‘Pulse’ wins 2023 Innovation Award from Microscopy Today

Below is the nomination text that will be published in Microscopy Today:

The ‘Pulse’ signal digitizer enables single-electron-sensitivity event detection in the scanning transmission electron microscope (STEM). It takes the raw analog signal from conventional STEM detectors as an input and returns a digital event stream. This digital event stream becomes the input to the microscope, yielding a virtual digital detector. The ‘Pulse’ digitizer comprises custom signal processing electronics, a field-programmable gate array processor, and control communications. It uses standard BNC connectors and TTL digital signal lines for universal compatibility with all TEM manufacturers. It is fully enclosed in an all-metal case and powered by a low-voltage USB-C power supply for worldwide operability. The ‘Pulse’ digitiser can deliver increased speed and sensitivity by detection of the fast rising edges of individual scintillator events. As published in Microscopy & Microanalysis (DOI:10.1017/S1431927620024721), the gradient of the signal reveals the discrete fast rising edges, and these can be used to more sensitively detect electron events.

With the increasing interest in low-dose imaging, more and more operators are imaging with lower beam currents and shorter pixel dwell times. Under these conditions dark-field STEM begins to show individual impact events. However, at such low doses Gaussian noise becomes unacceptable, and the signal is not defined in meaningful units (e.g., vacuum regions are not zero). Moreover, as pixel times decrease below 500 nanoseconds, the present 1 microsecond decay behavior of conventional detectors becomes unacceptable. The ‘Pulse’ signal digitizer offers a simple modular approach to equip new microscopes (or retrofit existing ones) with a digital detection capability.

There are many materials and processes that are too beam sensitive to be imaged in the TEM, including energy storage materials, catalysts, biological tissue, and viruses. Many samples can be completely destroyed by the beam, or even worse, survive but give unreliable or misleading data. The ‘Pulse’ signal digitizer enables faster frame-rates without deleterious streaking, leading to more gentle imaging of fragile specimens. The all-digital readout of electron events leads to zero dark-noise, further improving the signal-to-noise ratio (SNR). More broadly, since the ‘Pulse’ signal digitizer can be retrofitted to existing columns, owners of older instruments have a cost-effective route to upgrade their imaging detectors.