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Diamond: Britain’s answer to the Large Hadron Collider

 
Diamond Light Source

The huge Diamond Light Source in Oxfordshire: inside it’s ‘like something out of Star Wars’. Photograph: www.diamond.ac.uk

 

Powered by Guardian.co.ukThis article titled “Diamond: Britain’s answer to the Large Hadron Collider” was written by Brian Clegg, for The Observer on Saturday 1st February 2014 20.04 UTC

The darling of particle physics might be the Large Hadron Collider (LHC) at Cern, but as a practical tool it’s no match for the UK’s Diamond Light Source. Located on the rapidly growing National Physical Laboratory campus at Harwell in Oxfordshire, Diamond is an alchemist’s dream, a place where beams of light 10,000 times brighter than the sun are deployed to probe the nature of everyday things.

Diamond is the Marmite of the physics world. Just as the sticky gunk left over from the brewing process was repurposed as a savoury spread, the light that streams from Diamond was originally the waste product of a particle accelerator.

Diamond’s 561m-diameter ring, which gives the building its distinctive circular shape, houses a synchrotron. Like the LHC, this is a particle accelerator, in Diamond’s case using synchronised pulses from powerful magnets to accelerate electrons to near the speed of light. Synchrotrons were part of the earliest particle accelerator technology, dating back to the 1940s, and were soon found to have an unwanted byproduct. Because they accelerated electrons, they generated light, known as synchrotron radiation.

When an electron accelerates it gives off energy in the form of electromagnetic radiation. Almost everyone owns an electron accelerator – the transmitters in mobile phones generate radio waves by accelerating electrons in aerials. But synchrotrons push electrons to relativistic speeds and the acceleration of electrons around the ring produces a whole spectrum of electromagnetic energy from microwaves, up through infrared, visible light, ultraviolet and x-rays.

This happens even though the electrons travel around the main storage ring at a constant speed, because acceleration is a change in velocity, which combines speed and direction. To keep the electrons in the ring they are regularly shifted through small changes of direction by steering magnets, each of which results in an acceleration and a blast of light.

In the early synchrotron light sources, such as Diamond’s predecessor at Daresbury in Cheshire, this acceleration round the ring was the sole source of light, but in a modern, so-called third generation ring, electrons are also given extra acceleration by passing them through a series of alternating magnets to force the particles into a pattern of repetitive oscillations. These devices are known as undulators if they produce a tight, narrow oscillation generating a narrow band of radiation, or wigglers if they produce a wider band.

Diamond Light Source

A rare glimpse inside one of the beamline diffractometers. Photograph: www.diamond.ac.uk

Around the storage ring are ranged beamlines, exit beams for the radiation, where work stations known unromantically as hutches house the experiments. In Diamond’s massive 45,000 sq metre floor space (around eight times St Paul’s Cathedral) there are currently more than 20 beamlines, with space for 40 in the final configuration. “When you walk into this big hangar of a place,” says Diamond researcher David Cole, “it’s like something out of Star Wars.”

Though Diamond is a massive project, constructed between 2003 and 2007 with funding split between the Science and Technology Facility Council (86%) and the Wellcome Trust, it was relatively cheap with an initial construction cost around one-tenth of the LHC’s £2.6bn. Of course, Diamond is not on the same scale of build, but in terms of what it delivers it more than compensates.

Each year, a remarkably wide range of projects compete for time on Diamond’s beamlines, which run 24 hours a day, outside planned shutdowns. The light produced here is beyond anything that a university could deliver in a lab. Diamond’s x-ray sources, for example, are 100bn times more powerful than a conventional x-ray tube. While it is possible to produce lasers that develop as intense a blast of light as a synchrotron source, they are nowhere near as flexible because a laser is limited to a narrow range of frequencies, where Diamond produces a wide spectrum. Practically every application of Diamond requires a different frequency, fitting the sample being studied.

 

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