Tuesday, 13 May 2014

Diamond Light... by Daniel Parkes

from left to right: Jeremy Rushton, myself [Daniel Parkes] and
Tony Milodowski at the Diamond Light Source, Didcot
Following on from the interest in Barry's post about the amazing Diamond facility and the search for carbon here's team member Daniel Parkes to tell us more about the trip...

In late April I was one of a team of four staff from Mineralogy and Petrology to travel down to the Diamond Light Source near Harwell, Oxfordshire. Diamond is the UK’s national syncatron facility; the main building is a huge half-kilometre wide circular structure. The shape is governed by the central ring, which consists of a tube encased in electro-magnets and is used to accelerate electrons to colossal speeds; the electrons at diamond are travelling fast enough to circumnavigate the globe 7.5 times a second. At certain points around the ring different electro-magnets bend the electrons causing them to lose energy in the form of X-rays and long-wavelength light. The generated X-rays and light are directed away from the main ring and down what are known as ‘beam lines’. Each beamline has a unique application and the generated x-rays are used for a wide range of applications ranging from the 3d-imaging of fossil interiors to the study of vaccines and viruses. Our aim was to use the X-rays to investigate and tomographically image the organic matter distribution in soils, in order to better understand the factors controlling microbial mineralisation in relation to the turnover of soil organic matter and global climate change.

In order to image the samples the soils had to be specially prepared by Jo Wragg and Gemma Purser at the BGS. Gemma carried out gas chromatography (GC) on the samples in order to pick four soils with high microbial mineralisation rates (high CO2 production) and four with low microbial mineralisation rates (low CO2 production) Jo Wragg then doped the samples with osmium, osmium was used as it readily binds to organic matter and is considerably denser than the soil, so it was hoped it would give a good contrast images (as x-ray absorption is a function of density) of the organic matter distribution when scanned with the x-rays.

Working hard
Arriving at Diamond on Tuesday night there was a chance for a built of team building in the form of a Nepalise curry and a few character building (for Tony and Jeremy) games of pool. The next day, while the beamline staff set up the experiment, which included calibrating the machine and finding the Osmiun ‘edge’ (the energy at which osmium begins to absorb x-rays), we had a fairy intensive safety course which due to the serious consequences of being trapped in the experimental area or ‘hutch’ when the x-ray beam is switched on, included learning how to carry out a thorough search of the experimental area.

Long hours!
The plan was to carry out the 24 hr (the syncatron is constantly running as it is in such high demand and takes a lot of energy to start up) scanning of the samples in pairs, each working on 12 hr shifts, me and Tony settled down for the first night shift with the initial help and guidance of our dedicated beam line scientist Christina. Unfortunately we ran into a number of contrast related problems with the imaging software that meant it was difficult to correctly align our samples in the beamline, these continued into the following day and were eventually sorted when a fried £10,000 mirror in one of the recording cameras was replaced in classic ‘bodging’ style with a piece of reflective silicon. This allowed us on Thursday night to run all of our samples in one long effort; unfortunately the images that were produced were very blurry due to another mirror being knocked out of alignment when installing the piece of silicon. This meant that on Saturday night after some re-calibration work by the beamline scientist we had to re-run all our samples, thankfully this time we managed to capture an excellent set of data.

Barry Rawlins remained at Diamond for an extra day in order to process the images and is planning to carry out further statistical work in order to investigate the relationship between the amount of microbial mineralisation and the physical isolation of SOM, which will hopefully play a part in the better refinement of models relating to soil structure and organic matter turnover.

Personally the trip was a great opportunity to be involved in a project that allowed me to visit and learn about a fantastic science facility and also be involved in some new research that will hopefully for the basis of some high impact science for BGS. Overall a great experience and if anyone has the opportunity I would thoroughly recommend a trip to Diamond.

By Daniel Parkes

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