Telescope Array Project
| Organisation | Multi-national |
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| Location(s) |
Millard County, Utah United States |
| Coordinates | 39°17′49″N 112°54′31″W / 39.29694°N 112.90861°W |
| Altitude | ~1400 m |
| Built | 2007 |
| Telescope style | Hybrid (Surface + Fluorescence detectors) |
| Website | Official site |
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The Telescope Array project is an international collaboration involving research and educational institutions in Japan, The United States, Russia, South Korea, and Belgium. The experiment is designed to observe air showers induced by ultra-high-energy cosmic ray using a combination of ground array and air-fluorescence techniques. It is located in the high desert in Millard County, Utah (USA) at about 1,400 meters (4,600 ft) above sea level.
The Telescope Array observatory is a hybrid detector system consisting of both an array of 507 scintillation surface detectors (SD) which measure the distribution of charged particles at the Earth's surface, and three fluorescence stations which observe the night sky above the SD array. Each fluorescence station is also accompanied by a LIDAR system for atmospheric monitoring. The SD array is much like that of the AGASA group, but covers an area that is nine times larger. The hybrid setup of the Telescope Array project allows for simultaneous observation of both the longitudinal development and the lateral distribution of the air showers. When a cosmic ray passes through the earth's atmosphere and triggers an air shower, the fluorescence telescopes measure the scintillation light generated as the shower passes through the gas of the atmosphere, while the array of scintillator surface detectors samples the footprint of the shower when it reaches the Earth's surface.
At the center of the ground array is the Central Laser Facility which is used for atmospheric monitoring and calibrations.
The surface detectors that make up the ground array are activated when ionizing particles from an extensive air shower pass through them. When these particles pass through the plastic scintillator within the detector, it induces photo electrons which are then gathered by wavelength-shifting fibers and sent to a photomultiplier tube. The electronic components within the detectors then filter the results, giving the detectors comparable accuracy to the AGASA experiment.
The surface detectors are evenly distributed across a 762 km2 grid array with 1.2 km between each unit. Each surface detector has an assembled weight of 250 kg and consists of a power supply, two layers of scintillation detectors and electronics. Power is generated by a 120W solar panel and stored in a sealed lead-acid battery. The system has the capacity to operate for one week in complete darkness. Each scintillation detector layer is made of extruded plastic scintillator that is 1.2 cm thick and has an area of 3m2. The photo multiplier tube is connected to the scintillator via 96 wavelength-shifting fibers.
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