Pre-characterization pipeline for microjets in X-ray free-electron laser experiments

Gas Dynamic Virtual Nozzles (GDVNs) are used in certain X-ray free-electron laser facility experiments, such as serial femtosecond crystallography, to deliver fresh, microscopic jets of sample for each X-ray pulse to interact with.

For the best measurements, researchers need to be able to precisely control the characteristics of these microjets, including speed, diameter, and stability. Combining specialized hardware and open-source software, Karpos et al. developed a microjet characterization pipeline that automatically collects and analyzes images of micrometer-scale liquid jets produced by GDVNs. This system makes it easier to characterize and optimize microjets before arriving at an X-ray free-electron laser facility, where beamtime is limited.

“We can greatly increase the odds of success in our experiments simply because of how easy it is to pre-characterize microjets,” said author Konstantinos Karpos. “This can save huge amounts of money, time and effort by reducing the likelihood of wasted time and resources. This increases the chances of successfully capturing high-quality data necessary for unraveling complex biological mechanisms.”

The authors used the system to measure water jets down to 200 nanometers in diameter, which is smaller than previously observed with optical light. Current methods to study jets with sub-micrometer diameters require an environmental scanning electron microscope (ESEM).

“We no longer need to use ESEM, which was tedious, expensive, and required a customized ESEM,” Karpos said.

This reliable microjet characterization method could be extended beyond current standard experimental applications to a broader range of techniques such as fluctuation x-ray scattering, mass spectrometry, and time-resolved cryo-electron microscopy.

The authors also hope to add capabilities to the system beyond microjet characterization, such as fluorescence imaging.

Source: “Comprehensive characterization of gas dynamic virtual nozzles for X-ray free-electron laser experiments,” by Konstantinos Karpos, Sahba Zaare, Dimitra Manatou, Roberto C. Alvarez, Vivek Krishnan, Clint Ottmar, Jodi Gilletti, Aian Pableo, Diandra Doppler, Adil Ansari, Reza Nazari, Alexandra Ros, and Richard A. Kirian, Structural Dynamics (2024). The article can be accessed at https://doi.org/10.1063/4.0000262 .

This paper is part of the A decade of biology with XFELs: The 10th Annual BioXFEL International Conference Collection, learn more here .