This award supports the continuing research program at Black Hills State University in underground astrophysics research. The focus is mainly on dark matter and neutrinoless double-beta decay experiments planned for the Sanford Underground Research Facility (SURF) at Homestake, SD. For the dark matter experiments, DARKSIDE and MAX, BHSU is designing, building, and optimizing a continuous wave custom cavity ring-down spectroscopy (cw-CRDS) system for measuring the level of impurities in argon gas. This is important for the success of the depleted argon-based dark matter detectors. With this award the BHSU group expects to improve upon the sensitivity of commercial CRDS systems by at least an order of magnitude. The BHSU group will setup the facilities needed to clean the ancient lead bricks to be used for shielding the double-beta decay experiment, MAJORANA.
Broader impacts: Every summer the BHSU group involves South Dakota undergraduates in hands-on research. The BHSU QuarkNet Center, established in 2009, is one of the most active QuarkNet Centers in the country. Last year five teachers brought about 30 students to participate in an LHC Masterclass held at Homestake. As the group enters their 4th year, they expect to add about four new teachers to the Center. In addition, the BHSU group is working with representatives from Oglala Lakota College, in an effort to establish the first QuarkNet Center at a Tribal College or University (TCU).
This award was the primary funding establishing and supporting the activities of the BHSU Underground Particle Astrophysics research group. The main goal of this project was to establish a research program at Black Hills State University in underground particle physics. Objectives include providing opportunities to undergraduate students at BHSU and throughout SD to participate in neutrino and dark matter research; building a program in underground particle astrophysics; and establishing BHSU as a participating member in neutrinoless double beta decay experiments and dark matter searches. Beginning in 2009 with the hiring of Dr. Kara Keeter, research activities in underground physics at BHSU have greatly increased to include activities in both neutrino experiments and dark matter searches in addition to underground measurements of radiological background levels. With this grant and other federal and state sources, the group has supported a number of undergraduate and graduate students and research technicians including many women and some American Indian students. The group expanded with the hiring of postdoctoral researcher Brianna Mount in March 2011 (now Research Assistant Professor as of August 2013) and is now an active member of the Majorana Collaboration (building a neutrinoless double-beta decay detector based on 76Ge at the Sanford Underground Research Facility), the DarkSide Collaboration (building a liquid-argon-based WIMP dark matter detector at the LNGS in Gran Sasso, Italy), and the state-wide Collaboration for Ultralow Background Experiments in the Dakotas (CUBED) with low background measurements at Sanford Underground Research Facility (SURF). In addition, BHSU is building an Underground Campus on the 4850’ level at SURF; it will be ready for occupancy in 2015. This grant has been funding BHSU’s participation in DarkSide. By building a trace gas analyzer based on cavity ring-down spectroscopy (CRDS) technology, BHSU is providing a vital component to the DarkSide Collaboration. Initially, this project concentrated on setting up an optics lab for building a custom CRDS system for measuring trace gas impurities in noble gases such as argon and xenon that are important in dark matter detectors. Since the hiring of Dr. Mount, activities have centered on the design, construction and commissioning of the customized CRDS instrument. The instrument measures trace amounts of CH4, H2O and other impurities in noble gases such as argon and xenon that are of interest in dark matter detection. The sensitivity is projected to be at least an order of magnitude better than currently available commercial products. Large-scale liquid noble gas scintillation detectors are the basis for many current and proposed particle astrophysics experiments including dark matter searches, neutrinoless double beta decay experiments, and long baseline neutrino experiments. Impurities in the liquid argon reduce the overall light yield and disrupt the scintillation signal that is used to reject background events. To test the impurity levels in these liquid noble gases, we have developed at Black Hills State University (BHSU) a Cavity Ring-Down Spectroscopy (CRDS) system. The resulting instrument measures trace amounts of CH4, H2O and other impurities in noble gases such as argon and xenon that are of interest in dark matter detection. The sensitivity is projected to be at least an order of magnitude better than currently available commercial products. With our current noise level in the ring-down time, we can measure approximately 1.0 ppb water vapor in nitrogen and are in the process of improving this noise level iteratively by more careful mode-matching and better temperature and pressure stabilization of the cavity. Additionally, simply by lengthening our cell to 2 m (under discussion with TigerOptics) and assuming our current noise level (before any mode-matching changes, etc.), our sensitivity will be approximately 0.1 ppb. Twenty or more undergraduate students from 5 separate institutions have worked directly or indirectly on this project; about half a dozen other students and technicians have worked on related projects with the underground research group at BHSU. At least two have been American Indians; about half have been women. The BHSU QuarkNET Center is very active, and works synergistically with the BHSU underground physics research group. Brian Lowery (Aberdeen High School teacher) and Chad Ronish (Hill City High School teacher) were the "lead teachers" for the BHSU QuarkNet Center. In the summer of 2009 they participated in hands-on research activities (primarily the magnetic field measurements and radon measurements at Homestake) and worked on adapting teaching and learning materials for the classroom to incorporate their research experiences. Each summer since then, the member teachers meet during the summer and work on cosmic ray muon detector activities in addition to activities related to underground science. The group has now grown to nine members and plans to expand this year as well. In the summer of 2014, BHSU also hosted the Virtual QuarkNET Group.
