Deep Freeze

November 07, 2008

[NOTE: Welcome to Part III of Neutrino Week at Twisted Physics! For a primer on the basics of neutrino physics, check out Part I and Part II.]

On Sunday, my pal David Saltzberg left the balmy sunshine of Los Angeles and flew to the freezing expanse of the South Pole to take up temporary residence at the Amundsen-Scott South Pole Station -- which basically serves as the scientific headquarters for a couple of major neutrino-centric experiments. A physics professor at UCLA, Saltzberg has garnered his 15 minutes of fame as technical consultant for the hit TV sitcom, The Big Bang Theory. But he is first and foremost an experimental particle physicist, part of a collaboration to build and deploy a neutrino detector dubbed ANITA (the ANtarctic Impulsive Transient Array).

This is actually the second run for ANITA, which first launched a few years ago. Both versions are designed to detect high energy neutrinos produced by collisions between cosmic rays and the photons that comprise the cosmic microwave background radiation that pervades the entire universe -- the glowing embers of the Big Bang, if you will. The detector -- basically an array of 36 radio antennas -- is suspended from a helium balloon, which will circle the frozen continent as it scans for the telltale radio pulses produced when these high-energy neutrinos collide with atoms in the Antarctic ice sheet.

Anyway, ANITA 1.0 didn't gather much useful data, due in part to bad weather. That's no reason to give up the fight! Now, after another year or two of planning, and a summer spent in Texas building the apparatus, ANITA 2.0 is finally go for launch.

Fingers crossed! With a bit of luck, they might uncover some exotic physics, since neutrino collisions at those high energies are capable of, say, producing micro-black holes -- at least in theory. Saltzberg's job is to find some experimental evidence to support the theory. (As with any micro-black holes produced by the Large Hadron Collider, these would evaporate almost instantaneously, identifiable only by their decay pattern "signatures.")

Saltzberg's team isn't the only one with a neutrino experiment deployed at the South Pole. ANITA is part of a larger collaboration called AMANDA (Antarctic Muon And Neutrino Detector Array). AMANDA is a telescope buried deep in the ice beneath the Amundsen-Scott station. Like ANITA, AMANDA is designed to detect higher energy neutrinos (specifically of the muon flavor), but it uses photomultiplier tubes to detect flashes of Cherenkov radiation rather than radio antennae. Occasionally, a neutrino will collide with the nuclei of oxygen or hydrogen atoms in the ice and produce a muon and a shower of hadrons, releasing the excess energy as radiation.  Here's a nifty video the AMANDA collaboration put together explaining the basic set-up and how it works:

Why do particle physicists need so many different kinds of neutrino detection experiments? Saltzberg explains that "every time we look at the universe in a new regime" -- radio waves, for example, or x-ray or infrared astronomy, in addition to optical techniques -- "we learn something new." Similarly, each variation on neutrino detection looks at the particles in a slightly different way: focusing on a particular flavor, for instance, or a specific energy regime. Ideally, by looking at neutrinos from every conceivable angle, physicists will gain a thorough understanding of the underlying physics of these elusive, complicated particles.

Case in point: The underground neutrino detectors -- the now-defunct SNO, as well as Japan's Super-Kamiokande detector -- have the advantage of controlled conditions, but are limited in terms of volume of target material (i.e., their real estate covers however much water or other fluid they can fit in a giant manmade tank). AMANDA might sacrifice a bit of that control and precision of measurement, but it can detect higher energy neutrinos from sources outside the solar system because it's not as limited in scope (the Antarctic ice sheet is way bigger than any manmade tank).

We're already on AMANDA 2.0, and since 2005 -- nine years after it began operation -- the project has been folded into its eventual successor: the IceCube Neutrino Observatory. (Let's give these folks some credit for coming up with catchy monikers.) Again, they are drilling holes in the ice using a hot water drill to deploy strings of sensors.

The installation is roughly half complete, expected to be done in 2011. The grand total: thousands of spherical optical sensors (photomultiplier tubes) deployed on strings of 60 modules each, making IceCube the single largest neutrino telescope in the world.

So Saltzberg is part of an exciting scientific adventure, which makes it worth freezing his derriere off in such frigid temperatures for six months or so. Not that he's suffering too much: The Wall Street Journal recently ran a fascinating article by Michele Gentille, a chef and freelance food writer, who spent a season as sous-chef at the Amundsen-Scott South Pole Station in 2007.

Sure, there were some challenges: fresh produce is non-existent; it can take 10 days for meat to thaw; and at that altitude (9300 feet above sea level), water takes longer to boil, so it can take several hours to heat up a big pot of soup. Nonetheless, Gentille is the resourceful type, and managed to replicate several gourmet recipes featured at Bistro Laurent Tourondel in New York. She even baked some yummy pies for Thanksgiving dinner. Saltzberg and his fellow Antarctic scientists might be cold, but at least they're eating well.

Photos: (top) The Amundsen-Scott South Pole Station. (bottom) Illustration of IceCube's detector array. Both courtesy of the IceCube collaboration's image gallery and the National Science Foundation.

Comments

[Freiddie]

"a fascinating article" - link broken?

[Brian Hodges]

I remember a friend, whose brother was apparently a scientist in Antarctica, telling me that when you go to Antarctica you eat better than any other time in your life. The rationale is that food is so expensive to ship in anyway, that it's very easy to justify the little bit extra to bring in REALLY REALLY good food. If a hamburger costs 50 bucks, to ship, whats an extra ten for filet mignon, right?

[Rosebud]

I thought that water boils faster at high altitude, but at a lower temperature, and that's why its hard to heat things up well, and you need to boil longer. Am I wrong about that?