Lord of the rings

At 600m in diameter, Oxfordshire’s Diamond particle accelerator will produce the world’s brightest synchrotron light when it goes online in 2012.

It will cost £350m and take nine years to build. It will present huge challenges for the engineers designing it and bring ‘once-in-a-lifetime’ opportunities for advances in materials technology in sectors such as aerospace. It is the Diamond synchrotron – the UK’s biggest research project for 30 years, yet one with a profile in inverse proportion to its massive scale.

Few may have heard of it, but when completed in 2012 Oxfordshire’s Diamond will propel the UK into the world synchrotron big league. It will supersede the country’s existing facility at Daresbury in Cheshire and create the world’s brightest source of synchrotron light.

A synchrotron is a particle accelerator that acts as an extremely powerful microscope, using X-rays, infrared and ultraviolet light to reveal the atomic structures of even the most impenetrable materials.

The X-rays generated by Diamond, currently under construction at the Rutherford Appleton Laboratory (16km south of Oxford), will be 100,000 times brighter than those used in hospitals. This light will be used in research ranging from the stresses on aircraft engines to the magnetism of metals and medical research to develop new drugs.

Diamond researchers will be able to conduct 90 per cent of the same research conducted at the much bigger European Synchrotron Radiation Facility (ESRF) in Grenoble, France, but at far less cost thanks to the use of state-of-the-art technology in all aspects of its design.

The Diamond synchrotron is a doughnut-shaped structure with a diameter of 600m. The scale of the building is in stark contrast to its mission – to make measurements accurate to one micron. It is the kind of precision that could be ruined by a lorry running over a speed-bump half a mile away.

Prof Gerhard Materlik, chief executive of operating group Diamond Light Source and a world-renowned synchrotron expert who since 1974 has worked on installations in Germany, France and the US, is in no doubt about its significance.

Materlik claimed Diamond is a ‘unique project’ and a ‘once-in-a-lifetime chance’ with applications well beyond pure academic research. When it is up and running there will be major opportunities for industrial research in the aerospace industry, polymer science and nanotechnology, among other areas.

‘Issues like how a material is going to age, or how it is going to crack, or how it responds to strain need to be addressed by studying the structure of the material in detail. For that you need X-rays, and with synchrotron radiation you can study on the scale of atoms,’ said Materlik.

‘You can find out when, where and under what circumstances a material will crack. For example, you can study turbines while they are rotating to see where the weaknesses are. This is work we are hoping to do with Rolls-Royce,’ he added. Materlik hopes that up to 20 per cent of Diamond’s capacity will eventually be used for industrial R&D.

The synchrotron is composed of two concentric, connected rings consisting of straight and curved sections. At its heart is a huge particle accelerator that forces electrons around its circumference at almost the speed of light.

Electrons are fired into the inner ring from an electron gun, where oscillating electromagnetic fields are used to accelerate them. From the inner ring the electrons pass into the larger area, known as the storage ring, where they are held tightly in powerful magnetic fields. In the straight sections are arrays of focusing magnets which narrow the electron beam to less than 1mm. In the curved sections there are high-powered magnets to guide the electrons around the ring.

As the electrons travel around they give off energy in the form of light. This is known as synchrotron light, or synchrotron radiation, first fully exploited in the UK more than 20 years ago. The light is channelled off into tubes, known as beamlines, placed at regular tangents around the ring.

Blasting the light on to tiny samples of any material gives an insight into its internal structure more detailed than any other method. By altering the wavelengths and energy levels of the beamlines, researchers can choose from a range of inspection and measurement techniques.

The most common is diffraction, whereby X-rays passing through a sample of material bounce off the atoms or molecules inside it.

The reflected beams interact with each other, sometimes cancelling each other out, sometimes joining together. These interactions produce a distinctive pattern that is unique to the atomic or molecular structure of the material. This is particularly useful in determining the structures of chemical compounds and electronic and magnetic materials.

Another technique involves microfocus beams, which will observe tiny structures such as clusters of metal atoms. Infrared beams can be used in forensic analysis and cancer diagnosis.

Diamond will have 22 beamlines when it is completed in 2012, with each being tailored for a different area of research. Up to 18 more could be added if there is sufficient demand from researchers prepared to meet the cost.

At the practical end of this vision is Dr Alexander Korsunsky, an Oxford University lecturer who currently conducts synchrotron research for Rolls-Royce. Korsunsky has used X-ray diffraction at the UK’s existing synchrotron light source in Daresbury to measure residual stresses in nickel superalloy components of an aero-engine.

Residual stresses arise due to manufacturing processes such as forging, machining and welding. Their magnitude and nature are major factors in improving aero-engine designs.

Although Korsunsky’s team were able to conduct some research in this area, they found themselves hampered by technical difficulties. ‘The limitations stem from the size and weight of the objects that need to be studied. Components often measure nearly 1m in diameter and weigh over 50kg,’ said Korsunsky.

‘Developing and installing the mounting and manipulation systems for these purposes is not a trivial engineering task. The advent of the new Diamond synchrotron provides opportunities for incorporating these capabilities from the start, and using them in combination with a brighter and more powerful source of X-rays,’ he said.

Korsunsky is involved in a proposal for a Diamond beamline called the Joint Engineering, Environment and Processing station (JEEP). This will be dedicated to recreating realistic engineering environments to test engine parts or aeroplane wings under the same strain they would experience in flight, ‘It will provide unprecedented opportunities for advanced design for performance and structural integrity,’ said Korsunsky.

But before this can happen there is still much work to be done at the Diamond synchrotron. The project is still in its first building phase. The outer metal shell of the ‘doughnut’ is still under construction, due for completion later this year. The installation of the actual machinery – the electron gun, magnet arrays, beamlines and research equipment – is due to begin in September.

Construction of such an enormous structure, combined with such sensitive scientific equipment, is bound to throw up countless unplanned engineering problems. The first of these has already been overcome. The Rutherford Appleton is built on soft chalk which is susceptible to tiny, usually imperceptible movements in the earth.

But these movements can throw a sensitive measuring device completely off-kilter. The engineers had to insert 1,500 reinforced concrete piles 12m into the ground all around the synchrotron to gain the maximum level of stability at a cost of some £2m.

According to the Diamond team, it is this type of consultation between the engineers building the structure and the researchers who will use it that will make its synchrotron the best in the world.

The engineers designing the UK facility have learned important lessons from ESRF and synchrotrons elsewhere. For example, after the ESRF was completed the researchers using it found that vibrations in the earth were interfering with their equipment. After an extensive inquiry, lorries driving over a speed bump some distance from the synchrotron were found to be the source of the vibrations. It had to be removed before the facility could function normally.

Despite the obvious pride the engineers and researchers feel about the project, they claim there is no competition between research facilities. Prof Materlik talks of a ‘synchrotron research community’. He claimed its members ensure that all facilities are complementary, rather than competitive.

In fact, Materlik himself sits on the advisory committee for the French national synchrotron, called Soleil, which is due to open at around the same time as Diamond.

Despite this camaraderie, however, one senior scientist at Diamond couldn’t resist pointing out that ‘our synchrotron will be bigger and better than theirs’.

<b>Three generations of synchrotron light</b>

In 1980, the UK achieved a world first with the construction of a particle accelerator entirely dedicated to research using synchrotron light. The Synchrotron Light Source (SRS) in Daresbury, near Warrington, Cheshire, marked a coming of age for synchrotron radiation.

Until then synchrotron light had been a largely unexplored by-product of particle physics experiments. Particle physicists had used accelerators known as ‘atom-smashers’ for atom-splitting experiments since the 1930s.

By the 1940s it had become apparent that the particles gave off light – synchrotron light – as they hurtled around the accelerator.

During the 1960s curious chemists and biologists established their own research projects within the accelerators to experiment with synchrotron light. But the facilities were still run by particle physicists — synchrotron researchers were known as ‘parasites’ and could only use beams when the physicists did not need them.

These early parasitic research facilities are known as ‘first-generation light sources’. Although it used largely the same technology as the first generation, the UK’s SRS was the first facility to be dedicated to synchrotron light research – a second-generation light source.

Third-generation light sources such as the Diamond are defined by a huge increase in the brightness of the X-rays and an improvement in the ability of scientists to manipulate the kind of light emitted by the accelerator. These improvements are due to the development of magnetic systems known as ‘undulators’ and ‘multipole wigglers’. They increase the intensity and brightness of the beams of light by forcing them to wiggle or undulate.

The first purpose-built third-generation light source was for the European Synchrotron Radiation Facility (ESRF), in Grenoble, France, which opened in 1994. Diamond will be the newest addition to a family of European third-generation synchrotrons, which includes facilities in Germany, Spain, Sweden and Switzerland. Other significant third-generation synchrotrons are the Advanced Photon Source (APS) in the US and the Spring-8 synchrotron in Japan.

Fourth-generation light sources are still in an experimental stage with research being conducted in the US and Japan, and a proposal to develop the Daresbury site.Fourth-generation sources would give off one extremely intense flash of light to provide researchers with all the information they require.

<b>History of the diamond</b>

The Diamond project was first proposed following a 1993 government study into the research carried out by UK scientists at synchrotron radiation facilities here and abroad. The Woolfson Report looked at the UK’s existing synchrotron in Daresbury, which was due to be decommissioned by 2000 (though is now expected to keep running until 2008).

It also examined the ESRF in Grenoble, a joint European project at which UK researchers are entitled to around 15 per cent of the beam time.

The report concluded that the UK needed a new light source to fulfil the needs of its scientists. Both the government and the scientific community agreed with the findings, but the fledgling project floundered for five years amid financial and political indecision.In 1998 independent research funding body The Wellcome Trust came up with an offer of more than £100m towards construction and maintenance costs if the government made up the rest.

The main question was where to build the new synchrotron. Two sites were proposed: the existing site at Daresbury or the Rutherford Appleton Laboratory (RAL) in Oxfordshire.

The following two years were dominated by a fierce political row along north/south lines that threatened the future of the project. Eventually, amid bitter recriminations from the northern lobby, RAL was chosen.

An idiosyncratic intervention from the French in 1999 compounded the confusion. They offered £35m for a share in the project on condition that RAL was the site. A year later, just as Oxfordshire was confirmed as the location, the French pulled out entirely after deciding to build their own synchrotron just outside Paris.

A joint venture between the government and The Wellcome Trust, which agreed to take a 14 per cent stake in the project, was set up in March 2002 and building on the Oxfordshire site began a year later.

By January 2007, phase one of the Diamond project will be complete and up to seven of the beamlines will be operational. Fifteen more beamlines will then be built, culminating in all 22 being operational by early 2012.