LEAD — Progress at the Sanford Lab is moving forward as the race for dark matter continues.
On Friday, several media outlets were given a tour of the 4,850-foot level of the Lead laboratory, where scientists and engineers are searching for neutrinos and dark matter in the depths of the former Homestake gold mine.
The tour focused on three areas in the mine: the MAJORANA Lab, the Transition Cavern and the Davis Cavern. Each area of the old mine is being prepped for cutting-edge science experiments.
The Black Hills Pioneer was invited to be part of the tour, and after a long session on surface and underground lab safety, we descended into the facility via the Ross mineshaft.
Our first stop was the Clean Room at the MAJORANA Lab, a contained complex built into the mine tunnel where copper purification takes place. The copper begins at 99.95 percent purity, and through a chemical process is made ultra-pure, to within a trillionth of a percent.
We were able to watch part of the refining process through a viewing window. Scientists clad in full-bodied white suits and rainbow-hued protective eyegear transported small nuggets of copper from bin to bin, soaking it in acid baths, hosing it down with water and placing it in a sealed receptacle for further purification.
Lab officials said the purification process is used in industrial projects, but whereas the industrial world usually spends 10 days on purification, the lab spends five months in order to reach the right amount of purity for their experiments.
The purification process must take place below the surface to ensure the copper is free of radioactive particles that naturally exist on the earth's surface.
The purified copper will be used in future experiments to shield germanium crystals from radiation that would otherwise interfere with the tests. Lab scientists are trying to determine whether neutrinos are their own antiparticle, and even a small amount of radiation from the mine's rock walls - not to mention the sun — would negatively impact the quality of the material.
Dark matter is an elusive material said to compose 90 percent of the matter in the universe, but cannot be seen. Though its exact nature is still debated, lab officials compared finding dark matter with the discovery of electricity; if harnessed, it could end up providing humanity with a new energy resource.
Purified lead will also be used in the experiments. To get the proper purity, scientists have to collect the lead from old sunken ships from the time of the Romans to World War II. Being underwater for so long protects the lead from further radioactivity, mine officials said, and also allows the radioactive material present in the lead to break down, leaving the lead more pure as time goes by.
Later in the tour, we were chauffeured through the mine on an underground train to the Transition Cavern. Started in November 2009, this roughly 115,000 cubic-foot man-made cavern was excavated to make room for a new MAJORANA Lab, in which scientists can more extensively study neutrino activity.
At the time of the tour, engineers were scanning the cavern with laser equipment to create a high-definition, three-dimensional computer model, which they use to measure the strength and structure of the cavern throughout the construction process and after.
Engineer Kevin Hachmeister said the model has a number of applications, like aiding in the location of a joint set — similar to a miniature fault line — in different areas of the mine. It could also be used to create a virtual tour of the entire underground facility, making it accessible to people who may not be able to see it first-hand.
The group finally descended into the Davis Cavern, a 40-foot high space that will house an approximately 100-ton tank of purified water. The tank will house a smaller tank of Xenon and will be used as the locus of the Large Underground Xenon dark matter experment.
Dr. Jaret Heise, science liaison director at the lab, called the Davis Cavern “hallowed ground for neutrino physicists,” as it is the site of Nobel Prize-winning physicist Raymond Davis, Jr.'s Homestake Experiment, the first successful experiment to identify evidence of neutrinos from the sun.
For all its complexity, lab officials are adamant that continuing their research is highly important to scientific progress. Locating dark matter isn't just a local interest, they said; scientists around the world are racing to identify it. If it is found at Homestake, Heise said the discovery would “put us on the map” in the scientific community, adding to the worldwide recognition the mine already holds for its history with gold.
The lab has a lot of work to do yet before experimentation can begin, but if all goes well, the caverns should be ready for equipment installation in 2012.