At high energies (> 10 PeV), neutrinos can be most efficiently detected in dense, radio frequency (RF) transparent media via the Askaryan effect. The abundant cold ice covering the geographic South Pole, with its exceptional RF clarity, has been host to several pioneering efforts to develop this approach. Within the last years, a two-phased experiment ? the Askaryan Radio Array (ARA), designed to ultimately accumulate hundreds of high-energy GZK neutrinos - has been initiated at the South Pole Station, combining the drilling and logistics experience of the IceCube project, as well as the in-situ RF experience of the RICE experiment and the sub-nanosecond-scale data acquisition of the long-duration balloon project ANITA. The goal of ARA's Phase 1 (2010?2013) was to make deployment of a few testbed-type stations that used equipment designed and built under the NSF-funded MRI award. The next phase is to continue observations with these testbed stations to accumulate knowledge about RF properties of the upper layers of the ice sheet at South Pole and develop reliable hardware and software for deployable in-ice stations in the future. Recently-deployed three testbed stations are currently operational collecting data. Although the deployment of three testbed stations was generally successful, a number of problems were found in the full, 37-stations array deployment plans. This award is to provide bridge funds to keep the deployed testbed stations operational for another 12 months, while the project team reworks their proposal devising a staged approach for the full array deployment.
At high energies (> 1017 eV), neutrinos can be best detected in dense, radio transparent media via the Askaryan effect. The abundant cold ice covering the geographic South Pole, with its exceptional radio clarity, has been host to several pioneering efforts to develop this approach. In 2010, a new experiment called the Askaryan Radio Array (ARA), designed to ultimately accumulate the detection of hundreds of so-called "GZK neutrinos" was initiated at the South Pole, combining the drilling and logistics experience of IceCube, the in situ RF experience of RICE, and the sub-nanosecond data acquisition of ANITA. The first three years of the project centered on a single goal: to develop and build a small-scale neutrino detector embedded at shallow depths in the Antarctic ice sheet to observe these high-energy neutrinos. An eventual full-scale detector would then accumulate the statistics necessary to carry out a science program with broad intellectual merit, comprising basic particle physics, astrophysics, and glaciology. The success of that preliminary program, with three successful campaigns at the South Pole and working stations comparable in sensitivity to the IceCube experiment, has attracted considerable international attention with foreign collaborators who have proposed and/or pledged more than $3M in support, as well as substantial personnel resources. This second funding cycle, covering Summer 2013 through Fall 2014, had four limited objectives enumerated in the proposal that we summarize here along with how those objectives were met: a) Operation and data analysis of the existing detector. The existing ARA stations have continued in operation with an uptime of about 95% during 2014. Additional disk storage was installed both at South Pole and at the data warehouse at UW. We have both a weekly analysis phone call, and a weekly operations call. Three Ph.D. theses have been written with the ARA data. Journal publications using these data sets are in submission, and preparation, as of this report writing. b) Construction of a test system and reference detector at UW’s Physical Sciences Laboratory. These systems were purchased and integrated, primarily at National Taiwan University, and are now in use for an unexpected opportunity of testing the station electronics with a particle beam interacting in an ice target (at the Telescope Array site in Utah). After that experiment, the station will return to reference detector status in the large freezers at UW Physical Sciences Laboratory. c) Infrastructure development, in particular at OSU. The OSU ARA group has tooled up for cold testing of ARA subsystems and the construction of the miniATRI system which allows for a single string of an ARA station to be tested either in the lab in the north, or in the field at South Pole. This specifically addressed shortcomings in our in-field rapid testing of deployed station strings pointed out at a site visit (review) that took place in Washington, D.C. in spring 2013. d) Design of the miniATRI test system. This test system’s second-generation hardware is currently being built. The first-generation boards have been used by several groups in the States and overseas for software development for ARA and also as test platforms. The broader impact of the ARA project is realized through extensive involvement of both University students (particularly undergraduates who have significantly involved in the construction and preparation of hardware for South Pole deployment) and high school students (via the QuarkNet programs as well as a student intern program at UW), as well as aggressive publicizing of the ARA effort to the community at large via public talks, social media, and popular science articles. In addition to drawing on the combined RICE + IceCube + ANITA scientific heritage, ARA has also adapted and enlarged their well-established and ongoing Education and Outreach (E&O) programs. With its transformational science undertaken in a captivatingly hostile environment, ARA represents a truly unusual opportunity not only for scientific discovery but also for education and public outreach regardless of one’s level of scientific understanding. The adventurous nature of South Pole activity easily captures the imagination of the general public and attests to the public appeal of Antarctic science and astrophysics, in particular. ARA scientists and staff eagerly share the excitement of their experiences at the South Pole station and of the discovery potential of this project with a broad audience beyond the research community. Building on this excitement, ARA maximizes the educational value and public knowledge of IceCube science through talks to service groups, school visits, summer enrichment programs for Upward Bound students, and appearances in regional, national, and international media. ARA inspires a new generation of scientists to solve questions of extreme and fascinating physics, increase our knowledge of the Universe, create new technology, and expand options for future explorations.
