Scientists reenter Soudan Underground Laboratory

This photo, taken in 2004, shows the CDMS experiment in the Soudan Underground Laboratory.

Ten days after a mine access shaft fire shut down the Soudan Underground Laboratory, the first scientists returned to the laboratory as electricians began to restore power to the laboratory. It was the first time that lights in the laboratory were back on since March 17, when a fire protection system shut down the power to the entire laboratory because of a fire in the access shaft (see Fermilab Today article on March 21, 2011).

“I’m grateful to the Minnesota Department of Natural Resources and the laboratory staff for getting us to this point,” said Marvin Marshak, director of the underground laboratory, which is managed by the University of Minnesota; the mine is owned and operated by the Minnesota DNR. “Now that we have some power, we can make progress on returning the experiments to their normal operating conditions.”

The laboratory so far only receives limited power since crews still need to test the electrical system and replace a backup power cable. In the next couple of days, scientists will carry out a thorough investigation of the status of the two major experiments in the laboratory: the detector of the MINOS neutrino experiment and the detector of the Cryogenic Dark Matter Search experiment. The MINOS hall was still without power on Monday.

Last week, the DNR reported that some fire-extinguishing foam had entered the caverns of the MINOS and CDMS experiments. Yesterday, Dan Bauer, Fermilab Operations Manager for experiments at Soudan, entered the laboratory and found “a basically foam free environment” since the foam had collapsed. The parts of the cavern floors that are close to the access shaft showed signs of a sticky residue from the foam, which needs to be cleaned up.

CDMS scientists have begun to assess the status of their experiment’s cryogenic system, which cools ultra-sensitive particle detectors to less than one Kelvin, close to absolute zero temperature. The experiment has warmed to room temperature without losing vacuum, which gives hope that the cryogenics system was undamaged by the long power outage. Fermilab Today will provide an update when more information is available.

– Kurt Riesselmann