Rochester, NY
17 April 2014
 
    Photo: NASA

    Space. All those stars and shit. What holds it all together?

    The generally-assumed answer is gravity, and that is true, but physicists know there is more to the answer. Many a simulation has been run using the properties we understand gravity to have and enough matter to create, say, a small galaxy. And the numbers never really add up: every time, scientists find their virtual galaxies spinning off into ether, rather than curling into the elegant spirals and clusters we’re so accustomed to seeing. Why is that?

    The answer, as inferred by scientists, is a type of matter called “dark matter.” Dark matter neither emits nor radiates light and is electrically neutral, and is thus far undetectable by any instruments science has developed. “Dark,” get it? But when dark matter is added into the boffin’s equation for a working galaxy, lo and behold, the galaxy stays together the way we expect it to.

    So now science has a pretty good idea that there’s something out there that we can’t detect. Now how do we detect it?

    Engineers from the University of Rochester are helping to try to answer just that question in South Dakota. In a project called the¬†Large Underground Xenon experiment, or LUX, the team led by Dr.¬†Frank Wolfs has installed “trigger” mechanisms that make the determination whether data coming to the instrument is worthy of further study, or is simply noise.

    The LUX experiment is an exercise in super-tightly controlled recording. The LUX is shielded from most distracting inputs by a 70,000 gallon pool of water, buried 4,850 feet below the surface of the Earth. Setting the LUX up in this way keeps it from getting confused by solar and ambient radiation. Additionally, the whole system is surrounded by super-sensitive photomultiplier tubes (PMTs) capable of detecting and filtering out even a single photon. All things must remain silent if they’re to find the one signal that proves the existence of the illusive dark matter particle.

    Inside the detector, xenon gas cooled to -160 degrees Fahrenheit is monitored by still more PMTs. These tubes will look for the small flashes of light that will hypothetically be produced when a dark matter particle (Weakly Interacting Massive Particle, or WIMP) collides with a xenon atom. A second, stronger flash is caused when a strong magnetic field inside the detector draws the electrons released in the collision upward towards another layer of gaseous xeon.

    It is in comparing these two flashes that the University of Rochester’s engineering team comes in. Their trigger must determine whether or not there were two flashes and whether the two flashes are related before passing that data on to researchers.

    So if the LUX works out and the mystery particle that makes up 82% of our universe’s mass is laid bare, it will be the U of R that will actually hand the data off. Bitchin.

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