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Cartoon scheme of the experiment.
Two different shots (laser on) of the beam on the detector after it has been streaked by the RF deflector. The jitter in the TOA appears in the different time of appearance of the scattered region, but does not affect the temporal resolution of the shadowgraph. In the inset, we show the unstreaked beam size on the same scale which is equivalent to 35 fs rms. On the right, we plot a lineout of the pixel intensities along the AB line to illustrate the sharp transition in the signal.
(a) and (b) Time-resolved shadowgraph for two different fluences. (c) Simulation results comparing point charge (left) and extended charge (right) distributions. (d) Comparing instantaneous (left) and thermal (right) charge emission models.
(a) Square of hole radius vs. incident laser fluence. The right axis shows the effective charge required in the model to reproduce the data. The red curve indicates the behavior expected for photoemission from Cu using 800 nm photons. The blue line indicates a power law fit to the data showing significant space charge induced saturation. (b) Hole radius vs. time. The data (green) are in good agreement with a thermal emission model (blue). The results from the instantaneous emission model (red) are also shown.
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