A Central Rapidity Straw Tracker and Measurements on Cryogenic Components for the Large Hadron Collider

Sammanfattning: This thesis is divided into two parts in which two different aspects of the Large Hadron Collider (LHC) Project are discussed. The first part describes the design of a transition radiation tracker (TRT) for the inner detector in ATLAS. In particular, the barrel part was studied in detail. The barrel TRT consists of 52 544 1.5-m-long proportional tubes (straws), parallel to the beam axis and each with a diameter of 4 mm. The detector is divided into three module layers with 32 modules in each layer. The preparatory study comprises: module size optimization, mechanical and thermal calculations, tracking performance and material budget studies. A 0.5-m-long barrel-module prototype has been built and tested in order to validate the design. Measurements have been performed on the temperature distribution inside the detector in order to calibrate the thermal calculations and to verify the cooling scheme of the modules. Additional measurements have been performed, e.g. on leak tightness, wire tension, high voltage and cross-talk between channels. Finally, the transition radiation performance of two different fibre radiators was measured with the 0.5 m barrel prototype and, based on the performance of individual straws, the electron identification performance was estimated for the full barrel TRT. The second part deals with the cryogenic system for the LHC superconducting magnets. They will work at a temperature below 2 K and it is essential to understand the thermal behaviour of the individual cryogenic components in order to assess the insulating properties of the magnet cryostat. The work involves the design of two dedicated heat-inleak measuring benches for cryogenic components, and the results from heat-inleak measurements on two different types of cryogenic components are reported. Measurements were carried out on various support-post prototypes and on one quench-relief-valve prototype. The heat loads were measured with specially developed heatmeters and cross measured with calorimetric measurements and standard boil-off methods. The measured heat loads were compared with analytical calculations.