Research at RAL
As well as funding scientific research at universities and contributing to international collaborations like CERN, the STFC (Science & Technology Facilities Council) supports and runs a number of science laboratories in the UK, including the Edinburgh Observatory, the Daresbury Laboratory and the Rutherford Appleton Laboratory (RAL). The purpose of this article is to describe the particle accelerators and lasers based at the RAL. There is insufficient space to describe more than a couple of case studies of recent research so readers are encouraged to follow the links for further information, including educational resources and opportunities for visits. Every year thousands of scientists from more than 30 countries flock to RAL in the Oxfordshire countryside to undertake groundbreaking research in the life sciences, chemistry, physics, environmental science – even archaeology – though some of the most fruitful work blurs the boundaries between the disciplines.
Diamond Light Source
Figure 1: Aerial view of the Diamond Light Source
Figure 2: A schematic of the Diamond Light Source
When shown an aerial picture of the RAL site (figure 1), people’s eyes are drawn to the doughnut-shaped building, which houses the Diamond Light Source. Diamond opened in 2007 and can produce beams of light 10 billion times brighter than the Sun. It accelerates electrons in order to create synchrotron radiation. Once electrons are created in an electron gun, electric fields accelerate them in straight lines, while magnetic fields change their direction so that they follow a quasi-circular path, actually a series of chords (or straight lines) inscribed inside a circle. It is called a synchrotron because the strength of the bending magnets has to be increased in synchronicity with the increasing speed of the electrons, to keep them on the same 562 m circular trajectory. But when they change direction, the electrons lose energy as synchrotron radiation: beams of very bright highly focused light of different wavelengths, which emerges along a tangent to the ring (figure 2), where a target is waiting and scientists can analyse and interpret the interactions.
The fight against cancers and other illnesses will benefit from the new research techniques available at Diamond. Electronic engineers can image structures down to an atomic scale, helping them to understand the way impurities and defects behave and how they can be controlled. Plants and microorganisms have a natural ability to absorb toxic metals from contaminated land and then deactivate them. For example, Diamond is helping a group of researchers at Reading University, led by Professor Mark Hodson, to explore how earthworms cope with and process toxic levels of metal pollutants in soils in the expectation that this will lead to cheap and effective ways of cleaning up polluted land.
ISIS pulsed neutron and muon source
Figure 3: Instrument map of ISIS
The ISIS pulsed neutron and muon source (figure 3) is more difficult to spot amongst the buildings at RAL. It is also a synchrotron but, in this case, protons are accelerated in order to create muons and neutrons. Passing through a thin graphite target, two to three per cent of the proton beam produces muons (heavy electrons) for use in muon spin spectrometry. The remaining protons strike a tantalum-clad tungsten spallation target, where each proton can eject about 20 neutrons. Because neutrons are uncharged they can penetrate deep into matter without experiencing electrostatic repulsion and so provide different information, which cannot be revealed using Diamond. The 163 metre circumference of ISIS has 10 sections, each consisting of an electric field to accelerate bunches of protons and magnetic fields to steer and collimate the pulsed beam. Given that previous accelerators were cannibalised for her construction it seems apt that ISIS was named after Isis, the Ancient Egyptian goddess who could resurrect the dead and was also the matron of nature and magic. Opened in 1985, pioneering work at ISIS includes discovering the structure of high-temperature superconductors and the solid phase of the Buckminster fullerene.
Case Study: Cella Energy
Cella Energy is the first spin-out company from the ISIS neutron source. Along with colleagues from the University of Oxford and the London Centre for Nanotechnology at University College London, the ISIS team has already won prestigious awards for an innovation that may significantly reduce our carbon footprint and increase our energy security. This includes the 2011 Shell Springboard Award “for an invention which brings zero-emission hydrogen cars a step closer”.
Transport is estimated to contribute about 25 per cent of global anthropogenic carbon emissions. “In some senses hydrogen is the perfect fuel; it has three times more energy than petrol per unit of weight, and when it burns it produces nothing but water,” said Professor Stephen Bennington, Chief Scientific Officer at Cella Energy and the leader of the team behind the innovation that allows ordinary internal combustion engines to burn hydrogen.
The ultimate goal is electric vehicles driven by hydrogen fuel cells but these are yet to become commercially viable. The innovation from Cella Energy could bridge the gap, by providing the means for people to fill up their cars with hydrogen on the forecourt just as they do with petrol, side-stepping the need to pressurise or liquefy the gas. Hydrogen fuel is normally stored and handled as a liquid, which requires a pressure of 700 bar or a temperature of minus 253 °C. Inherently risky, both these ‘solutions’ require considerable energy, as well as expensive infrastructure, including pumping equipment.
Cella has manufactured hydride ammonia borane NH3BH3 (figure 4) as micro-fibres, thirty times thinner than a human hair. The result looks like tissue paper (as shown in figure 5). But the material could also be manufactured as micro-beads, which could be poured or pumped like a liquid and is the key behind overcoming the ‘3 minute, 300 mile rule’, where motorists expect a three minute refuel to last three hundred miles.
Figure 4: schematic of ammonia borane
Figure 5: Microfibres of ammonia borane
Case Study: ‘Cling-film’ solar cells
Scientists from the Universities of Sheffield and Cambridge used the ISIS neutron source and the Diamond Light Source to carry out research into plastic (polymer) solar cells.
“Over the next fifty years society is going to need to supply the growing energy demands of the world’s population without using fossil fuels, and the only renewable energy source that can do this is the Sun”, said Professor Richard Jones of the University of Sheffield. “ In a couple of hours enough energy from sunlight falls on the Earth to satisfy the energy needs of the Earth for a whole year, but we need to be able to harness this on a much bigger scale than we can do now. Cheap and efficient polymer solar cells that can cover huge areas could help move us into a new age of renewable energy.”
Photovoltaics are semiconductor devices that convert solar energy into electrical energy. Hitherto manufactured from silicon, they can also be made from plastic, so-called organic photovoltaic devices. Plastic films only sixty nanometres thick, over a thousand times thinner than a human hair, can be deposited from solution by low-cost roll-to-roll printing techniques similar to the way newspapers are printed and taken off a roll at the end.
Dr. Robert Dalgliesh (figure 6), one of the ISIS scientists involved says, “This work clearly illustrates the importance of the combined use of neutron and X-ray scattering sources such as ISIS and Diamond in solving modern challenges for society”. He added, “we were able to probe the internal structure and properties of the solar cell materials non-destructively” in order to improve the efficiency and performance of the solar cells.
Figure 6: Dr. Robert Dalgliesh at ISIS
Central Laser Facility
As well as developing and maintaining world-leading laser equipment for use by research teams throughout the UK, scientists at the Central Laser Facility (CLF) are pioneering and implementing the latest techniques in order to enhance and squeeze the most out of the technology. There are a number of lasers offering a vast range of output power, wavelength and pulse frequency to satisfy a plethora of research objectives. For example, high power lasers can initiate nuclear fusion while ultra-short pulsed lasers can track transient changes in atoms and molecules. The combination of design flexibility and expert operation means that CLF lasers are much more productive than they would be if each was limited to one specific role at a particular institution.
Figure 7: a scene from the film Goldfinger, starring the laser
(Image: Eon Entertainment)
A solution looking for a problem
When lasers were invented in 1960, they were called “a solution looking for a problem”. The tabloids ran stories about ‘death rays’, which might have inspired the scene in Goldfinger, the 1964 James Bond film, where the hero is strapped, spread-eagled, to a metal table while a laser cuts it in half. See figure 7 They are now ubiquitous, with compact disk players and eye surgery vying as the most familiar applications. They have generated billions of pounds Sterling worth of business and at least 10 Nobel laureates can thank lasers for the breakthroughs they achieved.
The most powerful lasers can be used to recreate the extremely high temperatures and pressures found in stars. Vulcan is a very high-energy laser with a footprint bigger than six tennis courts (see figure 8), which makes major contributions to Inertial Confinement Fusion (ICF), critical to the development of fusion energy. But lasers are rarely just pointed at something. The light is usually manipulated in some way. For example, lasers have been used to cool matter to the lowest temperature recorded in the known universe (achieving a universal record, not a mere world record) and they can be used as ‘optical tweezers’ to pick up and manipulate objects as small as micro-organisms. These ‘tweezers’ can also be used to measure the force required to unzip the DNA double helix or the force a virus needs to exert in order to invade a cell.
Figure 8: Vulcan
Case Study: What lies beneath?
Spectroscopy can reveal chemical composition. Shine light at it and the composition of a transparent substance or a dissolved sample can be revealed by the absorption spectra. Likewise, the reflected light from an opaque substance can betray its chemical composition. But what if you wanted to know what lies beneath the surface of a milky liquid or even a solid? A technique called spatially offset Raman spectroscopy (SORS) is being developed that will do just that. Close collaboration with STFC Innovations Ltd. is commercialising this technique through the spin-out company Cobalt Light Systems. (See figure 9.)
Figure 9: SORS in operation
Experiments have shown that SORS can detect hydrogen peroxide, a potential explosive, even when concealed in a typical plastic cosmetics bottle. If SORS could be deployed at airport check-in perhaps the ban on carrying liquids in hand luggage onto aeroplanes might be lifted. In collaboration with University College London, research is ongoing to establish whether SORS could be used to detect bone disease through soft tissue, while research with Gloucestershire Royal Hospital will establish whether breast cancer can be diagnosed by looking for signs of calcification in breast tissue.
Diamond Light Source
www.diamond.ac.uk/Home/Teachers.html includes links to downloadable simulations and linked problems, aimed at the A-level physics curriculum, and the opportunity for students to become involved in a Particle Physics Masterclass.
ISIS pulsed neutron and muon source
www.isis.stfc.ac.uk/learning/learning2114.html includes the excellent Backstage Science videos, with scientists describing what they do.
www.cellaenergy.com describes what they do in more detail, as does the relevant academic paper, Z. Kurban et al., J. Phys. Chem. C, 2010, 114 (49), p21201.
‘Cling film’ solar energy
P.A. Staniec et al., Advanced Energy Materials, 1(4), p499.
Central Laser Facility
www.clf.rl.ac.uk includes more information. There is an podcast by The Naked Scientists about Artemis - the Superfast XUV Laser, which can be heard at www.thenakedscientists.com/HTML/content/interviews/interview/1958/
Cobalt Light Systems