To perform cold tests on the different modules of the ATLAS liquid argon calorimeter, a cryogenic system has been constructed and is now operated at the CERN North Experimental Area. Three different test cryostats will house the modules, which can also be exposed to particle beams for calibration purposes. The three cryostats share a common liquid argon and liquid nitrogen distribution system. The system is rather complex since it has to allow operations of the three cryostats at the same time. Liquid nitrogen is used as cold source for both the cool-down of the cryostats and for normal operation of the cryostats filled with liquid argon.
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