Ultrashort, low-emittance electron pulses can be created at a high repetition rate by using a TM$_{110}$ deflection cavity to sweep a continuous beam across an aperture. These pulses can be used for time-resolved electron microscopy with atomic spatial and temporal resolution at relatively large average currents. In order to demonstrate this, a cavity has been inserted in a transmission electron microscope, and picosecond pulses have been created. No significant increase of either emittance or energy spread has been measured for these pulses. At a peak current of $814pm2$ pA, the root-mean-square transverse normalized emittance of the electron pulses is $varepsilon_{n,x}=(2.7pm0.1)cdot 10^{-12}$ m rad in the direction parallel to the streak of the cavity, and $varepsilon_{n,y}=(2.5pm0.1)cdot 10^{-12}$ m rad in the perpendicular direction for pulses with a pulse length of 1.1-1.3 ps. Under the same conditions, the emittance of the continuous beam is $varepsilon_{n,x}=varepsilon_{n,y}=(2.5pm0.1)cdot 10^{-12}$ m rad. Furthermore, for both the pulsed and the continuous beam a full width at half maximum energy spread of $0.95pm0.05$ eV has been measured.
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