  Multi-pass transmission electron microscopy (MPTEM) has been proposed as a
way to reduce damage to radiation-sensitive materials. For the field of
cryo-electron microscopy (cryo-EM), this would significantly reduce the number
of projections needed to create a 3D model and would allow the imaging of
lower-contrast, more heterogeneous samples. We have designed a 10 keV
proof-of-concept MPTEM. The column features fast-switching gated electron
mirrors which cause each electron to interrogate the sample multiple times. A
linear approximation for the multi-pass contrast transfer function (CTF) is
developed to explain how the resolution depends on the number of passes through
the sample.
