One of the issues faced by future fusion devices will be high divertor target heat loads. Alternative divertors can promote detachment, flux expansion and dissipation mechanisms to mitigate these heat loads. They have been investigated in several devices including TCV and DIII-D, and will be investigated on MAST-U. To evaluate their effectiveness, accurate target heat flux and power balance measurements are required in these machines. Infrared (IR) thermography is a widely used technique to determine the target heat flux, but is susceptible to surface effects and emissivity in carbon-walled machines. In this work, the effect of plasma exposure on graphite is assessed to understand what may happen in MAST-U. A sample of fine grain graphite, as used on MAST-U, is exposed to 30min plasma exposures, with density $n_e=\text{6\hspace{0.17em}}\times \text{\hspace{0.17em}1018}\text{m−3}$ and temperature $T_e=\text{0.08}\text{eV}$ as measured by Thomson scattering. During these pulses, the temperature is measured by a medium wave IR camera and is seen to decrease by $\approx$70 °C over the course of 3h of plasma exposure. Pyrometer measurements suggest that the IR camera data is affected by a change in the surface emissivity. Profilometry confirms erosion of graphite at the tile centre to a depth of $\approx \text{100}\text{µm}$, and a larger region of deposition further out, amounting to $\approx \text{40}\text{µm}$ of material.

未来的聚变设备面临的问题之一将是偏滤器目标热负荷高。替代分流器可以促进分离，磁通膨胀和耗散机制，以减轻这些热负荷。已在包括TCV和DIII-D在内的多种设备中对它们进行了研究，并将在MAST-U上对其进行研究。为了评估其有效性，这些机器需要精确的目标热通量和功率平衡测量值。红外（IR）热成像技术是确定目标热通量的一种广泛使用的技术，但是易受碳壁机器中表面效应和发射率的影响。在这项工作中，评估了等离子体暴露对石墨的影响，以了解MAST-U中可能发生的情况。将用于MAST-U的细晶粒石墨样品暴露于30分钟的等离子暴露下，密度${ñ}_{Ë}=\text{6}\times \text{1018}\text{m−3}$ 和温度 ${Ť}_{Ë}=\text{0.08}\text{电子伏特}$通过汤姆森散射测量。在这些脉冲期间，温度由中波红外热像仪测量，并且观察到温度降低了$\approx$在等离子暴露3小时的过程中达到70°C。高温计的测量表明，红外热像仪数据受表面发射率变化的影响。轮廓测定法可确认瓷砖中心的石墨腐蚀深度为$\approx \text{100}\text{微米}$，并且更大的沉积区域更远，总计 $\approx \text{40}\text{微米}$ 材料。