The average summertime temperature is 35 degrees below zero. There is always a northern wind blowing about 15 mph. When storms rage, they do so with wind speeds of 100 mph, driving snow and ice for miles.

These are the conditions under which several members of the College's Bartol Research Institute regularly visit the South Pole to study atmospheric radiation.

On the most recent expedition, from Nov. 15 to Jan. 15, UD researchers Xinhua Bai, Serap Tilav and Gerald Poirier were joined by high school teachers Jason Petula and Matts Pettersson. The group was responsible for collecting and analyzing data, maintaining equipment worth millions of dollars and assembling a protocol for the future study of atmospheric radiation.

One of the key aspects of the scientists' study lay a mile below the snow on which they walked. The Antarctic Muon and Neutrino Detector Array, known as AMANDA, consists of multiple phototubes inserted into holes drilled deep into the Earth. They are placed at such a depth as to eliminate particles from the atmosphere, which often act like static on a radio station.

Once locked away under a mile of ice and snow, AMANDA works like "a backwards light bulb," according to Thomas Gaisser, Martin A. Pomerantz Chair of Physics and Astronomy and the principal investigator for the project.

The sensors of AMANDA collect radiation that has been emitted by cosmic rays and has traveled through the center of the Earth. Gaisser says the rays "produce an optical shockwave, like a sound wave or a wave in water"--much like a sonic boom, but with light.

A second tool used by the researchers is the South Pole Air Shower Experiment, or SPASE, which is used to detect the same particles AMANDA does, only above ground. Because of the rarity of these high-energy particles--there is usually one in an area the size of a football field during the span of a minute--numerous sensors are laid over 15,000 square meters.

The South Pole is an ideal location for SPASE because of the high altitude, which also works to eliminate unimportant radiation that causes confusion in data. Due to the otherwise undesirable climate, moisture is instantly frozen, eliminating clouds. This cloud-free sky allows the particles studied by SPASE to move into the atmosphere without restraint.

A newly approved project, known as ICECUBE, underwent preliminary engineering testing, with Poirier at the helm. Poirier, who has been with the project since 1992 and built the modules used in AMANDA, had to install a tank of water and make it freeze clear in order to prevent a distorted reading by instruments that would be placed into the tank.

This is no simple task, because once water begins to freeze, it expands as much as 10 percent. However, the tanks could not be sealed from the snow and ice often carried by the wind without creating bubbles. Instead, Poirier developed a method that froze the water from the outside in. The center of the tank, which had to remain above freezing, slowly pushed up all remaining air from the water.

The annual trip provides an opportunity to visit the South Pole for more than just Bartol scientists. Each year, there is an opening for two Girl Scouts or Boy Scouts to tour the facilities. On the latest trip, none was able to attend, but members of Chesapeake Bay Girl Scout Troop 315 used e-mail to send a barrage of questions to the pole, which the scientists answered electronically.

Graduate students also are encouraged to make the voyage. "I see the need for graduate students involved in the immediate and long-term future," Poirier says. "This is a big project."

--Kaytie Dowling, AS 2004