The Majorana Demonstrator is being built at the Sanford Underground Research Facility in Lead, S.D. This detector is being built to search for Neutrionoless Double Beta Decay. This is a very rare form of radioactive decay. Black Hills State University students are helping to clean and prepare the lead bricks as part of the shield of the detector.
According to some theorists, Neutrinoless Double Beta Decay could explain the origin of mass.
According to Hall, normal Double Beta Decay happens when, two neutrons inside a nucleus change into two protons while discharging two neutrinos and two electrons. When Neutrinoless Double Beta Decay takes place, only the electrons would be visible because the two neutrinos would have been absorbed back into the atomic nucleus. This is because the neutrinos are electrically neutral, which means the neutrino and the anti-neutrino are basically identical.
The Majorana Demonstrator Project is located at the Davis Campus at SURF. This campus is located 4,850 feet below the surface of the Earth. The detector must be shielded from both cosmic rays above ground and other types of radiation below ground. For this they have several shields made out of different materials. The materials include plastic, lead and copper that is the purest in the world. They actually form the copper at the 4,850 level so that it never has the bombardment of cosmic rays as it would if it were formed on the surface and brought down.
“This copper is worth about $100 an ounce,” said Jaret Heise Science Director for SURF.
The lead part of the shield is what BHSU students and Dr. Kara Keeter have been helping with. Their job is to clean and repackage the lead bricks before they are taken underground and placed where they are needed to form the shield.
“In total the shield will require 5,200 lead bricks” said Heise.
The cleaning of the bricks takes place in Jonas Hall on the BHSU campus, in a clean room that has been set up and funded by Majorana.
“The process takes a little time and strength,” said Keeter.
The bricks are heavy and have to be cleaned under a fume hood. This working environment provides little room to lift and move the bricks. So far BHSU students have cleaned almost 4,000 lead bricks.
The dirty bricks arrive crated on a pallet. They are then removed from the pallet and pass through the plastic sheeting that acts as a door to the clean room. The next step is to place them under the fume hood into an acetic acid bath. The bricks are then rinsed in two separate deionized water baths. They then go into a nitric bath where they are scrubbed. Then they get another rinse in deionized water. After this step, the bricks are removed from the fume hood and placed in a final bath of deionized water. The bricks are then laid out on a table to dry. As they are drying they get sprayed with isprophal alcohol which then evaporates and helps to remove any leftover moisture in the bricks. The bricks are triple-bagged in plastic once they have completely dried. The plastic is sealed in a similar fashion to a food sealer, except the air is not vacuumed out. They are then crated back up on a pallet and are ready to head to SURF.
The bags are then removed one at a time as the bricks get into cleaner and cleaner areas in the underground research facility. This helps ensure the bricks are as clean as possible before they are put into final assembly.
In the spring of 2013 the cleaning facility was running 40 hours a week. They are not currently operating at this level right now but need workers. In order to help with this project, students need to have a dedicated time when they could work several hours at a time.
For more information on the Majorana Demonstrator Project visit SanfordLab.org. For more information on the brick cleaning work being done on the BHSU Campus contact Kara Keeter at [email protected]