No abstract

This study explores the capabilities of the Coherent X-ray Imaging Instrument at the Linac Coherent Light Source to image small biological samples. The weak signal from small samples puts a significant demand on the experiment. Aerosolized Omono River virus particles of $40 nm in diameter were injected into the submicrometre X-ray focus at a reduced pressure. Diffraction patterns were recorded on two area detectors. The statistical nature of the measurements from many individual particles provided information about the intensity profile of the X-ray beam, phase variations in the wavefront and the size distribution of the injected particles. The results point to a wider than expected size distribution (from $35 to $300 nm in diameter). This is likely to be owing to nonvolatile contaminants from larger droplets during aerosolization and droplet evaporation. The results suggest that the concentration of nonvolatile contaminants and the ratio between the volumes of the initial droplet and the sample particles is critical in such studies. The maximum beam intensity in the focus was found to be 1.9 Â 10 12 photons per mm 2 per pulse. The full-width of the focus at halfmaximum was estimated to be 500 nm (assuming 20% beamline transmission), and this width is larger than expected. Under these conditions, the diffraction signal from a sample-sized particle remained above the average background to a resolution of 4.25 nm. The results suggest that reducing the size of the initial droplets during aerosolization is necessary to bring small particles into the scope of detailed structural studies with X-ray lasers.

No abstract

Energetic ions at moderate laser intensities using foam-based multi-layered targets. Plasma Physics and Controlled Fusion, 56(4): 045001http://dx

A three-dimensional reconstruction of the Melbournevirus affected by a strong artifact in the center of the particle is presented. Using simulations, the artifact was found to be probably caused by background scattering, while particle size and pulse-energy variation did not affect the quality of the reconstruction. Possible ways to minimize such problems in the future are suggested.