Fig. 1: Schematic of the ultrafast electron microscope used for imaging photoemitted electron gas dynamics. | Nature Communications

Fig. 1: Schematic of the ultrafast electron microscope used for imaging photoemitted electron gas dynamics.

From: Transient lensing from a photoemitted electron gas imaged by ultrafast electron microscopy

Fig. 1: Schematic of the ultrafast electron microscope used for imaging photoemitted electron gas dynamics.The alternative text for this image may have been generated using AI.

a Short probe electron pulses (~500 fs, 490 kHz, 300 keV) are generated by impinging a UV (256 nm) laser beam onto a LaB6 photocathode. Pump laser pulses (~200 fs, 528 nm, 490 kHz, ~30 mJ/cm2) are focused onto the Cu grid sample inside a modified TEM. b A hot electron gas (red), created by means of two-photon emission, acts as a diverging lens to the probe electrons. After initial Coulomb explosion, the electron gas executes cyclotron oscillations (gray orbits) inside the magnetic field (b) of the objective lens, which are resolved by changing the relative timing of the pump and probe pulses (Δt). The strength of the intermediate lens in the TEM can be tuned to obtain different imaging conditions. The sample is tilted by 15o towards the pump laser in order to minimize the laser footprint on the sample.

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