The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) is a sub-orbital experiment designed to study the process of star formation in local galaxies (including the Milky Way) and in galaxies at cosmological distances. Using a 2m Cassegrain telescope, BLAST images the sky onto a focal plane, which consists of 270 bolometric detectors split between three arrays, observing simultaneously in 30% wide bands, centered at 250, 350, and 500 μm. The diffraction-limited optical system provides a resolution of 30" at 250 μm. The pointing system enables raster-like scans with a positional accuracy of ~30", reconstructed to better than 5" rms in postflight analysis. BLAST had two successful flights, from the Arctic in 2005, and from Antarctica in 2006, which provided the first high-resolution and large-area (~0.8−200 deg²) submillimeter surveys at these wavelengths. As a pathfinder for the SPIRE instrument on Herschel, BLAST shares with the ESA satellite similar focal plane technology and scientific motivation. A third flight in 2009 will see the instrument modified to be polarization-sensitive (BLAST-pol). With its unprecedented mapping speed and resolution, BLAST-pol will provide insights into Galactic star-forming nurseries, and give the necessary link between the larger, coarse resolution surveys and the narrow, resolved observations of star-forming structures from space and ground based instruments being commissioned in the next 5 years.

A new facility instrument, the Large APEX Bolometer Camera (LABOCA), developed by the Max-Planck-Institut f&diaeru;r Radioastronomie (MPIfR, Bonn, Germany), has been commissioned in May 2007 for operation on the Atacama Pathfinder Experiment telescope (APEX), a 12 m submillimeter radio telescope located at 5100 m altitude on Llano de Chajnantor in northern Chile. For mapping, this 295-bolometer camera for the 870 micron atmospheric window operates in total power mode without wobbling the secondary mirror. One LABOCA beam is 19 arcsec FWHM and the field of view of the complete array covers 100 square arcmin. Combined with the high efficiency of APEX and the excellent atmospheric transmission at the site, LABOCA offers unprecedented capability in large scale mapping of submillimeter continuum emission. Details of design and operation are presented.

We have developed key technologies to enable highly versatile, kilopixel bolometer arrays for infrared through millimeter wavelengths. Our latest array architecture is based on our Backshort Under Grid (BUG) design, which is specifically targeted at producing kilopixel-size arrays for future ground-based, suborbital and space-based X-ray and far-infrared through millimeter cameras and spectroometers. In November of 2007, we demonstrated a monolithic 8x16 BUG bolometer array with 2 mm-pitch detectors for astronomical observations using our 2 mm wavelength camera GISMO (the Goddard IRAM Superconducting 2 Millimeter Observer) at the IRAM 30 m telescope in Spain. The 2 mm spectral range provides a unique terrestrial window enabling ground-based observations of the earliest active dusty galaxies in the universe and thereby allowing a better constraint on the star formation rate in these objects. We present preliminary results from our observing run with the first fielded BUG bolometer array and discuss the performance of the instrument.

MUSTANG is a 90 GHz bolometer camera built for use as a facility instrument on the 100 m Robert C. Byrd Green Bank radio telescope (GBT). MUSTANG has an 8 by 8 focal plane array of transition edge sensor bolometers read out using time-domain multiplexed SQUID electronics. As a continuum instrument on a large single dish MUSTANG has a combination of high resolution (8) and good sensitivity to extended emission which make it very competitive for a wide range of galactic and extragalactic science. Commissioning finished in January 2008 and some of the first science data have been collected.

Large-format (sub)millimeter wavelength imaging arrays are best operated in scanning observing modes rather than traditional position-switched (chopped) modes. The choice of observing mode is critical for isolating source signals from various types of noise interference, especially for ground-based instrumentation operating under a bright atmosphere. Ideal observing strategies can combat 1/f noise, resist instrumental defects, sensitively recover emission on large scales, and provide an even field coverage - all under feasible requirements of telescope movement. This work aims to guide the design of observing patterns that maximize scientific returns. It also compares some of the popular choices of observing modes for (sub)millimeter imaging, such as random, Lissajous, billiard, spiral, On-The-Fly (OTF), DREAM, chopped and stare patterns. Many of the conclusions are also applicable other imaging applications and imaging in one dimension (e.g. spectroscopic observations).

The Millimeter Bolometer Array Camera (MBAC) was commissioned in the fall of 2007 on the new 6-meter Atacama Cosmology Telescope (ACT). The MBAC on the ACT will map the temperature anisotropies of the Cosmic Microwave Background (CMB) with arc-minute resolution. For this first observing season, the MBAC contained a diffraction-limited, 32 by 32 element, focal plane array of Transition Edge Sensor (TES) bolometers for observations at 145 GHz. This array was coupled to the telescope with a series of cold, refractive, reimaging optics. To meet the performance specifications, the MBAC employs four stages of cooling using closed-cycle ³He/⁴He sorption fridge systems in combination with pulse tube coolers. In this paper we present the design of the instrument and discuss its performance during the first observing season. Finally, we report on the status of the MBAC for the 2008 observing season, when the instrument will be upgraded to a total of three separate 1024-element arrays at 145 GHz, 220 GHz and 280 GHz.

We present the design and the present development status of a 204 pixels mm-wave bolometric camera compatible with the 30 meter IRAM telescope at Pico Veleta. Sequential and non-sequential ray-tracing and physical optics simulations have been performed with ZEMAX, taking into account the IRAM mirrors and the telecentric camera. The focal plane is made by an array of antenna-coupled NbSi microbolometers, described in brief. We present the cryostat design, and then more in details the optics and the baffling system. We conclude with a brief discussion on the future perspectives toward the multi-thousands pixels bolometric mm-wave camera at IRAM.

ArTeMiS is a camera designed to operate on large ground based submillimetric telescopes in the 3 atmospheric windows 200, 350 and 450 µm. The focal plane of this camera will be equipped with 5760 bolometric pixels cooled down at 300 mK with an autonomous cryogenic system. The pixels have been manufactured, based on the same technology processes as used for the Herschel-PACS space photometer. We review in this paper the present status and the future plans of this project. A prototype camera, named P-ArTeMiS, has been developed and successfully tested on the KOSMA telescope in 2006 at Gornergrat 3100m, Switzerland. Preliminary results were presented at the previous SPIE conference in Orlando (Talvard et al, 2006). Since then, the prototype camera has been proposed and successfully installed on APEX, a 12 m antenna operated by the Max Planck Institute für Radioastronomie, the European Southern Observatory and the Onsala Space Observatory on the Chajnantor site at 5100 m altitude in Chile. Two runs have been achieved in 2007, first in March and the latter in November. We present in the second part of this paper the first processed images obtained on star forming regions and on circumstellar and debris disks. Calculated sensitivities are compared with expectations. These illustrate the improvements achieved on P-ArTeMiS during the 3 experimental campaigns.

The MKID Camera is a millimeter/submillimeter instrument being built for astronomical observations from the Caltech Submillimeter Observatory. It utilizes microwave kinetic inductance detectors, which are rapidly achieving near-BLIP sensitivity for ground-based observations, and a software-defined radio readout technique for elegant multiplexing of a large number of detectors. The Camera will have 592 pixels distributed over 16 tiles in the focal plane, with four colors per pixel matched to the 750 μm, 850 μm, and 1.0 - 1.5 mm (split in two) atmospheric transmission windows. As a precursor to building the full-up camera and to enable ongoing detector testing, we have built a DemoCam comprised of a 16-pixel MKID array with which we have made preliminary astronomical observations. These observations demonstrate the viability of MKIDs for submillimeter astronomy, provide insight into systematic design issues that must be considered for MKID-based instruments, and they are the first astronomical observations with antenna-coupled superconducting detectors. In this paper, we describe the basic systems and specifications of the MKID Camera, we describe our DemoCam observations, and we comment on the status of submillimeter MKID sensitivities.

Development of large format, far infrared focal-plane arrays has been identified as a pressing need for future astronomical instruments. In particular, array sizes as large as 128x128 with sensitivities equal to or better than 10^-18 W/√Hz are the goals to be achieved within the next fifteen years. As part of our continuing effort to further this technology, we are developing a 32x32 Ge:Sb photoconductor FPA with a CTIA cryogenic readout multiplexer. A new, layered-hybrid architecture is employed to block the readout glow, improve heat dissipation and temperature uniformity across the array, and alleviate the potential problems associated with the large CTE mismatch between the Ge detector and the Si readout. This is the first 1k-pixel photoconductor FPA of its kind and is meant to be a pathfinder for future large format FPAs. Based on the test results of a prototype 2x16 Ge:Sb array of similar design, we expect the sensitivity of this FPA to be as low as 10^-18 W/√Hz. This paper presents the design, characteristics, and the expected performance of this array.

We are presenting the current progress on the titanium (Ti) hot-electron transition-edge devices. The ultimate goal of this work is to develop a submillimeter Hot-Electron Direct Detector (HEDD) with the noise equivalent power NEP = 10^-18-10^-20 W/Hz^1/2 for the moderate resolution spectroscopy and Cosmic Microwave Background (CMB) studies on future space telescope (e.g., SPICA, SAFIR, SPECS, CMBPol) with cryogenically cooled (~ 4-5 K) mirrors. Recentlyⁱ, we have achieved the extremely low thermal conductance (~ 20 fW/K at 300 mK and ~ 0.1 fW/K at 40 mK) due to the electron-phonon decoupling in Ti nanodevices with niobium (Nb) Andreev contacts. This thermal conductance translates into the "phonon-noise" NEP ≈ 3×10^-21 W/Hz^1/2 at 40 mK and NEP ≈ 3×10^-19 W/Hz^1/2 at 300 mK. These record data indicate the great potential of the hot-electron detector for meeting many application needs. Beside the extremely low phonon-noise NEP, the nanobolometers have a very low electron heat capacitance that makes them promising as detectors of single THz photonsⁱⁱ. As the next step towards the practical demonstration of the HEDD, we fabricated and tested somewhat larger than in Ref.1 devices (~ 6 μm × 0.35 μm × 40 nm) whose critical temperature is well reproduced in the range 300-350 mK. The output electrical noise measured in these devices with a low-noise dc SQUID is dominated by the thermal energy fluctuations (ETF) aka "phonon noise". This indicates the high electrothermal loop gain that effectively suppresses the contributions of the Johnson noise and the amplifier (SQUID) noise. The electrical NEP = 6.7×10^-18 W/Hz^1/2 derived from these measurements is in good agreement with the predictions based on the thermal conductance data. The very low NEP and the high speed (~ μs) are a unique combination not found in other detectors.

Bolometers are very simple devices. In principle, the behaviour of a bolometer can be described by a simple model along with a small number of parameters. The SPIRE instrument for the Herschel Space Observatory contains five arrays of NTD germanium spiderweb bolometers containing up to 139 pixels. We show from characterisation measurements on the ground using the flight read-out system that the bolometers follow the ideal model extremely well, are very stable, and that the read-out system is sufficiently well behaved to take advantage of this. Calibration should be greatly simplified by being able to take advantage of this behaviour.

Bolometers cooled to very low temperature are currently the most sensitive detectors for low spectral resolution detection of millimetre and sub-millimetre wavelengths. The best performances of the state-of-the-art bolometers allow to reach sensitivities below the photon noise of the Cosmic Microwave Background for example. Since 2003, a french R&D effort called DCMB ("Developpement Concerte de Matrices de Bolometres") has been organised between different laboratories to develop large bolometers arrays for astrophysics observations. Funded by CNES and CNRS, it is intended to get a coherent set of competences and equipments to develop very cold bolometers arrays by microfabrication. Two parallel developments have been made in this collaboration based on the NbSi alloy either semi-conductive or superconducting depending on the proportion of Nb. Multiplexing schemes have been developed and demonstrated for these two options. I will present the latest developments made in the DCMB collaboration and future prospects.

We present the experimental results and a bolometer model of the voltage-biased superconducting bolometer on the low stress silicon nitride (Si₃N₄) membrane, developed in collaboration between the Max-Planck-Institut fur Radioastronomie (MPIfR), Bonn and the Institute for Photonic Technology (IPHT), Jena, Germany. The superconducting thermistor, deposited on the low stress silicon nitride membrane, is a bilayer of gold-palladium and molybdenum and is designed for a transition temperature of 450 mK. Bolometers for the 1.2 mm atmospheric window were designed, built and tested. The thermal conductance of the bolometer is tuned by structuring the silicon nitride membrane into spider-like geometries. The incident radiation is absorbed by crossed dipoles made from gold-palladium alloy with a surface resistance of 10 Ω/square. Using the COSMOS finite element analysis package, the thermal conductance is obtained for the bolometers of different geometries. FEA simulations showed that the deposition of a gold ring around the absorbing area could increase the sensitivity of the bolometer. Therefore, a gold ring is deposited around the center absorbing patch of the silicon nitride membrane. For the bolometer with a gold ring, the measured NEP is 1.7 X (see manuscript for formula) Hz and the time constant is in the range between 1.4 and 2 ms.

We present measurements of the electrical and thermal properties of new arrays of bolometeric detectors that were fabricated as part of a program to develop bolometers optimized for the low photon background of the EBEX balloon-borne experiment. An array consists of 140 spider-web transition edge sensor bolometers microfabricated on a 4" diameter silicon wafer. The designed average thermal conductance (see manuscript) of bolometers on a proto-type array is 32 pW/K, and measurements are in good agreement with this value. The measurements are taken with newly developed, digital frequency domain multiplexer SQUID readout electronics.

Current and future astronomical detectors based on Transition Edge Sensors (TESs) need to achieve theoretically predicted current noise performance determined by the sum of contributions from thermal noise in the link to the heat bath, Johnson noise in the sensor itself and noise in the electrical readout circuit. Present TES geometries can have noise levels significantly above this limit. Our Mo/Cu bilayer TESs are fabricated on long, narrow, thermally isolating silicon nitride structures and are designed for operation at 360 or 200 mK. We briefly review the likely sources of the additional noise sources in this geometry and show results of measurements and modelling of the noise sources as the TES geometry is modified for TESs operated at both temperatures.

Transition-Edge Sensors (TESs) are sensitive devices used in astronomical detectors. Recent projects in ground-based and space astronomy demand the Noise Equivalent Power (NEP) of the TES to be reduced to the limits needed for accurate measurements, for example, of the B-mode polarisation of the CMB. Thus, we have measured thermal conductance of Si_xN_y bridges of various geometries, and present the results that give insight into the phonon transport mechanism inside these low-dimensional structures. We also present a new method for measuring the NEP of TESs using an on-chip black body radiator.

We have fabricated TES bolometers with finline transitions for the CℓOVER project. We have measured the optical response of CℓOVER's first prototype 97-GHz detectors and find that they have a detection efficiency close to 100%. We have also investigated the effects of misalignment of the finline in the waveguide and of thinning the substrate. The prototype detectors have dark NEPs as low as 1.5 x 10^-17W/√Hz and satisfy the requirement of photon-noise limited operation on CℓOVER. We describe the optical tests of CℓOVER's prototype 97-GHz detectors and discuss their implications for the design of the science-grade detectors.

We describe the optimization of transition edge superconducting (TES) detectors for use in a far-infrared (FIR) Fourier transform spectrometer (FTS) mounted on a cryogenically cooled space-borne telescope (e.g. SPICA). The required noise equivalent power (NEP) of the detectors is approximately 10^-19W/√Hz in order to be lower than the photon noise from astrophysical sources in octave wide bands in the FIR. The detector time constants must be less than 10 ms in order to allow fast scanning of the FTS mechanism. The detectors consist of superconducting thermometers suspended on thin legs of thermally isolating silicon nitride and operate at a temperature of approximately 100 mK. We present the design of the detectors, a proposed focal plane layout and optical coupling scheme and measurements of thermal conductance and time constant for low NEP prototype TES bolometers.

The Atacama Cosmology Telescope (ACT) aims to measure the Cosmic Microwave Background (CMB) temperature anisotropies on arcminute scales. The primary receiver for ACT is the Millimeter Bolometer Array Camera (MBAC). The MBAC is comprised of three 32×32 transition edge sensor (TES) bolometer arrays, each observing the sky with an independent set of band-defining filters. The MBAC arrays will be the largest pop-up detector arrays fielded, and among the largest TES arrays built. Prior to its assembly into an array and installation into the MBAC, a column of 32 bolometers is tested at ~ 0.4 K in a quick-turn-around dip probe. In this paper we describe the properties of the ACT bolometers as revealed by data from those tests, emphasizing a characterization that accounts for both the complex impedance and the noise as a function of frequency.

We describe a new type of FIR detector based on lumped element superconducting resonators (LEKIDs). These devices can act as distributed FIR radiation absorbers without the need for an additional coupling structure. In addition, these devices can be integrated into a compact filled array geometry with high filling factor. We describe the optimization of lumped element resonators for high coupling efficiency to incoming radiation in the wavelength region from 200μm - 450μm, measurements of electrical and optical properties of these devices and the design of a prototype array using these detectors.

The modeling of millimeter and sub-millimeter-wave optical systems requires special approaches. In many systems the beams can be considered to be coherent and their propagation can be efficiently modeled using modal analysis, especially useful for quick design purposes. Physical optics is also a useful tool when detailed analysis is required. Modal analysis in general, however, is a very powerful technique, which enables one also to understand issues associated with throughput when partially coherent systems and arrays are being considered. In the paper we discuss these issues and present some examples from millimeter and submillimeter wave astronomical instrumentation.

SCUBA-2 is a new wide-field submillimeter continuum instrument being commissioned on the James Clerk Maxwell Telescope on Mauna Kea in Hawaii. SCUBA-2 images simultaneously at 450 and 850 μm using large-scale arrays of superconducting bolometers, with over five thousand pixels at each wavelength. The arrays are cooled to less than 100 mK by the mixing chamber of a dilution refrigerator (DR), with a radiation shield at a nominal temperature of 1 K cooled by the DR still. The DR is a "dry" system, using a pulse tube cooler for precooling of the circulating helium in place of a liquid helium bath. This paper presents key performance data for the DR.

This paper describes the key design features and performance of HARP, an innovative heterodyne focal-plane array receiver designed and built to operate in the submillimetre on the James Clerk Maxwell Telescope (JCMT) in Hawaii. The 4x4 element array uses SIS detectors, and is the first sub-millimetre spectral imaging system on the JCMT. HARP provides 3-dimensional imaging capability with high sensitivity at 325-375 GHz and affords significantly improved productivity in terms of speed of mapping. HARP was designed and built as a collaborative project between the Cavendish Astrophysics Group in Cambridge UK, the UK-Astronomy Technology Centre in Edinburgh UK, the Herzberg Institute of Astrophysics in Canada and the Joint Astronomy Centre in Hawaii. SIS devices for the mixers were fabricated to a Cavendish Astrophysics Group design at the Delft University of Technology in the Netherlands. Working in conjunction with the new Auto Correlation Spectral Imaging System (ACSIS), first light with HARP was achieved in December 2005. HARP synthesizes a number of interesting features across all elements of the design; we present key performance characteristics and images of astronomical observations obtained during commissioning.

We report on developments of submillimeter heterodyne arrays for high resolution spectroscopy with APEX. Shortly, we will operate state-of-the-art instruments in all major atmospheric windows accessible from Llano de Chajnantor. CHAMP+, a dual-color 2×7 element heterodyne array for operation in the 450 μm and 350 μm atmospheric windows is in operation since late 2007. With its state-of-the-art SIS detectors and wide tunable local oscillators, its cold optics with single sideband filters and with 3 GHz of processed IF bandwidth per pixel, CHAMP+ does provide outstanding observing capabilities. The Large APEX sub-Millimeter Array (LAsMA) is in the final design phase, with an installation goal in 2009. The receiver will operate 7 and 19 pixels in the lower submillimeter windows, 285-375 GHz and 385-520 GHz, respectively. The front-ends are served by an array of digital wideband Fast Fourier Transform spectrometers currently processing up to 32×1.5 (optionally 1.8) GHz of bandwidth. For CHAMP+, we process 2.8 GHz of instantaneous bandwidth (in 16.4 k channels) for each of the 14 pixels.

We report on the development of 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.

CASIMIR, the Caltech Airborne Submillimeter Interstellar Medium Investigations Receiver is a multiband, far infrared and submillimeter, high resolution, heterodyne spectrometer under development for SOFIA. It is a first generation, PI class instrument. CASIMIR is designed for detailed, high sensitivity observations of warm (100 K) interstellar gas both in external galaxies and Galactic sources, including molecular clouds, circumstellar envelopes, and protostellar cores. Combining the 2.5 m SOFIA mirror with state of the art superconducting mixers, will give CASIMIR unprecedented sensitivity. Initially, CASIMIR will have two bands, at 1000 and 1250 GHz, and a further three bands, 550, 750, 1400 GHz, will be added soon after. Any four bands will be available on each flight. The availability of multiple bands during each flight will allow for efficient use of flight time. For example, searches for weak lines from rare species in bright sources can be carried out on the same flight with observations of abundant species in faint or distant objects.

Many of the most astrophysically important transitions of atoms and molecules occur at THz frequencies. These transitions allow us to probe the formation and evolution of stars, planets, galaxies, and even the Universe itself. A recent confluence of technologies involving mixers, local oscillators, micromachining, IF amplifiers, and digital signal processing now make the fabrication of large format (~1000 pixel), heterodyne arrays at THz frequencies possible. Planned observatories at high altitude sites (e.g. the high Atacama and Dome A in Antarctica) and in the stratosphere (e.g. SOFIA and balloon-borne telescopes) can serve as platforms from which THz arrays can provide unprecedented access to a powerful window to the Universe. In this paper the scientific impact and technical roadmap to the realization and implementation of THz arrays will be discussed.

Developments on large format array of superconducting tunnel junction detectors are discussed and recent activities in readout electronics developments and focal plane optics designs are presented. We have been working on submillimeter-wave SIS photon detectors at 650 GHz using niobium tunnel junctions, which have high sensitivity, large dynamic range and fast response. Here we discuss on an implementation plan of large format array with cryogenic readout electronics and compact focal plane optics design. GaAs-JFETs operate at less than 1 K with low noise, low power dissipation and fast response. We have demonstrated operation of cryogenic integrating amplifiers and digital electronics for SIS photon detectors with multiplexed readout. Combined with compact focal plane optics, we now have a conceptual design of large format array of SIS photon detectors in submillimeter-wave. Further development to realize higher sensitivity superconducting tunnel junction detectors with extremely low leakage current are foreseen.

We present a trade study for a submillimeter direct-detection spectrometer operating at the background limit for the Cornell Caltech Atacama Telescope (CCAT). In this study we compare the classical echelle spectrometer ZEUS with the waveguide grating spectrometer Z-Spec. The science driver for this instrument is spectroscopic investigation of high redshift galaxies as their far-IR fine structure line emission is redshifted into the telluric submillimeter windows. The baseline detector consists of SQUID multiplexed TES bolometers and the ideal spectrometer to detect weak lines from distant extragalactic sources is a grating with a resolution of ~103 and a large bandwidth, covering an entire telluric submillimeter window instantaneously. Since the density of high-z sources on the sky is ~100 within a 10'×10' field of view and a redshift range of Δz~0.2 we also explore multi-object (~50 objects) capability, including articulated mirrors and flexible waveguide fibers.

A novel concept of the parallel/series array of Superconducting Cold-Electron Bolometers (SCEB) with a superconducting absorber and a SIS' (Superconductor-Insulator-Weak Superconductor) Tunnel Junctions has been proposed. The current-biased SCEBs are connected in series for DC and in parallel for HF signal. A signal is concentrated to the absorber through the capacitance of tunnel junctions and additional capacitance for coupling of superconducting islands. Due to dividing power between an array of SCEBs and increasing responsivity, the noise matching is so effective that the photon NEP could be easily achieved at 300 mK with a room temperature JFET readout. The concept has been developed for matching with JFET readout for BOOMERanG balloon telescope. BOOMERanG is devoted for measuring the CMB polarization.

We have studied the sensitivity of a superconducting NbN hot electron bolometer mixer integrated with a spiral antenna at 4.3 THz. Using hot/cold blackbody loads and a beam splitter all in vacuum, we measured a double sideband receiver noise temperature of 1300 K at the optimum local oscillator (LO) power of 330 nW, which is about 12 times the quantum noise (hν/2k_B). Our result indicates that there is no sign of degradation of the mixing process at the super-THz frequencies. Also, a measurement method is introduced where the hot/cold response of the receiver is recorded at constant voltage bias of the mixer, while varying the LO power. We argue that this method provides an accurate measurement of the receiver noise temperature, which is not influenced by the LO power fluctuations and the direct detection effect. Moreover, our sensitivity data suggests that one can achieve a receiver noise temperature of 1420 K at the frequency of [OI] line (4.7 THz), which is scaled from the sensitivity at 4.3 THz with frequency.

The Band 3 receiver, covering the 84-116 GHz frequency band is one of the 10 channels that will be installed on the Atacama Large Millimeter Array (ALMA). A total of 73 units have to be built in two phases: 8 preproduction and then 65 production units. This paper reports on the assembly, testing and performance of the preproduction series of these state-of-the-art millimeter receivers.

Bicep is a ground-based millimeter-wave bolometric array designed to target the primordial gravity wave signature on the B-mode polarization of the cosmic microwave background (CMB) at degree angular scales. Currently in its third year of operation at the South Pole, Bicep is measuring the CMB polarization with unprecedented sensitivity at 100 and 150 GHz in the cleanest available 2% of the sky, as well as deriving independent constraints on the diffuse polarized foregrounds with select observations on and off the Galactic plane. Instrument calibrations are discussed in the context of rigorous control of systematic errors, and the performance during the first two years of the experiment is reviewed.

CℓOVER is a multi-frequency experiment optimised to measure the Cosmic Microwave Background (CMB) polarization, in particular the B-mode component. CℓOVER comprises two instruments observing respectively at 97 GHz and 150/225 GHz. The focal plane of both instruments consists of an array of corrugated feed-horns coupled to TES detectors cooled at 100 mK. The primary science goal of CℓOVER is to be sensitive to gravitational waves down to r ~ 0.03 (at 3σ)in two years of operations.

BICEP2/SPUD is the new powerful upgrade of the existing BICEP1 experiment, a bolometric receiver to study the polarization of the cosmic microwave background radiation, which has been in operation at the South Pole since January 2006. BICEP2 will provide an improvement up to 10 times mapping speed at 150 GHz compared to BICEP1, using the same BICEP telescope mount. SPUD, a series of compact, mechanically-cooled receivers deployed on the DASI mount at the Pole, will provide similar mapping speed in to BICEP2 in three bands, 100, 150, and 220 GHz. The new system will use large TES focal plane arrays to provide unprecedented sensitivity and excellent control of foreground contamination.

We are developing antenna-coupled Transition Edge Sensor (TES) bolometers to be used in the focal planes of telescopes mapping Cosmic Microwave Background (CMB) polarization anisotropies. These detectors will be both dual-polarized and ultra-wide band, each containing several frequency channels. Arrays of such detectors could realize mapping speeds nearly an order of magnitude higher than previously deployed technology while naturally facilitating foreground removal. For such detectors to be useful, the antennas must have a high gain and a low cross-polarization. We have designed a novel modification of DuHamel's Sinuous antenna that couples to a contacting lens and is driven by integrated microstrip feed-lines. The integrated feed lines allow the antenna to interface with microstrip circuits and bolometers in a way that is planar and scalable to kilo-pixel arrays. We have demonstrated the polarization and beam properties with scale model antennas that operate at 1-12 GHz.

We describe the design and performance of polarization selective antenna-coupled TES arrays that will be used in several upcoming Cosmic Microwave Background (CMB) experiments: SPIDER, BICEP-2/SPUD. The fully lithographic polarimeter arrays utilize planar phased-antennas for collimation (F/4 beam) and microstrip filters for band definition (25% bandwidth). These devices demonstrate high optical efficiency, excellent beam shapes, and well-defined spectral bands. The dual-polarization antennas provide well-matched beams and low cross polarization response, both important for high-fidelity polarization measurements. These devices have so far been developed for the 100 GHz and 150 GHz bands, two premier millimeter-wave atmospheric windows for CMB observations. In the near future, the flexible microstrip-coupled architecture can provide photon noise-limited detection for the entire frequency range of the CMBPOL mission. This paper is a summary of the progress we have made since the 2006 SPIE meeting in Orlando, FL.

We report on the design and tests of a prototype of the Millimeter-wave Bolometric Interferometer (MBI). MBI is designed to make sensitive measurements of the polarization of the cosmic microwave background (CMB). It combines the differencing capabilities of an interferometer with the high sensitivity of bolometers at millimeter wavelengths. The prototype, which we call MBI-4, views the sky directly through four corrugated horn antennas. MBI ultimately will have ~ 1000 antennas. These antennas have low sidelobes and nearly symmetric beam patterns, so spurious instrumental polarization from reflective optics is avoided. The MBI-4 optical band is defined by filters with a central frequency of 90 GHz. The set of baselines, determined by placement of the four antennas, results in sensitivity to CMB polarization fluctuations over the multipole range ℓ = 150 - 270. The signals are combined with a Fizeau beam combiner and interference fringes are detected by an array of spider-web bolometers. In order to separate the visibility signals from the total power detected by each bolometer, the phase of the signal from each antenna is modulated by a ferrite-based waveguide phase shifter. Initial tests and observations have been made at Pine Bluff Observatory (PBO) outside Madison, WI.

Many studies on the formation of stars and planets require high angular and high spectral resolution in the far-infrared regime. Even with the upcoming operation of the Herschel Space Observatory, ALMA, and JWST, angular resolutions of better than 1 arcsec combined with high spectral resolution in the crucial far-infrared domain of 1 THz to ~ 10 THz (300 μm to 30 μm) are still beyond observational reach. Only a far-infrared heterodyne interferometer can close this gap. Here we present the general requirements for a FIR heterodyne interferometer in space and address a number of critical key technologies needed for such an instrument.

We present a concept for BLISS, a sensitive far-IR-submillimeter spectrograph for SPICA. SPICA is a JAXA-led mission featuring a 3.5-meter telescope actively cooled to below 5K, envisioned for launch in 2017. The low-background platform is especially compelling for moderate-resolution survey spectroscopy, for which BLISS is designed. The BLISS / SPICA combination will offer line sensitivities below 10^-20W m^-2 in modest integrations, enabling rapid survey spectroscopy of galaxies out to redshift 5. The far-IR fine-structure and molecular transitions which BLISS / SPICA will measure are immune to dust extinction, and will unambiguously reveal these galaxies' redshifts, stellar and AGN contents, gas properties, and heavy-element abundances. Taken together, such spectra will reveal the history of galaxies from 1 GY after the Big Bang to the present day. BLISS is comprised of five sub-bands, each with two R ~ 700 grating spectrometer modules. The modules are configured with polarizing and dichroic splitters to provide complete instantaneous spectral coverage in two sky positions. To approach background-limited performance, BLISS detectors must have sensitivities at or below 5 × 10^-20W Hz^-1/2, and the format is 10 arrays of several hundred pixels each. It is anticipated that these requirements can be met on SPICA's timescale with leg-isolated superconducting (TES) bolometers cooled with a 50 mK magnetic refrigerator.

The Atacama Cosmology Telescope is a six meter, off-axis Gregorian telescope for measuring the cosmic microwave background at arcminute resolutions. The Millimeter Bolometer Array Camera (MBAC) is its current science instrument. Erected in the Atacama Desert of Chile in early 2007, it saw first light with the MBAC on 22 October 2007. In this paper we review its performance after one month of observing, focusing in particular on issues surrounding the alignment of the optical system that impact the sensitivity of the experiment. We discuss the telescope motion, pointing, and susceptibility to thermal distortions. We describe the mirror alignment procedure, which has yielded surface deviations of 31 μm rms on the primary and 10 μm rms on the secondary. Observations of planets show that the optical performance is consistent with the telescope design parameters. Preliminary analysis measures a solid angle of about 215 nanosteradians with a full width at half maximum of 1.44 arcminutes at 145 GHz.

We report measurements of the fluctuations in atmospheric emission (atmospheric noise) above Mauna Kea recorded with Bolocam at 143 GHz. These data were collected in November and December of 2003 with Bolocam mounted on the Caltech Submillimeter Observatory (CSO), and span approximately 40 nights. Below ≃ 0.5 Hz, the data time-streams are dominated by the f^-δ atmospheric noise in all observing conditions. We were able to successfully model the atmospheric fluctuations using a Kolmogorov-Taylor turbulence model for a thin wind-driven screen in approximately half of our data. Based on this modeling, we developed several algorithms to remove the atmospheric noise, and the best results were achieved when we described the fluctuations using a low-order polynomial in detector position over the 8 arcminute focal plane. However, even with these algorithms, we were not able to reach photon-background-limited instrument photometer (BLIP) performance at frequencies below ≃ 0.5 Hz in any observing conditions. Therefore, we conclude that BLIP performance is not possible from the CSO below ≃ 0.5 Hz for broadband 150 GHz receivers with subtraction of a spatial atmospheric template on scales of several arcminutes.

The 6-meter Atacama Cosmology Telescope will map the cosmic microwave background at millimeter wavelengths. The commissioning instrument for the telescope, the Millimeter Bolometer Array Camera, is based on a refractive optical system which simultaneously images three separate fields of view at three different frequencies: 145, 220, and 280 GHz. Each frequency band contains around twelve individual optical elements at five different temperature stages ranging from 300 K to 300 mK and a 32 x 32 array of Transition Edge Sensor bolometers at 300 mK. We discuss the design of the close-packed on-axis optical design of the three frequencies. The thermal design and performance of the system are presented in the context of the scientific requirements and observing schedule. A major part of the design was the incorporation of multiple layers of magnetic shielding. We discuss the performance of the 145 GHz optical system in 2007 and the implementation of the additional two frequency channels in 2008.

CRUSH is an approach to data analysis under noise interference, developed specifically for submillimeter imaging arrays. The method uses an iterated sequence of statistical estimators to separate source and noise signals. Its filtering properties are well-characterized and easily adjusted to preference. Implementations are well-suited for parallel processing and its computing requirements scale linearly with data size - rendering it an attractive approach for reducing the data volumes from future large arrays.

Z-Spec is a cryogenic, broadband, millimeter-wave grating spectrometer. It is capable of obtaining many spectral lines simultaneously because of its unprecedented broad bandwidth (185-305GHz). The bandpass covers the 1mm atmospheric transmission window with a resolving power of 250-400. Z-Spec uses 160 silicon nitride micromesh bolometers cooled down to less than 100mK for background-limited performance. The unique capability of Z-Spec to detect multiple lines simultaneously allows us to obtain information efficiently on the physical and chemical conditions of nearby Ultra-luminous Infrared Galaxies (ULIRGs) powered by starbursts or Active Galactic Nuclei. Here we report on new millimeter-wave broadband data for ULIRGs acquired with Z-Spec and the noise performance and achieved sensitivity in observations with the CSO. We found that during the observations the noise scales with the atmospheric opacity and can be explained well by our sensitivity model, considering the photon noise originating from the sky and the telescope, as well as the detector and electronics noise. The photon noise is found to dominate the total noise.

A prototype Q-band millimeter-wave heterodyne receiver based on monolithic microwave integrated circuit (MMIC) chips is designed and tested. The MMIC chips, including two three-stage 31.3-45GHz low-noise amplifier (LNA), a diode balanced mixer and a 4-12GHz IF amplifier, are fabricated by a 0.15-um Gallium-Arsenide (GaAs) metamorphic high-electron mobility transistor (MHEMT) foundry service. The MMIC chips are measured by probe in the gain stage. The three-stage 31.3-45GHz LNA MMIC exhibits 31-35dB gain and 2.8-3.5dB noise figure under room temperature environment. The balanced diode mixer with 31.3-45.0GHz RF frequency range and 27.3-33GHz LO frequency range shows 10-13dB conversion loss under 10-dBm LO pumping over 4-12GHz IF frequency range. The LO power of the mixer is provided by a phase-locked GaAs hetero-junction bipolar transistor (HBT) MMIC voltage-controlled oscillator cascaded by a buffer amplifier. The packaged modules of the individual MHEMT MMIC receiver components are designed for testing under 15-20K cryogenic operating temperature to ensure the low-noise performance. A compact multi-chip receiver module design concept will be presented.

FTS-2 is an imaging Fourier transform spectrometer (IFTS) being developed for use with SCUBA-2, the second generation, wide-field, submillimetre camera which will operate at the James Clerk Maxwell Telescope (JCMT). The FTS-2 interferometer uses a folded Mach-Zehnder configuration and will provide simultaneous broadband spectral imaging across both the 850 and 450 μm bands with variable resolution ranging from resolving powers of R ~10 to 5000. Details of the instrument design, optical modeling, data reduction pipeline and calibration plan which have changed since the project CDR are discussed, along with preliminary results of lab integration and testing.

We describe a procedure for measuring the full spatial state of coherence to which a bolometric detector is sensitive. It is based on the result that the expectation value of the output of any detector is given by the contraction of two tensor fields, one of which describes the state of coherence of the incoming radiation, and the other describes the state of coherence of the field to which the detector is sensitive. It follows that if a detector is illuminated by two coherent point sources and the phase of one source rotated relative to the other, the detector output displays a fringe. By repeating the process with different source locations, the entire detector coherence tensor can be reconstructed from the recorded complex visibilities.

The present status of the development of an extrinsic photoconductor based on a high-purity GaAs is reported. This photoconductor utilizing the shallow donor levels in GaAs and is highly sensitive for incident terahertz photons in the wavelength range 150 to 300 micron. The n-type GaAs crystal has been growth by liquid phase epitaxial (LPE) method, which is suitable to obtain thick and high-purity GaAs. The impurity concentration in GaAs layer has been decreased to the order of 10¹³ atoms/cm^-3. By doping the donors lightly in the LPE growth process, C/Si, (background doped) Se and Te doped GaAs layers has been fabricated. The GaAs photoconductors using these crystals are sensitive in longer wavelength region than Ge:Ga photoconductors used in the past far-infrared astronomical observations. The most sensitive detector is obtained with C or Si background doped GaAs, of which NEP is reached to 3×10^-16 W/Hz^0.5 at the temperature of 1.5 K, at 290 micron, the peak of its responsivity spectrum. A balloon-borne telescope utilizing our GaAs photoconductors, Tera-GATE (THz observation with GaAs photoconductors and a balloon-borne Telescope) is now under development. The Tera-GATE is a 69 cm diameter telescope. On its focal plane, a photoconductor array with Winston cone has 2-mm entrance aperture and leads the incident photons to a cavity where 0.5-mm size photoconductor is installed. Measured optical efficiency of the cone/cavity system is in an acceptable range ~40 percent.

The energy resolution of a detector is related to the figure of merit NEP×√τ which is proportional to the heat capacity of the detector. Hot electron (cold electron) devices have much lower heat capacity than bolometers with silicon nitride based thermal isolation. Traditional hot electron bolometers (HEB) require sub-micron fabrication for use at submm wavelengths and it is difficult to simultaneously couple radiation and read out these devices. The 2D electron gas (2DEG) in a semiconductor heterojunction effectively acts as a metal film with a thickness of a few angstroms and a tunable density and electron mobility. We describe a HEB that uses a 2DEG as an absorber and present simulations of optical coupling schemes for this type of detector including an antenna coupled to a coplanar waveguide with distributed 2DEG absorbers.

The flight model of the SPIRE instrument underwent several test campaigns in a test facility at the Rutherford Appleton Laboratory (RAL) in the UK. A final dark campaign, completed in March 2007, provided an environment virtually free from optical radiation. This allowed re-determining the fundamental model parameters of the NTD spider web bolometer detector arrays in the new environment. The tests reported in this paper produced a fairly homogeneous dataset to investigate white noise and 1/f noise at different bias voltages, bias frequencies, and bath temperatures. We find that the white noise performance is in excellent agreement with the model predictions, once we correct the low frequency signal variations that are due to temperature fluctuations of the thermal bath at about 300 mK. The temperature of the thermal bath (detector array base plate) is measured by thermistor pixels that are part of the bolometer arrays. A residual 1/f component beyond those variations is hardly detected. This unexpected stability is very welcome and will positively impact photometer scan maps, the most popular observing mode of SPIRE.

SCUBA-2 is a new wide-field submillimeter continuum instrument being commissioned on the James Clerk Maxwell Telescope on Mauna Kea in Hawaii. SCUBA-2 uses large-scale arrays of superconducting bolometers with SQUID- (superconducting quantum interference device) based multiplexing and amplification. The sensitivity of the devices that compose the detector arrays to magnetic fields is such that magnetic shielding, consisting of superconducting and high-permeability materials, was fitted to the detector enclosure at 1 K to reduce the magnetic field strength at the focal plane. This paper describes the design and construction of the cryogenic shielding, and presents verification measurements. The shielding performance was found to meet the instrument requirements, and compared well to the modelled results.

We describe design of two-polarization imaging array of 7 antenna-coupled TES-bolometers. The fabrication procedure involves both electron beam lithography and convenient optical lithography resulting in submicron definition of TES absorber films (down to ~ 0.2 μm) integrated within planar submm-wave antenna. Concept of matching optics between the long-focus optical telescope and lens-antenna TES bolometer array is described. Two-mirror short-focusing beam concentrator in combination with image rotator provides signal coupling to immersion lenses of the array. Each TES bolometer is coupled via microstrip transmission line to only one polarization of two-polarization crossed double-slot lens-antenna. Design of cryogenic 0.3-K system accommodating the matching optics is presented. We describe multiplexing readout scheme, which combines tomography, rotational scanning of the image and frequency domain division methods that drastically reduce the amount of wiring and substantially increase the final image resolution, especially for low-dimension arrays.

The detector arrays for the SCUBA-2 instrument consist of TES bolometers with superconducting amplifier and multiplexing circuits based on Superconducting Quantum Interference Devices (SQUIDs). The SCUBA-2 TES arrays and their multiplexed SQUID readouts need to be set-up carefully to achieve correct performance. Algorithms have been developed and implemented based on the first available commissioning grade detector, enabling the array to be set up and optimized automatically.

We have designed a detector package to house a superconducting bolometer array, SQUID multiplexers, bias and integration circuitry, optical filtering, electrical connectors, and thermal/mechanical interfaces. This package has been used successfully in the GISMO 2mm camera, a 128-pixel camera operating at a base temperature of 270mK. Operation at lower temperatures is allowed by providing direct heat sinking to the SQUIDs and bias resistors, which generate the bulk of the dissipation in the package. Standard electrical connectors provide reliable contact while enabling quick installation and removal of the package. Careful design has gone into the compensation for differing thermal expansions, the need for heat sinking of the bolometer array, and the placement of magnetic shielding in critical areas. In this presentation, we detail the design and performance of this detector package and describe its scalability to 1280-pixel arrays in the near future.

The Atacama Cosmology Telescope observes the Cosmic Microwave Background with arcminute resolution from the Atacama desert in Chile. For the first observing season one array of 32 x 32 Transition Edge Sensor (TES) bolometers was installed in the primary ACT receiver, the Millimeter Bolometer Array Camera (MBAC). In the next season, three independent arrays working at 145, 220 and 280 GHz will be installed in MBAC. The three bolometer arrays are each coupled to a time-domain multiplexer developed at the National Institute of Standard and Technology, Boulder, which comprises three stages of superconducting quantum interference devices (SQUIDs). The arrays and multiplexers are read-out and controlled by the Multi Channel Electronics (MCE) developed at the University of British Columbia, Vancouver. A number of experiments plan to use the MCE as read-out electronics and thus the procedure for tuning the three stage SQUID system is of general interest. Here we describe the automated array tuning procedures and algorithms we have developed. During array tuning, the SQUIDs are biased near their critical currents. SQUID feedback currents and lock points are selected to maximize linearity, dynamic range, and gain of the SQUID response curves. Our automatic array characterization optimizes the tuning of all three stages of SQUIDs by selecting over 1100 parameters per array during the first observing season and over 2100 parameters during the second observing season. We discuss the timing, performance, and reliability of this array tuning procedure as well as planned and recently implemented improvements.

We discuss the development, at Argonne National Laboratory, of a four-pixel camera suitable for photometry of distant dusty galaxies located by Spitzer and SCUBA, and for study of other millimeter-wave sources such as ultra-luminous infrared galaxies, the Sunyaev-Zeldovich (SZ) effect in clusters, and galactic dust. Utilizing Frequency Selective Bolometers (FSBs) with superconducting Transition-Edge Sensors (TESs), each of the camera's four pixels is sensitive to four colors, with frequency bands centered approximately at 150, 220, 270, and 360 GHz. The current generation of these devices utilizes proximity effect superconducting bilayers of Mo/Au or Ti/Au for TESs, along with frequency selective circuitry on membranes of silicon nitride 1 cm across and 1 micron thick. The operational properties of these devices are determined by this circuitry, along with thermal control structures etched into the membranes. These etched structures do not perforate the membrane, so that the device is both comparatively robust mechanically and carefully tailored in terms of its thermal transport properties. In this paper, we report on development of the superconducting bilayer TES technology and characterization of the FSB stacks. This includes the use of new materials, the design and testing of thermal control structures, the introduction of desirable thermal properties using buried layers of crystalline silicon underneath the membrane, detector stability control, and optical and thermal test results. The scientific motivation, FSB design, FSB fabrication, and measurement results are discussed.

Future space experiments will require large arrays of sensitive detectors in the submillimeter and millimeter range. Superconducting transition-edge sensors (TESs) are currently under heavy development to be used as ultra sensitive bolometers. In addition to good performance, the choice of material depends on long term stability (both physical and chemical) along with a good reproducibility and uniformity in fabrication. For this purpose we are investigating the properties of co-evaporated NbSi thin films. NbSi is a well-known alloy for use in resistive thermometers. We present a full low temperature characterization of superconductive NbSi films. In order to tune the critical temperature of the NbSi thermometers down to the desired range, we have to adjust the concentration of niobium in the NbSi alloy. Tests are made using 4He-cooled cryostats, 300mK 3He mini-fridges, Resistance Bridges and commercial SQUID. Measured parameters are the critical temperature, the sharpness of the transition. Noise measurements are on-going.

We describe the Submillimeter Array (SMA) Polarimeter, a polarization converter and feed multiplexer installed on the SMA. The polarimeter uses narrow-band quarter-wave plates to generate circular polarization sensitivity from the linearly-polarized SMA feeds. The wave plates are mounted in rotation stages under computer control so that the polarization handedness of each antenna is rapidly selectable. Positioning of the wave plates is found to be highly repeatable, better than 0.2 degrees. Although only a single polarization is detected at any time, all four cross correlations of left- and right-circular polarization are efficiently sampled on each baseline through coordinated switching of the antenna polarizations in Walsh function patterns. The initial set of anti-reflection coated quartz and sapphire wave plates allows polarimetry near 345 GHz; these plates have been have been used in observations between 325 and 350 GHz. The frequency-dependent cross-polarization of each antenna, largely due to the variation with frequency of the retardation phase of the single-element wave plates, can be measured precisely through observations of bright point sources. Such measurements indicate that the cross-polarization of each antenna is a few percent or smaller and stable, consistent with the expected frequency dependence and very small alignment errors. The polarimeter is now available for general use as a facility instrument of the SMA.

We report upon the development of a 190 GHz MMIC frequency doubler and 380 GHz sub-harmonic mixer using foundry planar Schottky diodes. The devices have been fabricated by the company UMS using their BES process, and post-processed afterwards to transfer the GaAs circuit membranes onto a quartz substrate. This novel substrate transfer technique is presented. Preliminary measurements give a doubler output power over 3 mW in the frequency range 170-205 GHz.

The Combined Array for Research in Millimeter-wave Astronomy (CARMA) have carried out a water vapor radiometer (WVR) project to test the WVR phase correction technique for better observational effciency. We have built two uncooled, but temperature-regulated, 22 GHz WVR prototypes to explore the feasibility of the technique. To better isolate the effects of instrumental and atmospheric instabilities, we have optimized theWVR design for simplicity with less high frequency components. The calibration system is Dicke switch with a single ambient load. The thermal regulation system consists of heaters and multi-stage insulation. We have completed testing of the WVR prototypes in a laboratory and at the CARMA site. The gain stability is about 20-100 mK and the front-end temperature rms is about a few mK to hundreds, depending on weather conditions. Based on the site tests, the sky temperature at 22 GHz usually varies a few K in 15 minutes, which is not necessary due to the atmospheric water vapor. Such short time-scale background temperature variation overwhelms the limit of the WVR dynamic range. Moreover, we have compared the WVR data rms with the phase monitor at the site and obtain a scale factor of the 22 GHz water vapor line, 6-12, which is consistent with the results of other WVR projects. We suggest that expanding the WVR dynamic range with diode detector models and a better thermal regulation system are keys to the success of the CARMA WVR phase correction.

Finlines are planar structures which allow broadband and low loss transition from waveguide to planar circuits. Their planar structure and large substrate makes them ideal for integration with other planar circuits and components, allowing the development of an on chip polarimeter. We have developed a method of extending the employment of finlines to thick substrates with high dielectric constants by drilling or etching small holes into the substrate, lowering the effective dielectric constant. We present the results of scale model measurements at 15GHz and cryogenic measurements at 90GHz which illustrate the excellent performance of finline transitions with porous substrates and the suitability of this technique for extending the bandwidth of finline transitions.

Astrophysical experiments dedicated to the study of the Cosmic Microwave Background are in needs of very well defined beam shape in order to get an accurate re-construction of the anisotropies power spectrum. These beams have to be carefully designed, but also properly characterised. Some of these instruments will be located in a cryostat for which filters and windows are necessary, and the effects of these additional optical components on the beam shape need to be taken into account. We present here, measurements of such effects on the co- and cross-polarisation radiation patterns of corrugated horns using a Vector Network Analyser.

Adiabatic demagnetization refrigerators (ADRs) can provide very low temperatures (< 100mK), making them an attractive option for cooling millimeter and submillimeter detectors. One drawback to their use has been the bulky electronic equipment that was often needed to operate them. In this paper, we present a compact, ADR controller that is designed for applications such as scientific ballooning and spaceflight where weight and reliability are primary concerns. The complete controller is contained on a 160mm by 100mm circuit card. A prototype has been tested with a single-stage ADR system. A minimum temperature of 180mK was achieved and stable control was demonstrated with an RMS temperature noise of 4.4 uK and a 1/f knee of order 1mHz. The dominant source of noise is digitization noise in the thermometer readout. Three cards on a backplane are currently being set up to control a three-stage ADR that is designed for continuous operation at 100mK. Additionally, a lower noise control card is under development.

The Goddard IRAM Superconducting Millimeter Observer (GISMO) is a new superconducting bolometer array camera for the IRAM 30 Meter Telescope on Pico Veleta, Spain. GISMO uses a 3He/4He cooler mounted to a liquid He/LN2 cryostat to cool the bolometer array and SQUID electronics to an operating temperature of 260mK. The bolometer array is based on the backshort-under-grid architecture and features 128 2mm square absorbing pixels. A 101mm diameter anti-reflection coated silicon lens is used to define the beam. A single cold pupil stop prevents warm radiation from reaching the array, but no other stops are used. In the beam, filters and a cold baffling and stray light suppression system were used to define the bandpass and prevent out-of-band radiation to a very high level, including out-of-band radiation leaking through the metal-mesh filters from extreme angles. We present a detailed description of this optical design and its performance. A comprehensive report of the electronics and cryogenic integration are also included.

We describe the design, construction, and characterization results of a waveguide Orthomode Transducer (OMT) for the 3 mm band (84-116 GHz.) The OMT is based on a symmetric backward coupling structure and has a square waveguide input port (2.54 mm × 2.54 mm) and two single-mode waveguide outputs: a standard WR10 rectangular waveguide (2.54 mm × 1.27 mm,) and an oval waveguide with full-radius corners. The reverse coupling structure is located in the common square waveguide arm and splits one polarization signal in two opposite rectangular waveguide sidearms using broadband -3 dB E-plane branch-line hybrid couplers. The device was optimized using a commercial 3D electromagnetic simulator. The OMT consists of two mechanical blocks fabricated in split-block configuration using conventional CNC milling machine. From 84 to 116 GHz the measured input reflection coefficient was less than -17 dB, the isolation between the outputs was less than -50 dB, the cross polarization was less than -30 dB, and the transmission was larger than -0.35 dB at room temperature for both polarization channels. The device is suitable for scaling to higher frequency.

The E and B Experiment, EBEX, is a Cosmic Microwave Background polarization experiment designed to detect or set upper limits on the signature of primordial gravity waves. Primordial gravity waves are predicted to be produced by inflation, and a measurement of the power spectrum of these gravity waves is a measurement of the energy scale of inflation. EBEX has sufficient sensitivity to detect or set an upper limit at 95% confidence on the energy scale of inflation of < 1.4 × 10¹⁶ GeV. This article reviews our strategy for achieving our science goals and discusses the implementation of the instrument.

The Millimeter-Wave Bolometric Interferometer (MBI) is a ground-based instrument designed to measure the polarization anisotropies of the Cosmic Microwave Background (CMB) and contains a number of quasi-optical components, including a complex back-to-back system of corrugated feed-horn antennas. In this paper we use MBI as an example to demonstrate the existing modeling techniques and as a focus to develop extended modeling capabilities. The software we use to model this system targets the millimeter and sub-millimeter region of the electromagnetic spectrum and has been extended to efficiently model the performance of back-to-back corrugated horns embedded in larger optical systems. This allows the calculation of the coupling of radiation from the sky to the detector array through a back-to-back horn feed system.

The SB349 is a 32x32 readout multiplexer specifically designed for far IR photodetectors and is capable of operating at cryogenic temperatures at least as low as 1.8K. This readout is a capacitive-transimpedance amplifier multiplexed to eight outputs and is buttable on two sides to form a 64x64 mosaic array. It features eight selectable gain settings, auto zero for better input uniformity, sample-and-hold circuitry, and provisions to block the readout glow. A special, 2-micron cryo-CMOS process was adopted to prevent freeze out and ensure low noise and proper operation at deep cryogenic temperatures. An overview of the design and the results of the tests performed on this device are reported in this paper.

We have been developing cryogenic readout integrated circuits (ROICs) for sensitive detectors at far-infrared and submillimeter wavelengths: The ROICs are constructed from SONY GaAs-JFETs, which have excellent performance even at less than 1 K. In addition, it is suitable device for ultra low background applications because of the extremely low gate leakage current. In the spring of 2008, we have designed and fabricated 4-ch AC-coupled capacitive transimpedance amplifiers and several basic digital circuits giving multiplex function for 32-element SIS photon detector array. The expected performance of the amplifier is as follows; open loop gain of >2000, power consumption <1.5 μW, and input referred noise ~ 1 μV/√Hz@1Hz. A summary of this 2008's experimental production and initial test results are presented in this paper.

This paper presents an ultra low noise instrumentation based on cryogenic electronic integrated circuits (ASICs : Application Specific Integrated Circuits). We have designed successively two ASICs in standard BiCMOS SiGe 0.35 μm technology that have proved to be operating at cryogenic temperatures. The main functions of these circuits are the readout and the multiplexing of SQUID/TES arrays. We report the cryogenic operation of a first ASIC version dedicated to the readout of a 2×4 pixel demonstrator array. We particularly emphasize on the development and the test phases of an ultra low noise (0.2 nV/√Hz) cryogenic amplifier designed with two multiplexed inputs. The cryogenic SiGe amplifier coupled to a SQUID in a FLL operating at 4.2 K is also presented. We finally report on the development of a second version of this circuit to readout a 3×8 detectors array with improved noise performances and upgraded functionalities.