50 mK cooling solution with an ADR precooled by a sorption cooler

International audienceCEA/SBT is currently developing a 2.5 K-50 mK cooling solution composed of a small demagnetization refrigerator (ADR) precooled by a sorption cooler, equivalent to the high temperature stage of a two-stage ADR system. Thanks to the use of this dual technology, a low weight cooler able to reach 50 mK with a heat sink up to 2.5 K can be designed. Because the sorption cooler is probably the lightest solution to produce sub-Kelvin temperatures, these developments allow us to propose a solution to face the drastic reduction in the mass budget of space missions like SPICA or IXO. The European Space Agency (ESA) is funding the development of an engineering model able to produce 1 lW net heat lift at 50 mK. It is sized so that the sorption cooler provides an additional 10 lW at 300 mK. The ESA main requirements are an autonomy of more than 24 h and a recycling time smaller than 8 h. We present the design of the system able to meet these requirements as well as the expected performances and preliminary measurements

Magnetic anisotropy and the shape memory phase transition in Ni52Mn26Ga22

Torque measurements of magnetocrystalline anisotropy energies, made on (1 0 0) and (1 1 0) oriented planar disc samples of the shape memory alloy Ni52Mn26Ga22 as a function of temperature and applied directional field cooling are reported. The results confirm small values for the anisotropy constants in the austenite phase (Phys. Rev. B 65 (2002) 134422). Optical observations reveal the influence of applied stresses and magnetic fields on the mobility of the phase transition and twin boundaries. Lorentz mode TEM observations from a (1 1 0) planar foil reveal the interactions between magnetic and anti-phase domain boundaries as the specimen is thermally cycled through the transition temperature

Versatile Device for the Study of Coupling Properties in Multifunctional Materials. Example: Ni-(Co)-Mn-In Heusler Materials

International audienceWe report on a versatile experimental setup for the study of the electro-magneto-elastothermal coupling for bulk materials having coupling properties. The setup enables measurement of stress and electrical resistivity in a 80 K-450 K temperature range under controlled uniaxial pressure in a magnetic field up to 8 T. The strong influence of uniaxial pressure and magnetic field on strain and transport properties is shown for Ni-Co-Mn-In Heusler single crystal material. Phase transformation, magnetostress and Magnetic Field Induced Phase Transformation and elastocaloric effect can be estimated using this versatile setup. This device is very complementary to the studies focused on the modeling of Thermo-Electro-Magneto-Mechanical behavior for functional materials

The NIKA2 Instrument at 30-m IRAM Telescope: Performance and Results

The New IRAM KID Arrays 2 (NIKA2) consortium has just finished installing and commissioning a millimetre camera on the IRAM 30-m telescope. It is a dual-band camera operating with three frequency-multiplexed kilo-pixels arrays of lumped element kinetic inductance detectors (LEKID) cooled at 150 mK, designed to observe the intensity and polarisation of the sky at 260 and 150 GHz (1.15 and 2 mm). NIKA2 is today an IRAM resident instrument for millimetre astronomy, such as intracluster medium from intermediate to distant clusters and so for the follow-up of Planck satellite detected clusters, high redshift sources and quasars, early stages of star formation and nearby galaxies emission. We present an overview of the instrument performance as it has been evaluated at the end of the commissioning phase