CWRU Physics Faculty
Corbin E. Covault
Professor of Physics
B.A., Massachusetts Institute of Technology (1985)
Ph.D., Harvard University (1991)
Experimental Particle Astrophysics, Gamma-Ray Astronomy, Ultra-high Energy Cosmic Rays
Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE)
I am particularly interested in the application of ground-based air shower detectors for gamma-ray astronomy. During the past decade, the unanticipated detection of high energy gamma-rays (between energies of 1 GeV and 10 TeV) from dozens of sources by space- and ground-based experiments has revolutionized our understanding of high energy processes in the universe. Gamma-rays result from high-energy interactions in the most compact and energetic sources inside and outside our galaxy. Gamma-rays from pulsars and supernova remnants are providing critical clues to the origin of cosmic rays. Furthermore gamma-rays dominate the outburst emission of certain AGN galaxies -- called "Blazars" -- indicating the presence of relativistic jets beamed toward the observer. Jets also appear to play a critical role in explaining the mysterious gamma-ray burst sources. Observed absorption features in extra-galactic gamma-ray spectra may provide an important probe of the intergalactic IR and optical photon field which in turn places significant constraints on cosmological models and theories of structure formation. A complete understanding of the high energy processes occurring in these most energetic sources requires full-spectrum gamma-ray observations. Until recently, the energy range from 20 to 300 GeV has been inaccessible, representing a gap in the gamma-ray spectrum and hindering further progress in gamma-ray astronomy.
Our group has recently developed and is operating a new experiment, called STACEE (Solar Tower Atmospheric Cherenkov Effect Experiment). STACEE is currently operating at the National Solar Thermal Test Facility at Sandia National Laboratories in Albuquerque, NM. The Sandia site contains over 200 steerable heliostat mirrors, each with 36 square meters of collecting area. By taking advantage of these pre-existing mirrors, we have been able to develop a new experiment with a very large light collection capability. We use the heliostat mirrors at night to collect Cherenkov light emission associated with gamma-ray air showers. STACEE is sensitive to gamma-rays in the energy range from 50 to 250 GeV, corresponding to this previously "unopened window" between current space- and ground-based techniques. Observations in this window are key to understanding the mechanisms for high energy particle acceleration in some of the most powerful astrophysical sources, including pulsars, active galactic nuclei, and supernova remnants.
The Pierre Auger Observatory for Ultra-High Energy Cosmic Rays
I am also very interested in ground-based techniques to determine the origin of the highest energy cosmic rays. The origin of these cosmic rays is a profound mystery in astrophysics. The rate of cosmic rays above 1020 eV is only one particle per square kilometer per century. There is no known mechanism for creating such high energy cosmic rays, but a small handful have been detected by previous experiments. To accurately measure the arrival direction of a statistically complete sample of such cosmic rays, an enormous detector must be built. Construction has started on the the Pierre Auger Observatory, an giant array with 1600 detectors that will eventually cover an area of 3000 square kilometers with thousands of detectors. Auger is a hybrid detector using both a ground-array of water-Cherenkov tanks and an atmospheric fluorescence detector based on the Fly's Eye technique. Our group is actively working to develop and test ground detectors for deployment at the southern hemisphere site in Mendoza Province, Argentina. Construction of Auger is scheduled to be completed in 2005.
X-ray Occulting Steerable Satellite (XOSS)I am working with other members of the department on a design concept called the X-ray Occulting Steerable Satellite (XOSS) . This would be a device that might provide near milli-arcsecond (mas) resolution of x-ray sources using current and planned future space-based x-ray detectors.