CERN Physicists Trap and Observe Antimatter For a Record-Breaking Quarter Hour

Question one: When it falls, will it fall down? Or up?
ALPHA's antimatter trap
The trap where it happens N. MADSEN, ALPHA/SWANSEA via Nature

Scientists working on the Antihydrogen Laser Physics Apparatus (ALPHA) at Cern’s particle physics laboratory had very exciting quarter hour recently. The team conjured and contained atoms of antihydrogen for a full 1,000 seconds–that’s nearly 17 minutes and 10,000 times longer than they were previously able to keep antimatter around before it disappeared in burst of particle-on-particle annihilations.

Antihydrogen is the antiparticle to hydrogen (but you might have guessed that), and is of interest to researchers because, basically, we don’t know a whole lot about antihydrogen specifically and antimatter generally. That’s because it’s notoriously difficult to study. Put antihydrogen and hydrogen in contact and you end up with nothing. The two will annihilate each other, essentially canceling each other out.

To keep antimatter and matter separate, the ALPHA team has been experimenting with magnetic antimatter traps that allow them to keep a cloud of anti-particles in existence for very short periods of time. The team had to open their trap after just 170 milliseconds during experiments last year, a period long enough to verify that it had actually created antimatter but not long enough to actually study it.

This time, it kept its antihydrogen cloud intact for more than 16 minutes by lowering the temperature of the antiprotons used to create the hydrogen much further, which lowered the overall energy inside their magnetic jar. The breakthrough should allow researchers to actually experiment on antihydrogen in coming years, helping them to answer some fundamental questions.

For instance, it’s unknown whether gravity affects antimatter in the same way as it affects normal matter. That is, scientists don’t even know if antimatter falls up or falls down. Having containers of the stuff to observe will naturally help scientists probe these unknowns.

[New Scientist, Technology Review]