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- Front Matter: Volume 8452
- Current/Near Term Cameras and Arrays
- Transition Edge Sensors: Array Design and Performance
- Transition Edge Sensors: Development and Readout
- Optical Design and Components
- Kinetic Inductance Detectors: Design, Readout, and Instruments
- Future Cameras and Focal Plane Arrays
- Terahertz Technology
- Coherent Detection Technologies
- CMB Instrumentation: Current/Near Term
- CMB Instrumentation: New Developments I
- CMB Instrumentation: New Developments II
- Mechanical Design and Cryogenics
- Poster Session
Front Matter: Volume 8452
Front Matter: Volume 8452
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This PDF file contains the front matter associated with SPIE Proceedings Volume 8452, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.
Current/Near Term Cameras and Arrays
A new era of wide-field submillimetre imaging: on-sky performance of SCUBA-2
Show abstract
SCUBA-2 is the largest submillimetre wide-field bolometric camera ever built. This 43 square arc- minute field-of-view instrument operates at two wavelengths (850 and 450 microns) and has been installed on the James Clerk Maxwell Telescope on Mauna Kea, Hawaii. SCUBA-2 has been successfully commissioned and operational for general science since October 2011. This paper presents an overview of the on-sky performance of the instrument during and since commissioning in mid- 2011. The on-sky noise characteristics and NEPs of the 450 μm and 850 μm arrays, with average yields of approximately 3400 bolometers at each wavelength, will be shown. The observing modes of the instrument and the on-sky calibration techniques are described. The culmination of these efforts has resulted in a scientifically powerful mapping camera with sensitivities that allow a square degree of sky to be mapped to 10 mJy/beam rms at 850 μm in 2 hours and 60 mJy/beam rms at 450 μm in 5 hours in the best weather.
The NIKA 2011 run: results and perspectives towards a permanent camera for the Pico Veleta observatory
M. Calvo,
M. Roesch,
F. X. Désert,
et al.
Show abstract
The Neel Iram Kids Array (NIKA) is a prototype instrument devoted to millimetric astronomy that has been
designed to be mounted at the focal plane of the IRAM 30m telescope at Pico Veleta (Spain). After the runs
of 2009 and 2010, we carried a third technical run in October 2011. In its latest configuration, the instrument
consists of a dual-band camera, with bands centered at 150 GHz and 220 GHz, each of them equipped with
116 pixels based on Lumped Element Kinetic Inductance Detectors. During the third run we tested many
improvements that will play a crucial role in the development of the final, kilopixel sized camera. In particular,
a new geometry based on a Hilbert curve has been adopted for the absorbing area of the LEKIDs, that makes
the detectors dual-polarization sensitive. Furthermore, a different acquisition strategy has been adopted, which
has allowed us to increase the photometric accuracy of the measurements, a fundamental step in order to get
scientifically significant data. In this paper we describe the main characteristics of the 2011 NIKA instrument
and outline some of its key features, discusse the results we obtained and give a brief outlook on the future NIKA
camera which will be installed permanently on site.
First observations with SuperCam and future plans
Show abstract
Supercam is a 345 GHz, 64-pixel heterodyne imaging array for the Heinrich Hertz Submillimeter Telescope
(HHSMT). By integrating SIS mixer devices with Low Noise Ampliers (LNAs) in 8 - 1x8 pixel modules, the
size needed for the cryostat and the complexity of internal wiring is signicantly reduced. All subsystems
including the optics, cryostat, bias system, IF boxes, and spectrometer have been integrated for all 64 pixels. In
the spring of 2012, SuperCam was installed on the HHSMT for an engineering run where it underwent system
level tests and performed rst light observations. In the fall of 2012 SuperCam will begin a 500 square degree
survey of the Galactic Plane in 12CO J=3-2. This large-scale survey will help answer fundamental questions
about the formation, physical conditions, and energetics of molecular clouds within the Milky Way. The data
set will be available via the web to all interested researchers.
Status of MUSIC, the MUltiwavelength Sub/millimeter Inductance Camera
Show abstract
We present the status of MUSIC, the MUltiwavelength Sub/millimeter Inductance Camera, a new instrument for the
Caltech Submillimeter Observatory. MUSIC is designed to have a 14', diffraction-limited field-of-view instrumented
with 2304 detectors in 576 spatial pixels and four spectral bands at 0.87, 1.04, 1.33, and 1.98 mm. MUSIC will be used
to study dusty star-forming galaxies, galaxy clusters via the Sunyaev-Zeldovich effect, and star formation in our own and
nearby galaxies. MUSIC uses broadband superconducting phased-array slot-dipole antennas to form beams, lumpedelement
on-chip bandpass filters to define spectral bands, and microwave kinetic inductance detectors to sense incoming
light. The focal plane is fabricated in 8 tiles consisting of 72 spatial pixels each. It is coupled to the telescope via an
ambient-temperature ellipsoidal mirror and a cold reimaging lens. A cold Lyot stop sits at the image of the primary
mirror formed by the ellipsoidal mirror. Dielectric and metal-mesh filters are used to block thermal infrared and out-ofband
radiation. The instrument uses a pulse tube cooler and 3He/ 3He/4He closed-cycle cooler to cool the focal plane to
below 250 mK. A multilayer shield attenuates Earth's magnetic field. Each focal plane tile is read out by a single pair of
coaxes and a HEMT amplifier. The readout system consists of 16 copies of custom-designed ADC/DAC and IF boards
coupled to the CASPER ROACH platform. We focus on recent updates on the instrument design and results from the
commissioning of the full camera in 2012.
First results of the polarimeter for the Large APEX Bolometer Camera (LABOCA)
Show abstract
An enhanced version of the ”Polarimeter für 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 and science verification phase. The combination of PolKa, LABOCA and APEX provides superior capabilities in mapping the polarization of the continuum at submillimeter wavelengths. We present here some preliminary results of the last commissioning run.
Design and first-light performance of TES bolometer arrays for submillimeter spectroscopy with ZEUS-2
Show abstract
We have recently commissioned the 2nd generation redshift(z) and Early Universe Spectrometer (ZEUS-2) at the Caltech
Submillimeter Observatory. ZEUS-2 is a long-slit grating spectrometer (R~1000) for observations in the submillimeter
wavelength regime that is optimized for observations of redshifted far-infrared spectral lines from galaxies in the early
universe. Here we report on the design and first light performance of the first TES bolometer array installed in ZEUS-2.
This array features 280 pixels each 1.26 mm square and arranged to provide ~35 pixel spectra at ~8 spatial positions on
the sky. A 1/4-wavelength back short of 100 micron and gold mesh absorber matching the impedance of free space
provides near 90% quantum efficiency for the 350 and 450 micron telluric windows. Array readout is done using SQUID
multiplexers and the Multichannel Electronics. We will also report on the progress to install two additional arrays tuned
to provide similar performance across the remaining telluric windows between 200-850 microns.
Transition Edge Sensors: Array Design and Performance
Scaling the summit of the submillimetre: instrument performance of SCUBA-2
Show abstract
SCUBA-2 is a revolutionary 10,000 pixel wide-field submillimetre camera, recently commissioned and now operational
at the James Clerk Maxwell Telescope (JCMT). Twin focal planes each consist of four 32 by 40 sub-arrays of
superconducting Transition Edge Sensor (TES) bolometers, the largest combined low temperature bolometer arrays in
operation, to provide simultaneous imaging at wavelengths of 450 and 850 microns. SCUBA-2 was designed to map
large areas of sky more than 100 times faster than the original ground breaking SCUBA instrument and has achieved this
goal. In this paper we describe the performance of the instrument and present results of characterising the eight science
grade TES bolometer arrays. We discuss the steps taken to optimise the setup of the TES arrays to maximise mapping
speed and show how critical changes to the sub-array module thermal design, the introduction of independent focal plane
and 1K temperature control and enhancements to the cryogenics have combined to significantly improve the overall
performance of the instrument.
TES arrays for the short wavelength band of the SAFARI instrument on SPICA
Show abstract
SPICA is an infra-red (IR) telescope with a cryogenically cooled mirror (~5K) with three instruments on board, one of
which is SAFARI that is an imaging Fourier Transform Spectrometer (FTS) with three bands covering the wavelength of
34-210 μm. We develop transition edge sensors (TES) array for short wavelength band (34-60 μm) of SAFARI. These
are based on superconducting Ti/Au bilayer as TES bolometers with a Tc of about 105 mK and thin Ta film as IR
absorbers on suspended silicon nitride (SiN) membranes. These membranes are supported by long and narrow SiN legs
that act as weak thermal links between the TES and the bath. Previously an electrical noise equivalent power (NEP) of
4×10-19 W/√Hz was achieved for a single pixel of such detectors. As an intermediate step toward a full-size SAFARI
array (43×43), we fabricated several 8×9 detector arrays. Here we describe the design and the outcome of the dark and
optical tests of several of these devices. We achieved high yield (<93%) and high uniformity in terms of critical
temperature (<5%) and normal resistance (7%) across the arrays. The measured dark NEPs are as low as 5×10-19 W/√Hz
with a response time of about 1.4 ms at preferred operating bias point. The optical coupling is implemented using
pyramidal horns array on the top and hemispherical cavity behind the chip that gives a measured total optical coupling
efficiency of 30±7%.
Ultra-low-noise transition edge sensors for the SAFARI L-band on SPICA
Show abstract
The Far-Infrared Fourier transform spectrometer instrument SAFARI-SPICA which will operate with cooled optics in a low-background space environment requires ultra-sensitive detector arrays with high optical coupling efficiencies over extremely wide bandwidths. In earlier papers we described the design, fabrication and performance of ultra-low-noise Transition Edge Sensors (TESs) operated close to 100mk having dark Noise Equivalent Powers (NEPs) of order 4 × 10−19W/√Hz close to the phonon noise limit and an improvement of two orders of magnitude over TESs for ground-based applications. Here we describe the design, fabrication and testing of 388-element arrays of MoAu TESs integrated with far-infrared absorbers and optical coupling structures in a geometry appropriate for the SAFARI L-band (110 − 210 μm). The measured performance shows intrinsic response time τ ~ 11ms and saturation powers of order 10 fW, and a dark noise equivalent powers of order 7 × 10−19W/√Hz. The 100 × 100μm2 MoAu TESs have transition temperatures of order 110mK and are coupled to 320×320μm2 thin-film β-phase Ta absorbers to provide impedance matching to the incoming fields. We describe results of dark tests (i.e without optical power) to determine intrinsic pixel characteristics and their uniformity, and measurements of the optical performance of representative pixels operated with flat back-shorts coupled to pyramidal horn arrays. The measured and modeled optical efficiency is dominated by the 95Ω sheet resistance of the Ta absorbers, indicating a clear route to achieve the required performance in these ultra-sensitive detectors.
Measurements of the optical performance of bolometers for SPICA/SAFARI
Show abstract
We have measured the optical response of detectors designed for SAFARI, the far-infrared imaging spectrometer for the SPICA satellite. To take advantage of SPICA's cooled optics, SAFARI’s three bolometer arrays are populated with extremely sensitive (NEP~2×10-19 W/√Hz) transition edge sensors with a transition temperature close to 100 mK. The extreme sensitivity and low saturation power (~4 fW) of SAFARI’s detectors present challenges to characterizing them. We have therefore built up an ultra-low background test facility with a cryogen-free high-capacity dilution refrigerator, paying careful attention to stray-light exclusion. Our use of a pulse-tube cooler to pre-cool the dilution refrigerator required that the SAFARI Detector System Test Facility provide a high degree electrical, magnetic, and mechanical isolation for the detectors. We have carefully characterized the performance of the test facility in terms of background power loading. The test facility has been designed to be flexible and easily reconfigurable with internal illuminators that allow us to characterize the optical response of the detectors. We describe the test facility and some of the steps we took to create an ultra-low background test environment. We have measured the optical response of two detectors designed for SAFARI’s short-wave wavelength band in combination with a spherical backshort and conical feedhorn. We find an overall optical efficiency of 40% for both, compared with an ideal-case predicted optical efficiency of 66%.
Transition Edge Sensors: Development and Readout
Low-dimensional phononic structures for ultra-low-noise transition edge sensors
Show abstract
Understanding the thermal behaviour of low-dimensional dielectric support structures patterned in <500 nm
dielectric membranes is an essential part of developing ultra-low-noise Transition Edge Sensors for space science.
To advance the technology further, we wish to produce phononic components that minimize low-temperature
(< 500 mK) thermal conductance, heat capacity, and thermal fluctuation noise, and thereby maximize sensitivity,
saturation power, and optical packing. We describe a technique for simulating the low-temperature thermal
behaviour of mesoscopic structures. Ballistic, elastic diffusive, localized and inelastic diffusive transport are
included, and the respective scattering lengths can be comparable with the scale sizes of the patterned features.
The technique computes the average fluxes of components having statistically characterized microstructure, the
spread in behaviour of notionally identical devices, and the RMS thermal fluctuation noise.
Improved performance of TES bolometers using digital feedback
Show abstract
Voltage biased, frequency multiplexed TES bolometers have become a widespread tool in mm-wave astrophysics. However, parasitic impedance and dynamic range issues can limit stability, performance, and multiplexing factors. Here, we present novel methods of overcoming these challenges, achieved through digital feedback, implemented on a Field-Programmable Gate Array (FPGA). In the first method, known as Digital Active Nulling (DAN), the current sensor (e.g. SQUID) is nulled in a separate digital feedback loop for each bolometer frequency. This nulling removes the dynamic range limitation on the current sensor, increases its linearity, and reduces its effective input impedance. Additionally, DAN removes constraints on wiring lengths and maximum multiplexing frequency. DAN has been fully implemented and tested. Integration for current experiments, including the South Pole Telescope, will be discussed. We also present a digital mechanism for strongly increasing stability in the presence of large series impedances, known as Digitally Enhanced Voltage Bias (DEVB).
Frequency division multiplexed readout of TES detectors with baseband feedback
Show abstract
SRON is developing an electronic system for the multiplexed read-out of an array of transition edge sensors (TES) by
combining the techniques of frequency domain multiplexing (FDM) with base-band feedback (BBFB). The astronomical
applications are the read-out of soft X-ray microcalorimeters and the far-infrared bolometers for the SAFARI instrument
on the Japanese mission SPICA. In this paper we derive the requirements for the read-out system regarding noise and
dynamic range in the context of the SAFARI instrument, and demonstrate that the current experimental prototype is
capable of simultaneously locking 57 channels and complies with these requirements.
Development of fast, background-limited transition-edge sensors for the background-limited infrared/sub-mm spectrograph (BLISS) for SPICA
Show abstract
We report experimental progress toward demonstrating background-limited arrays of membrane-isolated transition-edge sensors (TESs) for the Background Limited Infrared/Sub-mm Spectrograph (BLISS). BLISS is a space-borne instrument with grating spectrometers for wavelengths λ= 35-435 μm and with R= λ/Δλ~500. The goals for BLISS TESs are: noise equivalent power (NEP) = 5×10-20 W/Hz1/2 and response time τ<30ms. We expect background-limited performance from bilayers TESs with TC=65mK and G=15fW/K. However, such TESs cannot be operated at 50mK unless stray power on the devices, or dark power PD, is less than 200aW. We describe criteria for measuring PD that requires accurate knowledge of TC. Ultimately, we fabricated superconducting thermistors from Ir (TC≥135mK) and Mo/Cu proximitized bilayers, where TC is the thermistor transition temperature. We measured the Ir TES arrays in our 45mK base temperature adiabatic demagnetization refrigerator test system, which can measure up to eight 1x32 arrays simultaneously using a time-division multiplexer, as well as our single-pixel test system which can measure down to 15mK. In our previous Ir array measurements our best reported performance was NEP=2.5×10-19 W/Hz1/2 and τ~5ms for straight-beam TESs. In fact, we expected NEP 1.5×10-19W/Hz1/2 for meander beam TESs, but did not achieve this previously due to 1/f noise. Here, we detail improvements toward measuring the expected NEP and demonstrate NEP=(1.3±0.2)×10-19W/Hz1/2 in our single-pixel test system and NEP=(1.6±0.3)×10-19W/Hz1/2 in our array test system.
Optical Design and Components
Systematic effects introduced by lenses at mm-wavelengths in CMB applications
Show abstract
Telescopes for the next generation of CMB (Cosmic Microwave Background) experiments could be based on either
reflective (such as Planck, Clover) or refractive optics (BICEP, LSPE, SPIDER). Both techniques have advantages and
disadvantages. On-axis lens based telescopes can be compact while off-axis reflective configurations can be large. The
RF performances of mirror based telescopes are very well understood, whereas lens based systems have a lower
technology readiness level: specifically, the systematic effects (aberrations such as chromaticity, birefringence, losses,
standing waves and cross-polarisation) that they can introduce need to be accurately quantified at millimetre-wave. This
paper reports on both RF modelling and preliminary experimental studies of a lens coupled to a feed-horn antenna for
which the co- and cross-polarisation beam patterns are characterised.
Dielectrically embedded mesh half wave plate beam impact studies
Show abstract
An alternative solution to classic birefringent Half Wave Plates (HWP), based on the photolithographic techniques, has
been recently developed. This new device can offer a very good alternative as a polarisation modulator for future CMB
polarisation instruments. However, the systematic effects that this HWP will introduce in the overall instrument need to
be investigated.
We present a preliminary study of the impact of this dielectrically embedded HWP on the beam shape of a corrugated
horn and its performance across the beam. Using a W-band Vector Network Analyser, we measured the co- and crosspolarisation
beams of the HWP-horn system and the differential phase-shift introduced by the HWP across the beam.
Optical modeling of waveguide coupled TES detectors towards the SAFARI instrument for SPICA
Show abstract
The next generation of space missions targeting far-infrared wavelengths will require large-format arrays of extremely
sensitive detectors. The development of Transition Edge Sensor (TES) array technology is being developed for future
Far-Infrared (FIR) space applications such as the SAFARI instrument for SPICA where low-noise and high sensitivity is
required to achieve ambitious science goals.
In this paper we describe a modal analysis of multi-moded horn antennas feeding integrating cavities housing TES
detectors with superconducting film absorbers. In high sensitivity TES detector technology the ability to control the
electromagnetic and thermo-mechanical environment of the detector is critical. Simulating and understanding optical
behaviour of such detectors at far IR wavelengths is difficult and requires development of existing analysis tools.
The proposed modal approach offers a computationally efficient technique to describe the partial coherent response of
the full pixel in terms of optical efficiency and power leakage between pixels. Initial wok carried out as part of an ESA
technical research project on optical analysis is described and a prototype SAFARI pixel design is analyzed where the
optical coupling between the incoming field and the pixel containing horn, cavity with an air gap, and thin absorber layer
are all included in the model to allow a comprehensive optical characterization. The modal approach described is based
on the mode matching technique where the horn and cavity are described in the traditional way while a technique to
include the absorber was developed. Radiation leakage between pixels is also included making this a powerful analysis
tool.
Kinetic Inductance Detectors: Design, Readout, and Instruments
Dynamical behaviour of superconducting resonators under readout-frequency, readout-power, and signal-power switching
Show abstract
The sensitivities, saturation powers, and response times of Kinetic Inductance Detectors depend on the degree to
which the quasiparticle and phonon temperatures differ when readout and signal power are applied. Previously,
we proposed a model for saturation in KIDs, and found that hysteretic switching, which is seen experimentally,
emerges from the model in a natural way. Here we extend our work, and show through a diagrammatic rep-
resentation of operating-point trajectories that output pulse shapes can be calculated for non-hysteretic and
hysteretic changes of state driven by readout-frequency, readout-power, and signal-power pulses. The work has
several applications: (i) Understanding quasiparticle and phonon relaxation, and their dependence on film and
substrate thickness. (ii) Recovering quasiparticle cooling functions from measurements. (iii) Understanding
the relationship between optimum readout power and device and material parameters. (iv) Characterising the
time-dependent behaviour of photon-counting KIDs, including nonlinearity and pile up.
Electronics and data acquisition for kilopixels kinetic inductance camera
O. Bourrion,
C. Vescovi,
J. L. Bouly,
et al.
Show abstract
A digital frequency multiplexing electronics building block has been developed for the NIKA (New IRAM KID
Arrays) experience. It allows the real time monitoring of microwave kinetic inductance detectors (MKIDs)
arrays used for mm-wave astronomy. This electronics can monitor simultaneously 400 pixels over a 500MHz
bandwidth and requires only two coaxial cables for instrumenting such a large array. The chosen solution and
the performance achieved are presented in this paper.
MAKO: a pathfinder instrument for on-sky demonstration of low-cost 350 micron imaging arrays
Show abstract
Submillimeter cameras now have up to 104 pixels (SCUBA 2). The proposed CCAT 25-meter submillimeter telescope will feature a 1 degree field-of-view. Populating the focal plane at 350 microns would require more than 106 photon-noise limited pixels. To ultimately achieve this scaling, simple detectors and high-density multiplexing are essential. We are addressing this long-term challenge through the development of frequency-multiplexed superconducting microresonator detector arrays. These arrays use lumped-element, direct-absorption resonators patterned from titanium nitride films. We will discuss our progress toward constructing a scalable 350 micron pathfinder instrument focusing on fabrication simplicity, multiplexing density, and ultimately a low per-pixel cost.
Development of 1000 arrays MKID camera for the CMB observation
Show abstract
A precise measurement of the Cosmic Microwave Background (CMB) provides us a wealth of information about early universe. LiteBIRD is a future satellite mission lead by High Energy Accelerator Research Organization (KEK) and its scientific target is detection of the B-mode polarization of the CMB, which is a footprint of primordial gravitational waves generated during inflation era, but has not been successfully observed so far due to lack of sensitivity. Microwave Kinetic Inductance Detector (MKID) is one candidate of sensitive millimeterwave camera which will be able to detect the B-mode polarization. We have been developing MKID at National Astronomical Observatory of Japan (NAOJ) in cooperation with KEK and RIKEN for the focal plane detector of the LiteBIRD. The developed technologies are: fabrication process of MKIDs with epitaxially-formed aluminum (Al) on silicon (Si) wafer; optical system of the camera consisting of double-slot antenna with Si lens array; and readout circuit utilizing Fast Fourier Transform Spectrometer (FFTS). With these technologies, we designed a prototype MKIDs camera for the LiteBIRD.
MKID development for SuperSpec: an on-chip, mm-wave, filter-bank spectrometer
Show abstract
SuperSpec is an ultra-compact spectrometer-on-a-chip for millimeter and submillimeter wavelength astronomy. Its very small size, wide spectral bandwidth, and highly multiplexed readout will enable construction of powerful multibeam spectrometers for high-redshift observations. The spectrometer consists of a horn-coupled microstrip feedline, a bank of narrow-band superconducting resonator filters that provide spectral selectivity, and kinetic inductance detectors (KIDs) that detect the power admitted by each filter resonator. The design is realized using thin-film lithographic structures on a silicon wafer. The mm-wave microstrip feedline and spectral filters of the first prototype are designed to operate in the band from 195-310 GHz and are fabricated from niobium with at Tc of 9.2K. The KIDs are designed to operate at hundreds of MHz and are fabricated from titanium nitride with a Tc of ~ 2 K. Radiation incident on the horn travels along the mm-wave microstrip, passes through the frequency-selective filter, and is finally absorbed by the corresponding KID where it causes a measurable shift in the resonant frequency. In this proceedings, we present the design of the KIDs employed in SuperSpec and the results of initial laboratory testing of a prototype device. We will also brie describe the ongoing development of a demonstration instrument that will consist of two 500-channel, R=700 spectrometers, one operating in the 1-mm atmospheric window and the other covering the 650 and 850 micron bands.
Design considerations for a background limited 350 micron pixel array using lumped element superconducting microresonators
Christopher M. McKenney,
Henry G. Leduc,
Loren J. Swenson,
et al.
Show abstract
Future submillimeter telescopes will demand arrays with 106 pixels to fill the focal plane. MAKO is a 350 μm camera being developed to demonstrate the use of superconducting microresonators to meet the high multiplexing factors required for scaling to large-format arrays while offering background-limited single-pixel sensitivity. Candidate pixel designs must simultaneously meet many requirements. To achieve the desired noise equivalent powers it must efficiently absorb radiation, feature a high responsivity, and exhibit low intrinsic device noise. Additionally, the use of high resonator quality factors of order ~ 105 and resonant frequencies of order fres ≈ 100 MHz are desirable in order to reduce the per-pixel bandwidth to a minimum set by telescope scan speeds. This allows a maximum number of pixels to be multiplexed in a fixed electronic bandwidth. Here we present measurement results of the first MAKO prototype array which meets these design requirements while demonstrating sufficient sensitivity for background-limited operation at ground-based, far-infrared telescopes.
Future Cameras and Focal Plane Arrays
The GISMO-2 bolometer camera
Show abstract
We present the concept for the GISMO-2 bolometer camera, which we build for background-limited operation at the
IRAM 30 m telescope on Pico Veleta, Spain. GISMO-2 will operate simultaneously in the 1 mm and 2 mm
atmospherical windows. The 1 mm channel uses a 32 x 40 TES-based Backshort Under Grid (BUG) bolometer array, the
2 mm channel operates with a 16 x 16 BUG array. The camera utilizes almost the entire full field of view provided by
the telescope. The optical design of GISMO-2 was strongly influenced by our experience with the GISMO 2 mm
bolometer camera which is successfully operating at the 30m telescope. GISMO is accessible to the astronomical
community through the regular IRAM call for proposals.
The PILOT experiment for the measurement of interstellar dust polarization : the camera ground calibration
Show abstract
The Polarized Instrument for Long wavelength Observation of the Tenuous interstellar medium (PILOT) is a balloon borne experiment designed to measure the polarized emission from dust grains in the galaxy in the submillimeter range. The payload is composed of a telescope at the optical focus of which is placed a camera using 2048 bolometers cooled to 300 mK. The camera performs polarized optical measurements in two spectral bands (240 μm and 550 μm). The polarization measurement is based on a cryogenic rotating half-wave plate and a fixed mesh grid polarizer placed at 45o separating the beam into two orthogonal polarized components each detected by a detector array. The Institut d’Astrophysique Spatiale (Orsay, France) is responsible for the design, integration, tests and spectral calibration of the camera. Two optical benches have been designed for its imaging and polarization characterization and spectral calibration. Theses setups allow to validate the alignment of the camera cryogenic optics, to check the optical quality of the images, to characterize the time and intensity response of the detectors, and to measure the overall spectral response. A numerical photometric model of the instrument was developed for the optical configuration during calibration tests (spectral), functional tests (imager) on the ground, and flight configuration at the telescope focus, giving an estimate of the optical power received by the detectors for each configuration.
Sensitive semiconductor detectors of terahertz radiation for spaceborne applications based on Pb1-xSnxTe(In)
Show abstract
Doping of the lead telluride and related alloys with the group III impurities results in appearance of the unique physical
features of a material, such as persistent photoresponse, enhanced responsive quantum efficiency (up to 100
photoelectrons/incident photon), radiation hardness and many others. We present the physical principles of operation of
the photodetecting devices based on the group III-doped IV-VI including the possibilities of a fast quenching of the
persistent photoresponse, construction of the focal-plane array, new readout technique, and others. The advantages of
infrared photodetecting systems based on the group III-doped IV-VI in comparison with the modern photodetectors are
summarized. The spectra of the persistent photoresponse have not been measured so far because of the difficulties with
screening the background radiation. We report on the observation of strong persistent photoconductivity in
Pb0.75Sn0.25Te(In) under the action of monochromatic submillimeter radiation at wavelengths of 176 and 241 microns.
The sample temperature was 4.2 K, the background radiation was completely screened out. The sample was initially in
the semiinsulating state providing dark resistance of more than 100 GOhm. The responsivity of the photodetector is by
several orders of magnitude higher than in the state of the art Ge(Ga). The red cut-off wavelength exceeds the upper limit
of 220 microns observed so far for the quantum photodetectors in the uniaxially stressed Ge(Ga). It is possible that the
photoconductivity spectrum of Pb1-xSnxTe(In)covers all the submillimeter wavelength range.
Development of DESHIMA: a redshift machine based on a superconducting on-chip filterbank
Show abstract
Distant, dusty and extremely luminous galaxies form a key component of the high redshift universe, tracing the period of intense cosmic activity that ultimately gave rise to the present-day universe. These highly luminous galaxies, first detected in the ground-based submillimeter region, are however optically very faint, which hampers identification of the optical counterpart and the measurement of a redshift. We are developing a new direct-detection submm spectrograph DESHIMA. By taking advantage of the rapidly advancing technology of superconducting microresonators, DESHIMA will revolutionize the appearance and capabilities of a submm spectrograph. There will no longer be large grating optics; instead DESHIMA will be equipped with a single chip, onto which the entire system of a dispersive filterbank and MKID sensor array is integrated. This chip will host 5000-10000 MKID sensors to instantaneously cover the entire submillimeter wave band (320-950 GHz) with a resolution of f/Δf = 1000, further multiplied by 6-9 spatial pixels. With the broader bandwidth and higher detector sensitivity, DESHIMA will be very efficient compared to ALMA in picking up THz lines from submm galaxies with unknown redshifts. The expected outcome of this project is; 1) a record of the properties and evolution of distant luminous galaxies, 2) a powerful and compact multi-purpose spectrometer suitable for future ground base telescopes as well as satellite missions, and 3) the emergence of a new branch of observational astronomy based on flexible on-chip submillimeter optics.
The Kilopixel Array Pathfinder Project (KAPPa), a 16 pixel integrated heterodyne focal plane array
Show abstract
KAPPa (the Kilopixel Array Pathfinder Project) is developing key technologies to enable the construction of heterodyne
focal plane arrays in the terahertz frequency regime with ~1000 pixels. The leap to ~1000 pixels requires solutions to
several key technological problems before the construction of such a focal plane is possible. The KAPPa project will
develop a small (16-pixel) 2D integrated heterodyne focal plane array for the 660 GHz atmospheric window as a
technological pathfinder towards future kilopixel heterodyne focal plane arrays.
Terahertz Technology
Active local oscillator power stabilization for a hot electron bolometer heterodyne receiver
Show abstract
We report on the application of a new technique for actively stabilizing the power of a far infrared gas laser as the local
oscillator (LO) in a superconducting hot electron bolometer (HEB) heterodyne receiver system at 2.5 THz. The
technique utilizes PID feedback control of the local oscillator intensity by means of a voice-coil based swing arm
actuator placed in the beam path. The HEB itself is used as a direct detector to measure incident LO power whilst
simultaneously continuing to function as heterodyne mixer. Results presented here demonstrate a factor of 50
improvement in the measured total power and spectroscopic Allan variance time. Allan times of 30 seconds and 25
seconds respectively are shown for large and small area HEB's with a measured effective noise fluctuation bandwidth of
12 MHz. The technique is versatile and can be applied to any LO source and at any LO frequency.
Stabilized HEB-QCL heterodyne spectrometer at super-terahertz
Show abstract
We report a new experiment on a high-resolution heterodyne spectrometer using a 3.5 THz quantum cascade laser
(QCL) as local oscillator (LO) and a superconducting hot electron bolometer (HEB) as mixer by stabilizing both
frequency and amplitude of the QCL. The frequency locking of the QCL is demonstrated by using a methanol molecular
absorption line, a proportional-integral-derivative (PID) controller, and a direct power detector. We show that the LO
locked linewidth can be as narrow as 35 KHz. The LO power to the HEB is also stabilized by means of swing-arm
actuator placed in the beam path in combination of a second PID controller.
Terahertz-frequency waveguide HEB mixers for spectral line astronomy
Show abstract
We report on the development of waveguide-based mixers for operation beyond 2 THz. The mixer element is a
superconducting hot-electron bolometer (HEB) fabricated on a silicon-on-insulator (SOI) substrate. Because it is beyond
the capability of conventional machining techniques to produce the fine structures required for the waveguide embedding
circuit for use at such high frequencies, we employ two lithography-based approaches to produce the waveguide circuit:
a metallic micro-plating process akin to 3-D printing and deep reactive ion etching (DRIE) silicon micromachining.
Various mixer configurations have been successfully produced using these approaches. A single-ended mixer produced
by the metal plating technique has been demonstrated with a receiver noise temperature of 970 K (DSB) at a localoscillator
frequency of 2.74 THz. A similar mixer, produced using a silicon-based micro-machining technique, has a
noise temperature of 2000 K (DSB) at 2.56 THz. In another example, we have successfully produced a waveguide RF
hybrid for operation at 2.74 THz. This is a key component in a balanced mixer, a configuration that efficiently utilizes
local oscillator power, which is scarce at these frequencies. In addition to allowing us to extend the frequency of
operation of waveguide-based receivers beyond 2 THz, these technologies we employ here are amenable to the
production of large array receivers, where numerous copies of the same circuit, precisely the same and aligned to each
other, are required.
Local oscillator sub-systems for array receivers in the 1-3 THz range
Show abstract
Recent results from the Heterodyne Instrument for the 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 with emphasis on building a multi-pixel LO subsystem
for the scientifically important CII line around 1908 GHz. Recent results have shown that over 50 microwatts of output
power at 1.9 THz are possible with an optimized single pixel LO chain. These power levels are now sufficient to pump
array receivers in this frequency range. Further power enhancement can be obtained by cooling the chain to 120 K or by
utilizing in-phase power combining technology.
Membrane-based quasi-optical superconducting HEB mixers at terahertz frequencies
Show abstract
Superconducting Hot Electron Bolometer mixers offer the highest sensitivity for heterodyne detections at frequencies above 1 THz. Important efforts have been made these recent years to further increase the HEB mixers' sensitivity and working frequency and also to design multi-pixel configuration.
We present in this paper the developments of a non-standard quasi-optical membrane based HEB mixer where the commonly used focusing element, the silicon lens, is replaced by a micro-mirror and a membrane-based back-short. This configuration offers many advantages: easier processing for circuits at very high frequencies, better noise temperature brought by lower RF coupling loss and higher gain of the antenna. This design is also considered very attractive for multi-pixel receivers. The devices are made of phonon-cooled NbN HEB mixers processed on 1.4 μm thick stress-less Si3N4/Si02 membrane. Quasi-optical designs have been made for frequencies at 600 GHz and 2.5 THz. The design and the device fabrication process will be discussed and both DC and RF measurements at 600 GHz will be presented.
Coherent Detection Technologies
Sideband separating mixer for 600-720 GHz for ALMA band 9 upgrade
Show abstract
For high-frequency observational bands like ALMA (Atacama Large Millimeter Array) Band 9 (600—720 GHz), which
tend to be dominated by atmospheric noise, implementation of sideband-separating mixers can reduce, up to a factor of
two, the integration time needed to reach a certain signal-to-noise ratio for spectral line observations. Because of very
high oversubscription factor for observation in ALMA Band 9, an upgrade of the current Double Sideband (DSB) mixer
to a Two Sideband (2SB) configuration is a promising option for future ALMA development.
Here we present a developed 2SB mixer and a modified cartridge design. The 2SB mixer includes a waveguide RF
hybrid block, which have been produced on a micro-milling machine and equipped with standard Band 9 SIS mixer
devices. These two SIS mixers have been separately tested in DSB mode. The SSB noise temperature is within the
ALMA requirements of 336 K over 80% of the band, and 500 K over the entire band. The 2SB mixer has the sideband
rejection ratio better than 12 dB over the full RF band, which is also well within the ALMA specifications of 10 dB.
The ALMA photonic local oscillator system
Show abstract
The Atacama Large Millimeter Array (ALMA) Photonic Local Oscillator (PLO) is an advanced photonics system that
generates and distributes all of the Local Oscillator (LO) and timing references for the ALMA radio telescope array.
These LO and timing references are used by the receivers and electronics at the antennas, and by the Correlator in the
central building. Due to the unprecedented combination of high sky frequencies (up to 950 GHz) and long baseline
lengths of up to 15 kilometers, the ALMA 1st LO requirement is particularly stringent, with extremely precise timing and
synchronization needed down to the ~10 femtosecond level.
Performance highlights of the ALMA correlators
Alain Baudry,
Richard Lacasse,
Ray Escoffier,
et al.
Show abstract
Two large correlators have been constructed to combine the signals captured by the ALMA antennas deployed on the
Atacama Desert in Chile at an elevation of 5050 meters. The Baseline correlator was fabricated by a NRAO/European
team to process up to 64 antennas for 16 GHz bandwidth in two polarizations and another correlator, the Atacama
Compact Array (ACA) correlator, was fabricated by a Japanese team to process up to 16 antennas. Both correlators meet
the same specifications except for the number of processed antennas. The main architectural differences between these
two large machines will be underlined. Selected features of the Baseline and ACA correlators as well as the main
technical challenges met by the designers will be briefly discussed. The Baseline correlator is the largest correlator ever
built for radio astronomy. Its digital hybrid architecture provides a wide variety of observing modes including the ability
to divide each input baseband into 32 frequency-mobile sub-bands for high spectral resolution and to be operated as a
conventional 'lag' correlator for high time resolution. The various observing modes offered by the ALMA correlators to
the science community for 'Early Science' are presented, as well as future observing modes. Coherently phasing the
array to provide VLBI maps of extremely compact sources is another feature of the ALMA correlators. Finally, the status
and availability of these large machines will be presented.
CMB Instrumentation: Current/Near Term
BICEP2 and Keck Array operational overview and status of observations
Show abstract
The Bicep2 and Keck Array experiments are designed to measure the polarization of the cosmic microwave background (CMB) on angular scales of 2-4 degrees (ℓ = 50–100). This is the region in which the B-mode signal, a signature prediction of cosmic inflation, is expected to peak. Bicep2 was deployed to the South Pole at the end of 2009 and is in the middle of its third year of observing with 500 polarization-sensitive detectors at 150 GHz. The Keck Array was deployed to the South Pole at the end of 2010, initially with three receivers—each similar to Bicep2. An additional two receivers have been added during the 2011-12 summer. We give an overview of the two experiments, report on substantial gains in the sensitivity of the two experiments after post-deployment optimization, and show preliminary maps of CMB polarization from Bicep2.
Optimization and sensitivity of the Keck array
Show abstract
The Keck Array (SPUD) began observing the cosmic microwave background's polarization in the winter of 2011 at the South Pole. The Keck Array follows the success of the predecessor experiments BICEP and BICEP2, 1 using five on-axis refracting telescopes. These have a combined imaging array of 2500 antenna-coupled TES bolometers read with a SQUID- based time domain multiplexing system. We will discuss the detector noise and the optimization of the readout. The achieved sensitivity of the Keck Array is 11.5 μKCMB√s in the 2012 configuration.
The POLARBEAR experiment
Show abstract
We present the design and characterization of the POLARBEAR experiment. POLARBEAR will measure the polarization of the cosmic microwave background (CMB) on angular scales ranging from the experiment’s 3.5’ beam size to several degrees. The experiment utilizes a unique focal plane of 1,274 antenna-coupled, polarization sensitive TES bolometers cooled to 250 milliKelvin. Employing this focal plane along with stringent control over systematic errors, POLARBEAR has the sensitivity to detect the expected small scale B-mode signal due to gravitational lensing and search for the large scale B-mode signal from inflationary gravitational waves. POLARBEAR was assembled for an engineering run in the Inyo Mountains of California in 2010 and was deployed in late 2011 to the Atacama Desert in Chile. An overview of the instrument is presented along with characterization results from observations in Chile.
The bolometric focal plane array of the POLARBEAR CMB experiment
Show abstract
The POLARBEAR Cosmic Microwave Background (CMB) polarization experiment is currently observing from the Atacama Desert in Northern Chile. It will characterize the expected B-mode polarization due to gravitational lensing of the CMB, and search for the possible B-mode signature of inflationary gravitational waves. Its 250 mK focal plane detector array consists of 1,274 polarization-sensitive antenna-coupled bolometers, each with an associated lithographed band-defining filter. Each detector’s planar antenna structure is coupled to the telescope’s optical system through a contacting dielectric lenslet, an architecture unique in current CMB experiments. We present the initial characterization of this focal plane.
CMB Instrumentation: New Developments I
SPTpol: an instrument for CMB polarization measurements with the South Pole Telescope
Show abstract
SPTpol is a dual-frequency polarization-sensitive camera that was deployed on the 10-meter South Pole Telescope in January 2012. SPTpol will measure the polarization anisotropy of the cosmic microwave background (CMB) on angular scales spanning an arcminute to several degrees. The polarization sensitivity of SPTpol will enable a detection of the CMB “B-mode” polarization from the detection of the gravitational lensing of the CMB by large scale structure, and a detection or improved upper limit on a primordial signal due to inationary gravity waves. The two measurements can be used to constrain the sum of the neutrino masses and the energy scale of ination. These science goals can be achieved through the polarization sensitivity of the SPTpol camera and careful control of systematics. The SPTpol camera consists of 768 pixels, each containing two transition-edge sensor (TES) bolometers coupled to orthogonal polarizations, and a total of 1536 bolometers. The pixels are sensitive to light in one of two frequency bands centered at 90 and 150 GHz, with 180 pixels at 90 GHz and 588 pixels at 150 GHz. The SPTpol design has several features designed to control polarization systematics, including: singlemoded feedhorns with low cross-polarization, bolometer pairs well-matched to dfference atmospheric signals, an improved ground shield design based on far-sidelobe measurements of the SPT, and a small beam to reduce temperature to polarization leakage. We present an overview of the SPTpol instrument design, project status, and science projections.
Performance and on-sky optical characterization of the SPTpol instrument
Show abstract
In January 2012, the 10m South Pole Telescope (SPT) was equipped with a polarization-sensitive camera, SPTpol, in order to measure the polarization anisotropy of the cosmic microwave background (CMB). Measurements of the polarization of the CMB at small angular scales (~several arcminutes) can detect the gravitational lensing of the CMB by large scale structure and constrain the sum of the neutrino masses. At large angular scales (~few degrees) CMB measurements can constrain the energy scale of Inflation. SPTpol is a two-color mm-wave camera that consists of 180 polarimeters at 90 GHz and 588 polarimeters at 150 GHz, with each polarimeter consisting of a dual transition edge sensor (TES) bolometers. The full complement of 150 GHz detectors consists of 7 arrays of 84 ortho-mode transducers (OMTs) that are stripline coupled to two TES detectors per OMT, developed by the TRUCE collaboration and fabricated at NIST. Each 90 GHz pixel consists of two antenna-coupled absorbers coupled to two TES detectors, developed with Argonne National Labs. The 1536 total detectors are read out with digital frequency-domain multiplexing (DfMUX). The SPTpol deployment represents the first on-sky tests of both of these detector technologies, and is one of the first deployed instruments using DfMUX readout technology. We present the details of the design, commissioning, deployment, on-sky optical characterization and detector performance of the complete SPTpol focal plane.
Antenna-coupled TES bolometers for the Keck array, Spider, and Polar-1
Show abstract
Between the BICEP2 and Keck Array experiments, we have deployed over 1500 dual polarized antenna coupled bolometers
to map the Cosmic Microwave Background’s polarization. We have been able to rapidly deploy these detectors because
they are completely planar with an integrated phased-array antenna. Through our experience in these experiments, we
have learned of several challenges with this technology- specifically the beam synthesis in the antenna- and in this paper
we report on how we have modified our designs to mitigate these challenges. In particular, we discus differential steering
errors between the polarization pairs’ beam centroids due to microstrip cross talk and gradients of penetration depth in the
niobium thin films of our millimeter wave circuits. We also discuss how we have suppressed side lobe response with a
Gaussian taper of our antenna illumination pattern. These improvements will be used in Spider, Polar-1, and this season’s
retrofit of Keck Array.
The POLARBEAR-2 experiment
Show abstract
POLARBEAR-2 (PB-2) is a cosmic microwave background (CMB) polarization experiment observing at Atacama plateau in Chile. PB-2 is designed to improve the sensitivity to measure the CMB B-mode polarization by upgrading the current POLARBEAR-1 receiver that is currently mounted on the Huan Tran telescope. The improvements in PB-2 include, i) the dual band observations at 95 GHz and 150 GHz in each pixel using an sinuous antenna, ii) the increase of the total number of detectors, 7588 Al-Ti bilayer transition-edge sensor (TES) bolometers, iii) the bath temperature of bolometers at 100mK in the second phase of observation (300mK in the first phase.) With the expected sensitivity of 5.7 μK √ s, PB-2 is sensitive to a tensor-to-scalar ratio, r, of 0.01 at 95% confidence level (CL) and constrains the sum of neutrino masses as 90meV by PB-2 alone and 40meV by combining PB-2 and Planck at 68% CL. We schedule to deploy in 2014.
CMB Instrumentation: New Developments II
The Primordial Inflation Polarization Explorer (PIPER)
Show abstract
The Primordial Inflation Polarization Explorer (PIPER) is a balloon-borne instrument to measure the gravitational wave signature of primordial inflation through its distinctive imprint on the polarization of the cosmic microwave background. PIPER combines cold (1.5 K) optics, 5120 bolometric detectors, and rapid polarization modulation using VPM grids to achieve both high sensitivity and excellent control of systematic errors. A series of flights alternating between northern and southern hemisphere launch sites will produce maps in Stokes I, Q, U, and V parameters at frequencies 200, 270, 350, and 600 GHz (wavelengths 1500, 1100, 850, and 500 μm) covering 85% of the sky. The high sky coverage allows measurement of the primordial B-mode signal in the `reionization bump" at multipole moments l < 10 where the primordial signal may best be distinguished from the cosmological lensing foreground. We describe the PIPER instrument and discuss the current status and expected science returns from the mission.
MuSE: a novel experiment for CMB polarization measurement using highly multimoded bolometers
Show abstract
One of the most exciting targets for cosmic microwave background (CMB) polarization measurements is the faint signal from the primordial gravity waves predicted by inflationary models. Currently existing experiments and those under construction would constrain or detect such a signal at around r = 0.01, where r is the tensor to scalar ratio. In order to further improve the measurement, experiments for the next generation have to combine the following three: 1) excellent sensitivity, 2) multi-frequency measurement for the removal of galactic foregrounds, and 3) well-controlled systematics. We propose the Multimoded Survey Experiment (MuSE), which uses highly multimoded polarization-sensitive bolometers developed at NASA Goddard Space Flight Center (GSFC). MuSE, consisting of 69 pixels, will achieve a sensitivity equivalent to several thousand single-moded bolometers. Each pixel can be configured to be sensitive to a different frequency band, allowing very wide frequency coverage by a single focal plane. This enables us to clean galactic synchrotron and dust components with our data alone. MuSE achieves an effective array sensitivity to the CMB of 8 μK√s even after accounting for the sensitivity degradation from foreground removal and reaches a 2-σ error on r of 0.009 with two years of operation.
GroundBIRD: an experiment for CMB polarization measurements at a large angular scale from the ground
Show abstract
Odd-parity patterns in the cosmic microwave background (CMB) polarization, B-modes, could provide important cosmological information. Detection of the primordial B-mode power at a large angular scale would be a smoking gun signature of the inflationary universe. In particular, detecting a reionization bump (at a multipole of ≤ 10) should be a clear evidence of it. GroundBIRD is designed to detect the B-mode signal at this large angular scale from the ground. We will use superconducting detector arrays with small telescope that will also be cooled down to 4K. Therefore, the basic design can be extended to a satellite experiment. GroundBIRD employs a high-speed (20 rpm) rotation scan instead of the usual left–right azimuthal scan; this allows us to maintain a high-speed scan without any deceleration, resulting in a significant expansion of the scan range to 60° without any effect of the detector 1/f noise. Our target is measuring the CMB polarization power in a multipole (l) range of 6 ≤ l ≤ 300. We plan to start commissioning the instruments in Japan in early 2014; they will then be moved to the Atacama Desert in Chile for scientific observations.
Detector architecture of the cosmology large angular scale surveyor
Show abstract
The cosmic microwave background (CMB) provides a powerful tool for testing modern cosmology. In particular, if inflation has occurred, the associated gravitational waves would have imprinted a specific polarized pattern on the CMB. Measurement of this faint polarized signature requires large arrays of polarization-sensitive, background- limited detectors, and an unprecedented control over systematic effects associated with instrument design. To this end, the ground-based Cosmology Large Angular Scale Surveyor (CLASS) employs large-format, feedhorn- coupled, background-limited Transition-Edge Sensor (TES) bolometer arrays operating at 40, 90, and 150 GHz bands. The detector architecture has several enabling technologies. An on-chip symmetric planar orthomode transducer (OMT) is employed that allows for highly symmetric beams and low cross-polarization over a wide bandwidth. Furthermore, the quarter-wave backshort of the OMT is integrated using an innovative indium bump bonding process at the chip level that ensures minimum loss, maximum repeatability and performance uniformity across an array. Care has been taken to reduce stray light and on-chip leakage. In this paper, we report on the architecture and performance of the first prototype detectors for the 40 GHz focal plane.
Mechanical Design and Cryogenics
Millikelvin cryocooler for space- and ground-based detector systems
Show abstract
This paper describes the design of a continuously operating millikelvin cryocooler (mKCC) and its origins. It takes
heritage from the double adiabatic demagnetization refrigerator (dADR) which was built for the European Space Agency
(ESA). The compact design is based on a tandem configuration continuous ADR which alternately cycles two dADRs.
The mKCC is a single module (dimensions 355 x 56 x120 mm) which operates from a 4 K bath (liquid or cryocooler)
and provides an interface to the user which is settable from < 100 mK to 4 K. Predicted maximum cooling power at 100
mK is 7μW. It will use only single crystal tungsten magnetoresistive heat switches (the first ADR cooler to do so) and
the measured thermal performance of these heat switches is presented. The mKCC uses ten shielded 2 Tesla
superconducting magnets capable of ramping to full field in 20 – 30 seconds. This has been demonstrated in the lab and
the results are given for the successful performance of a prototype Chromium Potassium Alum (CPA) pill using one of
these magnets. The mKCC has been designed to be fully automated and user friendly with the aim of expanding the use
of millikelvin cryogenics and providing a good testing and operating platform for detector systems.
Thermal architecture of the SPICA/SAFARI instrument
Show abstract
The SAFARI instrument is a far infrared imaging spectrometer that is a core instrument of the SPICA mission. Thanks to the large (3 meter) SPICA cold telescope, the ultra sensitive detectors and a powerful Fourier Transform Spectrometer, this instrument will give access to the faintest light never observed in the 34 μm - 210 μm bandwidth with a high spectral resolution. To achieve this goal, TES detectors, that need to be cooled at a temperature as low as 50 mK, have been chosen. The thermal architecture of the SAFARI focal plane unit (FPU) which fulfils the TES detector thermal requirements is presented. In particular, an original 50 mK cooler concept based on a sorption cooler in series with an adiabatic demagnetization refrigerator will be used. The thermal design of the detector focal plane array (FPA) that uses three temperature stages to limit the loads on the lowest temperature stage, will be also described. The current SAFARI thermal budget estimations are presented and discussed regarding the limited SPICA allocations. Finally, preliminary thermal sensitivity analysis dealing with thermal stability requirements is presented.
The optical, mechanical, and thermal design and performance of the 2nd generation redshift (z) and early universe spectrometer, ZEUS-2
Show abstract
We have built a new long-slit grating spectrometer (ZEUS-2) for observations in the submillimeter wavelength regime (200-650 μm). ZEUS-2 is optimized for observations of redshifted far-infrared spectral lines from galaxies in the early Universe. The spectrometer employs three transition-edge sensed bolometer arrays, allowing for simultaneous observations of multiple lines in several telluric windows. Here we will discuss the optical, mechanical, and thermal requirements of ZEUS-2 and their subsequent design and performance. The entire instrument is cooled using a pulse tube cryocooler and an adiabatic demagnetization refrigerator. The cryogen-free approach enables remote control of the cooling system and allows for deployment of ZEUS-2 to telescope sites where access is limited. The compact and lightweight design is also within the size and weight constraints of several submm telescopes, making ZEUS-2 deployable at a variety of sites. ZEUS-2 completed a successful engineering run at the CSO on Mauna Kea in May 2012, and we plan to have our science-grade array system deployed on the APEX telescope in Chile for a science run in the fall of 2012.
Poster Session
POLOCAM: a millimeter wavelength cryogenic polarimeter prototype for MUSIC-POL
Show abstract
As a proof-of-concept, we have constructed and tested a cryogenic polarimeter in the laboratory as a prototype
for the MUSIC instrument (Multiwavelength Sub/millimeter Kinetic Inductance Camera). The POLOCAM
instrument consists of a rotating cryogenic polarization modulator (sapphire half-waveplate) and polarization
analyzer (lithographed copper polarizers deposited on a thin film) placed into the optical path at the Lyot stop
(4K cold pupil stop) in a cryogenic dewar. We present an overview of the project, design and performance
results of the POLOCAM instrument (including polarization efficiencies and instrumental polarization), as well
as future application to the MUSIC-POL instrument.
BoA: a versatile software for bolometer data reduction
Show abstract
Together with the development of the Large APEX Bolometer Camera (LABOCA) for the Atacama Pathfinder
Experiment (APEX), a new data reduction package has been written. This software naturally interfaces with
the telescope control system, and provides all functionalities for the reduction, analysis and visualization of
bolometer data. It is used at APEX for real time processing of observations performed with LABOCA and other
bolometer arrays, providing feedback to the observer. Written in an easy-to-script language, BoA is also used
offline to reduce APEX continuum data. In this paper, the general structure of this software is presented, and
its online and offline capabilities are described.
Development of a low background test facility for the SPICA-SAFARI on-ground calibration
Show abstract
SAFARI is a far-infrared camera to be launched in 2021 onboard the SPICA satellite. SAFARI offers imaging
spectroscopy and imaging photometry in the wavelength range of 34 to 210 μm with detector NEP of 2•10-19 W/√Hz.
A cryogenic test facility for SAFARI on-ground calibration and characterization is being developed. The main design
driver is the required low background of a few attoWatts per pixel. This prohibits optical access to room temperature and
hence all test equipment needs to be inside the cryostat at 4.5K. The instrument parameters to be verified are interfaces
with the SPICA satellite, sensitivity, alignment, image quality, spectral response, frequency calibration, and point spread
function. The instrument sensitivity is calibrated by a calibration source providing a spatially homogeneous signal at the
attoWatt level. This low light intensity is achieved by geometrical dilution of a 150K source to an integrating sphere. The
beam quality and point spread function is measured by a pinhole/mask plate wheel, back-illuminated by a second
integrating sphere. This sphere is fed by a stable wide-band source, providing spectral lines via a cryogenic etalon.
The DCU: the detector control unit of the SAFARI instrument onboard SPICA
Show abstract
The SpicA FAR infrared Instrument (SAFARI) is a European instrument for the infrared domain telescope SPICA, a
JAXA space mission. The SAFARI detectors are Transistor Edge Sensors (TES) arranged in 3 matrixes. The TES front
end electronic is based on Superconducting Quantum Interference Devices (SQUIDs) and it does the readout of the
3500 detectors with Frequency Division Multiplexing (FDM) type architecture. The Detector Control Unit (DCU),
contributed by IRAP, manages the readout of the TES by computing and providing the AC-bias signals (1 - 3 MHz) to
the TES and by computing the demodulation of the returning signals. The SQUID being highly non-linear, the DCU has
also to provide a feedback signal to increase the SQUID dynamic. Because of the propagation delay in the cables and the
processing time, a classic feedback will not be stable for AC-bias frequencies up to 3 MHz. The DCU uses a specific
technique
to compensate for those delays: the BaseBand FeedBack (BBFB). This digital data processing is done for the 3500 pixels
in parallel. Thus, to keep the DCU power budget within its allocation we have to specifically optimize the architecture of
the digital circuit with respect to the power consumption. In this paper we will mainly present the DCU architecture. We
will particularly focus on the BBFB technique used to linearize the SQUID and on the optimization done to reduce the
power consumption of the digital processing circuit.
A generic readout system for astrophysical detectors
E. Doumayrou,
M. Lortholary
Show abstract
We have developed a generic digital platform to fulfill the needs for the development of new detectors in
astrophysics, which is used in lab, for ground-based telescopes instruments and also in prototype versions for space
instruments development.
This system is based on hardware FPGA electronic board (called MISE) together with software on a PC
computer (called BEAR). The MISE board generates the fast clocking which reads the detectors thanks to a
programmable digital sequencer and performs data acquisition, buffering of digitalized pixels outputs and interfaces
with others boards. The data are then sent to the PC via a SpaceWire or Usb link. The BEAR software sets the MISE
board up, makes data acquisition and enables the visualization, processing and the storage of data in line. These
software tools are made of C++ and Labview (NI) on a Linux OS.
MISE and BEAR make a generic acquisition architecture, on which dedicated analog boards are plugged, so that to
accommodate with detectors specificity: number of pixels, the readout channels and frequency, analog bias and clock
interfaces.
We have used this concept to build a camera for the P-ARTEMIS project including a 256 pixels sub-millimeter
bolometer detector at 10Kpixel/s (SPIE 7741-12 (2010)). For the EUCLID project, a lab camera is now working for the
test of CCDs 4Mpixels at 4*200Kpixel/s. Another is working for the testing of new near infrared detectors (NIR LFSA
for the ESA TRP program) 110Kpixels at 2*100Kpixels/s. Other projects are in progress for the space missions PLATO
and SPICA.
Phase-controlled polarization modulators
Show abstract
We report technology development of millimeter/submillimeter polarization modulators that operate by introducing a variable, controlled phase delay between two orthogonal polarization states. The variable-delay polarization modulator (VPM) operates via the introduction of a variable phase delay between two linear orthogonal polarization states, resulting in a variable mapping of a single linear polarization into a combination of that Stokes parameter and circular (Stokes V) polarization. Characterization of a prototype VPM is presented at 350 and 3000 microns. We also describe a modulator in which a variable phase delay is introduced between right- and left- circular polarization states. In this architecture, linear polarization is fully modulated. Each of these devices consists of a polarization diplexer parallel to and in front of a movable mirror. Modulation involves sub-wavelength translations of the mirror that change the magnitude of the phase delay.
Water vapour radiometers for the Australia telescope compact array
Show abstract
We have developed Water Vapour Radiometers (WVRs) for the Australia Telescope Compact Array that are capable of determining excess path fluctuations by virtue of measuring small temperature fluctuations in the atmosphere using the 22.3 GHz water vapour line for each of the six antennae. By measuring the line of sight variations of the water vapour, the induced path excess and thus the phase delay can be estimated and corrections can then be applied during data reduction. This reduces decorrelation of the source signal. In this presentation, we discuss the design of the WVRs, an uncooled quadruple filter radiometer capable of detecting water line temperature fluctuations to a sensitivity of 12 mK. The design process of the WVRs is discussed with an emphasis on the modelled sensitivity requirements, filter placement, radio frequency interference mitigation and we conclude by demonstrating how this water vapour radiometry system recovers the telescope's efficiency and image quality as well as how this improves the telescope's ability to use longer baselines at higher frequencies, thereby resulting in higher spatial resolution. We discuss a quadruple filter, uncooled 22.2 GHz Water Vapour Radiometer (WVR) system developed for the six antennae of the Australia Telescope Compact Array. The design process of the WVRs is discussed with an emphasis on the modelled sensitivity requirements, filter placement, radio frequency interference mitigation and we conclude by demonstrating how this system recovers the telescope's efficiency and image quality as well as how this improves the telescope's ability to use longer baselines at higher frequencies, thereby resulting in higher spatial resolution.
The cosmology large angular scale surveyor (CLASS): 40 GHz optical design
Show abstract
The Cosmology Large Angular Scale Surveyor (CLASS) instrument will measure the polarization of the cosmic microwave background at 40, 90, and 150 GHz from Cerro Toco in the Atacama desert of northern Chile. In this paper, we describe the optical design of the 40 GHz telescope system. The telescope is a diffraction limited catadioptric design consisting of a front-end Variable-delay Polarization Modulator (VPM), two ambient temperature mirrors, two cryogenic dielectric lenses, thermal blocking filters, and an array of 36 smooth-wall scalar feedhorn antennas. The feed horns guide the signal to antenna-coupled transition-edge sensor (TES) bolometers. Polarization diplexing and bandpass definition are handled on the same microchip as the TES. The feed horn beams are truncated with 10 dB edge taper by a 4 K Lyot-stop to limit detector loading from stray light and control the edge illumination of the front-end VPM. The field-of-view is 19° x 14° with a resolution for each beam on the sky of 1.5° FWHM.
ALMA nutator design and preliminary performances
Show abstract
We report the past two years of collaboration between the different actors on the ALMA nutator. Building on previous developments, the nutator has seen changes in much of the design. A high-modulus carbon fiber structure has been added on the back of the mirror in order to transfer the voice coils forces with less deformation, thus reducing delay problems due to flexing. The controller is now an off-the-shelf National Instrument NI-cRIO, and the amplifier a class D servo drive from Advanced Motion Controls, with high peak power able to drive the coils at 300 Volts DC. The stow mechanism has been totally redesigned to improve on the repeatability and precision of the stow position, which is also the reference for the 26 bits Heidenhain encoders. This also improves on the accuracy of the stow position with wind loading. Finally, the software, written largely with National Instrument's LabView, has been developed. We will discuss these changes and the preliminary performance achieved to date.
Mirror illumination and spillover measurements of the Atacama Cosmology Telescope
Show abstract
The Atacama Cosmology Telescope (ACT) is a 6 m telescope designed to map the Cosmic Microwave Background
(CMB) simultaneously at 145 GHz, 220 GHz and 280GHz. The receiver in ACT, the Millimeter Bolometer Array
Camera, features 1000 TES bolometers in each band. The detector performance depends critically on the total
optical loading, requiring the spillover contributions from the optics to be minimal. This inspired the use of
a cold Lyot stop to limit the illumination of the primary and the use of guard rings surrounding the primary
and secondary reflectors. Here, we present a direct measurement of the illumination aperture for both reflectors
and of the attenuation level outside the main optical path. We used a 145 GHz, 1mW source and a chopper
wheel to produce a time-varying signal with a broad beam profile. We sampled the response of the camera for
different locations of the source, placed in front and beside the primary and secondary mirrors. The aperture
of the primary was measured to be 5.72 ± 0.17m in diameter (95 ± 3% of its geometrical size), while the
aperture of the secondary yielded 2 ± 0.12m in diameter. Both apertures are consistent with the optical design.
Comparing to previous measurements of the beam solid angle from planet observations, we estimate an optical
efficiency of 72.3 ± 4.8%. We found that the attenuation outside the primary aperture was −16 ± 2 dB, which
is below the theoretical expectations, and −22 ± 1 dB outside the secondary aperture, which is consistent with
simulations. These results motivated the extension of the baffles surrounding the secondary mirror, with the
following reduction in detector optical loading from 2.24pW to 1.88 pW.
Far sidelobes measurement of the Atacama Cosmology Telescope
Show abstract
The Atacama Cosmology Telescope (ACT) is a 6m telescope designed to map the Cosmic Microwave Background
(CMB) simultaneously at 145GHz, 220 GHz and 280 GHz. Its off-axis Gregorian design is intended to minimize
and control the off-axis sidelobe response, which is critical for scientific purposes. The expected sidelobe level for
this kind of design is less than -50 dB and can be challenging to measure. Here we present a measurement of the
145GHz far sidelobes of ACT done on the near-field of the telescope. We used a 1mW microwave source placed
13 meters away from the telescope and a chopper wheel to produce a varying signal that could be detected by the
camera for different orientations of the telescope. The source feed was designed to produce a wide beam profile.
Given that the coupling is expected to be dominated by diffraction over the telescope shielding structure, when
combined with a measurements of the main beam far field response, these measurement can be used to validate
elements of optical design and constrain the level of spurious coupling at large angles. Our results show that the
diffractive coupling beyond the ground screen is consistently below -75 dB, satisfying the design expectations.
Optical characterization of the Keck array polarimeter at the South Pole
Show abstract
The Keck Array (SPUD) is a set of microwave polarimeters that observes from the South Pole at degree angular scales in search of a signature of Inflation imprinted as B-mode polarization in the Cosmic Microwave Background (CMB). The first three Keck Array receivers were deployed during the 2010-2011 Austral summer, followed by two new receivers in the 2011-2012 summer season, completing the full five-receiver array. All five receivers are currently observing at 150 GHz. The Keck Array employs the field-proven BICEP/ BICEP2 strategy of using small, cold, on-axis refractive optics, providing excellent control of systematics while maintaining a large field of view. This design allows for full characterization of far-field optical performance using microwave sources on the ground. We describe our efforts to characterize the main beam shape and beam shape mismatch between co-located orthogonally-polarized detector pairs, and discuss the implications of measured differential beam parameters on temperature to polarization leakage in CMB analysis.
Experimental performance comparison of two polarimeter techniques for CMB applications
Show abstract
Polarisation modulators are necessary for present and next generations of CMB polarisation experiments. Because of the
very faint B-mode signal expected, these instruments have not only to be extremely sensitive but also to have low and
well-characterised systematic effects.
The beam RF characterisation in the W-band (75-110 GHz) of two polarimeter pixels using the same corrugated horn has
been performed using two different modulators: a waveguide rotator modulator and a quasi-optical half-wave plate. Coand
cross-polarisation beam measurements are presented together with the systematic effects introduced by both
modulators.
A negative refractive index metamaterial wave plate for millimetre-wave applications
Show abstract
By use of a metamaterial based on the ‘cut wire pair’ geometry, highly birefringent wave plates may be constructed by virtue of the geometry’s ability of having a negative and positive refractive index along its perpendicular axes. Past implementations have been narrow band in nature due to the reliance on producing a resonance to achieve a negative refractive index band and the steep gradient in the phase difference that results. In this paper we attempt to design and manufacture a W-band quarter wave plate embedded in polypropylene that applies the Pancharatnam method to increase the useable bandwidth. Our modelling demonstrates that a broadening of the phase difference’s bandwidth defined as the region 90° ± 2° is possible from 0.6% (101.7 GHz – 102.3 GHz) to 7.8% (86.2 GHz – 93.1 GHz). Our experimental results show some agreement with our modelling but differ at higher frequencies.
The optical design of the QUBIC beam combiner
Show abstract
The Q and U Bolometric Interferometer for Cosmology (QUBIC) is a ground-based interferometer that aims to meet one of the major challenges of modern cosmology in the detection of B-mode polarization anisotropies in the Cosmic Microwave Background.B-mode anisotropies originate from tensor fluctuations of the metric produced during the inflationary phase of the early Universe. Their detection would therefore constitute a major step towards understanding the primordial Universe. The expected level of these anisotropies is however so small that detection requires instruments with high sensitivity and extremely good control of systematic effects. The QUBIC instrument is based on the novel concept of bolometric interferometry, and exploits the sensitivity advantages of bolometric detectors along with the greater control of systematics offered by interferometry.The instrument will directly observe the sky through an array of entry horns whose signals will be combined optically onto an array of bolometers cooled to around 300mK. The whole set-up is located inside a cryostat. The sensitivity of the instrument is maximised if equivalent baselines produce identical fringe patterns on the focal plane. This requires the minimization of wavefront aberrations for a wide field-of-view and a fast system.In this poster we present the quasi-optical design and analysis of the dual reflector designed to do this. We report on the loss of sensitivity for different levels of optical aberration in the combiner. The sensitivity of the QUBIC instrument is comparable with that of an imager with the same number of horns but with much greater control over systematics.
Development of the test interferometer for ALMA
Show abstract
The ALMA Test Interferometer appeared as an infrastructure solution to increase both ALMA time availability for science activities and time availability for Software testing and Engineering activities at a reduced cost (<30000K USD) and a low setup time of less than 1 hour. The Test Interferometer could include up to 16 Antennas when used with only AOS resources and a possible maximum of 4 Antennas when configured using Correlator resources at OSF. A joined effort between ADC and ADE-IG took the challenge of generate the Test Interferometer from an already defined design for operations which imposed a lot of complex restrictions on how to implement it. Through and intensive design and evaluation work it was determined that is possible to make an initial implementation using the ACA Correlator and now it is also being tested the feasibility to implement the Testing Interferometer connecting the Test Array at AOS with Correlator equipment installed at the OSF, separated by 30 km. app. Lastly, efforts will be done to get interferometry between AOS and OSF Antennas with a baseline of approximately 24 km.
Recent advances in the development of SWIFTS for broadband millimeter spectroscopy
Show abstract
We present latest developments of the millimetric Stationary Waves Integrated Fourier Transform Spectrometer
(SWIFTS) that uses the Kinetic Inductance Detectors (KID) technology. SWIFTs are on-chip autocorrelator
spectrometers where the incoming signal forms an interferogram by reflection in a short-circuited coplanar wave-guide.
By collecting electromagnetic (EM) energy along the guide, one can retrieve this interference pattern. A subsequent offline
Fourier transform gives spectral information with a moderate resolution (~500-1000). SWIFTS concept has already
been proven to work in the optical and microwave (<20 GHz) bands. It will be useful in any application where integrated
and broadband spectral analysis is needed, as an example it will be a practical alternative to Martin-Pupplet
interferometer. In practice, fabrication of such a device is very challenging mostly because the set of detectors has to
collect energy without destroying the interference pattern. As a consequence, design of the coupling parts is a crucial
problem that has to be tackled with the help of EM simulation tools. We present here the SWIFTS principle of operation,
details of fabrication, and the latest simulations results.
A 3mm multipixel SIS receiver for IRAM 30-m Pico Veleta Telescope
Anne-Laure Fontana,
Catherine Boucher,
Patrice Serres,
et al.
Show abstract
A 3mm band focal plane array heterodyne receiver is being developed for Nasmyth focus of the IRAM 30-m Pico Veleta
Radio Telescope located in the Sierra Nevada Mountains, south of Spain. This receiver will comprise 25 dual linear
polarization pixels operating across the 80-116GHz nominal band. Design efforts are being made to enlarge the band to
cover the full 3mm atmospheric transmission window available at Pico Veleta, i.e. 72-116GHz. The instrument will be
coupled to the Pico Veleta Telescope via a purely reflective low-loss optical system that includes a de-rotator. The
receiver will be based on 5 x 5 cryogenically cooled dual-linear polarized feed horns cascaded with Ortho Mode
Transducers (OMT) and side band separating SIS mixers, a technology which offers state-of-the-art performances for
millimeter and sub-millimeter receivers.
Electromagnetic design for SuperSpec: a lithographically-patterned millimetre-wave spectrograph
Show abstract
SuperSpec is an innovative, fully planar, compact spectrograph for mm/sub-mm astronomy. SuperSpec is based on a superconducting filter-bank consisting of a series of planar half-wavelength filters to divide up the incoming, broadband radiation. The power in each filter is then coupled into titanium nitride lumped element kinetic inductance detectors, facilitating the read out of a large number of filter elements. We will present electromagnetic simulations of the different components that will make up an R = 700 prototype instrument. Based on these simulations, we discuss optimisation of the coupling between the antenna, transmission line, filters and detectors.
SuperSpec: design concept and circuit simulations
Show abstract
SuperSpec is a pathfinder for future lithographic spectrometer cameras, which promise to energize extra-galactic astrophysics at (sub)millimeter wavelengths: delivering 200–500 kms-1 spectral velocity resolution over an octave bandwidth for every pixel in a telescope’s field of view. We present circuit simulations that prove the concept, which enables complete millimeter-band spectrometer devices in just a few square-millimeter footprint. We evaluate both single-stage and two-stage channelizing filter designs, which separate channels into an array of broad-band detectors, such as bolometers or kinetic inductance detector (KID) devices. We discuss to what degree losses (by radiation or by absorption in the dielectric) and fabrication tolerances affect the resolution or performance of such devices, and what steps we can take to mitigate the degradation. Such design studies help us formulate critical requirements on the materials and fabrication process, and help understand what practical limits currently exist to the capabilities these devices can deliver today or over the next few years.
Optimized sensitivity and beam pattern of a twin-slot antenna coupled NbN HEB mixer at 1.6THz
Show abstract
We report on a twin-slot antenna coupled superconducting NbN hot electron bolometer (HEB) mixer designed for 1.6
THz. Terahertz (THz) radiation is quasi-optically coupled to the HEB with an uncoated elliptical Si lens. Measured DSB
receiver noise temperatures are 1500 K at 0.85 THz, 1200 K at 1.27 THz, 1100 K at 1.31 THz, 1100 K at 1.4 THz, and
1000 K at 1.63 THz. This value at 1.63 THz is reduced to 750 K when the hot/cold loads in vacuum are used. The
frequency dependence of the noise temperature is consistent with the measured FTS spectral response. The measured farfield
beam patterns of the lens/antenna combination show nearly collimated beams with the side lobes below -16dB by
adding a 40 μm extension to a standard Si elliptical lens design, which is understood by considering a slightly lower
dielectric constant of Si (εSi) of 11.4 instead of 11.7. The good performance of such NbN HEB mixers makes it suitable
for future high-resolution spectroscopic astronomical applications.
Vertically illuminated TW-UTC photodiodes for terahertz generation
Show abstract
More efficient and powerful continuous-wave photonic mixers as terahertz sources are motivated by the need of more versatile local oscillators for submillimeter/terahertz receiver systems. Uni-Travelling Carrier (UTC) photodiodes are very prospective candidates for reaching this objective, but so far only have been reported as lumped-elements or as edge-illuminated optical-waveguide travelling-wave (TW) devices. To overcome the associated power limitations of those implementations, we are developing a novel implementation of the UTC photodiodes which combines a travelingwave photomixer with vertical velocity-matched illumination in a distributed structure. In this implementation called velocity-matched travelling-wave uni-travelling carrier photodiode, it is possible to obtain in-situ velocity matching of the beat-fringes of the two angled laser beams with the submm/THz-wave on the stripline. In this way, minimum frequency roll-off is achieved by tuning the angle between the two laser beams. A first design of these TW-UTC PDs from our Terahertz Photonics Laboratory at University of Chile has been micro-fabricated at the MC2 cleanroom facility at Chalmers Technical University.
A 4mm spectroscopic dual-beam receiver for the Robert C. Byrd green bank radio telescope
Show abstract
With a 100-meter aperture, and recent improvements to its surface accuracy and servo system upgrades, the Robert C.
Byrd Green Bank Telescope is the most sensitive telescope operating at 90 GHz. A dual-feed heterodyne receiver is
developed for observations at the lower frequency end of the 3-4mm atmospheric window (67 to 93 GHz). The science
goals are primarily molecular spectroscopic studies of star formation and astrochemistry both internal and external to the
Milky Way galaxy. Studies of the structural and physical properties of star-forming, cold-cloud cores will be
revolutionized with molecular spectroscopy of the deuterium and other important species within the band. Essential for
spectroscopy is the ability to remove slow gain and atmospheric variations. An optical table external to the cooled
components rotates into the path of either beam an ambient temperature load, an offset mirror for viewing an internal
cold load, or a quarter-wave plate that produces circular polarization for VLBI observations. A composite waveguide
window comprised of HDPE, Zitex, and z-cut quartz provides a high-strength, low-loss medium for transmission of the
signal to the cooled corrugated feed horn. An orthomode transducer separates the polarization components which are
amplified by low noise HEMT amplifiers. Warm W-band MMIC amplifiers are required to compensate a negative gain
slope and to reduce noise contributions from the down conversion to the GBT IF frequencies. Initial science results and
receiver performance during commissioning observations will be presented along with details of the component design.
Cryogenic analog-to-digital converters using spread spectrum technology for coherent receivers
Show abstract
We propose analog-to-digital converters (ADCs) using spread spectrum technology in cryogenic receivers or at warm
room temperature for coherent receiver backend systems. As receiver signals are processed and stored digitally, ADCs
play a critical role in backend read-out systems. To minimize signal distortion, the down-converted signals should be
digitized without further transportation. However, digitizing the signals in or near receivers may cause radio frequency
interference. We suggest that spread spectrum technology can reduce the interference significantly. Moreover, cryogenic
ADCs at regulated temperature in receiver dewars may also increase the bandwidth usage and simplify the backend
digital signal process with fewer temperature-dependant components. While industrial semiconductor technology
continuously reduces transistor power consumption, low power high speed cryogenic ADCs may become a better
solution for coherent receivers. To examine the performance of cooled ADCs, first, we design 4 bit 65 nm and 40 nm
CMOS ADCs specifically at 10 K temperature, which commonly is the second stage temperature in dewars. While the
development of 65 nm and 40 nm CMOS ADCs are still on-going, we estimate the ENOB is 2.4 at 10 GSPS,
corresponding to the correlation efficiency, 0.87. The power consumption is less than 20 mW.
A 4 GHz digital receiver using the Uniboard platform
Giovanni Comoretto,
Antonietta Russo,
Benjamin Quertier,
et al.
Show abstract
The Uniboard is a general purpose board, developed as a part of the Radionet FP7 program, that hosts 8 Altera
StratixIV FPGAs interconnected by high speed links. It can be used standalone or as a part of a more complex
system.
The Digital receiver application uses a single Uniboard to implement a flexible packetization of a wideband
signal in the frequency domain. It accepts a 4 GHz (8 GS/s) input bandwidth and provides up to 64 output
bands. The bandwidth and position of each output band can be independently adjusted.
The input signal is first analyzed by a polyphase filterbank, that splits the input band into 32 sub-bands with
a bandwidth of 190 MHz and a spacing of 128 MHz. The overlap among adjacent bands allows the positioning of
the output bands without dead regions. This filterbank is followed by an array of digitally defined downconverters,
each one composed of a mixer/LO and a variable decimation filter. The filter band can be adjusted in binary
steps from 1 to 128 MHz. Using tap recirculation, the filter shape remains constant over this whole range, with
about 60 dB of stopband rejection and 90% usable passband.
The output bands are packetized according to the VDIF VLBI standard, over eight 10G Ethernet links.
Further processing can be done either on board, or in a cluster of conventional PCs.
In addition, high speed ADC are in-house developed (ASIC 65nm CMOS STmicroelectronics) to feed the
Uniboard card with 8GS/s, 4GHz BW, 3bits samples.
UniBoard: generic hardware for radio astronomy signal processing
J. E. Hargreaves
Show abstract
UniBoard is a generic high-performance computing platform for radio astronomy, developed as a Joint Research
Activity in the RadioNet FP7 Programme. The hardware comprises eight Altera Stratix IV Field Programmable Gate
Arrays (FPGAs) interconnected by a high speed transceiver mesh. Each FPGA is connected to two DDR3 memory
modules and three external 10Gbps ports. In addition, a total of 128 low voltage differential input lines permit
connection to external ADC cards. The DSP capability of the board exceeds 644E9 complex multiply-accumulate
operations per second.
The first production run of eight boards was distributed to partners in The Netherlands, France, Italy, UK, China and
Korea in May 2011, with a further production runs completed in December 2011 and early 2012.
The function of the board is determined by the firmware loaded into its FPGAs. Current applications include
beamformers, correlators, digital receivers, RFI mitigation for pulsar astronomy, and pulsar gating and search machines
The new UniBoard based correlator for the European VLBI network (EVN) uses an FX architecture with half the
resources of the board devoted to station based processing: delay and phase correction and channelization, and half to the
correlation function. A single UniBoard can process a 64MHz band from 32 stations, 2 polarizations, sampled at 8 bit.
Adding more UniBoards can expand the total bandwidth of the correlator. The design is able to process both prerecorded
and real time (eVLBI) data.
Practical implementation and on the field test results of an enhanced algorithm for polarization optimization of the line length corrector of ALMA central local oscillator
Show abstract
This paper describes the practical implementation and on the field test results of an Enhanced algorithm, based on Jones matrix Eigen analysis, to find the minimal polarization change points for the ALMA's line length corrector fiber stretcher. These points are complicated to find because they can be located at any point of the Poincare sphere and they also change after manipulation of fibers and with time, so the optimization of the fibers stretcher needs to be systematically checked and redone. The execution time of the original algorithm takes up to 20 minutes depending on the starting polarization state. This enhanced algorithm reduces this time in most of cases to less than a minute, with no intrinsic dependency on the starting point.
ALMA band 1 development at Universidad de Chile
Nicolas Reyes,
Pablo Zorzi,
Claudio Jarufe,
et al.
Show abstract
The lowest spectroscopic band devised for the Atacama Large Millimeter Array (ALMA), the so-called Band 1,
covers the frequency range from 31 to 45 GHz. This band was not implemented during the rst construction
phase of the telescope, but will be included during a second ALMA development phase. During the past 4
years our group has been working on the development of technology to cover this band, complying with the
demanding ALMA specications. Among the most burdensome challenges are the stringent specications on
noise temperature, the large required bandwidth, and the limited space available for this receiver within the
ALMA cryostat. In this paper we present some of the technologies we have developed, including the design of
key components like horn, lens, ortho-mode transducer, and low noise ampliers. We also present an evaluation
of third-party components which can be used in the receiver. The work is used to present a preliminary layout
of the Band 1 receiver.
European low-noise MMIC technologies for cryogenic millimetre wave radio astronomical applications
Show abstract
The Low Noise technology has a paramount relevance on radiotelescopes and radiometers performances. Its influence on
sensitivity and temporal stability has a deep impact on obtainable scientific results. As well known, front end active part
of scientific instruments are cryocooled in order to drastically reduce the intrinsic thermal noise generated by its
electronic parts and consequently increase the sensitivity. In this paper we will describe the obtained results by an Italian
Space Agency funded activity. The aim is to validate European MMIC Low Noise technologies and designs for
cryogenic environments in the range of millimetre wave. As active device, HEMT (High Electron Mobility Transistor)
are considered the best device for high frequency and low noise cryo applications. But not all the semiconductor foundry
process are suitable for applications in such environment. Two European Foundries has been selected and two different
HEMT based Low Noise Amplifiers have been designed and produced. The main goal of this activity is identify an
European technology basement for space and ground based low noise cryogenic applications. Designs, layout,
architectures, foundry processes and results will be compared.
Development of receiver and local oscillator components for Atacama large millimeter/submillimeter array (ALMA) band-1 in Taiwan
Show abstract
A series of 31.3-45.0GHz millimeter-wave components including 31.3-45GHz low-noise amplifiers, band-pass and highpass
filters, a cascode PHEMT mixer, and 4-12GHz IF amplifiers are developed in Taiwan. The local oscillator for band-
1 is also developed, including the phase-locked GaAs HBT MMIC voltage-controlled oscillator cascaded by a buffer
amplifier and a baseline design based on a YIG-tunes oscillator with active frequency doubler. The measured RMS jitter
of the HBT VCO LO is around 51 fs and the version of YIG is less than 40fs over 1K to 1MHz frequency offset.
A cryogenic set-up for accurate measurements of S-parameters
Show abstract
We have developed a set-up to perform measurements of S-parameters on devices operated at low temperature,
using a Vector Network Analyzer in combination with a cryogenic chamber. High accuracy in the characterization
of the devices is obtained using a set of TRL calibration standards operated at the same cryogenic temperature of
the DUT. Measurements have been performed on Front-End-Modules of mm-wave receivers including cryogenic
LNA developed within our collaboration.
The wideband backend for host country radio astronomy in the Spanish DSN Robledo complex
J. R. Rizzo,
A. Pedreira,
C. García Miró,
et al.
Show abstract
The NASA Deep Space Network hosts three complexes worldwide for spacecrafts tracking. The Spanish complex,
the Madrid Deep Space Communications Complex (MDSCC), operates a set of highly sensitive antennas, which
are used for Host Country Radio Astronomy (HCRA) during a percentage of their operational time. We have
designed, developed and built a wideband backend for HCRA in MDSCC, which greatly improves its available facilities,
and opens new scientic cases to be tackled. The backend is able to sample up to 6 GHz of instantaneous
bandwidth, in the frequency range from 18 to 50 GHz, using two dierent antennas. An intermediate-frequency
(IF) processor downconverts the two-polarization signals to four base-band channels of 1.5 GHz width. Digitalisation
is done through a set of FPGA-based FFT spectrometers, which can provide spectral resolutions from 7 to
200 kHz, and spectral coverages from 100MHz to 1.5 GHz each. This new facility enables HCRA to aord new
scientic projects, such as extragalactic radio astronomy and spectral surveys; at the same time, the available
time for HC is greatly optimized. It was necessary the development of dedicated software for spectra acquisition
and control of the equipment, and also the upgrading of the existing observing programs. Once end-to-end
assembled, the whole backend was tested through a set of commissioning observations. In this contribution
the main features of the new backend are described, including the IF processor, the FFT spectrometer and the
developed software. Some astronomical results are also included.
An 8 GHz digital spectrometer for millimeter-wave astronomy
Roberto G. García,
Olivier Gentaz,
Maryse Baldino,
et al.
Show abstract
We have designed and tested a digital spectrometer suitable for analyzing 8 GHz baseband signals. It is based on a 16-
Gsps, 5-bit ADC from e2v and a Stratix-IV FPGA employed for later filtering and signal processing. Digitized data is
received and synchronized via twenty high-speed 4-Gbps transceivers integrated in the FPGA. A 64-channel polyphase
filter bank separates the input signal into 250-MHz sub-bands, allowing subsequent high-resolution analysis. To obtain
continuous spectral information over the input bandwidth, we have implemented a 50% overlapping architecture
solution. Subsequently these sub-bands are processed using Fast Fourier Transform modules.
This system meets present-day demands on high-resolution wideband digital back-ends for millimeter-wave telescopes.
This technology will be part of the next generation wideband correlator for the future upgrade of the IRAM Plateau de
Bure interferometer (NOEMA project).
From an MMIC chip to a working cryogenic low-noise amplifier: a detailed study on packaging
Show abstract
Cryogenic Low Noise Amplifiers, based on MMIC HEMT technology, require a careful packaging to reach optimal
performance. Differences between modeled and measured performance can often be related to chip mounting details. In
the framework of the development of new cryogenic LNAs, described in a companion paper, we have developed a
specific packaging to host W-band cryogenic MMIC LNAs. We present here some of the main factors analyzed in the
design and chip integration activities. In particular, mechanical and thermal modeling, LNA chip gluing and adhesive
properties, sensitivity to components integration accuracy (i.e. deviation from the ideal orientation). Preliminary test
results are also reported.
The DBBC environment for millimeter radioastronomy
Show abstract
The Digital Base Band Converter project developed in the last decade produced a general architecture and a
class of boards, firmware and software, giving the possibility to build a general purpose back-end system for
VLBI or single-dish observational activities. Such approach suggests the realization of a digital radio system,
i.e. a receiver with conversion not realized with analogue techniques, maintaining only amplification stages in
the analogue domain. This solution can be applied until a maximum around 16 GHz, the present limit for the
instantaneous input band in the latest version of the DBBC project, while in the millimeter frequency range this
maximum limit of 0.5-2 GHz of the previous versions allows the intermediate frequency to be processed in the
digital domain.
A description of the elements developed in the DBBC project is presented, with their use in different environments.
The architecture is composed of a PC controlled mainframe, and of different modules that can be
combined in a very flexible way in order to realize different instruments. The instrument can be expanded or
retrofitted to meet increasing observational demands. Available modules include ADC converters, processing
boards, physical interfaces (VSI and 10G Ethernet).
Several applications have already been implemented and used in radioastronomic observations: a DDC (Direct
Digital Conversion) for VLBI observations, a Polyphase Digital Filter Bank, and a Multiband Scansion
Spectrometer. Other applications are currently studied for additional functionalities like a spectropolarimeter,
a linear-to-circular polarization converter, a RFI-mitigation tool, and a phase-reference holographic tool-kit.
A 3mm band dual polarization MMIC receiver for the 30-m Pico Veleta Radio Telescope
Patrice Serres,
Olivier Garnier,
Yves Bortolotti,
et al.
Show abstract
We present the design, construction and test results of a prototype MMIC receiver for the 3 mm band (84-116 GHz). The
receiver cryogenic module consists of a single corrugated feed horn cascaded with an Ortho Mode Traducer (OMT) that
splits the two incoming linear polarized signals in two independent single-mode rectangular waveguides. Low noise
MMIC HEMT amplification modules, attached to the OMT WR10 waveguide outputs, amplify the signal of each
polarization channel. Outside the dewar, each signal is filtered, down-converted, and further amplified to provide a final
8 GHz IF bandwidth across 4-12 GHz. The receiver was installed on the Pico Veleta 30 m telescope in August 2010
where it was used to perform spectral line surveys of astronomical sources. The measured receiver noise temperature was
below 75 K with an average value of ~55 K for both polarization channels across 84-116 GHz.
ALMA SIS mixer optimization for stable operation
Show abstract
The Atacama Large Millimeter/Submillimeter Array (ALMA), an interferometric radio telescope will have 66 array
elements when complete. The ALMA Front End is designed to accommodate up to 10 receiver bands covering most of
the wavelength range from 10 to 0.3 mm. Superconductor-insulator-superconductor (SIS) mixers are employed for
Bands 3 (~3 mm) through 10 (~0.3 mm). Ordinarily the SIS bias is selected to achieve the lowest receiver noise
temperatures. However, in order to obtain the lowest detection threshold, the SIS bias also needs to be optimized with
respect to receiver stability. There are also other parameters to be optimized such as the magnetic field strength used to
suppress the Josephson currents and avoidance of Shapiro. This paper will summarize the results of work carried out to
derive the optimal operating parameters for the large number of mixers in use on the telescope so as to keep the
telescope operating reliably and repeatably.
Photonic phased array technology for radio telescope systems
D. H. P. Maat,
K. Dijkstra
Show abstract
The application of novel photonic technologies in radio telescope systems becomes more-and-more attractive thanks to
the improvement of the performance of photonic signal transport and photonic signal processing technologies and a
reduction of their cost level. For the development of photonic technology for radio telescopes like the SKA, a photonic
phased array roadmap has been defined at ASTRON, according to which a number of photonic technology demonstrator
are built and experimentally investigated.
In one of the first steps of the roadmap, a discrete IC component based photonic phased array tile with optical analog
links and photonic beamformer was developed. Currently a photonic phased array tile is being built with hybrid
integrated optical transmitter and photonic beamformer IC technology. In this paper, the photonic phased array
technology roadmap will be described. In addition, a description will be given of both photonic phased array
demonstrator systems and experimental results will be given.
New capabilities for the Southern 1.2m mm-Wave Telescope
Show abstract
In this paper we describe the status of an upgrading program that it is being carried out to modernize the front
and back ends of the Southern 1.2-m mm-Wave Telescope to cover eciently the band from 86 to 115 GHz. On
the one hand, the new front end will have a sideband-separating conguration to suppress the image band noise.
This front end will use one low noise amplier and two Schottky diodes for down conversion. On the other hand,
we are developing a modern digital spectrometer, based on the Recongurable Open Architecture Computing
Hardware (ROACH), to ease the operation and improve the spectral resolution up to a factor of 4. Moreover,
the spectrometer will include IF hybridization capabilities to avoid analog hybrids and, therefore, improve the
sideband rejection ratio of the receiver.
A new phase-lock algorithm for the ALMA receivers
Show abstract
In this work, a new phase-lock algorithm for the Local Oscillator system of the ALMA receiver is presented.
This new algorithm replaced the look-up table based scheme used originally in the ALMA receivers. In
this new scheme all variables are adjusted dynamically on each lock attempt, except for the YIG oscillator
frequency limits. The new developed is able to correct aging and non-linearity of the YIG oscillators used
in the LO system. The provided solution reduces the locking time in up to a factor of ten, improving lock
success rate up to 99.91%.
The status of the QUIJOTE multifrequency instrument
R. J. Hoyland,
M. Aguiar-González,
B. Aja,
et al.
Show abstract
The QUIJOTE-CMB project has been described in previous publications. Here we present the current status of the
QUIJOTE multi-frequency instrument (MFI) with five separate polarimeters (providing 5 independent sky pixels): two
which operate at 10-14 GHz, two which operate at 16-20 GHz, and a central polarimeter at 30 GHz. The optical
arrangement includes 5 conical corrugated feedhorns staring into a dual reflector crossed-draconian system, which
provides optimal cross-polarization properties (designed to be < −35 dB) and symmetric beams. Each horn feeds a novel
cryogenic on-axis rotating polar modulator which can rotate at a speed of up to 1 Hz. The science driver for this first
instrument is the characterization of the galactic emission. The polarimeters use the polar modulator to derive linear
polar parameters Q, U and I and switch out various systematics. The detection system provides optimum sensitivity
through 2 correlated and 2 total power channels. The system is calibrated using bright polarized celestial sources and
through a secondary calibration source and antenna. The acquisition system, telescope control and housekeeping are all
linked through a real-time gigabit Ethernet network. All communication, power and helium gas are passed through a
central rotary joint. The time stamp is synchronized to a GPS time signal. The acquisition software is based on PLCs
written in Beckhoffs TwinCat and ethercat. The user interface is written in LABVIEW. The status of the QUIJOTE MFI
will be presented including pre-commissioning results and laboratory testing.
Control system architecture of QUIJOTE multi-frequency instrument
Show abstract
The QUIJOTE-CMB experiment has been described in previous publications. Here we describe the architecture of the
control system, hardware and software, of the QUIJOTE I instrument (MFI). It is a multi-channel instrument with five
separate polarimeters: two of which operate at 10-14 GHz, two of which operate at 16-20 GHz, and a central polarimeter
at 26-36 GHz. Each polarimeter can rotate at a speed of up to 1 Hz and also can move to discrete angular positions which
allow the linear polar parameters Q, U and I to be derived. The instrument is installed in an alt-azimuth telescope which
implements several operational modes: movement around the azimuth axis at a constant velocity while the elevation axis
is held at a fixed elevation; tracking of a sky object; and raster of a rectangular area both in horizontal and sky
coordinates. The control system of both, telescope and instrument, is based in the following technologies: an LXI-VXI
bus is used for the signal acquisition system; an EtherCAT bus implements software PLCs developed in TwinCAT to
perform the movement of the 5 polarimeters and the 2 axes of the telescope. Science signal, angular positions of the 5
polarimeters and telescope coordinates are sampled at up to 4000 Hz. All these data are correlated by a time stamp
obtained from an external GPS clock implementing the Precise Time Protocol-1588 which provides synchronization to
less than 1 microsecond. The control software also acquires housekeeping (HK) from the different subsystems.
LabVIEW implements the instrument user interface.
Laboratory characterization of CMB polarimeters using novel calibration system with cryogenically cooled loads
Show abstract
Polarimeters used in cosmic microwave background (CMB) experiments must be well calibrated to measure
faint CMB polarization patterns with low systematic errors. Polarimeter characteristics generally vary with
the incident load temperature (Tload). Therefore, re-producing the observing conditions in the laboratory is an
important concern. For polarimeters, we developed a characterization system with cryogenically cooled loads.
The loads generate unpolarized radiation (15 K and 30 K), comparable to the typical sky temperature of the
best sites on the ground, e.g., the Atacama Desert in Chile (Tload ∼ 15 K). The radiation from the loads is
reflected by a metal mirror in the cryostat, yielding partially polarized radiation (600 mK), entering a feed horn
on the polarimeter. Rotation of the mirror alters the incident angle of the polarization and causes periodic
switching of the load temperature for Y -factor measurements. We demonstrated the validity of the system using
a polarimeter developed for an upgrade of QUIET (QUIET-II), which can obtain the Stokes parameters I, Q,
and U simultaneously. The system characterized all the necessary properties, e.g., the responses for I, Q, and
U, and their crosstalk. In addition, a wide range of polarimeter bias conditions was surveyed. The principle of
the characterization system is not limited to a particular frequency or detection scheme. Thus, various types of
state-of-the-art detectors can be calibrated by using this system.
New demodulation scheme for coherent polarimeters in CMB experiments
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We propose an innovative demodulation scheme for coherent detectors used in cosmic microwave background polarization experiments. Removal of non-white noise, e.g., narrow-band noise, in detectors is one of the key requirements for the experiments. A combination of modulation and demodulation is used to extract polarization signals as well as to suppress such noise. Traditional demodulation, which is based on the two-point numerical differentiation, works as a first-order high pass filter for the noise. The proposed demodulation is based on the three-point numerical differentiation. It works as a second-order high pass filter. By using a real detector, we confirmed significant improvements of suppression power for the narrow-band noise. We also found improvement of the noise floor, which is from the stronger suppression to the tail of 1/f noise.
Design and characterization of 90 GHz feedhorn-coupled TES polarimeter pixels in the SPTpol camera
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The SPTpol camera is a two-color, polarization-sensitive bolometer receiver, and was installed on the 10 meter South Pole Telescope in January 2012. SPTpol is designed to study the faint polarization signals in the Cosmic Microwave Background, with two primary scientific goals. One is to constrain the tensor-to-scalar ratio of perturbations in the primordial plasma, and thus constrain the space of permissible in inflationary models. The other is to measure the weak lensing effect of large-scale structure on CMB polarization, which can be used to constrain the sum of neutrino masses as well as other growth-related parameters. The SPTpol focal plane consists of seven 84-element monolithic arrays of 150 GHz pixels (588 total) and 180 individual 90 GHz single- pixel modules. In this paper we present the design and characterization of the 90 GHz modules.
Feedhorn-coupled TES polarimeter camera modules at 150 GHz for CMB polarization measurements with SPTpol
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The SPTpol camera is a dichroic polarimetric receiver at 90 and 150 GHz. Deployed in January 2012 on the South Pole Telescope (SPT), SPTpol is looking for faint polarization signals in the Cosmic Microwave Background (CMB). The camera consists of 180 individual Transition Edge Sensor (TES) polarimeters at 90 GHz and seven 84-polarimeter camera modules (a total of 588 polarimeters) at 150 GHz. We present the design, dark characterization, and in-lab optical properties of the 150 GHz camera modules. The modules consist of photolithographed arrays of TES polarimeters coupled to silicon platelet arrays of corrugated feedhorns, both of which are fabricated at NIST-Boulder. In addition to mounting hardware and RF shielding, each module also contains a set of passive readout electronics for digital frequency-domain multiplexing. A single module, therefore, is fully functional as a miniature focal plane and can be tested independently. Across the modules tested before deployment, the detectors average a critical temperature of 478 mK, normal resistance RN of 1.2Ω , unloaded saturation power of 22.5 pW, (detector-only) optical efficiency of ~ 90%, and have electrothermal time constants < 1 ms in transition.
Performance of the SCUBA-2 dry dilution refrigerator: 4 years of operation at the JCMT
Show abstract
Cryogen free or ‘dry’ dilution refrigerators that integrate a cryocooler such as a two stage pulse tube to replace the conventional liquid helium bath and 1K pot, have become a practical alternative for cooling astronomical detectors to mK temperatures and offer many advantages. SCUBA-2, the new submillimetre camera in operation at the JCMT, on the summit of Mauna Kea, Hawaii, was one of the first instruments to use such a fridge design. The dry dilution fridge for SCUBA-2 has now been in service for almost 4 years during commissioning at JCMT. In the most recent astronomical commissioning phase, the dilution fridge was in continuous operation for 10 months with no loss of base temperature or cooling power, cooling the SCUBA-2 detector arrays to below 100mK while maintaining a further 100Kg of enclosure, shields and SQUID amplifiers at 1K. In this paper we review some of the lessons from operating a dry dilution fridge at the JCMT and the necessary changes that have been incorporated. We present the performance of the fridge and discus its role in ensuring the success of SCUBA-2.
The high altitude qualification tests of the cryogenic and vacuum system for ALMA
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The Cryogenic System of ALMA is one of the core sub systems of the Front End low noise receiver and the failsafe
operation is mandatory to ensure the successful astronomical observations. ESO has done a comprehensive test
campaign on the ALMA operational site Chajnantor1 at an altitude of 5000m, to qualify this system for the harsh
operational conditions.
In this contribution we will present an overview of those Qualification tests which have been carried out on ALMA`s 4K
Cryogenic and Vacuum System components and the additional required measures to operate the system under the special
environmental conditions, respectively the operational constrains. That will include the findings concerning the
optimization of the remote diagnostic and the definition of additional monitor and control parameters. The resulting
solutions have considerable influence on the maintenance processes, the operational staff requirements and the reduction
of the operational costs in particularly with regards to the large system number of 66 antennas.
POLARBEAR-2 optical and polarimeter designs
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POLARBEAR-2 is a ground based cosmic microwave background (CMB) radiation experiment observing from Atacama, Chile. The science goals of POLARBEAR-2 are to measure the CMB polarization signals originating from the inflationary gravity-wave background and weak gravitational lensing. In order to achieve these science goals, POLARBEAR-2 employs 7588 polarization sensitive transition edge sensor bolometers at observing fre quencies of 95 and 150 GHz with 5.5 and 3.5 arcmin beam width, respectively. The telescope is the off-axis Gregorian, Huan Tran Telescope, on which the POLARBEAR-1 receiver is currently mounted. The polarimetry is based on modulation of the polarized signal using a rotating half-wave plate and the rotation of the sky. We present the developments of the optical and polarimeter designs including the cryogenically cooled refractive optics that achieve the overall 4 degrees field-of-view, the thermal filter design, the broadband anti-reflection coating, and the rotating half-wave plate.
SWIPE: a bolometric polarimeter for the Large-Scale Polarization Explorer
P. de Bernardis,
S. Aiola,
G. Amico,
et al.
Show abstract
The balloon-borne LSPE mission is optimized to measure the linear polarization of the Cosmic Microwave Background at large angular scales. The Short Wavelength Instrument for the Polarization Explorer (SWIPE) is composed of 3 arrays of multi-mode bolometers cooled at 0.3K , with optical components and filters cryogenically cooled below 4K to reduce the background on the detectors. Polarimetry is achieved by means of large rotating half-wave plates and wire-grid polarizers in front of the arrays. The polarization modulator is the first component of the optical chain, reducing significantly the effect of instrumental polarization. In SWIPE we trade angular resolution for sensitivity. The diameter of the entrance pupil of the refractive telescope is 45 cm, while the field optics is optimized to collect tens of modes for each detector, thus boosting the absorbed power. This approach results in a FWHM resolution of 1.8, 1.5, 1.2 degrees at 95, 145, 245 GHz respectively. The expected performance of the three channels is limited by photon noise, resulting in a final sensitivity around 0.1-0.2 μK per beam, for a 13 days survey covering 25% of the sky.
Multichroic dual-polarization bolometric detectors for studies of the cosmic microwave background
Show abstract
We are developing multi-chroic antenna-coupled TES detectors for CMB polarimetry. Multi-chroic detectors in- crease the mapping speed per focal plane area and provide greater discrimination of polarized galactic foregrounds with no increase in weight or cryogenic cost. In each pixel, a silicon lens-coupled dual polarized sinuous antenna collects light over a two-octave frequency band. The antenna couples the broadband millimeter wave signal into microstrip transmission lines, and on-chip filter banks split the broadband signal into several frequency bands. Separate TES bolometers detect the power in each frequency band and linear polarization. We will describe the design and performance of these devices and present optical data taken with prototype pixels. Our measurements show beams with percent level ellipticity, percent level cross-polarization leakage, and partitioned bands using banks of 2, 3, and 7 filters. We will also describe the development of broadband anti-reflection coatings for the high dielectric constant lens. The broadband anti-reflection coating has approximately 100% bandwidth and no detectable loss at cryogenic temperature. Finally, we will describe an upgrade for the Polarbear CMB experiment and installation for the LiteBIRD CMB satellite experiment both of which have focal planes with kilo-pixel of these detectors to achieve unprecedented mapping speed.
Stray light suppression in the Goddard IRAM 2-Millimeter Observer (GISMO)
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The Goddard-IRAM Superconducting 2 Millimeter Observer (GISMO) is an 8x16 Transition Edge Sensor (TES) array
of bolometers built as a pathfinder for TES detector development efforts at NASA Goddard Space Flight Center. GISMO
has been used annually at the Institut de Radioastronomie Millimétrique (IRAM) 30 meter telescope since 2007 under
engineering time and was opened in the spring of 2012 to the general astronomical community. The spring deployment
provided an opportunity to modify elements of the room temperature optics before moving the instrument to its new
permanent position in the telescope receiver cabin. This allowed for the possibility to extend the cryostat, introduce
improved cold baffling and thus further optimize the stray light performance for final astronomical use of the instrument,
which has been completed and validated. We will demonstrate and discuss several of the methods used to quantify and
limit the influence of stray light in the GISMO camera.