Development of superconducting flexible cables for 4th generation Cosmic Microwave Background experiments – CMB-FLEX

Cosmology has made tremendous progress in the last twenty-five years in determining accurately the matter and energy content of the Universe. One of the major remaining questions is the generation of the density fluctuations that gave birth to the structures (galaxies, clusters of galaxies) that make up the Universe today. These fluctuations would come from Inflation, a phase of exponential expansion that took place during a tiny fraction of a second, at the beginning of the Big-Bang. To prove Inflation, it is necessary to observe the polarization of the Cosmic Microwave Background (CMB) with a sensitivity at least five times higher than the current generation of experiments, known as 3rd generation. This high sensitivity requires to observe the sky with half a million detectors cooled at 100mK that have to be connected to their electronics. For this, two wires per detector, that is one million wires in total, will have to be manufactured under the form of about 16,000 cables containing 160 wires each. Today, no one in the world is able to produce these cables with the required characteristics (flexible, superconducting, compact, reproducible, reliable) to achieve the technical and scientific objectives of the 4th generation experiments. CEA Paris-Saclay has designed prototypes for space missions that fulfill part of the required characteristics (flexible, superconducting, compact). The objective of this project is to adapt the CEA prototypes specifically to CMB experiments, to study in detail their characteristics as well as their defects in order to improve their reproducibility and their reliability. At the end of the project, the designed cables should have all the required characteristics, and their mass production for the 4th generation CMB experiments can be undertaken. These cables are a key element of the detection chain without which the nominal sensitivity, and consequently the scientific objectives, cannot be achieved.