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UK confirms withdrawal from ILC

Physicists in the UK have failed to persuade research council bosses to rejoin preparations for the International Linear Collider (ILC). The decision to pull the UK out of the project had been announced in December by the Science and Technology Facilities Council (STFC) after it was awarded an average annual funding increase of just 4.5% over the next three years, which left it with £80m less to spend than planned.

But despite strong protests from physicists, the STFC says in a statement released today that it has “reaffirmed its decision to stop funding the ILC”, which is seen as the next big experiment in particle physics after the Large Hadron Collider at CERN. The statement was released following a meeting of the STFC’s council last week.

I can never accept the legitimacy of the deeply flawed process that has led to the STFC’s withdrawal from the ILC Brian Foster, Oxford University

The STFC has also confirmed that it will stop funding for solar-terrestrial physics and that it will cut its investment in the two 8 m Gemini telescopes in Hawaii and Chile, which will prevent UK astronomers from using either facility despite the country having been a founding member of the project and having invested more than £35m in the telescopes.

Delivery plan

The decision to withdraw from the ILC was first revealed in a “delivery plan” that the STFC published in December, which outlined its scientific priorities over the next three years in the light of the £80m funding shortfall. Bosses at the STFC will spend the next three weeks considering that document, before making a final decision on 27 February of what to fund, although the decisions concerning the ILC, Gemini and solar-terrestrial physics will not be reversed. The STFC will then begin “a period of consultation with the community concerning the implementation of the plan”.

Brian Foster from Oxford University in the UK, who is European director of the ILC’s global design effort, says he regrets — but is not surprised by — the STFC council’s decision to withdraw from the ILC.

“At no time has council or any of its subsidiary bodies, or the chief executive, seen fit to discuss this ill-informed decision with me or our international partners, but has instead presented it as a fait accompli,” Foster told physicsworld.com. “While I am grateful that various STFC officials are working constructively with me to try to rescue some of the world-leading work in the UK, I can never accept the legitimacy of the deeply flawed process that has led to the STFC’s withdrawal from the ILC. I will continue to make the case for this vital world project in the hope that STFC will rejoin in the future.”

Michael Rowan-Robinson, president of the Royal Astronomical Society, told physicsworld.com that he is pleased that the STFC is seeking input from the scientific community in implementing its plans. “However, I am still not happy either with the funding allocation or the way it has been managed by the STFC,” he says.

Not as bad as it seems

In its statement, the STFC tries to show that the overall funding situation is not as bad as it might appear. It points out that it does not envisage any compulsory redundancies taking place before the summer, apart from the 180 staff who will lose their jobs over the next two years as a result of the scheduled closure of the Synchrotron Radiation Source at the Daresbury Laboratory in Cheshire.

The STFC also claims that particle-physics grants will be worth £7.1m more in 2008/9 than in 2005/6 — a rise of 43% — and that grants for astronomy will rise by 67% over the same period as a result of the research councils having to pay the “full economic cost” of research projects. In the past, grants included only about half of the “indirect” costs of a project, which go towards buying equipment and paying the salaries of permanent staff.

But Mark Lancaster, a particle physicist at University College London, is not impressed with the STFC’s statement. “There is nothing really new here, apart from a moratorium on compulsory redundancies,” he says. “The STFC has spun it the best it can but the numbers speak for themselves: there will be 25% fewer astronomy post-docs in 2011 than in 2008. Project grants will still be cancelled and existing rolling grants will be cut.”

Columbus module heads to the space station

Europe’s Columbus laboratory has been successfully launched into space towards its eventual home on the International Space Station (ISS). The 10-tonne Columbus module took off on board the space shuttle Atlantis as it lifted off from the Kennedy Space Center in Cape Canaveral, Florida, at about 14:50 EST (19:50 GMT) today. American and European astronauts will spend the next 11 days connecting the module to the space station, in what will be the single largest contribution by the European Space Agency (ESA) to this international effort.

Columbus is a 4.5 m-wide cylindrical space capsule that has room for 14 separate science experiments. The lab will primarily study how reduced gravity affects a range of medical and physical phenomena.

“I think it is very important for Europe to have a permanent laboratory up there,” says Martin Zell, ESA’s head of research operations in human spaceflight, microgravity and exploration.

The €700m laboratory is a user facility containing 10 telephone-booth-sized racks that can accommodate a wide range of experiments over Columbus’s proposed 10-year lifetime. “A satellite mission is fixed from the beginning, whereas in Columbus the facilities host experiments that can change,” says Zell. Five of the racks have been pre-installed in Columbus before launch with experiments to study fluid science, biology and physiology.

The shuttle Atlantis also contains two separate payloads — a suite of solar observation equipment and a material testing platform — that astronauts will hook up to two of Columbus’ four external mountings that are exposed to outer space. “Columbus is more than a science laboratory; it is a technology test bed that will give Europe experience in living in space,” Zell says.

I think it is very important for Europe to have a permanent laboratory up there Martin Zell, ESA

Physics experiments

Several physics experiments will take place in the Fluid Science Laboratory (FSL), which includes various interferometers and high-speed cameras for studying user-provided liquids, emulsions and aqueous foams in the station’s microgravity. The first FSL experiment is Geoflow, which will model the dynamic flow in the Earth’s liquid mantle by trapping silicon oil between two concentric spherical shells. Simulating the mantle is extremely difficult on the Earth’s surface because gravity overwhelms the other forces that are of interest. “Columbus provides us the opportunity to study the influences of temperature and rotation on convective flow when gravity is no longer there,” says Geoflow team member Birgit Futterer of Brandenburg Technical University in Cottbus, Germany.

The launch, originally planned for early December last year, was twice called off due to a glitch in a now-repaired fuel gauge sensor. This final hold-up capped a 16-year delay, as the Columbus lab was due to lift-off in 1992 to commemorate the 500th anniversary of its namesake’s voyage to America. However, it was not until 1995 that ESA decided on the lab’s full development and not until 2002 that much of the construction was completed in Italy and Germany. The Columbia shuttle disaster in 2003, in which seven astronauts died, put all plans on hold.

Geoflow had been scheduled to start just as soon as Columbus was secured to the station but with the two-month delay mission planners have moved ahead some biology experiments that are more time-sensitive. After such a long wait, both European and American scientists are anxious for Columbus to get going. “It is a huge enhancement in the research capabilities of the space station,” says Zell.

Cooled material stretches beyond belief

Most materials contract when they are cooled and get bigger when they are warmed up. But some substances do the opposite by shrinking in certain directions as they are heated and expanding when cooled. Now researchers in the UK have found an inorganic crystalline material composed of silver, cobalt, carbon and nitrogen that expands more than any other known material when cooled.

Negative thermal expansion occurs when, during heating, a crystal contracts along one or more crystal axes, while positive thermal expansion describes what happens when the material expands along one or more of these axes. Using X-ray diffraction Andrew Goodwin, a physicist at the University of Cambridge and colleagues at the Rutherford Appleton Laboratory and Durham University, found that silver(I)hexacyanocobaltate(III), or Ag3Co(CN)6, has a coefficient of thermal expansion of around –120 × 10–6 K–1 in one direction, some 14 times larger than the previous best material, ZrW2O8 (Science 319 794).

Colossal expansion

Moreover, the material expands so much along the other axes when heated that its coefficient of thermal expansion in this direction is 140 × 10–6 K–1, some 10 times bigger than any other material. The researchers use the term ‘colossal’ to describe a material that has an axis with a thermal expansion more than 100 × 10–6 K–1, meaning that Ag3CoC6 is the first material with both colossal positive and negative thermal expansion.

You can imagine the silver framework like a collapsible garden fence Andrew Goodwin, University of Cambridge

The material displays this unusual behaviour because of its sandwich-like structure in which Co(CN)6 octahedra sit between layers of silver atoms in the middle. As the bonds between the silver atoms are relatively weak, the silver layers can flex easily. “You can imagine the silver framework like a collapsible garden fence” says Goodwin. As the material is cooled this flexing of the silver layer allows it to contract which then pushes the octahedra of the remaining surrounding ions out and causes the material to stretch when cooled.

The researchers think that the material could be used to stabilize mirrors and other optical devices in satellites which can be very sensitive to changes in dimension. Such devices change position because the satellites heat up and cool down so much as they orbit the earth. Goodwin and colleagues believe that applying a thin coat of the material to the mirror could counteract this change of dimension and avoid the need for it to be mechanically adjusted.

Putting the squeeze on quantum noise

Physicists in Germany have produced a beam of “squeezed” laser light with a record low level of quantum noise. Their technique reduced the noise in an infrared beam by 90% and could someday be used to allow gravitational wave detectors to probe deeper into space and to create quantum information and cryptography systems.

The electric field of a light beam always carries some inherent quantum noise — the result of fluctuations in amplitude and phase caused by the intrinsic quantum nature of the photons. Now Roman Schnabel and colleagues at the Max Planck Institute for Gravitational Physics and Leibniz University in Hanover have found a way to remove much of this noise from a 1064-nm laser beam using a double-refraction crystal and green laser light (Phys Rev Lett 100 033602).

Storing photons

“The green laser prepares the crystal by causing the electron cloud of the crystal’s atoms to oscillate with the frequency of the green light,” explained Schnabel. “In this state, the crystal can then store photons sent in by the infrared beam.” When the photon flux is then reduced these stored photons are replaced back into the beam, which in turn achieves a more regular photon distribution.

As a result, phase fluctuations are almost eliminated from the beam. “We achieved a quantum noise reduction level of 90%,” said Schnabel, adding, “Until now a good result was a reduction by a factor of four, down to 25%”.

The researchers believe that the squeezing strength in their set-up is limited by optical losses rather than phase fluctuations, and so could be improved further.

Using squeezed light we can extend the reach of gravitational wave detectors by a factor of three Roman Schnabel, Max Planck Institute for Gravitational Physics and Leibniz University

Quantum noise can perturb sensitive measurements, such as those made by the Laser Interfermometer Gravitational Wave Observatory (LIGO) facilities in the US. All current LIGO detectors use infrared lasers to search for the tiny interference patterns that are predicted to appear when gravitational waves interact with the beams, but the extreme weakness of the waves makes them almost impossible to detect.

According to Schnabel, the uniform intensity of squeezed light could make these detectors more sensitive and allow it to probe deeper into space where the elusive waves are created. “Using squeezed light we can extend the reach of gravitational wave detectors by a factor of three,” he said.

Another application could be quantum information and cryptography. “Squeezed states have been used to demonstrate several quantum information protocols, construct entangled states of light and demonstrate quantum teleportation,” said Schnabel.

Dynamic holograms grow up

Physicists in the US have created the largest holographic display that can show different 3D images. The display is also the first to be based on a material known as a photorefractive polymer, which opens the door to even bigger dynamic displays.

The principle of making a hologram is straightforward. First, a single laser beam is split into an “object beam” and a “reference” beam. The object beam is directed to an object to be rendered, which scatters the light towards a plate. At the plate, this light mixes with that of the reference beam, producing an interference pattern that contains all the 3D information — that is, phase and amplitude — about the object. The interference pattern then just has to be stored in a suitable material, usually as a spatially varying absorption, thickness or refractive index.

For static holograms, there are many storage materials — indeed, commercially available static holograms can be bought in full colour and high resolution up to almost any size. The problem arises, however, if one wants a material that can display images that change over time. Physicists have managed this to some extent using, for example, “acousto-optic crystals”. But because the effect in these materials is fickle, the displays must be updated around 30 times a second, which is good for 3D video but can only be used to make tiny displays.

TV resolution

10 cm screen
10 cm screen

Nasser Peyghambarian and colleagues from the University of Arizona, in collaboration with Nitto Denko Technical Corporation in California, have now created an updatable holographic display that is 10 cm square with roughly the same resolution as a standard television (Nature 451 694). “The updateable holographic display represents the middle ground between low-resolution, small dynamic displays and high-resolution, large, static displays,” Nasser told physicsworld.com.

The display is made of a photorefractive polymer, in which mobile charge carriers accumulate in the light and dark patches of the interference pattern, creating a spatially-varying electric field. This field forces the polymer’s refractive index into a profile matching the interference pattern, which can remain stored for around three hours, or until the charge carriers are dispersed with a uniform “eraser” beam.

The team are now trying to increase the size of the displays and reduce the writing time for showing video. Peyghambarian says they have “encouraging” results in full-colour versions. Progress in this area will be attractive for applications in medicine, where surgeons could see complex operations progress in real-time 3D; or for the military, to give an instant view of the location of enemy fighters.

Dark matter may not be so dark

Direct evidence for dark matter, the other worldy substance thought to make up 23% of the universe, could be staring cosmologists in the face. That’s the conclusion of theoretical physicist Susan Gardner at the University of Kentucky in the US, who argues that if dark-matter particles had a tiny magnetic moment they would imprint a distinct polarization pattern in the radiation left over from the early universe.

For some researchers, this is a big if. The most widely studied dark-matter candidates, which arise naturally in supersymmetric extensions to the standard model of particle physics, do not have magnetic moments. But with few observational constraints, the difference between one dark-matter candidate and another is often a matter of theoretical preference.

Why should dark matter, which is much more abundant, be homogeneous in composition? Susan Gardner, University of Kentucky

“Recently there has been a proliferation of novel candidates for dark matter,” says Jonathan Feng at the University of California at Irvine, who has come up with a few himself. “This one has a property that most others do not, but science is not a democracy — the most popular candidate doesn’t necessarily win!”

Particles of the moment

Proposed in 1933 to explain why some galaxies rotate faster than would be possible if only visible matter was locally present, dark matter has gained plenty of indirect support in the last few decades. But apart from knowing that dark-matter particles interact gravitationally and must be electrically neutral (otherwise they would couple strongly to electromagetic radiation and would have been spotted), researchers do not know what dark matter actually is.

In fact, Gardner questions whether dark matter is made up of just one type of particle at all, as supersymmetric solutions suggest. “The world we know is made up of lots of different kinds of particles, many with magnetic moments,” she says. “Why should dark matter, which is much more abundant, be homogeneous in composition?”

Provided the early universe contained a magnetic field, Gardner’s dark-matter particles would line up like tiny bar magnets and produce a net magnetization (Phys Rev Lett 100 041303 ). This would have a distinct effect on the polarization of photons in the cosmic microwave background (CMB), which was born 380,000 years after the big bang when the universe cooled enough for atoms to form. Dark matter is already vital when trying to explain the size of small fluctuations observed in the temperature of the CMB, since these come from density perturbations in the primordial plasma. Were photons to interact with magnetic dark-matter particles, however, their polarization vectors would be rotated via the Faraday effect.

Detecting such a polarization signature would not only rule out supersymmetric dark-matter candidates, but also show that dark matter is slightly less “dark” than originally thought.

Polarization modes

The problem is that there are many sources of polarization in the CMB photons. The most prominent comes from scattering by electrons that “see” non-uniform radiation due to surrounding density fluctuations. These are classed as “E-mode” polarization patterns, and recently have been measured in detail using the Wilkinson Microwave Anisotropy Probe (WMAP) and other ground-based experiments. So far undetected are the much weaker “B-mode” patterns, which can arise due to gravitational waves that cause space to expand and contract.

We are paying closer attention to our EB spectrum than ever because of these possible probes of new physics Gary Hinshaw, NASA Goddard Flight Center

Crucially, the Faraday effect rotates the primordial E-mode polarization into B-mode polarization, producing a correlated EB signature. Furthermore, this signal would not depend on the frequency of light, providing a clear way to test Gardner’s proposal. Indeed, in 2006 Bo Feng at the Chinese Academy of Sciences and co-workers, while searching for signs that nature violates a fundamental symmetry called CPT, hinted that such an EB signal already exists in the WMAP data (Phys Rev Lett 96 221302).

“The dark-matter proposal deserves further study, in particular to determine at which angular scales such effects would be evident,” says Gary Hinshaw at NASA’s Goddard Flight Center in Maryland. Hinshaw, who heads the data analysis for the WMAP science team, thinks the challenge will be to rule out a similar EB signal from synchrotron radiation produced in foreground galaxies, although he notes that this would have a strong frequency dependence.. “We are paying closer attention to our EB spectrum than ever because of these possible probes of new physics,” he adds.

Deposition improves medical implants

 

Plasma-enhanced sputtering and nanoparticle deposition are among the new physical techniques that allow the generation and controlled deposition of materials such as silver, silicon carbide and tantalum. These materials are of great interest to medical-device scientists because they can be used to create biocompatible coatings for medical implants. Such coatings reduce the chance that an implanted device will be rejected by the patient’s immune system or cause infection, and they will surely play a leading role in the evolution of medical-device science in the near future.

Mantis Deposition has developed a novel technique that allows the generation and deposition of nanoparticles in vacuum via magnetron sputtering under relatively high pressures. Unlike normal thin-film vacuum-deposition techniques, such as electron-beam evaporation or sputtering, our nanoparticle method provides control over the density and porosity of the coating. In addition, no heat is generated at the substrate, so the most delicate of materials, including organic molecules, can be coated. Finally, almost all other techniques for producing nanoparticles create a powdered material that has to be purified or refined further before being used for a coating, whereas our technique enables the direct generation, characterization and energy-controlled deposition of the nanoparticles to form a nanostructured coating in a single process. This has allowed us to produce revolutionary new materials and coatings.

The company is taking part in several European Union- and UK-funded research projects in the areas of antibacterial coatings, photocatalytic materials, fuel cells and biosensors. At the moment, for example, we are completing a project funded by the Department of Trade and Industry (now the Technology Strategy Board) that aims to develop a prototype system for creating antibacterial coatings. In the first instance, this will be used for cleaning medical instruments. These are usually sterilized in an autoclave — a pressurized device designed to heat aqueous solutions above their boiling point — but it has recently been noted that certain prions (protein-based infectious particles) can withstand the autoclave process. In contrast, our system first cleans the surface in vacuum using a radio-frequency plasma, which removes all contamination, and then applies a coating of silver nanoparticles that have been accelerated electrostatically.

Silver is known to have antibacterial properties, so this generates an active antibacterial coating. The accelerated nanoparticles also form an extremely adherent coating without the need for any binders or additives. This technology could also be used to make nanoparticle markers for use in magnetic resonance imaging, to coat medical implants, to make biosensors and, indeed, any application where careful control of the surface structure and stoichiometry could improve the functionality of a product.

Vacuum-deposition technology must overcome several challenges, however, if it is to be used to produce medical devices. Health and safety are of utmost importance, and regulations influence the materials that can be used as well as how they are produced. Factors such as adhesion of the coating are critical where the device is to be implanted because any bits of coating that come off can be harmful to the patient. With our nanoparticle technology it is possible to control the adhesion of layers by applying electrostatic acceleration to the charged nanoparticles. It is also import-ant that coated surfaces are very clean, and in vacuum it is possible to employ any of several techniques for surface preparation, including plasma cleaning and heating. Finally, the successful technique must be both technically and economically scalable.

These advantages mean that vacuum-deposition techniques are finding unique roles to play in the production of medical devices, in many cases where chemical techniques have failed to produce materials and coatings of sufficient quality. The new physical nanoparticle techniques are producing materials that have demonstrated more than significant increases in the performance of certain medical devices during clinical tests. Mantis owns intellectual property that addresses the issues of process efficiency and scaling-up, and we envisage that this technology will be used in a commercial product within two years.

Physicists get to the bottom of volcano hotspots

One of the mysteries of geophysics is how heat is transported from the Earth’s core, through the mantle and into the crust. A controversial aspect of this process is the idea that massive plumes of hot material from deep in the mantle well up towards the surface, causing volcano hotspots such as Iceland and Hawaii. Now, two physicists in the US have shown that — at least in theory — such mantle plumes could exist for long enough to cause hotspots.

The mantle is a region of dense rock that extends 50–3000 km below the surface of the Earth. Although the mantle is solid, geophysicists believe that it can also flow in response to the extreme temperatures and pressures generated by the Earth’s core. As a result, convective processes — such as mantle plumes — are likely to play an important role in how heat is transported through the mantle.

Laboratory experiments

The theory of mantle plumes got a boost in 1999 when Anne Davaille at the University of Paris 7 simulated them in a small tank containing two unmixed liquids of slightly different densities. Two liquids were used to mimic one of the many boundaries between rock layers that are believed to exist in the mantle.

When the denser liquid at the bottom of the tank was heated, Davaille observed several different types of behaviour ranging from violent mixing to the emergence of thin tendrils of denser liquid that extended up into the less dense fluid.

The tendrils formed on the boundary between the two fluids where the lower fluid pushed into the upper fluid to create a cone-shaped intrusion with a wide base and narrow top from which the tendril emerged. While the tendrils persisted for long periods of time, it wasn’t clear from the experiment whether the tendrils would occur on the density, time and length scales relevant to the Earth’s mantle.

Mathematical model

Now, Laura Schmidt and Wendy Zhang at the University of Chicago have come up with a new mathematical model of how tendrils form in Davaille’s experiments (Phys Rev Lett 100 044502). The researchers believe that their model can be scaled up to explain how mantle plumes many kilometres across could arise.

Schmidt and Zhang began with equations that described the shape and flow of the tendrils, which they solved using a combination of analytical and numerical techniques. Their calculations suggest that the cones occur at “stagnation points” which endure for long periods of time and anchor the tendrils. Such stagnation points have also been observed in a similar experiment done by Schmidt at the University of Chicago.

Schmidt told physicsworld.com that the tendrils remain stable for long periods of time because they remain isolated from larger-scale convective flow in the tank. This enduring quality of the tendrils is important, because mantle plumes responsible for hotspots would have to endure for more that 100 million years.

Possible mechanism

According to Schmidt, the calculations suggest that the tendrils “are a generic feature of convecting multi-layer liquids, and would be present in a layered mantle”. She describes the tendrils as “a possible mechanism behind hotspot persistence”.

Schmidt and Zhang now plan to do a more rigorous check of their theory against experiment by seeing if their model can predict the rate of flow through tendrils of different sizes. They are also doing a more detailed study of what factors affect the stability of the tendrils.

Empirical data help freeze-drying

Freeze-drying (lyophilization) is the process of freezing a material under vacuum to remove water. It is used to preserve a range of substances (most famously coffee) and plays an important role in the manufacture of pharmaceutical, biological and diagnostic healthcare products.

While commercial pharmaceutical freeze-drying has been commonplace for more than 60 years, controlling the process remains challenging and research continues into the methodologies involved – often driven by industry regulators. Most freeze-dried products are made by processes developed through trial and error, rather than from empirical data.

A small number of companies, including Biopharma Technology (BTL), are working to change this by developing analytical instruments to determine the temperatures at which materials go through key structural phase transitions. For BTL’s customers alone, this information has been crucial in controlling the quality of 470 different freeze-dried product formulations.

A freeze-dryer consists of a vacuum chamber where the product, often in vials, is placed on a special shelf, the temperature of which is controlled. Water vapour generated during the drying process is removed via a connection to a second vessel called an ice trap, which condenses the vapour into ice. Both vessels are maintained at vacuum levels down to 10–3 mbar. The shelf-temperature range is typically –50 °C to 60 °C and the ice trap is at –75 °C.

The freeze-drying process involves three main phases: freezing; primary drying; and secondary drying. Each involves exposing the material to different thermo-dynamic conditions and success relies on understanding the behaviour of the water during each phase.

In the freezing phase, close attention must be paid to the behaviour of both the solvent (usually water) and the solute(s) in the starting material. The way in which a solution freezes defines the structure and porosity of the final product and must be controlled very carefully. Ice formation is a two-stage process. The first stage is nucleation, which involves water molecules arranging themselves in tiny crystals or gathering around impurities. The second is crystal growth, and in freeze-drying the size and networking of the crystals are of more interest than their shape.

The solutes will freeze into a crystalline, amorphous or multiphase structure depending on the type of material. There are three critical temperatures that affect the process. These correspond to the eutectic (Teu) phase transition for crystalline material, and the glass transition (Tg) and collapse transition (Tc) for amorphous material. These usually define the maximum allowable temperature that the sample can be held at until all of the ice has been removed.

Ice is removed by sublimation during primary drying. However, sublimation cools the material and so energy must be put into the product to compensate for this. Energy is transmitted to the product mainly by gaseous convection and conduction, and transmission is controlled by adjusting the shelf temperature and chamber pressure. The pressure is controlled to within approximately ±5 × 10–3 mbar, typically over a range of pressures between 2 ×  10–2 and 50 × 10–2 mbar.

Only the top of the sample is exposed to the vacuum, so drying occurs from the top down. The sublimation interface, which moves down as drying proceeds, should be kept below the critical temperature of the product throughout primary drying to avoid processing defects. In crystalline systems, for example, the entire frozen mass should be maintained below Teu to avoid boiling, which can result in the product being splattered around the container.

Measuring the temperature of the sublimation interface is a significant challenge. Near-infrared thermal imaging has not been particularly successful, so instead the measured rise in vapour pressure can be used to calculate the temperature. Currently, however, the majority of commercial processes do not involve measuring the interface temperature.

Once sublimation is complete, the product will resemble a dried cake or powder, but it will often contain sufficient moisture to reduce shelf stability significantly. This moisture is referred to as “unfrozen water” and may be absorbed, associated or chemically bound to the product. It is removed by secondary drying, whereby higher shelf temperatures and lower chamber pressures are typically employed to encourage desorption of the unfrozen water.

A freeze-drying process can take from a few hours to several days to complete, and the length of each phase can vary significantly, depending on factors such as the product and the type of containers used, and their depth of fill.

New IUVSTA president looks forward

The International Union for Vacuum Science, Technique and Applications (IUVSTA) is a federation of 30 national vacuum societies and it represents about 15,000 scientists, engineers and technicians worldwide who are active in basic and applied research, development, manufacturing, sales and education. Bill Rogers, who took over as president of the IUVSTA last year for a tenure of three years, trained as a surface scientist. Currently he is associate laboratory director for energy and environment science and technology at the Idaho National Laboratory in the US.

What is the IUVSTA’s role within the international vacuum community?

The IUVSTA seeks to stimulate international collaboration in the fields of vacuum science, techniques and applications. It provides a strong programme of meetings, including the triennial International Vacuum Congress, an ongoing series of topical workshops and schools, and a regular series of European Vacuum Conferences. It also has a growing awards and recognition programme, and it has recently made great strides in expanding its educational efforts, which include a visual-aids series and a budding short-course programme. The IUVSTA also provides financial and organizational assistance to various international scientific groups and co-sponsorship for many of their activities.

How would you assess the current state of vacuum science and technology, both in academia and industry?

In my opinion, the study of vacuum science and technology peaked in the 1970s. For example, the last truly new innovation in vacuum measurement was the development and deployment of the spinning-rotor gauge, which dates back to the mid-1980s. This is not to say that vacuum technology has stood still: turbomolecular pumps are much more robust than they were 20 years ago; materials and coatings for vacuum applications have proliferated at a rapid rate; and innovation and improvement in electronics design have revolutionized displays, interfaces, computer controls and many other areas. So, while revolutionary changes in vacuum technology have been absent in the last few decades, what has kept the industry afloat is the never-ending list of applications where controlled environments, and thus vacuum technology, are necessary to study new phenomena. A few examples include surface, thin-film and nano science; semiconductor physics; and new areas of materials science, such as low-dimensional materials and high-temperature superconductors. In many cases, advances in these fields have rapidly led to commercialization, such as the use of optoelectronics for flat-panel displays. This in turn has been a boon for the vacuum-technology industry because most of the manufacturing techniques involved require some degree of vacuum. So the field continues to rejuvenate itself as new applications for vacuum emerge.

What do you see as the main challenges facing those involved in vacuum science and technology?

From an academic perspective, the postgraduate educational process is becoming increasingly interdisciplinary. To my knowledge there is no major university where vacuum science and technology is offered as a degree, yet it is a field that must be mastered in order to study other phenomena of interest. Graduate students usually pick up these skills via self-study or from a practitioner in the field; rarely from a formal course. I see this as a major challenge for students and postdocs who need a working knowledge of vacuum science and technology to pursue their varied research interests. This offers an opportunity for the IUVSTA to enhance its educational programme, particularly with regard to topical schools and workshops in highly specialized areas. From an industrial prospective, very little fundamental research is done in industrial labs; they usually concentrate on applied research and development. Most new innovation occurs in academia and many new applications reach the market through small companies that are spun-out of universities, so being first to the market with a new product is the real challenge.

What are your predictions for the future of vacuum science and technology?

I believe that field has a bright future because major advances in emerging and yet-to-be-discovered areas of interest will demand controlled environments. These environments are often created by the application of vacuum technology. Vacuum science and technology is an indispensable tool for cutting-edge science. A recent example is the completion of the US Department of Energy’s $1.2 bn Spallation Neutron Source at the Oak Ridge National Laboratory in Tennessee. Vacuum science and technology is also a necessity for advanced-materials processing and manufacture, as can be seen at any state-of-the-art semiconductor-fabrication facility. The IUVSTA is in the final stages of developing a strategic plan that will be implemented in this triennium. The plan will help the organization to pursue new opportunities in vacuum science, technology and related fields. Being at the heart of science and manufacturing is a good place to be, now and in the future.

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