This PDF file contains the front matter associated with SPIE Proceedings Volume 9914, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

The POL-2 polarimeter for the SCUBA-2 10 000 pixel Terahertz camera on the James Clerk Maxwell Telescope (JCMT) in it's late state of commissioning. Proposals have been accepted for POL-2 and general observing will start in August 2016. SCUBA-2 has a field of view of 43 arcmin at both of the 850 and 450 μm focal planes. POL-2 will map the sky in the the 850 μm band. The POL-2 polarimeter utilizes three optical components: a half wave plate and two wire-grid polarizers used as calibrator and analyzer covering the full field of SCUBA-2. We describe the instrument, data acquisition and features/artifacts that have been encountered during the commissioning.

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.

The SAFARI Detector Test Facility is an ultra-low background optical testbed for characterizing ultra-sensitive prototype horn-coupled TES bolmeters for SAFARI, the grating spectrometer on board the proposed SPICA satellite. The testbed contains internal cold and hot black-body illuminators and a light-pipe for illumination with an external source. We have added reimaging optics to facilitate array optical measurements. The system is now being used for optical testing of prototype detector arrays read out with frequency-domain multiplexing. We present our latest optical measurements of prototype arrays and discuss these in terms of the instrument performance.

Here we report on the optical design and on the spectral-spatial characterisation of a small 16 pixel camera. The prototype uses TES detectors with NEPs ~10^-16 W/Hz^0.5 which have been fabricated with near identical optical coupling structures to mimic their much lower NEP counterparts (~10^-19 W/Hz^0.5). This modification, which is achieved through changing only the pixel thermal conductance, G, has allowed us to perform spectral/spatial cryogenic testing using a 100mK ADR to view room temperature thermal sources. The measurements show a flat spectral response across the waveband and minimal side lobe structure in the antenna patterns down to 30dB.

We describe the geometry, architecture, dark- and optical performance of ultra-low-noise transition edge sensors as THz detectors for the SAFARI instrument. The TESs are fabricated from superconducting Mo/Au bilayers coupled to impedance-matched superconducting β-phase Ta thin-film absorbers. The detectors have phonon-limited dark noise equivalent powers of order 0.5 - 1.0 aW/ √ Hz and saturation powers of order 20 - 40 fW. The low temperature test configuration incorporating micro-machined backshorts is also described, and construction and typical performance characteristics for the optical load are shown. We report preliminary measurements of the optical performance of these TESs for two SAFARI bands; L-band at 110 − 210 μm and S-band 34 − 60 μm .

SRON is developing ultra-low noise Transition Edge Sensors (TESs) based on a superconducting Ti/Au bilayer on a suspended SiN island with SiN legs for the SAFARI instrument aboard the SPICA mission. We successfully fabricated TESs with very narrow (0.5-0.7 μm) and thin (0.25 μm) SiN legs on different sizes of SiN islands using deep reactiveion etching process. The pixel size is 840x840 μm² and there are variety of designs with and without optical absorbers. For TESs without absorbers, we measured electrical NEPs as low as <1x10^-19 W/√Hz with response time of 0.3 ms and reached the phonon noise limit. Using TESs with absorbers, we quantified the darkness of our setup and confirmed a photon noise level of 2x10^-19 W/√Hz.

We describe feedhorn-coupled polarization-sensitive detector arrays that utilize monocrystalline silicon as the dielectric substrate material. Monocrystalline silicon has a low-loss tangent and repeatable dielectric constant, characteristics that are critical for realizing efficient and uniform superconducting microwave circuits. An additional advantage of this material is its low specific heat. In a detector pixel, two Transition-Edge Sensor (TES) bolometers are antenna-coupled to in-band radiation via a symmetric planar orthomode transducer (OMT). Each orthogonal linear polarization is coupled to a separate superconducting microstrip transmission line circuit. On-chip filtering is employed to both reject out-of-band radiation from the upper band edge to the gap frequency of the niobium superconductor, and to flexibly define the bandwidth for each TES to meet the requirements of the application. The microwave circuit is compatible with multi-chroic operation. Metalized silicon platelets are used to define the backshort for the waveguide probes. This micro-machined structure is also used to mitigate the coupling of out-of-band radiation to the microwave circuit. At 40 GHz, the detectors have a measured efficiency of ∼90%. In this paper, we describe the development of the 90 GHz detector arrays that will be demonstrated using the Cosmology Large Angular Scale Surveyor (CLASS) ground-based telescope.

This report presents a down-conversion method involving digital sideband separation for the Yuan-Tseh Lee Array (YTLA) to double the processing bandwidth. The receiver consists of a MMIC HEMT LNA front end operating at a wavelength of 3 mm, and sub-harmonic mixers that output signals at intermediate frequencies (IFs) of 2–18 GHz. The sideband separation scheme involves an analog 90° hybrid followed by two mixers that provide down-conversion of the IF signal to a pair of in-phase (I) and quadrature (Q) signals in baseband. The I and Q baseband signals are digitized using 5 Giga sample per second (Gsps) analog-to-digital converters (ADCs). A second hybrid is digitally implemented using field-programmable gate arrays (FPGAs) to produce two sidebands, each with a bandwidth of 1.6 GHz. The 2 x 1.6 GHz band can be tuned to cover any 3.6 GHz window within the aforementioned IF range of the array. Sideband rejection ratios (SRRs) above 20 dB can be obtained across the 3.6 GHz bandwidth by equalizing the power and delay between the I and Q baseband signals. Furthermore, SRRs above 30 dB can be achieved when calibration is applied.

We report on the design of a 240 GHz double-side-band receiver for the Submillimeter Array (SMA). The heart of this receiver is a 3-junction series connected SIS mixer, which allows it to provide intermediate frequency (IF) output up to more than 12 GHz. We have custom built a low noise Amplifier-Multiplier Chain for use as the receiver’s Local Oscillator module, which is tunable from 210 to 270 GHz. The receiver has demonstrated low noise performance in laboratory. 7 out of the 8 SMA antennas are now equipped with this receiver. The receiver has already participated in Event Horizon Telescope observations in April 2016, working with the SMA-200 receiver to provide dual polarization coverage for the EHT Hawaii Station. This receiver has enabled the SMA to provide 32 Gbit per second data stream to the EHT observations. We are currently trying to improve the on-sky beam co-alignment of this receiver with respect to other SMA receivers.

In the modular sideband-separating mixers that we built over the last years, we observe a clear anti-correlation between the image rejection ratio obtained with a certain block and its noise performance, as well as strong correlations between the image rejection and imbalances in the pumping of the mixer devices. We report on the mechanisms responsible for these effects, and conclude that the reduction of the image rejection is largely explained by the presence of standing waves. We demonstrate the rejection ratio to be very sensitive to those. In principle, all potential round-trip paths should be terminated in matched loads, so no standing waves can develop. In practice, the typical high reflections from the SIS mixers combined with imperfect loads and non-negligible input/output reflections of the other components give many opportunities for standing waves. Since most of the loss of image rejection can be attributed to standing waves, the anti-correlation with the noise temperature can be understood by considering any excess loss in the structure, as the waveguides start acting as distribured loads. This reduces the standing waves, and thereby improves the rejection ratio, at the expense of noise temperature. Based on these experiences, we designed a new waveguide structure, with a basic waveguide size of 400×200 μm and improved loads. Strong emphasis was placed on low input and output reflections of the waveguide components, in some places at the cost of phase or amplitude imbalance. For the latter there is ample margin not to impair the performance, however. Apart from further details of the design, we present the first results of the new mixers, tested in a modified production-level ALMA Band 9 receiver, and show that even in an unfinished state, it simultaneously meets requirements for image rejection and noise temperature.

Wideband receivers for the 3-mm band were developed for CARMA, the Combined Array for Research in Millimeterwave Astronomy. Three cryogenic MMIC (monolithic microwave integrated circuit) amplifiers manufactured in InP 35- nm technology are combined in a block with waveguide probes and gain equalizers to cover the 80–116 GHz band. These are followed by a sideband-separating mixer that has two 17 GHZ wide outputs, for upper and lower sidebands. Each receiver has a feed horn followed by a circular-to-linear polarizer and orthomode transducer. The two polarizations are amplified by the cryogenic MMICs, and the outputs downconverted in sideband separating mixers, resulting in four 1–18 GHz channels that can be simultaneously correlated. The first receiver was tested in the lab, and on-sky tests conducted at CARMA. Measured noise temperatures were in the range 40–70 K, with a sideband rejection of about 15 dB.

Polarized thermal emission from interstellar dust grains can be used to map magnetic fields in star forming molecular clouds and the diffuse interstellar medium (ISM). The Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry (BLASTPol) flew from Antarctica in 2010 and 2012 and produced degree-scale polarization maps of several nearby molecular clouds with arcminute resolution. The success of BLASTPol has motivated a next-generation instrument, BLAST-TNG, which will use more than 3000 linear polarization- sensitive microwave kinetic inductance detectors (MKIDs) combined with a 2.5 m diameter carbon fiber primary mirror to make diffraction-limited observations at 250, 350, and 500 µm. With 16 times the mapping speed of BLASTPol, sub-arcminute resolution, and a longer flight time, BLAST-TNG will be able to examine nearby molecular clouds and the diffuse galactic dust polarization spectrum in unprecedented detail. The 250 μm detec- tor array has been integrated into the new cryogenic receiver, and is undergoing testing to establish the optical and polarization characteristics of the instrument. BLAST-TNG will demonstrate the effectiveness of kilo-pixel MKID arrays for applications in submillimeter astronomy. BLAST-TNG is scheduled to fly from Antarctica in December 2017 for 28 days and will be the first balloon-borne telescope to offer a quarter of the flight for “shared risk” observing by the community.

SCUBA-2 is a state of the art wide field camera on the JCMT. SCUBA-2 has been fully operational since November 2011, producing a wide range of science results, including a unique series of survey programs. A new large survey programme commenced in 2015, which included for the first time, polarisation sensitive measurements using POL-2, the polarimeter ancillary instrument. We discuss proposals and the science case for upgrading SCUBA-2 with new detector arrays that will keep SCUBA-2 and the JCMT at the forefront of continuum submillimetre science.

This proceeding presents the current TIME-Pilot instrument design and status with a focus on the close-packed modular detector arrays and spectrometers. Results of laboratory tests with prototype detectors and spectrometers are discussed. TIME-Pilot is a new mm-wavelength grating spectrometer array under development that will study the Epoch of Reionization (the period of time when the first stars and galaxies ionized the intergalactic medium) by mapping the fluctuations of the redshifted 157:7 μm emission line of singly ionized carbon ([CII]) from redshift z ~ 5:2 to 8:5. As a tracer of star formation, the [CII] power spectrum can provide information on the sources driving reionization and complements 21 cm data (which traces neutral hydrogen in the intergalactic medium). Intensity mapping provides a measure of the mean [CII] intensity without the need to resolve and detect faint sources individually. We plan to target a 1 degree by 0.35 arcminute field on the sky and a spectral range of 199-305 GHz, producing a spatial-spectral slab which is 140 Mpc by 0.9 Mpc on-end and 1230 Mpc in the redshift direction. With careful removal of intermediate-redshift CO sources, we anticipate a detection of the halo-halo clustering term in the [CII] power spectrum consistent with current models for star formation history in 240 hours on the JCMT. TIME-Pilot will use two stacks of 16 parallel-plate waveguide spectrometers (one stack per polarization) with a resolving power R ~ 100 and a spectral range of 183 to 326 GHz. The range is divided into 60 spectral channels, of which 16 at the band edges on each spectrometer serve as atmospheric monitors. The diffraction gratings are curved to produce a compact instrument, each focusing the diffracted light onto an output arc sampled by the 60 bolometers. The bolometers are built in buttable dies of 8 (low freqeuency) or 12 (high frequency) spectral channels by 8 spatial channels and are mated to the spectrometer stacks. Each detector consists of a gold micro-mesh absorber and a titanium transition edge sensor (TES). The detectors (1920 total) are designed to operate from a 250 mK base temperature in an existing cryostat with a photon-noise-dominated NEP of ~2 * 10^-17 WHz^-1-2. A set of flexible superconducting cables connect the detectors to a time-domain multiplexing SQUID readout system.

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 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.

Bicep3 is a 520mm aperture, compact two-lens refractor designed to observe the polarization of the cosmic microwave background (CMB) at 95 GHz. Its focal plane consists of modularized tiles of antenna-coupled transition edge sensors (TESs), similar to those used in Bicep2 and the Keck Array. The increased per-receiver optical throughput compared to Bicep2/Keck Array, due to both its faster f=1:7 optics and the larger aperture, more than doubles the combined mapping speed of the Bicep/Keck program. The Bicep3 receiver was recently upgraded to a full complement of 20 tiles of detectors (2560 TESs) and is now beginning its second year of observation (and first science season) at the South Pole. We report on its current performance and observing plans. Given its high per-receiver throughput while maintaining the advantages of a compact design, Bicep3- class receivers are ideally suited as building blocks for a 3rd-generation CMB experiment, consisting of multiple receivers spanning 35 GHz to 270 GHz with total detector count in the tens of thousands. We present plans for such an array, the new "BICEP Array" that will replace the Keck Array at the South Pole, including design optimization, frequency coverage, and deployment/observing strategies.

BICEP3, the latest telescope in the BICEP/Keck program, started science observations in March 2016. It is a 550mm aperture refractive telescope observing the polarization of the cosmic microwave background at 95 GHz. We show the focal plane design and detector performance, including spectral response, optical efficiency and preliminary sensitivity of the upgraded BICEP3. We demonstrate 9.72 μKCMB√s noise performance of the BICEP3 receiver.

We describe 280 GHz bolometric detector arrays that instrument the balloon-borne polarimeter spider. A primary science goal of spider is to measure the large-scale B-mode polarization of the cosmic microwave background (cmb) in search of the cosmic-inflation, gravitational-wave signature. 280 GHz channels aid this science goal by constraining the level of B-mode contamination from galactic dust emission. We present the focal plane unit design, which consists of a 16x16 array of conical, corrugated feedhorns coupled to a monolithic detector array fabricated on a 150 mm diameter silicon wafer. Detector arrays are capable of polarimetric sensing via waveguide probe-coupling to a multiplexed array of transition-edge-sensor (TES) bolometers. The spider receiver has three focal plane units at 280 GHz, which in total contains 765 spatial pixels and 1,530 polarization sensitive bolometers. By fabrication and measurement of single feedhorns, we demonstrate 14.7° FHWM Gaussian-shaped beams with <1% ellipticity in a 30% fractional bandwidth centered at 280 GHz. We present electromagnetic simulations of the detection circuit, which show 94% band-averaged, single-polarization coupling efficiency, 3% reflection and 3% radiative loss. Lastly, we demonstrate a low thermal conductance bolometer, which is well-described by a simple TES model and exhibits an electrical noise equivalent power (NEP) = 2.6 x 10^-17 W/√Hz, consistent with the phonon noise prediction.

PILOT is a stratospheric experiment designed to measure the polarization of dust FIR emission, towards the diffuse interstellar medium. The first PILOT flight was carried out from Timmins in Ontario-Canada on September 20th 2015. The flight has been part of a launch campaign operated by the CNES, which has allowed to launch 4 experiments, including PILOT. The purpose of this paper is to describe the performance of the instrument in flight and to perform a first comparison with those achieved during ground tests. The analysis of the flight data is on-going, in particular the identification of instrumental systematic effects, the minimization of their impact and the quantification of their remaining effect on the polarization data. At the end of this paper, we shortly illustrate the quality of the scientific observations obtained during this first flight, at the current stage of systematic effect removal.

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 present the design and characterization of low-volume, lumped-element aluminum kinetic inductance de- tectors for sensitive far-infrared astronomy observations. The lumped-element kinetic inductance detectors are comprised of meandered inductors that serve as radiation absorbers in parallel with interdigitated capacitors, forming high quality factor resonators. Low inductor volumes lead to low noise equivalent powers by raising quasiparticles densities, and hence responsivities, with respect to larger volumes. Low volumes are achieved with thin (20 nm), narrow (150 nm) inductors. The interdigitated capacitor architecture is designed to mitigate two-level system noise by lowering electric fields in the silicon substrate. Resonance frequencies are in the range of 190 to 500 MHz, with measured internal quality factors in excess of 1 x 10⁵. In a prior incarnation, a titanium nitride layer on top of the aluminum served as a protective layer, but complicated the superconducting proper- ties. These results were reported previously. In the current incarnation, the aluminum layer is left bare with no titanium nitride over-layer. The results for these bare aluminum devices include a yield of 88%, frequency responsivity of 10⁹ W^-1, and noise equivalent power of 1 x 10^-17 W Hz^-1/2 for a 350μm array. There is no evidence for 1=f noise down to at least 200 mHz. The sensitivity is currently limited by white noise, very likely from stray light in the testbed; for this detector design, sensitivities limited by generation-recombination noise in a lower-background environment should be several orders of magnitude lower.

The main objective of this activity is to develop new focal plane coupling array concepts and technologies that optimise the coupling from reflector optics to the large number of detectors for next generation sub millimetre wave telescopes particularly targeting measurement of the polarization of the cosmic microwave background (CMB). In this 18 month TRP programme the consortium are tasked with developing, manufacturing and experimentally verifying a prototype multichroic pixel which would be suitable for the large focal plane arrays which will be demanded to reach the required sensitivity of future CMB polarization missions. One major development was to have multichroic operation to potentially reduce the required focal plane size of a CMB mission. After research in the optimum telescope design and definition of requirements based on a stringent science case review, a number of compact focal plane architecture concepts were investigated before a pixel demonstrator consisting of a planar mesh lens feeding a backend Resonant Cold Electron Bolometer RCEB for filtering and detection of the dual frequency signal was planned for manufacture and test. In this demonstrator the frequencies of the channels was chosen to be 75 and 105 GHz in the w band close to the peak CMB signal. In the next year the prototype breadboards will be developed to test the beams produced by the manufactured flat lenses fed by a variety of antenna configurations and the spectral response of the RCEBs will also be verified.

In this paper we present the development and verification of feed horn simulation code based on the mode- matching technique to simulate the electromagnetic performance of waveguide based structures of rectangular cross-section. This code is required to model multi-mode pyramidal horns which may be required for future far infrared (far IR) space missions where wavelengths in the range of 30 to 200 µm will be analysed. Multi-mode pyramidal horns can be used effectively to couple radiation to sensitive superconducting devices like Kinetic Inductance Detectors (KIDs) or Transition Edge Sensor (TES) detectors. These detectors could be placed in integrating cavities (to further increase the efficiency) with an absorbing layer used to couple to the radiation. The developed code is capable of modelling each of these elements, and so will allow full optical characterisation of such pixels and allow an optical efficiency to be calculated effectively. As the signals being measured at these short wavelengths are at an extremely low level, the throughput of the system must be maximised and so multi-mode systems are proposed. To this end, the focal planes of future far IR missions may consist of an array of multi-mode rectangular feed horns feeding an array of, for example, TES devices contained in individual integrating cavities. Such TES arrays have been fabricated by SRON Groningen and are currently undergoing comprehensive optical, electrical and thermal verification. In order to fully understand and validate the optical performance of the receiver system, it is necessary to develop comprehensive and robust optical models in parallel. We outline the development and verification of this optical modelling software by means of applying it to a representative multi-mode system operating at 150 GHz in order to obtain sufficiently short execution times so as to comprehensively test the code. SAFARI (SPICA FAR infrared Instrument) is a far infrared imaging grating spectrometer, to be proposed as an ESA M5 mission. It is planned for this mission to be launched on board the proposed SPICA (SPace Infrared telescope for Cosmology and Astrophysics) mission, in collaboration with JAXA. SAFARI is planned to operate in the 1.5-10 THz band, focussing on the formation and evolution of galaxies, stars and planetary systems. The pixel that drove the development of the techniques presented in this paper is typical of one option that could be implemented in the SAFARI focal plane, and so the ability to accurately understand and characterise such pixels is critical in the design phase of the next generation of far IR telescopes.

The Large Scale Polarisation Explorer (LSPE) is a balloon-borne experiment aiming to measure the B-mode component of the CMB polarisation at large angular scales. Onboard LSPE, the Short Wavelength Instrument for the Polarisation Explorer (SWIPE) is a bolometric polarimeter observing in three bands centred at 140, 220 and 240 GHz. The telescope is a single large-diameter plano-convex lens with a cold aperture stop. A small number of multi-mode feed horns feeding bolometric detectors are used within the focal plane, achieving a sensitivity equivalent to that of 100’s of single-mode horns. Simulations have been performed to predict the multi-mode optical response of the horn-lens configuration for centre and off-axis pixels pertaining to each frequency band. The horn has been simulated to a high accuracy using the Method of Moments. Using the horn simulation result as a source, the optical response of the lens has been examined using the more approximate simulation technique; Ray-Launching Geometrical Optics (RL-GO). Solution accuracy and simulation time depend heavily on the choice of RL-GO simulation parameters including: mesh size; the number of launched rays; and how densely the horn source beam is sampled. Individual convergence studies have been performed for each of these parameters and a final model has been obtained as a compromise between simulation time and accuracy. The instrumental polarisation of the lens is predicted to be at the -50 dB level. Finally, the optimal location of where to place the telescope focus in relation to the horn to maximise on-axis gain has been investigated. Several techniques agreed that the ‘phase centre’ is around 20 mm behind the horn aperture at 140 GHz, increasing to 30 mm at 220 and 240 GHz. Taking into account beam truncation effects caused by the finite size of the telescope was found to reduce the overall variation in on-axis gain.

In these proceedings, we summarize our in-field evaluation of temperature-to-polarization leakage associated with the use of a continuously-rotating, ambient-temperature half-wave plate (HWP) on the Atacama B-Mode Search (ABS) experiment. Using two seasons of data, we demonstrate scalar leakage of ∼ 0.01%. This is consistent with model expectations and an order of magnitude better than any previously-reported leakage. We constrain higher-order dipole and quadrupole leakage terms to be < 0.06% (95% confidence). Without any mitigation from scan cross-linking or boresight rotation, this corresponds to an upper limit on systematic errors in the tensor-to-scalar ratio r ;S 0.01. The HWP significantly reduces temperature-to-polarization leakage systematic errors for ABS and shows the promise of fast polarization modulation with HWPs for future experiments. Full details can be found in Ref. 1.

Advanced ACTPol (AdvACT) is an upgraded camera for the Atacama Cosmology Telescope (ACT) that will measure the cosmic microwave background in temperature and polarization over a wide range of angular scales and five frequency bands from 28-230 GHz. AdvACT will employ four arrays of feedhorn-coupled, polarization- sensitive multichroic detectors. To accommodate the higher pixel packing densities necessary to achieve Ad- vACT’s sensitivity goals, we have developed and optimized wideband spline-profiled feedhorns for the AdvACT multichroic arrays that maximize coupling efficiency while carefully controlling polarization systematics. We present the design, fabrication, and testing of wideband spline-profiled feedhorns for the multichroic arrays of AdvACT.

Detectors for cosmic microwave background (CMB) experiments are now essentially background limited, so a straightforward alternative to improve sensitivity is to increase the number of detectors. Large arrays of multichroic pixels constitute an economical approach to increasing the number of detectors within a given focal plane area. Here, we present the fabrication of large arrays of dual-polarized multichroic transition-edge-sensor (TES) bolometers for the South Pole Telescope third-generation CMB receiver (SPT-3G). The complete SPT-3G receiver will have 2690 pixels, each with six detectors, allowing for individual measurement of three spectral bands (centered at 95 GHz, 150 GHz and 220 GHz) in two orthogonal polarizations. In total, the SPT-3G focal plane will have 16140 detectors. Each pixel is comprised of a broad-band sinuous antenna coupled to a niobium microstrip transmission line. In-line filters are used to define the different band-passes before the millimeter-wavelength signal is fed to the respective Ti/Au TES sensors. Detectors are read out using a 64x frequency domain multiplexing (fMux) scheme. The microfabrication of the SPT-3G detector arrays involves a total of 18 processes, including 13 lithography steps. Together with the fabrication process, the effect of processing on the Ti/Au TES’s Tc is discussed. In addition, detectors fabricated with Ti/Au TES films with Tc between 400 mK 560 mK are presented and their thermal characteristics are evaluated. Optical characterization of the arrays is presented as well, indicating that the response of the detectors is in good agreement with the design values for all three spectral bands (95 GHz, 150 GHz, and 220 GHz). The measured optical efficiency of the detectors is between 0.3 and 0.8. Results discussed here are extracted from a batch of research of development wafers used to develop the baseline process for the fabrication of the arrays of detectors to be deployed with the SPT-3G receiver. Results from these research and development wafers have been incorporated into the fabrication process to get the baseline fabrication process presented here. SPT-3G is scheduled to deploy to the South Pole Telescope in late 2016.

The Advanced Atacama Cosmology Telescope Polarimeter is an upgraded receiver for the Atacama Cosmology Telescope, which has begun making measurements of the small angular scale polarization anisotropies in the Cosmic Microwave Background using the first of four new multichroic superconducting detector arrays. Here, we review all details of the optimization and characterization of this first array, which features 2012 AlMn transition- edge sensor bolometers operating at 150 and 230 GHz. We present critical temperatures, thermal conductivities, saturation powers, time constants, and sensitivities for the array. The results show high uniformity across the 150 mm wafer and good performance in the field.

The Primordial Inflation Explorer (PIXIE) is an Explorer-class mission concept designed to measure the polar- ization and absolute intensity of the cosmic microwave background. In the following, we report on the design, fabrication, and performance of the multimode polarization-sensitive bolometers for PIXIE, which are based on silicon thermistors. In particular we focus on several recent advances in the detector design, including the implementation of a scheme to greatly raise the frequencies of the internal vibrational modes of the large-area, low-mass optical absorber structure consisting of a grid of micromachined, ion-implanted silicon wires. With ∼ 30 times the absorbing area of the spider-web bolometers used by Planck, the tensioning scheme enables the PIXIE bolometers to be robust in the vibrational and acoustic environment at launch of the space mission. More generally, it could be used to reduce microphonic sensitivity in other types of low temperature detectors. We also report on the performance of the PIXIE bolometers in a dark cryogenic environment.

Measuring the B-mode polarization of the CMB radiation requires a detailed understanding of the projection of the detector onto the sky. We show how the combination of scan strategy and processing generates a cylindrical beam for the spectrum measurement. Both the instrumental design and the scan strategy reduce the cross coupling between the temperature variations and the B-modes. As with other polarization measurements some post processing may be required to eliminate residual errors.

In this paper we present the results of our 176-pixel prototype of the FDM readout system for SAFARI, a TES-based focal-plane instrument for the far-IR SPICA mission. We have implemented the knowledge obtained from the detailed study on electrical crosstalk reported previously. The effect of carrier leakage is reduced by a factor two, mutual impedance is reduced to below 1 nH and mutual inductance is removed. The pixels are connected in stages, one quarter of the array half of the array and the full array, to resolve intermediate technical issues. A semi-automated procedure was incorporated to find all optimal settings for all pixels. And as a final step the complete array has been connected and 132 pixels have been read out simultaneously within the frequency range of 1-3.8MHz with an average frequency separation of 16kHz. The noise was found to be detector limited and was not affected by reading out all pixels in a FDM mode. With this result the concept of using FDM for multiplexed bolometer read out for the SAFARI instrument has been demonstrated.

The third generation receiver for the South Pole Telescope, SPT-3G, will make extremely deep, arcminuteresolution maps of the temperature and polarization of the cosmic microwave background. The SPT-3G maps will enable studies of the B-mode polarization signature, constraining primordial gravitational waves as well as the effect of massive neutrinos on structure formation in the late universe. The SPT-3G receiver will achieve exceptional sensitivity through a focal plane of ~16,000 transition-edge sensor bolometers, an order of magnitude more than the current SPTpol receiver. SPT-3G uses a frequency domain multiplexing (fMux) scheme to read out the focal plane, combining the signals from 64 bolometers onto a single pair of wires. The fMux readout facilitates the large number of detectors in the SPT-3G focal plane by limiting the thermal load due to readout wiring on the 250 millikelvin cryogenic stage. A second advantage of the fMux system is that the operation of each bolometer can be optimized. In addition to these benefits, the fMux readout introduces new challenges into the design and operation of the receiver. The bolometers are operated at a range of frequencies up to 5 MHz, requiring control of stray reactances over a large bandwidth. Additionally, crosstalk between multiplexed detectors will inject large false signals into the data if not adequately mitigated. SPT-3G is scheduled to deploy to the South Pole Telescope in late 2016. Here, we present the pre-deployment performance of the fMux readout system with the SPT-3G focal plane.

Field Programmable Gate Arrays (FPGAs) capacity and Analog to Digital Converters (ADCs) speed have largely increased in the last decade. Nowadays we can find one million or more logic blocks (slices) as well as several thousand arithmetic units (ALUs/DSP) available on a single FPGA chip. We can also commercially procure ADC chips reaching 10 GSPS, with 8 bits resolution or more. This unprecedented power of computing hardware has allowed the digitalization of signal processes traditionally performed by analog components. In radio astronomy, the clearest example has been the development of digital sideband separating receivers which, by replacing the IF hybrid and calibrating the system imbalances, have exhibited a sideband rejection above 40dB; this is 20 to 30dB higher than traditional analog sideband separating (2SB) receivers. In Rodriguez et al.,1 and Finger et al.,2 we have demonstrated very high digital sideband separation at 3mm and 1mm wavelengths, using laboratory setups. We here show the first implementation of such technique with a 3mm receiver integrated into a telescope, where the calibration was performed by quasi-optical injection of the test tone in front of the Cassegrain antenna. We also reported progress in digital polarization synthesis, particularly in the implementation of a calibrated Digital Ortho-Mode Transducer (DOMT) based on the Morgan et al. proof of concept.3 They showed off- line synthesis of polarization with isolation higher than 40dB. We plan to implement a digital polarimeter in a real-time FPGA-based (ROACH-2) platform, to show ultra-pure polarization isolation in a non-stop integrating spectrometer.

Advanced ACTPol is an instrument upgrade for the six-meter Atacama Cosmology Telescope (ACT) designed to measure the cosmic microwave background (CMB) temperature and polarization with arcminute-scale angular resolution. To achieve its science goals, Advanced ACTPol utilizes a larger readout multiplexing factor than any previous CMB experiment to measure detector arrays with approximately two thousand transition-edge sensor (TES) bolometers in each 150 mm detector wafer. We present the implementation and testing of the Advanced ACTPol time-division multiplexing readout architecture with a 64-row multiplexing factor. This includes testing of individual multichroic detector pixels and superconducting quantum interference device (SQUID) multiplexing chips as well as testing and optimizing of the integrated readout electronics. In particular, we describe the new automated multiplexing SQUID tuning procedure developed to select and optimize the thousands of SQUID parameters required to readout each Advanced ACTPol array. The multichroic detector pixels in each array use separate channels for each polarization and each of the two frequencies, such that four TESes must be read out per pixel. Challenges addressed include doubling the number of detectors per multiplexed readout channel compared to ACTPol and optimizing the Nyquist inductance to minimize detector and SQUID noise aliasing.

The Simons Array is a next generation cosmic microwave background (CMB) polarization experiment whose science target is a precision measurement of the B-mode polarization pattern produced both by inflation and by gravitational lensing. As a continuation and extension of the successful POLARBEAR experimental program, the Simons Array will consist of three cryogenic receivers each featuring multichroic bolometer arrays mounted onto separate 3.5m telescopes. The first of these, also called POLARBEAR-2A, will be the first to deploy in late 2016 and has a large diameter focal plane consisting of dual-polarization dichroic pixels sensitive at 95 GHz and 150 GHz. The POLARBEAR-2A focal plane will utilize 7,588 antenna-coupled superconducting transition edge sensor (TES) bolometers read out with SQUID amplifiers using frequency domain multiplexing techniques. The next two receivers that will make up the Simons Array will be nearly identical in overall design but will feature extended frequency capability. The combination of high sensitivity, multichroic frequency coverage and large sky area available from our mid-latitude Chilean observatory will allow Simons Array to produce high quality polarization sky maps over a wide range of angular scales and to separate out the CMB B-modes from other astrophysical sources with high fidelity. After accounting for galactic foreground separation, the Simons Array will detect the primordial gravitational wave B-mode signal to r > 0.01 with a significance of > 5σ and will constrain the sum of neutrino masses to 40 meV (1σ) when cross-correlated with galaxy surveys. We present the current status of this funded experiment, its future, and discuss its projected science return.

POLARBEAR-2 (PB-2) is a cosmic microwave background (CMB) polarization experiment that will be located in the Atacama highland in Chile at an altitude of 5200 m. Its science goals are to measure the CMB polarization signals originating from both primordial gravitational waves and weak lensing. PB-2 is designed to measure the tensor to scalar ratio, r, with precision σ(r) > 0:01, and the sum of neutrino masses, Σm_z, with σ(Σm_v) < 90 meV. To achieve these goals, PB-2 will employ 7588 transition-edge sensor bolometers at 95 GHz and 150 GHz, which will be operated at the base temperature of 250 mK. Science observations will begin in 2017.

The Primordial Inflation Polarization ExploreR (PIPER) is a balloon-borne telescope designed to measure the polarization of the Cosmic Microwave Background on large angular scales. PIPER will map 85% of the sky at 200, 270, 350, and 600 GHz over a series of 8 conventional balloon flights from the northern and southern hemispheres. The first science flight will use two 32 × 40 arrays of backshort-under-grid transition edge sensors, multiplexed in the time domain, and maintained at 100 mK by a Continuous Adiabatic Demagnetization Refrigerator. Front- end cryogenic Variable-delay Polarization Modulators provide systematic control by rotating linear to circular polarization at 3 Hz. Twin telescopes allow PIPER to measure Stokes I, Q, U , and V simultaneously. The telescope is maintained at 1.5 K in an LHe bucket dewar. Cold optics and the lack of a warm window permit sensitivity at the sky-background limit. The ultimate science target is a limit on the tensor-to-scalar ratio of r ∼ 0.007, from the reionization bump to l ∼ 300. PIPER’s first flight will be from the Northern hemisphere, and overlap with the CLASS survey at lower frequencies. We describe the current status of the PIPER instrument.

The Cosmology Large Angular Scale Surveyor (CLASS) is a four telescope array designed to characterize relic primordial gravitational waves from in ation and the optical depth to reionization through a measurement of the polarized cosmic microwave background (CMB) on the largest angular scales. The frequencies of the four CLASS telescopes, one at 38 GHz, two at 93 GHz, and one dichroic system at 145/217 GHz, are chosen to avoid spectral regions of high atmospheric emission and span the minimum of the polarized Galactic foregrounds: synchrotron emission at lower frequencies and dust emission at higher frequencies. Low-noise transition edge sensor detectors and a rapid front-end polarization modulator provide a unique combination of high sensitivity, stability, and control of systematics. The CLASS site, at 5200 m in the Chilean Atacama desert, allows for daily mapping of up to 70% of the sky and enables the characterization of CMB polarization at the largest angular scales. Using this combination of a broad frequency range, large sky coverage, control over systematics, and high sensitivity, CLASS will observe the reionization and recombination peaks of the CMB E- and B-mode power spectra. CLASS will make a cosmic variance limited measurement of the optical depth to reionization and will measure or place upper limits on the tensor-to-scalar ratio, r, down to a level of 0.01 (95% C.L.).

In this work we present experimental investigation of the MgB₂ hot-electron bolometer (HEB) for low noise mixing at terahertz frequencies. A dedicated MgB₂ thin film deposition system was designed and constructed based on Hybrid Physical-Chemical Deposition. Films as thin as 15nm have a superconducting transition at 35K, with a critical current density <10⁷ A/cm² (at 4.2K) in bridges as narrow as 500nm, indicating on good connectivity in the film. The gain bandwidth (GBW) was measured by mixing of two THz sources. The GBW is proportional to the film thickness and it is at least 6GHz for 15nm thick devices. Performance of MgB₂ HEBs was compared to performance of one of the NbN HEB mixers made for the Herschel Space Observatory (one of the flight units), for which both the GBW and the Noise Bandwidth (NBW) was measured. MgB₂ HEB mixers show a GBW at least a factor of three broader compared to the NbN HEB measured in the same set-up.

Obtaining temperature, pressure, and composition profiles along with wind velocities in the Earth’s thermosphere/ionosphere system is a key NASA goal for understanding our planet. We report on the status of a technology development effort to build an all-solid-state heterodyne receiver at 2.06 THz that will allow the measurement of the 2.06 THz [OI] line for altitudes greater than 100 km. The receiver front end features low-parasitic Schottky diode mixer chips that are driven by a local oscillator (LO) source using Schottky diode based multipliers. The multiplier chain consists of a 38 GHz oscillator followed by a set of three cascaded triplers at 114 GHz, 343 GHz and 1.03 THz.

Phased array feed (PAF) receivers used on radio astronomy telescopes offer the promise of increased fields of view while maintaining the superlative performance attained with traditional single pixel feeds (SPFs). However, the much higher noise temperatures of room temperature PAFs compared to cryogenically-cooled SPFs have prevented their general adoption. Here we describe a conceptual design for a cryogenically cooled 2.8 – 5.18 GHz dual linear polarization PAF with estimated receiver temperature of 11 K. The cryogenic PAF receiver will comprise a 140 element Vivaldi antenna array and low-noise amplifiers housed in a 480 mm diameter cylindrical dewar covered with a RF transparent radome. A broadband two-section coaxial feed is integrated within each metal antenna element to withstand the cryogenic environment and to provide a 50 ohm impedance for connection to the rest of the receiver. The planned digital beamformer performs digitization, frequency band selection, beam forming and array covariance matrix calibration. Coupling to a 15 m offset Gregorian dual-reflector telescope, cryoPAF4 can expect to form 18 overlapping beams increasing the field of view by a factor of ~8x compared to a single pixel receiver of equal system temperature.

Here we summarize the initial results from a complex field radiation pattern measurement of a kinetic inductance detector instrument. These detectors are phase insensitive and have thus been limited to scalar, or amplitude-only, beam measurements. Vector beam scans, of both amplitude and phase, double the information received in comparison to scalar beam scans. Scalar beam measurements require multiple scans at varying distances along the optical path of the receiver to fully constrain the divergence angle of the optical system and locate the primary focus. Vector scans provide this information with a single scan, reducing the total measurement time required for new systems and also limiting the influence of system instabilities. The vector scan can be taken at any point along the optical axis of the system including the near-field, which makes beam measurements possible for large systems at high frequencies where these measurements may be inconceivable to be tested in-situ. Therefore, the methodology presented here should enable common heterodyne analysis for direct detector instruments. In principle, this coherent measurement strategy allows phase dependent analysis to be performed on any direct-detect receiver instrument.

We describe the current status, including preliminary design, characterization efforts, and recent progress, in the development of a spatial/spectral double Fourier laboratory-based interferometer testbed instrument within the Astronomical Instrumentation Group (AIG) laboratories at the University of Lethbridge, Canada (UL). Supported by CRC, CFI, and NSERC grants, this instrument development will provide laboratory demonstration of spatial-spectral interferometry with a concentration of furthering progress in areas including the development of spatial/spectral interferometry observation, data processing, characterization, and analysis techniques in the Far-Infrared (FIR) region of the electromagnetic spectrum.

novel type of the multichroic “seashell” resonant antenna is developed for CMB measurements. The polarized slot antennas are arranged in the compact form of a seashell with individual slots for each frequency and each polarization. Such an arrangement gives unique opportunity for independent adjusting individual parameters of slots with microstrip lines (MSL) and bolometers. For each frequency band the seashell antenna contains two pairs of orthogonal slots for each polarization connected by microstrip lines (MSL) with a bolometer in the middle for in-phase operation. To fit slots in λ/2 area for the best beam shape, lumped capacitances in the form of H-slot were introduced. Ellipticity of a beam was improved to the level of better than 1%.

The seashell antenna gives a unique opportunity to select needed bandwidth by resonant properties of slots themselves. Slots are phased by MSLs connecting two opposite slots with a resistive Cold-Electron Bolometer (CEB) placed just in middle of two MSLs. MSLs and CEBs are placed just in the area of the seashell antenna. The resonant seashell antenna with CEBs avoids long MSLs bringing signal outside the antenna to large external filters as in the case of sinuous antenna. This innovation avoids losses in long MSLs and increases frequency range.

We present the results from the magnetic field generation within the Kilopixel Array Pathfinder Project (KAPPa) instrument. The KAPPa instrument is a terahertz heterodyne receiver using a Superconducting-Insulating- Superconducting (SIS) mixers. To improve performance, SIS mixers require a magnetic field to suppress Josephson noise. The KAPPa test receiver can house a tunable electromagnet used to optimize the applied magnetic field. The receiver is also capable of accommodating a permanent magnet that applies a fixed field. Our permanent magnet design uses off-the-shelf neodymium permanent magnets and then reshapes the magnetic field using machined steel concentrators. These concentrators allow the use of an unmachined permanent magnet in the back of the detector block while two small posts provide the required magnetic field across the SIS junction in the detector cavity. The KAPPa test receiver is uniquely suited to compare the permanent magnet and electromagnet receiver performance. The current work includes our design of a ‘U’ shaped permanent magnet, the testing and calibration procedure for the permanent magnet, and the overall results of the performance comparison between the electromagnet and the permanent magnet counterpart.

The ALMA Band-1 receiver front-end prototype cold and warm cartridge assemblies, including the system and key components for ALMA Band-1 receivers have been developed and two sets of prototype cartridge were fully tested. The measured aperture efficiency for the cold receiver is above the 80% specification except for a few frequency points. Based on the cryogenically cooled broadband low-noise amplifiers provided by NRAO, the receiver noise temperature can be as low as 15 – 32K for pol-0 and 17 – 30K for pol-1. Other key testing items are also measured. The receiver beam pattern is measured, the results is well fit to the simulation and design. The pointing error extracted from the measured beam pattern indicates the error is 0.1 degree along azimuth and 0.15 degree along elevation, which is well fit to the specification (smaller than 0.4 degree). The equivalent hot load temperature for 5% gain compression is 492 - 4583K, which well fit to the specification of 5% with 373K input thermal load. The image band suppression is higher than 30 dB typically and the worst case is higher than 20 dB for 34GHz RF signal and 38GHz LO signal, which is all higher than 7 dB required specification. The cross talk between orthogonal polarization is smaller than -85 dB based on present prototype LO. The amplitude stability is below 2.0 x 10-7 , which is fit to the specification of 4.0 x 10-7 for timescales in the range of 0.05 s ≤ T ≤ 100 s. The signal path phase stability measured is smaller than 5 fs, which is smaller than 22 fs for Long term (delay drift) 20 s ≤ T < 300 sec. The IF output phase variation is smaller than 3.5° rms typically, and the specification is less than 4.5° rms. The measured IF output power level is -28 to -30.5 dBm with 300K input load. The measured IF output power flatness is less than 5.6 dB for 2GHz window, and 1.3dB for 31MHz window. The first batch of prototype cartridges will be installed on site for further commissioning on July of 2017.

We report the development of the new 4-beam, 2-polarization, 2-sideband, 100 GHz band SIS receiver "FOREST" (FOur beam REceiver System on the 45-m Telescope) and the results from commissioning and observations on the Nobeyama 45-m Telescope operated by Nobeyama Radio Observatory, a branch of National Astronomical Observatory of Japan. FOREST aims to add new capabilities of large-area mapping and simultaneous multi-line observation at 80 { 116 GHz band to the Nobeyama 45-m Telescope, which is one of the largest millimeter radio telescopes in the world. The configuration of the four beams is a quadrate of 2 x 2 with the separation between adjacent beams of 50". Beam size of each beam is ~ 15" at 115 GHz. Receiver noise temperature is as low as that of ALMA Band 3 receivers, so that mapping speed is more than four times as high as that of the other 100 GHz band receivers on the 45-m Telescope. The IF bandwidth is 8 GHz (4 { 12 GHz) realizing simultaneous ¹²CO(J = 1-0), ¹³CO(J = 1-0), and C¹⁸O(J = 1-0) observations. Cooled components inside of cryostat are modularized per beam. IF signals from the cryostat are processed by the room temperature IF system, and then passed to spectrometers. We have installed the FOREST receiver into the Nobeyama 45-m Telescope, evaluated its performance, and made large area mapping observations. These demonstrate the excellent performance of the FOREST receiver and the Nobeyama 45-m Telescope.