More than 40 Majorana Demonstrator researchers met at the Sanford Lab last week, for four days, to assess progress and refine schedules for the experiment?s many paths forward. ?Every single path has made notable progress,? said Majorana Principal Investigator John Wilkerson, who is a physicist at the University of North Carolina.
Majorana will search for neutrinoless double-beta decay using detectors made of enriched, specially engineered germanium-76 crystals. The 76Ge crystals, ranging in size from slightly larger than hockey pucks to slightly smaller than Coke cans, will be tied together in frames, or ?strings,? made of ultra-pure copper, which is being electroformed deep underground to avoid contamination by cosmic radiation. Ultimately the detector strings will be installed in two cylindrical cryostats, also made of electroformed copper, but the team also has constructed a prototype cryostat?made of commercial copper and filled with natural germanium crystals?to test the system.
The Majorana team began electroforming copper on the 4850 Level in July 2011. They moved into their Davis Campus lab last year, and now they?re building the experiment. ?The reason we?re here is because people are dedicated to doing this and they?re making real sacrifices,? Wilkerson told his colleagues. ?Being away from family is difficult, and we really appreciate that.?
For permanent Sanford Lab staff, living in the beautiful Black Hills is a perk, but the Majorana collaboration includes 18 different institutions in the U.S. and Canada and the experiment?s researchers are from around the world. For those scientists, the Davis Campus is a foreign posting. Making that posting easier for newcomers is the job of a group of four Majorana researchers called ?WBS 1.03.?
WBS is a project-management acronym for ?work breakdown structure.? The WBS system assigns a number to every task in a large project. Though members of this particular group sometimes laughingly describe themselves as the ?1.03 Stooges,? their task, ?Host Lab Infrastructure,? is critically important. ?We?re jacks of all trades,? said task leader Cabot-Ann Christofferson, a chemist at South Dakota School of Mines and Technology. ?We manage day-to-day operations.? The biggest challenge, she said, is making sure that researchers new to the site understand how Majorana procedures mesh with Sanford Lab protocols?especially regarding health and safety.
Christofferson?s 1.03 deputy task leaders are three post-doc physicists: Brandon White of Oak Ridge National Laboratory, Kirill Pushkin of the University of South Dakota and Wenqin Xu of Los Alamos National Laboratory.
?In John Wilkerson?s overview of the whole project he emphasized the importance of 1.03,? said Xu, a UCLA graduate who is from China.
?Basically, we?re keeping order,? Pushkin added. ?But we also have other specific tasks we?re working on.? Pushkin, who came to South Dakota from Alabama but who is originally from Russia, works on shielding and radon purging. White is part of the ?detector acceptance? group, which monitors the quality of the 76Ge crystals. (White also helped drive a load of enriched germanium from Tennessee to South Dakota, through a blizzard.) Xu works on data acquisition, and Christofferson is deputy task leader for copper electroforming.
More than half the electroformed copper has been produced, and all 10 of the underground electroforming baths are on their last run, Christofferson said. In addition, 9 kilograms of ultra-pure 76Ge is on site ?way ahead of schedule,? Wilkerson said.
The prototype cryostat will be ready for testing in a few weeks. Cryostat 1 could be taking data by the end of the year, and Cryostat 2 will be online by fall of 2014. Wilkerson?s bottom-line assessment: ?We?re keeping on schedule.?