This proposal requests support for the research activities of the High Energy Astrophysics (HEA) group in the Physics Department at Case Western Reserve University which is active in two major experimental projects: (1) The Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE) for detecting gamma-rays in the 50 to 250 GeV range, and (2) The Pierre Auger Observatory (PAO) for observing the highest energy cosmic rays at EeV energies.
STACEE is a ground-based gamma-ray detector using the heliostat mirrors of a solar array to collect atmospheric Cherenkov radiation. The large mirror area available at the array permits STACEE to operate at energies well below previous ground-based instruments and to explore the gamma-ray energy range between 50 and 250 GeV. The experiment has been in continuous operation since 2001 and has observed and reported results on several Active Galactic Nuclei (AGN), gamma-ray pulsars and supernova remnants, and has searched for high-energy emission from Gamma-Ray Bursters (GRB). This proposal requests support for the continued operation of STACEE, and the participation of the Case HEA group as one of its founding members. Activities on STACEE will ramp down during the proposal period as this experiment ceases observations on June 1, 2007.
The Auger Observatory is a new major international experiment to measure the energy and arrival direction of Ultra High Energy Cosmic Rays (UHECR) above 1020 eV. The origin of the UHECR remains one of the important questions being probed in UHECR physics. The Auger Observatory is a hybrid detector consisting of two co-located detector systems: (1) an array of 1,600 water Cherenkov Surface Detector (SD) stations spread over 3,000 square kilometers area for detecting air shower particles on the ground, and (2) a set of four Fluorescence Detector (FD) telescopes which provide stereo calorimetric measurements of the development of cosmic ray showers as the propagate through the atmosphere. The experiment is located near Malargue, Argentina and construction is well underway, with three of the four FD's operational and more than 950 of the 1,600 SD stations installed and running. Data from the partially complete Auger observatory are being collected and the first set of science results from Auger have recently been presented. The Auger Observatory will be completed by early 2007. This proposal requests support for the continued participation of the Case group in Auger, which participates in several areas of detector development, deployment, calibration and data analysis.
Broader impacts: Several members of the Case group are active in a variety of education and outreach programs, including a new program for physical science instruction for Cleveland high school teachers and the application of wireless transmitters ("clickers") for introductory physics education. Several techniques developed for STACEE and Auger by the Case group are applicable in other arenas, including: (1) the use of heliostats to support remote sensing by earth-viewing satellites, (2) the design and application of new types of non-imaging optical systems, and (3) the development of mirror measurement techniques for solar energy applications.
Here we describe the scientific activities supported by NSF grant 0601088. This grant was originally funded for the three-year period (06/01/2006 through 05/31/2009). This grant supports the scientific activities of the High Energy Astrophysics (HEA) group in the physics department at Case Western Reserve University. Members of the HEA group play a major role in the Pierre Auger Cosmic Ray Observatory (PAO), which has been constructed and is operated by an international consortium of collaborators. The purpose of the Auger Observatory is to study the highest energy cosmic rays -- high energy particles that travel through the Universe. Discovered by Victor Hess in 1912 during a high-altitude balloon flight, the cosmic rays are particles of intense energy arriving to the Earth from all directions is space. However, even after decades of effort by astrophysicists, the origins and exact nature of these most energetic particles remains an elusive mystery. These are the most energetic particles in the Universe, as much kinetic energy as a fast-pitch baseball concentrated into a single subatomic particle. How is it possible that such a large amount of energy can be concentrated in such a small package? What is the nature of those astrophysical objects where such particles might be accelerated? What can we learn about fundamental physics by studying the process of how these particles are accelerated and propagate to us? These are the questions that the Pierre Auger Cosmic Ray Observatory has been designed to address. The purpose of the Pierre Auger Observatory is to measure the arrival directions, energies and other physical properties of the highest energy cosmic rays. When these particles enter the Earth's atmosphere from space, an extensive shower of new particles is created which then rains down to the surface. Auger is an array of over 1600 individual particle detectors arranged over an area of 3000 square kilometers, located in the high desert pampas of Argentina to the east of the Chilean Andes. The Auger Observatory is a large international collaboration of more than 400 physicists from 19 countries. For Auger, construction of experiment in Argentina is complete, and the Observatory has been operating continuously at full size since 2008. Auger has observed dozens of cosmic rays at the highest energies, and has already extended the the exposure to several times over that achieved by all previous experiments combined. Auger has now reported results for cosmic ray energy spectra, upper limits on the fraction of gamma-rays )which places a strong constrain against top-down source models), and upper limits on tau neutrinos. All of these results place strong constraints on models for the astrophysical origins of cosmic rays. Additionally, the Auger experiment has presented a major result in the detection of anisotropy for the highest energy cosmic rays where we have shown that the arrival directions are correlated with the positions of relatively near by Active Galactic Nuclei (AGN) believed to be large black holes located at the centers of large galaxies. This new result conclusively demonstrates the extragalactic nature of the sources of the highest energy cosmic rays and opens the door for future prospect for conducting "charged particle astronomy", with the ultimate goal of identifying individual astrophysical sources of cosmic rays in the sky. The Case Western group continues to have a leadership role in the Auger Collaboration in two main technical arenas: (1) GPS event time-tagging, which is critical for Auger shower arrival direction reconstruction and (2) large-area wireless telecommunications which are critical to collect data and to control the operation of the observatory. Both of these efforts involve new applications of these technologies that can be used in other fields of science and technology for a wider impact. The HEA group at CWRU has developed and continues to improve and upgrade a set of portable time-tagging systems which can flexibly determine the absolute GPS time to better than 20 nanoseconds for any electronic or optical signal at any position in the field. We continue to improve our understanding of the timing performance of Auger, working closely with the Auger group at Colorado School of Mines (CSM) and have developed and deployed a new set of timing systems for the new Xtra Laser Facility (XLF) located at the center of the Auger array. Since 2007, the CWRU group leader has served a key role as the Task Leader for Wireless telecommunications (Comms), dealing with the extensive wireless LAN network connecting all detectors to the central campus. The PI has direct and ongoing responsibility for the operation and performance of the surface detector station wireless radio transmitters, a set of four communications towers, and all associated microwave backbone data transfer system. The PI also supervises, coordinates, and troubleshoots all other wireless communication issues on site, including voice Comms (walkie-talkie), point-to-point 2.4 GHz data relays, and site WiFi.
