“Is that like a transformer?”
I’ve just been to Japan for a synchrotron school. Most of my non-scientist friends had never even heard of the word ‘synchrotron’ before I told them where I was going. One friend thought it sounded like something from the movie ‘Transformers’. Fortunately, Mike’s latest post will help you tell the difference.
Others friends have heard of the Large Hadron Collider and they assume that I must be doing particle physics. But I’m not – I’m a geologist.
‘SPring-8′ synchrotron, Japan
This is the synchrotron facility called ‘SPring-8’ in Japan, where I’ve just spent ten days learning all about how these things work and what you can do with them. So what do they do and why, as a geologist, would I go there? And what does it look like, inside?
Being a geologist means that I want to learn about the Earth. As children, most of us grow up learning a lot about the world by seeing. The sun’s light reflects off the things around us and enters our eyes, which send signals to our brain. But there is a limit to what we can see with our eyes, and with light from the sun.
In my lab at the Research School of Earth Sciences, I make lava – molten rock – and cool it so quickly that it turns to glass. I want to find out how the atoms are arranged inside the glass, and how that arrangement might change with pressure. But that’s not something I can see with sunlight and my eyes. Instead, I need a different type of light – I need x-rays.
But I can’t just use any old x-rays. When you break an arm you might get an x-ray that illuminates your whole arm, but I need to look at atoms, so I need to focus all that light into a very small spot – like the difference between a light globe and a laser pointer. Both might have the same power, but because the laser pointer is so focussed, it illuminates small areas much more brightly.
So I need very bright, focussed x-rays. Unfortunately it’s not easy to make an x-ray laser*. This is where synchrotrons come in. A synchrotron is a light source, and I need it to generate light that will help me “see” the results of my experiments, and hopefully understand something new about the Earth.
Okay, but why does it look like a doughnut?
That’s because of the way synchrotron light is produced. Inside the doughnut-shaped building, there is another doughnut-shaped, er, room (?) … called the “storage ring” which has walls at least a metre thick. Inside the storage ring, there is a length of metal tubing that goes all the way around, surrounded by different types of magnets. Inside the tubing, electrons are flying through, around the ring, at close to the speed of light. The magnets keep all the electrons going in the right direction – not in a circle but in a big polygon with straight sections and bends. So, it’s called a storage ring because this is where the electrons are stored. When the electron beam is forced to bend, x-rays (and other wavelengths of light) are produced, and this light is funnelled out of the storage ring and into a “beamline”.
Did you just skim over that paragraph, wondering why I got so excited about magnets and electrons and metal tubing? I’m describing it because this is the real heart of the synchrotron, and this is not something you usually get to see. Even if I’d known all this stuff was in there (which I didn’t), seeing it for myself really helped me understand what was going on.
Inside the storage ring.
So I want to share two cool things that I saw inside the storage ring, and both of them are evidence that not all of the x-rays go to the beamlines, but some get scattered and escape (that’s why you need the walls to be so thick).
(1) Have you ever left some paper on the windowsill, and found after a couple of weeks it turned yellow? In this photo, the same thing has happened to the floor, but with x-rays. The floor has been discoloured except for the region in the ‘shadow’ of the metal strut.
X-rays causing discolouration of the floor, but the metal strut has cast a shadow.
(2) This telephone. I took a photo because it seemed strange to see such old technology while standing in the heart of such high-tech facility. As it turns out, the x-rays in the storage ring tend to kill electronics, proving the worth of the trusty analogue phone.
Also inside the storage ring.
Though some get scattered, most of the x-rays do get captured and sent down into the beamlines – and this is where the science happens! What kind of science? It turns out, a lot! I was surprised to find myself one of only four earth scientists out of 77 students on this course. The majority of students seemed to be in biological research doing protein crystallography. Until now I didn’t even know that proteins formed crystals! There were also students working on topics ranging from the properties of rubber and plastic, to nanoparticles in the environment, to the motion of atoms in solids.
So, synchrotrons are not aliens, nor do they involve smashing particles together. They are facilities that produce bright and focussed light useful to a wide range of science and engineering.
* X-ray lasers have just started to be developed. There are three in the world, and the smallest one is 900 m long. You can actually see this facility in the photo of SPring-8 above: it’s the long building above and to the right of the synchrotron.