Newswise — Scientists are gearing up for development now that the decision has been made to place a deep underground science and engineering laboratory in the former Homestake Gold Mine.The National Science Foundation announced July 10 that Homestake is the preferred site for such a project. Assistant professor of physics Robert McTaggart, who helped coordinate South Dakota State University's involvement in the project, said South Dakota scientists and the state economy will benefit from the plan.
The Black Hills mine complex will eventually be adapted as the setting for science experiments at depths of up to 8,000 feet, though the initial development will take place at 4,850 feet. "Homestake has two things going for it. One is it has a lot of pre-excavated sites that can be engineered to house experiments," McTaggart said. "The main reason they want to go there is the rock itself. The rock provides shielding from cosmic rays that can mimic exotic physics events such as neutrinos, dark matter, and signals from proton decay.
"We know a lot about the structure of the mine from a hundred years of previous experience in excavating gold from the Homestake Mine. It will be easier to put physics infrastructure at a lower depth than any of the other competing sites," the scientist concluded. McTaggart said having the world-class laboratory in South Dakota will have "unimaginable" effects on physics and related disciplines at SDSU and other state universities. Top science graduates also may have the chance to stay in South Dakota and work at the lab, McTaggart said. "To put it bluntly, this decision means that students who major in mathematics, physics, chemistry, biology and engineering in South Dakota universities such as SDSU are going to have a place to go after they graduate, so they can stay within the state." McTaggart said faculty at SDSU and other state universities have submitted proposals to the Department of Energy EPSCoR, or the Experimental Program to Stimulate Competitive Research, for two initial projects related to infrastructure needs. Led by assistant professor Dongming Mei from the University of South Dakota, physicists want to determine the levels of naturally occurring radiation in materials and remove as much of it as possible.
If approved, both projects would be implemented over the course of three years. The cost of the two projects together would exceed $2 million. "One project would be a facility to assay materials brought into the mine for radioimpurities, which is necessary because we want to either reduce the radioactivity for incoming material as close to zero as possible, or know about it in advance.
"To make an analogy, we're looking for hay-colored needles in a haystack. The layers of rock at the mine remove a great deal of that haystack by blocking cosmic rays. So why would we want to bring in more hay via the transport of materials into the mine?" For example, McTaggart said, cosmic rays can convert small amounts of copper into radioactive cobalt at ground level. If scientists brought in copper that was neither treated nor sampled, radioactive decays from that small amount of cobalt could mimic true events and throw off any results. There's also a need for purified water, which is going to be important for detecting neutrinos. "A neutrino doesn't interact very often with matter, but when it does, it can knock off an electron. Electrons traveling faster than the speed of light in water produce 'Cherenkov light' in much the same way that an airplane produces a shock wave when going faster than the speed of sound in air," McTaggart said.
"Most materials besides purified water will absorb too much of the Cherenkov light before it reaches any detectors. As a result, we may miss events entirely or misinterpret the events we see." Another project on deck for the Homestake facility would use lasers to ionize and remove unwanted isotopes in the purification of noble gases used for dark matter detection.
However, similar techniques could be applied to other gases and solids. Many other experiments that go into the mine would benefit from such ultra-pure materials. National laboratories at Berkeley and Los Alamos will be directly involved with both proposals. Collaborations with researchers elsewhere will continue to build now that the decision has been made to place the deep underground science and engineering lab in South Dakota.
"SDSU has a memorandum of understanding with Argonne National Laboratory, so we're actively investigating ways to incorporate Argonne National Laboratory into our plans," McTaggart said. In addition to particle physics, other applications in microbiology and engineering are also under consideration.
"Here at SDSU, microbiologists such as professor Bruce Bleakley are interested in life deep underground that can exist without sunlight and in extreme conditions that at first glance should not support life. These microbial life forms may influence research into cancer, bioprocessing for ethanol, and the existence of life in extreme conditions both on earth and elsewhere in the solar system," said McTaggart. With regard to engineering, there will be many opportunities to support the construction of detectors and other experimental infrastructure at the mine and elsewhere throughout the state. In addition, the reduced cosmic-ray environment may also lead to new technologies in the future. "Impacts from cosmic-rays at the ground level can affect crystal growth and the behavior of semiconductor materials or other alloys. The Homestake Mine could produce the purest crystalline structures to date," McTaggart said. The project also will help drive regional economic development, he added. "This can occur as the state attracts more faculty, more students, and more employees to work at high-tech companies. When they buy food, homes, and other products, economic development will result for the state."
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