In its recent annual review, the Majorana Demonstrator (MJD) received high marks from Department of Energy and National Science Foundation officers and an international review committee.
?They recognized that we?ve made tremendous progress and are doing very well over all,? said John Wilkerson, principal investigator of MJD and the John R. and Louise S. Parker Distinguished Professor in the Department of Physics and Astronomy at the University of North Carolina. ?They offered us some constructive criticism that we will incorporate as we build the demonstrator.?
In their search for a rare form of radioactive decay, MJD researchers have been assembling natural germanium detectors into ?strings? inside a clean room on the 4850L. These strings were installed and tested in a prototype cryostat nearly identical to the ultra-clean cryostats that will be used in Majorana.
?The idea in building the prototype is to help us get ready to build the actual module,? Wilkerson said.
Researchers are building the experiment underground to eliminate the ?noise? from cosmic rays. But there is also radiation in the rocks, equipment, specks of dust and people. To filter out the additional radiation, the germanium detectors will be placed in cryostats made of ultra-pure copper that will be placed inside a copper shield and surrounded by a lead igloo. Each cryostat will contain seven strings of four detectors.
While building the module, the team of more than 100 researchers faced some real challenges. ?We are working with ideas that haven?t been tried before, including connecting cables as thick as a single hair inside a glove box wearing four pairs of gloves,? Wilkerson said. ?It?s a very complex task.?
The team learned that infrared (IR) heat was getting in, affecting the operation of the detectors. ?We did some improvements on the IR shielding in the last month and resolved the issue,? he said.
The collaboration expects to start building strings with enriched 76Ge detectors in April or May, Wilkerson said. If all continues to go well, they will begin collecting data later this year. He praised Sanford Lab for its support. ?The people here are key to our success.?
Wilkerson also praised members of the collaboration for their efforts to see the project through. ?We are in a fantastic phase right now,? he said. ?And we?re having fun seeing the work of the last few years come to fruition.?