University of Wisconsin-Madison Physical Sciences Lab

LBNE: APA Cold Test

Wednesday, February 13th, 2013

PSL cleared a major hurdle in the Long Baseline Neutrino Experiment (LBNE) project when it cold tested the Anode Plane Array (APA). The LBNE project is going to shoot neutrino particles from a source at Fermilab to a detector located in Lead, SD. The detector will be comprised of a number of large panels, the APAs, that will be submerged in liquid argon, which has a temperature of -302 degrees Fahrenheit (87 degrees Kelvin).

Picture of the Anode Panel ArrayThe completed APA.

The APA prototype used for the cold test was a 40% scale version of the final panel. The APA was designed at Brookhaven National Lab, and it was constructed at PSL. The frame is made of stainless steel rectangular tubing, with thin strands of copper wire stretched over the top. The wire is then attached to a circuit board, to track neutrinos.

Picture of Daya Bay anti-neutrino detectorThe cryostat, with the liquid nitrogen dewars,being filled.

For the test, rather than using liquid argon, 778 liters (205 gallons) of liquid nitrogen were used. Since liquid argon was more difficult to source, nitrogen was used instead. Liquid nitrogen is actually colder than liquid argon, liquid nitrogen being -320 degrees Fahrenheit (77.3 degrees Kelvin). The APA was loaded into the cryostat, a large leak proof box that was constructed by Fermilab and extensively modified by PSL. Once the APA was in, the box was covered and liquid nitrogen filled the cryostat. When the cryostat was full, PSL Electrical Engineer Dan Wahl and Technician Andy Arbuckle tested the various detector circuits to make sure they were functional in the cold environment. All of the circuits worked, and the APA prototype test was a success.

Picture of Daya Bay anti-neutrino detectorThe APA after the test. Note all of the frost from the water that condensed on the very cold APA.