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Description
Fast beam blanking provides a direct way to control electron dose and time structure in (S)TEM without altering the imaging optical conditions. The NanoPulser is an electrostatic beam blanker [Mv1.1]integrated between the C1 aperture and lens on the Iliad (S)TEM platform. It provides guaranteed sub-10 ns unblanking (3.5 ns demonstrated), repetition rates up to 1 MHz, and control through AutoScript. It is positioned in front of the condenser system[Mv2.1], the module can be used without optical limitations during normal operation.
A first application is dose reduction during STEM scanning. By blanking the beam during flyback and at the beam parking position, electrons are delivered to the specimen only when signal is being acquired[Mv3.1]. In experiments on a zeolite structure, flyback contributions of up to 30% of the electron dose and the dose accumulated at the beam parking position were removed, giving a clear improvement in image contrast and resolution.
The same timing control allows the beam to be used as a “gentle” pulsed probe. Automated workflows that vary dwell time and NanoPulser duty cycle show the expected increase in first-order FFT intensity with decreasing total dose. At constant total dose, reducing the duty cycle also increased the first-order reflection intensities, indicating reduced structural damage under stroboscopic illumination. Pulsed diffraction experiments on MoS₂, with on average one electron per pulse, further indicate that temporal separation of electrons can mitigate beam damage at comparable average dose rates.
For dynamic experiments, the NanoPulser enables sub-10 ns stroboscopic imaging. In a 5D-STEM experiment, the rise of an electric field across a gap between two electrodes in an electrochemical holder was mapped by measuring the time-dependent deflection of the direct beam [1]. The illumination was varied from steady state down to 3.5 ns electron pulses with approximately 2 ns timing steps, while maintaining repetition rates up to 1 MHz.
Beyond conventional raster scanning, fast blanking enables non-conventional and sparse scan strategies such as random, Hilbert, and bitmap patterns [2]. It also enables dose painting, in which the beam-open time is controlled for each individual pixel while maintaining a fixed pixel dwell [3]. This creates a practical route to distribute electron dose according to a user-defined spatial or multimodal criterion.
These results show that the NanoPulser is not only a fast blanker, but a beam-delivery module that links dose, dose rate, time structure, and automated microscope control. As a standard feature on new Iliad (S)TEM systems, it provides a platform for dose-efficient imaging, beam-damage mitigation, sub-10 ns stroboscopy, and programmable scan strategies.
Figure 1 Schematic overview of NanoPulser integration and application space. The Nanopulser is placed in front of the C1 lens and enables fast beam gating for flyback/park blanking, duty-cycle control, pulsed illumination, dose painting, and sub-10 ns stroboscopic experiments.
References
1. Microscopy and Microanalysis, 30 (Suppl. 1) (2024), 1465–1466, doi:10.1093/mam/ozae044.723
2. A. Velazco et al., Ultramicroscopy (2020), 113021, doi:10.1016/j.ultramic.2020.113021
3. P. Potoček et al., Advanced Intelligent Systems 6 (2024), 2300745, doi:10.1002/aisy.202300745
4. The authors acknowledge Ricardo Egoavil and Pavel Potoček for non-conventional scanning workflows and Joakim Kryger-Baggesen (DTU) and Noopur Jain (Thermo Fisher Scientific) for MoS₂ pulsed-diffraction experiments.