Khan S F, Nyholm P R, Decker K J, MacPhee A G, Hilsabeck T J, Boyle D, Palmer N, Miller T A, Carpenter A C
Lawrence Livermore National Laboratory, Livermore, California 94550, USA.
General Atomics, San Diego, California 92186, USA.
Rev Sci Instrum. 2024 Oct 1;95(10). doi: 10.1063/5.0219554.
The National Ignition Facility produced the first nuclear fusion experiment demonstrating net positive energy gain on December 5, 2022. The x-ray streak camera that measures the bang time and burn-width from this landmark experiment had an electronic failure and did not record data. The CCD sensor was replaced with a radiation hardened CMOS sensor that has since demonstrated successful operation on repeat ignition shots. Concurrently, an instrument artifact was identified that occurs when the signal consists primarily of energetic x rays >15 keV (common on burning plasma experiments). This artifact, which appears as a background pedestal, arises from the x-ray back-fluorescence generated by the solid metal accelerating mesh behind the photocathode in the streak tube. We have mitigated this background signal by limiting the sensitive area of the photocathode. Herein, the details of the modifications and the results are presented.
国家点火装置于2022年12月5日进行了首次核聚变实验，展示了净正能量增益。用于测量这一具有里程碑意义实验的爆炸时间和燃烧宽度的X射线条纹相机出现电子故障，未记录数据。CCD传感器被一个抗辐射的CMOS传感器取代，该传感器此后在重复点火实验中已成功运行。同时，还发现了一种仪器伪像，当信号主要由能量大于15 keV的高能X射线组成时（在燃烧等离子体实验中很常见）就会出现。这种伪像表现为背景基座，是由条纹管中光阴极后面的固体金属加速网产生的X射线背向荧光引起的。我们通过限制光阴极的敏感区域来减轻这种背景信号。在此介绍修改的细节和结果。
