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Tabletop accelerator shoots cheap antimatter bullets
THIS WEEK
Antimatter bullets get fast and cheap MAKE way for the antimatter gun. A tabletop device just 10 square metres in size can spit out energetic bursts of positrons as dense as those kicked out by the giant particle-factories at CERN. Each positron-packed bullet lasts for just a fraction of a second, so don’t expect to fill the tank of your antimatter engine any time soon. Instead, the smaller, cheaper machine might help labs around the world study deep-space objects such as powerful radiation jets squirted out by black holes. Antiparticles have the same mass as their ordinary particle counterparts but carry an opposite charge and spin. The particles annihilate on contact with ordinary matter, vanishing in a puff of energy, which makes it difficult to produce and study them on Earth. Huge machines at particle physics labs, such as CERN near Geneva, Switzerland, have been churning out antimatter for over a decade. But it is an expensive pursuit that, for CERN, requires a 190-metre-long track. Instead, Gianluca Sarri at
Want fewer hurricanes? Pollute the air CLEANING up the air in the West may have made us healthier, but it could also be responsible for an increase in North Atlantic tropical storms. A new analysis shows that the number of storms falls as pollution rises, and rises when pollution drops. Tighter pollution controls “could reduce aerosols so quickly that we’ll have record numbers of tropical 10 | NewScientist | 29 June 2013
Queen’s University Belfast, UK, and colleagues used rapid laser bursts to make positrons in their smaller, budget device. The laser pulse ionises inert helium gas, generating a stream of high-speed electrons. This electron beam is directed at a thin metallic foil so that it crashes into metal atoms, releasing a jet of electrons and positrons. These particles are
laser at a tiny gold disc. Sarri says his set-up is much more practical and cheaper: “They needed much stronger lasers, and those lasers are expensive.” Also, they produced streams of positrons that were extremely broad, “whereas our jet is a hundred times narrower and remains pencil-like as it propagates,” he adds. “This is similar to the powerful streams of matterantimatter observed outside pulsars and black holes.” CERN physicist Niels Madsen notes, though, that the tabletop device has limitations. It only makes relatively light particles like positrons, whereas to make an anti-atom you also need antiprotons, which are almost 2000 times more massive. For now, he says, making heavier antiparticles “is not doable in a small lab in a cheap fashion”. Nor does the smaller machine address the problem of antimatter storage. To hold antimatter stable it must be chilled, and the tabletop method makes searinghot beams of particles moving at near light speed. As an alternative, says Sarri, the beams can be used to mimic the way particle fountains from black holes and pulsars shoot through and interact with gases in the interstellar medium, creating mini versions of these enigmatic astrophysical phenomena in the –Cosmic antimatter factory– lab for the first time. n CXC/ASU/J. Hester et al, HST/NASA
Katia Moskvitch
separated into two beams with magnets (Physical Review Letters, doi.org/m2n). The team call their device an antimatter gun because the bursts of positrons last just 30 femtoseconds (quadrillionths of a second). Despite their short duration, the beams contain a quadrillion positrons per cubic centimetre, says Sarri, meaning they are comparable in density to the ones made at CERN. In 2008 scientists at the Lawrence Livermore National Laboratory in California produced large quantities of antimatter by directing an extremely powerful
storms for the next decade or two”, says Nick Dunstone of the Met Office Hadley Centre in Exeter, UK. Aerosols cool Earth’s surface by scattering light, which does not affect storms. But aerosols also increase the brightness and lifetime of low-level marine clouds. When Dunstone added this to his climate models, the simulated clouds cooled the surface more than expected. A cooler North Atlantic has less energy to power hurricanes, and such cooling also boosts wind shear in the storm nursery, ripping up nascent hurricanes (Nature Geoscience, doi.org/m2z).
In the 20th century, aerosol emissions increased during industrialisation and decreased with economic slumps. Tropical storms were frequent from the 1930s through to the 1950s, but rarer in the better economic times of the 1960s to mid-1990s. Then pollution controls in the West cut aerosol levels, and hurricanes came roaring back. Dunstone expects the increase to
“Tighter pollution controls could cause record numbers of tropical storms for the next decade or two”
continue for two decades. After that, global warming may make storms less common, by warming the air and thereby reducing the all-important temperature difference between the sea and the air. Aerosols do seem to affect storm frequency, agrees Gabriel Vecchi of the NOAA Geophysical Fluid Dynamics Laboratory in Princeton, New Jersey. “Where our results disagree is the magnitude of the effect.” Dunstone says aerosols can account for all the variation in frequency, while Vecchi says global warming and natural cycles also have major effects. Jeff Hecht n
Antimatter bullets get fast and cheap MAKE way for the antimatter gun. A tabletop device just 10 square metres in size can spit out energetic bursts of positrons as dense as those kicked out by the giant particle-factories at CERN. Each positron-packed bullet lasts for just a fraction of a second, so don’t expect to fill the tank of your antimatter engine any time soon. Instead, the smaller, cheaper machine might help labs around the world study deep-space objects such as powerful radiation jets squirted out by black holes. Antiparticles have the same mass as their ordinary particle counterparts but carry an opposite charge and spin. The particles annihilate on contact with ordinary matter, vanishing in a puff of energy, which makes it difficult to produce and study them on Earth. Huge machines at particle physics labs, such as CERN near Geneva, Switzerland, have been churning out antimatter for over a decade. But it is an expensive pursuit that, for CERN, requires a 190-metre-long track. Instead, Gianluca Sarri at
Want fewer hurricanes? Pollute the air CLEANING up the air in the West may have made us healthier, but it could also be responsible for an increase in North Atlantic tropical storms. A new analysis shows that the number of storms falls as pollution rises, and rises when pollution drops. Tighter pollution controls “could reduce aerosols so quickly that we’ll have record numbers of tropical 10 | NewScientist | 29 June 2013
Queen’s University Belfast, UK, and colleagues used rapid laser bursts to make positrons in their smaller, budget device. The laser pulse ionises inert helium gas, generating a stream of high-speed electrons. This electron beam is directed at a thin metallic foil so that it crashes into metal atoms, releasing a jet of electrons and positrons. These particles are
laser at a tiny gold disc. Sarri says his set-up is much more practical and cheaper: “They needed much stronger lasers, and those lasers are expensive.” Also, they produced streams of positrons that were extremely broad, “whereas our jet is a hundred times narrower and remains pencil-like as it propagates,” he adds. “This is similar to the powerful streams of matterantimatter observed outside pulsars and black holes.” CERN physicist Niels Madsen notes, though, that the tabletop device has limitations. It only makes relatively light particles like positrons, whereas to make an anti-atom you also need antiprotons, which are almost 2000 times more massive. For now, he says, making heavier antiparticles “is not doable in a small lab in a cheap fashion”. Nor does the smaller machine address the problem of antimatter storage. To hold antimatter stable it must be chilled, and the tabletop method makes searinghot beams of particles moving at near light speed. As an alternative, says Sarri, the beams can be used to mimic the way particle fountains from black holes and pulsars shoot through and interact with gases in the interstellar medium, creating mini versions of these enigmatic astrophysical phenomena in the –Cosmic antimatter factory– lab for the first time. n CXC/ASU/J. Hester et al, HST/NASA
Katia Moskvitch
separated into two beams with magnets (Physical Review Letters, doi.org/m2n). The team call their device an antimatter gun because the bursts of positrons last just 30 femtoseconds (quadrillionths of a second). Despite their short duration, the beams contain a quadrillion positrons per cubic centimetre, says Sarri, meaning they are comparable in density to the ones made at CERN. In 2008 scientists at the Lawrence Livermore National Laboratory in California produced large quantities of antimatter by directing an extremely powerful
storms for the next decade or two”, says Nick Dunstone of the Met Office Hadley Centre in Exeter, UK. Aerosols cool Earth’s surface by scattering light, which does not affect storms. But aerosols also increase the brightness and lifetime of low-level marine clouds. When Dunstone added this to his climate models, the simulated clouds cooled the surface more than expected. A cooler North Atlantic has less energy to power hurricanes, and such cooling also boosts wind shear in the storm nursery, ripping up nascent hurricanes (Nature Geoscience, doi.org/m2z).
In the 20th century, aerosol emissions increased during industrialisation and decreased with economic slumps. Tropical storms were frequent from the 1930s through to the 1950s, but rarer in the better economic times of the 1960s to mid-1990s. Then pollution controls in the West cut aerosol levels, and hurricanes came roaring back. Dunstone expects the increase to
“Tighter pollution controls could cause record numbers of tropical storms for the next decade or two”
continue for two decades. After that, global warming may make storms less common, by warming the air and thereby reducing the all-important temperature difference between the sea and the air. Aerosols do seem to affect storm frequency, agrees Gabriel Vecchi of the NOAA Geophysical Fluid Dynamics Laboratory in Princeton, New Jersey. “Where our results disagree is the magnitude of the effect.” Dunstone says aerosols can account for all the variation in frequency, while Vecchi says global warming and natural cycles also have major effects. Jeff Hecht n