Heat Transfer Studies of Cryogel® Z under Mechanical Pressure for Large-Scale Insulation of Particle Detectors

The development of detectors for hadron-hadron colliders is one of the major challenges in the evolution process of the Future Circular Collider project at CERN. The ultrathin solenoid concept aims at significantly improving the magnetic field distribution efficiency within the detectors. Its design calls for a thermal insulation of the cold mass at 5K that has to offer structural support while being sufficiently transparent for particle detection. The insulation material Cryogel ®Z shows promising properties in this context. This thesis comprises the development of an experimental test setup that allows the evaluation of the Cryogel Z’s eligibility for application in an ultrathin solenoid and first test results. The generation of two low-temperature levels by a pulse-tube refrigerator and the vacuum vessel were preconditions to the design of the experimental setup. Thus, after acquiring detailed performance data of the novel pulse-tube refrigerator with a given test stand, numerical simulations were conducted using these data to determine feasible design dimensions for the experimental setup. Based on the obtained dimensioning results, the new setup was designed in detail, commissioned and installed. With this setup, first experiments were conducted using heat meters which determined heat loads through the Cryogel Z on the cold mass and an intermediate thermal shield, whose temperature was varied between 40K and 80 K. In analogy with the conditions in the ultrathin solenoid, the Cryogel Z was compressed by a 1 bar mechanical pressure load throughout the conducted experiments. The obtained experimental results revealed the heat load values per square meter of 7-layer Cryogel Z insulation on both the cold mass and the thermal shield for shield temperatures of 40 K, 53K and 80 K. Considering the results obtained in this work and the coefficients of performance of the existing cryoplants at CERN, a determination of an optimum thermal shield temperature of 46...47K was possible.