Speakers
Description
INTA Thermal testing and Model Correlation of Cryostat Thermal Straps
M. Fernandez-Sanchez1, J. Azcue1, M. Reina1, L. Bastide2, A. García-Llases2, J. Gómez-Elvira1, A. Balado1
1 INTA, Ctra. Torrejón-Ajalvir Km.4 28850-Torrejón de Ardoz, Spain
2 ISDEFE Consultant at INTA, Ctra. Torrejón-Ajalvir Km.4 28850-Torrejón de Ardoz, Spain
ABSTRACT
Scientific missions to study the Hot Universe, the effect of Active Galactic Nuclei (AGN) in the intra-cluster medium (ICM) and by obtaining the distribution and properties of the warm/hot baryonic filaments in the intergalactic medium, does use of X-ray spectrometry, which detectors are transition-edge sensor (TES) superconductor detectors operating at millikelvin. That goal could be reached with a cryostat refrigerated by means of cryocoolers up to 2 K, while the subKelvin refrigeration is part of the Focal Plane Assembly, where the TES are.
DCS (Detector Cooling System) is a demonstrator of such cryostats, designed to test the performance and the functionality of a cryogen free coolers chain. The DCS is composed by two main assemblies: Focal Plane Assembly (FPA) and a Dewar (the pressure vessel structure and radiative shields cooled by Pulse tube and Joule-Thompson coolers), which creates a 2K environment for the FPA, where an ADR cools the detectors. The radiation is managed by the intermediate cooled shields, while the conduction goes through two “radial” paths: mechanical straps and harness. In both cases, there are a number of thermal anchors with the internal cooled shields. Thus, gradually, its temperatures are decreased and heat fluxes removed by the coolers.
Each mechanical strap is formed by four links of composite materials (GFRP and CFRP) manufactured by INTA Composites Area. The materials of the links was selected according to structural and thermal requirements, first Eigen frequencies above 60Hz, and a heat load on 2K enclosure lower than 20mW. Thus, the material distribution is GFRP for high temperature stages (300K to 30K) and CFRP in low temperature stages (30K to 2K).
To verify the design, a dedicated thermo-mechanical test was performed, submitting the straps to temperature gradients and mechanical stress similar to the expected. A dedicated set-up was designed and two straps were tested at their temperature range, with the hot end of the strap at 300K, while the cold end was at 30K due to the facility constrains. Straps under a tension of 6.000N applied at room temperature, according the DCS design. Active thermal control, insulating shields and ancillary elements, were used to create the thermal environment, and Silicon-Diode thermal sensors used to measure the strategic spots. Moreover, strain gauge was used before the cool down to measure the deformation due to the tension, which were checked before and after the test to discard any loss of tension due to temperature changes.
This paper describes the test set-up and thermal model done to correlate the DCS Mechanical Strap performances under the foreseen environment, and the results of such correlation.
