Most of our high-resolution imaging methods have to compromise between temporal or spatial resolutions, similar to a pinhole camera. If the entrance pinhole is very small, the resulting image is crisp, but requires a long exposure and thus, is less suitable to capture moving objects. One can increase the pinhole diameter and thus, increase the temporal resolution, but this comes at a cost of the sharpness of the image.
Of course, our microscopic tools have greatly evolved over time, but this original problem still limits our capabilities to observe fast processes at the nanoscale. Examples include chemical and catalytic reactions, nucleation dynamics and growth of nanoparticles, and other phenomena which are short-lived. One idea to overcome this obstacle is to use an illumination source, which is capable of producing intense short wavelengths radiation such as X-rays within very short exposure times.
X-ray Free Electron Lasers (FELs), such as the LCLS at SLAC, are capable of producing very bright bursts of coherent X-rays within a few femtoseconds. This large-scale technique offers unique opportunities to visualise fast processes via coherent X-ray diffractive imaging. Coherent X-ray diffractive imaging, however, suffers from intrinsic loss of phase, and therefore structure recovery is often complicated and not always uniquely-defined. Here, we introduce the method of in-flight holography, where we use nanoclusters as reference X-ray scatterers in order to encode relative phase information into diffraction patterns of a virus. The references (small spherical nanoparticles) and the bio samples are injected into random positions within the FEL focus. Using in-flight holography, we were able to reconstruct the unknown relative orientation of the reference and the sample. In a second step, we used Fourier X-ray holography to reconstruct the shape of the specimen.
In my talk I will report on several studies exploring the in-flight holography principle. Moreover, I will discuss future capabilities and applications for X-ray FELs and the possibility of future table-top experiments.
After her graduate studies at the Technical University of Berlin in Germany, Dr. Taisia Gorkhover joined SLAC in 2014 as a Peter Paul Ewald fellow from the Volkswagen Foundation. Gorkhover has been a spokesperson for three LCLS experiments and a collaborator in more than 15, and she co-authored or led more than 30 publications in high-impact journals. She has received the 2018 LCLS Young Investigator Award, granted to early-career scientists in recognition of exceptional research using the Linac Coherent Light Source (LCLS) X-ray free-electron laser at the Department of Energy’s SLAC National Accelerator Laboratory. Dr. Gorkhover was one of four SLAC scientists to win the Department of Energy’s Early Career Research Program award in March 2018. In 2016, she was the first female scientist to receive the Panofsky Fellowship, named after the laboratory’s founder and first director.
“I’m interested in developing new imaging methods that are becoming possible because of XFELs,” says Gorkhover. “My main motivation is to see how we can use this exciting technology to learn about the behavior of complex nanoscale systems.”
