This story first appeared in Fermilab Today on September 18, 2009.
Bob Barger makes adjustments inside the COUPP experiment's tank, which contains a prototype detector that will eventually search for dark matter.
Scientists from the Chicagoland Observatory for Underground Particle Physics, or COUPP, experiment began filling Wednesday a prototype detector that they hope will eventually join other experiments in the search for dark matter.
The prototype is a larger version in a series of detectors that scientists began testing four years ago. The first in the series held one liter of target fluid, the next was two liters and this one is 30 liters.
The eventual goal is to deploy the new detector underground to join the worldwide search for dark matter by detecting weakly interacting massive particles, or WIMPs, which are one of the top candidates for dark matter. Before that happens, however, scientists want to monitor the device above ground for software glitches, image quality, and potential engineering problems, a process that began Wednesday.
“We’d like to make sure it works before we move it underground,” said Fermilab's Andrew Sonnenschein, project manager for COUPP. “We’re trying to minimize the risks for when it is far away and inaccessible.”
At 3 p.m., the COUPP project team began adjusting a series of valves that would allow a liquid called iodotriflouromethane, or CF3I, to trickle into the transparent quartz jar that resembles a large test tube. CF3I is commonly used as a fire suppressant.
When a WIMP interacts with an atom in the pressurized and superheated CF3I liquid, the particle will trigger a small expanding bubble. The moment the experiment detects a bubble larger than 1 millimeter, the detector records a one-second video of the bubble.
Scientists will test the real chamber, which is made of higher-grade quartz, in the NuMI tunnel about 1000 feet underground at Fermilab this winter, said Russ Rucinski, project engineer for COUPP. The higher-grade quartz will cut background interference.
COUPP scientists plan to eventually install the detector and other equipment more than a mile underground at SNOLAB in Sudbury, Ontario, in 2010. With the large detector shielded from cosmic rays deep underground and with a greater sensitivity than the one-liter prototype, scientists hope to extract a clear signal of WIMPs.
by Chris Knight
