Ultrafast X-ray Lasers Illuminate Airborne Nanoparticle Morphology

ABSTRACTThe world’s first hard x-ray FEL (XFEL), the Linac Coherent Light Source (LCLS) is operational, steadily producing mJ energy, <75 fs pulses of 1.5 Å x-rays (1012 photons per pulse), a billion times more intensity than any other X-ray source. XFELs have stimulated the shift from the use of x-rays to probe periodic structures, such as crystals, to imaging non-periodic structures using ultrabright x-ray pulses shorter than the time for required for the onset of damage. The international community has embraced the potential as additional XFELs are currently being constructed in Japan, Italy and Germany with many more already planned or in construction elsewhere. Here the recent efforts to extend x-ray microscopy to the nanoscale for airborne particles using diffract-and-destroy methods are reviewed. Projecting current experimental results to future facilities suggests that gains of more than 104 in data acquisition rates are possible by 2020. This projection emphasizes the need for the development of fast x-ray detectors, infrastructure investments to handle the rapid data rate and storage requirements, as well as the appropriate training of scientists to handle data interpretation. Further improvements in particle delivery methods are also necessary, in particular to reduce sample consumption and to provide orthogonal data channels for each individual particle imaged. The projected growth of single particle CXDI data rates show great promise for the field. However, to achieve the resolution required to solve many scientific problems tractable with single-shot imaging, improvements in the absolute number of photons per pulse in a given area are still necessary.