867 research outputs found
Prototype high angular resolution LEKIDs for NIKA2
The current resolution of the NIKA2 260 GHz arrays is limited by the
inductor size on the individual pixels. In view of future
updates of the instrument, we have developed a prototype array with smaller
pixels that is experimentally compared to the current pixel design. We find an
in-lab improvement increase of the angular resolution of 8%, promising an
on-sky FWHM resolution of 10.2" using this new pixel design.Comment: 6 pages, 4 figures, submitted to Journal of Low Temperature Detecto
Uniform non-stoichiometric titanium nitride thin films for improved kinetic inductance detector array
We describe the fabrication of homogeneous sub-stoichiometric titanium
nitride films for microwave kinetic inductance detector (mKID) arrays. Using a
6 inch sputtering target and a homogeneous nitrogen inlet, the variation of the
critical temperature over a 2 inch wafer was reduced to <25 %. Measurements of
a 132-pixel mKID array from these films reveal a sensitivity of 16 kHz/pW in
the 100 GHz band, comparable to the best aluminium mKIDs. We measured a noise
equivalent power of NEP = 3.6e-15 W/Hz^(1/2). Finally, we describe possible
routes to further improve the performance of these TiN mKID arrays.Comment: 7 pages, 4 figures, submitted to Journal of low temperature physics,
Proceedings of LTD-1
Optimisation de détecteurs pour l'astronomie du rayonnement X : développement de jonctions supraconductrices pour l'isolation thermique dans les interconnexions
Future of the next camera onboard space observatories implies a major enhancement in number of pixelsand a very low operative temperature (below 0.1 K). In this evolution, the large number of output wiresfrom the cool detector is often responsible of the most important thermal load onto the cold bath(cryostat).In this context, the thermal insulation between the different detection circuits is the bottleneck for thesecameras. An innovative technological component, protected by a patent, has been developed to tackle thisproblem. This device has both an excellent electrical resistivity and a very high thermal resistivity.The proposed solution is a stack of thin superconducting layers at electrical interconnections.The thermal resistance at each interface relies on the elastic properties of the materials used, the quality ofthe interfaces and temperature. The AMM model used in conjunction with the measured materialcharacteristics allows a theorical estimation of the thermal resistance per interface. The measurementsundertaken with superconducting connections with very high thermal resistivity are very well describedby this AMM model. We have measured thermal resistances as high as 3.3 105 K/W @ 200 mKfor a multilayer of 62 interfaces built with titaniun nitride and niobium alternatively on a 16 mm2 array.In the conditions foreseen for a 4000 micro-calorimeters camera operating at 50 mK in X-rays,this multilayer technique should allow a thermal load onto the cold bath that is much lower that 1 mWfor more than 8000 contacts.L’avenir des nouvelles caméras embarquées pour l’astrophysique spatiale semble passer par unaccroissement du nombre de pixels et un fonctionnement à très basse température (en dessous de 0,1 K).Avec cette évolution, le nombre important de fils en sortie du détecteur refroidi représente souvent lacharge thermique prédominante sur la source froide (cryostat).Dans ce contexte, l’isolation thermique entre les différents circuits de détection est un point crucial pources caméras. Une brique technologique innovante a été développée pour apporter une solution présentantune excellente conduction électrique couplée à une grande isolation thermique. Cette innovation,protégée par un brevet, permet de résoudre cet apparent paradoxe. La solution proposée consiste enl’empilement d’un grand nombre de couches minces de matériaux supraconducteurs dans lesinterconnexions.La résistance thermique à chaque interface est dépendante des propriétés élastiques des matériaux,de la qualité des interfaces et de la température à laquelle le système fonctionne. A très basse température,le modèle AMM, couplé aux mesures des caractéristiques des matériaux composants la multicouche,permettent une estimation théorique de la résistance thermique pour une interface. Les mesures effectuéesavec les liaisons supraconductrices à forte résistivité thermique concordent avec les estimationsthéoriques. Nous avons ainsi pu mesurer des résistances thermiques de l’ordre de 3,3.105 K/W à 200 mKpour une multicouche composée d’une succession (62 interfaces) de couches minces de nitrure de titaneet de niobium sur une surface de 16 mm2. Dans les conditions d’utilisation prévues pour une camérarayons X de 4000 pixels microcalorimétriques, l’utilisation de cette brique technologique devrait assurerune charge thermique sur la source froide (à 50 mK) très inférieure au μW pour plus de 8000 pointsde contact. Ce dispositif pourra être utilisé à l’avenir dans nombre de projets cryogéniques, lorsqu’une excellenteisolation thermique associée à une excellente conduction électrique sera recherchée
Niobium Silicon alloys for Kinetic Inductance Detectors
We are studying the properties of Niobium Silicon amorphous alloys as a
candidate material for the fabrication of highly sensitive Kinetic Inductance
Detectors (KID), optimized for very low optical loads. As in the case of other
composite materials, the NbSi properties can be changed by varying the relative
amounts of its components. Using a NbSi film with T_c around 1 K we have been
able to obtain the first NbSi resonators, observe an optical response and
acquire a spectrum in the band 50 to 300 GHz. The data taken show that this
material has very high kinetic inductance and normal state surface resistivity.
These properties are ideal for the development of KID. More measurements are
planned to further characterize the NbSi alloy and fully investigate its
potential.Comment: Accepted for publication on Journal of Low Temperature Physics.
Proceedings of the LTD15 conference (Caltech 2013
Lumped element kinetic inductance detectors maturity for space-borne instruments in the range between 80 and 180 GHz
This work intends to give the state-of-the-art of our knowledge of the
performance of LEKIDs at millimetre wavelengths (from 80 to 180~GHz). We
evaluate their optical sensitivity under typical background conditions and
their interaction with ionising particles. Two LEKID arrays, originally
designed for ground-based applications and composed of a few hundred pixels
each, operate at a central frequency of 100, and 150~GHz (
about 0.3). Their sensitivities have been characterised in the laboratory using
a dedicated closed-circle 100~mK dilution cryostat and a sky simulator,
allowing for the reproduction of realistic, space-like observation conditions.
The impact of cosmic rays has been evaluated by exposing the LEKID arrays to
alpha particles (Am) and X sources (Cd) with a readout sampling
frequency similar to the ones used for Planck HFI (about 200~Hz), and also with
a high resolution sampling level (up to 2~MHz) in order to better characterise
and interpret the observed glitches. In parallel, we have developed an
analytical model to rescale the results to what would be observed by such a
LEKID array at the second Lagrangian point.Comment: 7 pages, 2 tables, 13 figure
A horn-coupled millimeter-wave on-chip spectrometer based on Lumped Element Kinetic Inductance Detectors
Context. Millimetre-wave astronomy is an important tool for both general
astrophysics studies and cosmology. A large number of unidentified sources are
being detected by the large field-of-view continuum instruments operating on
large telescopes.
Aims. New smart focal planes are needed to bridge the gap between large
bandwidth continuum instruments operating on single dish telescopes and the
high spectral and angular resolution interferometers (e.g. ALMA in Chile, NOEMA
in France). The aim is to perform low-medium spectral resolution observations
and select a lower number of potentially interesting sources, i.e.
high-redshift galaxies, for further follow-up.
Methods. We have designed, fabricated and tested an innovative on-chip
spectrometer sensitive in the 85-110~GHz range. It contains sixteen channels
selecting a frequency band of about 0.2 GHz each. A conical horn antenna
coupled to a slot in the ground plane collects the radiation and guides it to a
mm-wave microstrip transmission line placed on the other side of the
mono-crystalline substrate. The mm-wave line is coupled to a filter-bank. Each
filter is capacitively coupled to a Lumped Element Kinetic Inductance Detector
(LEKID). The microstrip configuration allows to benefit from the high quality,
i.e. low losses, mono-crystalline substrate, and at the same time prevents
direct, i.e. un-filtered, LEKID illumination.
Results. The prototype spectrometer exhibit a spectral resolution R = lambda
/ Delta_lambda = 300. The optical noise equivalent power is in the low
1E-16W/sqrt(Hz) range for an incoming power of about 0.2pW per channel. The
device is polarisation-sensitive, with a cross-polarisation lower than 1% for
the best channels.Comment: Submitted to Astronomy & Astrophysic
Bi-layer Kinetic Inductance Detectors for space observations between 80-120 GHz
We have developed Lumped Element Kinetic Inductance Detectors (LEKID)
sensitive in the frequency band from 80 to 120~GHz. In this work, we take
advantage of the so-called proximity effect to reduce the superconducting gap
of Aluminium, otherwise strongly suppressing the LEKID response for frequencies
smaller than 100~GHz. We have designed, produced and optically tested various
fully multiplexed arrays based on multi-layers combinations of Aluminium (Al)
and Titanium (Ti). Their sensitivities have been measured using a dedicated
closed-circle 100 mK dilution cryostat and a sky simulator allowing to
reproduce realistic observation conditions. The spectral response has been
characterised with a Martin-Puplett interferometer up to THz frequencies, and
with a resolution of 3~GHz. We demonstrate that Ti-Al LEKID can reach an
optical sensitivity of about ~ (best pixel), or
~ when averaged over the whole array. The optical
background was set to roughly 0.4~pW per pixel, typical for future space
observatories in this particular band. The performance is close to a
sensitivity of twice the CMB photon noise limit at 100~GHz which drove the
design of the Planck HFI instrument. This figure remains the baseline for the
next generation of millimetre-wave space satellites.Comment: 7 pages, 9 figures, submitted to A&
NIKEL_AMC: Readout electronics for the NIKA2 experiment
The New Iram Kid Arrays-2 (NIKA2) instrument has recently been installed at
the IRAM 30 m telescope. NIKA2 is a state-of-art instrument dedicated to
mm-wave astronomy using microwave kinetic inductance detectors (KID) as
sensors. The three arrays installed in the camera, two at 1.25 mm and one at
2.05 mm, feature a total of 3300 KIDs. To instrument these large array of
detectors, a specifically designed electronics, composed of 20 readout boards
and hosted in three microTCA crates, has been developed. The implemented
solution and the achieved performances are presented in this paper. We find
that multiplexing factors of up to 400 detectors per board can be achieved with
homogeneous performance across boards in real observing conditions, and a
factor of more than 3 decrease in volume with respect to previous generations.Comment: 21 pages; 16 figure
Lumped Element Kinetic Inductance Detectors for space applications
Kinetic Inductance Detectors (KID) are now routinely used in ground-based
telescopes. Large arrays, deployed in formats up to kilopixels, exhibit
state-of-the-art performance at millimeter (e.g. 120-300 GHz, NIKA and NIKA2 on
the IRAM 30-meters) and sub-millimeter (e.g. 350-850 GHz AMKID on APEX)
wavelengths. In view of future utilizations above the atmosphere, we have
studied in detail the interaction of ionizing particles with LEKID (Lumped
Element KID) arrays. We have constructed a dedicated cryogenic setup that
allows to reproduce the typical observing conditions of a space-borne
observatory. We will report the details and conclusions from a number of
measurements. We give a brief description of our short term project, consisting
in flying LEKID on a stratospheric balloon named B-SIDE.Comment: To appear in the SPIE 2016 Proceeding
Very low resistance Al/Cu joints for use at cryogenic temperatures
We present two different techniques for achieving low resistance (20 n) contacts between copper and aluminium at cryogenic temperatures. The
best method is based on gold plating of the surfaces in an e-beam evaporator
immediately after Ar plasma etching in the same apparatus, yielding resistances
as low as 3 n that are stable over time. The second approach
involves inserting indium in the Al/Cu joint. For both methods, we believe key
elements are surface polishing, total removal of the aluminum oxide surface
layer, and temporary application of large (typ. 11 kN) compression forces. We
believe the values for gold plated contacts are the lowest ever reported for a
Cu/Al joint of a few . This technology could simplify the
construction of thermal links for advanced cryogenics applications, in
particular that of extremely low resistance heat switches for nuclear
demagnetization refrigerators.Comment: Accepted by Journal of Low Temperature Physic
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