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


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


Fourier transformation

Fourier transformation

These are notes of a Fourier workshop I used to run over three days for our 3rd year MPhys students. This is now covered in other modules, but I've decided to keep the notes online as they may be useful to someone out there. [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


Gallops, bales and ducks but no x-rays and no beer - the Ridgeway

Gallops, bales and ducks but no x-rays and no beer - the Ridgeway

This walk was a pleasant surprise arising from a disappointment: We were at Diamond Light Source to do some x-ray experiments on polymer films but a vacuum leak on the beamline meant that we had the afternoon off while Diamond's technicians were busy fixing the problem and pumping the system down again. Luckily I had some trainers and my camera with me, so we got to enjoy the sunshine and the scenery of the West Ilsley Downs instead. As the Ridgeway, an ancient track, runs along a ridge (the clue is in the name!) just south of Harwell Science Campus, we left the car at Bury Down right on the Ridgeway and walked west, with views of Didcot power station and the research centre we'd just escaped from. After a short while, we dropped off the Ridgeway towards West Ilsley. To do so, we had to cross some racehorse gallops (no racing horses in view), part of a network of grass gallops belonging to West Ilsley Stables. The view to the south included crop fields in the process of being harvested and straw bales being stacked, with some interesting geometrical patterns on the ground that I'm not used to from my usual moorland habitat. West Ilsley is a village with all the ingredients a stereotypical village is supposed to have: a cricket field, a pub (unfortunately closed for a nap in the late afternoon), a village green with resident ducks and a church. Having walked the length of the main street, we made the short ascent up Folly Down back to the Ridgeway and the car park. We did get our beer in the beer garden of The Lamb in Wantage later in the evening, and the rest of the beamtime went very well from the next morning, too. [more] [other diversions]