This PDF file contains the front matter associated with SPIE Proceedings Volume 7741, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

The CEA/LETI and CEA/SAp started the development of far-infrared filled bolometer arrays for space applications over a decade ago. The unique design of these detectors makes possible the assembling of large focal planes comprising thousands of bolometers running at 300 mK with very low power dissipation. Ten arrays of 16x16 pixels were thoroughly tested on the ground, and integrated in the Herschel/PACS instrument before launch in May 2009. These detectors have been successfully commissioned and are now operating in their nominal environment at the second Lagrangian point of the Earth-Sun system. In this paper we briefly explain the functioning of CEA bolometer arrays, and we present the properties of the detectors focusing on their noise characteristics, the effect of cosmic rays on the signal, the repeatability of the measurements, and the stability of the system.

SCUBA-2 is a state of the art 10,000 pixel submillimeter camera installed and being commissioned at the James Clerk Maxwell Telescope (JCMT) providing wide-field simultaneous imaging at wavelengths of 450 and 850 microns. At each wavelength there are four 32 by 40 sub-arrays of superconducting Transition Edge Sensor (TES) bolometers, each packaged with inline SQUID multiplexed readout and amplifier. In this paper we present the results of characterising individual 1280 bolometer science grade sub-arrays, both in a dedicated 50mk dilution refrigerator test facility and in the instrument installed at the JCMT.

An enhanced version of the "Polarimeter f¨ur bolometer Kameras" (PolKa) has been installed on the APEX telescope (Atacama Pathfinder EXperiment) in October 2009, to work in combination with LABOCA (the Large APEX Bolometer Camera). This polarimeter was included in the design of LABOCA's optics from the beginning and it is now going through a commissioning phase. Preliminary tests on sky have confirmed that the combination of PolKa, LABOCA and APEX provides unprecedented capabilities in mapping the polarization of the continuum emission at submillimeter wavelengths.

We present the results of the latest multicolor Microwave Kinetic Inductance Detector (MKID) focal plane arrays in the submillimeter. The new detectors on the arrays are superconducting resonators which combine a coplanar waveguide section with an interdigitated capacitor, or IDC. To avoid out-of-band pickup by the capacitor, a stepped-impedance filter is used to prevent radiation from reaching the absorptive aluminum section of the resonator. These arrays are tested in the preliminary demonstration instrument, DemoCam, a precursor to the Multicolor Submillimeter Inductance Camera, MUSIC. We present laboratory results of the responsivity to light both in the laboratory and at the Caltech Submillimeter Observatory. We assess the performance of the detectors in filtering out-of-band radiation, and find the level of excess load and its effect on detector performance. We also look at the array design characteristics, and the implications for the optimization of sensitivities expected by MUSIC.

Germanium photoconductors offer excellent sensitivity in the 50-140μm spectral range. Coupled with their modest cooling requirements and their compatibility with the silicon cryo-CMOS readout technology, these detectors are the most attractive candidates for far IR astronomy in this wavelength range. Over the years we have been pursuing the advancement of this technology and our initial effort has produced a 2x16 Ge:Sb array with an NEP in the low 10^-18 W/√Hz range, rivaling the best far IR arrays currently available. Further work has resulted in design and fabrication of a low noise, 2-side buttable 32x32 (64x64 mosaic) CTIA readout, the first 1k-pixel Ge:Sb fully assembled focal-plane array, a new hybrid design better suited for far IR photoconductors, and the preliminary design of a 2-side buttable 64x64 (128x128 mosaic) CTIA readout. Our developmental work continues and we believe that sensitivity levels below 10^-18 W/√Hz are within reach. This paper presents an overview of our progress so far and outlines our roadmap for further work.

We present the current status of the development of a far-infrared monolithic Ge:Ga photoconductor array proposed for the SAFARI instrument onboard SPICA, which is a future infrared space mission. SPICA has a large (3-m class) cooled (<6 K) telescope, which enables us to make astronomical observations with high spatial resolution and unprecedented sensitivity in the mid- and far-infrared wavelength. As a candidate detector to cover the 45-110 μm band of a far-infrared focal plan instrument of SAFARI, we are developing a large format monolithic Ge:Ga array. The monolithic Ge:Ga array is directly connected to cryogenic readout electronics (CRE) using the Au-Indium bumping technology. Our goal is to develop a 64×64 Ge:Ga array, on the basis of existing technologies and experience in making the 3×20 Ge:Ga monolithic arrays for the AKARI satellite. In order to realize a larger format array with better sensitivity than that of the AKARI array, we have been making some technical improvements; (1) development of the Au-In bumping technology to realize the large format array, (2) optimization of the structure of the transparent electrode to achieve the better sensitivity, (3) development of an anti-reflection coating to reduce interference fringe between the Ge substrate, and (4) Use of the low-noise cryogenic readout electronics with low power consumption. We fabricated the prototype 5×5 Ge:Ga arrays to demonstrate and evaluate the properties of monolithic array. We demonstrate experimentally the feasibility of these elemental technologies, and also show the results of performance measurements for the prototype Ge:Ga arrays.

We report on the development of a large-format stressed gallium doped germanium (Ge:Ge) array for the SAFARI instrument planned for the Japanese infrared satellite SPICA. Building on flight proven PACS heritage, the goal of our development is a 32 pixel stressed Ge:Ga module for the wavelength range between 110 and 210 μm, being the building block of a 32 × 32 pixel detector array. The unprecedented size of this array would allow the use of almost all of the 3.8 × 3.8 arcmin field of view available to SAFARI in the SPICA focal plane. Our 32 pixel prototype module features three selectable read-out architectures enabling the evaluation and optimization of the detector performance as well as a two stage multiplexer to distribute the dissipative heat load on the temperature stages provided by the satellite. Thermal modeling has shown that the heat loads are in compliance with the thermal budgets of the SPICA cryogenic system. The ultimate development goal with optimized read-out circuits is an NEP of 1 × 10^-18 W/Hz^1/2, which presents a factor of 8 improvement in noise performance compared to the PACS stressed Ge:Ga array.

The ArTeMiS submillimetric camera will observe simultaneously the sky at 450, 350 and 200 μm using 3 different focal planes made of 2304, 2304 and 1152 bolometric pixels respectively. This camera will be mounted in the Cassegrain cabin of APEX, a 12 m antenna located on the Chajnantor plateau, Chile. To realize the bolometric arrays, we have adapted the Silicon processing technology used for the Herschel-PACS photometer to account for higher incident fluxes and longer wavelengths from the ground. In addition, an autonomous cryogenic system has been designed to cool the 3 focal planes down to 300 mK. Preliminary performances obtained in laboratory with the first of 3 focal planes are presented. Latest results obtained in 2009 with the P-ArTeMiS prototype camera are also discussed, including massive protostellar cores and several star forming regions that have been clearly identified and mapped.

The Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry (BLAST-Pol) is a suborbital mapping experiment designed to study the role played by magnetic fields in the star formation process. BLAST-Pol is the reconstructed BLAST telescope, with the addition of linear polarization capability. Using a 1.8m Cassegrain telescope, BLAST-Pol images the sky onto a focal plane that consists of 280 bolometric detectors in three arrays, observing simultaneously at 250, 350, and 500μm. The diffraction-limited optical system provides a resolution of 30"at 250μm. The polarimeter consists of photolithographic polarizing grids mounted in front of each bolometer/ detector array. A rotating 4K achromatic half-wave plate provides additional polarization modulation. With its unprecedented mapping speed and resolution, BLAST-Pol will produce three-color polarization maps for a large number of molecular clouds. The instrument provides a much needed bridge in spatial coverage between larger-scale, coarse resolution surveys and narrow field of view, and high resolution observations of substructure within molecular cloud cores. The first science flight will be from McMurdo Station, Antarctica in December 2010.

MUSIC (the Multiwavelength Submillimeter kinetic Inductance Camera) is an instrument being developed for the Caltech Submillimeter Observatory by Caltech, JPL, the University of Colorado, and UCSB. MUSIC uses microwave kinetic inductance detectors (MKIDs) - superconducting micro-resonators - as photon detectors. The readout is almost entirely at room temperature and is highly multiplexed. MUSIC will have 576 spatial pixels in four bands at 850, 1100, 1300 and 2000 microns. MUSIC is scheduled for deployment at the CSO in the winter of 2010/2011. We present an overview of the camera design and readout and describe the current status of the instrument and some results from the highly successful May/June 2010 observing run at the CSO with the prototype camera, which verified the performance of the complete system (optics, antennas/filters, resonators, and readout) and produced the first simultaneous 3-color observations with any MKID camera.

The 6 K cooled primary mirror of the SPICA observatory, to be launched in 2018, allows a photometry gain in sensitivity in the far infrared of more than two orders of magnitude when compared with current instrumentation in space. All the proposed detector solutions will have to deploy radically different solutions from previous developments to cope with the extremely low background and very low power budgets available at all the temperature stages. We present the current design of very large "all Silicon" filled Bolometer Arrays cooled below 100 mK, and the solutions we develop for the BASIC (Bolometer Arrays for the All Silicon SAFARI Imaging Camera) focal planes of SAFARI. They will cover simultaneously three wavelength bands between 30 and 210 μm.

BICEP2/Keck and SPIDER are cosmic microwave background (CMB) polarimeters targeting the B-mode polarization induced by primordial gravitational waves from inflation. They will be using planar arrays of polarization sensitive antenna-coupled TES bolometers, operating at frequencies between 90 GHz and 220 GHz. At 150 GHz each array consists of 64 polarimeters and four of these arrays are assembled together to make a focal plane, for a total of 256 dual-polarization elements (512 TES sensors). The detector arrays are integrated with a time-domain SQUID multiplexer developed at NIST and read out using the multi-channel electronics (MCE) developed at the University of British Columbia. Following our progress in improving detector parameters uniformity across the arrays and fabrication yield, our main effort has focused on improving detector arrays optical and noise performances, in order to produce science grade focal planes achieving target sensitivities. We report on changes in detector design implemented to optimize such performances and following focal plane arrays characterization. BICEP2 has deployed a first 150 GHz science grade focal plane to the South Pole in December 2009.

We are developing dual-polarized multi-channel antenna-coupled Transition Edge Sensor (TES) Bolometers for Cosmic Microwave Background (CMB) Polarimetry in terrestrial experiments. Each pixel of the array couples incident power into the lithographed microstrip circuits with a dual-polarized broadband planar sinuous antenna who's gain is increased with a contacting extended hemispherical lens. Microstrip filter manifolds partition the two-octave bandwidth into narrow channels before terminating at separate TES bolometers. We describe the design methodology and fabrication methods used, and also the results of optical tests that show high optical throughput in properly located bands, as well as high cross-polarization rejection. We have explored two antenna feeding schemes that result in different quality beams and we comment on the relative merits of each. Finally, we quantify the increases in mapping speed that an array of our multichroic pixels might realize over traditional monochromatic pixels.

Transition edge sensor (TES) is the selected detector for the SAFARI FIR imaging spectrometer (focal plane arrays covering a wavelength range from 30 to 210 μm) on the Japanese SPICA telescope. Since the telescope is cooled to <7 K, the instrument sensitivity is limited by the detector noise. Therefore among all the requirements, a crucial one is the sensitivity, which should reach an NEP (Noise Equivalent Power) as low as 3E^-19 W/Hz^0.5 for a base temperature of >50 mK. Also the time constant should be below 8 ms. We fabricated and characterized low thermal conductance transition edge sensors (TES) for SAFARI instrument on SPICA. The device is based on a superconducting Ti/Au bilayer deposited on suspended SiN membrane. The critical temperature of the device is 155 mK. The low thermal conductance is realized by using narrow SiN ring-like supporting structures. All measurements were performed having the device in a light-tight box, which to a great extent eliminates the loading of the background radiation. We measured the current-voltage (IV) characteristics of the device in different bath temperatures and determine the thermal conductance (G) to be equal to 1.66 pW/K. This value corresponds to a noise equivalent power (NEP) of 1E^-18 W/√Hz. The current noise and complex impedance is also measured at different bias points at 25 mK bath temperature. The measured electrical (dark) NEP is 2E^-18 W/√Hz, which is about a factor of 2 higher than what we expect from the thermal conductance that comes out of the IV curves. Despite using a light-tight box, the photon noise might still be the source of this excess noise. We also measured the complex impedance of the same device at several bias points. Fitting a simple first order thermal-electrical model to the measured data, we find an effective time constant of about 65 μs and a thermal capacity of 3-4 fJ/K in the middle of the transition

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 have fabricated absorber-coupled microwave kinetic inductance detector (MKID) arrays for sub-millimeter and farinfrared astronomy. Each detector array is comprised of λ/2 stepped impedance resonators, a 1.5μm thick silicon membrane, and 380μm thick silicon walls. The resonators consist of parallel plate aluminum transmission lines coupled to low impedance Nb microstrip traces of variable length, which set the resonant frequency of each resonator. This allows for multiplexed microwave readout and, consequently, good spatial discrimination between pixels in the array. The Al transmission lines simultaneously act to absorb optical power and are designed to have a surface impedance and filling fraction so as to match the impedance of free space. Our novel fabrication techniques demonstrate high fabrication yield of MKID arrays on large single crystal membranes and sub-micron front-to-back alignment of the microstrip circuit.

Detectors employing superconducting microwave kinetic inductance detectors (MKIDs) can be read out by measuring changes in either the resonator frequency or dissipation. We will discuss the pros and cons of both methods, in particular, the readout method strategies being explored for the Multiwavelength Sub/millimeter Inductance Camera (MUSIC) to be commissioned at the CSO in 2010. As predicted theoretically and observed experimentally, the frequency responsivity is larger than the dissipation responsivity, by a factor of 2-4 under typical conditions. In the absence of any other noise contributions, it should be easier to overcome amplifier noise by simply using frequency readout. The resonators, however, exhibit excess frequency noise which has been ascribed to a surface distribution of two-level fluctuators sensitive to specific device geometries and fabrication techniques. Impressive dark noise performance has been achieved using modified resonator geometries employing interdigitated capacitors (IDCs). To date, our noise measurement and modeling efforts have assumed an onresonance readout, with the carrier power set well below the nonlinear regime. Several experimental indicators suggested to us that the optimal readout technique may in fact require a higher readout power, with the carrier tuned somewhat off resonance, and that a careful systematic study of the optimal readout conditions was needed. We will present the results of such a study, and discuss the optimum readout conditions as well as the performance that can be achieved relative to BLIP.

Efficient optical modelling in the far infrared is challenging because of the dominance of diffraction effects in typical astronomical instruments. With the development of the next generation of array imagers and multi-moded feed systems the necessity for computational efficiency has become critical to ensure an optimised design, comprehensive system and telescope analysis and image deconvolution. A multi-technique capability is necessary to simulate both efficiently and accurately the propagation of the signal collected by the telescope through the quasi-optical beam guide and feed structures using an appropriate combination of modelling tools, seamlessly passing from one regime to the next from detector to sky. Physical optics for example, although computationally intensive, is useful tool when detailed telescope beam analysis is required, particularly for providing cross-polarisation information. Modal analysis is often appropriate for modelling beam guide structures while analysing the detector feed coupling may rely on a more complete electromagnetic analysis because of the small sizes involved and the use of waveguide and planar structures. Image recovery ideally requires a deconvolution technique based on a modal approach and precise knowledge of the beams on the sky. In this paper we report on our work in the continued development of such appropriate techniques with the particular goal of prototyping powerful efficient computational tools for imaging arrays and partially coherent systems. In the presentation, we will discuss these issues and present examples from real instrumentation.

We have recently developed a repeatable and reliable technique for anti-reflection coating large lenses, suitable for use at sub-mm wavelengths. Small lenses have been coated using this technique, and are currently flying on-board Herschel- SPIRE and Planck-HFI. We have recently coated much larger, highly-curved lenses (up to 380 mm diameter) for the EBEX and Polarbear cosmic microwave background (CMB) experiments. In this paper, we present details of the coating technique, experimental results of coated samples, and comparison of the results to theoretical predictions. We also present an indication of their technology readiness level (TRL) for future space applications such as B-Pol.

Next generation cosmic microwave background (CMB) polarization anisotropy measurements will feature focal plane arrays with more than 600 millimeter-wave detectors. We make use of high-resolution photolithography and wafer-scale etch tools to build planar arrays of corrugated platelet feeds in silicon with highly symmetric beams, low cross-polarization and low side lobes. A compact Au-plated corrugated Si feed designed for 150 GHz operation exhibited performance equivalent to that of electroformed feeds: ~ -0.2 dB insertion loss, < -20 dB return loss from 120 GHz to 170 GHz, < -25 dB side lobes and < -23 dB cross-polarization. We are currently fabricating a 50mm diameter array with 84 horns consisting of 33 Si platelets as a prototype for the SPTpol and ACTpol telescopes. Our fabrication facilities permit arrays up to 150mm in diameter.

The goal of a large (25 m) submillimeter telescope with high aperture efficiencies up to frequencies of ~ 1 THz requires a wavefront sensor able to measure the telescope surface figure to an accuracy of order 1 micron, better than has been achieved to date in the millimeter/submillimeter (MSM) regime. On the other hand, the recent availability of largeformat submillimeter detector arrays suggests that new techniques can be applied. In particular, using submillimeter focal plane arrays, variants of interferometric pupil-plane wavefront sensing techniques familiar from the optical/infrared (OIR) regime could perhaps be applied profitably in the MSM. However, while many possibilities can in principle be considered, many of these possibilities would be unwieldy in the MSM, because of the need for large off-axis reflective optical elements, and the consequent sizeable optical layout. However, the overall size of an interferometer can be minimized by making use of a common-path interferometer. Here we thus consider the applicability to MSM wavefront sensing of a rather simple common-path pupil-plane interferometer, specifically a scanning version of the fixed-phase phase-contrast interferometers described in different contexts by Zernicke¹ and Dicke². Both transmissive and reflective solutions for the needed phase shifting interferometers are possible, but here we focus on the reflective case as a proof of principle. Such a common-path phase-shifting interferometer has several potential advantages: relative simplicity, compactness, ease of manufacturability, reduced systematic effects, and high accuracy.

Bicep2 deployed to the South Pole during the 2009-2010 austral summer, and is now mapping the polarization of the cosmic microwave background (CMB), searching for evidence of inflationary cosmology. Bicep2 belongs to a new class of telescopes including Keck (ground-based) and Spider (balloon-borne) that follow on Bicep's strategy of employing small, cold, on-axis refracting optics. This common design provides key advantages ideal for targeting the polarization signature from inflation, including: (i) A large field of view, allowing substantial light collecting power despite the small aperture, while still resolving the degree-scale polarization of the CMB; (ii) liquid helium-cooled optics and cold stop, allowing for low, stable instrument loading; (iii) the ability to rotate the entire telescope about the boresight; (iv) a baffled primary aperture, reducing sidelobe pickup; and (v) the ability to characterize the far field optical performance of the telescope using ground-based sources. We describe the last of these advantages in detail, including our efforts to measure the main beam shape, beammatch between orthogonally-polarized pairs, polarization efficiency and response angle, sidelobe pickup, and ghost imaging. We do so with ground-based polarized microwave sources mounted in the far field as well as with astronomical calibrators. Ultimately, Bicep2's sensitivity to CMB polarization from inflation will rely on precise calibration of these beam features.

We will present the design and implementation, along with calculations and some measurements of the performance, of the room-temperature and cryogenic optics for MUSIC, a new (sub)millimeter camera we are developing for the Caltech Submm Observatory (CSO). The design consists of two focusing elements in addition to the CSO primary and secondary mirrors: a warm off-axis elliptical mirror and a cryogenic (4K) lens. These optics will provide a 14 arcmin field of view that is diffraction limited in all four of the MUSIC observing bands (2.00, 1.33, 1.02, and 0.86 mm). A cold (4K) Lyot stop will be used to define the primary mirror illumination, which will be maximized while keeping spillover at the sub 1% level. The MUSIC focal plane will be populated with broadband phased antenna arrays that efficiently couple to factor of (see manuscript) 3 in bandwidth,^{1, 2} and each pixel on the focal plane will be read out via a set of four lumped element filters that define the MUSIC observing bands (i.e., each pixel on the focal plane simultaneously observes in all four bands). Finally, a series of dielectric and metal-mesh low pass filters have been implemented to reduce the optical power load on the MUSIC cryogenic stages to a quasi-negligible level while maintaining good transmission in-band.

We report on both laboratory and telescope integration results from SuperCam, a 64 pixel imaging spectrometer designed for operation in the astrophysically important 870 micron atmospheric window. SuperCam will be used to answer fundamental questions about the physics and chemistry of molecular clouds in the Galaxy and their direct relation to star and planet formation. The SuperCam key project is a fully sampled Galactic plane survey covering over 500 square degrees of the Galaxy in ¹²CO(3-2) and ¹³CO(3-2) with 0.3 km/s velocity resolution In the past, all heterodyne focal plane arrays have been constructed using discrete mixers, arrayed in the focal plane. SuperCam reduces cryogenic and mechanical complexity by integrating multiple mixers and amplifiers into a single array module with a single set of DC and IF connectors. These modules are housed in a closed-cycle cryostat with a 1.5W capacity 4K cooler. The SuperCam instrument is currently undergoing laboratory testing with four of the eight mixer array modules installed in the cryostat (32 pixels). Work is now underway to perform the necessary modifications at the 10m Heinrich Hertz Telescope to accept the SuperCam system. SuperCam will be installed in the cassegrain cabin of the HHT, including the optical system, IF processing, spectrometers and control electronics. SuperCam will be integrated with the HHT during the 2009-2010 observing season with 32 pixels installed. The system will be upgraded to 64 pixels during the summer of 2010 after assembly of the four additional mixer modules is completed.

ZEUS-2, the second generation (z)Redshift and Early Universe Spectrometer, like its predecessor is a moderate resolution (R~1000) long-slit, echelle grating spectrometer optimized for the detection of faint, broad lines from distant galaxies. It is designed for studying star-formation across cosmic time. ZEUS-2 employs three TES bolometer arrays (555 pixels total) to deliver simultaneous, multi-beam spectra in up to 4 submillimeter windows. The NIST Boulder-built arrays operate at ~100mK and are readout via SQUID multiplexers and the Multi-Channel Electronics from the University of British Columbia. The instrument is cooled via a pulse-tube cooler and two-stage ADR. Various filter configurations give ZEUS-2 access to 7 different telluric windows from 200 to 850 micron enabling the simultaneous mapping of lines from extended sources or the simultaneous detection of the 158 micron [CII] line and the [NII] 122 or 205 micron lines from z = 1-2 galaxies. ZEUS-2 is designed for use on the CSO, APEX and possibly JCMT.

In the wavelength regime between 60 and 300 microns there are a number of atomic and molecular emission lines that are key diagnostic probes of the interstellar medium. These include transitions of [CII], [NII], [OI], HD, H₂D+, OH, CO, and H₂O, some of which are among the brightest global and local far-infrared lines in the Galaxy. In Giant Molecular Clouds (GMCs), evolved star envelopes, and planetary nebulae, these emission lines can be extended over many arc minutes and possess complicated, often self absorbed, line profiles. High spectral resolution (R> 10⁵) observations of these lines at sub-arcminute angular resolution are crucial to understanding the complicated interplay between the interstellar medium and the stars that form from it. This feedback is central to all theories of galactic evolution. Large format heterodyne array receivers can provide the spectral resolution and spatial coverage to probe these lines over extended regions. The advent of large format (~100 pixel) spectroscopic imaging cameras in the far-infrared (FIR) will fundamentally change the way astronomy is performed in this important wavelength regime. While the possibility of such instruments has been discussed for more than two decades, only recently have advances in mixer and local oscillator technology, device fabrication, micromachining, and digital signal processing made the construction of such instruments tractable. These technologies can be implemented to construct a sensitive, flexible, heterodyne array facility instrument for SOFIA. The instrument concept for StratoSTAR: Stratospheric Submm/THz Array Receiver includes a common user mounting, control system, IF processor, spectrometer, and cryogenic system. The cryogenic system will be designed to accept a frontend insert. The frontend insert and associated local oscillator system/relay optics would be provided by individual user groups and reflect their scientific interests. Rapid technology development in this field makes SOFIA the ideal platform to operate such a modular, continuously evolving instrument.

We present the design of a broadband superconductor-insulator-superconductor (SIS) mixer operating near 700 GHz. A key feature of our design is the utilisation of a new type of waveguide to planar circuit transition comprising a unilateral finline taper. This transition is markedly easier to design, simulate and fabricate than the antipodal finline we employed previously. The finline taper and the superconducting circuitry are deposited on a 15 μm thick silicon substrate. The employment of the very thin substrate, achieved using Silicon-On-Insulator (SOI) technology, makes it easy to match the incoming signal to the loaded waveguide. The lightweight mixer chip is held in the E-plane of the waveguide using gold beam leads, avoiding the need for deep grooves in the waveguide wall. This new design yields a significantly shorter chip, free of serrations and a wider RF bandwidth. Since tuning and all other circuits are integrated on the mixer chip, the mixer block is extremely simple, comprising a feed horn and a waveguide section without any complicated mechanical features. We employ a new type of smooth-walled horn which exhibits excellent beam circularity and low cross polarisation, comparable to the conventional corrugated horn, and yet is easier to fabricate. The horn is machined by standard milling with a drill tool shaped into the horn profile. In this paper, we describe the detailed design of the mixer chip including electromagnetic simulations, and the mixer performance obtained with SuperMix simulations. We also present the preliminary measurements of the smooth-walled horn radiation patterns near the mixer operating frequencies.

Heterodyne spectroscopy of molecular rotational lines and atomic fine-structure lines is a powerful tool in astronomy and planetary research. One example is the OI fine structure line at 4.7 THz. This is a main target for the observation with GREAT, the German Receiver for Astronomy at Terahertz Frequencies, which will be operated on board of SOFIA. We report on the development of a compact, easy-to-use source, which combines a quantum-cascade laser (QCL) with a compact, low-input-power Stirling cooler. This work is part of the local-oscillator development for GREAT/SOFIA. The QCL, which is based on a two-miniband design, has been developed for high output power and low electrical pump power. Efficient carrier injection is achieved by resonant longitudinal optical phonon scattering. The amount of generated heat complies with the cooling capacity of the Stirling cooler. The whole system weighs less than 15 kg including cooler, power supplies etc. The output power is above 1 mW. With an appropriate optical beam shaping, the emission profile of the laser becomes a fundamental Gaussian one. Sub-MHz frequency accuracy can be achieved by locking the emission of the QCL to a molecular resonance.

Recent results from the Heterodyne Instrument for Far-Infrared (HIFI) on the Herschel Space Telescope have confirmed the usefulness of high resolution spectroscopic data for a better understanding of our Universe. This paper will explore the current status of tunable local oscillator sources beyond HIFI and provide demonstration of how power combining of GaAs Schottky diodes can be used to increase both power and upper operating frequency for heterodyne receivers. Availability of power levels greater than 1 watt in the W-band now makes it possible to design a 1900 GHz source with more than 100 microwatts of expected output power.

The size of existing and projected submillimeter heterodyne receiver arrays is rapidly increasing. As receiver arrays grow ever larger, the local oscillator power they require increases as well. We have developed Terahertz (THz) Traveling Wave Tube Amplifiers (TWTA) that promise to provide more than enough power in the 200 to 700 GHz frequency range to pump the largest arrays being planned for submillimeter telescopes. This technology combines revolutionary carbon nanotube cathodes and electron gun design with unique software modeling and micro-fabrication capabilities. We review key enabling technologies that make this breakthrough possible, present the design, realization, computer models and preliminary results of the THz TWT we have fabricated at 220 and 350 GHz

NTU-Array is designed for W-band (78-113Ghz) interferometric observations of Sunyaev-Zeldovich effects. The first phase operation of the telescope with 6 receivers had its first light in 2008 with single-polarization and half the full bandwidth. The second-phase operation of NTU-Array in Nevada will begin the dual-polarization, full-band observation in 2010. One-bit sampling at 18Ghz and digital correlation are in use in this telescope. Due to the ultra broadband coverage, the IF system divides the 35GHz full-band into four 8.7GHz sub-bands. The first stage of IF module containing a 35GHz broadband amplifier with fairly flat-gain performance over 25db gain divides the first-stage IF into two outputs. The 2nd-stage IF module further divides the two input IF signals and down-converts them to four basebands of DC-8.7Ghz. An LO module with 8.7Ghz input is to generate outputs with x2, x3 and x9 harmonics for the down-conversion. The Walsh function is injected into the x9 LO via an IQ mixer. Each IF baseband is transmitted through an optical link to the 18Ghz, 1-bit sampling ADC located in the control room. The analog optical link contains a driver and equalizer to compensate for the path loss. Considering the limited size of the telescope mount, the entire IF/LO system of each receiver has a compact size about 20cm cubed. This physical size can be further reduced to fit the future 19-pixel-receiver upgrade of NTU-Array

High-resolution heterodyne spectrometers operating at above 2 THz are crucial for detecting, e.g., the HD line at 2.7 THz and oxygen OI line at 4.7 THz in astronomy. The potential receiver technology is a combination of a hot electron bolometer (HEB) mixer and a THz quantum cascade laser (QCL) local oscillator (LO).Here we report the first highresolution heterodyne spectroscopy measurement of a gas cell using such a HEB-QCL receiver. The receiver employs a 2.9 THz free-running QCL as local oscillator and a NbN HEB as a mixer. By using methanol (CH₃OH) gas as a signal source, we successfully recorded the methanol emission line at 2.92195 THz. Spectral lines at IF frequency at different pressures were measured using a FFTS and well fitted with a Lorentzian profile. Our gas cell measurement is a crucial demonstration of the QCL as LO for practical heterodyne instruments. Together with our other experimental demonstrations, such as using a QCL at 70 K to operate a HEB mixer and the phase locking of a QCL such a receiver is in principle ready for a next step, which is to build a real instrument for any balloon-, air-, and space-borne observatory.

We present an overview of the recent progress made in the development of a far-IR array of ultrasensitive hot-electron nanobolometers (nano-HEB) made from thin titanium (Ti) films. We studied electrical noise, signal and noise bandwidth, single-photon detection, optical noise equivalent power (NEP), and a microwave SQUID (MSQUID) based frequency domain multiplexing (FDM) scheme. The obtained results demonstrate the very low electrical NEP down to 1.5×10^-20 W/Hz^1/2 at 50 mK determined by the dominating phonon noise. The NEP increases with temperature as ~ T³ reaching ~ 10^-17 W/Hz^1/2 at the device critical temperature T_C = 330-360 mK. Optical NEP = 8.6×10^-18 W/Hz^1/2 at 357 mK and 1.4×10^-18 W/Hz^1/2 at 100 mK respectively, agree with thermal and electrical data. The optical coupling efficiency provided by a planar antenna was greater than 50%. Single 8-μm photons have been detected for the first time using a nano-HEB operating at 50-200 mK thus demonstrating a potential of these detectors for future photon-counting applications in mid-IR and far-IR. In order to accommodate the relatively high detector speed (~ μs at 300 mK, ~ 100 μs at 100 mK), an MSQUID based FDM multiplexed readout with GHz carrier frequencies has been built. Both the readout noise ~ 2 pA/Hz^1/2 and the bandwidth > 150 kHz are suitable for nano-HEB detectors.

The Cold-Electron Bolometer (CEB) is a sensitive millimetre-wave detector which is easy to integrate with superconducting planar circuits. CEB detectors have other important features such as high saturation power and very fast response. We have fabricated and tested CEB detectors integrated across the slot of a unilateral finline on a silicon substrate. Bolometers were fabricated using two fabrication methods: e-beam direct-write trilayer technology and an advanced shadow mask evaporation technique. The CEB performance was tested in a He³ sorption cryostat at a bath temperature of 280mK. DC I-V curves and temperature responses were measured in a current bias mode, and preliminary measurements of the optical response were made using an IMPATT diode operating at 110GHz. These tests were conducted by coupling power directly into the finline chip, without the use of waveguide or feedhorns. For the devices fabricated in standard direct-write technology, the bolometer dark electrical noise equivalent power is estimated to be about 5×10^-16W/√Hz, while the dark NEP value for the shadow mask evaporation technique devices is estimated to be as low as 3×10^-17W/√Hz.

We report the sensitivity of a superconducting NbN hot electron bolometer mixer integrated with a tight spiral antenna at 5.3 THz. Using a measurement setup with black body calibration sources and a beam splitter in vacuo, and an antireflection coated Si lens, we obtained a double sideband receiver noise temperature of 1150 K, which is 4.5 times hν/kB (quantum limit). Our experimental results in combination with an antenna-to-bolometer coupling simulation suggest that HEB mixer can work well at least up to 6 THz, suitable for next generation of high-resolution spectroscopic of the neutral atomic oxygen (OI) line at 4.7 THz.

EBEX is a NASA-funded balloon-borne experiment designed to measure the polarization of the cosmic microwave background (CMB). Observations will be made using 1432 transition edge sensor (TES) bolometric detectors read out with frequency multiplexed SQuIDs. EBEX will observe in three frequency bands centered at 150, 250, and 410 GHz, with 768, 384, and 280 detectors in each band, respectively. This broad frequency coverage is designed to provide valuable information about polarized foreground signals from dust. The polarized sky signals will be modulated with an achromatic half wave plate (AHWP) rotating on a superconducting magnetic bearing (SMB) and analyzed with a fixed wire grid polarizer. EBEX will observe a patch covering ~1% of the sky with 8' resolution, allowing for observation of the angular power spectrum from l = 20 to 1000. This will allow EBEX to search for both the primordial B-mode signal predicted by inflation and the anticipated lensing B-mode signal. Calculations to predict EBEX constraints on r using expected noise levels show that, for a likelihood centered around zero and with negligible foregrounds, 99% of the area falls below r = 0.035. This value increases by a factor of 1.6 after a process of foreground subtraction. This estimate does not include systematic uncertainties. An engineering flight was launched in June, 2009, from Ft. Sumner, NM, and the long duration science flight in Antarctica is planned for 2011. These proceedings describe the EBEX instrument and the North American engineering flight.

QUIET is an experimental program to measure the polarization of the Cosmic Microwave Background (CMB) radiation from the ground. Previous CMB polarization data have been used to constrain the cosmological parameters that model the history of our universe. The exciting target for current and future experiments is detecting and measuring the faint polarization signals caused by gravity waves from the inflationary epoch which occurred < 10^-30 s after the Big Bang. QUIET has finished an observing season at 44 GHz (Q-Band); observing at 95 GHz (W-Band) is ongoing. The instrument incorporates several technologies and approaches novel to CMB experiments. We describe the observing strategy, optics design, detector technology, and data acquisition. These systems combine to produce a polarization sensitivity of 64 (57) μK for a 1 s exposure of the Phase I Q (W) Band array. We describe the QUIET Phase I instrument and explain how systematic errors are reduced and quantified.

POLARBEAR is a Cosmic Microwave Background (CMB) polarization experiment that will search for evidence of inflationary gravitational waves and gravitational lensing in the polarization of the CMB. This proceeding presents an overview of the design of the instrument and the architecture of the focal plane, and shows some of the recent tests of detector performance and early data from the ongoing engineering run.

The Bicep2 telescope is designed to measure the polarization of the cosmic microwave background on angular scales near 2-4 degrees, near the expected peak of the B-mode polarization signal induced by primordial gravitational waves from inflation. Bicep2 follows the success of Bicep, which has set the most sensitive current limits on B-modes on 2-4 degree scales. The experiment adopts a new detector design in which beam-defining slot antennas are coupled to TES detectors photolithographically patterned in the same silicon wafer, with multiplexing SQUID readout. Bicep2 takes advantage of this design's higher focal-plane packing density, ease of fabrication, and multiplexing readout to field more detectors than Bicep1, improving mapping speed by nearly a factor of 10. Bicep2 was deployed to the South Pole in November 2009 with 500 polarization-sensitive detectors at 150 GHz, and is funded for two seasons of observation. The first months' data demonstrate the performance of the Caltech/JPL antenna-coupled TES arrays, and two years of observation with Bicep2 will achieve unprecedented sensitivity to B-modes on degree angular scales.

We report on the preliminary detector performance of the Bicep2 mm-wave polarimeter, deployed in 2009 to the South Pole. Bicep2 is currently imaging the polarization of the cosmic microwave background at 150 GHz using an array of 512 antenna-coupled superconducting bolometers. The antennas, band-defining filters and transition edge sensor (TES) bolometers are photolithographically fabricated on 4 silicon tiles. Each tile consists of an 8×8 grid of ~7 mm spatial pixels, for a total of 256 detector pairs. A spatial pixel contains 2 sets of orthogonal antenna slots summed in-phase, with each set coupled to a TES by a filtered microstrip. The detectors are read out using time-domain multiplexed SQUIDs. The detector pair of each spatial pixel is differenced to measure polarization. We report on the performance of the Bicep2 detectors in the field, including the focal plane yield, detector and multiplexer optimization, detector noise and stability, and a preliminary estimate of the improvement in mapping speed compared to Bicep1.

The C-Band All-Sky Survey (C-BASS) aims to produce sensitive, all-sky maps of diffuse Galactic emission at 5 GHz in total intensity and linear polarization. These maps will be used (with other surveys) to separate the several astrophysical components contributing to microwave emission, and in particular will allow an accurate map of synchrotron emission to be produced for the subtraction of foregrounds from measurements of the polarized Cosmic Microwave Background. We describe the design of the analog instrument, the optics of our 6.1 m dish at the Owens Valley Radio Observatory, the status of observations, and first-look data.

Over preceding conferences, the design and implementation of the SCUBA-2 (Sub-millimeter Common-User Bolometric Array 2) instrument hardware has been described in detail. SCUBA-2 has been installed on the James Clerk Maxwell Telescope (JCMT) for over two years and its hardware has been successfully commissioned. This paper describes the culmination of this process and compares the optical/mechanical design and test expectations of the instrument hardware against the performance achieved in the field.

MUSIC (Multicolor Submillimeter kinetic Inductance Camera) is a new facility instrument for the Caltech Submillimeter Observatory (Mauna Kea, Hawaii) developed as a collaborative effect of Caltech, JPL, the University of Colorado at Boulder and UC Santa Barbara, and is due for initial commissioning in early 2011. MUSIC utilizes a new class of superconducting photon detectors known as microwave kinetic inductance detectors (MKIDs), an emergent technology that offers considerable advantages over current types of detectors for submillimeter and millimeter direct detection. MUSIC will operate a focal plane of 576 spatial pixels, where each pixel is a slot line antenna coupled to multiple detectors through on-chip, lumped-element filters, allowing simultaneously imaging in four bands at 0.86, 1.02, 1.33 and 2.00 mm. The MUSIC instrument is designed for closed-cycle operation, combining a pulse tube cooler with a two-stage Helium-3 adsorption refrigerator, providing a focal plane temperature of 0.25 K with intermediate temperature stages at approximately 50, 4 and 0.4 K for buffering heat loads and heat sinking of optical filters. Detector readout is achieved using semi-rigid coaxial cables from room temperature to the focal plane, with cryogenic HEMT amplifiers operating at 4 K. Several hundred detectors may be multiplexed in frequency space through one signal line and amplifier. This paper discusses the design of the instrument cryogenic hardware, including a number of features unique to the implementation of superconducting detectors. Predicted performance data for the instrument system will also be presented and discussed.

We describe the cryogenic system for SPIDER, a balloon-borne microwave polarimeter that will map 8% of the sky with degree-scale angular resolution. The system consists of a 1284 L liquid helium cryostat and a 16 L capillary-filled superfluid helium tank, which provide base operating temperatures of 4 K and 1.5 K, respectively. Closed-cycle ³He adsorption refrigerators supply sub-Kelvin cooling power to multiple focal planes, which are housed in monochromatic telescope inserts. The main helium tank is suspended inside the vacuum vessel with thermally insulating fiberglass flexures, and shielded from thermal radiation by a combination of two vapor cooled shields and multi-layer insulation. This system allows for an extremely low instrumental background and a hold time in excess of 25 days. The total mass of the cryogenic system, including cryogens, is approximately 1000 kg. This enables conventional long duration balloon flights. We will discuss the design, thermal analysis, and qualification of the cryogenic system.

We describe SPIDER, a balloon-borne instrument to map the polarization of the millimeter-wave sky with degree angular resolution. Spider consists of six monochromatic refracting telescopes, each illuminating a focal plane of large-format antenna-coupled bolometer arrays. A total of 2,624 superconducting transition-edge sensors are distributed among three observing bands centered at 90, 150, and 280 GHz. A cold half-wave plate at the aperture of each telescope modulates the polarization of incoming light to control systematics. SPIDER's first flight will be a 20-30-day Antarctic balloon campaign in December 2011. This flight will map ~8% of the sky to achieve unprecedented sensitivity to the polarization signature of the gravitational wave background predicted by inflationary cosmology. The SPIDER mission will also serve as a proving ground for these detector technologies in preparation for a future satellite mission.

Here we describe the design and performance of the SPIDER instrument. SPIDER is a balloon-borne cosmic microwave background polarization imager that will map part of the sky at 90, 145, and 280 GHz with subdegree resolution and high sensitivity. This paper discusses the general design principles of the instrument inserts, mechanical structures, optics, focal plane architecture, thermal architecture, and magnetic shielding of the TES sensors and SQUID multiplexer. We also describe the optical, noise, and magnetic shielding performance of the 145 GHz prototype instrument insert.

The Primordial Inflation Polarization Explorer (PIPER) is a balloon-borne instrument designed to search for the faint signature of inflation in the polarized component of the cosmic microwave background (CMB). Each flight will be configured for a single frequency, but in order to aid in the removal of the polarized foreground signal due to Galactic dust, the filters will be changed between flights. In this way, the CMB polarization at a total of four different frequencies (200, 270, 350, and 600 GHz) will be measured on large angular scales. PIPER consists of a pair of cryogenic telescopes, one for measuring each of Stokes Q and U in the instrument frame. Each telescope receives both linear orthogonal polarizations in two 32 × 40 element planar arrays that utilize Transition-Edge Sensors (TES). The first element in each telescope is a variable-delay polarization modulator (VPM) that fully modulates the linear Stokes parameter to which the telescope is sensitive. There are several advantages to this architecture. First, by modulating at the front of the optics, instrumental polarization is unmodulated and is therefore cleanly separated from source polarization. Second, by implementing this system with the appropriate symmetry, systematic effects can be further mitigated. In the PIPER design, many of the systematics are manifest in the unmeasured linear Stokes parameter for each telescope and thus can be separated from the desired signal. Finally, the modulation cycle never mixes the Q and U linear Stokes parameters, and thus residuals in the modulation do not twist the observed polarization vector. This is advantageous because measuring the angle of linear polarization is critical for separating the inflationary signal from other polarized components.

We are constructing the Primordial Inflation Polarization Explorer (PIPER) to measure the polarization of the cosmic microwave background (CMB) and search for the imprint of gravity waves produced during an inflationary epoch in the early universe. The signal is faint and lies behind confusing foregrounds, both astrophysical and cosmological, and so many detectors are required to complete the measurement in a limited time. We will use four of our matured 1,280 pixel, high-filling-factor backshort-under-grid bolometer arrays for efficient operation at the PIPER CMB wavelengths. All four arrays observe at a common wavelength set by passband filters in the optical path. PIPER will fly four times to observe at wavelengths of 1500, 1100, 850, and 500 μm in order to separate CMB from foreground emission. The arrays employ leg-isolated superconducting transition edge sensor bolometers operated at 128 mK; tuned resonant backshorts for efficient optical coupling; and a second-generation superconducting quantum interference device (SQUID) multiplexer readout. We describe the design, development, and performance of PIPER bolometer array technology to achieve background-limited sensitivity for a cryogenic balloon-borne telescope.

The Keck Array is a cosmic microwave background (CMB) polarimeter that will begin observing from the South Pole in late 2010. The initial deployment will consist of three telescopes similar to BICEP2 housed in ultracompact, pulse tube cooled cryostats. Two more receivers will be added the following year. In these proceedings we report on the design and performance of the Keck cryostat. We also report some initial results on the performance of antenna-coupled TES detectors operating in the presence of a pulse tube. We find that the performance of the detectors is not seriously impacted by the replacement of BICEP2's liquid helium cryostat with a pulse tube cooled cryostat.

The six-meter Atacama Cosmology Telescope (ACT) in Chile was built to measure the cosmic microwave background (CMB) at arcminute angular scales. We are building a new polarization sensitive receiver for ACT (ACTPol). ACTPol will characterize the gravitational lensing of the CMB and aims to constrain the sum of the neutrino masses with ~ 0.05 eV precision, the running of the spectral index of inflation-induced fluctuations, and the primordial helium abundance to better than 1 %. Our observing fields will overlap with the SDSS BOSS survey at optical wavelengths, enabling a variety of cross-correlation science, including studies of the growth of cosmic structure from Sunyaev-Zel'dovich observations of clusters of galaxies as well as independent constraints on the sum of the neutrino masses. We describe the science objectives and the initial receiver design.

EBEX (the E and B EXperiment) is a balloon-borne telescope designed to measure the polarisation of the cosmic microwave background radiation. During a two week long duration science flight over Antarctica, EBEX will operate 768, 384 and 280 spider-web transition edge sensor (TES) bolometers at 150, 250 and 410 GHz, respectively. The 10-hour EBEX engineering flight in June 2009 over New Mexico and Arizona provided the first usage of both a large array of TES bolometers and a Superconducting QUantum Interference Device (SQUID) based multiplexed readout in a space-like environment. This successful demonstration increases the technology readiness level of these bolometers and the associated readout system for future space missions. A total of 82, 49 and 82 TES detectors were operated during the engineering flight at 150, 250 and 410 GHz. The sensors were read out with a new SQUID-based digital frequency domain multiplexed readout system that was designed to meet the low power consumption and robust autonomous operation requirements presented by a balloon experiment. Here we describe the system and the remote, automated tuning of the bolometers and SQUIDs. We compare results from tuning at float to ground, and discuss bolometer performance during flight.

This paper will present the design, implementation, performance analysis of an open source readout system for arrays of microwave kinetic inductance detectors (MKID) for mm/submm astronomy. The readout system will perform frequency domain multiplexed real-time complex microwave transmission measurements in order to monitor the instantaneous resonance frequency and dissipation of superconducting microresonators. Each readout unit will be able to cover up to 550 MHz bandwidth and readout 256 complex frequency channels simultaneously. The digital electronics include the customized DAC, ADC, IF system and the FPGA based signal processing hardware developed by CASPER group.^1-7 The entire system is open sourced, and can be customized to meet challenging requirement in many applications: e.g. MKID, MSQUID etc.

Commissioning of SCUBA-2 included a program of skydips and observations of calibration sources intended to be folded into regular observing as standard methods of source flux calibration and to monitor the atmospheric opacity and stability. During commissioning, it was found that these methods could also be utilised to characterise the fundamental instrument response to sky noise and astronomical signals. Novel techniques for analysing onsky performance and atmospheric conditions are presented, along with results from the calibration observations and skydips.

We have successfully fabricated a superconducting transition edge sensor (TES), bolometer that centers on the use of electron-phonon decoupling (EPD) for thermal isolation. We have selected a design approach that separates the two functions of far-infrared and THz radiative power absorption and temperature measurement, allowing separate optimization of the performance of each element. We have integrated molybdenum/gold (Mo/Au) bilayer TES and ion assisted thermally evaporated (IAE) bismuth (Bi) films as radiation absorber coupled to a low-loss microstripline from niobium (Nb) ground plane to a twin-slot antenna structure. The thermal conductance (G) and the time constant for the different geometry device have been measured. For one such device, the measured G is 1.16×10^-10 W/K (± 0.61×10^{- 10} W/K) at 60 mK, which corresponds to noise equivalent power (NEP) = 1.65×10^-18W/ √Hz and time constant of ~5 μs.

We report on the characterization of Si_xN_y (Si-N) optical absorbers and support beams for transition-edge sensors (TESs). The absorbers and support beams measured are suitable to meet ultra-sensitive noise equivalent power (NEP≤10^-19W/√Hz) and effective response time (τ) requirements (τ≤100ms) for space-borne far-infrared( IR)/submillimeter(sub-mm) spectrometers, such as the Background Limited far-Infrared/Sub-mm Spectrograph (BLISS) and the SpicA FAR-infrared Instrument (SAFARI) for the SPace Infrared telescope for Cosmology and Astrophysics (SPICA). The thermal response time (τ₀) of an absorber suspended by support beams from a lowtemperature substrate depends on the heat capacity (C) of the absorber and the thermal conductance (G) of the support beams (τ₀=C/G). In membrane-isolated TESs for BLISS, the effective response time τ is expected to be a factor of 20 smaller than τ0 because of voltage-biased electrothermal feedback operation and assumption of a reasonable open-loop gain, LI≈20. We present design specifications for the arrays of membrane-isolated ultra-sensitive TESs for BLISS. Additionally, we measured G and τ₀ for two Si-N noise thermometry device (NTD) architectures made using different fabrication processes: (1) a solid membrane Si-N absorber suspended by thin and long Si-N support beams and (2) a wire-mesh Si-N absorber suspended by long, and even thinner, Si-N support beams. The measurements of G and τ₀ were designed to test suitability of the Si-N thermal performance to meet the demands of the two SPICA instruments. The solid membrane NTD architecture is similar to the TES architecture for SAFARI and the mesh membrane NTD is similar to that of BLISS TESs. We report measured values of G and C for several BLISS and SAFARI NTD devices. We observe that the heat capacity of the solid membrane devices can be reduced to the order of 1fJ/K at 65mK for devices that are wet etched by KOH. However, C for these devices is found to be on the order of 100fJ/K for a dry XeF₂ process. The heat capacity is similarly large for the mesh devices produced with a dry XeF₂ etch.

The next generation of Cosmic Microwave Background (CMB) experiments probing for signals of inflation and small angular scale polarization anisotropies require higher sensitivity and better control of systematics. We are developing monolithic arrays of orthomode transducer (OMT) coupled transition edge sensor (TES) polarimeters designed for operation at 150 GHz to address these requirements. OMT coupling allows for simultaneous and independent detection of two orthogonal linear polarization states incident on a single pixel. We present measurements of optical efficiencies η_op of single pixels with on-chip band-defining filters, with η_op = 57±4 stat±9 sys %. We also provide evidence for an out-of-band blue leak and address possible sources as well as mitigation techniques. Additionally, we discuss methods for increasing efficiency being implemented in the next generation of pixels, currently in fabrication. Still under development, these pixels are produced as monolithic polarimeter arrays and are slated for use in the Atacama Cosmology Telescope Polarization (ACTpol) and South Pole Telescope Polarization (SPTpol) experiments, while single-pixel polarimeters are to be deployed in the Atacama B-mode Search (ABS) experiment.

ALMA Band 1, covering 31-45 GHz, is the lowest signal frequency band of the ALMA telescope and development of the technology to be used for the front-end cartridge is currently in a research phase. We have made progress on various key components designed for use in the ALMA Band 1 cartridge, including the orthomode transducer (OMT), low-noise amplifier (LNA), lens, and down-converting mixer. Since the layout of the ALMA cartridges within the antenna is not optimized for the lowest band, a dielectric lens is required to avoid blocking other bands. Using a lens necessitates careful characterization of the dielectric properties controlling focal length and dielectric loss. It is also important to match the index of refraction of the lens to minimize reflection while still providing equal performance for both linear polarizations and not introducing any cross-polarization effects. Different anti-reflection techniques will be shown; for example, a hole array, as an anti-reflection layer, has been used for a vacuum window and measured results are compared with simulation. A test cryostat has been constructed by adding an extension to a commercial liquid helium cryostat. Initial sensitivity measurements of a simplified prototype receiver will be given, incorporating an HDPE window, commercial conical feedhorn, 3-stage LNA, and warm amplification stage. An overview of the system losses, receiver noise budget, and system alignment tolerances will also be shown. Furthermore, there is interest in either extending or shifting the existing frequency towards 50 GHz, and the impact on each component will be considered.

We describe the design construction and performance of a L-band (1300-1800 MHz) Ortho Mode Junction for the L-P dual-band receiver to be installed on the 64 m Sardinia Radio Telescope (SRT), a new radio telescope which is being built in Sardinia, Italy. The Ortho Mode Junction (OMJ) separates two orthogonal linearly polarized signals propagating in a 172 mm diameter circular waveguide and couple them into four coaxial outputs. The OMJ is part of an OMT (Ortho Mode Transducer), which includes two 180⁰ hybrids allowing to recombine the out-of-phase signals from the balanced OMJ outputs. The OMJ consists of four probes arranged in symmetrical configuration across the circular waveguide. A shaped tuning stub with cylindrical profile is placed a quarter wavelength away from the probes to guarantee broadband operation with low reflection coefficient across L-band. The four identical probes have a cylindrical structure, each consisting of three concentric cylinders that attach to the central pin of standard 50 Ω 7/16-type coaxial connectors. The OMJ will be cooled at 80 K inside a compact dewar together with directional couplers and Low Noise Amplifiers. The two linearly polarized signals from an input 190 mm diameter room temperature L-band feed couple into the cryogenic dewar through a vacuum window located across the waveguide. Inside the dewar, the 190 mm diameter circular waveguide is tapered down to 172 mm using a conical transition (length 85 mm) filled with a Styrodur® foam that provides mechanical support for a 0.125 mm thick Kapton vacuum barrier. A 0.6 mm air gap across the 172 mm circular waveguide provides thermal decoupling between the ambient temperature and the 80 K OMJ, which is connected to the conical transition output.

The knowledge of THz continuum spectra is essential to investigate the emission mechanisms by high energy particle acceleration processes. Technical challenges appear for obtaining selective spectral sensing in the far infrared range to diagnose radiation produced by solar flare burst emissions measured from space as well as radiation produced by high energy electrons in laboratory accelerators. Efforts are been carried out intended for the development of solar flare high cadence radiometers at two THz frequencies to operate outside the terrestrial atmosphere (i.e. at 3 and 7 THz). One essential requirement is the efficient suppression of radiation in the visible and near infrared. Experimental setups have been assembled for testing (a) THz transmission of "low-pass" filters: rough surface mirrors; membranes Zitex G110G and TydexBlack; (b) a fabricated 2.4 THz resonant grid band-pass filter transmission response for polarization and angle of incidence; (c) radiation response from distinct detectors: adapted commercial microbolometer array using HRFZ-Si window, pyroelectric module and Golay cell; qualitative detection of solar radiation at a sub-THz frequency has been tested with a microbolometer array placed at the focus of the 1.5 m reflector for submillimeter waves (SST) at El Leoncito, Argentina Andes.

We present the design of the passive feed system of the dual-band receiver for the prime focus of the Sardinia Radio Telescope (SRT), a new 64 m diameter radio telescope which is being built in Sardinia, Italy. The feed system operates simultaneously in P-band (305-410 MHz) and L-band (1300-1800 MHz). The room temperature illuminators are arranged in coaxial configuration with an inner circular waveguide for L-band (diameter of 19 cm) and an outer coaxial waveguide for P-band (diameter of 65 cm). Choke flanges are used outside the coaxial section to improve the crosspolarization performance and the back scattering of the P-band feed. The geometry was optimized for compactness and high antenna efficiency in both bands using commercial electromagnetic simulators. Four probes arranged in symmetrical configuration are used in both the P and the L-band feeds to extract dual-linearly polarized signals and to combine them, through phased-matched coaxial cables, into 180 deg hybrid couplers. A vacuum vessel encloses the two P-band hybrids and the two L-band hybrids which are cooled, respectively at 15 K and 77 K. For the P-Band, four low loss coaxial feedthroughs are used to cross the vacuum vessel, while for the L-Band a very low loss large window is employed. The P-band hybrids are based on a microstrip rat-race design with fractal geometry. The L-band hybrids are based on an innovative double-ridged waveguide design that also integrates a band-pass filter for Radio Frequency Interference (RFI) mitigation.

Astronomical dust is observed in a variety of astrophysical environments and plays an important role in radiative processes and chemical evolution in the galaxy. Depending upon the environment, dust can be either carbon-rich or oxygen-rich (silicate grains). Both astronomical observations and ground-based data show that the optical properties of silicates can change dramatically with the crystallinity of the material, and recent laboratory research provides evidence that the optical properties of silicate dust vary as a function of temperature as well. Therefore, correct interpretation of a vast array of astronomical data relies on the understanding of the properties of silicate dust as functions of wavelength, temperature, and crystallinity. The OPASI-T (Optical Properties of Astronomical Silicates with Infrared Techniques) project addresses the need for high quality optical characterization of metal-enriched silicate condensates using a variety of techniques. A combination of both new and established experiments are used to measure the extinction, reflection, and emission properties of amorphous silicates across the infrared (near infrared to millimeter wavelengths), providing a comprehensive data set characterizing the optical parameters of dust samples. We present room temperature measurements and the experimental apparatus to be used to investigate and characterize additional metal-silicate materials.

We present a smooth-walled feedhorn with cross polarization and reflected power lower than -30 dB across the entire 30% bandwidth. A prototype feedhorn has been fabricated, and the wide-band, low-cross polarization performance has been demonstrated. The feedhorn has a circular aperture and monotonically narrows towards an input waveguide interface. This allows it to be manufactured by progressively milling the profile using a set of custom tools. This is especially useful in applications where a large number of feeds are desired in a planar array format. Such applications include astronomical cameras in millimeter waveband that require large arrays of detectors for future increases in mapping speed and sensitivity. Specifically, large arrays of feedhorns are well-matched to the problem of measuring the polarization of the cosmic microwave background to search for the faint signature of inflation, as they provide good beam control, the requisite sensitivity, and compatibility with low-noise bolometric detectors.

Spider is a balloon-borne array of six telescopes that will observe the Cosmic Microwave Background. The 2624 antenna-coupled bolometers in the instrument will make a polarization map of the CMB with approximately one-half degree resolution at 145 GHz. Polarization modulation is achieved via a cryogenic sapphire half-wave plate (HWP) skyward of the primary optic. We have measured millimeter-wave transmission spectra of the sapphire at room and cryogenic temperatures. The spectra are consistent with our physical optics model, and the data gives excellent measurements of the indices of A-cut sapphire. We have also taken preliminary spectra of the integrated HWP, optical system, and detectors in the prototype Spider receiver. We calculate the variation in response of the HWP between observing the CMB and foreground spectra, and estimate that it should not limit the Spider constraints on inflation.

We have designed, fabricated, and tested compact radiative control structures, including antireflection coatings and resonant absorbers, for millimeter through submillimeter wave astronomy. The antireflection coatings consist of micromachined single crystal silicon dielectric sub-wavelength honeycombs. The effective dielectric constant of the structures is set by the honeycomb cell geometry. The resonant absorbers consist of pieces of solid single crystal silicon substrate and thin phosphorus implanted regions whose sheet resistance is tailored to maximize absorption by the structure. We present an implantation model that can be used to predict the ion energy and dose required for obtaining a target implant layer sheet resistance. A neutral density filter, a hybrid of a silicon dielectric honeycomb with an implanted region, has also been fabricated with this basic approach. These radiative control structures are scalable and compatible for use large focal plane detector arrays.

We describe the design, construction, and performance of a waveguide Orthomode Transducer (OMT) for the 385-500 GHz band. The OMT is based on a symmetric backward coupling structure with a square waveguide input (0.56x0.56 mm²) and two single-mode waveguide outputs: a standard WR2.2 waveguide (0.56x0.28 mm²) and an oval waveguide with full-radius corners. The OMT is rescaled from a lower frequency design that was developed for the 3 mm band; it was optimized using a commercial 3D electromagnetic simulator. The OMT consists of two mechanical blocks in split-block configuration, fabricated using a CNC micromilling machine. A first prototype copper alloy OMT employing standard UG387 flanges at all ports was fabricated and tested. From 385 to 500 GHz the measured input reflection coefficient was less than -10 dB, the isolation between the outputs was less than -25 dB, the cross polarization was less than -10 dB, and the transmission was ≈-2 dB at room temperature for both polarization channels. The effects of misalignment errors in the OMT performance were studied using electromagnetic simulation. A second OMT version utilizing custom made mini-flanges and much shorter waveguides was designed and will be tested soon. This novel OMT is more tolerant to misalignment errors of the block halves and is expected to have much improved performance over the first prototype.

The SCUBA-2 imaging Fourier Transform Spectrometer (FTS-2) is a dual-band Mach-Zehnder imaging spectrometer, built for use with the SCUBA-2 camera on the James Clerk Maxwell Telescope (JCMT). FTS-2 will provide resolving powers of R ~ 10 to 5000 across the 450 and 850 μm bands, with a FOV up to 5 arcmin². The instrument has been built and tested, with first light on the telescope planned for fall 2010. We present the alignment process, laboratory test results, and discuss the first science targets in the context of other similar space and ground-based instruments.

We describe the design, construction and performance of a novel 180° hybrid power divider for L-band (1.3-1.8 GHz). The hybrid is based on a double ridged waveguide cavity that also integrates a band pass filter. The device will operate at 77 K inside a cryogenically cooled receiver to be installed at the primary focus of the Sardinia Radio Telescope. The hybrid has three ports consisting of N-type coaxial connectors whose central pins are attached to launching probes located inside the double ridge waveguide structure. The signal is launched into the cavity from an input probe located on one cavity end and is extracted from two output probes on the opposite end. The output probes are arranged in balanced configuration, are axially symmetric, and aligned along the same axis. Both input and output probes are located in front of reactive loads consisting of shaped tunerless backshorts that provide broad band responses with low reflection coefficient. The band pass filter is located in the middle of the cavity, between the two input and output transitions. The dimensions of the device (excluding connectors) are 70 x 57.2 x 254.4 mm³. The design was optimized using a commercial electromagnetic simulator. From 1.3-1.8 GHz the measured output reflection coefficient was less than -17dB , the coupling and the phase difference between inputs and output was respectively, 3±0.25dB and 180⁰±0.9⁰, over the full band. The amplitude and phase balance performances are much superior to that of commercially available devices.

At Universidad de Chile we have started a program for the development of a prototype receiver for Band 1 (31-45 GHz) of the Atacama Large Millimeter Array. This receiver will use a low-noise amplifier which is specified to have 5 times the quantum limit (~10 K). Here we present the first efforts and results towards reaching that goal.

The Q/U Imaging Experiment (QUIET) is an experimental program to make very sensitive measurements of the Cosmic Background Radiation (CMB) polarization from the ground. A key component of this project is the ability to produce large numbers of detectors in order to achieve the required sensitivity. Using a breakthrough in mm-wave packaging at JPL, a polarimeter-on-a-chip has been developed which lends itself to the mass-production techniques used in the semiconductor industry. We describe the design, implementation and performance of these polarimeter modules for QUIET Phase I and briefly discuss the plans for further module development.

We report on the development of some of the key technologies that will be needed for a large-format Cosmic Microwave Background (CMB) interferometer with many hundreds of wideband W-band (75-110 GHz) receivers. A scalable threebaseline prototype interferometer is being assembled as a technology demonstration for a future ground- or space-based instrument. Each of the prototype heterodyne receivers integrates two InPMonolithic Microwave Integrated Circuit (MMIC) low-noise amplifiers, a coupled-line bandpass filter, a subharmonic balanced diode mixer, and a 90° local oscillator phase switch into a single compact module that is suitable for mass production. Room temperature measurements indicate bandaveraged receiver noise temperatures of 500 K from 85-100 GHz. Cryogenic receiver noise temperatures are expected to be around 50 K.

A prototype heterodyne amplifier module has been designed for operation from 140 to 170 GHz using Monolithic Millimeter- Wave Integrated Circuit (MMIC) low noise InP High Electron Mobility Transistor (HEMT) amplifiers. In the last few decades, astronomical instruments have made state-of-the-art measurements operating over the frequency range of 5-100 GHz, using HEMT amplifiers that offer low noise, low power dissipation, high reliability, and inherently wide bandwidths. Recent advances in low-noise MMIC amplifiers, coupled with industry-driven advances in high frequency signal interconnects and in the miniaturization and integration of many standard components, have improved the frequency range and scalability of receiver modules that are sensitive to a wide (20-25%) simultaneous bandwidth. HEMT-based receiver arrays with excellent noise and scalability are already starting to be manufactured around 100 GHz, but the advances in technology should make it possible to develop receiver modules with even higher operation frequency - up to 200 GHz. This paper discusses the design of a compact, scalable module centered on the 150 GHz atmospheric window using components known to operate well at these frequencies. Arrays equipped with hundreds of these modules can be optimized for many different astrophysical measurement techniques, including spectroscopy and interferometry.

We describe the design and characterisation of a cryogenic millimetre/sub-millimetre wave calibration load, cooled by use of a closed cycle refrigerator that is used to test the performance of the ALMA receiver front-end system. Use of the refrigerator removes the need for liquid cryogen (nitrogen) cooling and allows for long duration, and unattended operation independent of orientation angle. Key requirements of the load include provision of a well-characterised and constant brightness temperature over a wide frequency range (from ~100 GHz to ~1 THz) polarisation insensitivity, high emissivity and mechanical stability. Test and verification of the load performance characteristics is achieved by using several measurement techniques; these are presented and compared with measurements made using a liquid cryogen load (cooled reference).

More efficient continuous-wave photonic nearinfrared mixers as terahertz sources are investigated with the motivation to develop a universal photonic local oscillator for astronomical submillimeter/terahertz receiver systems. For this, we develop new concepts for vertically illuminated traveling-wave (TW) photomixers, TW Uni-Travelling Carrier (UTC) photodiodes. Device simulation/modeling and optical/terahertz testing is being done in the new terahertz photonics laboratory at the Electrical Engineering Department of the University of Chile, whereas device fabrication is performed at the MC2 cleanroom facility at Chalmers Technical University. We report on first progress in this direction.

Beam characterization is of critical importance when analyzing and interpreting data from Cosmic Microwave Background (CMB) experiments. In this paper we present scanning strategies, data analysis methods and results of the 44 GHz (Q-Band) beam characterization for the Q/U Imaging ExperimenT (QUIET) Phase- I, using the Crab nebula (Tau A) and Jupiter as polarized and unpolarized point sources, respectively. The beams are modeled as a sum of gaussian terms multiplied by orthogonal polynomials after symmetrization using observations taken at different rotation angles about the optical axis. The l-space window function calculation procedure is explained and applied, along with the corresponding propagation of parameter uncertainty. These window functions encode the effect of the finite resolution of the instrument on its ability to measure the angular power spectrum, as a function of multipole . Additionally, the instrumental polarization is characterized in terms of two-dimensional Mueller fields which describe the coupling of the Stokes parameters. The data presented in this work were collected during the first season of QUIET observations that started in October 2008.

The Q/U Imaging ExperimenT (QUIET), a ground-based experiment located in the Atacama Desert in Chile, measures the polarization of the Cosmic Microwave Background (CMB). In Phase I, it measures the CMB polarization at angular scales of 25 (see manuscript) l (see manuscript) 1000 using radiometer arrays in the Q (44 GHz) and W (95 GHz) frequency bands. The Q-band and W-band receivers of Phase I of the QUIET instrument contain 2 and 6 total power modules (TT modules), and 17 and 84 polarization modules respectively. Responsivities for the TT modules are obtained primarily from Jupiter and skydip measurements, using Jupiter as the absolute calibrator and the more frequent skydip measurements to track short time-scale fluctuations over the course of the season. Responsivities for the polarization modules are obtained from Tau A, relative measurements from the Moon, a polarizing wire-grid, and skydips. Skydips are used to track the responsivity of the polarization modules on a shorter time-scale.

We present a method of cross-calibrating the polarization angle of a polarimeter using Bicep Galactic observations. Bicep was a ground based experiment using an array of 49 pairs of polarization sensitive bolometers observing from the geographic South Pole at 100 and 150 GHz. The Bicep polarimeter is calibrated to ±0.01 in cross-polarization and less than ±0.7° in absolute polarization orientation. Bicep observed the temperature and polarization of the Galactic plane (R.A = 100° ~ 270° and Dec. = -67° ~ -48°). We show that the statistical error in the 100 GHz Bicep Galaxy map can constrain the polarization angle offset of Wmap W band to 0.6° ± 1.4°. The expected 1σ errors on the polarization angle cross-calibration for Planck or EPIC are 1.3° and 0.3° at 100 and 150 GHz, respectively. We also discuss the expected improvement of the Bicep Galactic field observations with forthcoming Bicep2 and Keck observations.

The very challenging SPICA/SAFARI scientific goals imply to cool most detector solutions below 100 mK. This implies to find reliable solutions providing not only very efficient thermal insulation between the different temperature stages, but also keeping the stray light level well below the foreseen astronomical background (20 aW/pixel !). The main constraint is the available power budget (1-2μW); this value includes optical, electrical and parasitic power loads. This poster describes how the Herschel/PACS Bolometer Focal Plane thermo-mechanical design can be adapted to the new thermal and optical needs, while keeping a sufficiently stiff structure to withstand launch vibrations. We give the first results on the thermal and mechanical behaviour obtained with a prototype.

NTU-Array is a W-band, dual-polarization, 6-receiver interferometer telescope aiming to detect the cross-over of CMB primary and secondary anisotropies. The telescope has 34Ghz instantaneous bandwidth for the continuum observation. The ultra-wide bandwidth is down-converted to four base-bands of 0-8.7Ghz for the ensuing digital correlation. We have completed the development of an FX digital correlator system for NTU-Array, which utilizes 18Ghz, 1-bit samplers for digitization and Virtex-4 FPGAs for subsequent digital processing of Fourier transformation and cross-correlation. This new digital correlator has 275Mhz frequency resolution and is processing in real time the 850 Gbps input data at power consumption about 1 KW. We stress that our present setup substantially under-rates this FPGA computing machine, as it is designed to process 2.5 Tbps input data in real time from 18Ghz, 3-bit ADCs. Verification of this new digital correloator has been completed, and it demonstrates that the correlator can detect small signals with -40db S/N within one second integration per frequency channel.

Frequency multiplexed readout systems for large TES bolometer arrays are in use for ground and balloonbased mm-wavelength telescopes. New digital backend electronics for these systems implement advanced signal processing algorithms on FPGAs. Future satellite instruments will likely use similar technology. We address the challenges of operating FPGAs in an orbital radiation environment using neighbour-neighbour monitoring, where each FPGA monitors its neighbour and can correct errors due to radiation events. This approach reduces the FPGA's susceptibility to crippling events without relying on triple redundancy or radiation-hardened parts, which raise the system cost, power budget, and complexity. This approach also permits earlier adoption of the latest FPGAs, since radiation-hardened variants typically lag the state of the art.

We discuss on the development of a 32-ch cryogenic readout module for a superconductive imaging submillimeter-wave camera (SISCAM). The module is composed of GaAs-JFET integrated circuits such as capacitive trans-impedance amplifiers (CTIAs), multiplexer with sample-and-holds and shift-registers. Performances of these integrated circuits are evaluated; 1) amplifier gain of 5000 and gain-bandwidth more than 500 kHz, 2) operation of 32-ch multiplexers addressed by shift-registers, and 3) operation of voltage distributors. Using these GaAs-JFET cryo-ASICs, a 32-ch cryogenic readout module was fabricated for an imaging array of SIS photon detectors at 650 GHz.