The New IRAM KID Arrays (NIKA): a continuum camera for millimeter wave astronomy – NIKA

In May 2011, IRAM (Institut de Radioastronomie Millimétrique) issued a call for tender for the next generation continuum instrumentation of the 30-m telescope at Pico Veleta (Spain). The NIKA (New IRAM KIDs Arrays) consortium answered with a detailed proposal to build a large-format, dual-color (150GHz = 2mm and 240GHz = 1.25mm) camera. This proposal was examined by the IRAM Scientific Advisory Committee who has recently issued a positive recommendation for the NIKA camera. The instrument will be based on the new and extremely promising KIDs (Kinetic Inductance Detectors) technology. The technological program is led by French researchers at the Institut Néel and LPSC (Grenoble). The French part of the collaboration is completed by IPAG (Grenoble), IAS (Orsay), CEA-IRFU (Saclay) and IRAP (Toulouse). IRAM-Grenoble is actively participating to the project, contributing with 50% co-financing and their expertise in the field of detectors design/fabrication, electronics and data analysis. At the international level, this French consortium will collaborate with the University of Cardiff (UK), the Netherlands Institute for Space Research – SRON and The University of Roma La Sapienza (Italy). The international collaborators will provide in particular, on independent funding, the optical filters and the beam splitter. The NIKA camera will be based on a prototype instrument already tested at the IRAM 30-m telescope in 2009, 2010 and 2011. These successful technical/scientific runs allowed for the first time to assess the viability of the KIDs technology for ground-based mm-wave observations. In particular, the 2011 dual-band prototype exhibited a state-of-the-art performance at 150 GHz. The instrument will incorporate a continuous close-cycled dilution refrigerator with a base temperature of 100 mK, cold reimaging optics and filters designed to sample a 6 arc minute field of view simultaneously in at least 2 channels centered at wavelengths of 1.25 and 2 mm. The baseline detector focal plane units will consist of arrays of KIDs with a pixel spacing of 0.75 f*lambda giving approximately 1000 detectors at 2 mm and 3000 detectors at 1.25 mm. These detectors will be read out with a maximum of 16 cold amplifiers, and the same number of coaxial cables pairs. On top of that, the implementation of a “Polarization Channel” allowing linearly polarized continuum emission to be measured in at least the 1.2 mm band is being planned as a future upgrade. The implementation of a third imaging band in the sub-mm range (850 micron) is also envisaged as a second-priority upgrade. In the present proposal, we request ANR support for the construction of the baseline instrument (dual-band, pure imaging, as stated by IRAM in their call). Funding for the “Polarization Channel” upgrade has already been obtained by CEA-IRFU (Saclay) as part of an ERC European contract. The baseline instrument will be designed to be fully compatible with both upgrades. The duration of this ANR program is three years, mainly dedicated to an intense instrumental development: cryostat fabrication, detectors and electronics design, fabrication and testing. The last semester is mainly characterized by the instrument commissioning at the Pico Veleta telescope. At the end of the ANR project, the NIKA camera will become a powerful facility instrument (e.g. the gain in mapping speed compared to the previous generation continuum instrument is 40-100) which will benefit the entire community of astronomers using IRAM.