|
Phantom
Detectors
|
|
|
|
Photo:
John
Jacobsen
|
|
|
Hoses
carrying hot water melt their way into the ice. The hot
water is used to drill the deep columns into which the
optical sensors are placed.
|
|
|
|
Neutrino
detection is tricky business. The instrument must be big enough
to detect the rare neutrino interaction, transparent enough
to track a muon's path across a great distance, and far enough
below the Earth's surface to filter out interference from
irrelevant particles and light. As it turns out, the extraordinary
clarity of the deep Antarctic ice provides an ideal medium.
Buried nearly a mile and a half beneath the Polar ice cap,
AMANDA acts more like a telescope than a traditional particle
detector, collecting rather than creating particle debris.
But while most telescopes search the skies with optical lenses
and mirrors to capture celestial light, this one uses phototubes
in glass orbs to scrutinize the subterranean ice for the light
that heralds a neutrino's passing. Nearly seven hundred of
these glass detectors are placed throughout the ice, strung
on nineteen cables lowered deep into narrow columns of melted
ice, where they freeze in place. You can see how these parts
of the detector are set up in
a
variety of schematic diagrams of the detector
.
As neutrinos bombard the sunken detectors, a few interact
with subatomic particles in the ice and rock and create muons.
Essentially a heavy electron, the negatively charged muon
emits a faint blue light that illuminates the phototubes.
Acting like light bulbs in reverse, the phototubes collect
a muon's light and convert it into electrical signals, which
are sent to computers above the ice that store and process
the data. The signals announce the presence of a neutrino
arrival, as well as its rate, frequency, and path. Researchers
hope to trace the muon's path back to the neutrino's cosmic
origins.
To mine the full potential of the deep, clear Antarctic ice,
scientists plan to outfit AMANDA with as many as 50,000 orbs
on 80 cables over the next decade. As they push the limits
of engineering and endurance, researchers sense the discovery
of something truly monumental—though they're not sure
what. They'll just have to wait till the heavens send them
the clues.
To learn more about AMANDA:
AMANDA Web page:
http://amanda.berkeley.edu/amanda/amanda.html
The Center for Astrophysical Research in Antarctica:
http://astro.uchicago.edu/cara/home.html
|
