News


A small circuit into Cwm Rheidol from Pontarfynach/Devil's Bridge

A small circuit into Cwm Rheidol from Pontarfynach/Devil's Bridge

August 2018 - A quick evening wander into the Rheidol gorge, starting from the centre of Pontarfynach/Devil's Bridge, where there is usually ample parking space by the side of the main road. After following the road in the direction of Aberystwyth up to the edge of the village, we took a gate to follow the path over grassland to the edge of the gorge, just above the Vale of Rheidol trackbed. The path then follows along the edge of the wooded slope and alternates between grassland and broadleaf forest. ... [more] [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


Partial Differential Equations

Partial Differential Equations

I no longer teach this module but have decided to leave the notes online for general reference. Following a brief review of ordinary differential equations, these pages deal with partial differential equations in detail, with applications across physics. Separation of variables, physical boundary conditions and Fourier expansion are introduced using the Laplace equation to determine a temperature profile in a hot plate. These techniques are subsequently transferred to the Poisson, diffusion and wave equations. The lecture ends with an introduction to Fourier transforms.
Dyma fersiwn Cymraeg y tudalennu hyn hefyd. [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


A small circuit into Cwm Rheidol from Pontarfynach/Devil's Bridge

A small circuit into Cwm Rheidol from Pontarfynach/Devil's Bridge

Cwm Rheidol from Pontarfynach/Devil's Bridge
A quick evening wander into the Rheidol gorge, starting from the centre of Pontarfynach/Devil's Bridge, where there is usually ample parking space by the side of the main road. After following the road in the direction of Aberystwyth up to the edge of the village, we took a gate to follow the path over grassland to the edge of the gorge, just above the Vale of Rheidol trackbed. The path then follows along the edge of the wooded slope and alternates between grassland and broadleaf forest. ... [more]
Elenydd  5.4km  230m  2hrs   [more] [walks]

Other diversions


A sightseeing walk in Paisley on a dreich January morning

A sightseeing walk in Paisley on a dreich January morning

While in Paisley for work, I had a quick walk around the town centre before heading back down the M8. The light wasn't great on this grey January day but it was dry and I managed to get some shots of the University, Town Hall, Paisley Abbey and the Coats Observatory. I'll be back in the summer! [more] [other diversions]