Electron-to-counts conversion efficiency is an important parameter of electron detectors. The CCD has the
advantage of a better conversion efficiency, better spatial resolution, and often a higher dynamic range (16 bit).
High conversion efficiency is very important if the signal of interest is low.
For instance, conversion efficiency of Ultrscan provided by Gatan is between 24 and 57 Counts/Prim e-. In the Gatan 666 PEELS system, a single count in the
multichannel analyzer is the result of ∼ 30 primary electrons, which create 30,000
photons at the scintillator, resulting in 3000 photodiode electrons .
To avoid beam damage with high energy electron beams, one needs to reduce the data acquisition time by maximizing:
i) The electron-to-counts conversion efficiency in EELS and TEM/STEM measurements,
ii) The count rate capacity and collection efficiency in EDS measurements.
 J. Geiger, “Inelastic electron scattering with energy losses in the meV-region,”
39th Ann. Proc. Electron Microsc. Soc. Am., ed. G.W. Bailey, Claitor’s Publishing,
Baton Rouge, Louisiana, 182 (1981).