March 8, 2012
Microwaves Used In First Time Measurement Of Antimatter Atom
An international team of physicists at CERN (the European Laboratory for Particle Physics) used microwaves to measure and manipulate an atom made of antimatter for the first time ever.
While imprecise, the measurement represents an important first step in being able to study antimatter atoms in detail -- a critical part of understanding why the universe is made of matter and not antimatter.
"This is the first time that anyone has ever interacted with an antimatter atom," said lead author Mike Hayden, a physicist with Simon Fraser University and a member of CERN's ALPHA collaboration.
"For decades, scientists have wanted to study the intrinsic properties of antimatter atoms in the hope of finding clues that might help answer fundamental questions about our universe," he said.
"In the middle of the last century, physicists were developing and using microwave techniques to study ordinary atoms like hydrogen. Now, 60 or 70 years down the road, we've just witnessed the first-ever microwave interactions with an anti-atom."
The ALPHA team's work has focused on the stable trapping of antihydrogen atoms, the antimatter counterpart of the simplest atom, hydrogen. The hydrogen atom — the most plentiful in the universe -- is so simple that some of the most fundamental physical constants have been discovered by measuring the tiny energy shifts triggered by the magnetic and electric interactions of hydrogen´s proton nucleus with its single orbiting electron.
Antihydrogen, on the other hand, is rare, with single positrons (antielectrons) orbiting single antiprotons. It is difficult to make, and even more difficult to measure and manipulate. Indeed, antihydrogen had never even been trapped until ALPHA succeeded in doing so in 2010.
Such antimatter stands out as one of the biggest mysteries of science. Fundamental theories predict perfect symmetry between matter and antimatter, but the glaring absence of antimatter in our universe suggests there might be a difference.
Enter microwave spectroscopy, one of the most sensitive techniques for probing the structure of atoms.
The current work involved confining anti-atoms in a magnetic trap and irradiating them with microwaves. Precise tuning of the microwave frequency and magnetic field enabled researchers to hit an internal resonance, kicking atoms out of the trap and revealing information about their properties.
"This study demonstrates the feasibility of applying microwave spectroscopy to fiendishly difficult-to-handle anti-atoms," said co-author Walter Hardy, a renowned expert on microwave spectroscopy from University of British Columbia.
"ALPHA is about to enter an intensive upgrade phase that promises to create an ever-clearer picture of the inner structure of anti-matter atoms."
The work is published online March 7 in the journal Nature.
Image Caption: Electrodes for the ALPHA Penning trap are inserted into the vacuum chamber and cryostat assembly. Positrons and antiprotons combine in the trap to form antihydrogen (Image: Niels Madsen ALPHA/Swansea)
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