High quality ultrafast transmission electron microscopy using resonant microwave cavities

TL;DR

This paper demonstrates the creation of ultrashort, high-quality electron pulses in a transmission electron microscope using a resonant microwave cavity, achieving atomic resolution with minimal emittance increase.

Contribution

The study introduces a method to generate picosecond electron pulses with low emittance in a TEM using a TM110 cavity, maintaining beam quality at high repetition rates.

Findings

Picosecond electron pulses with minimal emittance increase.

Achieved high peak current of approximately 814 pA.

Maintained energy spread of about 0.95 eV for pulses and continuous beam.

Abstract

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 $814\pm2$ pA, the root-mean-square transverse normalized emittance of the electron pulses is $\varepsilon_{n,x}=(2.7\pm0.1)\cdot 10^{-12}$ m rad in the direction parallel to the streak of the cavity, and $\varepsilon_{n,y}=(2.5\pm0.1)\cdot 10^{-12}$ 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 $\varepsilon_{n,x}=\varepsilon_{n,y}=(2.5\pm0.1)\cdot 10^{-12}$ m rad. Furthermore, for both the pulsed and the continuous beam a full width at half maximum energy spread of $0.95\pm0.05$ eV has been measured.