News


Invited talk at Helmholtz-Zentrum Berlin

Invited talk at Helmholtz-Zentrum Berlin

January 2016 - Rudi was invited to give a talk on Stoichiometry vs. morphology of photovoltaic films: Scattering experiments with chemical sensitivity in the Energy Materials In-situ Laborarory's (EMIL) seminar at the Helmholtz-Zentrum für Materialien und Energie (HZB) in Berlin. He also had a chance to see the HZB anomalous scattering beamline at Bessy after its relocation to the sector of the ring managed by the German metrology agency, Physikalisch-Technische Bundesanstalt (PTB) and admire its most recent addition, an in-vacuum Pilatus detector enabling ASAXS experiments at very low energies such as the sulphur K-edge. The trip was rounded off by comparing notes on current projects with Simone Raoux and Armin Hoell of HZB and Michael Krumrey of PTB. [more]  [other news]

Recent beamtime


SANS experiment on solvent-annealed diblocks on SANS2d

SANS experiment on solvent-annealed diblocks on SANS2d

The original aim of this experiment was to use proton/deuteron contrast to locate remnants of the solvents used in solvent-vapour annealing in our polymer films. As it turns out, the contrast arising from these small amounts of trapped solvent is insufficient to be detected on a sensible time scale. We therefore switched tack somewhat and varied the solvent from more polar (acetone) to non-polar (hexane) and the substrate temperature during annealing from 21C down to 1C. An initial look at the data suggests that they are in line with our findings using GISAXS during the recent commissioning experiment at I22. [more] [beamtimes]

Teaching materials


ph327 - Atomic Physics

ph327 - Atomic Physics

In this lecture, we're looking at the internal structure of the electron cloud of an atom, investigate how we can interact with it by triggering transitions between the different electronic states using spectroscopic methods, and derive the shape of the periodic table from the states available in atoms of the different chemical elements. Interactions between electronic states and forces internal and external to the atom are also considered, and mathematical methods which enable us to predict transitions and explain spectra. [more] [teaching]

Research papers


Dynamic strain propagation in nanoparticulate zirconia refractory

Dynamic strain propagation in nanoparticulate zirconia refractory

Residual and intrinsic strains in granular materials have been studied extensively. However, understanding the dynamic strains that cause these resultant residual strains is key to developing better strain-resistant materials. This investigation demonstrates a method for characterizing dynamic strain propagation in granular materials. The specimen is a zirconia based refractory composed of sol-gel-derived zirconia nanoparticles in a potassium silicate glass binder. In situ synchrotron X-ray powder diffraction in flat-plate geometry is used to characterize the sample structure on timescales of the order of 1ms. A 125W CO2 laser is used to strain the sample with a 25ms pulse length. To compensate for the poor flux on this timescale, a pump-probe method is repeated 1000 times and the resulting data are subsequently re-binned to improve statistics. A Gaussian weighting function is also used to introduce better contrast between strained and unstrained frames. TOPAS Academic is used for fitting with a Le Bail model in batch mode. Lattice parameters and sample height are refined during fitting, along with a Lorentzian line width for extracting microstrain broadening. Microstrains, epsilon, in the range of 1.01% < epsilon < 1.46% are reported on a 1ms timescale. [request reprint]  [papers]

Walking in Wales


Low cloud and a little snow on Pumlumon

Low cloud and a little snow on Pumlumon

Pumlumon Fawr from Nant-y-Moch
A surprise sunny cold spell at the weekend between two miserable, murky November weeks gave an opportunity for a quick ascent of Pumlumon Fawr from Nant-y-Moch reservoir. As the camera battery was playing up, I had to resort to using the phone to take pictures - with reasonable results. Starting from the minor road running up the eastern shore of Nant-y-Moch reservoir, I took the hydro track to Llyn Llygad Rheidol, waded through the stream emerging from its overflow and made my way up toward... [more]
Elenydd  10.2km  430m  3.5hrs   [more] [walks]

Other diversions


Swapping images with JavaScript

Swapping images with JavaScript

This is a JavaScript function to swap one image for another when the viewer clicks the picture. Repeated clicks toggle between the two images. [more] [other diversions]