CUBED: South Dakota 2010 Research Center For Dusel Experiments

Nuclear Physics A 834 (2010) 816c–818c www.elsevier.com/locate/nuclphysa CUBED: South Dakota 2010 Research Center For Dusel Experiments Christina Kellera∗ , Drew Altonb , Xinhau Baic , Dan Durbend , Jaret Heisee , Haiping Hongc , Stan Howardc , Chaoyang Jianga , Kara Keeterd , Robert McTaggartf , Dana Medlinc , Dongming Meia , Andre Petukhovc , Joel Rauberf , Bill Roggenthenc , Jason Spaansa , Yongchen Suna , Barbara Szczerbinskag , Keenan Thomasa , Michael Zehfusd , Chao Zhanga a The University of South Dakota, Vermillion, SD 57069, USA b Augustana College, Sioux Falls, SD 57197, USA c South Dakota School of Mines and Technology, Rapid City, SD 57701, USA d e f Black Hills State University, 1200 University Street, Spearfish, SD, 57799, USA Sanford Lab, Lead, SD 57754, USA South Dakota State University, Brookings, SD 57007, USA g Department of Physical Sciences, Dakota State University, Madison, SD 57042, USA With the selection of the Homestake Mine in western South Dakota by the National Science Foundation (NSF) as the site for a national Deep Underground Science and Engineering Laboratory (DUSEL), the state of South Dakota has sought ways to engage its faculty and students in activities planned for DUSEL. One such effort is the creation of a 2010 Research Center focused on ultra-low background experiments or a Center for Ultra-low Background Experiments at DUSEL (CUBED). The goals of this center include to 1) bring together the current South Dakota faculty so that one may begin to develop a critical mass of expertise necessary for South Dakota’s full participation in large-scale collaborations planned for DUSEL; 2) to increase the number of research faculty and other research personnel in South Dakota to complement and supplement existing expertise in nuclear physics and materials sciences; 3) to be competitive in pursuit of external funding through the creation of a center which focuses on areas of interest to experiments planned for DUSEL such as an underground crystal growth lab, a low background counting facility, a purification/depletion facility for noble liquids, and an electroforming copper facility underground; and 4) to train and educate graduate and undergraduate students as a way to develop the scientific workforce of the state. We will provide an update on the activities of the center and describe in more detail the scientific foci of the center. ∗ supported by the Governor’s Office of Economic Development, through a 2010 Center Grant 0375-9474/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.nuclphysa.2010.01.155 C. Keller et al. / Nuclear Physics A 834 (2010) 816c–818c 817c 1. Introductions In addition to being a productive gold mine and serving as an economic engine for western South Dakota, the Homestake gold mine also served as the home for a seminal experiment in nuclear astrophysics. In the search for solar neutrinos, Ray Davis, a physicist at Brookhaven National Lab located a large tank of perchloroethylene in a mining cavity approximately 5,000 ft underground. The experiment detected solar neutrinos, but at one third the rate predicted by current models for the energy production within the Sun. The discrepancy was confirmed by later neutrino experiments, and Ray Davis was awarded the 2002 Nobel Prize in Physics, the first and only Nobel Prize awarded to an experiment located in the State of South Dakota. Mining operations ceased at Homestake in late 2001, and the possibility of converting the extensive underground space into an interdisciplinary national laboratory began to take shape. The State formed the South Dakota Science and Technology Authority (SDSTA) to serve as landlord and to manage the property. $39M was appropriated by the State Legislature, and $70M was donated by T. Denny Sanford for the establishment of the Sanford Lab, with a primary focus on ultra-low background experiments. And in 2007, NSF selected Homestake as the potential site of a national deep underground science and engineering Laboratory (DUSEL). The location of a national science lab in South Dakota presents tremendous opportunities for a state with agriculture and tourism as the primary economic engines of the state and fits perfectly with the state’s 2010 initiative, which outlines a series of goals to promote economic growth within South Dakota. [1] In response to planned experiments at Sanford Lab/DUSEL, South Dakota’s governor announced the creation of a new 2010 center for ultra-low background experiments at DUSEL (CUBED), focused on materials purification and crystal growth underground and led by The University of South Dakota. CUBED provides a mechanism for scientists within South Dakota to come together in such a way as to develop a critical mass of expertise for participation in planned large scale collaborations focusing on the direct detection of dark matter and neutrinoless double beta decay, and located at DUSEL. The emphasis on experiments focusing on dark matter and neutrinoless double beta decay is consistent with the priorities identified by a national panel (P5 report) as two of the highest funding priorities for particle physics in the immediate future. These discovery opportunities have tremendous funding potential, both through the NSF-sponsored research programs, as well as commercial opportunities developed as a result of the materials production techniques developed in this center. The expected scientific outcomes will impact undergraduate and graduate education in the state, and may also fuel economic growth in the areas of materials development and production. 2. Scientific Goals Experiments searching for rare events require an unprecedented level of purity in the materials used to construct the detector, and must be located in an ultra-low background environment. The community recognizes that to fully exploit this exciting physics program and achieve the planned sensitivity one needs the shielding of a deep underground laboratory and an underground ultra low background facility to screen materials for radioactive contamination. Certain DUSEL experiments require detectors made from single crystal germanium for neutrinoless double-beta decay experiments [2] and NaI/CsI crys- 818c C. Keller et al. / Nuclear Physics A 834 (2010) 816c–818c tals for dark matter searches [3,4], with estimates on requirements exceeding 1000 kg. While domestic firms do produces crystals of this type, demand will exceed current production limits, and there is no motivation to increase production limits. Additionally, these firms all produce crystals in a surface environment leading to an increase in the cosmogenic production of 68 Ge and 60 Co in enriched 76 Ge produced on the surface. These isotopes can seriously limit the sensitivity of next generation double-beta decay experiments if the crystals reside on the surface for as little as a week. This sets strict constraints on allowable production time and transportation at the surface. Thus, purification and crystal growth performed underground avoids cosmogenic contamination and is greatly preferred over surface processing and shipping. A goal of CUBED is to construct an underground crystal growth facility at DUSEL to provide ultra-pure crystals for use in neutrinoless double beta decay experiments and direct dark matter searches. Noble gases also serve as excellent detectors for dark matter searches, with Argon being one of the preferred gases. Unfortunately, the presence of 39 Ar in naturally occurring Argon, even at the level 10−15 g/g, provides an undesirable background as one scales up to multi-ton experiments. The physics community has considered several different approaches to obtain argon depleted of 39 Ar, and the CUBED center is exploring two such methods. The first adapts the well known method of using thermal diffusion columns for isotope enrichment; the second looks at extracting argon from water reservoirs located in geologically old rock formations. We hope that using argon from underground wells as a starting material for the thermal diffusion columns may result in a depletion factor as large as one thousand. 3. Center Economic Goals/Education Goals In addition to building collaborations among existing faculty, CUBED also initiates the process of increasing the number of trained physicists in South Dakota. Two new research faculty will be hired using center funding to contribute to the development of DUSEL projects, and pursue external funding. The center also funds post-doctoral researchers, graduate students, and other skilled technical positions. Finally, the activities of the center will contribute to the new state-wide Master’s program in physics approved to begin in the fall of 2009, and will play an important role in the success of a proposed doctoral program in physics. The program is planned to be cooperative among the state institutions, and when approved will remove South Dakota from the list of only two institutions in the United States which do not offer a Ph.D. in physics. REFERENCES 1. http://www.2010initiative.com/2010initiative.asp 2. The Majorana neutrinoless double-beta decay experiment, the Majorana collaboration. 3. R. Bernabei et al., Eur. Phys. J. C 53 (2008) 205. 4. E. Won et al., Nuclear Physics B - Proceedings Supplements Volume 78, Issues 1-3, August 1999, Pages 449-453.