Porosity evolution in proton irradiated microfine-grained POCO graphite
Porosity evolution in proton irradiated microfine-grained POCO graphite
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DOI：
10.1016/j.jnucmat.2023.154732
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发表时间：
2023-09
影响因子：
3.1
通讯作者：
Ming Jiang;K. Ammigan;George Lolov;Frederique Pellemoine;Dong Liu
中科院分区：
文献类型：
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作者：
Ming Jiang;K. Ammigan;George Lolov;Frederique Pellemoine;Dong Liu
本文研究了在费米实验室NuMI束线上用340 kW、120 GeV质子辐照NT 02靶系统后POCO ZXF-5 Q石墨的孔隙度演化。这种POCO石墨在低剂量辐照下发生了直接的体积尺寸膨胀，在此过程中其局部微观结构的变化仍然没有得到很好的理解。在这项工作中，（亚）微米尺度的孔隙度从六个位置跨质子束注量和温度梯度进行了研究，使用聚焦离子束扫描电子显微镜（FIB-SEM）断层扫描。已经建立并实施了基于深度学习的断层图像分割技术，用于孔隙度分割和量化。已经发现，在质子束中心处的孔隙率的总体积百分比降低（0.88 - 8.4体积%），通过与未辐照的POCO（12 - 13体积%）进行比较梁2σ和5σ半径（体积分数为12%）。孔隙率体积百分比的降低是由于质子束中心区域材料体积膨胀导致体积> 0.1 μ m3的孔隙减少所致。讨论了孔隙率降低与尺寸变化和辐照蠕变的关系，以及其他影响因素，还需要通过控制良好的辐照实验进行进一步研究。
This work investigated the porosity evolution of POCO ZXF-5Q graphite that has been irradiated by 340 kW, 120 GeV protons inside NT02 target system in Fermilab's NuMI beamline. This POCO graphite has undergone direct bulk dimensional swelling at low dose irradiation and its local microstructural change is still not well-understood during this process. In this work, the (sub-) micrometre scale porosity from six locations across proton beam fluence and temperature gradients have been studied using focused ion beam-scanning electron microscopy (FIB-SEM) tomography. A deep learning-based tomographic image segmentation technique has been established and implemented for porosity segmentation and quantification. It has been found that there is a decrease in the total volumetric percentage of the porosity at proton beam centre (∼ 8 – 8.4 vol.%), by comparing to un-irradiated POCO (∼ 12 – 13 vol.%) and to beam 2σ and 5σ radii (∼ 12 vol.%). This decrease in porosity volume percentage was found to be caused by the reduction in pores with volumes > 0.1 μm3induced by material bulk dimensional swelling at proton beam centre area. The porosity reduction in relation to dimensional change and irradiation creep was discussed among with other contributing factors, and further investigations through well-controlled irradiation experiment are still needed.