Heart of the matter

The UK leads the way in neutron research, but if the government does not commit to bidding to build the world’s highest-intensity spallation source we will lose our premier position. Julia Pierce reports.

If you were to draw up a list of the world’s greatest research institutions, the likes of CERN, MIT and Sandia would quickly spring to mind… but Burn Airfield in North Yorkshire?

If a bid for a £1bn ‘matterscope’ is successful, in 10 years’ time this relatively unheralded part of the country could be transformed into an international centre for neutron science.

The project revolves around the European Spallation Source (ESS). This would fire high-energy protons at liquid mercury to chip off – or ‘spall’ – neutrons that can be used to probe deep into matter.

The UK currently leads the world in neutron research. The Rutherford Appleton Laboratory near Oxford is home to ISIS, which with its 250kW beam is Earth’s most powerful spallation source. When built, the ESS will claim this honour with a beam intensity of 10MW, but with other European bids on the table and rival international projects gathering pace, the UK must act quickly if it is to avoid surrendering its dominant position.

Using the ESS, researchers will have the capability to obtain vital information concerning the structure and function of materials from plastics to semiconductors, furthering the development of areas such as low loss transmission of electrical power, medicines that are free from side effects and lighter, safer vehicles. Scientists will be able to observe events such as stress fractures within a composite aeroplane wing or the lubrication layer in a running engine.

While EU governments agree that the ESS should be built, the question of where it should be sited and who will provide funds has caused the project to stall. However, Yorkshire-ESS (YESS) — formed from the White Rose University Consortium comprising the universities of Leeds, Sheffield and York— and Yorkshire Forward, the Regional Development Agency for Yorkshire and Humber are now attempting to rekindle enthusiasm and secure the ESS for the UK.

It is estimated that the facility could attract up to 5,000 scientists and is likely to become the site of various spin-off facilities, just like the ILL High Flux Reactor and the European Synchrotron Radiation Facility, both in Grenoble, France. Bob Cywinski, professor of physics at Leeds University and scientific and technical advisor to YESS, which was involved in the creation of ISIS between 1980 and 1985, said the facility would have numerous applications.

‘This is a matter of looking at, for example, a failed railway line or superconducting systems. You can probe things such as buckyballs (C60 molecules) and look at their atoms and the forces holding them together. X-rays can’t see hydrogen atoms, but neutron sources can. So you could take materials and change their structure to make them behave how you want. You can look at the strain on railway rails or put a car engine in the beam and see it working. The neutrons will enable you to look through the metal in the same way that X-rays look through flesh. You can even see how polymer strands move against each other. Any area of science and engineering that is interested in solid materials will benefit.’

There is a great need for a new European neutron facility. Over 4,500 neutron research scientists (also known as neutron scatterers), two-thirds of the world’s total number, reside in Europe to exploit facilities such as ISIS. However, the pace of scientific advancement means that ISIS is becoming outdated.

The US and Japan are presently constructing megawatt spallation neutron sources, each of which will be far more powerful than any existing facility in Europe. The US Spallation Neutron Source (SNS), being built in Oak Ridge, Tennessee by the US Department of Energy, is a 1.4MW, $1.4bn (£750m) design that began construction in 1999 and will be completed in 2006 with the potential for significant future upgrades. A similar facility in Japan will be ready in 2007.

Once ISIS has been superseded scientists such as Cywinski fear many researchers may be forced to move abroad. ‘The US has the money to be able to fund something like this on its own and it is relatively easy to start as researchers only have to apply to one government and convince them of the project’s worth,’ Cywinski said.

‘The facility will have tremendous technological kudos. It will be on a par with CERN in terms of being well known. We have a few thousand scientists involved in neutron research and the US has a few hundred, yet they are the ones getting a new facility.’

In Europe neutrons have been produced mainly by nuclear reactors, but there are limits to using these for higher intensities. Within the Organisation for Economic Cooperation and Development (OECD) countries and Russia there are presently around 26 large operational neutron facilities. Most are based on reactors, but around two-thirds will come to the end of their useable lives between 2005 and 2015.

Consequently, over a decade ago an OECD forum predicted a neutron drought, with an increasing number of researchers wanting to use neutrons just as facilities producing them were being wound down. The OECD recommended building high-intensity spallation neutron sources in North America, the Asia-Pacific region and Europe.

In 1990, in a report to the European Commission, the Neutron Study Panel recommended that a design study should be initiated for a next-generation neutron source. But while the US and Japan pressed ahead it was six years before the building of the ESS was finally proposed.

The operation of the ESS is based on clean particle accelerator technology. The spallation source consists of a proton linear accelerator (Linac), which uses magnets to accelerate pulses of charged protons to almost the speed of light.

When the beam of high-energy particles exits the Linac it is either directed straight at the long pulse target station and converted into a long pulse of neutrons or sent through a set of compressor rings to form extremely short proton pulses. The compressed proton pulses are directed to a short pulse target station where they are converted into short pulses of neutron beams.

The targets consist of 1m3 of liquid mercury encased in concrete. Each target produces neutrons with different characteristics for different types of experiments. When the pulses strike the targets they chip neutrons off the mercury atoms in a process known as spallation. These neutrons are collected and channelled into a beam directed to various instruments for scientists to use to look at materials.

The long pulse target produces neutrons that are useful for looking at samples of soft matter, such as plastics or chemicals. The intense beams from the short pulse target are used to analyse harder materials such as metals, semiconductors and ceramics.

But building the ESS will not be simple. In May 2002 five sites indicated that they would be interested in hosting the e1.5bn (£1bn) facility. It was also agreed that a baseline engineering design should be ready by the end of 2003, with a decision on the project’s fate due by early 2004 at the latest.

Full plans for the ESS were designed, but while EU governments agreed that a next-generation source was urgently needed, the complexity of a decision-making process involving several states stalled project approval. Faced with this, in September 2003 the ESS Council disbanded.

However, this year the group decided to try again. A new organisation, the European Spallation Source-Initiative (ESS-I) based at Grenoble, was set up in October to work with interested governments and speak up for a next-generation neutron source in Europe.

Thanks to YESS, hopes that the ESS could be built in the UK were rekindled earlier this year after the government announced a review of options, including ESS, for the UK spending review in 2006. By mid-2005 Lord Sainsbury is expected to reach a decision on whether the UK will bid for funds. If the review gives a positive report, by then the government will consider funding for the 2006 comprehensive spending review. A final decision on whether to build the new facility is due late 2007. If all goes well, construction could begin the same year and the facility would be completed by 2014 or 2015.

However, government attempts to co-ordinate the UK bid have been criticised as being slow. ‘Lord Sainsbury has said the UK should take a lead in negotiating with the EU over the site of the ESS,’ said Cywinski. ‘However, the fate of the bid is now in the hands of the Council for the Central Laboratory of the Research Councils (CCLRC). My own feeling is that they have been a little slow off the mark. They are just setting up the review that Sainsbury promised in June last year.’

Progress elsewhere in Europe means that the UK must make a decision in mid-2005 to be on an equal footing with other countries. ‘The middle of 2005 will be particularly important,’ said Peter Tindemans, chairman of the ESS-I.

‘We should not forget the rapid progress that the US and Japan are making. It looks like SNS will be on-stream in 2006, and the Japanese source in 2007 or 2008. I believe that several people underestimate the danger this will raise for Europe’s position in neutron science, and are therefore delaying decisions.’

‘Along with Yorkshire’s YESS, there is a Scandinavian consortium of Swedish, Danish and Norwegian regional governments, laboratories and universities bidding for the ESS. The Swedes seem to be taking the bid very seriously as part of their overall scientific policy.’

In July the government appointed Allan Larsson, director-general at the EU Commission, as a special negotiator to assess the possibility of locating the ESS at Lund, on the southern tip of Sweden. The results of the assessment will be presented on 1 July 2005, when the group will decide whether it will bid for the site.

‘Sweden is investing the most of all the EU countries on research — about four per cent of our GDP,’ said Dr Patrik Carlsson, scientific project manager for ESS-Scandinavia. ‘Our government would like to keep investing in research and has also recognised the importance of investing in infrastructure. There are plans to build a new synchrotron and a free electron laser, MAX-IV, very close to ESS.’

The Hungarian government’s minister of education is looking into the benefits of Hungary hosting the ESS and will come up with a financial analysis around mid-2005. The country plans to invest substantial European structural funds and is also considering adding funding via a loan from the European Investment Bank. The country has suggested two possible sites, supported by the prestigious Hungarian Academy of Sciences.

Also interested in bidding are two German groups: Sachsen and Sachsen-Anhalt, two states in the former East Germany, which propose a site between the cities of Halle and Leipzig, and Forschungzentrum Juelich (FZJ). The FZJ bid is supported by the state of North Rhine-Westphalia in Germany, which is aiming for the ESS to be built near the Research Centre of Jüelich, close to Belgium and the Netherlands. The German government has yet to lend support to either bid, but has decided to close two of their reactors, in 2006 and 2009/2010. Though it will still be funding four national reactors plus a one-third share of ILL, this reduction may force Germany to think seriously about ensuring future access to neutron sources.

Though the UK’s ISIS facility was considering entering a bid, it has decided not to participate. However, Tindemans believes it may reconsider if Sainsbury’s report is positive.

Either way, securing such a facility in the UK would maintain the country’s world-leading position, as well as benefiting Europe’s researchers. ‘I will have retired by the time it is running, but I am fighting for the next generation to have access to better facilities than I did,’ said Cywinski.

‘It will be a wonderful legacy for the 21st century.’