“Picture this in the jaws of a magnet,” says Wit Busza, a nuclear physicist at the Massachusetts Institute of Technology. “Look in here. This is where the particles went in.”
He pointed to the inside of a tiny tube covered in a tinier silicon grid, a crucial piece of the Phobos particle detector.
One of four detectors that made up Brookhaven’s Relativistic Heavy Ion Collider (RHIC), Phobos recorded the properties of a special substance known as quark-gluon plasma from 2000 to 2005. Physicists are only now sorting through the last of the small detector’s wealth of data.
Though particle physicists study the universe’s smallest inhabitants, their laboratories are often the realms of big machines, multiple-story detectors in seemingly endless underground tunnels. Phobos’ three main pieces, though, each can fit on a desk. Like model ships in bottles, they now sit in separate glass boxes on the fourth floor of MIT’s Building 24.
In 1989, Busza had imagined a much larger experiment. “It was called the Modular Array of RHIC Spectra, or MARS,” he says. “It got rejected. It was too expensive.” Back at the drawing board, he designed a smaller, cheaper detector: “A colleague of mine said that, since MARS was rejected, I should name this one after a moon of Mars.” In 1999, Brookhaven finished construction. Phobos was born.