Abstract

As part of the recovery project of the National Spherical Tokamak Experiment–Upgrade (NSTX-U), the divertor plasma-facing components (PFCs) were redesigned to handle significantly higher heat fluxes and longer pulse lengths than NSTX. The design process resulted in a castellated, graphite PFC tile. To verify the thermal performance of this design, dedicated electron beam, high heat flux (HHF) testing was carried out on a de-optimized mock-up PFC target. These tests demonstrated that the tile design is itself robust to large, localized thermal gradients. No mechanical damage to the mock-up was observed during HHF testing, though the actual PFC tile mechanical tie-down was not tested. Rather, when the surface temperature exceeded the sublimation temperature of graphite, carbon blooms from the mock-up tile surface were observed. This resulted in 1 to 2 mm of surface material ablating from the mock-up after repeated, highly localized electron beam exposures.

摘要

作为国家托卡马克实验升级（NSTX-U）回收项目的一部分，对偏滤器等离子体组件（PFC）进行了重新设计，以处理比NSTX高得多的热通量和更长的脉冲长度。设计过程产生了带齿的石墨PFC瓷砖。为了验证该设计的热性能，对未优化的模型化PFC目标进行了专用电子束，高热通量（HHF）测试。这些测试表明，瓷砖设计本身对较大的局部热梯度具有鲁棒性。在HHF测试期间，未观察到对模型的机械损坏，尽管未测试实际的PFC瓷砖机械约束。而是，当表面温度超过石墨的升华温度时，观察到从模型砖表面出现碳华。