Hybrid pixel detector for data collection at 100 keV. (a) shows the EIGER X 500K camera mounted on the ISO160-K flange. (b) shows the vacuum enclosure containing the detector fitted to the bottom of the projection chamber of an FEI TF20. (c) shows the measured detective quantum efficiency (DQE) of the detector versus spatial frequency (fraction of the Nyquist frequency) at 100 keV. The inset shows the events that are observed with a threshold of 6.5 keV (with probability greater than 0.01%) in images that have less than one incident 100 keV electron per 1000 pixels. The relative probabilities for an electron to be recorded in one, two, three or four pixels are 0.257, 0.520, 0.140 and 0.081, respectively. This distribution for recording incident electrons gives an average response per electron of 2.0 counts and an upper bound for DQE(0) of 0.85.