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Published on: July 27, 2018
DC photoelectron gun parameters for ultrafast electron microscopy
Joel A Berger1, John T Hogan, Michael J Greco
1Department of Physics (M/C 273), University of Illinois at Chicago, 845 W. Taylor Street, Chicago, IL 60607-7059, USA.
This study characterizes an ultrashort laser pulse driven DC photoelectron gun. The results support the development of dynamic transmission electron microscopes with sub-nanometer, picosecond space-time resolution.
Area of Science:
- Physics
- Materials Science
- Electron Microscopy
Background:
- The development of advanced electron microscopes requires high-performance electron sources.
- Ultrashort laser pulses offer precise control over electron emission for advanced applications.
Purpose of the Study:
- To characterize the performance of a DC photoelectron gun driven by ultrashort laser pulses.
- To evaluate the feasibility of this gun for dynamic transmission electron microscopy (DTEM) with sub-1 nm.ps resolution.
Main Methods:
- Utilized a DC photoelectron gun based on the Togawa et al. thermionic emission gun design.
- Employed single-photon and two-photon photoemission from Ta and Cu(100) photocathodes.
- Drove photoemission using harmonics of a femtosecond Yb:KGW laser (261 nm and 532 nm pulses).
Main Results:
- Observed both single-photon (up to 20,000 electrons/pulse) and two-photon photoemission.
- Generated electron beams of approximately 1 mm² with negligible divergence at the anode.
- Photoemission efficiency showed dependence on laser polarization, consistent with theoretical expectations.
Conclusions:
- The characterized photoelectron gun demonstrates suitable performance for advanced electron microscopy.
- The results indicate potential for achieving sub-1 nm.ps space-time resolution in dynamic transmission electron microscopy.
- Further investigation into physical limitations is necessary for optimizing DTEM development.
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