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Physics and industry

The importance of physics to the UK economy has increased significantly over the past 10 years, according to a report published by the Institute of Physics last month. The report shows that the total number of companies in physics-based industries (PBI) increased by 165% between 1989 and 2000. However, investment in these companies is not keeping pace with other manufacturing sectors and there is “overwhelming evidence” of an increasing shortfall of trained physicists to meet the demands of industry, especially as about half of all new physics graduates find jobs outside the so-called traditional PBI sector. The challenges identified by the report are familiar: the low levels of investment in PBI companies; the “indiscriminate shunning” of technology companies by the investment community since 2000; the low rate of commercialization of academic physics research; the shortage of physics graduates; and the poor image of science- and engineering-based industry.

It will not be easy to solve any of these problems, although efforts to address the shortage of physics graduates are in hand following the publication last year of the increasingly influential Roberts report on the supply of scientists and engineers (Physics World June 2002 pp58-59 print version only). The problem of under-investment has also been the subject of many government reports, but little seems to change: survey after survey has confirmed that UK companies invest significantly less in R&D than their international competitors. This situation is unlikely to change without major incentives from the government.

To encourage the commercialization of academic physics research, the report calls on university physics departments to teach entrepreneurship to students and to exploit more of their research in industry. There is much to be said for equipping physics students with as wide a range of skills as possible, but with courses already overloaded and other reports calling for improved communication and team-working skills, additional non-physics modules would have to be optional. Moreover, although the Institute’s report estimates that physics-based industries account for 43% of employment in manufacturing in the UK, there is not really a physics industry in the sense that there is a chemical or a biotechnology industry. This significantly reduces the opportunities for physics departments to take part in university-industry collaborations. However, it is imperative that UK industry starts to invest seriously in the key technologies of the 21st century, be these nanotechnology or renewable energy, and that the academic physics community backs up this investment with a supply of well prepared graduates and innovative ideas.
• See industry.iop.org/pbi.html and p 44 (print version only).

Physics around the world

This issue contains four articles about science in parts of the globe that Physics World does not often cover, starting with a report (p11, print version only) on a recent meeting that explored why the Islamic world seems to be turning its back on science. On page 15 (print version only) Katepalli Sreenivasan of the Abdus Salam International Centre for Theoretical Physics (ICTP) describes how the level of scientific literacy has fallen in many countries since the centre was founded almost 40 years ago. Habatwa Mweene was at the sharp end of that illiteracy recently. As a semi-official spokesman on the 2001 solar eclipse, Mweene had to convince a sceptical – and largely fundamentalist Christian – public in Zambia that the eclipse did not signal the end of the world (p56, print version only). But there are ways that scientists from developed nations can help. They can support the ICTP and – as Paul Prentice describes on page 47 (print version only) – go and teach in the developing world. His experience in Ethiopia was certainly hard but shows what can be achieved.

Novel crystals form under pressure

The physical properties of materials depend strongly on structure and interatomic distance. High pressure can vary these distances considerably and enables the relationship between structure and properties to be examined. Moreover, pressure can bring about large changes in the arrangement of atoms in a material without altering its chemical composition. Previous high-pressure work at Edinburgh by McMahon and colleagues revealed complex new structures in various elements, such as rubidium, barium, strontium and bismuth, including the first ever composite structures in an element. One structure that they observed in barium was described by a researcher as the “weirdest atomic structure of a metal or of any pure element” (V Heine 2000 Nature 403 836). These results were obtained by studying single crystals of the elements under high pressure using X-ray diffraction.

Now, McMahon and co-workers have studied tellurium and selenium – elements known to exhibit complex behaviour at high pressure, such as dramatic changes in the superconductivity transition temperature on compression. To create the huge pressures needed in their experiments (up to 36 GPa) the researchers squeezed small amounts of the powdered element between two diamonds. They then studied the sample, while it was under pressure, using X-ray beams from the Synchrotron Radiation Source at Daresbury.

“The structures in tellurium and selenium are an entirely new elemental structure type – a very simple crystal arrangement with large out-of-phase modulations,” McMahon told PhysicsWeb. “What happens is that the atoms are displaced from their positions in the basic structure by a certain amount.” It is not yet clear, however, why these elements adopt such structures under high pressures. The link between this complex organization and the change in superconductivity transition temperature remains another mystery.

The team now intend to measure other physical properties at high pressure. “We can then use pressure to ‘tune’ the properties of materials to improve their characteristics,” said McMahon, who hopes that these properties could be produced at atmospheric pressures. The results will be published in Physical Review Letters shortly.

Gold floats in magnetized oxygen

Magnetic levitation occurs when the force on a diamagnetic object is strong enough to balance the weight of the object itself. If the object is immersed in a paramagnetic fluid, such as gaseous oxygen, the levitation can be enhanced by the effect of buoyancy caused by the “magneto-Archimedes” effect. The levitation force per unit volume of the object depends on the vertical magnetic field gradient in the vessel.

The fact that the density of a gas at fixed pressure is inversely proportional to temperature (Charles’ law), as is the paramagnetic susceptibility (Curie’s law) means that near the boiling point of liquid oxygen, 90 K, the magnetic buoyancy of oxygen gas is ten times stronger than at room temperature.

Liquid oxygen can provide even greater buoyancy – enough to float dense diamagnetic objects at relatively low magnetic field strengths (figure 1). Each object floats at the point at which the local magneto-Archimedes force balances its weight, and the position of the object can be adjusted by changing the magnetic field strength.

Figure 2

The researchers also noticed the formation of a regular pattern of peaks on the surface of the liquid oxygen (figure 2). The peaks are a result of magnetic and surface energy effects and have only ever been observed in synthetic ferrofluids before.

Breaking charge symmetry with nuclei

According to charge symmetry protons and neutrons should have the same properties. This symmetry is obviously broken because the proton has a positive electric charge while the neutron is neutral. Moreover, the neutron is slightly heavier than the proton and decays into a proton, an electron and a neutrino after about ten minutes. However, protons and neutrons behave the same in many other nuclear reactions.

Stephenson and co-workers used the cyclotron facility at Indiana to direct a beam of deuterons – nuclei that contain one proton and one neutron – through a target of deuterium gas. All of the helium nuclei made in this process were collected and detected. The short-lived pions produced in the reaction decay into pairs of photons, which were also detected. The team collected enough events to be able to calculate the rate at which the fusion reaction occurs.

Theoretical physicists believe that charge symmetry breaking originates with quarks – the particles that make up protons and neutrons. A proton contains two “up” quarks and one “down” quark, while a neutron contains one up and two down quarks. Part of the violation is thought to result from the fact that up and down quarks have different charges – +2/3 and -1/3 respectively – and part is thought to be due to their different masses.

“The solution to this riddle is part of the story of the formation of the universe after the big bang,” Stephenson told PhysicsWeb. “As the universe cooled, a point was reached where neutrons and protons could exist separately. As a result of charge symmetry breaking, more protons than neutrons were formed and thus, the early universe contained hydrogen – which later fuelled the stars. If the proton had been heavier, then neutrons would have been the most abundant particle and hydrogen would not have survived.”

The Indiana team plan to submit its results to Physical Review Letters shortly.

Z-fusion makes progress

Fusion is the process that powers stars and, if harnessed in the laboratory, could provide a clean and almost limitless source of energy. However, fusion reactions are difficult to achieve because they require extremely high temperature plasmas, which must be confined long enough to be able to extract an appreciable amount of energy.

In the past, plasma has been confined by strong magnetic fields in “tokamaks” or by laser beams in inertial confinement experiments. The Sandia team used a “ Z-pinch” in which electrical current rapidly heats an array of tungsten wires into the plasma state and causes them to explode. These expanding wires then merge into a cylinder and produce higher intensity X-rays, which strike the surface of a target capsule containing deuterium. The X-ray energy produces a shock wave that heats and compresses the deuterium, leading to fusion.

The team estimates that about 10 billion neutrons are produced, which corresponds to an energy output of about 4 mJ. It now hopes that a larger Z-machine could increase this fusion yield in the future.

New neutrons for European scientists

ISIS generates neutrons by firing high-energy protons at a tungsten target in a process known as spallation. Its existing target station directs short-wavelength neutrons to 20 scientific instruments that support around 1500 researchers working across condensed-matter physics, materials science, chemistry and biology.

The second target station, to be housed in a new building, will generate longer-wavelength neutrons to allow research in soft condensed matter, advanced materials and biomolecules. Andrew Taylor, director of ISIS, says that about six new instruments should be up and running when the new target comes on line at the end of 2007, with another 12 instruments starting up over the following five years. The £100m will cover the cost of the core target station and the first set of instruments. Negotiations are underway to obtain funding for the remaining instruments from other countries.

ISIS and a reactor at the Institut Laue-Langevin in Grenoble, France, are currently the world’s two most advanced high-flux neutron sources. They will be superseded by larger facilities being constructed by the US and Japan that are due to start up in 2006 and 2007 respectively. But Taylor says that the upgrade to ISIS will ensure that the UK machine retains its pre-eminence until at least 2008.

Approval for the second target station follows the start of construction last month of the £235m Diamond synchrotron source at Rutherford, and the announcement by the government last week that the Daresbury Laboratory in Cheshire is to receive £11.5m for research into a new 4th generation light source.

Can diamond now be a superconductor?

Diamond is a semiconductor and Prins has long been interested in using n-type diamond as a “cold” cathode to replace the “hot” cathodes found in television tubes and many other devices. Moreover, he believes that the results of his experiments on n-type diamond surfaces – made by exposing the diamond to energetic oxygen ions – can only be explained by a new type of superconducting state. “If it is not superconductivity then it must be violating the second law of thermodynamics,” he says.

In his experiments, Prins measures the current that flows between the diamond and a gold-plated probe as the distance between them is varied. When a voltage of +1000 V is applied, the current always settles down at a value of about 0.5 mA for separations up to about 16 µm, after which it falls to zero. A current also flows in the opposite direction when a voltage of –1000 V is applied, but it decreases more rapidly with distance. The experiments are performed at room temperature in a vacuum of 10^–6 mbar.

Prins argues that a thin “electron-charge” layer is formed in the vacuum just above the surface of the diamond, and that a depletion layer of positive charges forms in the diamond. This is similar, he says, to the Schottky diode that is generated between an n-type semiconductor and a metal. Prins then applies the equations that describe electron transport through a Schottky diode to his system. He finds that as more and more electrons are extracted from the diamond, the density of electrons in this layer reaches a critical value at which a Bose–Einstein-type condensate of electron pairs forms. Current continues to flow from the diamond cathode through this layer to the anode, even though there is no voltage across the layer – a sign of superconductivity.

However, the rest of the diamond community remains to be convinced. Richard Jackman of University College London, who edited the special issue of the journal in which Prins’ papers appear, describes them as “largely theoretical papers, thought provoking and very controversial – the end conclusions remain open to debate”.

Prins admits that he must show that the state can expel magnetic fields to conclusively prove that the state is superconducting. However, he has recently retired and does not have the facilities to perform such an experiment. He has offered to fly his samples to another lab but has not yet found any volunteers. Prins and two colleagues are also trying to secure patents on the ideas.

In addition, Prins is half-way through writing six theoretical papers that will, he claims, fully explain the results and shed new light on the mechanisms underlying high-temperature superconductivity.

Energy R&D needs more investment

The government recently published a white paper on energy, citing economics and waste as reasons for turning its back on nuclear power. It said that by 2020 a fifth of the country’s electricity should be generated from renewable energy sources, such as wind, wave and solar power. It pledged an extra £60m for such technologies, increasing its total spending on renewable energy to about £350m over four years.

However, the Science and Technology Committee believes that these funds lack focus and are insufficient, both in absolute terms and in comparison with the UK’s competitors. “There is a superabundance of funding bodies, resulting in fragmentation of effort and confusion in academia and industry,” its report says. “Where UK technologies are developed, we found the private sector unwilling to develop these technologies while the government is failing to step in to take them forward or provide the necessary incentives to encourage private companies.”

The committee recommends the formation of a “Renewable Energy Authority” to identify and develop those technologies that are best suited to Britain’s natural resources and skills. “We believe that the focus should be on offshore technologies – wind, wave and tidal – and nuclear fission and fusion,” it says.

The committee also criticizes the government’s economic incentives for the take up of renewable technologies, and proposes setting up a taxation system to reward “carbon-free” or “carbon-neutral” sources. “We believe that nuclear fission should enjoy the full status of a carbon-free technology,” it says. “Renewable sources of power are not coming on stream fast enough and nuclear power must fill the gap.”

Solar surgery makes progress

Laser light is used in certain medical procedures such as the removal of cancerous tissue. The growths, which are normally between a few mm to a few centimetres in diameter, are killed by high and localized rapid heating. The laser light is coupled into an optical fibre that is threaded through a catheter to the tissue being treated. However, this method can be expensive which has limited it to being used more widely.

Last September, the Israeli team led by Jeffrey Gordon, reported that it had built compact solar fibre-optic “concentrators” that provide the same power levels and densities as laser optic fibres. The concentrator consists of a parabolic mirror 200mm in diameter and with a focal length of 120 mm. It concentrates solar radiation into an optical fibre 1mm in diameter and up to 20m long (see figure). The researchers were able to produce several watts of concentrated sunlight at flux levels 10000 times that of a normal solar beam.

Visible and near-infra red wavelengths have certain advantages over infrared or ultraviolet radiation; commercial optical fibres with high light transmissivity are easily available; and the optical penetration depth is much greater. Moreover, the absorption spectrum of biological tissue is well suited to the spectrum of solar radiation.

Now, the scientists have managed to use their technique to carry out surgery on chicken livers. In one experiment, the end of the fibre was placed in a protective glass sleeve that was inserted directly into the organ. In another “non-contact” experiment the livers were sandwiched between two glass slides and the fibre tip placed against the upper slide.

The researchers focused the solar beam on the sample surface for up to 360 seconds and then measured how much the tissue had coagulated, which shows that cells in the tissue have been killed. The beam varied in power from 2W to about 6.5W and lesions of approximately 1000 mm³ were observed penetrating deep inside the tissue – roughly the same size as the lesions treated in tumour surgery.

The team has now embarked upon clinical trials on live animals. “Our first successful solar surgery on live animals was performed in January 2003,” Gordon told PhysicsWeb. “We are continuing with these trials. Thus far, our lab work is restricted to livers because our surgical partner is a liver surgeon but in principle, solar surgery could be developed for a far broader range of applications.”

Double funding boost for Daresbury

“In the medium-term, we intend to see Daresbury developed as a mixed-use science campus,” said Mike Shields, chief executive of the agency. “It will provide fundamental research and development funded by the Government and the private sector, and research by local universities. We are now well on the way to achieving this.”

The money for 4GLS will cover research, development and design over three years. 4GLS will use an energy recovery linac and a free electron laser to generate light over a range of wavelengths from the infrared to the extreme ultraviolet.

“Twenty years ago, Daresbury demonstrated that it could lead the world with the building of the world’s first ‘second generation’ source,” said Elaine Seddon, the 4GLS project manager. “Now we have shown that we can lead the world again with 4th generation technology.”

4GLS was originally part of the CASIM proposal at Daresbury, which also included a proton accelerator called SIRIUS that could be used both for nuclear physics and medical research. Although the nuclear physics programme planned for SIRIUS was rated highly in a government review of the proposal, the use of accelerated protons and ions for cancer therapy was not viewed as a high priority in a recent review by the National Cancer Research Institute.

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