A Cherenkov Radiation Detector Design for the Observation and Measurement of High Energy Cosmic Rays Yvette Cendes, Research Adviser: Corbin Covault Department of Physics, Case Western Reserve University The Pierre Auger Observatory is a large-scale experiment devoted to the detection of the highest energy cosmic rays. Currently phase one of the Auger experiment in Argentina, known as Auger South, consists of detectors spread over several kilometers.[1] Plans are being developed for an Auger North facility in southeastern Colorado. The energy of particles detected by the Observatory are currently callibrated with expensive florescence detectors. Further, several puzzles remain unanswered, such as the composition of the cosmic rays and their exact energies, which are questions a Cherenkov radiation detector would be designed to address. INTRODUCTION The primary component of the detector is a photomultiplier tube (PMT) most sensitive in the blue- ultraviolet wavelengths of Cherenkov radiation. To reduce ti impact of sky brightness at low elevation angles, we have developed a “Winston cone” which restricts the field of view to approximately 40 degrees from zenith. High-energy cosmic rays are particles from deep space with energies greater than eV. Although their origins are unknown, recent Auger observations indicate a correlation between the cosmic rays and Active Galactic Nuclei, which are supermassive black holes.[2] When a cosmic ray hits the upper atmosphere, it sets into motion a chain of interactions in what is known as a particle shower. A byproduct of this shower is Cherenkov radiation, created when a particle moves faster than the speed of light in a medium. Observing this light can yeild important information about the energy and composition of the original cosmic ray particle. We have conducted simulation study in order to fully understand the expected measurements from the detector. In order to do this, photons were simulated with the CORSIKA package ( Figure 5). We have also simulated the detector responseto light, and the circumstance of several detectors in an array was also considered. SIMULATIONS Additional testing of the design is needed to ensure that cosmic ray showers will be successfully detected. We will do this by using four scintillator panels to detect cosmic ray showers, which will in turn trigger the Cherenkov detector. If light is observed by the detector corresponding to the particle shower, it will be a confirmation that Cherenkov radiation can be detected with this method. In addition to this, we will examine the overall feasibility of the Cherenkov radiation detector as a part of the Auger Observatory. 1.Pierre Auger Observatory. September The Pierre Auger Collaboration. Correlation of the nearest High-Energy Cosmic Rays with Nearby Extragalactic Objects. November 9, REFERENCES Figure 5: The final setup of the Cherenkov detector. Here, the scintillator panels (depicted as crabs) detect the cosmic ray shower particles, which in turn trigger the Cherenkov detector to detect radiation. Image courtesy: Ross Burton Figure 4: The Cherenkov detector when assembled with the photomultiplier tube, the base, and the Winston cone. I would like to thank the members of HEA group for all their help in this project. In particular, I would like to express my thanks to Ross Burton for his assistance and simulation work, as well as Kate Oldak and Jonathan Douglas for their help with the Winston cone design and construction. Figure 1: Artist’s conception of a cosmic ray particle shower at the Auger Observatory. Image credit: Auger Figure 3: The Winston Cone from above. Notice how the collection area is effectively twice as large as it was without the photomultiplier tube. Figure 2: Measurements taken to determine the Winston Cone dimensions. It was calculated that the cone should only accept light at a maximum of 40 degrees from zenith for full optimization. The Winston cone was then constructed and coated with a thin layer of aluminized mylar in order to reflect unwanted background light. The new PMT and Winston Cone apparatus was retested against the night sky, and measurements indicated a significant reduction in background light levels. The components of the detector were then assembled. A sturdy base was constructed along with plastic dowels to hold the cone in place, and the entire apparatus was raised in order to run the necessary input voltage and output feed cables to the PMT. FINAL SETUP Figure 5: A simulation of Cherenkov photons from the ground in a TeV shower- 45 degrees from zenith. SCIENTIFIC MOTIVATION AKNOWLEDGEMENTS FUTURE STUDY DESIGN