Despite first being described over three centuries ago, gravity remains one of the least understood of the fundamental forces. At CERN’s recently completed AEgIS experiment, a team is setting out to examine its effects on something much less familiar: antimatter.
Located in the experimental hall at the Antiproton Decelerator (AD), the AEgIS experiment is designed to make the first direct measurement of Earth’s gravitational effect on antimatter. By sending a beam of antihydrogen atoms through very thin gratings, the experiment will be able to measure how far the antihydrogen atoms fall and in how much time – giving the AEgIS team a measurement of the gravitational coupling. The team finished putting all of the elements of the experiment together by the end of 2012, but they will have to wait for two years for beams to return to the AD hall following the Long Shutdown (LS1), which has just begun.
To make progress in the meantime, the AEgIS team has decided to try out the experiment with hydrogen instead of antihydrogen. By replacing antiprotons with their own proton source, the team will be able to manufacture its own hydrogen beam to use for commissioning and testing the set-up. Surprisingly, carrying out the experiment with hydrogen will be more difficult technically than with antihydrogen. Another challenge will be in the production of the positronium that will be used in creating the hydrogen. The positronium needs to be moving fast enough to ensure that it does not decay before it meets the protons/antiprotons, but not so fast as to pass the protons/antiprotons altogether. The AEgIS team will be carrying out this commissioning during the coming months, opening up their set-up next month to make any necessary adjustments and to install a hydrogen detector and proton source.
• For more, see the article in CERN Bulletin.
