Lee Ha Rim, Hwang Junhyeok, Ogawa Takashi, Kim Jisoo, Lee Jeong-Woong, Jung Haewon, Yun Dal-Jae, Lee Sangsun, Park In-Yong
Scientific Instruments Performance Evaluation Team, Advanced Instrumentation Institute, Korea Research Institute of Standards and Science (KRISS), 267 Gajeong-ro, Yuseong-gu, Daejeon 34113, South Korea.
Major in Nanoconvergence Measurement, University of Science and Technology, 217 Gajeong-ro, Yuseong-gu, Daejeon 34113, South Korea.
Microsc Microanal. 2023 Dec 21;29(6):2004-2013. doi: 10.1093/micmic/ozad122.
To date, lanthanum hexaboride (LaB6) thermionic electron sources have not been able fully to capitalize on their inherent potential, resulting in an ambiguous position within the application area. Although they exhibit higher brightness compared with a tungsten filament source, they still fall short of the performance of Schottky electron sources. This study aims to explore the capabilities of the LaB6 electron source under different operating conditions to bridge the gap, ultimately to realize its untapped potential. Simulations in virtual source mode indicated enhanced beam brightness and a reduced beam half-angle with an increase the extraction voltage, promising up to tenfold times higher beam brightness compared with the crossover mode. The energy distribution measured using a prelens retarding field energy analyzer revealed an energy distribution of 0.55 eV and a high angular current density of 33 mA/sr in the virtual source mode. Therefore, the virtual source mode of LaB6 can provide a narrow energy distribution akin to that of a ZrO/W Schottky electron gun (1600 K) while having an angular current density over 2,000 times higher. In addition, the stability of the virtual source mode is ±0.022%, while that of the crossover mode is ±0.138%.
迄今为止，六硼化镧（LaB6）热离子电子源尚未能够充分发挥其固有潜力，导致其在应用领域的地位尚不明确。尽管与钨丝源相比，它们具有更高的亮度，但仍不及肖特基电子源的性能。本研究旨在探索LaB6电子源在不同工作条件下的能力，以弥合差距，最终实现其未开发的潜力。虚拟源模式下的模拟表明，随着提取电压的增加，束流亮度增强，束流半角减小，与交叉模式相比，束流亮度有望提高十倍。使用透镜前减速场能量分析仪测量的能量分布显示，在虚拟源模式下，能量分布为0.55 eV，角电流密度高达33 mA/sr。因此，LaB6的虚拟源模式可以提供类似于ZrO/W肖特基电子枪（1600 K）的窄能量分布，同时角电流密度高出2000倍以上。此外，虚拟源模式的稳定性为±0.022%，而交叉模式的稳定性为±0.138%。
