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Detailed schematic of the experimental setup including streak camera. Photoelectrons are produced by back-illumination of a gold cathode (z = 0 cm). They are then accelerated at 95 keV towards a 700 aperture in a disk silicon anode wafer (z = 1 cm). A magnetic lens (M1, z = 9 cm) collimates the bunch before entering the RF rebunching cavity (z = 39 cm), and a second magnetic lens (M2, z = 45 cm). The electrons then come to a temporal focus at the sample (z = 59 cm) and diffract from it. The electrons then pass through a pair of high voltage streak plates, placed 1 mm from the sample, encoding their time of arrival information with respect to a trigger laser pulse. They are then recorded at the CCD detector (z = 85 cm).
Characterization of the streak camera. The streak velocity is determined by changing the trigger delay and measuring the electron displacement on the CCD, yielding a value of 47 pixels/ps (2.8 mrads/ps) with error (±0.3 pixel per/ps). Inset: The streak velocity and arrival time is also affected by trigger pulse energy. The energy is given for 800 nm pulses with beam diameter of 3 mm FWHM. We worked in a saturated regime at 80 where a change in trigger pulse energy makes a minute contribution to the arrival time (11 ).
Characterization of the RF compressed electron pulses using the streak camera. (a) Plot shows single shot electron arrival times measured by the streak camera. Using the experimentally determined streak velocity in Fig. 2 , the jitter (blue trace) is 200 fs RMS. The reference direction (red trace), experiencing no streak voltage, yields a minimal temporal resolution to the determination of the arrival time of 30 fs RMS. (b) The panels show the minimal pulse duration achievable for the given electron densities at the sample position. Each pair of beams represents an unstreaked (left) and streaked (right) pulse on the CCD for a given measured electron density at the sample position. Pulse durations are given in FWHM. The scaling for each image pair is different.
Comparison of the streaked and unstreaked diffraction patterns. (a) Panel shows an averaged diffraction pattern of a Si(001) oriented thin crystal and panel (b) shows the same sample but with the streak camera turned on.
Proof of principle experiment with time stamping. (a) The (001) oriented silicon sample is pumped with 400 nm light. The photoinduced relative change to the (220) bragg peak is plotted as a function of time. Five traces were taken at 3 h time intervals, showing the effects of phase drift masking the dynamics. (b) The same data but with each shot re-binned using the time stamp generated from the displacement of the streaked diffraction patterns. The insets show the average of the 5 traces in (a) and (b), respectively.
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