To study the hot and energetic universe, the European Space Agency (ESA) is developing the ATHENA L-class mission. One of its instruments, the X-Ray Integral Field Unit (X-IFU) will reach very high sensitivity thanks to detector temperature as low as 50 mK. In 2022, ATHENA has been fully reconfigured and X-IFU uses now a passively cooled 50 K cryostat with thermal interfaces at 20 K and at 5 K thanks to the use of a mechanical cooler.

To reach the lowest temperature stages, a multistage adiabatic demagnetization refrigerator (ADR) system is being developed at CEA. From a 5 K interface, a succession of 5 ADR stages provides cooling interface at 1.8 K, 320 mK and 50 mK for the focal plane assembly (FPA). In addition to the demanding cooling requirements, due to the vicinity to the FPA, the multistage ADR cooler has stringent requirement specifically in term of magnetic sensitivity.

A demonstration model of the 5 stage ADR has been assembled and tested. The first purpose of this model is to validate the functional performances as well as our numerical models. Then, the prototype will be integrated in the 4K – core DM model of the X-IFU instrument at CNES for coupling with the FPA. This talk will present the DM design and tests results, including constraints linked to the integration in X-IFU. Finally, we will present the next steps of this long-term project.

Keywords
Cryocoolersa|ADR|ATHENA