Christoph Rau, Diamond Light Source
Part of the show Looking into the Light!
Christoph – So we are at the Beamline I13 for Imaging and coherence, and the purpose is imaging to imagine on the micro and nanometre scale.
Meera - So we’re currently just out on the outdoor grounds of Diamond and the synchrotron is quite a distance away from us. We can see it, so we’re now about 150m or so away. So this beamline is quite unique in itself in that it’s located out of the light source, it’s at this distance, and the hutch over there is about 250m?
Christoph – That’s correct. The reason for doing so is we want to make use of the property of coherence of light and for doing so you have to have a.) a very small light source and b.) to be very far away to have a large, lateral coherent field and that’s exactly why we are so far away.
Meera - So what do you mean by coherence?
Christoph – Coherence is a property of light. Light might have different characters, one is the feature of being a light particle or light might be considered as a light wave and then in this case we talk about coherence light.
Meera - So by coherent light, you mean light in its wave-form, not particle?
Christoph – Correct
Meera - and how is a beam of light maintained at such a large distance? So we’re currently about halfway between the light source and the beamline hutch, so we’re about 150, maybe about 125m away. We are stood on top of concrete and below us, within this concrete, are the tubes in which the beam of light will be travelling. What happens at either end of this tube to keep this light travelling straight through?
Christoph – Ok, so at the beginning we have the light sources which are undulators and each undulator generates the x-rays and they are canted to each other in a slight angle and further they propagate on the beamline, the more they get separated and to increase further the separation we put some mirrors at the beginning of the beamline so that at the end, where we are standing here now, we have roughly a separation of 4 metres between the two different branches.
Meera - So you have 2 beams of light coming over the hutch here from the source?
Christoph – That’s correct, yes
Meera - So if we just move into the actual hutch now to see the type of research that can take place at this beamline. There are 2 hutches at this beamline; and imaging and a coherence one. We’ve come through to the imaging one, but what kind of imaging will take place here?
Christophe - So on this branch, we have the now partially coherent light arriving on the sample and while the light is going through the sample, the light wave is deformed and what happens is that around the edges of the structures, the structures get enhanced, the light wave is deformed and then you can easily detect with a detector these enhance structures.
Meera - Therefore quite clearly seeing the edges and therefore the shape and structure of your sample?
Christoph - That’s correct, and that’s what is called the ‘edge enhancement’
Meera - What kind of samples will be looked at in this way?
Christoph - Basically any kind of sample which is opaque for the eye and which has interesting features on the micro-length scale. Applications are in the field of Biology, for example, Material Science, Geology, there’s a very large range of applications
Meera - And how does this compare to other imaging techniques, even those used in hospitals, so just a simple x-ray?
Christoph - The big difference is the resolution you can achieve. At the hospital, for example, the doctors are interested to learn about whether the bone is broken or not, here we are interested in questions like ‘Why does the bone break?’, ‘What is the mechanism behind this?’, ‘How can you improve any kind of mechanical behaviour?’ and so on.
Meera - Now this is the imaging hutch, but you mentioned there are 2 branches for this particular beamline, also a coherence one, which is about 4-5metres away from her, but in another hutch. What kind of work will be taking place, what will be looked at there?
Christoph - So here, for example, on the imaging branch we will do biomedical applications and Material Science, so we are interested to learn about, for example, cracks in material – that’s very important for Industrial applications, or for biomedical applications what I’m personally interested to learn about is hearing. We will study the mechanisms which are happening inside the cochlea.
Meera - Christoph Rau, Principal Beamline Scientist at Diamond’s Imaging and Coherence Beamline.