The design of a concentric cylinder calorimeter for measuring the apparent thermal conductivity of MLI blankets is presented. Unlike similar devices where a liquid cryogen is used to control the cold boundary temperature and the cryogen boil-off rate is used to obtain the heat transfer through blanket, the design presented in this paper utilizes mechanical refrigerators to control the boundary temperatures and a heat rate meter to determine the heat load. This approach ensures two unique features of the apparatus. First, the use of cryocoolers enables the user to set the boundary temperatures anywhere within the operating range of the refrigerators and therefore permits a wide range of temperature and temperature differences with the measurement. The other unique feature is that the total heat transfer through the blanket is obtained by measuring the heat conducted along a cold cylinder support rod of known thermal conductivity. To determine the absolute thermal conductivity, a calibration is needed to eliminate the temperature related effects on the support rod.
Abstract. Multilayer Insulation (MLI) blankets for MRI cryostats were experimentally tested and modeled. These blankets were tested using a high accuracy experimental apparatus that allows for set temperature boundary conditions that are not linked to liquid cryogen temperatures. Additional testing was also done on blanket performance when compressed. The experimental data was modeled and the results show good agreement. The model uses only design parameters to determine the thermal performance of the blanket. Using this model, a new blanket was designed, tested, and implemented in production.
Here we present details of an experiment for verifying the liquid helium vessel relief device for the Alpha Magnetic Spectrometer-02 (AMS-02). The relief device utilizes a series of rupture discs designed to open in the event of a vacuum failure of the AMS-02 cryogenic system. A failure of this type is classified to be a catastrophic loss of insulating vacuum accident. This apparatus differs from other approaches due to the size of the test volumes used. The verification apparatus consists of a 250 liter vessel used for the test quantity of liquid helium that is located inside a vacuum insulated vessel. A large diameter valve is suddenly opened to simulate the loss of insulating vacuum in a repeatable manner. Pressure and temperature vs. time data are presented and discussed in the context of the AMS-02 hardware configuration.
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