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The masters of antimatter

Physics World reporter Tushna Commissariat recently visited the ALPHA antimatter experiment at CERN and caught up with its spokesperson Jeffrey Hangst. In this podcast, they talk about the perfect recipe for making antihydrogen, they discuss dealing with the fact and fiction that surrounds the field, and reveal the everyday realties of being an antimatter architect.

Housed within CERN’s Antimatter Factory, which includes the Antiproton Decelerator (AD) (the source that provides low-energy antiprotons), ALPHA and the other antimatter experiments – ACE, AEGIS, ATRAP and ASACUSA – all study the many puzzling facets of antimatter. From its interaction with regular matter to the biological effects of antiprotons to how it falls under gravity, the various experimental teams hope that all will be revealed about antimatter’s true nature in the coming years.

In particular, the ALPHA experiment – which won the Physics World Breakthrough of the Year in 2010 for trapping 38 antihydrogen atoms for about one-fifth of a second – is gearing up to scrutinize the stuff, as it will begin an experimental run this summer with the newly updated ALPHA2 device, which uses lasers to spectroscopically study the internal structure of the antihydrogen atom.

In addition to finding out how exactly one makes and holds a few thousand atoms of the most volatile stuff in the universe, listen to this podcast to find out why Hangst thinks he has the coolest job in the world and what it is like to visit the one place in the universe where, as far as we know, antimatter is actively being produced.

Astronomers fill supervoid in their knowledge

A cold spot in the cosmic microwave background — The cold spot (bottom right) resides in the southern galactic hemisphere. (Courtesy: ESA Planck collaboration)

Astronomers believe they may finally be able to explain the origin of the “cold spot”, a glaringly large cool region in the cosmic microwave background (CMB). Maps of the CMB, such as that created by the Wilkinson Microwave Anisotropy Probe (WMAP) and more recently by the Planck mission, reveal the distribution of radiation left over after the Big Bang. When in 2004 researchers noticed this cold spot on the map, they soon realized it was either a sign of exotic physics linked to the Big Bang itself or it was caused by some sort of structure in the foreground between the CMB and the Earth.

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Physicists generate electrical currents from noise

Two quantum dots have been used to generate an electrical current from voltage noise. The device was created by physicists in Germany, who say that it could lead to the development of systems that convert waste heat into useful energy.

Electronic devices generate large amounts of excess heat that must be dissipated. Instead of simply discarding this energy, using it to do useful work could revolutionize the electronics industry, and make it possible to create more efficient devices. Indeed, for more than a decade, physicists have been thinking up ways to convert this heat into electrical currents that can do work, such as power electronic devices.

Now, Lukas Worschech and colleagues at the University of Würzburg in Germany have verified experimentally that random voltage fluctuations can be rectified to drive a direct current. The experiment uses voltage noise to mimic the hot and cold spots of waste heat, and is therefore not a direct demonstration of waste heat being converted into work. However, team member Fabian Hartmann explains that it shows that small voltage fluctuations can drive a current: “A device derived from our sample might be able to provide the necessary power to drive autonomous and self-powered systems.”

Coupled quantum dots

The experiment comprises two quantum dots, which are discs of semiconductor about 300 nm in diameter. The quantum dots are separated by 150 nm to ensure that they exchange energy via Coulomb coupling – the electrostatic force that charged particles feel at a distance – as opposed to electrons physically jumping between the two subsystems. The researchers then connected three conducting leads to the system: two to the upper quantum dot to allow current to flow across the dot and one linking the lower quantum dot to a voltage source (several volts) with superimposed noise in the millivolt range.

While increasing the intensity of the noise applied to the lower quantum dot, the researchers measured larger currents across the upper quantum dot. The data followed a quadratic trend: doubling the voltage noise quadrupled the maximum current, at least for millivolt noise levels and currents measured in nanoamperes. “Certainly there is an upper bound that limits the device’s current. So far we have not tested these limits,” says Hartmann. The researchers also showed that they could reverse the direction of the current by changing the voltages of the leads attached to the upper quantum dot. This makes it energetically favourable for electrons to flow in one direction or another, depending on the voltage.

Getting warmer

One limitation to the team’s energy-harvesting scheme is that the quantum dots were immersed in liquid helium, which is clearly impractical for consumer electronics. Therefore, it will be critical to demonstrate that currents can still be driven at room temperature. “The biggest challenge is certainly to build a device that operates at room temperature,” notes Björn Sothmann, a researcher at the University of Geneva, who was not involved in the study.

In addition, further work is needed to show that currents can be driven by thermal fluctuations rather than voltage noise. “They do not create a true thermal gradient but mimic the effect by introducing noisy gate voltages,” says Rafael Sánchez of the Institute of Materials Science in Madrid, who published a theoretical study in 2012 that suggested that thermal fluctuations can drive a directed current. “However, the two effects [voltage fluctuations and thermal gradients] are closely related, so this study serves as a proof of principle for the rectification mechanism,” Sánchez concludes.

The research is described in Physical Review Letters.

Protests halt telescope construction on Hawaiian mountain

The summit of Mauna Kea, a dormant volcano on the island of Hawaii, has long been valued by astronomers for its pristine dark skies and high altitude. Rising to 4200 m at its peak, the mountain is the best location in the northern hemisphere to host astronomical observatories, and is currently home to 13 different telescopes. Long before the land was leased to the University of Hawaii for research purposes, though, the mountain was a sacred place for native Hawaiians.

Now, however, plans to build a new facility that will dwarf all others on the mountain are under threat, after construction of the $1.4bn Thirty Meter Telescope (TMT) was interrupted in late March when hundreds of native Hawaiians protested and prevented construction crews from entering the site. So far, 31 people have been arrested, and on 7 April Hawaii governor David Ige announced that construction would stop; it is not known when work will resume.

International collaboration

Designed to have a primary mirror 30 m across made of 492 hexagonal segments enclosed in a structure 66 m wide and 56 m tall, the observatory will allow astronomers to resolve the faintest and oldest galaxies. It is a collaboration between the California Institute of Technology (Caltech), the University of California, the National Astronomical Observatories of the Chinese Academy of Sciences, the National Institutes of Natural Sciences/National Astronomical Observatory of Japan, the Indian Institute of Astrophysics, the Association of Universities for Research in Astronomy, and the Association of Canadian Universities for Research in Astronomy.

To [the University of Hawaii], understanding one creation story is more important than the creation story of the islands they occupy
Kamahana Kealoha, Sacred Mauna Kea Hui

Members of the TMT project insist that they have the legal right to proceed after meeting all of the requirements to build the observatory, a process that took about seven years. “We followed the process slowly and carefully,” says Sandra Dawson from Caltech, who is TMT Hawaii community-affairs manager. “We got all the permits. We’ve been through the legal system. At every step, we have been approved.” Dawson adds that the TMT Corporation held some 30 public meetings open to the community to address possible concerns.

But many residents and conservationists say that laws have been circumvented, arguing that building the TMT will harm the delicate ecosystem on the mountain. A more fundamental concern, however, is their view that colonialism is impinging on the cultural and spiritual beliefs of the indigenous population. Since 1968 the University of Hawaii has leased more than 11,000 acres of land on Mauna Kea from the Hawaiian Department of Land and Natural Resources for scientific research.

“According to the Hawaiian world view, Mauna Kea’s summit is a place where creation begins,” says Kamahana Kealoha of Sacred Mauna Kea, one of the groups leading the protests. He adds that the University of Hawaii – which is subleasing the land on Mauna Kea to the TMT Corporation – “insist that the quest to see the origins of the universe is paramount. To them, understanding one creation story is more important than the creation story of the islands they occupy”, he says.

History, religion and culture

Upon seeing the concerns raised through the protests, some astronomers have begun to ask if construction of the observatory should continue. Emily Rice of the College of Staten Island in New York says that the astronomy community needs to talk about the issues raised by the protestors. “The discussion can’t just be science, funding and environmental impact. It has to be history, religion and culture,” she says. “Those [aspects] are things that scientists traditionally tend to stay away from. But we really can’t, in good faith, ignore these aspects of our work anymore.”

Amid the protests last month, Canada announced that it would provide $243.5m over 10 years toward the TMT’s construction.

Nanometre-scale printing technique could put its stamp on the electronics industry

This year marks 20 years since Stephen Chou, Peter Krauss and Preston Renstrom first published their work showcasing a versatile approach for mass production of identical nanostructures for the electronics industry. This technique is called nanoimprint lithography and it involves pressing a nano-patterned structure into a hot molten polymer. As the polymer cools, the pattern stamped into it sets so that it can be used as a mould to make several identical replicas of the original structure.

Just as the printing press brought literature to the masses, it is easy to imagine how this nanofabrication technique could have a significant impact on the production of integrated circuits. To commemorate the development, Nanotechnology has published a perspective article on the technique, and I had a chance to talk to the author Qiangfei Xia of the University of Massachusetts at Amherst about the technique’s advantages, challenges and outlook for the future.

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Heavy-metal Higgs, meet the Publons, Stephen Hawking's galactic tour and more

By Tushna Commissariat and Hamish Johnston

I’m sure that most of you have wondered what the Higgs boson would sound like if it were a heavy-metal song. Now you can turn it up to 11 (TeV that is) courtesy of CERN physicist and guitarist Piotr Traczyk, who has “sonified” data from two plots from the CMS experiment that were presented at the Higgs discovery seminar on 4 July 2012. His heavy-metal ditty is based on gamma–gamma and 4-lepton data from CMS and after you listen to his excellent song in the above video, you can find out more about how it was created by reading this entry by Traczyk on the Cylindrical Onion blog.

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Philae comet lander set for reboot

Artist's impression of Philae on the surface of comet 67P — Here comes the Sun: the Philae lander may reawaken soon. (Courtesy: ESA/ATG medialab)

Scientists at the European Space Agency (ESA) are hoping that the Philae lander, which successfully landed on a comet last year, will re-establish contact soon as it travels closer to the Sun. Philae was part of ESA’s Rosetta mission that was launched in 2004 but when Philae separated from Rosetta in November, it landed on the comet in an awkward position. This meant that the craft’s solar panels did not receive enough sunlight to recharge its battery, but the lander’s 10 instruments were able to carry out measurements before it went into hibernation mode about 50 hours after landing.

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ALMA debuts its high-resolution results

Scientific results of the highest resolution observations yet attempted by the Atacama Large Millimeter/submillimeter Array (ALMA) telescope are described in four papers to be published this month in Astrophysical Journal Letters. The observations were part of a campaign to test ALMA’s capabilities when run in its long-baseline configuration, and the result is stunning images and data for five astronomical objects. These include the planet-forming disc of HL Tau, the tumbling asteroid Juno, and a lensed galaxy 12 billion light-years away. These results are not only rich with new insights, but they also give us a sense of the incredible capabilities that ALMA will provide in the future.

ALMA is an array of 12 m- and 7 m-diameter antennas that observe the cosmos at millimetre/submillimetre wavelengths. The antennas work together to function as an interferometer, and this allows the signals from each of the antennas to be combined to simulate a telescope the size of the distance between the individual units. The array works like a zoom lens on a camera: the antennas can be repositioned so that the baseline of the simulated telescope is as small as 150 m or as large as 15 km across.

Expecting the unexpected

ALMA’s capabilities in its wavelength regime are revolutionary. The array is the largest and most sensitive millimetre/submillimetre instrument in the world, and its resolution is 10 times better than even the Hubble Space Telescope. As Anneila Sargent, chair of the ALMA board while the array was being built, predicted in 2008, “We know that every time in the past that a new wavelength region has been opened up, as ALMA will do, we have been surprised by entirely unexpected discoveries that significantly changed our understanding of the universe. We also expect the unexpected from ALMA.”

In its smaller configurations, ALMA can study the large-scale structure of cold gas and dust in the universe – and this is how the array has been used since it began its first early-science operations in 2011. But now, ALMA is beginning to test its long-baseline configuration, in which it is able to make its highest resolution observations and study the small-scale structure of objects in detail.

ALMA’s Long Baseline Campaign, which ran in late 2014, observed five targets using 22–36 antennas arranged with a baseline of up to the maximum 15 km. The targets were specifically selected to push the limits of ALMA’s capabilities: each target has a small angular size (less than two arcseconds) with a fine-scale structure that had been largely unresolved in previous observations made with other telescopes. Two of the targets, the variable star Mira and the active galaxy 3C138, were primarily used for calibration and comparisons of ALMA data with those of other telescopes. The remaining three targets not only demonstrated ALMA’s capabilities, but also resulted in new science discoveries.

Image of the protoplanetary disc surrounding the star HL Tau — Possible planets: the protoplanetary disc surrounding the young star HL Tau. ALMA has revealed a structure within the disc that indicates possible planet formation. (Courtesy: ALMA (NRAO/ESO/NAOJ))

The first discovery involves HL Tau, which is a young star surrounded by a protoplanetary disc – a disc of gas and dust from which planets can be born. ALMA’s detailed observations of this region revealed a remarkable structure within the disc: a series of light and dark concentric rings indicative of planets caught in the act of formation. Studying this system is allowing scientists to better understand how multi-planet solar systems, like our own, form and evolve.

Juno, which is one of the largest asteroids in our solar system’s main asteroid belt, is the subject of the second discovery. ALMA’s observations of Juno were made when the asteroid was approximately 295 million kilometres from Earth. The 10 images ALMA took have been stitched together into the brief animation shown below, which shows the asteroid tumbling through space as it orbits the Sun. ALMA’s observations are not of reflected light, but rather of the millimetre-wavelength light emitted by the asteroid itself. The resolution of these images is good enough to study the shape and even some surface features of the asteroid – something that is unprecedented for this wavelength.

The final discovery concerns the star-forming galaxy SDP.81, which is so far from Earth that the light we see was emitted when the universe was only 15% of its current age. The galaxy is only visible because of a fortuitous alignment between it and a nearby foreground galaxy. The gravity of the foreground galaxy acts as a lens and bends the light from SDP.81 into a highly magnified cosmic ring. The combination of this lucky alignment and ALMA’s high resolution gives scientists a spectacularly detailed view of this distant galaxy, allowing them to study the actual shape of the galaxy and motion within it. This is ALMA’s highest resolution observation so far, and is described by Alma astronomers as being “about the same as seeing the rim of a basketball hoop atop the Eiffel Tower from the observing deck of the Empire State Building”.

The observations from ALMA’s first test of its long baseline clearly demonstrate that exciting times are ahead as scientists gear-up for the next cycle of observations. “It takes a combination of ALMA’s high resolution and high sensitivity to unlock these otherwise hidden details of the early universe,” says ALMA director Pierre Cox. “These results open a new frontier in astronomy, and prove that ALMA can indeed deliver on its promise of transformational science.”

How to efficiently capture carbon dioxide out of thin air

A novel synthetic material that is a thousand times more efficient than trees at capturing carbon dioxide from the atmosphere was presented by Klaus Lackner, director of Arizona State University’s new Center for Negative Carbon Emissions, at a meeting of the American Physical Society in Maryland last Sunday. According to Lackner, the amount of carbon dioxide in the atmosphere has reached the point where simply reducing emissions will not be enough to tackle climate change. Referring to recent environmental reports, Lackner emphasized the need for prolonged periods of carbon capture and storage – also known as “negative carbon emission”.

Trees and other biological matter are natural sinks of carbon dioxide but they do not trap it permanently and the amount of land required is prohibitive. “There is no practical solution that doesn’t include large periods of negative emission,” says Lackner, adding that “we need means that are faster than just growing a tree.” During the past few years, Lackner and his colleagues have developed a synthetic membrane that can capture carbon dioxide from the air passing through it. The membrane consists of an “ion-exchange” resin – positive anions in the resin attract carbon dioxide, with a maximum load of one carbon-dioxide molecule for every positive charge. This process is moisture sensitive, such that the resin absorbs carbon dioxide in dry air and releases it again in humid air. As a result, this material works best in warm, dry climates.

Show and tell

Lackner plans to install corrugated collecting panels incorporating the membrane material on the roof of the Center for Negative Carbon Emissions this summer. The researchers hope that this public installation will demonstrate the economic feasibility and efficiency of a new technology that can address the issue of climate change, and help shift the debate from reduced carbon emissions to negative carbon emissions.

To keep costs low, the first step – capturing the carbon from the air – is free. “We made it cheap by being passive. We can’t afford to be blowing air around,” says Lackner. The resin itself is readily available and can be mass-produced, because it is already widely used to soften and purify water. The collectors trap between 10 and 50% of the total carbon dioxide that passes through. Compared with the amount of carbon dioxide that a typical tree collects during the course of its lifetime, these panels are a thousand times more efficient.

Panels of carbon-capture resin — Able membrane: corrugated panels of carbon-capture resin will be installed on top of the Center for Negative Carbon Emissions this summer. (Courtesy: Jessica Hochreiter, Arizona State University)

“I believe we have reached a point where it is really paramount for substantive public research and development of direct air capture,” says Lackner. “The Center for Negative Carbon Emissions cannot do it alone.”

Post trappings

Lackner estimates that about a hundred-million shipping-container-sized collectors would be needed to deal with the world’s current level of carbon emissions. As these collectors would typically become saturated within an hour, Lackner envisions a possible “ski-lift” approach where saturated panels are taken away to a humid environment to release their carbon dioxide and then recycled back to the dry air for more carbon capture.

The question also remains of what to do with the carbon dioxide once it is trapped. Burying it is one option, which is something Lackner says is likely, given the sheer quantity of carbon that must be captured. His centre is also testing ways to recycle the carbon dioxide and sell it to industries that could use it to make products such as fire extinguishers, fizzy drinks and carbon-dioxide-enhanced greenhouses, and even synthetic fuel oil.

Balloon-borne experiment will reveal how cosmic rays damage computer memories

By Tamela Maciel at the APS April Meeting in Baltimore, Maryland

Little bits: the CRIBFLEX logo. (Courtesy: Drexel University Society of Physics Students)

A group of undergraduate students at Drexel University in Philadelphia is ready to click “confirm” on an Amazon order that will include a weather balloon, a memory storage device, a GPS, a Geiger counter and a BeagleBoard computer (described to me as a “beefier version of Raspberry Pi”). For less than $2000, this team of physics, engineering and computer-science students plans to launch a weather-balloon experiment that will measure the effects of cosmic rays on DRAM memory devices at high altitudes.

The team is part of the Drexel University Society of Physics Students and the members presented their experiment design at the April Meeting of the American Physical Society in Baltimore, Maryland, last weekend.

DRAM is a very quick and simple type of electronic memory – each bit takes the form of a capacitor that either has charge or doesn’t, according to whether it’s storing a zero or one. Unfortunately, this simple design can make the bits very sensitive to radioactivity or cosmic rays, which can cause bits to flip values and introduce “soft errors” into the data.

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The masters of antimatter

Astronomers fill supervoid in their knowledge