Precise measurement of the electron beam current in a TEM

Doses for X‐ray and electron diffraction: New features in RADDOSE‐3D including intensity decay models

“…Measuring the beam current as indicated by the built-in screen ampere meter can also often be inaccurate. Installing a Faraday cup, or using the drift tube of a spectrometer as a Faraday cup, is often the most accurate method (Krause et al, 2021), and can also be used to properly calibrate the screen ampere meter. We compared the symptoms of RD (specifically the rates of intensity decay, disulphide bond breakage, and decarboxylation) at cryo-temperatures in MicroED and X-ray crystallography, and determined that both global and specific damage events happen at similar doses.…”

“…Since account is now taken of primary beam energy and specimen composition, the biggest error in dose is likely to be the fluence measurement itself. Methods to measure this as accurately as possible are discussed by Krause et al ( 2021 ). Unless beam currents are very low, one must be careful when using the counts from a direct electron detector, because of coincidence loss (Li et al, 2013 ).…”

“…Measuring the beam current as indicated by the built‐in screen ampere meter can also often be inaccurate. Installing a Faraday cup, or using the drift tube of a spectrometer as a Faraday cup, is often the most accurate method (Krause et al, 2021 ), and can also be used to properly calibrate the screen ampere meter.…”

Event driven 4D STEM acquisition with a Timepix3 detector: microsecond dwell time and faster scans for high precision and low dose applications

“…If one electron lights up one pixel, this corresponds to a current of 6.4 pA which compared to conventional STEM imaging is somewhat on the low side. In the Section 3, it is shown that this estimate has to be adjusted with more technical details but the order of magnitude is correct [29]. In Fig.…”

“…Since the incoming electron current is lower than the detection threshold for measuring the current via the fluorescent screen or spectrum drift tube method, no absolute measurement of the electron current could be performed here. However in the work of Krause et al [29] it is shown that direct electron detectors provide an accurate estimate for low currents. Since the 7 keV threshold loses the least amount of electrons (see Fig.…”