Abstract

In this study, quantitative measurement of the spatial coherence of electron beams emitted from a thermionic-emission 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 $6.9\;\unicode{x00B5}{\rm m}$, 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 ${{\rm LaB}_6}$ 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.

© 2021 Optical Society of America

Spatial coherence of anisotropic and astigmatic sources in interference electron microscopy and holography

Francisco F. Medina and Giulio Pozzi
J. Opt. Soc. Am. A 7(6) 1027-1033 (1990)

Quality factor of partially coherent Airy beams in a turbulent atmosphere

Wei Wen, Xianwu Mi, and Shaohua Xiang
J. Opt. Soc. Am. A 38(11) 1612-1618 (2021)

Study of the origin of the complex beam profile of a hole-coupled free electron laser oscillator

Heishun Zen and Hideaki Ohgaki
J. Opt. Soc. Am. A 38(11) 1656-1661 (2021)

Measurements of spatial coherence of partially coherent light with and without orbital angular momentum

H. Di Lorenzo Pires, J. Woudenberg, and M. P. van Exter
J. Opt. Soc. Am. A 27(12) 2630-2637 (2010)

Spatial coherence of electron bunches extracted from an arbitrarily shaped cold atom electron source

Sebastian D. Saliba, Corey T. Putkunz, David V. Sheludko, Andrew J. McCulloch, Keith A. Nugent, and Robert E. Scholten
Opt. Express 20(4) 3967-3974 (2012)