The First Antihydrogen Beam
Posted by on Tuesday, January 28, 2014 Under: Particle Physics
Exciting new results have been announced by the ASACUSA Experiment at CERN today. The team has been reviewing data they collected in 2012 in the Antiproton Decelerator facility, and have confirmed that they had produced a beam of antihydrogen. If this holds up under peer review and academic scrutiny, it will be the first anti-matter beam of atoms ever produced by mankind.
In the late 1920s, work by Paul Dirac to understand relativistic quantum mechanics lead to an odd result - his equations predicted that for each particle of matter there would be a second particle with the same mass and opposite charge. At first he and other theorists didn't believe this, and spent a lot of time and effort to try to eliminate the second particle or to adjust its mass to fit other known particles. However when studies of cosmic rays lead Carl Anderson to announce in 1932 the experimental discovery of the positron, which had the same mass as an electron but opposite charge, it became clear the Dirac's formula had predicted the existence of antimatter.
Even now antimatter is mysterious. At present there are no confirmed processes which can generate or destroy antimatter without the same amount of matter being affected (however there are numerous theories to explain this, but all require new and unobserved physics to work). Some of the most fundamental symmetries of nature seem to require the they are produced together and must be destroyed together, and balance is always preserved. Except the known Universe is almost entirely matter, and no antimatter in large quantities has ever been observed.
Antimatter is also difficult to produce. While positrons (anti-electrons) are now known to be generated in some radioactive decays, and can be produce relatively easily at small particle accelerators, anti-protons still require much larger and more expensive facilities due to the need to generate at least 2 GeV of energy in a single reaction. And worse yet, any antimatter that is produced immediately annihilates with ordinary matter, making it difficult to contain and observe. As such the larger particle colliders can and do generate beams of antiprotons, but they are not in atomic form.
What the ASACUSA team is claiming is that they have managed to keep positrons in orbit around antiprotons in sufficient quantities to maintain a beam of antihyrdrogen. They did this by first taking a beam of antiprotons, and cooling them down to very low temperatures. They then combined the antiprotons with positrons inside of a magnetic field that was designed to hold them away from any ordinary matter. This allowed the two species of particles to bind together, with the positrons orbiting the antiprotons, forming a total of 80 atoms of antihydrogen.
Since antihydrogen cannot be studied and examined inside the magnetic field, the anti-atoms are ejected in a beam (using another magnetic field), and directed into other experiments that aim to determine the properties of antimatter in greater detail. In this way, scientists hope to determine whether or not antimatter and matter are identical, or whether some interesting new physics causes a very slight asymmetry between them.
Next ASACUSA is going to restart their experiment (it was turned off about a year ago) and begin the next step, which is to measure the hyperfine structure of anti-hydrogen. But that is another story...
In the late 1920s, work by Paul Dirac to understand relativistic quantum mechanics lead to an odd result - his equations predicted that for each particle of matter there would be a second particle with the same mass and opposite charge. At first he and other theorists didn't believe this, and spent a lot of time and effort to try to eliminate the second particle or to adjust its mass to fit other known particles. However when studies of cosmic rays lead Carl Anderson to announce in 1932 the experimental discovery of the positron, which had the same mass as an electron but opposite charge, it became clear the Dirac's formula had predicted the existence of antimatter.
Even now antimatter is mysterious. At present there are no confirmed processes which can generate or destroy antimatter without the same amount of matter being affected (however there are numerous theories to explain this, but all require new and unobserved physics to work). Some of the most fundamental symmetries of nature seem to require the they are produced together and must be destroyed together, and balance is always preserved. Except the known Universe is almost entirely matter, and no antimatter in large quantities has ever been observed.
Antimatter is also difficult to produce. While positrons (anti-electrons) are now known to be generated in some radioactive decays, and can be produce relatively easily at small particle accelerators, anti-protons still require much larger and more expensive facilities due to the need to generate at least 2 GeV of energy in a single reaction. And worse yet, any antimatter that is produced immediately annihilates with ordinary matter, making it difficult to contain and observe. As such the larger particle colliders can and do generate beams of antiprotons, but they are not in atomic form.
What the ASACUSA team is claiming is that they have managed to keep positrons in orbit around antiprotons in sufficient quantities to maintain a beam of antihyrdrogen. They did this by first taking a beam of antiprotons, and cooling them down to very low temperatures. They then combined the antiprotons with positrons inside of a magnetic field that was designed to hold them away from any ordinary matter. This allowed the two species of particles to bind together, with the positrons orbiting the antiprotons, forming a total of 80 atoms of antihydrogen.
Since antihydrogen cannot be studied and examined inside the magnetic field, the anti-atoms are ejected in a beam (using another magnetic field), and directed into other experiments that aim to determine the properties of antimatter in greater detail. In this way, scientists hope to determine whether or not antimatter and matter are identical, or whether some interesting new physics causes a very slight asymmetry between them.
Next ASACUSA is going to restart their experiment (it was turned off about a year ago) and begin the next step, which is to measure the hyperfine structure of anti-hydrogen. But that is another story...
In : Particle Physics
I am a theoretical physicist & mathematician, with training in electronics, programming, robotics, and a number of other related fields.
