BFORE is a high-altitude ultra-long-duration balloon mission to map the cosmic microwave background (CMB). During a 28-day mid-latitude ight launched from Wanaka, New Zealand, the instrument will map half the sky to improve measurements of the optical depth to reionization tau. This will break parameter degeneracies needed to detect neutrino mass. BFORE will also hunt for the gravitational wave B-mode signal, and map Galactic dust foregrounds. The mission will be the first near-space use of TES/mSQUID multichroic detectors (150/217 GHz and 280/353 GHz bands) with low-power readout electronics.
The next generation of cosmic microwave background (CMB) experiments, such as CMB-S4, will require large arrays of multi-chroic, polarisation-sensitive pixels. Arrays of lumped-element kinetic inductance detectors (LEKIDs) optically coupled through an antenna and transmission line structure are a promising candidate for such experiments. Through initial investigations of small prototype arrays, we have shown this compact device architecture can produce intrinsic quality factors < 10^5, allowing for MUX ratios to exceed 10^3. Moreover, we have demonstrated that additional noise from two-level systems can be reduced to an acceptable level by removing the dielectric from over the capacitive region of the KID, while retaining the microstrip coupling into the inductor. To maximise the efficiency of future focal planes, it is desirable to observe multiple frequencies simultaneously within each pixel. Therefore, we utilise the proven transmission line coupling scheme to introduce band-defining structures to our pixel architecture. Initially targeting the peak of the CMB at 150-GHz, we present a preliminary study of these narrow-band filters in terms of their spectral bandwidth and out of band rejection. By incorporating simple in-line filters we consider the overall impact of adding such structures to our pixel by investigating detector performance in terms of noise and quality factor. Based on these initial results, we present preliminary designs of an optimised mm-wave diplexer that is used to split-up the 150 GHz atmospheric window into multiple sub-bands, before reaching the absorbing length of the LEKID. We present measurements from a set of prototype filter-coupled detectors as the first demonstration towards construction of large-format, multi-chroic, antenna-coupled LEKIDs with the sensitivity required for future CMB experiments.
The mm-wavelength sky reveals the initial phase of structure formation, at all spatial scales, over the entire observable history of the Universe. Over the past 20 years, advances in mm-wavelength detectors and camera systems have allowed the field to take enormous strides forward – particularly in the study of the Cosmic Microwave Background – but limitations in mapping speeds, sensitivity and resolution have plagued studies of astrophysical phenomena. In fact, limitations due to inherent biases in the ground-based mm-wavelength surveys conducted over the last 2 decades continue to motivate the need for deeper and wider-area maps made with increased angular resolution. TolTEC is a new camera that will fill the focal plane of the 50m diameter Large Millimeter Telescope (LMT) and provide simultaneous, polarization-sensitive imaging at 2.0, 1.4, and 1.1mm wavelengths. The instrument, now under construction, is a cryogenically cooled receiver housing three separate kilo-pixel arrays of Kinetic Inductance Detectors (KIDs) that are coupled to the telescope through a series of silicon lenses and dichroic splitters. TolTEC will be installed and commissioned on the LMT in early 2019 where it will become both a facility instrument and also perform a series of 100 hour “Legacy Surveys” whose data will be publicly available. The initial four surveys in this series: the Clouds to Cores Legacy Survey, the Fields in Filaments Legacy Survey, the Ultra-Deep Legacy Survey and the Large Scale Structure Survey are currently being defined in public working groups of astronomers coordinated by TolTEC Science Team members. Data collection for these surveys will begin in late 2019 with data releases planned for late 2020 and 2021. Herein we describe the instrument concept, provide performance data for key subsystems, and provide an overview of the science, schedule and plans for the initial four Legacy Survey concepts.
SuperSpec is a new technology for millimeter and submillimeter spectroscopy. It is an on-chip spectrometer being developed for multi-object, moderate resolution (R = ~300), large bandwidth survey spectroscopy of high-redshift galaxies for the 1 mm atmospheric window. SuperSpec targets the CO ladder in the redshift range of z = 0 to 4, the [CII] 158 um line from z = 5 to 9, and the [NII] 205 um line from z = 4-7. All together these lines offer complete redshift coverage from z = 0 to 9. SuperSpec employs a novel architecture in which detectors are coupled to a series of resonant filters along a single microwave feedline instead of using dispersive optics. This construction allows for the creation of a full spectrometer occupying only 20 cm squared of silicon, a reduction in size of several orders of magnitude when compared to standard grating spectrometers. This small profile enables the production of future multi-object spectroscopic instruments required as the millimeter-wave spectroscopy field matures.
SuperSpec uses a lens-coupled antenna to deliver astrophysical radiation to a microstrip transmission line. The radiation then propagates down this transmission line where upon proximity coupled half wavelength microstrip resonators pick off specific frequencies of radiation. Careful tuning of the proximity of the resonators to the feedline dials in the desired resolving power of the SuperSpec filterbank by tuning the coupling quality factor. The half wavelength resonators are then in turn coupled to the inductive meander of kinetic inductance detectors (KIDs), which serve as the power detectors for the SuperSpec filterbank. Each SuperSpec filter bank contains hundreds of titanium nitride TiN KIDs and the natural multiplexibility of these detectors allow for readout of the large numbers of required detectors. The unique coupling scheme employed by SuperSpec allows for the creation of incredibly low volume (2.6 cubic microns), high responsivity, TiN KIDs. Since responsivity is proportional to the inverse of quasiparticle-occupied volume, this allows SuperSpec to reach the low NEPs required by moderate resolution spectroscopy to be photon limited from the best ground-based observing sites.
We will present the latest results from SuperSpec devices. In particular, detector NEPs, measured filter bank efficiency (including transmission line losses), and spectral profiles for a full ~ 300-channel filterbank. Finally, we will report on our system end to end efficiency and total system NEP.
The Mexico-UK Sub-millimetre Camera for AsTronomy (MUSCAT) is a large-format, millimetre-wave camera consisting of 1,500 background-limited lumped-element kinetic inductance detectors (LEKIDs) scheduled for deployment on the Large Millimeter Telescope (Volcán Sierra Negra, Mexico) in 2018. MUSCAT is designed for observing at 1.1 mm and will utilise the full 40 field of view of the LMTs upgraded 50-m primary mirror. In its primary role, MUSCAT is designed for high-resolution follow-up surveys of both galactic and extra-galactic sub-mm sources identified by <i>Herschel</i>. MUSCAT is also designed to be a technology demonstrator will provide the first on-sky demonstrations of novel design concepts such as horn-coupled LEKID arrays and closed continuous cycle miniature dilution refrigeration.<p> </p> Here we describe some of the key design elements of the MUSCAT instrument such as the novel use of continuous sorption refrigerators and a miniature dilutor for continuous 100-mK cooling of the focal plane, broadband optical coupling to Aluminium LEKID arrays using waveguide chokes and anti-reflection coating materials as well as with the general mechanical and optical design of MUSCAT. We will explain how MUSCAT is designed to be simple to upgrade and the possibilities for changing the focal plane unit that allows MUSCAT to act as a demonstrator for other novel technologies such as multi-chroic polarisation sensitive pixels and on-chip spectrometry in the future. Finally, we will report on the current status of MUSCAT's commissioning.
With increasing array size, it is increasingly important to control stray radiation inside the detector chips themselves. We demonstrate this effect with focal plane arrays of absorber coupled Lumped Element microwave Kinetic Inductance Detectors (LEKIDs) and lens-antenna coupled distributed quarter wavelength Microwave Kinetic Inductance Detectors (MKIDs). In these arrays the response from a point source at the pixel position is at a similar level to the stray response integrated over the entire chip area. For the antenna coupled arrays, we show that this effect can be suppressed by incorporating an on-chip stray light absorber. A similar method should be possible with the LEKID array, especially when they are lens coupled.
SPACEKIDS, a European Union FP-7 project, has recently been completed. It has focused on developing kinetic
inductance detector (KID) arrays and demonstrating their suitability for space applications at far infrared and
submillimetre wavelengths. KID arrays have been developed for both low-background (typical of astrophysical
applications) and high-background (typical of Earth-observation applications), based on performance specifications
derived from the science requirements of representative potential future missions. KID pixel and array designs have
been developed, together with readout electronics necessary to read out large numbers of pixels. Two laboratory
demonstrator systems have been built and used for comprehensive evaluation of large-format array characteristics and
performance in environments representative of both astronomy and Earth observing applications. We present an
overview of the SPACEKIDS project and a summary of its main results and conclusions.
We report on the development of scalable prototype microwave kinetic inductance detector (MKID) arrays tai- lored for future multi-kilo-pixel experiments that are designed to simultaneously characterize the polarization properties of both the cosmic microwave background (CMB) and Galactic dust emission. These modular arrays are composed of horn-coupled, polarization-sensitive MKIDs, and each pixel has four detectors: two polariza- tions in two spectral bands between 125 and 280 GHz. A horn is used to feed each array element, and a planar orthomode transducer, composed of two waveguide probe pairs, separates the incoming light into two linear po- larizations. Diplexers composed of resonant-stub band-pass filters separate the radiation into 125 to 170 GHz and 190 to 280 GHz pass bands. The millimeter-wave power is ultimately coupled to a hybrid co-planar waveguide microwave kinetic inductance detector using a novel, broadband circuit developed by our collaboration. Elec- tromagnetic simulations show the expected absorption efficiency of the detector is approximately 90%. Array fabrication will begin in the summer of 2016.
We discuss the design considerations and initial measurements from arrays of dual-polarization, lumped-element
kinetic inductance detectors (LEKIDs) nominally designed for cosmic microwave background (CMB) studies. The
detectors are horn-coupled, and each array element contains two single-polarization LEKIDs, which are made
from thin-film aluminum and optimized for a single spectral band centered on 150 GHz. We are developing two
array architectures, one based on 160 micron thick silicon wafers and the other based on silicon-on-insulator (SOI)
wafers with a 30 micron thick device layer. The 20-element test arrays (40 LEKIDs) are characterized with both
a linearly-polarized electronic millimeter wave source and a thermal source. We present initial measurements
including the noise spectra, noise-equivalent temperature, and responsivity. We discuss future testing and further
design optimizations to be implemented.
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.
Keywords: cryogenics detectors, millimeter-wave, superconducting resonators.
We present the results of a feasibility study, which examined deployment of a ground-based millimeter-wave polarimeter, tailored for observing the cosmic microwave background (CMB), to Isi Station in Greenland. The instrument for this study is based on lumped-element kinetic inductance detectors (LEKIDs) and an F/2.4 catoptric, crossed-Dragone telescope with a 500 mm aperture. The telescope is mounted inside the receiver and cooled to < 4 K by a closed-cycle 4He refrigerator to reduce background loading on the detectors. Linearly polarized signals from the sky are modulated with a metal-mesh half-wave plate that is rotated at the aperture stop of the telescope with a hollow-shaft motor based on a superconducting magnetic bearing. The modular detector array design includes at least 2300 LEKIDs, and it can be configured for spectral bands centered on 150 GHz or greater. Our study considered configurations for observing in spectral bands centered on 150, 210 and 267 GHz. The entire polarimeter is mounted on a commercial precision rotary air bearing, which allows fast azimuth scan speeds with negligible vibration and mechanical wear over time. A slip ring provides power to the instrument, enabling circular scans (360 degrees of continuous rotation). This mount, when combined with sky rotation and the latitude of the observation site, produces a hypotrochoid scan pattern, which yields excellent cross-linking and enables 34% of the sky to be observed using a range of constant elevation scans. This scan pattern and sky coverage combined with the beam size (15 arcmin at 150 GHz) makes the instrument sensitive to 5 < ` < 1000 in the angular power spectra.
SuperSpec is a novel on-chip spectrometer we are developing for multi-object, moderate resolution (R = 100 − 500), large bandwidth (~1.65:1) submillimeter and millimeter survey spectroscopy of high-redshift galaxies. The spectrometer employs a filter bank architecture, and consists of a series of half-wave resonators formed by lithographically-patterned superconducting transmission lines. The signal power admitted by each resonator is detected by a lumped element titanium nitride (TiN) kinetic inductance detector (KID) operating at 100 – 200 MHz. We have tested a new prototype device that is more sensitive than previous devices, and easier to fabricate. We present a characterization of a representative R = 282 channel at f = 236 GHz, including measurements of the spectrometer detection efficiency, the detector responsivity over a large range of optical loading, and the full system optical efficiency. We outline future improvements to the current system that we expect will enable construction of a photon-noise-limited R = 100 filter bank, appropriate for a line intensity mapping experiment targeting the [CII] 158 μm transition during the Epoch of Reionization.
The New IRAM KID Array (NIKA) is a dual-band camera operating with frequency multiplexed arrays of Lumped Element Kinetic Inductance Detectors (LEKIDs) cooled to 100 mK. NIKA is designed to observe the intensity and polarisation of the sky at 1.25 and 2.14 mm from the IRAM 30 m telescope. We present the improvements on the control of systematic effects and astrophysical results made during the last observation campaigns between 2012 and 2014.
The Neel Iram Kids Array (NIKA) is a prototype instrument devoted to millimetric astronomy that has been
designed to be mounted at the focal plane of the IRAM 30m telescope at Pico Veleta (Spain). After the runs
of 2009 and 2010, we carried a third technical run in October 2011. In its latest configuration, the instrument
consists of a dual-band camera, with bands centered at 150 GHz and 220 GHz, each of them equipped with
116 pixels based on Lumped Element Kinetic Inductance Detectors. During the third run we tested many
improvements that will play a crucial role in the development of the final, kilopixel sized camera. In particular,
a new geometry based on a Hilbert curve has been adopted for the absorbing area of the LEKIDs, that makes
the detectors dual-polarization sensitive. Furthermore, a different acquisition strategy has been adopted, which
has allowed us to increase the photometric accuracy of the measurements, a fundamental step in order to get
scientifically significant data. In this paper we describe the main characteristics of the 2011 NIKA instrument
and outline some of its key features, discusse the results we obtained and give a brief outlook on the future NIKA
camera which will be installed permanently on site.
SuperSpec is an ultra-compact spectrometer-on-a-chip for millimeter and submillimeter wavelength astronomy. Its very small size, wide spectral bandwidth, and highly multiplexed readout will enable construction of powerful multibeam spectrometers for high-redshift observations. The spectrometer consists of a horn-coupled microstrip feedline, a bank of narrow-band superconducting resonator filters that provide spectral selectivity, and kinetic inductance detectors (KIDs) that detect the power admitted by each filter resonator. The design is realized using thin-film lithographic structures on a silicon wafer. The mm-wave microstrip feedline and spectral filters of the first prototype are designed to operate in the band from 195-310 GHz and are fabricated from niobium with at T<sub><i>c </i></sub> of 9.2<i>K</i>. The KIDs are designed to operate at hundreds of MHz and are fabricated from titanium nitride with a T<sub><i>c </i></sub> of ~ 2 K. Radiation incident on the horn travels along the mm-wave microstrip, passes through the frequency-selective filter, and is finally absorbed by the corresponding KID where it causes a measurable shift in the resonant frequency. In this proceedings, we present the design of the KIDs employed in SuperSpec and the results of initial laboratory testing of a prototype device. We will also brie describe the ongoing development of a demonstration instrument that will consist of two 500-channel, R=700 spectrometers, one operating in the 1-mm atmospheric window and the other covering the 650 and 850 micron bands.
SuperSpec is an innovative, fully planar, compact spectrograph for mm/sub-mm astronomy. SuperSpec is based on a superconducting filter-bank consisting of a series of planar half-wavelength filters to divide up the incoming, broadband radiation. The power in each filter is then coupled into titanium nitride lumped element kinetic inductance detectors, facilitating the read out of a large number of filter elements. We will present electromagnetic simulations of the different components that will make up an <i><strong>R</strong></i> = 700 prototype instrument. Based on these simulations, we discuss optimisation of the coupling between the antenna, transmission line, filters and detectors.
SuperSpec is a pathfinder for future lithographic spectrometer cameras, which promise to energize extra-galactic astrophysics at (sub)millimeter wavelengths: delivering 200–500 kms<sup>-1</sup> spectral velocity resolution over an octave bandwidth for every pixel in a telescope’s field of view. We present circuit simulations that prove the concept, which enables complete millimeter-band spectrometer devices in just a few square-millimeter footprint. We evaluate both single-stage and two-stage channelizing filter designs, which separate channels into an array of broad-band detectors, such as bolometers or kinetic inductance detector (KID) devices. We discuss to what degree losses (by radiation or by absorption in the dielectric) and fabrication tolerances affect the resolution or performance of such devices, and what steps we can take to mitigate the degradation. Such design studies help us formulate critical requirements on the materials and fabrication process, and help understand what practical limits currently exist to the capabilities these devices can deliver today or over the next few years.
The Lumped Element Kinetic Inductance Detector (LEKID) was first proposed in 2007 as a solution for using
kinetic inductance type detectors for sub-mm astronomy (450 - 200μm). Since then the LEKID has been
demonstrated to have applications over a much wider range of wavelength. Examples of this have been 200μm
detection of a cold blackbody and successful testing of a demonstration array operating at 2mm on the IRAM
telescope in October 2009. Due to the combination of absorber and detector in a single element, the LEKID is
an extremely simple detector to fabricate requiring only one deposition and etch step to produce an array of up
to 1000 pixels multiplexed onto a single feedline. The LEKID is also a very compact detector making it ideal
for producing arrays with high filling factors. The suitability of the LEKID for use in large arrays has prompted
a return visit to the IRAM telescope with a dual band instrument in 2010. This presentation will review the
progress to date of the LEKIDs development and outline design considerations for producing LEKIDs for future
FIR astronomical instruments such as SPICA. Also reviewed will be possible applications for the LEKID outside
sub-mm and mm astronomy.
Lumped-element kinetic inductance detectors (LEKIDs) have recently shown considerable promise as direct-absorption
mm-wavelength detectors for astronomical applications. One major research thrust within the Néel Iram Kids Array (NIKA)
collaboration has been to investigate the suitability of these detectors for deployment at the 30-meter IRAM telescope located
on Pico Veleta in Spain.
Compared to microwave kinetic inductance detectors (MKID), using quarter wavelength resonators, the resonant circuit of
a LEKID consists of a discrete inductance and capacitance coupled to a feedline. A high and constant current density
distribution in the inductive part of these resonators makes them very sensitive. Due to only one metal layer on a silicon
substrate, the fabrication is relatively easy.
In order to optimize the LEKIDs for this application, we have recently probed a wide variety of individual resonator and
array parameters through simulation and physical testing. This included determining the optimal feed-line coupling, pixel
geometry, resonator distribution within an array (in order to minimize pixel cross-talk), and resonator frequency spacing.
Based on these results, a 32-pixel Aluminum array was fabricated and tested in a dilution fridge with optical access, yielding
an average optical NEP of ~7.2 x 10-16 W/Hz^1/2. In October 2009 a first prototype of LEKIDs has been tested at the IRAM
30 m telescope and first astronomical results have been achieved.
We describe a new type of FIR detector based on lumped element superconducting resonators (LEKIDs). These
devices can act as distributed FIR radiation absorbers without the need for an additional coupling structure.
In addition, these devices can be integrated into a compact filled array geometry with high filling factor. We
describe the optimization of lumped element resonators for high coupling efficiency to incoming radiation in the
wavelength region from 200μm - 450μm, measurements of electrical and optical properties of these devices and
the design of a prototype array using these detectors.
Kinetic inductance detectors (KIDs) provide an attractive solution to the production of large detector arrays for use in ground and space based 200μm astronomy. KIDs work by measuring the change in quasi-particle density upon photon absorption in a high Q superconducting resonator. A change in quasi-particle density is measured by a shift in phase of a microwave probe signal of frequency equal to that of the resonant frequency of the KID. Such detectors have a fundamental noise limit owing to the quasi-particle recombination rate, which, in a KID fabricated from a high quality Niobium film can give sensitivities of 10<sup>-18</sup>W√Hz at 1K. Constructing KIDs of varying resonant frequencies coupled to a single transmission line provides a multiplexed detector array with simple low temperature electronics. Here we discuss the theoretical requirements for both ground and space based 200μm cameras with various radiation coupling schemes for this wavelength range using distributed and lumped element high Q resonators.