## beam diameter

in in situ microanalysis
https://doi.org/10.1351/goldbook.B00622
Diameter of the beam between which 68% of the electrons fall. For Gaussian beam shapes this corresponds to the 2$$\sigma$$-value of the intensity distribution of the beam. Measurement can be carried out by scanning a beam across a sufficiently sharp edge and recording the transmitted electrons.
Source:
PAC, 1983, 55, 2023. (Nomenclature, symbols and units recommended for in situ microanalysis (Provisional)) on page 2027 [Terms] [Paper]