Fast pulse shaping for a novel gated electron mirror

Abstract

We present the design and prototype of a switchable electron mirror, along with a technique for driving it with an arbitrary pulse shape. We employ a general technique for electronic pulse-shaping, where high fidelity of the pulse shape is required, but the characteristics of the system, which are possibly nonlinear, are not known. This driving technique uses an arbitrary waveform generator to pre-compensate the pulse, with a simple iterative algorithm used to generate the input waveform. This is a broadly applicable, general method for arbitrary pulse shaping. Driving our switchable electron mirror with a flat-top pulse, we demonstrate an improvement in rms error of roughly two orders of magnitude compared to an uncompensated waveform. Our results demonstrate the feasibility of high fidelity waveform reproduction in the presence of nonidealities, with immediate applications in the realization of novel electron optical components.

Automated Design of Electron Mirrors for Multipass Electron Microscopy and 4D-STEM+EELS

“…Dose-efficient imaging techniques are critical for understanding the structure and properties of lowatomic-number materials. Two very different techniques-multipass electron microscopy [1] and fourdimensional scanning transmission electron microscopy [2] with simultaneous electron energy loss spectroscopy (4D-STEM+EELS)-that allow for increased information at constant electron dose stand to benefit or depend on a single, relatively new electron optical component: a gated mirror [3] that can selectively transmit or reflect electrons.…”

“…Multipass electron microscopy improves contrast by passing electrons through the sample multiple times in order to increase the phase and amplitude modulation of the transmitted electron produced by a specimen. Several designs have been proposed [4]- [7] and manufacturing is in progress for one microscope [5]; the use of a gated mirror to pass electrons in from the source or out to the detection apparatus is one of several approaches to handle switching between multipassing and electron emission/detection [3]. An important parameter for a gated mirror in multipass electron microscopy is the spherical aberration, as electrons reflected in the diffraction plane can acquire a negative third-order spherical aberration to cancel the positive spherical aberration of other elements in the column and lead to much lower aberrations added on each pass, allowing for a higher number of passes at high resolution without deterioration of image quality.…”