Full spatial characterization of a nanofocused x-ray free-electron laser beam by ptychographic imaging

Abstract

The emergence of hard X-ray free electron lasers (XFELs) enables new insights into many fields of science. These new sources provide short, highly intense, and coherent X-ray pulses. In a variety of scientific applications these pulses need to be strongly focused. In this article, we demonstrate focusing of hard X-ray FEL pulses to 125 nm using refractive x-ray optics. For a quantitative analysis of most experiments, the wave field or at least the intensity distribution illuminating the sample is needed. We report on the full characterization of a nanofocused XFEL beam by ptychographic imaging, giving access to the complex wave field in the nanofocus. From these data, we obtain the full caustic of the beam, identify the aberrations of the optic, and determine the wave field for individual pulses. This information is for example crucial for high-resolution imaging, creating matter in extreme conditions, and nonlinear x-ray optics.

Coherent X-ray diffractive imaging on the single-cell-level of microbial samples

“…More recent ptychographic studies investigate the maximum derivable information from ptychographic data under non-simple experimental conditions for the illuminating wave-eld or the object such as position uncertainties [20,110,182], partial coherence and multiple wavelenghts [15,44,78,299], multiple object planes [181,284] and undersampling of the recorded di racted intensities [71]. In the rst place, however, the probably most important result has been the understanding that the ptychographic method not only is able to solve for the encoded object information but also for the illuminating wave-eld [183,294,296] making ptychography a valuable tool for analysing the wave-elds of X-rays [134,144,159,160,265,268]. In principle, the decoupling of object and illuminating wave-eld makes the retrieved object information free of aberrations.…”

The potential of future light sources to explore the structure and function of matter

“…All methods mentioned above, such as CDI, will benefit directly from this development. In particular, X-ray ptychography (Rodenburg et al, 2007;Schropp et al, 2012Schropp et al, , 2013) and X-ray ptychography feature articles tomography (Dierolf et al, 2010;Diaz et al, 2012;Trtik et al, 2013;Holler et al, 2014), which require scanning of the sample in steps of a fraction of the diameter of the coherent focus and a large number of projections, are extremely time consuming these days and would greatly benefit from the dramatically increased coherent flux, bringing down the time for such experiments from hours at present to minutes, or allowing for increased resolution, which is mainly limited by counting statistics at present. Such a development would bring us much closer to a routinely applicable X-ray three-dimensional microscope; it would never be able to compete with electron microscopy in terms of resolution but it would allow the study of thicker samples under relevant application conditions without special preparation at a resolution of the order of 5 nm or better.…”

High-flux ptychographic imaging using the new 55 µm-pixel detector `Lambda' based on the Medipix3 readout chip

“…partial coherence, broad bandpass illumination or a thick object (Maiden & Rodenburg, 2009;Thibault et al, 2009;Thibault & Menzel, 2013;Claus et al, 2013;Edo et al, 2013;Suzuki et al, 2014;Batey et al, 2014;Clark et al, 2014;Enders et al, 2014). Hence, ptychography is also an ideal tool for analysing X-ray wavefields (Schropp et al, 2010;Kewish, Guizar-Sicairos et al, 2010;Kewish, Thibault et al, 2010;Hö nig et al, 2011;Vila-Comamala et al, 2011;Wilke et al, 2012;Schropp et al, 2013;Huang et al, 2013). However, achieving optimum resolution in ptychographic imaging remains a challenge.…”

“…correcting for positional errors (GuizarSicairos & Fienup, 2008;Maiden et al, 2012;Beckers et al, 2013;Tripathi et al, 2014) but on the experimental side this problem is currently mainly approached by increasing the fluence (e.g. Takahashi et al, 2011Takahashi et al, , 2013Guizar-Sicairos et al, 2012;Holler et al, 2012;Schropp et al, 2012;Wilke et al, 2013).…”