Kamis, 05 Mei 2011
CERN scientists confine antihydrogen atoms for 1000 seconds
(a) A schematic view of the ALPHA trap. Penning trap electrodes are held at ~9 K, and have an inner diameter of 44.5 mm. A three-layer silicon vertex detector surrounds the magnets and the cryostat. A 1 T base field is provided by an external solenoid (not shown). An antiproton beam is introduced from the right, while positrons from an accumulator are brought in from the left. (b) The magnetic field strength in the y-z plane (z is along the trap axis, with z=0 at the centre of the magnetic trap). Green dashed lines in this and other figures depict the location of the inner walls of the electrodes. (c) The axial field profile, with an effective trap length of ~270 mm. (d) The field strength in the x-y plane. (e) The field strength profile along the x-axis. Image credit: ArXiv paper (see ref. below)
Seventeen minutes may not seem like much, but to physicists working on the Antihydrogen Laser Physics Apparatus (ALPHA) project at the CERN physics complex near Geneva, 1000 seconds is nearly four orders of magnitude better than has ever been achieved before in capturing and holding onto antimatter atoms. In a paper published in arXiv, a team of researchers studying the properties of antimatter, describe a process whereby they were able to confine antihydrogen atoms for just that long, paving the way for new experiments that could demonstrate properties of antimatter that until now, have been largely speculation.
The process works by cooling the antiprotons that when combined with positrons, are used to make the antihydrogen, which reduces the energy in the resulting antimatter and allows for more of it to be confined in a magnetic trap, and then held there in a cloud for a period of time.
One of the big questions in physics is whether antihydrogen atoms occupy the same energy levels as hydrogen; others of course want to know how it reacts to gravity, as some have speculated that antihydrogen might actually fall up, or behave in other unexpected ways. The experiments going on at CERN might just answer both those questions, and more.
The idea of the specialness of antimatter has become a fixture of modern science fiction books, magazines and especially television and movies, creating in the public mind an oftentimes distorted image of what harnessing antimatter might bring. Thus, any new advances such as those happening at CERN tend to incite headlines that invite even more speculation.
At any rate, in the experiment, the researchers were able to trap 309 antihydrogen atoms, up from the previous best of just 38, which means the team is learning to both capture more of them and to hold on to them longer before collisions with various trace gasses causes them to be annihilated, or in some cases to become energized enough to escape the magnetic field.
Up next for the ALPHA team are plans to cool a small bunch of antihydrogen atoms in such a way as to allow them to watch as it either rises or falls due to gravity, thus answering one of the more exciting questions regarding antimatter, in perhaps just the next few months.