Radiation Tolerance Tests of Ultrasonic Oxygen Deficiency Sensors

The Large Hadron Collider (LHC), presently under construction at CERN, will contain about 96 tons of high-density helium (liquid and supercritical), mostly located in the underground components of the LHC machine. To detect a dangerous decrease of oxygen concentration in the atmosphere caused by a potential release of helium, the Oxygen Deficiency Hazard Detection system will be applied for the LHC operation in the tunnel and other selected areas. The oxygen concentration is derived on the assumption that the gas added to the air is helium alone. A novel concept of oxygen deficiency detection system, built at the Wroclaw University of Technology (WUT) in Poland, allows verifying the oxygen concentration in the air by means of sound velocity measurements. The paper describes the design and functionality of two prototypes of ultrasonic ODH detection system tested by the WUT. In order to qualify the systems to be used in the LHC tunnel, the stability of ultrasonic transducers and electronics has been checked under radiation in an environment similar to that predicted for the LHC. At the beginning both systems have been tested in TCC2 test radiation zone at CERN. The complementary test, was performed in Institute of Atomic Energy (IEA) in Poland.