Tunable Electron Beam Pulser for Picoseconds Stroboscopic Microscopy in Transmission Electron Microscopes
June W. Lau, Michael B. Katz
For two decades, time-resolved transmission electron microscopes (TEM) have relied on pulsed-laser photoemission to generate electron bunches to explore sub-microsecond to sub- picosecond dynamics. Despite the vast successes of photoemission time-resolved TEMs, laser- based systems are inherently complex, thus tend not to be turn-key. In this paper, we report on the successful retro t of a commercial 200KeV TEM, without an external laser, capable of producing continuously tunable pulsed electron beams with repetition rates from 0.1GHz up to 12GHz and a tunable bunch length from the repetition frequency down to 10 pico-seconds. This innovation enables temporal access into previously inaccessible regimes: i.e., high rep- etition rate stroboscopic experiments. Combination of a pair of RF-driven traveling wave stripline elements, quadruple magnets, and a variable beam aperture enables operation of the instrument in (1) continuous waveform (CW) mode as though the instrument was never unmodi ed, (2) stroboscopic (pump-probe) mode, and (3) pulsed beam mode for dose rate sensitive materials. To assess the e ect of a pulsed beam on image quality, we examined Au nanoparticles using brightfi eld, high-resolution TEM imaging and selected area diffraction in both continuous and pulsed-beam mode.