News


Half the Alltfedw circuit

Half the Alltfedw circuit

April 2018 - 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] [more external link]  [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


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


Riverside path with obstacles

Riverside path with obstacles

Gelli Ddu / Black Covert from Gelli Ddu/Black Covert NRW car park
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.
Elenydd  2.5km  10m  0.5hrs   [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]