Zekun Fang

Topic

Cyclic Electron Illumination and Beam Response Measurement Using < 1 μs Multi-Trigger Exposures on the Merlin-Medipix Detector

Department of Physics and Astronomy

Date & location

• Wednesday, January 7, 2026
• 9:00 A.M.
• Clearihue Building, Room B007

Examining Committee

Supervisory Committee

• Dr. Arthur Blackburn, Department of Physics and Astronomy, University of Victoria (Supervisor)
• Dr. Andrew MacRae, Department of Physics and Astronomy, UVic (Member)
• Dr. Makhsud Saidaminov, Department of Chemistry, UVic (Outside Member)

External Examiner

• Dr. Rodney Herring, Department of Mechanical Engineering, UVic

Chair of Oral Examination

• Dr. Jordan Stanger-Ross, Department of History, UVic

Abstract

There is a need to observe dynamic microscopic phenomena and reduce sample damage in electron microscopy to enable better understanding of physical phenomena and allow higher-fidelity microstructure determination for materials science and biological applications. This need is driving advances in time resolved electron microscopy and creates the requirement to characterize the dynamic response of the electron beam at the upper frequency limits of the microscope’s scan deflection system.

Here we advance time resolved electron microscopy using the previously little-explored multiple-trigger frame mode of the Medipix-Merlin detector on a transmission electron microscope (TEM). We use this detector at trigger rates up 200 kHz with shutter or count-enable durations down to 100 ns, to determine the voltage to beam-deflection transfer function, including the frequency-dependent phase response. Following this, we describe and test a scheme for providing a 50 kHz pulsed illumination mode in a TEM, using a cyclic orbital beam trajectory synchronized with multi-trigger frame acquisition on a Medipix-Merlin detector. This allows us to obtain time or electron-dose resolved series of selected area diffraction data. We apply this scheme to investigate electron damage in C36H74 paraffin (hexatriacontane). This is a model highly electron-beam sensitive material that has previously been characterised using a pulsed-laser excited electron beam source in the TEM. However, owing to experimental uncertainties of our method on this very sensitive material, our damage rate results on this material are inconclusive.

Nonetheless our advancement and demonstration of a new pulsed electron beam illumination mode for TEM, and a new method of determining the amplitude and phase response of the beam deflection system, should be useful for those seeking to develop high-speed and lower-cost dynamic electron microscopy systems.