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

Abstract

Suitable detection systems that are capable of recording high photon count rates with single-photon detection are instrumental for coherent X-ray imaging. The new single-photon-counting pixel detector 'Lambda' has been tested in a ptychographic imaging experiment on solar-cell nanowires using KirkpatrickBaez-focused 13.8 keV X-rays. Taking advantage of the high count rate of the Lambda and dynamic range expansion by the semi-transparent central stop, a high-dynamic-range diffraction signal covering more than seven orders of magnitude has been recorded, which corresponds to a photon flux density of about 10 5 photons nm À2 s À1 or a flux of $10 10 photons s À1 on the sample. By comparison with data taken without the semi-transparent central stop, an increase in resolution by a factor of 3-4 is determined: from about 125 nm to about 38 nm for the nanowire and from about 83 nm to about 21 nm for the illuminating wavefield.

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

“…This section is based on results that have been published in [333]. J. Wallentin's contributions of the nanowire sample and corresponding SEM images are gratefully acknowledged.…”

“…In the second section,`Bacterial Samples', the three leading sample systems Deinococcus radiodurans, Bacillus subtilis and Bacillus thuringiensis are reviewed and concepts of the used sample preparation techniques both for X-ray imaging and transmission electron microscopy are outlined. The third section,`Experiments', gives an overview about the experimental achievements that are partly based on publications in [330,332,333] (sections 3.1, 3.3, 3.4), have been accepted for publication [331] (section 3.2) or are in preparation for publication [329] 1 (section 3.5).…”

Phase retrieval for object and probe in the optical near-field

“…2.10(c)). Even worse, the flat field correction is only justified in case that the following approximation holds: 98) where D ∆i,j is the Fresnel propagation operator given in equation 2.45, o(x, y) is the transmission function of the sample given in equation 2.76 and p i (x, y) is the illumination at defocus distance i. For a more rigorous treatment of the validity of the flat field correction, the reader is referred to [30,31].…”

Advanced x-ray multilayer waveguide optics

“…With fully opened entrance slits in front of the KB mirrors, the beam size at GINIX was around 295 nm × 181 nm in x and y directions. Therefore, experiments were carried out with smaller slits, notably with a 50 µm slit size, to achieve a spot size broadened by diffraction, see also the ptychographic probe reconstructions presented in [81]. Moreover, this setting warrants full spatial coherence.…”