚀除氢，需要短波长和高功率的激光器。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