Astrophysicist digs holes to chart the stars

Research at the South Pole may hold certain occupational hazards - freezing to death or finding vintage Yoo-Hoos in the galley - but it also offers the opportunity to discover if any neutrinos are ceaselessly bombarding the earth.

With a grant from the Penn Research Foundation, Doug Cowen, assistant professor of physics and astronomy, traveled south this past winter break to conduct research on neutrinos.

South Pole research has the typical delays of other projects, plus 30 hours of flying time, temperamental weather restrictions and extended periods between data collection.

Doug Cowen with a light-sensitive photo tube used in the South Pole AMANDA research project

Photo by Kim Weimer

Getting to the research site took as many days as the actual work. Bad weather at the Pole kept Cowen and his fellow researchers in sunny Christchurch, New Zealand, for five days, but it wasn't exactly a vacation. "Summer in New Zealand is a whole lot hotter if you're wearing a goose-down parka," Cowen said.

Neutrinos are potentially problem-solving subatomic particles. No one is sure whether they have mass or what their specific role is in the galaxy.

Cowen and his partners think that they can use them to chart astronomical events. "Neutrinos are a signature of the universe no one has been able to see before," Cowen said.

Unlike photons and protons, neutrinos might become valuable yardsticks of the universe because they do not bend as they travel.

Cowen's research is based at AMANDA (Antarctic Muon and Neutrino Detector Array), an array of photo-tubes strung onto cables and placed vertically, 1.5 miles deep into the polar ice cap. The strands detect neutrinos as they travel through the earth from their celestial sources. In theory, the AMANDA project will be able to plot the trajectory of speeding neutrinos as they cut through the field of buried photo tubes, providing a line to trace back the subatomic particles' trajectory from a cosmic happening.

Cowen and his colleagues look for neutrinos produced by two types of cosmic events.

Supermassive black holes, in the process of all their destroying, process and release a great magnitude of energy. Much of that is sucked back in, but neutrinos are possible escapees.

The other events are gamma-ray bursts coming from neutron stars that have collapsed into one another. "They accelerate particles as they do their death dance, giving off enough energy to outshine other galaxies-for brief seconds," Cowen said.

This was Cowen's first trip to the AMANDA site, but he's been involved with the project half of his five years at Penn. His on-site work consisted of installing a circuit that prevents the loss of data as it travels the 1,500 meters from the photo tubes to the surface.

"When the pulse travels up the cable it becomes distorted. For the data to get all the way to the top, you have to turn the 'volume knob' up all the way. With the new circuit, you can turn the volume down some and extend the life-span of the tubes."

The new circuit (designed by Penn's Mitch Newcomer and built by Godwin Mayers) will make it easier to clean up all the signals that hit the photo tubes and filter out the ones that will lead back to a specific place and time. "If you know the reaction of the tubes and if we have specific space to connect it to - now that would be something," Cowen said.

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Originally published on February 25, 1999