The Brightest Diamond; Synchrotron, that is...

21 October 2007

Interview with

Richard Walker & Sanjeet Dhesi, Diamond Synchrotron; Tim Wess, Cardiff University

Earlier this week, HM the Queen and the Duke of Edinburgh opened the Diamond Synchrotron in Oxfordshire.  Now this very expensive device creates very high energy electromagnetic radiation (that's known as synchrotronic light) and it's filtered to give you and extremely intense x-ray beam which is hundreds of times more powerful that the one you'd get in hospital.  We sent Meera down to the site this week to find out how it works and the benefits of using such high-energy light.

Meera -   Hello, this week I'm at Diamond Light-Source out at Didcot, Oxfordshire to find out about the giant particle accelerator located out here known as the synchrotron.  Now the building itself is huge, silver and doughnut-shaped.  And to give you an idea of just how big it is, it apparently covers the area of five football pitches.  What I'm here to find out about is, 'what is a synchrotron, what does it actually do and how does it work?'  I'm also going to be finding out just how this technology is being used to benefit everyday life and even to uncover ancient messages hidden in parchment such as the Dead Sea Scrolls.  To answer the first of my questions is Richard Walker who's the Technical Director of Diamond Lightsource.  We're actually here inside the synchrotron now.  What exactly is a synchrotron?

Diamond LightsourceRichard -   A synchrotron is a particle accelerator; in the case of Diamond we accelerate electrons.  We accelerate these in a large circular machine, about half a kilometre in circumference where they reach very high energy.  The energy is 3000 million volts and at that energy they give off very large amounts of electromagnetic radiation when they're bent to maintain their circular orbit.  It is this electromagnetic energy, called synchrotron light that we use in the experiments.

Meera -   We're inside the synchrotron itself, where are we standing?

Richard -   Well, we're actually stood in the linear accelerator which is the first part of the acceleration system.  Right at the beginning, where the electrons come to life and they're liberated from the atoms in an electron gun.  The electron gun fires the electrons into the linear accelerator where they're accelerated up to 100 million volts.  From there they're transferred into another synchrotron, a booster synchrotron where they're accelerated up to the final energy of 3000 million volts before they're injected into the storage ring.

Meera -   They're bent round. Is this done using magnets?

Richard -   We use a large array of electromagnets, both to bend the electrons that form the circular orbit and also to focus them and keep them very tightly compressed.  It's the small size of the electron beam that gives rise to very bright synchrotron light that we want to generate and use in our experiments.

Meera -   So now I know how the synchrotron actually runs, but what benefit does this high beam of light actually provide?  I'm with Sanjeet Dhesi who's a principle beam-line scientist here at Diamond.  What, exactly, is a beam-line?

Sanjeet -   A beam-line is a series of x-ray optics that helps channel the light that's produced in the machine all the way down to the sample where we have an electron microscope that we use to study anything from magnetism to chemical reactions on a surface.

Meera -   So we're outside your nano-science beam-line now.  What is this in front of us?  How is this beam line being channelled?

Sanjeet -   If you take light into a camera you use a series of lenses to focus the light onto your film.  If you try to do that with x-rays, the x-rays just go straight through the lens.  Instead of using lenses you have to use mirrors.  The beam-line is actually a series of half a dozen mirrors that take the light and channel the light and focus the light down to our sample where the light is only a tenth of the width of your hair but it has about 1000 billion times the intensity of a hospital x-ray source.

Meera -   How many beam-lines are there here at Diamond?

Sanjeet -   In phase 1 of Diamond there were seven beam-lines that were constructed.  You can do anything on a beam-line from looking at the structure of a protein to understand how a virus attacks your body to looking at structures under extremely high pressure and extremely high temperatures.  That's important, for instance, for understanding how iron behaves at the Earth's core.  There's a whole host of ways that x-rays interact with matter to work out exactly what's happening at the fundamental level of the atomic scale.

Meera -   So extremely variable fields of science are being explored using this synchrotron light but it's not only science that's benefiting.  Scientists are also trying to learn more about history.  Professor Tim Wess and his team at Cardiff University have been using synchrotron light to understand the texts of ancient parchments such as the Dead Sea Scrolls: potentially enabling them to read the scrolls without having to unravel them.  I've got Tim here with me now.  Hello Tim.

Tim -   Hello Meera.

Meera -   What made you start working with ancient parchments?

Tim -   Well, what a lot of people don't actually know is that parchment's actually made out of dried skin and therefore that's made out of collagen.  I've been working with synchrotron radiation to understand the structure of collagen for about the last 20 years.  What we've been trying to do is see how intact the collagen is in a piece of parchment because what happens to parchment as it gets older and the control mechanisms of repair are lost when we're looking at something which is no longer in an animal, you begin to see that the collagen deteriorates into gelatine.  Collagen is really like a little rope molecule which really gives us the strength in our tissues, tendons, our bones and our skin.  When it deteriorates into gelatine usually in our body it's taken away and recycled but in a document like an historical parchment the gelatine just sits there.  It's lost its strength; it likes to take up water which means the gelatine actually becomes a jelly.  Therefore, the parchment becomes very fragile, brittle and very, very difficult to unfold and read or handle.

Meera -   So how are you using synchrotron light to overcome this problem?

Tim -   First of all, we can begin to detect without hopefully damaging the piece of parchment how intact it is.  Using the synchrotron, we have a very fine beam of x-rays we put through the parchment sample.  The way that the x-rays interact with the matter tells us about the state of the matter that's present.  We get a very distinct signal for the way the x-rays are scattered with collagen and a different one for gelatine.  We can begin to tell the difference between those two and then advise on the collagen-to-gelatine ratio in any of these samples.  We have looked at the Dead Sea Scrolls here using the scattering to try and understand the damage that's occurred to the Dead Sea Scrolls because what we're finding is that the caves that the different samples were coming from seem to have affected how stable they are and how they've managed to stay intact.  When we find that a sample has been so badly damaged that it shouldn't be displayed or unfurled, there's a second approach with the synchrotron that we can begin to use which really relates to a process called tomography.  We pass an x-ray beam through an object then the picture we get depends on presence of things like writing on the surface of the parchment so from that we can take lots and lots of pictures at different angles of the piece of parchment.  Whether it's a rolled up piece of parchment as a scroll, we can then reconstruct on a computer from all the different absorption patterns that we have what the original object was.  And that's where we've begun to realise that using the ink on parchment, on the surface of it, we can read objects which we would really not be able to unroll.

Meera -   So there you have it.  Irony at its best.  This giant silver doughnut is enabling scientists to probe matter down to tiny atomic scales and this extremely new technology is going to provide answers to questions and beliefs that go back thousands of years.

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