First plasma operation in ITER will start after completing the assembly of the tokamak vessel and the installation of the main sub-systems, but prior to the installation of the blanket modules and the divertor cassettes. Utilization of temporary limiters and divertor replacement structures will provide a poloidal and toroidal reference side position to the plasma edge to protect the vacuum vessel and other components already installed during operations. An additional set of mirrors is required to reflect the power injected from the upper launcher towards the plasma resonance for EC-assisted breakdown of the plasma up to a beam dump needed to trap and absorb the power of the beams after crossing the plasma in order to reduce the stray radiation escaping back into the vacuum chamber down to less than 10% of the total power. The quasi-optical system has been designed, with shape and size of the mirrors compliant with the requirements provided by ITER for their installation, realization and plasma performances, resulting in two standard focussing mirrors and one grating mirror. The beam dump consists of a box with five metal plates, the first providing a spreading of the high incident power and the others coated with absorbing material with thickness distribution studied to gradually reduce the power during the multiple reflections inside the box, avoiding damages to the coating itself. This work focuses on the validation of the quasi-optical design of the mirrors and the assessment of the dump performances, based on a multi-bounces model developed ad-hoc for this purpose. The study includes a tolerance analysis for the beam dump to include the effect of uncertainties in the thickness of the absorbing coating and misalignments of the mirrors, to verify the performances of the dump also when operating in different conditions with respect to the nominal ones.

中文翻译：

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ITER 首次等离子体操作的容器内镜子和束流收集器的设计验证

ITER 中的第一次等离子体操作将在完成托卡马克容器的组装和主要子系统的安装之后开始，但在毯子模块和偏滤器盒的安装之前。利用临时限制器和偏滤器替换结构将为等离子体边缘提供极向和环形参考侧位置，以保护操作期间已安装的真空容器和其他部件。需要一组额外的镜子将从上部发射器注入的功率反射到等离子体共振，以实现等离子体的 EC 辅助分解，直至束流收集器，该束流收集器需要在穿过等离子体后捕获和吸收束流的功率，以便将逃逸回真空室的杂散辐射减少至总功率的 10% 以下。准光学系统的设计，反射镜的形状和尺寸符合ITER对其安装、实现和等离子体性能的要求，包括两个标准聚焦镜和一个光栅镜。光束收集器由一个带有五块金属板的盒子组成，第一块金属板提供高入射功率的传播，其他金属板涂有吸收材料，其厚度分布经过研究，可在盒子内部多次反射期间逐渐降低功率，避免损坏涂层本身。这项工作的重点是验证镜子的准光学设计和评估转储性能，基于为此目的专门开发的多次反射模型。该研究包括对光束收集器的公差分析，包括吸收涂层厚度的不确定性和反射镜未对准的影响，以验证光束收集器在相对于标称条件的不同条件下运行时的性能。