News


Riverside path with obstacles

Riverside path with obstacles

April 2018 - A quick evening stroll from the National Resources Wales car park at Gelli Ddu/Black Covert near Trawsgoed. This is just a flat walk through mixed woodland by the side of the Afon Ystwyth. On this occasion, the path was blocked in several places because windblown trees were scattered throughout the forest. This necessitated a few detours to the edge of the woodlands, with views across farmland in the Ystwyth valley. [more external link]  [other news]

Recent beamtime


Anomalous scattering of chalcopyrite films at the ESRF

Anomalous scattering of chalcopyrite films at the ESRF

In recent years, we have developed absorption-contrast SAXS as a fast scattering technique able to exploit chemical contrast in heterogeneous samples using fluorescence correction. This makes the interpretation of scattering patterns in complex materials less error-prone, and the speed of the technique allows it to be used for in-situ experiment on a time scale of seconds. In this experiment, we wanted to benchmark our technique against the established but much slower method of anomalous scattering (ASAXS), so we loaded a range of Cu(In,Ga)S2 films on mica substrates into a sample changer and took data at six energies each around the Cu and Ga K-edges. A very relaxed beamtime by our (usually in-situ) standards - we even managed to escape the lab for a walk up the Bastille while the sample changer did all the work! [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


Half the Alltfedw circuit

Half the Alltfedw circuit

Coed Alltfedw from Gelli Ddu/Black Covert NRW car park
National Resources Wales provide a car park by the Afon Ystwyth near Trawsgoed with two waymarked paths. One of them leads onto Alltfedw, a low ridge to the east of Llanilar and ending fairly abruptly at Trawsgoed. It is mostly covered in forest (Coed Alltfedw). Unfortunately, there had been significant storm damage recently, which hasn't been cleared yet. However, the lower part is accessible with care, while I had to turn round near the summit because the toppled trees were piled up or l... [more]
Elenydd  3.4km  120m  1hrs   [more] [walks]

Other diversions


Along the Sheffield & Tinsley Canal into Sheffield

Along the Sheffield & Tinsley Canal into Sheffield

On the Tue afternoon before the 2012 Geograph conference in Sheffield, a group of Geograph-ers met at Meadowall South / Tinsley tram stop for a walk along the canal to its terminus at Sheffield Canal Basin on the edge of the city centre. The walk passes a flight of locks at the Tinsley end to take the canal up towards industrial Attercliffe. The canal then runs in a fairly deep trench, with the tram and several foot and road bridges crossing it at considerable height. Finally, the canal opens into Sheffield Canal Basin at the city end, where several original warehouses are still present, including the Straddle, built across the canal with five loading bays. After the walk, we dispersed briefly to sort out our hotels and then met in the Fat Cat, Kelham Island Brewery's pub, for beer and pies. [more] [other diversions]