One of the key parts of this cryo-refrigerator is the porous media called the regenerator which stores the energy of the working gas. In order to enhance its storage capacity, we developed new structures with specific heat anomalies in the 4K - 20K temperature range (cf. Fig.) and we put them in the regenerator. Starting from 20K, we reached an ultimate temperature near 3.8K and the system is able to produce 15mW at 4.5K.
This new technological building block will be integrated in a complete system and could be connected to already existing sub-Kelvin coolers in order to propose new space mission concepts without helium bath (a helium bath is consumed day by day, after depletion, the space mission is over, as for the Herschel mission) for long-life astrophysics missions such as the Athena (Advanced Telescope for High ENergy Astrophysics) mission of the European Space Agency.
An important support for the development of the regenerator structures with specific heat anomalies has been provided by Gérard LAPERTOT (SPSMS/Imapec), Stéphanie Pouget (SGX), Christophe Marin (SPSMS/Imapec) and Daniel Braithwaite (SPSMS/Imapec).
Specific heat ratio of the structures.