Fig. 5: Dependence on the intermediate lens strength.
From: Transient lensing from a photoemitted electron gas imaged by ultrafast electron microscopy
a–c Image conditions with various intermediate lens currents (ILC): a 0.65 A, underfocus regime, barrel distortion, b 0.95 A, in-focus regime, c 1.1 A, overfocus regime, pincushion distortion. The corresponding images are shown at the bottom (Δt = 173 ps, OL current 0.7 A). Since the electron gas (EG, red) acts like a diverging lens, the probe electrons that pass through the gas (blue) are focused by the objective lens (OL) after/below the probe electrons that are not affected by the electron lens (green). COP = crossover plane. The scale bars are 50 μm (no scale bar for image in b, since the grid is not visible). In this figure, all the projection lenses after the sample are replaced by one equivalent lens (labeled IL). Only the IL strength was changed. The copper grid is not shown for simplicity. d ROI difference intensity traces for various ILC values (OL current 0.7 A).
