Quantitative measurement of spatial coherence of electron beams emitted from a thermionic electron gun
Quantitative measurement of spatial coherence of electron beams emitted from a thermionic electron gun
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DOI：
10.1364/josaa.437843
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发表时间：
2021-12-01
影响因子：
1.9
通讯作者：
Yamasaki, Jun
中科院分区：
文献类型：
--
作者：
Hatanaka, Shuhei;Yamasaki, Jun
据我们所知，在这项研究中，首次实现了热离子发射枪发射的电子束空间相干性的定量测量。为了进行测量，在 200 kV 透射电子显微镜中，使用有效直径约为 10 nm 的特制孔径在样品平面上形成艾里图案。随后，通过对光束直径范围为2.0至6.9μm记录的艾里图案进行拟合分析，成功测量了与光束直径成比例的7至19nm的空间相干长度。此外，考虑到在样品平面上测量的总束流的时间演化，显示了轴上电流密度和相干长度之间的关系，其中前者与后者的平方成反比。与先前研究中使用肖特基型场发射枪测量的结果相比，当在样品平面上形成相似的光束强度时，LaB6热离子发射枪透射电子显微镜的空间相干长度要短一到两个数量级。 (c) 2021 年美国光学学会
In this study, quantitative measurement of the spatial coherence of electron beams emitted from a thermionicemission gun was achieved for the first time, to our knowledge. For the measurement, Airy patterns were formed using a specially fabricated aperture with an effective diameter of approximately 10 nm at the specimen plane in a 200 kV transmission electron microscope. Subsequently, from the fitting analysis of the Airy patterns recorded with beam diameters ranging from 2.0 to 6.9 mu m, spatial coherence lengths from 7 to 19 nm were successfully measured in proportion to the beam diameters. In addition, considering time evolution of the total beam current measured at the specimen plane, the relation between the on-axis current density and the coherence length is shown, where the former is inversely proportional to the square of the latter. Compared with the result using a Schottky-type field emission gun measured in a previous study, the spatial coherence length in the LaB6 thermionic-emission gun transmission electron microscope is one to two orders of magnitude shorter when a similar beam intensity is formed at the specimen plane. (c) 2021 Optical Society of America