Development of Lumped Element Kinetic Inductance Detectors for the W-Band

We are developing a Lumped Element Kinetic Inductance Detector (LEKID) array able to operate in the W-band (75-110 GHz) in order to perform ground-based Cosmic Microwave Background (CMB) and mm-wave astronomical observations. The W-band is close to optimal in terms of contamination of the CMB from Galactic synchrotron, free-free, and thermal interstellar dust. In this band, the atmosphere has very good transparency, allowing interesting ground-based observations with large (>30 m) telescopes, achieving high angular resolution (<0.4 arcmin). In this work we describe the startup measurements devoted to the optimization of a W-band camera/spectrometer prototype for large aperture telescopes like the 64 m SRT (Sardinia Radio Telescope). In the process of selecting the best superconducting film for the LEKID, we characterized a 40 nm thick Aluminum 2-pixel array. We measured the minimum frequency able to break CPs (i.e. $h\nu=2\Delta\left(T_{c}\right)=3.5k_{B}T_{c}$) obtaining $\nu=95.5$ GHz, that corresponds to a critical temperature of 1.31 K. This is not suitable to cover the entire W-band. For an 80 nm layer the minimum frequency decreases to 93.2 GHz, which corresponds to a critical temperature of 1.28 K; this value is still suboptimal for W-band operation. Further increase of the Al film thickness results in bad performance of the detector. We have thus considered a Titanium-Aluminum bi-layer (10 nm thick Ti + 25 nm thick Al, already tested in other laboratories), for which we measured a critical temperature of 820 mK and a cut-on frequency of 65 GHz: so this solution allows operation in the entire W-band.Comment: 16th International Workshop on Low Temperature Detectors, Grenoble 20-24 July 2015, Journal of Low Temperature Physics, Accepte

The NIKA instrument: results and perspectives towards a permanent KID based camera for the Pico Veleta observatory

The New IRAM KIDs Array (NIKA) is a pathfinder instrument devoted to millimetric astronomy. In 2009 it was the first multiplexed KID camera on the sky; currently it is installed at the focal plane of the IRAM 30-meters telescope at Pico Veleta (Spain). We present preliminary data from the last observational run and the ongoing developments devoted to the next NIKA-2 kilopixels camera, to be commissioned in 2015. We also report on the latest laboratory measurements, and recent improvements in detector cosmetics and read-out electronics. Furthermore, we describe a new acquisition strategy allowing us to improve the photometric accuracy, and the related automatic tuning procedure.Comment: 24th International Symposium on Space Terahertz Technology, ISSTT 2013, April 8 to 10, 2013, Groningen, the Netherland

Latest NIKA results and the NIKA-2 project

NIKA (New IRAM KID Arrays) is a dual-band imaging instrument installed at the IRAM (Institut de RadioAstronomie Millimetrique) 30-meter telescope at Pico Veleta (Spain). Two distinct Kinetic Inductance Detectors (KID) focal planes allow the camera to simultaneously image a field-of-view of about 2 arc-min in the bands 125 to 175 GHz (150 GHz) and 200 to 280 GHz (240 GHz). The sensitivity and stability achieved during the last commissioning Run in June 2013 allows opening the instrument to general observers. We report here the latest results, in particular in terms of sensitivity, now comparable to the state-of-the-art Transition Edge Sensors (TES) bolometers, relative and absolute photometry. We describe briefly the next generation NIKA-2 instrument, selected by IRAM to occupy, from 2015, the continuum imager/polarimeter slot at the 30-m telescope.Comment: Proceedings of Low Temperature Detectors 15 (LTD-15), Pasadena, June 201

CALDER - Neutrinoless double-beta decay identification in TeO2_2 bolometers with kinetic inductance detectors

Next-generation experiments searching for neutrinoless double-beta decay must be sensitive to a Majorana neutrino mass as low as 10 meV. CUORE, an array of 988 TeO$_2$ bolometers being commissioned at Laboratori Nazionali del Gran Sasso in Italy, features an expected sensitivity of 50-130 meV at 90% C.L, that can be improved by removing the background from $\alpha$ radioactivity. This is possible if, in coincidence with the heat release in a bolometer, the Cherenkov light emitted by the $\beta$ signal is detected. The amount of light detected is so far limited to only 100 eV, requiring low-noise cryogenic light detectors. The CALDER project (Cryogenic wide-Area Light Detectors with Excellent Resolution) aims at developing a small prototype experiment consisting of TeO$_2$ bolometers coupled to new light detectors based on kinetic inductance detectors. The R&D is focused on the light detectors that could be implemented in a next-generation neutrinoless double-beta decay experiment.Comment: 8 pages, 3 figures, added reference to first result

The NIKA2 instrument, a dual-band kilopixel KID array for millimetric astronomy

NIKA2 (New IRAM KID Array 2) is a camera dedicated to millimeter wave astronomy based upon kilopixel arrays of Kinetic Inductance Detectors (KID). The pathfinder instrument, NIKA, has already shown state-of-the-art detector performance. NIKA2 builds upon this experience but goes one step further, increasing the total pixel count by a factor $\sim$10 while maintaining the same per pixel performance. For the next decade, this camera will be the resident photometric instrument of the Institut de Radio Astronomie Millimetrique (IRAM) 30m telescope in Sierra Nevada (Spain). In this paper we give an overview of the main components of NIKA2, and describe the achieved detector performance. The camera has been permanently installed at the IRAM 30m telescope in October 2015. It will be made accessible to the scientific community at the end of 2016, after a one-year commissioning period. When this happens, NIKA2 will become a fundamental tool for astronomers worldwide.Comment: Proceedings of the 16th Low Temperature Detectors workshop. To be published in the Journal of Low Temperature Physics. 8 pages, 4 figures, 1 tabl

Detection of the tSZ effect with the NIKA camera

We present the first detection of the thermal Sunyaev-Zel'dovich (tSZ) effect from a cluster of galaxies performed with a KIDs (Kinetic Inductance Detectors) based instrument. The tSZ effect is a distortion of the black body CMB (Cosmic Microwave Background) spectrum produced by the inverse Compton interaction of CMB photons with the hot electrons of the ionized intra-cluster medium. The massive, intermediate redshift cluster RX J1347.5-1145 has been observed using NIKA (New IRAM KIDs arrays), a dual-band (140 and 240 GHz) mm-wave imaging camera, which exploits two arrays of hundreds of KIDs: the resonant frequencies of the superconducting resonators are shifted by mm-wave photons absorption. This tSZ cluster observation demonstrates the potential of the next generation NIKA2 instrument, being developed for the 30m telescope of IRAM, at Pico Veleta (Spain). NIKA2 will have 1000 detectors at 140GHz and 2x2000 detectors at 240GHz, providing in that band also a measurement of the linear polarization. NIKA2 will be commissioned in 2015.Comment: SF2A Proceedings 201

Non-parametric deprojection of NIKA SZ observations: Pressure distribution in the Planck-discovered cluster PSZ1 G045.85+57.71

The determination of the thermodynamic properties of clusters of galaxies at intermediate and high redshift can bring new insights into the formation of large-scale structures. It is essential for a robust calibration of the mass-observable scaling relations and their scatter, which are key ingredients for precise cosmology using cluster statistics. Here we illustrate an application of high resolution $(< 20$ arcsec) thermal Sunyaev-Zel'dovich (tSZ) observations by probing the intracluster medium (ICM) of the \planck-discovered galaxy cluster \psz\ at redshift $z = 0.61$, using tSZ data obtained with the NIKA camera, which is a dual-band (150 and 260~GHz) instrument operated at the IRAM 30-meter telescope. We deproject jointly NIKA and \planck\ data to extract the electronic pressure distribution from the cluster core ($R \sim 0.02\, R_{500}$) to its outskirts ($R \sim 3\, R_{500}$) non-parametrically for the first time at intermediate redshift. The constraints on the resulting pressure profile allow us to reduce the relative uncertainty on the integrated Compton parameter by a factor of two compared to the \planck\ value. Combining the tSZ data and the deprojected electronic density profile from \xmm\ allows us to undertake a hydrostatic mass analysis, for which we study the impact of a spherical model assumption on the total mass estimate. We also investigate the radial temperature and entropy distributions. These data indicate that \psz\ is a massive ($M_{500} \sim 5.5 \times 10^{14}$ M$_{\odot}$) cool-core cluster. This work is part of a pilot study aiming at optimizing the treatment of the NIKA2 tSZ large program dedicated to the follow-up of SZ-discovered clusters at intermediate and high redshifts. (abridged)Comment: 16 pages, 10 figure

High angular resolution Sunyaev-Zel'dovich observations of MACS J1423.8+2404 with NIKA: Multiwavelength analysis

The prototype of the NIKA2 camera, NIKA, is an instrument operating at the IRAM 30-m telescope, which can observe simultaneously at 150 and 260GHz. One of the main goals of NIKA2 is to measure the pressure distribution in galaxy clusters at high resolution using the thermal SZ (tSZ) effect. Such observations have already proved to be an excellent probe of cluster pressure distributions even at high redshifts. However, an important fraction of clusters host submm and/or radio point sources, which can significantly affect the reconstructed signal. Here we report on <20" resolution observations at 150 and 260GHz of the cluster MACSJ1424, which hosts both radio and submm point sources. We examine the morphology of the tSZ signal and compare it to other datasets. The NIKA data are combined with Herschel satellite data to study the SED of the submm point source contaminants. We then perform a joint reconstruction of the intracluster medium (ICM) electronic pressure and density by combining NIKA, Planck, XMM-Newton, and Chandra data, focusing on the impact of the radio and submm sources on the reconstructed pressure profile. We find that large-scale pressure distribution is unaffected by the point sources because of the resolved nature of the NIKA observations. The reconstructed pressure in the inner region is slightly higher when the contribution of point sources are removed. We show that it is not possible to set strong constraints on the central pressure distribution without accurately removing these contaminants. The comparison with X-ray only data shows good agreement for the pressure, temperature, and entropy profiles, which all indicate that MACSJ1424 is a dynamically relaxed cool core system. The present observations illustrate the possibility of measuring these quantities with a relatively small integration time, even at high redshift and without X-ray spectroscopy.Comment: 15 pages, 17 figures, submitted to A&

First array of enriched Zn82^{82}Se bolometers to search for double beta decay

The R&D activity performed during the last years proved the potential of ZnSe scintillating bolometers to the search for neutrino-less double beta decay, motivating the realization of the first large-mass experiment based on this technology: CUPID-0. The isotopic enrichment in $^{82}$Se, the Zn$^{82}$Se crystals growth, as well as the light detectors production have been accomplished, and the experiment is now in construction at Laboratori Nazionali del Gran Sasso (Italy). In this paper we present the results obtained testing the first three Zn$^{82}$Se crystals operated as scintillating bolometers, and we prove that their performance in terms of energy resolution, background rejection capability and intrinsic radio-purity complies with the requirements of CUPID-0