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[show abstract]
[hide abstract]
ABSTRACT: We describe the signal processing logic, firmware, and software for a frequency-domain multiplexed biasing and demodulation system that reads out transition-edge-sensor bolometer arrays for millimeter-wavelength cosmology telescopes. This system replaces a mixed-signal readout back end with a much smaller and more power-efficient system relying on field-programmable gate arrays for control, computation, and signal processing. The new system is sufficiently robust, automated, and power efficient to be flown on stratospheric balloon-borne telescopes and is being developed further for satellite applications.
IEEE Transactions on Instrumentation and Measurement 02/2012; · 1.21 Impact Factor
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B. Keating,
S. Moyerman,
D. Boettger,
J Edwards,
G. Fuller,
F. Matsuda,
N. Miller,
H. Paar,
G. Rebeiz,
I. Schanning, [......],
M. Hazumi,
T Matsumura,
H Morii,
A Shimizu,
T Tomaru,
P. Hyland, M. Dobbs,
P. Ade,
W. Grainger,
C. Tucker
[show abstract]
[hide abstract]
ABSTRACT: Observations of the temperature anisotropy of the Cosmic Microwave Background
(CMB) lend support to an inflationary origin of the universe, yet no direct
evidence verifying inflation exists. Many current experiments are focussing on
the CMB's polarization anisotropy, specifically its curl component (called
"B-mode" polarization), which remains undetected. The inflationary paradigm
predicts the existence of a primordial gravitational wave background that
imprints a unique B-mode signature on the CMB's polarization at large angular
scales. The CMB B-mode signal also encodes gravitational lensing information at
smaller angular scales, bearing the imprint of cosmological large scale
structures (LSS) which in turn may elucidate the properties of cosmological
neutrinos. The quest for detection of these signals; each of which is orders of
magnitude smaller than the CMB temperature anisotropy signal, has motivated the
development of background-limited detectors with precise control of systematic
effects. The POLARBEAR experiment is designed to perform a deep search for the
signature of gravitational waves from inflation and to characterize lensing of
the CMB by LSS. POLARBEAR is a 3.5 meter ground-based telescope with 3.8
arcminute angular resolution at 150 GHz. At the heart of the POLARBEAR receiver
is an array featuring 1274 antenna-coupled superconducting transition edge
sensor (TES) bolometers cooled to 0.25 Kelvin. POLARBEAR is designed to reach a
tensor-to-scalar ratio of 0.025 after two years of observation -- more than an
order of magnitude improvement over the current best results, which would test
physics at energies near the GUT scale. POLARBEAR had an engineering run in the
Inyo Mountains of Eastern California in 2010 and will begin observations in the
Atacama Desert in Chile in 2011.
10/2011;
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D Schwan,
P A R Ade,
K Basu,
A N Bender,
F Bertoldi,
H-M Cho,
G Chon,
John Clarke, M Dobbs,
D Ferrusca, [......],
C L Reichardt,
P L Richards,
R Schaaf,
P Schilke,
M W Sommer,
H Spieler,
C Tucker,
A Weiss,
B Westbrook,
O Zahn
[show abstract]
[hide abstract]
ABSTRACT: The Atacama pathfinder experiment Sunyaev-Zel'dovich (APEX-SZ) instrument is a millimeter-wave cryogenic receiver designed to observe galaxy clusters via the Sunyaev-Zel'dovich effect from the 12 m APEX telescope on the Atacama plateau in Chile. The receiver contains a focal plane of 280 superconducting transition-edge sensor (TES) bolometers instrumented with a frequency-domain multiplexed readout system. The bolometers are cooled to 280 mK via a three-stage helium sorption refrigerator and a mechanical pulse-tube cooler. Three warm mirrors, two 4 K lenses, and a horn array couple the TES bolometers to the telescope. APEX-SZ observes in a single frequency band at 150 GHz with 1' angular resolution and a 22' field-of-view, all well suited for cluster mapping. The APEX-SZ receiver has played a key role in the introduction of several new technologies including TES bolometers, the frequency-domain multiplexed readout, and the use of a pulse-tube cooler with bolometers. As a result of these new technologies, the instrument has a higher instantaneous sensitivity and covers a larger field-of-view than earlier generations of Sunyaev-Zel'dovich instruments. The TES bolometers have a median sensitivity of 890 μK(CMB)√s (NEy of 3.5 × 10(-4) √s). We have also demonstrated upgraded detectors with improved sensitivity of 530 μK(CMB)√s (NEy of 2.2 × 10(-4) √s). Since its commissioning in April 2007, APEX-SZ has been used to map 48 clusters. We describe the design of the receiver and its performance when installed on the APEX telescope.
The Review of scientific instruments 09/2011; 82(9):091301. · 1.52 Impact Factor
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J. Hubmayr,
J.E. Austermann,
J.A. Beall,
D. Becker,
D.A. Bennett,
B.A. Benson,
L.E. Bleem,
C.L. Chang,
J.E. Carlstrom,
H. Cho, [......],
J. McMahon,
J. Mehl,
S.S. Meyer,
J.P. Nibarger,
M.D. Niemack,
D.R. Schmidt,
E. Shirokoff,
S.M. Simon,
K.W. Yoon,
E.Y. Young
[show abstract]
[hide abstract]
ABSTRACT: We are developing arrays of 150 GHz transition edge sensor (TES) polarimeters for the South Pole Telescope polarimeter (SPTpol). Prototype devices use an aluminum manganese (Al-Mn) alloy TES with a normal resistance R<sub>n</sub> suited to frequency domain multiplexing (fMUX) used in SPTpol. Using the fMUX readout, the devices exhibit noise performance consistent with expectations when R >; 0.8R<sub>n</sub>. Below 0.8R<sub>n</sub>, the detectors have high loopgain and become unstable, which is predicted by use of a compound TES model. We address this issue in a recent fabrication with increased TES heat capacity and normal metal structures on the TES to tune the temperature sensitivity.
IEEE Transactions on Appiled Superconductivity 07/2011; · 1.04 Impact Factor
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B. Westbrook,
P. A. R. Ade,
A. N. Bender,
H. M. Cho,
J. Clarke, M. Dobbs,
D. Ferrusca,
N. W. Halverson,
W. L. Holzapfel,
B. R. Johnson, [......],
A. T. Lee,
M. Lueker,
J. Mehl,
X. Meng,
T. Plagge,
C. L. Reichardt,
P. L. Richards,
D. Schwan,
E. Shirokoff,
H. Spieler
[show abstract]
[hide abstract]
ABSTRACT: We describe the recent reoptimization of the detector array in the APEX‐SZ receiver, which is currently operating at the APEX telescope in Chile. APEX‐SZ is designed to image the Sunyaev Zel’dovich effect (SZE). Observations are made in a single spectral band centered on 150 GHz, which is where the decrement of the SZE peaks. The APEX‐SZ transition‐edge sensor bolometers are micro‐fabricated in six 55‐element sub arrays, which combine to form the full 330‐element focal plane operating at 280 mK. We report on the newest generation of sub‐arrays that use a λ∕4 silicon‐filled backshort. Compared to the first generation array which used a 3λ∕4 backshort, the new arrays have a broader bandwidth and an increased optical efficiency. We present spectral bandpass and efficiency measurements and compare these to electromagnetic simulations of the bolometer absorption. The overall improvement in optical coupling reduces the noise equivalent temperature (NET) of each bolometer by a factor of approximately 1.5. Several galaxy clusters have been observed using the new detectors and analysis of the data is currently underway. We also present plans for future upgrades to the receiver.
AIP Conference Proceedings. 12/2009; 1185(1):363-366.
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[show abstract]
[hide abstract]
ABSTRACT: A digital frequency multiplexing (DfMUX) system has been developed and used to tune large arrays of transition edge sensor (TES) bolometers read out with SQUID arrays for mm-wavelength cosmology telescopes. The DfMUX system multiplexes the input bias voltages and output currents for several bolometers on a single set of cryogenic wires. Multiplexing reduces the heat load on the camera's sub-Kelvin cryogenic detector stage. In this paper we describe the algorithms and software used to set up and optimize the operation of the bolometric camera. The algorithms are implemented on soft processors embedded within FPGA devices operating on each backend readout board. The result is a fully parallelized implementation for which the setup time is independent of the array size. Comment: 5 pages, 4 figures
11/2009;
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K. Basu,
Y Y Zhang,
M. W. Sommer,
A. N. Bender,
F. Bertoldi, M. Dobbs,
H. Eckmiller,
N. W. Halverson,
W. L. Holzapfel,
C. Horellou, [......],
A. T. Lee,
J. Mehl,
K. M. Menten,
F. P. Navarrete,
F. Pacaud,
C. L. Reichardt,
T. H. Reiprich,
P. L. Richards,
D. Schwan,
B. Westbrook
[show abstract]
[hide abstract]
ABSTRACT: We demonstrate the usability of mm-wavelength imaging data obtained from the APEX-SZ bolometer array to derive the radial temperature profile of the hot intra-cluster gas out to radius r_500 and beyond. The goal is to study the physical properties of the intra-cluster gas by using a non-parametric de-projection method that is, aside from the assumption of spherical symmetry, free from modeling bias. We use publicly available X-ray imaging data from the XMM-Newton observatory and our Sunyaev-Zel'dovich Effect (SZE) imaging data from the APEX-SZ experiment at 150 GHz to de-project the density and temperature profiles for the relaxed cluster Abell 2204. We derive the gas density, temperature and entropy profiles assuming spherical symmetry, and obtain the total mass profile under the assumption of hydrostatic equilibrium. For comparison with X-ray spectroscopic temperature models, a re-analysis of the recent Chandra observation is done with the latest calibration updates. Using the non-parametric modeling we demonstrate a decrease of gas temperature in the cluster outskirts, and also measure the gas entropy profile. These results are obtained for the first time independently of X-ray spectroscopy, using SZE and X-ray imaging data. The contribution of the SZE systematic uncertainties in measuring T_e at large radii is shown to be small compared to the Chandra systematic spectroscopic errors. The upper limit on M_200 derived from the non-parametric method is consistent with the NFW model prediction from weak lensing analysis. Comment: Replaced with the published version; A&A 519, A29 (2010)
11/2009;
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[show abstract]
[hide abstract]
ABSTRACT: We have designed and demonstrated a superconducting quantum interference device (SQUID) array linearized with cryogenic feedback. To achieve the necessary loop gain, a 300-element series array SQUID is constructed from three monolithic 100-element series arrays. A feedback resistor completes the loop from the SQUID output to the input coil. The short feedback path of this linearized SQUID array (LISA) allows for a substantially larger flux-locked loop bandwidth as compared to a SQUID flux-locked loop that includes a room temperature amplifier. The bandwidth, linearity, noise performance, and 3 Phi(0) dynamic range of the LISA are sufficient for its use in our target application: the multiplexed readout of transition-edge sensor bolometers.
The Review of scientific instruments 09/2009; 80(9):094501. · 1.52 Impact Factor
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N. W. Halverson,
T. Lanting,
P. A. R. Ade,
K. Basu,
A. N. Bender,
B. A. Benson,
F. Bertoldi,
H.-M. Cho,
G. Chon,
J. Clarke, [......],
C. Reichardt,
P. L. Richards,
R. Schaaf,
P. Schilke,
F. Schuller,
D. Schwan,
H. Spieler,
C. Tucker,
A. Weiss,
and O. Zahn
[show abstract]
[hide abstract]
ABSTRACT: We present observations of the Sunyaev-Zel'dovich effect (SZE) in the Bullet cluster (1E 0657–56) using the APEX-SZ instrument at 150 GHz with a resolution of 1'. The main results are maps of the SZE in this massive, merging galaxy cluster. The cluster is detected with 23σ significance within the central 1' radius of the source position. The SZE map has a broadly similar morphology to that in existing X-ray maps of this system, and we find no evidence for significant contamination of the SZE emission by radio or IR sources. In order to make simple quantitative comparisons with cluster gas models derived from X-ray observations, we fit our data to an isothermal elliptical β model, despite the inadequacy of such a model for this complex merging system. With an X-ray-derived prior on the power-law index, β = 1.04+0.16 –0.10, we find a core radius r c = 142'' ± 18'', an axial ratio of 0.889 ± 0.072, and a central temperature decrement of –771 ± 71 μKCMB, including a ±5.5% flux calibration uncertainty. Combining the APEX-SZ map with a map of projected electron surface density from Chandra X-ray observations, we determine the mass-weighted temperature of the cluster gas to be T mg = 10.8 ± 0.9 keV, significantly lower than some previously reported X-ray spectroscopic temperatures. Under the assumption of an isothermal cluster gas distribution in hydrostatic equilibrium, we compute the gas mass fraction for prolate and oblate spheroidal geometries and find it to be consistent with previous results from X-ray and weak-lensing observations. This work is the first result from the APEX-SZ experiment, and represents the first reported scientific result from observations with a large array of multiplexed superconducting transition-edge sensor bolometers.
The Astrophysical Journal 07/2009; 701(1):42. · 6.02 Impact Factor
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M. Lueker,
B.A. Benson,
C.L. Chang,
Hsiao-Mei Cho, M. Dobbs,
W.L. Holzapfel,
T. Lanting,
A.T. Lee,
J. Mehl,
T. Plagge,
E. Shirokoff,
H.G. Spieler,
J.D. Vieira
[show abstract]
[hide abstract]
ABSTRACT: In contemporary cosmic microwave background experiments, bolometric detectors are often background limited, and in this case the sensitivity of instruments can only be improved by increasing the number of background-limited detectors, and so contemporary TES receivers contain as many pixels as possible. Frequency-domain multiplexing (fMUX) is one strategy for reading out many detectors with one SQUID. For any readout system, it is important to carefully evaluate the thermal design of detector, in conjunction with the readout bandwidth, in order to ensure stable electro-thermal feedback (ETF). We demonstrate a novel technique for characterizing the thermal circuit of our detectors, using am AC-bias and the fMUX electronics. This technique is used to study the internal thermal coupling of a TES bolometer. We illustrate how the insights gathered by this technique have been instrumental in improving the stability of our multiplexed detectors for the south pole telescope (SPT).
IEEE Transactions on Appiled Superconductivity 07/2009; · 1.04 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: This paper describes contributions to the workshop, 'Technology Development for a CMB Probe of Inflation,' held at NIST in Boulder CO, Aug. 25-28, 2008 concerning technologies to read out direct detectors (including bolometers and microwave kinetic inductance detectors) in a CMBPol satellite mission. The large number of polarimeters required for a satellite mission will likely make it necessary to multiplex the output signals into a small number of readout channels at the cold state. We describe both the cryogenic components and the present-generation warm readout electronics, consider the benefits and challenges of each option, and analyze their technology readiness level and needed additional investments.
Journal of Physics Conference Series 06/2009; 155(1):012004.
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S. Dodelson,
R. Easther,
S. Hanany,
L. McAllister,
S Meyer,
L. Page,
P. Ade,
A. Amblard,
A. Ashoorioon,
C. Baccigalupi, [......],
R. Flauger,
P. Fosalba,
J. Fowler,
S. Galli,
E. Gates,
W. Gear,
Y Giraud-Heraud,
K. Gorski,
B. Greene,
A. Gruppuso
[show abstract]
[hide abstract]
ABSTRACT: Modern cosmology has sharpened questions posed for millennia about the origin of our cosmic habitat. The age-old questions have been transformed into two pressing issues primed for attack in the coming decade: How did the Universe begin? and What physical laws govern the Universe at the highest energies? The clearest window onto these questions is the pattern of polarization in the Cosmic Microwave Background (CMB), which is uniquely sensitive to primordial gravity waves. A detection of the special pattern produced by gravity waves would be not only an unprecedented discovery, but also a direct probe of physics at the earliest observable instants of our Universe. Experiments which map CMB polarization over the coming decade will lead us on our first steps towards answering these age-old questions.
03/2009;
-
[show abstract]
[hide abstract]
ABSTRACT: We have designed and demonstrated a Superconducting Quantum Interference Device (SQUID) array linearized with cryogenic feedback. To achieve the necessary loop gain a 300 element series array SQUID is constructed from three monolithic 100-element series arrays. A feedback resistor completes the loop from the SQUID output to the input coil. The short feedback path of this Linearized SQUID Array (LISA) allows for a substantially larger flux-locked loop bandwidth as compared to a SQUID flux-locked loop that includes a room temperature amplifier. The bandwidth, linearity, noise performance, and dynamic range of the LISA are sufficient for its use in our target application: the multiplexed readout of transition-edge sensor bolometers.
02/2009;
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M. Nord,
K. Basu,
F. Pacaud,
P. A. R. Ade,
A. N. Bender,
B. A. Benson,
F. Bertoldi,
H. M. Cho,
G. Chon,
J. Clarke, [......],
K. M. Menten,
T. Plagge,
C. L. Reichardt,
P. L. Richards,
R. Schaaf,
D. Schwan,
H. Spieler,
C. Tucker,
A Weiss,
O. Zahn
[show abstract]
[hide abstract]
ABSTRACT: We used the APEX-SZ and LABOCA bolometer cameras on the APEX telescope to map the decrement of the Sunyaev-Zeldovich effect at 150 GHz and the increment at 345 GHz toward the galaxy cluster Abell 2163. The SZE images were used to model the radial density and temperature distribution of the ICM, and to derive the gas mass fraction in the cluster under the assumption of hydrostatic equilibrium. We used the isothermal beta model to fit the SZE decrement/increment radial profiles. We performed a simple, non-parametric de-projection of the radial density and temperature profiles, in conjunction with XMM-Newton X-ray data, under the simplifying assumption of spherical symmetry. We combined the peak SZE signals derived in this paper with published SZE measurements of this cluster to derive the cluster line-of-sight bulk velocity and the central Comptonization, using priors on the ICM temperature. We find that the best-fit isothermal model to the SZE data is consistent with the ICM properties implied by the X-ray data, particularly inside the central 1 Mpc radius. Although the assumptions of hydrostatic equilibrium and spherical symmetry may not be optimal for this complex system, the results obtained under these assumptions are consistent with X-ray and weak-lensing measurements. This shows the applicability of the simple joint SZE and X-ray de-projection technique described in this paper for clusters with a wide range of dynamical states. (Abridged) Comment: 14 pages, 9 figures. To appear in A&A. Sections 4 and 5 updated
02/2009;
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Ilan Sagiv,
A. M. Aboobaker,
P. Ade,
F. Aubin,
C. Baccigalupi,
J. Borrill,
D. Chapman,
J. Didier, M. Dobbs,
W. Grainger, [......],
N. Ponthieu,
B. Reichborn-Kjennerud,
T. Renbarger,
F. Stivoli,
R. Stompor,
H. Tran,
G. Tucker,
J. Vinokurov,
M. Zaldarriaga,
K. Zilic
[show abstract]
[hide abstract]
ABSTRACT: We report on the status of EBEX, a NASA-funded balloon-borne polarimeter
designed to measure the B-mode polarization of the cosmic microwave
background radiation. The EBEX receiver is designed to set a 2σ
upper limit on an inflationary tensor-to-scalar ratio of 0.02. This
limit assumes a 14-day flight, a scan pattern covering 420 square
degrees of the sky, and foreground subtraction to levels below detector
noise. The instrument employs a 1.5 meter Gregorian-type telescope and
1440 bolometric transition edge sensor detectors distributed over two
focal planes. Polarization is measured using a rotating achromatic half
wave plate (AHWP) and a fixed polarizing grid. The AHWP is continuously
rotated using a superconducting magnetic bearing. Sky signals will be
observed in three bands centered at 150, 250 and 410 GHz, providing
strong leverage against the polarized dust foreground. Integration of
the gondola and the receiver will occur in fall 2008. A short-duration
test flight employing 384 detectors in one focal plane is planned for
2009.
12/2008; 41:500.
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N. W. Halverson,
T. Lanting,
P. A. R. Ade,
K. Basu,
A. N. Bender,
B. A. Benson,
F. Bertoldi,
H. M. Cho,
G. Chon,
J. Clarke, [......],
C. Reichardt,
P. L. Richards,
R. Schaaf,
P. Schilke,
F. Schuller,
D. Schwan,
H. Spieler,
C. Tucker,
A Weiss,
O. Zahn
[show abstract]
[hide abstract]
ABSTRACT: We present observations of the Sunyaev-Zel'dovich effect (SZE) in the Bullet cluster (1E 0657--56) using the APEX-SZ instrument at 150 GHz with a resolution of 1 arcmin. The main results are maps of the SZE in this massive, merging galaxy cluster. The cluster is detected with 23 sigma significance within the central 1 arcmin radius of the source position. The SZE map has a broadly similar morphology to that in existing X-ray maps of this system, and we find no evidence for significant contamination of the SZE emission by radio or IR sources. In order to make simple quantitative comparisons with cluster gas models derived from X-ray observations, we fit our data to an isothermal elliptical beta model, despite the inadequacy of such a model for this complex merging system. With an X-ray derived prior on the power-law index, beta = 1.04 +0.16 -0.10, we find a core radius r_c =142 +/- 18 arcsec, an axial ratio of 0.889 +/- 0.072, and a central temperature decrement of -771 +/- 71 micro-K_CMB, including a +/-5.5% flux calibration uncertainty. Combining the APEX-SZ map with a map of projected electron surface density from Chandra X-ray observations, we determine the mass-weighted temperature of the cluster gas to be T_mg=10.8 +/- 0.9 keV, significantly lower than some previously reported X-ray spectroscopic temperatures. Under the assumption of an isothermal cluster gas distribution in hydrostatic equilibrium, we compute the gas mass fraction for prolate and oblate spheroidal geometries and find it to be consistent with previous results from X-ray and weak lensing observations. This work is the first result from the APEX-SZ experiment, and represents the first reported scientific result from observations with a large array of multiplexed superconducting transition-edge sensor bolometers. Comment: 17 pages, 5 figures, accepted for publication in the Astrophysical Journal. Changes in v2: Modified in response to referee comments. Also, improvements in the analysis pipeline and flux calibration result in modification of the maps and model fit parameters. Calibration section and X-ray comparison sections are significantly modified
07/2008;
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[show abstract]
[hide abstract]
ABSTRACT: An FPGA based digital signal processing (DSP) system for biasing and reading out multiplexed bolometric detectors for mm-wavelength telescopes is presented. This readout system is being deployed for balloon-borne and ground based cosmology experiments with the primary goal of measuring the signature of inflation with the Cosmic Microwave Background Radiation. The system consists of analog superconducting electronics running at 250 mK and 4 K, coupled to digital room temperature backend electronics described here. The digital electronics perform the real time functionality with DSP algorithms implemented in firmware. A soft embedded processor provides all of the slow housekeeping control and communications. Each board in the system synthesizes multi-frequency combs of 8 to 32 carriers in the MHz band to bias the detectors. After the carriers have been modulated with the sky-signal by the detectors, the same boards digitize the comb directly. The carriers are mixed down to base-band and low pass filtered. The signal bandwidth of 0.050 Hz-100 Hz places extreme requirements on stability and requires powerful filtering techniques to recover the sky-signal from the MHz carriers.
IEEE Transactions on Nuclear Science 03/2008; · 1.45 Impact Factor
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SPT Collaboration,
J. E. Ruhl,
P. A. R. Ade,
J. E. Carlstrom,
H. M. Cho,
T. Crawford, M. Dobbs,
C. H. Greer,
N. W. Halverson,
W. L. Holzapfel, [......],
J. J. Mohr,
S. Padin,
T. Plagge,
C. Pryke,
D. Schwan,
M. K. Sharp,
M. C. Runyan,
H. Spieler,
Z. Staniszewski,
A. A. Stark
[show abstract]
[hide abstract]
ABSTRACT: A new 10 meter diameter telescope is being constructed for deployment at the
NSF South Pole research station. The telescope is designed for conducting
large-area millimeter and sub-millimeter wave surveys of faint, low contrast
emission, as required to map primary and secondary anisotropies in the cosmic
microwave background. To achieve the required sensitivity and resolution, the
telescope design employs an off-axis primary with a 10m diameter clear
aperture. The full aperture and the associated optics will have a combined
surface accuracy of better than 20 microns rms to allow precision operation in
the submillimeter atmospheric windows. The telescope will be surrounded with a
large reflecting ground screen to reduce sensitivity to thermal emission from
the ground and local interference. The optics of the telescope will support a
square degree field of view at 2mm wavelength and will feed a new 1000-element
micro-lithographed planar bolometric array with superconducting transition-edge
sensors and frequency-multiplexed readouts. The first key project will be to
conduct a survey over approximately 4000 degrees for galaxy clusters using the
Sunyaev-Zel'dovich Effect. This survey should find many thousands of clusters
with a mass selection criteria that is remarkably uniform with redshift. Armed
with redshifts obtained from optical and infrared follow-up observations, it is
expected that the survey will enable significant constraints to be placed on
the equation of state of the dark energy.
11/2004;
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[show abstract]
[hide abstract]
ABSTRACT: We describe the development of a frequency-domain multiplexer (MUX) to read out arrays of superconducting transition-edge sensors (TES). Fabrication of large-format arrays of these sensors is becoming practical; however, reading out each sensor in the array is a major instrumental challenge. Frequency-domain multiplexing can greatly simplify the instrumentation of large arrays by reducing the number of SQUID's (superconducting quantum interference devices) and wires to the low temperature stages. Each sensor is AC biased at a different frequency, ranging from 380 kHz to 1 MHz. Each sensor signal amplitude-modulates its respective AC bias frequency. An LC filter associated with each sensor suppresses Johnson noise from the other sensors. The signals are combined at a current summing node and measured by a single SQUID. The individual signals from each sensor are then lock-in detected by room temperature electronics. Test chips with fully lithographed LC filters for up to 32 channels have been designed and fabricated. The capacitance and inductance values have been measured and are close to the design goals. We discuss the basic principles of frequency-domain multiplexing, the design and testing of the test chips, and the implementation of a practical system.
IEEE Transactions on Appiled Superconductivity 07/2003; · 1.04 Impact Factor
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D Schwan,
F Bertoldi,
S Cho, M Dobbs,
R Guesten,
N.W Halverson,
W.L Holzapfel,
E Kreysa,
T.M Lanting,
A.T Lee, [......],
J Mehl,
K Menten,
D Muders,
M Myers,
T Plagge,
A Raccanelli,
P Schilke,
P.L Richards,
H Spieler,
M White
[show abstract]
[hide abstract]
ABSTRACT: The APEX-SZ experiment is a sky survey designed to discover galaxy clusters via the Sunyaev–Zel’dovich effect at millimeter wavelengths. We describe the components of the instrument, including the 12 m Atacama Pathfinder Experiment telescope, optics, Transition-edge sensor bolometer array and SQUID readout. APEX-SZ will begin observations in 2004.
New Astronomy Reviews.
