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The superconducting magnets of the Large Hadron Collider (LHC) will be cooled at 1.9 K by distributed cooling loops working with saturated two-phase superfluid helium flowing in 107 m long bayonet heat exchangers located in each magnet cold-mass cell. The temperature of the magnets could be difficult to control because of the large dynamic heat load variations. Therefore, it is foreseen to measure the heat exchangers pressure to feed the regulation loops with the corresponding saturation temperature. The required uncertainty of the sub-atmospheric saturation pressure measurement shall be of the same order of the one associated to the magnet thermometers, in pressure it translates as ±5 Pa at 1.6 kPa. The transducers shall be radiation hard as they will endure, in the worst case, doses up to 10 kGy and 1015 neutrons·cm-2 over 10 years. The sensors under evaluation were installed underground in the dump section of the SPS accelerator with a radiation environment close to the one expected for the LHC. The monitoring equipment was installed in a remote radiation protected area. This paper presents the results of the radiation qualification campaign with emphasis on the reliability and accuracy of the pressure sensors under the test conditions. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The complete procedure to calibrate thermometers is a complex process, especially when several thousand semiconductor-type thermometers are used and must be individually calibrated, as in the case of the instrumentation of the new Large Hadron Collider (LHC) machine at CERN. Indeed, the similarity of the characteristics of semiconducting thermometers is more limited than that of wire-wound thermometers. The span of the characteristics spread can appear as a homogeneous set, or can show clusters (groups) of characteristics. In the latter case, one of the reasons for clustering may be the fabrication process by batches of numerous devices on the same wafer. Consequently, the detection of the groups can be useful, from the supplier point of view, to give information relevant to improving the fabrication uniformity. From the user point of view, it is useful for making a guess of the possible thermometer stability with time, when this is a must, as in the LHC case. In fact, thermometers showing characteristics outlying or in small clusters should be considered to be potentially anomalous. In addition, the identification of anomalous groups allows the detection of artifacts due to the experimental process. For a large number of thermometers, this analysis requires the use of automated procedures and, consequently, automated decisions that avoid false effects. The paper describes the mathematical methodology adopted for the identification of the clusters, based on the mixed-effect modeling of the thermometer characteristics. © 2003 American Institute of Physics [ABSTRACT FROM AUTHOR]