It’s not often that physics, or indeed a physicist, has much in common with pop music or exceedingly popular boy bands. But earlier this week, at an event at the Sydney Opera House titled “An Evening with Stephen Hawking, with Lucy Hawking and Paul Davies”, an audience member asked Hawking (who appeared in holographic form) “What do you think is the cosmological effect of Zayn Malik leaving One Direction?” Watch the video above to see what Hawking said to comfort the distraught fan and how theoretical physics truly may have all the answers.
A couple of years back, I had the pleasure of travelling 1100 metres below ground to visit a dark-matter laboratory at the bottom of the Boulby Mine on the north-east coast of England. The journey was certainly memorable – it involved plunging down in a rattling lift cage for several minutes with a group of miners setting off on their morning shift. Once in the lab – housed inside a souped-up set of trailers – I interviewed physicist Sean Paling about the experimental projects going on there.
Setting up an underground lab, like that at Boulby, certainly doesn’t come cheap and in recent years, many have started to diversify into new areas. In the May issue of Physics World, which is now out in print and digital formats, Paling and his colleague Stephen Sadler – who is director at DURRIDGE UK Radon Instrumentation – describe the renaissance in the science taking place far beneath our feet. Studies in underground labs now range from Mars rovers to muon tomography and from radioactive dating to astrobiology.
After four years studying Mercury in great detail, NASA’s $446m Mercury Surface, Space Environment, Geochemistry (MESSENGER) mission has come to an end. MESSENGER was the first spacecraft to visit Mercury since the mid-1970s, when the Mariner 10 probe flew past the planet three times. MESSENGER crashed into the planet yesterday after using up all of its fuel, while continuing to take data until the very end.
First proposed in 1996, MESSENGER was launched from Cape Canaveral aboard a Delta II rocket on 3 August 2004. It then made its way to Mercury – a 7.9 billion-kilometre journey – completing a fly-by of Earth, two fly-bys of Venus and three of Mercury itself. In 2011 MESSENGER became the first craft to orbit Mercury, with the craft entering a highly elliptical orbit around the planet that ranged from an altitude of 200 km at its nearest to about 15,000 km at its furthest point.
New discoveries
Having orbited Mercury more than 4000 times over the past four years, the 513 kg spacecraft has mapped and imaged the inner planet, worked out its geological history, discovered that its internal magnetic field is offset from the planet’s centre and found a surprising amount of water in its exosphere. MESSENGER’s nine instruments – including cameras, spectrometers and magnetometers – also uncovered evidence for past volcanic activity, as well as the possibility that Mercury has a liquid-iron core. In 2014 scientists even suggested that the probe had unearthed signs of an annual meteor shower on Mercury.
The MESSENGER spacecraft has given us much of what we now know about one of Earth’s nearest neighbours
Sean Solomon, MESSENGER principal investigator
“The history of solar-system exploration has taught us that the first spacecraft to orbit a planet, because of its global perspective and the opportunity for continuous observations over an extended period, always provides a huge increase in information,” MESSENGER principal investigator Sean Solomon, who is director of Lamont Doherty Earth Observatory at Colombia University, told physicsworld.com. “Over the last four years, the MESSENGER spacecraft, – the latest example of this lesson – has given us much of what we now know about one of Earth’s nearest neighbours.”
After running out of propellant late last year, MESSENGER began to enter a “terminal” orbit. In the last few weeks it began to use up its helium reserves that extended the craft’s operation by a couple of weeks. But with that since exhausted, the craft – travelling at around 14,000 km per hour – plummeted into the planet creating a crater some 15 m wide.
“I have worked on MESSENGER for 14 years, so seeing the end of the mission is bittersweet – it has been far more successful than any of us could ever have hoped or dreamed, but we are extremely sad to see the end of this tough and capable little spacecraft,” says Louise Procker, a planetary scientist at the Johns Hopkins University Applied Physics Laboratory who is also deputy project scientist on MESSENGER. “MESSENGER’s legacy will be huge: not only have we discovered so much about how the innermost planet evolved to its present state, we have also learned more about how terrestrial planets work, which helps us understand why the Earth is such a special place.”
Future missions
MESSENGER, however, will not be the last probe to visit Mercury. BepiColombo – a joint mission of the European Space Agency and the Japan Aerospace Exploration Agency – will pick up where MESSENGER left off. To be launched in 2017, it will comprise two satellites – the Mercury Planetary Orbiter and the Mercury Magnetospheric Orbiter – that are planned to enter orbit around Mercury in 2024. “MESSENGER’s discoveries have raised many new questions about the innermost planet, so it is heartening that two spacecraft are scheduled to be launched to Mercury two years from now,” Solomon adds.
A practical, portable ultralow-field magnetic resonance imaging (MRI) system has been unveiled by researchers from the Los Alamos National Laboratory in the US. With its low power requirements and lightweight construction, the researchers hope that their prototype design can soon be deployed for use in medical centres in developing countries as well as in military field hospitals.
MRI is a powerful medical diagnostic tool, which can be applied to the detailed imaging of a variety of soft tissues, in particular the brain. MRI scanners work by using large, powerful magnets to align the protons (hydrogen atoms) in water molecules. Short bursts of radio waves are then used to excite the protons, which as they relax give off weak radio waves the scanner can detect. Image contrast is provided by the varying relaxation times between different tissue types. Despite their usefulness, however, conventional MRI systems require both a considerable source of power and a supply of cryogens, such as helium or liquid nitrogen, to keep the magnets cool and functioning. On top of that, they are expensive to build and bulky to house.
Scaling down
“Standard MRI machines just can’t go everywhere,” explains project leader Michelle Espy, a physicist at Los Alamos. “Soldiers wounded in battle usually have to be flown in to a large hospital – and people in emerging nations just don’t have access to MRI at all.”
To scale down the scanners, Espy and her team have made use of ultralow magnetic fields, which have intensities comparable to that of the Earth’s magnetic field, to develop what they call “battlefield MRI” (bMRI). To detect the much weaker signals, their machine uses a superconducting quantum interference device (SQUID), which acts as an extremely sensitive magnetometer. While previous research has demonstrated the potential of ultralow-field MRI scanners, it has been limited by poor image qualities, long imaging times and – most critically – an impractical need to operate in an environment almost entirely isolated from ambient electromagnetic noise. “SQUIDs are so sensitive they’ll respond to a truck driving by outside, or a radio signal from 50 miles away,” explains Al Urbaitis, an engineer at Los Alamos.
To combat potential sources of interference, the team built its first prototype device within a large metal enclosure, which acted as a shield. The researchers scanned the brains of human test subjects, producing images with a special resolution of 2.1 × 2.4 mm2, with a 15 mm slice thickness. Having used this set-up to demonstrate their machine’s potential, the researchers have now switched to developing a second iteration of the device that works in an open environment. In the new design, shielding is offered by a series of lightweight wire coils, which encircle the scanner. Currently, the coils only compensate for the Earth’s magnetic field, but the team is confident the shielding can be enhanced to cancel out additional interference on the fly.
Clear imagery
“We’ve been very happy with some of the initial imagery that’s been produced from the lightweight, second-generation system,” says Espy, adding that “with additional development, these systems could be relatively easy and inexpensive to deploy”.
The team has been working towards a military medical application, but is also investigating the potential benefits the device could provide in developing countries that do not have access to conventional MRI. In addition, ultralow-field MRIs also have the potential to be used in situations where – because of the powerful magnets – conventional MRI is not suitable. For example, an ultralow-field machine could be used in emergency situations where metal cannot practically be excluded from the scanning environment.
“The ultralow-field MRI images presented by [the researchers] are very impressive and encouraging for all other groups working along similar lines of research,” says Peter Blümler, a physicist from Johannes Gutenberg University Mainz in Germany, who is not a part of the Los Alamos team. He adds “Personally, I do not see portable MRI systems replacing the high-field equipment, but rather complementing the diagnostic potential of magnetic resonance.” Mark Cohen, a bioengineer from UCLA in the US who was also not involved in this study, is impressed with the work, especially as it represents the first practical test of the principle at the scale of a true human imaging system.
Restricted Data is a blog about the history of nuclear weapons and the efforts policy-makers and scientists have made to try to keep this history secret. Its author is Alex Wellerstein, a historian of science at the Stevens Institute of Technology in New Jersey, US, whose CV includes a one-year stint as the “Edward Teller Graduate Fellow in Science and Security Studies” at the US Department of Energy (“still my best job title” he writes). Wellerstein’s academic research interests lie in the same area, but in the blog, he is writing for a general audience.
What are some of the topics covered?
Most posts on Restricted Data deal with events from the 1940s and 1950s, such as the Manhattan Project to build the first atomic weapons and the US and Soviet hydrogen bomb tests. Over the past decade or so, many formerly secret documents related to this period have been declassified, and others are emerging all the time. Wellerstein is also interested in less-well-studied aspects of nuclear history. One recent post (with the arresting title “How to die at Los Alamos”) focuses on occupational safety at the wartime weapons lab, while another complains about the use of fake “mushroom cloud” photographs (and their associated physical inaccuracies) in books.
Anything else of note?
As well as the blog itself, Wellerstein has also built a tool called Nukemap that models what would happen if a nuclear device were to explode in a certain location. Users of Nukemap can specify the device’s yield (in kilotons), the type of explosion (airburst or surface) and a few other parameters, as well as choosing where the explosion takes place. From a policy perspective it is, perhaps, reassuring to know that if a “crude nuclear terrorist weapon” with a yield of 0.1 kilotons went off in a city centre, few if any people would die in the blast itself, and prompt medical care would save the lives of most of the radiation casualties. But it is quite another thing to look at a map centred on your own house, and imagine what even a “minor” nuclear incident would do to familiar people and landmarks nearby.
Why should I visit?
For those who want to learn more about the history of nuclear weapons, Wellerstein’s blog offers an accessible introduction to a wide range of “science and society” issues, from the morality of the atomic bombings of Hiroshima and Nagasaki during the Second World War to the health risks of radioactive fallout from later nuclear tests. Perhaps more importantly, though, Restricted Data is a good reminder that, like scientists, historians are in the business of analysing data, using it to construct theories, and then checking those theories against new facts that emerge. The declassification of once-secret documents is part of this historical-scientific process, and reading Restricted Data will help you appreciate how perceptions of our scientific past are changing.
Can you give me a sample quote?
From a post about the first Soviet hydrogen-bomb test: “The fully loaded Tu-16 bomber had to abort when the test site was unexpectedly covered by clouds, making them unable to see the target aiming point and rendering the optical diagnostic systems inoperable. The plane was ordered to land, only now it had a fully armed experiment H-bomb on board. There was concern that if it crashed, it could result in a nuclear yield…destroying the airfield and a nearby town. The airfield had meanwhile iced over. Igor Kurchatov, the lead Soviet nuclear-weapons scientist, drove out to the airfield himself personally to see the airfield. [Weapons scientist and later dissident Andrei] Sakharov assured him that even if it crashed, the odds of a nuclear yield were low. An army unit at the airfield quickly worked to clear the runway, and so Kurchatov ordered the plane to land. It did so successfully. Kurchatov met the crew on the field, no doubt relieved. Sakharov recalls him saying, ‘One more test like [this one] and I’m retiring.’ As for Sakharov, he called it ‘a very long day’.”
New real-time information about the electric fields that create lightning could be obtained from the radio waves formed when cosmic-ray showers pass through thunderstorms. That is the conclusion of an international team of physicists, after examining the data recorded by a radio telescope during electrical storms. The team saw changes in radio emissions from charged particles, which computer models suggest are due to deflections by the strong electric fields in thunderclouds.
About 40 flashes of lightning occur every second around the world, according to satellite imaging. While most are harmless, lightning strikes can damage buildings and even kill people. Some of this destruction could be mitigated if we knew where and when lightning will strike, but such predictions are hard because we understand so little about how lightning is created. Thunderstorms evolve quickly and unpredictably, making it tricky to use instruments on rockets or balloons to measure the huge electric fields that build up in thunderclouds before a lightning discharge.
Showers from space
The new research takes a different tack and studies the shower of particles created when a high-energy cosmic particle collides with an atomic nucleus in the atmosphere and sets off a shower of particles that rain down towards Earth. Many of these particles are electrically charged and so get deflected by the Earth’s magnetic field. This deflection causes the particles to emit radio waves that can be detected by a radio telescope.
According to calculations carried out in 2010 by Heino Falcke at Radboud University in the Netherlands, and colleagues, both the polarization and the intensity of these radio waves would be altered in a measurable way by electric-field gradients above about 10 kV/m, which is a typical value found in a thundercloud.
While these calculations were done mainly to help astrophysicists filter out the effect of electric fields on radio studies of cosmic rays, Falcke and colleagues have now joined up with geophysicists and astrophysicists to measure the electric field in thunderclouds using a radio telescope for the first time.
Led by the Radboud-based astrophysicist Pim Schellart, the team sifted through data taken in 2011–2014 by the Low Frequency Array (LOFAR) radio telescope in the Netherlands. The telescope had spotted 762 air showers in this time, but only about 60 events could not be explained by magnetic deflection alone. Further analysis identified 31 of these events as having sufficient signal-to-noise ratio to allow further examination.
Messy throwaways
Schellart describes these as throwaway events that would not normally have been analysed because they are “too messy”. But records held by the Royal Dutch Meteorological Society show that lighting strikes had occurred within 2 h and 150 km of 20 of the 31 anomalous showers, enabling Schellart and colleagues to argue that the remaining 11 events might correspond to atmospheric electric fields that did not lead to recorded lightning strikes.
The team then used a computer simulation to analyse telescope data from one of the lightning events. Their modelling suggests that the radio waves were produced in a thundercloud that extended from 3 km above the ground to a maximum altitude of 8 km – which are both reasonable values for a thundercloud. It is possible that the cloud extended beyond 8 km, but above that altitude there would have been fewer charged particles because the shower would not have been fully developed.
Gradient makes the grade
The analysis also suggests that the electric-field gradient was 50 kV/m at the top of the cloud and 27 kV/m in its lower reaches, which again are typical values for a thundercloud. Interestingly, the researchers found that increasing the electric-field gradient in their model beyond 50 kV/m led to very little change in the predicted radio-wave intensity – an effect that they are now investigating.
“How the radio emission changes gives us a lot of information about the electric fields in thunderstorms”, says Schellart, adding, “We could even determine the strength of the electric field at a certain height in the cloud.” His team has also installed an electric-field meter at LOFAR to further understand anomalous events that do not correspond to recorded lightning strikes.
Birds flock over Central Park. (Courtesy: iStockphoto/giovanni1232)
It’s been a great week for birds – or at least those flying over the state of New York – after state governor Andrew Cuomo pledged to create safer migration routes for our feathered friends. All state buildings will now have to comply with a national US initiative that seeks to curb levels of light pollution, which can disorient birds and lead to huge numbers of avian deaths by “fatal light attraction”.
Many species of bird rely on the light from star constellations to help them navigate during spring and autumn migrations. Unfortunately, artificial light sources can throw the animals off course, and light reflected from glass can cause the birds to smack into windows, walls, floodlights and other hard surfaces. It is estimated that as many as a billion birds succumb to this cruel end each year in the US alone, according to the US Department of Agriculture.
This is the fifth and final instalment of our “five amazing physics demonstrations” presented by science-demo guru Neil Downie and his adept assistant Matthew Isbell.
In a special feature in the April issue of Physics World, Downie describes his five best demos of all time, all of which use everyday equipment to illustrate fundamental physics concepts. Downie describes how his fondness for the five experiments comes from the fact that, with a bit of creativity, each one can be easily adapted to explore physical concepts further. In the digital edition of the April issue, each demonstration is accompanied by a video in which Downie walks you through how you would present each demonstration to an audience. Full details of how to access the digital edition are available at the bottom of this article.
In this final demo of the series, Downie uses a model train set equipped with an ultrasound emitter to demonstrate the Doppler effect. Employing a bat detector to convert the ultrasound signal into an audible sound, Downie illustrates how the pitch increases as the train steams towards him, and then decreases as it moves away. The train set brings a potentially dry subject to life and Downie uses the set-up to explain how bats utilize the Doppler effect when hunting for prey.
Double Doppler with Train Set
So what’s this all about? The Doppler effect is of fundamental importance in physics, not least because measuring the redshift of light from galaxies lets us estimate how far away they are. When it comes to sound, however, demonstrating the Doppler effect is not easy. You could get someone on a passing train to play a trumpet or try whirling an electronic beeper around on a string – but neither is particularly simple. What is more, the Doppler shift is small and can be masked by changes in sound volume. This project is a much neater way of showing the Doppler effect and has the added bonus of bringing ultrasonic waves to life.
What bits and pieces do I need? You will need an electronic bat detector – a hand-held device that converts ultrasound into audible sound. You’ll also need an ultrasonic transducer, such as the kind fitted to cars to help drivers park. Such devices, which emit ultrasound at about 40 kHz, are normally hooked up to a separate microprocessor circuit to create pulses. So to get a continuous source of waves, you’ll need to connect the emitter to an oscillator circuit. Finally, you need to attach the transducer to a moving vehicle – a toy train running on a circular track is ideal.
How do I get going? Lay the track somewhere without too many flat walls or in the corner of a room (this reduces reflections). Turn on the ultrasonic emitter and put it in the train. Then switch on your detector. If you’re standing still, you’ll hear the pitch of the signal rise and fall with a characteristic “heeeEEEeeaaAAAAaaaaw” as the train first approaches and then moves off. There’s a steady high note as the train approaches, and a steady low note as it recedes, with a modulating pitch in-between.
And what physics will I learn? If you’re standing still and the train’s approaching you at speed v, the frequency of the sound received, fr, will differ from the emitted frequency, fe, according to the classic textbook formula fr = fe[c/(c – v)], where c is the speed of sound. (The formula is fr = fe[c/(c + v)] if the train is moving away.) If the sound were at an audible frequency of about 2 kHz, then for a source approaching at 0.5 ms–1, the detected frequency would rise by just 3 Hz, which would be hard to hear given that a semitone in music is 120 Hz. A 40 kHz ultrasonic system moving at the same speed, however, will have a Doppler shift of about 60 Hz, which is easy to notice if you adjust the bat detector so it emits, say, 1000 Hz waves when it receives 40 kHz ultrasound – it will be about a whole musical tone different. You could also use your equipment to detect other sources of ultrasound, from rubbing fingers and whistling fluorescent lamps to electronics and clanging metals. Or even bats.
If you’re a member of the Institute of Physics (IOP), you can now enjoy immediate access to the April issue of Physics World with the digital edition of the magazine
A search of 100,000 galaxies for signs of highly advanced extraterrestrial life, carried out by researchers in the US, has found no evidence that they harbour advanced civilizations. Scouring through observations from NASA’s WISE orbiting observatory, the researchers looked for unusually high amounts of mid-infrared radiation, which could mark out a colonized galaxy. The research is a significant expansion of previous work, which only studied about 100 galaxies. Although the team has not found any obvious signs of advanced life just yet, it has come across some puzzling new sources of mid-infrared radiation that need further study.
In 1960 the eminent physicist Freeman Dyson suggested that highly advanced alien civilizations beyond the solar system could be detected by the inevitable waste heat that they would produce in the form of mid-infrared emissions. He reasoned that such civilizations would have developed technologies that extracted useful energy from starlight by converting it into mid-infrared radiation. In a paper published in the journal Science, Dyson proposed that “a search for point sources of infrared radiation be attempted, either independently or in conjunction with the search for artificial radio emissions”. But such searches were only made possible once space-based telescopes like WISE were developed.
Hot on ET’s heels
Together with colleagues in the US, Jason Wright of Penn State University began the so-called Glimpsing Heat from Alien Technologies Survey (G-HAT), which makes use of WISE. “Whether an advanced spacefaring civilization uses the large amounts of energy from its galaxy’s stars to power computers, spaceflight, communication or something we can’t yet imagine, fundamental thermodynamics tells us that this energy must be radiated away as heat in the mid-infrared wavelengths,” explains Wright, adding that this “same basic physics causes your computer to radiate heat while it is turned on”.
Team member Roger Griffith, also at Penn State University, combed the entire WISE catalogue of detections – nearly 100 million entries – for objects consistent with galaxies emitting too much mid-infrared radiation. He then individually examined and categorized around 100,000 of the most promising galaxy images. The researchers’ extensive search did not throw up any obvious candidates for an alien civilization reprocessing more than 85% of its starlight into the mid-infrared wavelength. But they did find about 50 galaxies that have unusually high levels of mid-infrared radiation. “Our follow-up studies of those galaxies may reveal if the origin of their radiation results from natural astronomical processes or if it could indicate the presence of a highly advanced civilization,” says Wright.
In any case, the very fact that the extensive search did not find any colonized galaxies is curious in itself. Many of these galaxies are billions of years old, giving plenty of time for technologically advanced civilizations to form and establish. “Either they don’t exist, or they don’t yet use enough energy for us to recognize them,” says Wright.
WISE curiosities
“Once we had identified the best candidates for alien-filled galaxies, we had to determine whether they were new discoveries that needed follow-up study or well-known objects that had a lot of mid-infrared emission for some natural reason,” says Matthew Povich, who is part of the G-HAT team and is based at the California State Polytechnic University in Pomona. All told, the researchers found about half a dozen objects that were both unexpected and potentially interesting to study in the future to determine exactly which natural astronomical phenomena may be causing the results.
Among the discoveries within our own Milky Way galaxy, the team spotted a bright nebula around the nearby star “48 Librae”, and a cluster of objects easily detected by WISE in a patch of sky that appears totally black when viewed only in the visible spectrum. “This cluster is probably a group of very young stars forming inside a previously undiscovered molecular cloud, and the 48 Librae nebula is apparently caused by a huge cloud of dust around the star, but both deserve much more careful study,” says Povich.
Wright believes that more careful future observations of light from galaxies with higher-than-expected mid-infrared emissions will “push our sensitivity to alien technology down to much lower levels, and to better distinguish heat resulting from natural astronomical sources from heat produced by advanced technologies. This pilot study is just the beginning”.
Going in circles: a Project 8 team member adjusts the experiment. (Courtesy: Project 8)
The cyclotron radiation emitted by a single electron has been measured for the first time by a team of physicists in the US and Germany. The research provides a new and potentially more precise way to study beta decay, which involves the emission of an electron and a neutrino. In particular, it could provide physicists with a much better measurement of neutrino mass, which is crucial for understanding physics beyond the Standard Model.
The Standard Model of particle physics assumes that the mass of neutrinos is zero, but in 1998 the Super-Kamiokande detector in Japan showed conclusively that the particles undergo oscillations and therefore must have mass. Knowing the masses of the three known types of neutrino is crucial to understanding physics beyond the Standard Model, but actually measuring the masses is proving extremely difficult. “Currently, we know more about the mass of the Higgs boson, which was discovered two years ago, than we do about the mass of the neutrino, which was discovered 60 years ago,” says Patrick Huber of Virginia Tech in the US.
Studies of neutrino oscillations tell us only that the average neutrino mass must be at least 0.01 eV/c2, so researchers are also trying to measure the mass using conservation of energy in beta decay. This is a nuclear process that involves the emission of an electron and a neutrino – strictly speaking, an electron antineutrino. Neutrinos are extremely difficult to detect, so physicists instead measure the energy of the electron and use this to calculate the mass of the neutrino.
Upper bound
The best measurements so far give an upper bound on the electron antineutrino mass of 2.05 eV/c2. Scientists are assembling a new detector called KATRIN at Karlsruhe Institute of Technology in Germany. This should measure a neutrino mass as small as 0.2 eV/c2 – which could still leave a 20-fold uncertainty in its value. But KATRIN is the size of a building, and further improvements in measurement accuracy by this method would require an even larger, more expensive spectrometer.
Now, physicists at Pacific Northwest National Laboratory, National Radio Astronomy Observatory, University of California Santa Barbara, University of Washington, the Massachusetts Institute of Technology and Karlsruhe University have set up the Project 8 collaboration, which is taking a different and possibly more elegant approach to measuring neutrino mass. When an electron passes through a magnetic field, its path curves into a circular orbit, and this causes the electron to emit cyclotron radiation at microwave frequencies. The nature of this radiation is dependent on the energy of the electron, and therefore measuring this effect could provide a much more simple and precise technique of measuring the energy than is currently used at KATRIN. The challenge, however, is how to detect the extremely weak femtowatt signal of cyclotron radiation from a single electron.
Now, the Project 8 team has taken an important step in that direction by being the first to detect this cyclotron radiation. Its prototype tabletop apparatus is located at the University of Washington in Seattle, and it uses a centimetre-sized gas cell that is filled with krypton-83 – a gas that undergoes beta decay. In an actual neutrino-mass experiment, the krypton would be replaced with tritium, but this introduces additional technical and safety considerations that will be considered in the future. The cell is placed inside a superconducting coil to generate a magnetic field. Electrons emitted by the beta decay travel in very long circular paths inside the tiny cell, emitting cyclotron microwave radiation, which is then detected by cooled, ultralow-noise detectors.
Small and simple
The researchers measured the energy of single emitted electrons with an accuracy of 30 eV. While this is far too low to obtain a reliable calculation of the neutrino mass, the team is now working to optimize the device to improve its resolution. “The apparatus that we built was very, very small”, says team member Benjamin Monreal of the University of California, Santa Barbara, “And that made the electronics very simple. We’re now preparing the readout designs, the antenna designs, the amplifier designs and the software to try to scale up.”
Huber, who was not involved in the research, is impressed, “They have successfully completed the first, very crucial step,” he says. “From here on, careful engineering and scaling of the device should get them to a point where they can compete with KATRIN.” However, he says, “there are probably more physics experiments that have failed because of ‘mere engineering challenges’ than for any other reason”.
