Pierre Auger Observatory Central Laser Facility Upgrade

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This award will assist in funding an upgrade to the Central Laser "test beam" Facility (CLF) located near the center of the Pierre Auger Observatory (PAO). The PAO uses the atmosphere as a giant calorimeter to measure the highest energy particles known to exist. At these extreme energies (1-100 EeV; 1 EeV = 10^18 eV; 1 eV is the energy an electron or proton gains when it is accelerated by a voltage of one Volt), particle test beams, traditionally used to characterize accelerator based detectors, simply do not exist. However, light scattered out of a pulsed Ultra-Violet (UV) laser beam directed into the atmosphere will generate tracks that can be recorded by the same fluorescence detectors that record tracks from extensive air showers. There is an approximate effective optical equivalence between a 5 milliJoule UV laser track and a 100 EeV air shower. The proposed CLF upgrade will add a Raman LIDAR receiver and a robotic photometric calibration system, and make related improvements. It will target three specific areas:1. Use the "super test beam" to crosscheck the end-to-end photometric calibration of the fluorescence detector which sets the energy scale for the observatory. 2. Within a few minutes of the detection of air-showers of particular interest, the Raman receiver will make an independent precision measurement of the aerosol optical depth profile and water vapor profile. Events of interest include very high energy candidates detected in hybrid mode, air showers from the region near the radio galaxy Centaurus A, and exotic candidates with shower profiles that may not fit the standard shape. Aerosol optical depth is the largest time varying correction applied to air shower reconstruction. 3. Systematically compare the aerosol optical depth profiles measured by the Raman LIDAR receiver and by the side-scatter method currently used to fill the observatory's aerosol profile database. This comparison is especially important to the elongation rate analysis of hybrid data that suggests the particle composition may transition to heavier primaries above 10 EeV.CSM undergraduates are naturally involved in the research, as they are required to complete a senior design project as part of their curriculum. Raman LIDAR is a standard aerosol profile measurement technique that will enhance the usefulness of the atmospheric data base collected by non-traditional methods. This will enable more direct comparisons with other data sets in the atmospheric science community.