Diamond

A friend of mine from university, Dr Mark Basham  is a data acquisition scientist at the Diamond Light Source, a 3rd generation synchrotron, built at the Rutherford Appleton Laboratory near Oxford.  As a physics graduate myself I've been itching to get a tour of the place and towards the end of last year I got my wish!

The Diamond complex consists of a linear accelerator (1) which is pretty much a beefed up TV tube.  This fires electrons into the synchrotron (2 - the smaller, inner ring) which accelerates them up to 3 Giga electron Volts (3GeV).  Just to put this into perspective,  during the nuclear fission of a Uranium 235 atom 'only' 210MeV of energy is released (equivalent to 20kilotons of TNT). 

Once accelerated, they are passed into the storage ring (3 - the larger, outer ring) where they travel at close to the speed of light. 

Part of why synchrotrons are so cool is that hugely powerful magnets are used to steer the electron beam around the ring and as they pass through these magnets 'synchrotron radiation' is given off in the form of highly energetic x-rays, ultra-violet light and infra-red rays.  It is at these points where the beam lines (4) come in to allow you to do some really exciting science!

The beam lines are where all the experiments are done.  They are basically a big box (6,7,8) of electronics, mechanics and computers that look through the 'window' through which the synchrotron radiation is emitted.  They are heavily shielded, in some cases with inches of lead, and are very expensive.  If I remember correctly a 'blanking plate' (for those places where beam lines are still to be built) cost over £1/2m!).

This equipment basically allows the beam to be tuned, processed, attenuated etc so it is correct for the current sample. 

The samples are what this entire place is about.  They can be anything you can think of, viruses, plastics, alloys or even chocolate.

The beam line that Mark works on has a multi-axis (like 50 or something) robotic sample container which allows the material being analysed to be swivelled, rotated, translated in various directions at high speed and high precision.

The accelerator and the storage ring operate in close to vacuum conditions, but it is impossible to remove all of the atmosphere.  This means periodically an electron will strike a stray atom, causing particles to veer off on random trajectories.  If one of these particles collides with the casing it is likely to cause another particle to be ejected, and so-on and so-on until the energy from the initial collision is dissipated.  This is called a 'resonance cascade'.

Yes.  I have a friend who has a PhD in theoretical physics and who works at a particle accelerator facility which experiences 'permanent resonance cascade reactions'.

Just to be on the safe side he's got this on his desk...

 

...can you spot it?