The New Iram Kid Array-2 (NIKA2) is a next generation camera for continuum millimeter wave observations currently being developed by the NIKA2 consortium. This camera will be installed at the focal plane of the IRAM 30m telescope in Sierra Nevada (Spain) in 2015, replacing the already successful NIKA prototype that opened to external observers in February 2014. With respect to the prototype, NIKA2 will represent an important step forward, thanks to major improvements in all of its key components.

Detectors: the NIKA2 focal plane will be fully sampled using Kinetic Inductance Detectors (KID), a novel superconducting detectors technology that provides at the same time high sensitivity and ease of multiplexing. Dual color imaging will be obtained thanks to the simultaneous readout of a 1000 pixels array at 2mm and 2x2000 pixels arrays at 1.2mm. The two arrays at 1.2mm allow the measurement of the linear polarization in this band. A series of dedicated electronics boards named NIKEL will be used to acquire the astronomical signal. Each of them is capable of exciting and reading out up to 400 kids simultaneously using one single coaxial line. The goal point source sensitivities are around 10 and 15 mJy·sqrt(s) at 2mm and 1.2mm respectively.

Cryostat: to cool down the detectors to their ideal working temperature (~100mK) a dedicated cryostat has been designed and fabricated. It is based on two Pulse Tube coolers and a closed cycle 3He/4He dilution refrigerator. Its impressive dimensions (2.3m length and 1m diameter, for a total weight approaching one ton) are dictated by the space needed to host the arrays and the re-imaging optics, and for splitting the optical beam to illuminate each one of the three arrays. The cryostat is currently under test, and has already been successfully cooled down to below 100mK in May 2014.

Optics: the optics chain has been designed in order to have a much larger Field of View (FoV), which will be 6.5 arcmin in diameter. This will be fully sampled at 0.75 F*Lambda. A dichroic is used to split the two optical bands, and a wire grid further splits the 1mm band to divide its two perpendicular polarizations. In front of each array a dedicated optical filter is used to accurately define the bands.

As of today, the NIKA2 development has proceeded according to the timeline. Its installation and commissioning are thus planned to start during the 2015 Summer. The combination of arrays of state-of-the-art detectors with the high resolution and large FoV provided by the IRAM 30m telescope, will make NIKA2 a unique tool for astronomers worldwide.


NIKA2 in a nutshell

The NIKA2 cryostat

The 2mm KID matrix