Researchers have completed an inspection of damage at the underground physics lab closed due to fire on March 17, says the lab’s director. The Soudan Underground Laboratory of the University of Minnesota was shut down for ten days after fire broke out in the timbers lining an elevator shaft that serves the lab site, located on level 27 of the mine, which is 710 metres underground (the underground location shields out cosmic rays that would act as a source of background noise for experiments in the lab). After going back in for the first time yesterday, lab staff found some damage from firefighting foam forced down the shaft that burst open the doors to the lab, and are reckoning with a need for substantial clean-up to remove debris from the fire that was brought in, says lab director Marvin Marshak. “The good news is that there seems very little damage to any of the experiments in the lab,” he says. One exception was some waterlogging of wires used to magnetize the Main Injector Neutrino Oscillation Search (MINOS) detector, which detects neutrinos beamed from Fermilab in Batavia, Illinois. They will need to be dried out before the detector can be remagnetized. “The fire was unfortunate. However, the alarm systems worked as designed,” Marshak says.
Other experiments at the lab include the Cryogenic Dark Matter Search (CDMS), which was undamaged, and the Coherent Germanium Neutrino Technology (CoGeNT), both of which look for evidence of dark matter particles passing through the Earth. Juan Collar of the University of Chicago and CoGeNT says the unexpected shutdown interrupted a 15 month search for a modulation in the flow of WIMPS, expected to change with the seasons as the Earth moves in its orbit. He doesn’t know when the detector, which needs to be cryogenically cooled and which warmed up when power was cut to the lab, will be back to normal. “It is pretty bad for us,” he says, “ideally we would have liked to look at at least two years of modulation data.”
The state concluded that the fire was accidental, probably caused by sparks produced by maintenance work in the elevator shaft around level 25.
Update: This blog was updated on April 4th, to include information about the probable cause of the fire.
Image credit: Lab welcome sign, MINOS Collaboration