HIGH-SPEED MULTIFRAME DYNAMIC TRANSMISSION ELECTRON MICROSCOPE IMAGE ACQUISITION SYSTEM WITH ARBITRARY TIMING

摘要

An electron microscope is disclosed which has a laser-driven photocathode and an arbitrary waveform generator (AWG) laser system (“laser”). The laser produces a train of temporally-shaped laser pulses of a predefined pulse duration and waveform, and directs the laser pulses to the laser-driven photocathode to produce a train of electron pulses. An image sensor is used along with a deflector subsystem. The deflector subsystem is arranged downstream of the target but upstream of the image sensor, and has two pairs of plates arranged perpendicular to one another. A control system controls the laser and a plurality of switching components synchronized with the laser, to independently control excitation of each one of the deflector plates. This allows each electron pulse to be directed to a different portion of the image sensor, as well as to be provided with an independently set duration and independently set inter-pulse spacings.

主权项

1. An electron microscope comprising:
a laser-driven photocathode; an arbitrary waveform generation (AWG) laser system for producing a train of temporally-shaped laser pulses of a predefined pulse duration and waveform, and arranged to direct the laser pulses to the laser-driven photocathode for producing a train of electron pulses; a first lens stack arranged to focus the train of electron pulses to a sample; a second lens stack producing a magnified image or diffraction pattern of the sample on an image sensor; a deflector subsystem having electrostatic deflector plates arranged downstream of the sample upstream of the image sensor, the deflector plates comprising a first pair of plates and a second pair of plates arranged perpendicular to the first pair of plates; and a control system in communication with both the AWG laser system and the deflector subsystem, the control system communicating with a plurality of switching components and synchronized with the AWG laser system for rapidly and reversibly switching voltage signals applied to each one of the deflector plates to independently control excitation of each one of the deflector plates to synch operation of the deflector subsystem with the train of laser pulses, so as to direct each said electron pulse to a different portion of the image sensor to capture a high-speed sequence of images or diffraction patterns of the sample, and to provide each said electron pulse with an independently set and programmable duration controlled by the controller, and to provide spacings between sequentially generated ones of the electron pulses that are variable, programmable and independently controlled by the controller.