We present feasibility study of an accelerator-based ultrafast transmission electron microscope (u-TEM) capable of producing a full field image in a single-shot with simultaneous picosecond temporal resolution and nanometer spatial resolution. We study key physics related to performance of u-TEMs, and discuss major challenges as well as possible solutions for practical realization of u-TEMs. The feasibility of u-TEMs is confirmed through simulations using realistic electron beam parameters. We anticipate that u-TEMs with a product of temporal and spatial resolution beyond 10 −19 m*s will open up new opportunities in probing matter at ultrafast temporal and ultrasmall spatial scales.

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We report an experimental demonstration of polarization smoothing by using a specially cut KDP plate in the convergent ultraviolet (351 nm wavelength) section of a high-power laser system. A 410  mm×410  mm×10  mm sized KDP plate placed after the final focus lens successfully reduced the focal spot intensity contrast to 75.6%, which is in good agreement with the theoretical expectation. In our experiment, no obvious transverse stimulated scattering was observed with the maximum 351 nm laser energy of 4032 J/3 ns, thus indicating the operation safety margin of our laser system.