CORRIGENDUM: Analytic description of the chemical erosion of graphite by hydrogen ions
CORRIGENDUM: Analytic description of the chemical erosion of graphite by hydrogen ions
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DOI：
10.1088/0029-5515/36/12/i05
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发表时间：
1996-12
期刊：
影响因子：
3.3
通讯作者：
J. Roth;C. García-Rosales
中科院分区：
文献类型：
--
作者：
J. Roth;C. García-Rosales
使用石墨作为面向等离子体的材料的一个主要问题是，由于碳氢化合物的形成，在氢轰击下会增加侵蚀。鉴于等离子体暴露碳组分的寿命评估以及ITER等现有和未来机器中产生的杂质，化学溅射侵蚀产额的相关能量、温度和入射通量的解析表达式具有特别重要的意义。到目前为止，基于对实验室数据的半经验拟合，还不可能外推与高密度偏滤器等离子体相关的通量和能量。从对现有经验公式的简要回顾开始，描述了最近对热活化碳氢化合物释放的原子过程的详细研究，这些研究使得建立包括离子通量作为参数的改进的分析描述成为可能。氢轰击对石墨的化学侵蚀有两个过程：一个是热激活的碳氢化合物释放，Ytherm；另一个是低能量和低温下的表面过程，是碰撞能量转移引起的表面碳氢化合物的动力学喷射，Ysurf。新的解析描述可以很好地符合现有的离子束侵蚀数据，并可以外推到偏滤器相关的通量。在高离子通量下，化学侵蚀的最大值被移到更高的温度，在那里，损伤结构的退火导致比先前估计的更强的Ytherm还原。没有关于Ysurf可能与通量相关的数据，这给外推留下了一些不确定性
One main concern about the use of graphite as a plasma facing material is the enhanced erosion under hydrogen bombardment due to hydrocarbon formation. In view of the lifetime evaluation of plasma exposed carbon components and of impurity production in present and future machines such as ITER, an analytical expression for the erosion yield by chemical sputtering for the relevant energies, temperatures and incident fluxes is of special importance. An extrapolation to fluxes and energies relevant for high density divertor plasmas has not been possible up to now on the basis of semiempirical fits to laboratory data. Starting from a short review of the existing empirical formulas, recent detailed investigations of the atomistic processes for the thermally activated hydrocarbon emission are described, which enable the formulation of an improved analytical description including the ion flux as a parameter. The chemical erosion of graphite by hydrogen bombardment results from two processes: the thermally activated hydrocarbon emission, Ytherm, and a surface process at low energies and low temperatures resulting from the kinetic ejection of surface hydrocarbon complexes from collisional energy transfer, Ysurf. The new analytic description can be fitted well to the existing data for ion beam erosion, and extrapolation to divertor relevant fluxes is possible. At high ion fluxes the maximum of chemical erosion is shifted to higher temperatures, where annealing of damaged structures leads to a stronger reduction of Ytherm than previously estimated. There are no data on a possible flux dependence of Ysurf, leaving still some uncertainty in extrapolation