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AMI Consortium: T. W. Shimwell,
R. W. Barker,
P. Biddulph,
D. Bly,
R. C. Boysen,
A. R. Brown,
M. L. Brown,
C. Clementson,
M. Crofts,
T. L. Culverhouse, [......],
P. F. Scott,
C. Shaw,
H. Smith,
D. J. Titterington,
M. Velic,
E. M. Waldram,
S. West,
B. A. Wood, G. Yassin,
J. T. L. Zwart
[show abstract]
[hide abstract]
ABSTRACT: We present an interesting Sunyaev-Zel'dovich (SZ) detection in the first of
the Arcminute Microkelvin Imager (AMI) 'blind', degree-square fields to have
been observed down to our target sensitivity of 100{\mu}Jy/beam. In follow-up
deep pointed observations the SZ effect is detected with a maximum peak
decrement greater than 8 \times the thermal noise. No corresponding emission is
visible in the ROSAT all-sky X-ray survey and no cluster is evident in the
Palomar all-sky optical survey. Compared with existing SZ images of distant
clusters, the extent is large (\approx 10') and complex; our analysis favours a
model containing two clusters rather than a single cluster. Our Bayesian
analysis is currently limited to modelling each cluster with an ellipsoidal or
spherical beta-model, which do not do justice to this decrement. Fitting an
ellipsoid to the deeper candidate we find the following. (a) Assuming that the
Evrard et al. (2002) approximation to Press & Schechter (1974) correctly gives
the number density of clusters as a function of mass and redshift, then, in the
search area, the formal Bayesian probability ratio of the AMI detection of this
cluster is 7.9 \times 10^4:1; alternatively assuming Jenkins et al. (2001) as
the true prior, the formal Bayesian probability ratio of detection is 2.1
\times 10^5:1. (b) The cluster mass is MT,200 = 5.5+1.2\times 10^14h-1M\odot.
(c) Abandoning a physical model with num- -1.3 70 ber density prior and instead
simply modelling the SZ decrement using a phenomenological {\beta}-model of
temperature decrement as a function of angular distance, we find a central SZ
temperature decrement of -295+36 {\mu}K - this allows for CMB primary
anisotropies, receiver -15 noise and radio sources. We are unsure if the
cluster system we observe is a merging system or two separate clusters.
12/2010;
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J. V. Buckle,
R. E. Hills,
H. Smith,
W. R. F. Dent,
G Bell,
E. I. Curtis,
R. Dace,
H. Gibson,
S. F. Graves,
J. Leech, [......],
P. Friberg,
T. Jenness,
R. Kackley,
N. P. Rees,
R. Tilanus,
C. Walther,
W. Zwart,
T.M. Klapwijk,
M. Kroug,
T. Zijlstra
[show abstract]
[hide abstract]
ABSTRACT: This paper describes a new Heterodyne Array Receiver Programme (HARP) and Auto-Correlation Spectral Imaging System (ACSIS) that have recently been installed and commissioned on the James Clerk Maxwell Telescope (JCMT). The 16-element focal-plane array receiver, operating in the submillimetre from 325 to 375 GHz, offers high (three-dimensional) mapping speeds, along with significant improvements over single-detector counterparts in calibration and image quality. Receiver temperatures are $\sim$120 K across the whole band and system temperatures of $\sim$300K are reached routinely under good weather conditions. The system includes a single-sideband filter so these are SSB figures. Used in conjunction with ACSIS, the system can produce large-scale maps rapidly, in one or more frequency settings, at high spatial and spectral resolution. Fully-sampled maps of size 1 square degree can be observed in under 1 hour. The scientific need for array receivers arises from the requirement for programmes to study samples of objects of statistically significant size, in large-scale unbiased surveys of galactic and extra-galactic regions. Along with morphological information, the new spectral imaging system can be used to study the physical and chemical properties of regions of interest. Its three-dimensional imaging capabilities are critical for research into turbulence and dynamics. In addition, HARP/ACSIS will provide highly complementary science programmes to wide-field continuum studies, and produce the essential preparatory work for submillimetre interferometers such as the SMA and ALMA. Comment: MNRAS Accepted 2009 July 2. 18 pages, 25 figures and 6 tables
07/2009;
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J. T. L. Zwart,
R. W. Barker,
P. Biddulph,
D. Bly,
R. C. Boysen,
A. R. Brown,
C. Clementson,
M. Crofts,
T. L. Culverhouse,
J. Czeres, [......],
C. Shaw,
T. W. Shimwell,
H. Smith,
A. C. Taylor,
D. J. Titterington,
M. Velić,
E. M. Waldram,
S. West,
B. A. Wood, G. Yassin
[show abstract]
[hide abstract]
ABSTRACT: The Arcminute Microkelvin Imager is a pair of interferometer arrays operating with six frequency channels spanning 13.9–18.2 GHz, for observations on angular scales of 30 arcsec–10 arcmin and for declinations greater than −15°; the Small Array has a sensitivity of 30 mJy s−1/2 and the Large Array has a sensitivity of 3 mJy s−1/2. The telescope is aimed principally at Sunyaev–Zel'dovich imaging of clusters of galaxies. We discuss the design of the telescope and describe and explain its electronic and mechanical systems.
Monthly Notices of the Royal Astronomical Society 12/2008; 391(4):1545 - 1558. · 4.90 Impact Factor
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L. Piccirillo,
P. Ade,
M. D. Audley,
C. Baines,
R. Battye,
M. Brown,
P. Calisse,
A. Challinor,
W. D. Duncan,
P. Ferreira, [......],
D. Sutton,
A. Taylor,
G. Teleberg,
D. Titterington,
V. N. Tsaneva,
C. Tucker,
R. Watson,
S. Withington, G. Yassin,
J. Zhang
[show abstract]
[hide abstract]
ABSTRACT: ClOVER is a multi-frequency experiment optimised to measure the Cosmic
Microwave Background (CMB) polarization, in particular the B-mode
component. ClOVER comprises two instruments observing respectively at 97
GHz and 150/225 GHz. The focal plane of both instruments consists of an
array of corrugated feed-horns coupled to TES detectors cooled at 100
mK. The primary science goal of ClOVER is to be sensitive to
gravitational waves down to r ~ 0.03 (at 3σ)in two years of
operations.
Proc SPIE 07/2008; 7020:35.
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C.E. North,
B. R. Johnson,
P. A. R. Ade,
M.D. Audley,
C. Baines,
R. A. Battye,
M. L. Brown,
P. Cabella,
P. G. Calisse,
A. D. Challinor, [......],
D. Sutton,
A. C. Taylor,
G. Teleberg,
D. Titterington,
V. Tsaneva,
C. Tucker,
R Watson,
S. Withington, G. Yassin,
J. Zhang
[show abstract]
[hide abstract]
ABSTRACT: We describe the objectives, design and predicted performance of Clover, which is a ground-based experiment to measure the faint ``B-mode'' polarisation pattern in the cosmic microwave background (CMB). To achieve this goal, clover will make polarimetric observations of approximately 1000 deg^2 of the sky in spectral bands centred on 97, 150 and 225 GHz. The observations will be made with a two-mirror compact range antenna fed by profiled corrugated horns. The telescope beam sizes for each band are 7.5, 5.5 and 5.5 arcmin, respectively. The polarisation of the sky will be measured with a rotating half-wave plate and stationary analyser, which will be an orthomode transducer. The sky coverage combined with the angular resolution will allow us to measure the angular power spectra between 20 < l < 1000. Each frequency band will employ 192 single polarisation, photon noise limited TES bolometers cooled to 100 mK. The background-limited sensitivity of these detector arrays will allow us to constrain the tensor-to-scalar ratio to 0.026 at 3sigma, assuming any polarised foreground signals can be subtracted with minimal degradation to the 150 GHz sensitivity. Systematic errors will be mitigated by modulating the polarisation of the sky signals with the rotating half-wave plate, fast azimuth scans and periodic telescope rotations about its boresight. The three spectral bands will be divided into two separate but nearly identical instruments - one for 97 GHz and another for 150 and 225 GHz. The two instruments will be sited on identical three-axis mounts in the Atacama Desert in Chile near Pampa la Bola. Observations are expected to begin in late 2009.
06/2008;
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[show abstract]
[hide abstract]
ABSTRACT: A novel design of a waveguide to microstrip or coplanar waveguide transition using a unilateral finline taper is presented. The transition from the unilateral finline mode to the TEM microstrip mode is done directly, avoiding the antipodal finline tapers that have commonly been employed. This results in significant simplification of the design and fabrication, and shortening of the chip length, thereby reducing insertion loss. Also presented are designs at 90 GHz that can be employed in superconducting tunnel junction mixers or transition edge sensor bolometers, and scale-model measurements at 15 GHz.
Electronics Letters 02/2008; · 0.96 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: We describe the design and performance of Potter horns at millimetre and submillimetre wavelength employing a novel software
package that we have developed, using Genetic Algorithm. The horn is easy to fabricate and exhibits excellent beam circularity
and low cross polarization over a 15% bandwidth which is sufficient for many applications. Excitation of the required higher
order modes is done by either a step or a flare discontinuity at the horn throat. In each case we provide design curves that
give the optimum parameters of the horn geometry as a function of frequency and beamwidth. The range of values provided covers
the parameters required for the design of horns for telescope feeds and various other instruments. The design curves show
clearly that the flare-step performance is superior to the traditional groove-step Potter horn. The simulations for designing
these horns were carried out at millimetre and submillimetre wavelengths but the results can be scaled to lower or higher
frequencies. A key component in the design method is the optimization software that searches for the correct magnitude and
location of the flare discontinuities. We have developed a software package based on the combination of modal matching, a
genetic algorithm (GA) and downhill simplex optimization. The genetic code is first used to locate the proximity of the global
minimum. The set of parameters obtained are then used as a starting point for the simplex method, which refines the parameters
to the required accuracy.
International Journal of Infrared and Millimeter Waves 11/2007; 28(12):1103-1114. · 0.58 Impact Factor
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M.D. Audley,
D.M. Glowacka,
D.J. Goldie,
A.N. Lasenby,
V.N. Tsaneva,
S. Withington,
P.K. Grimes,
C.E. North, G. Yassin,
L. Piccirillo,
G. Pisano,
P.R. Ade,
G. Teleberg,
K.D. Irwin,
W.D. Duncan,
C.D. Reintsema,
M. Halpern,
E.S. Battistelli
[show abstract]
[hide abstract]
ABSTRACT: CLOVER aims to detect the signature of gravitational waves from inflation by measuring the B-mode polarization of the cosmic microwave background. CLOVER consists of two polarimeters. One operates at 97 GHz, using finline-coupled transition edge sensors (TES). The other has a combined 150/220-GHz focal plane populated by radial-probe coupled TES detectors. The 97-GHz instrument will have 100 feedhorns and 200 detectors while the combined 150 and 220-GHz instrument will have a total of 200 horns. To achieve the target NEP of 1.5 x 10-<sup>17</sup> W Hz<sup>-1</sup> the 97-GHz detectors will have a transition temperature of 190 mK and will operate with a base temperature of ~ 100 mK. CLOVER's detectors are fabricated on 225-micron silicon substrates. In the 97-GHz instrument a finline transition feeds a microstrip which is terminated by a matched resistor on the silicon nitride island that carries the TES. Each detector is fabricated as a single chip to ensure a 100% operational focal plane. The detectors are mounted in linear modules made of copper which form split-block waveguides. Each detector module contains a time-division SQUID multiplexer to read out the detectors. The multiplexed signals are further amplified by SQUID series arrays. The first prototype detectors for CLOVER have a transition temperature of 350 mK and were fabricated to validate the detector design and the polarimeter technology. We have characterised these detectors in a dedicated test facility. The CLOVER testbed contains cryogenics similar to those in the final instrument: a pulse-tube cooler, He-7 sorption fridge, and a mini dilution fridge so that the detectors are tested in a realistic environment. The test bed has a cryogenic black- body source with band-defining filters for optical testing. As well as the multi-channel electronics that will be used on the final instrument the test bed has an analogue SQUID readout which allows us to characterise the readout fully. We discuss the result-
s of the detector tests and the design changes needed to achieve the required sensitivity.
Infrared and Millimeter Waves, 2007 and the 2007 15th International Conference on Terahertz Electronics. IRMMW-THz. Joint 32nd International Conference on; 10/2007
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[show abstract]
[hide abstract]
ABSTRACT: A superconducting thin-film nanoswitch for the subterahertz frequency range has been proposed, developed, fabricated, and
tested. The switch makes it possible to modulate the microwave signal or switch it between two branches of a circuit with
low losses and high speed. The switch can be naturally integrated with superconducting high-sensitive detectors. Its application
makes it possible to avoid the use of massive slow mechanical modulators and to improve the measurement accuracy in decisive
astrophysical experiments such as the investigation of the anisotropy of the cosmic microwave background.
JETP Letters 09/2007; 86(4):275-277. · 1.35 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: We describe a procedure for modeling the nonlinear, quantum-mechanical behavior of very high harmonic superconductor-insulator-superconductor (SIS) mixers. A typical mixer is pumped by a strong microwave source at 10–15 GHz , which causes high-harmonic (20–40) currents to flow, any one of which can be used as a local oscillator to downconvert a submillimeter-wave signal to a low microwave frequency, 1–8 GHz . This mode of operation is attractive for measuring the beam patterns of conventional SIS mixers, because only a single submillimeter-wave source is needed. We conducted simulations using the 20th harmonic of a 13.5 GHz microwave source, downconverting a 271.4 GHz signal to a 1.4 GHz intermediate frequency. These simulations clearly show that linear downconversion can be achieved even for relatively high levels of rf signal power; although, care is needed when choosing the operating point. The patterns of behavior seen in the simulations are in remarkable agreement with recently published experimental results.
Journal of Applied Physics 02/2007; · 2.17 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: The design and test results of a compact C-band orthomode transducer are presented. The transducer comprises four rectangular probes orthogonally arranged in a circular waveguide, designed to work in the WG13 band. Measurements of the system in the frequency range 4.64 - 7.05 GHz agree very well with simulation results and show a cross-polarisation level below -58 dB, a return loss of about -20 dB, and an insertion loss difference of less than 0.18 dB between the orthogonal polarisation modes across the full waveguide band.
Electronics Letters 02/2007; · 0.96 Impact Factor
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AMI Collaboration,
R. Barker,
P Biddulph,
D. Bly,
R. Boysen,
A. Brown,
C. Clementson,
M. Crofts,
T. Culverhouse,
J. Czeres, [......],
P Scott,
C Shaw,
A Taylor,
D. Titterington,
M. Velic,
E. Waldram,
S. West,
B. Wood, G. Yassin,
J. Zwart
[show abstract]
[hide abstract]
ABSTRACT: We report the first detection of a Sunyaev-Zel'dovich (S-Z) decrement with the Arcminute Microkelvin Imager (AMI). We have made commissioning observations towards the cluster A1914 and have measured an integrated flux density of -8.61 mJy in a uv-tapered map with noise level 0.19 mJy/beam. We find that the spectrum of the decrement, measured in the six channels between 13.5-18GHz, is consistent with that expected for a S-Z effect. The sensitivity of the telescope is consistent with the figures used in our simulations of cluster surveys with AMI. Comment: 5 pages, 6 figures, submitted to MNRAS Letters
09/2005;
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G. Pisano,
P. A. R. Ade,
C. Calderon,
A. D. Challinor,
P. de Bernardis,
L. Dunlop,
W. K. Gear,
Y. Giraud-Héraud,
D. J. Goldie,
K. J. B. Grainge, [......],
M. E. Jones,
A. N. Lasenby,
B. Maffei,
P. D. Mauskopf,
S. J. Melhuish,
A. Orlando,
L. Piccirillo,
A. C. Taylor,
S. Withington, G. Yassin
[show abstract]
[hide abstract]
ABSTRACT: The C$_{\it l}$OVER instrument (described elsewhere in this volume) is being built to measure the $B$-mode polarisation of the Cosmic Microwave Background. Each of the 256 pixels is made up a pseudo-correlation receiver that can be realised using either waveguide or microstrip technology. In this work we present a design study for a possible waveguide-based solution. Each of the individual components has been optimised using electromagnetic finite-element modelling software (HFSS).
EAS Publications Series 01/2005; 14:245.
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[show abstract]
[hide abstract]
ABSTRACT: We report the successful operation of a superconductor-insulator-superconductor (SIS) finline mixer operating near the superconducting energy gap of Nb. The mixer employs a new type of Pickett-Potter horn-reflector (PPHR) antenna, which exhibits low sidelobes and low cross-polarization levels, and yet is easy to fabricate. The SIS tunnel junction and all of the integrated superconducting tuning circuits are fabricated from Nb using planar-circuit technology. The mixer employs an antipodal finline section, deposited on one side of a quartz substrate, which transforms the high impedance of the waveguide (≈300 Ω) to the low impedance of the microstrip line (≈20 Ω). The Nb/Al-oxide/Nb tunnel junction is fabricated at the same time as the finline circuit. In this paper, we describe the design and testing of the mixer, and pay particular attention to the electromagnetic design of the PPHR antenna. We investigate the noise temperature and gain of the mixer over 642-714 GHz, and analyze the experimental results using rigorous theories that were developed specifically for the purpose. Our investigation demonstrates that finline mixers have good performance both below and above the superconducting energy gap.
IEEE Transactions on Microwave Theory and Techniques 11/2004; · 1.85 Impact Factor
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A. C. Taylor,
A. Challinor,
D. Goldie,
K. Grainge,
M. E. Jones,
A. N. Lasenby,
S. Withington, G. Yassin,
W. K. Gear,
L. Piccirillo,
P. Ade,
P. D. Mauskopf,
B. Maffei,
G. Pisano
[show abstract]
[hide abstract]
ABSTRACT: We describe the design and expected performance of Clover, a new instrument designed to measure the B-mode polarization of the cosmic microwave background. The proposed instrument will comprise three independent telescopes operating at 90, 150 and 220 GHz and is planned to be sited at Dome C, Antarctica. Each telescope will feed a focal plane array of 128 background-limited detectors and will measure polarized signals over angular multipoles 20 < l < 1000. The unique design of the telescope and careful control of systematics should enable the B-mode signature of gravitational waves to be measured to a lensing-confusion-limited tensor-to-scalar ratio r~0.005.
08/2004;
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[show abstract]
[hide abstract]
ABSTRACT: When designing instruments for submillimeter-wave astronomy it is important to understand precisely how saturating superconducting tunnel-junction mixers behave. In this article, a procedure is described for calculating the behavior of tunnel-junction circuits when multitone high-level signals are applied. The procedure is based on a full quantum-mechanical description of photon-assisted tunneling, and uses Harmonic Newton to search for a set of voltages and currents that satisfy the circuit equations at every frequency present. A number of illustrative simulations are presented, and it is shown that Harmonic Newton can be used to model saturating superconductor–insulator–superconductor mixers in a robust and numerically efficient manner. © 2003 American Institute of Physics.
Journal of Applied Physics 06/2003; 93(12):9812-9822. · 2.17 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: The feasibility of making single-chip, superconducting detectors for submillimetre-wave astronomical inteferometry is demonstrated. An experimental device based on back-to-back corrugated horns, and back-to-back finline transitions, was fabricated. The detector was illuminated at 350 GHz, using a coherent laboratory source, and 0.6° fringes were measured.
Electronics Letters 05/2003; · 0.96 Impact Factor
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03/2003; -1:353.
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[show abstract]
[hide abstract]
ABSTRACT: We present the design of a novel two-element horn-reflector
antenna, which has been used on an interferometer built for studying the
anisotropy in the cosmic microwave background at an angular scale of
≈2° and a frequency of 33 GHz. The design consists of a pair of
closely packed parabolic mirrors fed by two rectangular corrugated
horns, each at an offset angle of 75° to the axis of its mirror. The
offset angle and the horn-reflector dimensions were chosen so that the
antenna has elliptical primary beams producing a synthesized beam with
circular lobes. We have designed and tested the radiation pattern of the
individual antennas and the performance of the interferometer using
bright radio sources. Our measurements revealed that the individual
antennas have low sidelobes and that the crosstalk between the two
elements of the interferometer is less than -80 dB. We therefore
conclude that this design is suitable for the required astronomical
application
IEEE Transactions on Antennas and Propagation 03/2002; · 2.15 Impact Factor
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Low Temperature Electronics, 2002. Proceedings of the 5th European Workshop on; 02/2002
