Magnetic Sample Environment for in situ SAXS WAXS Measurements on Magnetic Nanoparticles with Shape Anisotropy

A vacuum compatible magnetic sample environment has been developed and installed at the four crystal monochromator beamline of the Physikalisch Technische Bundesanstalt PTB at the synchrotron radiation facility BESSY II in Berlin, Germany. The design is based on a water cooled electromagnetic coil setup and is aimed to provide a magnetic flux density of up to 900 mT at the sample position. The magnetic field is applied in order to align or arrange magnetic nanoparticles which can then be measured using small angle X ray scattering SAXS and wide angle X ray scattering WAXS . This can be beneficial in the analysis of particles with arbitrary shape. The corresponding scattering patterns are collected as 2D images on vacuum compatible variants of the PILATUS 1M and PILATUS 100K detector

Improved measurement results for the Avogadro constant using a 28Si-enriched crystal

New results are reported from an ongoing international research effort to accurately determine the Avogadro constant by counting the atoms in an isotopically enriched silicon crystal. The surfaces of two 28Si-enriched spheres were decontaminated and reworked in order to produce an outer surface without metal contamination and improved sphericity. New measurements were then made on these two reconditioned spheres using improved methods and apparatuses. When combined with other recently refined parameter measurements, the Avogadro constant derived from these new results has a value of $N_A = 6.022 140 76(12) \times 10^{23}$ mol$^{-1}$. The X-ray crystal density method has thus achieved the target relative standard uncertainty of $2.0 \times 10^{-8}$ necessary for the realization of the definition of the new kilogram.Comment: postprint, 22 page, 3 figures, 14 table

A new 28Si single crystal: counting the atoms for the new kilogram definition

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Characterization of a quadrant diamond transmission X ray detector including a precise determination of the mean electron hole pair creation energy

Precise monitoring of the incoming photon flux is crucial for many experiments using synchrotron radiation. For photon energies above a few keV, thin semiconductor photodiodes can be operated in transmission for this purpose. Diamond is a particularly attractive material as a result of its low absorption. The responsivity of a state-of-the art diamond quadrant transmission detector has been determined, with relative uncertainties below 1% by direct calibration against an electrical substitution radiometer. From these data and the measured transmittance, the thickness of the involved layers as well as the mean electron–hole pair creation energy were determined, the latter with an unprecedented relative uncertainty of 1%. The linearity and X-ray scattering properties of the device are also described.</jats:p