News


ASAXS experiment on CIGS films at the ESRF

ASAXS experiment on CIGS films at the ESRF

September 2015 - Nathan and Rudi were joined by Armin Hoell and Xenia Erler from the Helmholtz-Zentrum für Materialien und Energie at Berlin for an Experiment at beamline ID02 at the European Synchrotron Radiation Facility (ESRF) at Grenoble. This experiment was aimed at validating our absorption-contrast technique (ac-SAXS) for fast energy-dependent x-ray scattering experiments against the established but slower method of anomalous scattering (ASAXS). The local beamline team, Peter Boesecke and Michael Sztucki gave us excellent support and ensured the experiments went smoothly. [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


Strumbling about the north Pembrokeshire coast

Strumbling about the north Pembrokeshire coast

Strumble Head from Strumble Head
There were some doubts about the weather prospects for this bank holiday Saturday, but the Met Office produced excellent advice: go south rather than north, and stick to the coast, so Strumble Head it was. Despite the bank holiday, there was still plenty of parking space by the lighthouse when we arrived, and the weather was glorious. The route followed all the narrow inlets of Pembrokeshire's fractal coast, but we turned inland at Carregwastad Point and cut across the Strumble headland toward... [more]
coastal  14.2km  230m  4hrs   [more] [walks]

Other diversions


Exploring the water mills of the Loxley valley

Exploring the water mills of the Loxley valley

A group of Geograph-ers met again the morning after the Geograph conference 2012 to walk the Loxley valley from Malin Bridge to Stacey Bank. Alan Murray-Rust had prepared a map and factsheet for each participant showing the locations of all the former mills along the way. Setting off from the tram stop, we soon left the road and followed a footpath along the river, seeing the sites of Wisewood rolling mill and forge on the way. The rolling mill at Little Matlock is still in operation, though no longer water driven. Not much is left of Olive rolling mill, although the very deep tailrace of the mill and former mill workers' accommodation can still be seen. Upstream, there is evidence of water management from the times when the amount of water to be taken from the river at various sluice gates had to be agreed to make sure all mills could run. The former compensation reservoir at Stacey Bank, just at the foot of the dam of Damflask reservoir, also served this purpose. At the end of the walk, we retired to the Nag's Head inn at Stacey Bank for drinks and food before everyone headed home. [slideshow] [more] [other diversions]