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Show 178 ABSOLUTE CALIBRA TION OF STANDARD LIGHT SOURCE FOR THE TELESCOPE ARRAY PROJECT AIR FLUORES CENCE TELESCOPES Gina Vasilo , (John Matthews) Department of Physics and Astronomy University of Utah RESEARCH POSTERS ON THE HILL SPRING 2012 Absolute Calibration of Standard Light Sources for the Telescope Array Project Air Fluorescence Telescopes Gina Vasiloff, John Matthews Physics Student Photo Faculty Photo Image upper middle 2 Image upper right 3 The large mirrors reflect and focus light from air fluorescence from cosmic ray showers onto large cameras. The cameras must be accurately calibrated to ensure we are using valid data in our analyses. To do this we use a special lamp called a roving xenon flasher (RXF) as a fixed light source. If we know the amount of light output by the RXF and the amount of light detected by the camera, we can find the detection error of the camera. Conclusion Gina Vasiloff John N. Matthews Data Analysis Cosmic Rays Fluorescence Telescopes A cosmic ray is any particle that has traveled to Earth from beyond Earth's atmosphere. When a cosmic ray enters Earth's atmosphere, it collides with and accelerates an air molecule. The cosmic ray and air molecule both go on to accelerate more air molecules creating what is called an extensive air shower. By observing air showers, we are able to deduce information about the cosmic rays that caused them. Telescope Array The Telescope Array is comprised of three fluorescence detector sites and a ground array of 507 smaller detectors. The RXF must itself be calibrated before it can be used to calibrate the fluorescence detectors. We used a hybrid photodiode (HPD) to measure the light output from the RXF. The hybrid photodiode measures the amount of photons put out each time a light is flashed at it. The HPD and RXF were placed in a dark box along with a light emitting diode (LED). The light output by the LED and then by the RXF is measured by the HPD. The LED was set to put out an average of one photoelectron per flash so we can find the single photoelectron gain of the HPD. Based on the single photoelectron gain, we can determine the number of photoelectrons output by the RXF. The single photoelectron gain and the mean of the RXF signal are then put into the following formula to calculate the photon density of the RXF's signal. Experimental Setup Mirrors and Cameras at Middle Drum Fluorescence Detector The Telescope Array Project is designed to detect and measure the highest energy subatomic particles. These mysterious particles from space are far higher in energy than any created in accelerators on Earth. We have provided a system for accurate absolute calibration of the fluorescence telescopes. In doing so, we enabled the project to gather reliable data about these ultra high energy cosmic rays. This data will be used to further understanding of our universe and answer questions about the origin and nature of these extraordinary particles. The Telescope Array Project is the largest Ultra- High Energy Cosmic Ray (UHECR) experiment in the northern hemisphere. When an UHECR en ters the Earth's atmosphere, it collides with the nucleus of a molecule in the atmosphere. This collision produces a number of particles. Each particle carries some part of the energy of the original UHECR particle. These high energy particles go on to collide with more air molecules. The process repeats itself many times over resulting in a cascade of millions or billions of particles. The Telescope Array Project uses both fluorescence telescopes and an array of particle detectors on the ground to observe these particle cascades. Using this information we can determine the energy, chemical composition and arrival direction of the original UHECRs. A light source called the Roving Xenon Flasher (RXF) is used as a "Standard Candle" to illuminate and calibrate the air fluorescence telescopes. We have developed a system using a hybrid photo diode to measure the light output (number of photons per square millimeter) produced by each flash of the RXF. The RXF is very stable and easily transported between telescopes and observatories. This allows us to transfer laboratory calibrations to instruments in the field and perform an absolute calibration of the telescopes at all of the observatories. |