"The hope is to find out something new. Something really unexpected, because it calls for a redefinition of your ideas and the basics of physics," said Roberto Battiston, a physicist at Italy's University of Perugia and deputy spokesperson for the AMS.
AMS was originally scheduled to launch in 2005, but after the 2003 Columbia space shuttle disaster, NASA drastically cut nonessential space shuttle missions like the one that would have carried the AMS.
Then, after finally earning a spot for the AMS on a July 2010 space shuttle launch, principal investigator Sam Ting decided to replace the device's electromagnet.
The cryogenic superconducting magnet had enough coolant to last for three years, said Ting, AMS spokesperson and physicist at MIT and CERN.
"After three years, we could have refueled the helium, but then they decided not to fly the shuttle anymore," he said.
The space station itself is expected to run until 2020 or even 2028. With its new, weaker magnet, which doesn't require coolant, the AMS is expected to run indefinitely—or until the space station itself comes down.
It took just a few months to replace the magnet, but the decision was "agonizing," since it would mean postponing the AMS's launch, according to the University of Perugia's Battiston.
In retrospect, he said, "it was a very wise choice."