Abstract:The experimental characterization of the spatial and temporal coherence properties of the free-electron laser in Hamburg (FLASH) at a wavelength of 8.0 nm is presented. Double pinhole diffraction patterns of single femtosecond pulses focused to a size of about 10×10 µm 2 were measured. A transverse coherence length of 6.2 ± 0.9 µm in the horizontal and 8.7 ± 1.0 µm in the vertical direction was determined from the most coherent pulses. Using a split and delay unit the coherence time of the pulses produced in the same operation conditions of FLASH was measured to be 1.75 ± 0.01 fs. From our experiment we estimated the degeneracy parameter of the FLASH beam to be on the order of 10 10 to 10 11 , which exceeds the values of this parameter at any other source in the same energy range by many orders of magnitude. (4) were well satisfied in our experimental geometry. The maximum time delay introduced through the path length difference was τ max ≈ 0.6 fs and was smaller than the temporal coherence length τ c = (1.75 ± 0.0.01) fs measured by the split and delay unit (see below). Therefore, we could safely assume that in transverse coherence measurements |γ eff 12 (τ)| ≈ |γ eff 12 (0)| and α 12 (τ) ≈ α 12 (0). 36. An unconstrained fit yields a value of |γ eff 11 | ≈ 0.8 in both directions and provides slightly larger values for the transverse coherence length. We attribute this to inhomogenities in the transmission through the pinholes. 37. J. Chalupsky, J. Krzywinski, L. Juha, V. Hajkova, J. Cihelka, T. Burian, L. Vyain, J. Gaudin, A. Gleeson, M.Jurek, A. R. Khorsand, D. Klinger, H. Wabnitz, R. Sobierajski, M. Störmer, K. Tiedtke, and S. Toleikis, "Spot size characterization of focused non-Gaussian X-ray laser beams", Opt. Express 18, 27836 (2010). 38. We attribute this positional uncertainty to both, instabilities of the sample stages and beam positional jitter. 39. In our experiment the maximum of |γ 12 (τ)| did not reach unity but rather a value of 0.14. The reason for this is that the full beam was split in the middle and overlapped again meaning that parts of the center of the beam were overlapped with parts of the edge of the beam (see [27]

The unique strengths of x-ray microscopy are high penetration depth and near-edge resonances that provide chemical information. We use ptychography, a coherent diffractive imaging technique that disposes of the requirement for isolated specimens, and demonstrate resonant imaging by exploiting resonances near the oxygen K edge to differentiate between two oxygen-containing materials. To highlight a biological system where resonant ptychography might be used for chemical mapping of unsliced cells, reconstructions of freeze-dried Deinococcus radiodurans cells at an energy of 517 eV are shown.

No abstract

A new Rococo 2 X-ray fluorescence detector was implemented into the cryogenic sample environment at the Hard X-ray Micro/Nano-Probe beamline P06 at PETRA III, DESY, Hamburg, Germany. It features a high solid angle of up to 1.10 steradian and high count rates of 1 Mcounts s−1 per sensor.

A ptychographical coherent diffractive imaging experiment in the water window with focused soft X-rays at 500 eV is reported. An X-ray beam with high degree of coherence was selected for ptychography at the P04 beamline of PETRA III synchrotron radiation source. The beam coherence was measured with the newly developed non-redundant array method, and a coherence length of 4.1 mm and global degree of coherence of 35% at 100 mm exit slit opening in the vertical direction were determined. A pinhole, 2.6 mm in size, selected the coherent part of the beam that was used to obtain ptychographic reconstruction results of a lithographically manufactured test sample and a fossil diatom. The achieved resolution was 53 nm for the test sample and was only limited by the size of the detector. The diatom was imaged at a resolution better than 90 nm.

Coherent X-ray ptychography is a tool for highly dose efficient lensless nano-imaging of biological samples. We have used partially coherent soft X-ray synchrotron radiation to obtain a quantitative image of a laterally extended, dried, and unstained fibroblast cell by ptychography. We used data with and without a beam stop that allowed us to measure coherent diffraction with a high-dynamic range of 1.7·10. As a quantitative result, we obtained the refractive index values for two regions of the cell with respect to a reference area. Due to the photon energy in the water window we obtained an extremely high contrast of 53% at 71 nm half-period resolution. The dose applied in our experiment was 9.5·10 Gy and is well below the radiation damage threshold. The concept for dynamic range improvement for low dynamic range detectors with a beam stop opens the path for high resolution nano-imaging of a variety of samples including cryo-preserved, hydrated and unstained biological cells.

Barnacles are able to establish stable surface contacts and adhere underwater. While the composition of adult barnacle cement has been intensively studied, far less is known about the composition of the cement of the settlement-stage cypris larva. The main challenge in studying the adhesives used by these larvae is the small quantity of material available for analysis, being on the order of nanograms. In this work, we applied, for the first time, synchrotron radiation-based μ-X-ray fluorescence analysis (SR-μ-XRF) for in vivo and in situ analysis of young barnacles and barnacle cyprids. To obtain biologically relevant information relating to the body tissues, adhesives, and shell of the organisms, an in situ sample environment was developed to allow direct microprobe investigation of hydrated specimens without pretreatment of the samples. In 8-day-old juvenile barnacles (Balanus improvisus), the junctions between the six plates forming the shell wall showed elevated concentrations of calcium, potassium, bromine, strontium, and manganese. Confocal measurements allowed elemental characterization of the adhesive interface of recently attached cyprids (Balanus amphitrite), and substantiated the accumulation of bromine both at the point of initial attachment as well as within the cyprid carapace. In situ measurements of the cyprid cement established the presence of bromine, chlorine, iodine, sulfur, copper, iron, zinc, selenium, and nickel for both species. The previously unrecognized presence of bromine, iron, and selenium in the cyprid permanent adhesive will hopefully inspire further biochemical investigations of the function of these substances.

Insects represent the majority of known animal species and exploit a variety of fascinating nanotechnological concepts. We investigated the wings of the damselfly Calopteryx haemorrhoidalis, whose males have dark pigmented wings and females have slightly pigmented wings. We used scanning electron microscopy (SEM) and nanoscale synchrotron X-ray fluorescence (XRF) microscopy analysis for characterizing the nanostructure and the elemental distribution of the wings, respectively. The spatially resolved distribution of the organic constituents was examined by synchrotron Fourier transform infrared (s-FTIR) microspectroscopy and subsequently analyzed using hierarchical cluster analysis. The chemical distribution across the wing was rather uniform with no evidence of melanin in female wings, but with a high content of melanin in male wings. Our data revealed a fiber-like structure of the hairs and confirmed the presence of voids close to its base connecting the hairs to the damselfly wings. Within these voids, all detected elements were found to be locally depleted. Structure and elemental contents varied between wing membranes, hairs and veins. The elemental distribution across the membrane was rather uniform, with higher Ca, Cu and Zn levels in the male damselfly wing membranes.