S. J. Melhuish

The University of Manchester, Manchester, ENG, United Kingdom

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Publications (41)143.13 Total impact

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    ABSTRACT: The QUIJOTE (Q-U-I JOint Tenerife) CMB Experiment is designed to observe the polarization of the Cosmic Microwave Background and other Galactic and extragalactic signals at medium and large angular scales in the frequency range of 10-40 GHz. The first of the two QUIJOTE telescopes and the multi-frequency (10-20 GHz) instrument have been in operation since November 2012. In 2014 a second telescope and a new instrument at 30GHz will be ready for commissioning, and an additional instrument at 40 GHz is in its final design stages. After three years of effective observations, the data obtained by these telescopes and instruments will have the required sensitivity to detect a primordial gravitational-wave component if the tensor-to-scalar ratio is larger than r = 0.05. At the moment, we have completed half of the wide Galactic survey with the multi-frequency instrument covering 18 000 square degrees of the Northern hemisphere. When we finish this survey in early 2014, we shall have reached approximately 14{\mu}K per one degree beam at 11, 13, 17 and 19 GHz, in both Q and U.
    01/2014;
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    Mark A. McCulloch, Simon J. Melhuish, Lucio Piccirillo
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    ABSTRACT: In this paper a new design of MMIC based LNA is outlined. This design uses a discrete 100-nm InP HEMT placed in front of an existing InP MMIC LNA to lower the overall noise temperature of the LNA. This new approach known as the Transistor in front of MMIC (T+MMIC) LNA, possesses a gain in excess of 40dB and an average noise temperature of 9.4K compared to 14.5K for the equivalent MMIC-only LNA measured across a 27-33GHz bandwidth at a physical temperature of 8K. A simple ADS model offering further insights into the operation of the LNA is also presented and a potential radio astronomy application is discussed
    10/2013;
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    Simon J. Melhuish, Lorenzo Martinis, Lucio Piccirillo
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    ABSTRACT: We present a 3He / 4He dilution refrigerator designed for cooling astronomical mm-wave telescope receivers to around 100 mK. Used in combination with a Gi?fford-McMahon closed-cycle refrigerator, 4He and 3He sorption-pumped refrigerators, our cryogen-free system is capable of achieving 2 microW cooling power at 87 mK. A receiver attached directly to the telescope optics is required to rotate with respect to the downward direction. This scenario, of variable tilt, has proved difficult for typical dilution refrigerators, but our design has a geometry chosen to allow tilt to 45 degrees and beyond.
    Cryogenics 12/2012; s 55–56. · 1.17 Impact Factor
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    ABSTRACT: We present the designs for and the results of a prototype cryogenic Ka-band low noise amplifier (LNA), that is based on the hybridization of microwave integrated circuits (MICs) and monolithic microwave integrated circuits (MMICs). The resulting transistor plus MMIC (T+MMIC) 5 stage LNA, has a peak gain of 52dB, a minimum noise temperature of 12K at an ambient temperature of ≈23K, and a 20% bandwidth of 27-33GHz. We outline the background behind the LNA, our measurement process, the LNA's performance, our future development plans and discuss the possible advantages that this amplifier layout may offer.
    Microwave Conference (EuMC), 2012 42nd European; 01/2012
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    ABSTRACT: We present the designs for and the results of a prototype cryogenic Ka-band low noise amplifier (LNA), that is based on the hybridization of microwave integrated circuits (MICs) and monolithic microwave integrated circuits (MMICs). The resulting transistor plus MMIC (T+MMIC) 5 stage LNA, has a peak gain of 52dB, a minimum noise temperature of 12K at an ambient temperature of ≈23K, and a 20% bandwidth of 27-33GHz. We outline the background behind the LNA, our measurement process, the LNA's performance, our future development plans and discuss the possible advantages that this amplifier layout may offer.
    Microwave Integrated Circuits Conference (EuMIC), 2012 7th European; 01/2012
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    ABSTRACT: We present early results of noise temperature measurements made on a Planck LFI EBB Ka-band low noise amplifier at physical temperatures as low as 1.5 K. This temperature is an order of magnitude lower than typically used on radio astronomy receiver systems. The results are tentatively compared with semi-empirical predictions made by Pospieszalski.
    Microwave Integrated Circuits Conference (EuMIC), 2012 7th European; 01/2012
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    ABSTRACT: We present a 82-100 GHz circular waveguide polarization rotator based on a broadband rotating half-wave retarder. The device was designed for astrophysics experiments aimed to characterize the polarization of the cosmic microwave background radiation. The device is based on a Pancharatnam recipe used in optics and has a very low intrinsic cross polarization, very flat phase response across the band and very low losses. It can be used in astronomical experiments where very high performance is required but also as a variable polarization source for instrument calibrations. The design was manufactured and then tested using a millimeter-wave vector network analyzer. The average measured RL, IL and cross polarization across a 30% bandwidth were, respectively, -38 dB, -0.27 dB, and -36.5 dB.
    IEEE Microwave and Wireless Components Letters 04/2011; · 1.78 Impact Factor
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    ABSTRACT: We present a catalog of compact sources derived from the QUaD Galactic Plane Survey. The survey covers ~800 square degrees of the inner galaxy (|b|<4 degrees) in Stokes I, Q and U parameters at 100 and 150 GHz, with angular resolution 5 and 3.5 arcminutes. 505 unique sources are identified in I, of which 239 are spatially matched between frequency bands, with 50 (216) detected at 100 (150) GHz alone; 182 sources are identified as ultracompact HII (UCHII) regions. Approximating the distribution of total intensity source fluxes as a power-law, we find a slope of $\gamma_{S,100}=-1.8\pm0.4$ at 100 GHz, and $\gamma_{S,150}=-2.2\pm0.4$ at 150 GHz. Similarly, the power-law index of the source two-point angular correlation function is $\gamma_{\theta,100}=-1.21\pm0.04$ and $\gamma_{\theta,150}=-1.25\pm0.04$. The total intensity spectral index distribution peaks at $\alpha_{I}\sim0.25$, indicating that dust emission is not the only source of radiation produced by these objects between 100 and 150 GHz; free-free radiation is likely significant in the 100 GHz band. Four sources are detected in polarized intensity P, of which three have matching counterparts in I. Three of the polarized sources lie close to the galactic center, Sagittarius A*, Sagittarius B2 and the Galactic Radio Arc, while the fourth is RCW 49, a bright HII region. An extended polarized source, undetected by the source extraction algorithm on account of its $\sim0.5^{\circ}$ size, is identified visually, and is an isolated example of large-scale polarized emission oriented distinctly from the bulk galactic dust polarization. Comment: 30 pages, 19 figures, two catalogs; submitted to ApJS; maps and catalogs downloadable from <http://find.spa.umn.edu/quad/quad_galactic>
    The Astrophysical Journal Supplement Series 01/2011; 195(1). · 16.24 Impact Factor
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    ABSTRACT: We present a survey of ~800 deg2 of the galactic plane observed with the QUaD telescope. The primary products of the survey are maps of Stokes I, Q, and U parameters at 100 and 150 GHz, with spatial resolution of 5' and 35, respectively. Two regions are covered, spanning approximately 245°-295° and 315°-5° in the galactic longitude l and –4° < b < +4° in the galactic latitude b. At 002 square pixel size, the median sensitivity is 74 and 107 kJy sr–1 at 100 GHz and 150 GHz respectively in I, and 98 and 120 kJy sr–1 for Q and U. In total intensity, we find an average spectral index of α = 2.35 ± 0.01(stat) ± 0.02(sys) for |b| ≤ 1°, indicative of emission components other than thermal dust. A comparison to published dust, synchrotron, and free-free models implies an excess of emission in the 100 GHz QUaD band, while better agreement is found at 150 GHz. A smaller excess is observed when comparing QUaD 100 GHz data to the WMAP five-year W band; in this case, the excess is likely due to the wider bandwidth of QUaD. Combining the QUaD and WMAP data, a two-component spectral fit to the inner galactic plane (|b| ≤ 1°) yields mean spectral indices of α s = –0.32 ± 0.03 and α d = 2.84 ± 0.03; the former is interpreted as a combination of the spectral indices of synchrotron, free-free, and dust, while the second is largely attributed to the thermal dust continuum. In the same galactic latitude range, the polarization data show a high degree of alignment perpendicular to the expected galactic magnetic field direction, and exhibit mean polarization fraction 1.38 ± 0.08(stat) ± 0.1(sys)% at 100 GHz and 1.70 ± 0.06(stat) ± 0.1(sys)% at 150 GHz. We find agreement in polarization fraction between QUaD 100 GHz and the WMAP W band, the latter giving 1.1% ± 0.4%.
    The Astrophysical Journal 09/2010; 722(2):1057. · 6.73 Impact Factor
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    ABSTRACT: We evaluate the contribution of cosmic microwave background (CMB) polarization spectra to cosmological parameter constraints. We produce cosmological parameters using high-quality CMB polarization data from the ground-based QUaD experiment and demonstrate for the majority of parameters that there is significant improvement on the constraints obtained from satellite CMB polarization data. We split a multi-experiment CMB dataset into temperature and polarization subsets and show that the best-fit confidence regions for the LCDM 6-parameter cosmological model are consistent with each other, and that polarization data reduces the confidence regions on all parameters. We provide the best limits on parameters from QUaD EE/BB polarization data and we find best-fit parameters from the multi-experiment CMB dataset using the optimal pivot scale of k_p=0.013 Mpc-1 to be {omch2, ombh2, H_0, A_s, n_s, tau}= {0.113, 0.0224, 70.6, 2.29 times 10^-9, 0.960, 0.086}. Comment: 7 pages, 5 figures, updated to reflect published version, minor changes to spelling and format
    The Astrophysical Journal 06/2010; 716(2):1040-1046. · 6.73 Impact Factor
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    ABSTRACT: Centaurus (Cen) A represents one of the best candidates for an isolated, compact, highly polarized source that is bright at typical cosmic microwave background (CMB) experiment frequencies. We present measurements of the 4 degree by 2 degree region centered on Cen A with QUaD, a CMB polarimeter whose absolute polarization angle is known to 0.5 degrees. Simulations are performed to assess the effect of misestimation of the instrumental parameters on the final measurement and systematic errors due to the field's background structure and temporal variability from Cen A's nuclear region are determined. The total (Q, U) of the inner lobe region is (1.00 +/- 0.07 (stat.) +/- 0.04 (sys.), -1.72 +/- 0.06 +/- 0.05) Jy at 100 GHz and (0.80 +/- 0.06 +/- 0.06, -1.40 +/- 0.07 +/- 0.08) Jy at 150 GHz, leading to polarization angles and total errors of -30.0 +/- 1.1 degrees and -29.1 +/- 1.7 degrees. These measurements will allow the use of Cen A as a polarized calibration source for future millimeter experiments. Comment: 9 pages, 8 figures, v2 matches version published in ApJ
    The Astrophysical Journal 02/2010; 710(2):1541. · 6.73 Impact Factor
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    ABSTRACT: We present a set of techniques and materials we are currently developing which enable very broadband and highly effective optical devices in the spectral region from 20 GHz to 20 THz. Many of these devices have already been employed in terrestrial, airborne and space based telescope systems.
    12/2009;
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    ABSTRACT: We present an improved analysis of the final data set from the QUaD experiment. Using an improved technique to remove ground contamination, we double the effective sky area and hence increase the precision of our cosmic microwave background (CMB) power spectrum measurements by ~30% versus that previously reported. In addition, we have improved our modeling of the instrument beams and have reduced our absolute calibration uncertainty from 5% to 3.5% in temperature. The robustness of our results is confirmed through extensive jackknife tests, and by way of the agreement that we find between our two fully independent analysis pipelines. For the standard six-parameter ΛCDM model, the addition of QUaD data marginally improves the constraints on a number of cosmological parameters over those obtained from the WMAP experiment alone. The impact of QUaD data is significantly greater for a model extended to include either a running in the scalar spectral index, or a possible tensor component, or both. Adding both the QUaD data and the results from the Arcminute Cosmology Bolometer Array Receiver experiment, the uncertainty in the spectral index running is reduced by ~25% compared to WMAP alone, while the upper limit on the tensor-to-scalar ratio is reduced from r < 0.48 to r < 0.33 (95% c.l.). This is the strongest limit on tensors to date from the CMB alone. We also use our polarization measurements to place constraints on parity-violating interactions to the surface of last scattering, constraining the energy scale of Lorentz violating interactions to <1.5 × 10–43 GeV (68% c.l.). Finally, we place a robust upper limit on the strength of the lensing B-mode signal. Assuming a single flat band power between ℓ = 200 and ℓ = 2000, we constrain the amplitude of B-modes to be <0.57 μK2 (95% c.l.).
    The Astrophysical Journal 10/2009; 705(1):978. · 6.73 Impact Factor
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    ABSTRACT: In this paper we present a parameter estimation analysis of the polarization and temperature power spectra from the second and third season of observations with the QUaD experiment. QUaD has for the first time detected multiple acoustic peaks in the E-mode polarization spectrum with high significance. Although QUaD-only parameter constraints are not competitive with previous results for the standard 6-parameter LCDM cosmology, they do allow meaningful polarization-only parameter analyses for the first time. In a standard 6-parameter LCDM analysis we find the QUaD TT power spectrum to be in good agreement with previous results. However, the QUaD polarization data shows some tension with LCDM. The origin of this 1 to 2 sigma tension remains unclear, and may point to new physics, residual systematics or simple random chance. We also combine QUaD with the five-year WMAP data set and the SDSS Luminous Red Galaxies 4th data release power spectrum, and extend our analysis to constrain individual isocurvature mode fractions, constraining cold dark matter density, alpha(cdmi)<0.11 (95 % CL), neutrino density, alpha(ndi)<0.26 (95 % CL), and neutrino velocity, alpha(nvi)<0.23 (95 % CL), modes. Our analysis sets a benchmark for future polarization experiments. Comment: 8 pages, 5 figures, submitted to ApJ
    The Astrophysical Journal 08/2009; 701(2):857-864. · 6.73 Impact Factor
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    ABSTRACT: We present measurements of the cosmic microwave background (CMB) radiation temperature anisotropy in the multipole range 2000<ell<3000 from the QUaD telescope's second and third observing seasons. After masking the brightest point sources our results are consistent with the primary LCDM expectation alone. We estimate the contribution of residual (un-masked) radio point sources using a model calibrated to our own bright source observations, and a full simulation of the source finding and masking procedure. Including this contribution slightly improves the chi^2. We also fit a standard SZ template to the bandpowers and see no strong evidence of an SZ contribution, which is as expected for sigma_8 approx 0.8. Comment: 5 pages, 5 figures, updated beam model, full data release available online (see text), accepted to ApJL
    The Astrophysical Journal Letters 08/2009; 700(2):L187-L191. · 6.35 Impact Factor
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    ABSTRACT: We constrain parity-violating interactions to the surface of last scattering using spectra from the QUaD experiment's second and third seasons of observations by searching for a possible systematic rotation of the polarization directions of cosmic microwave background photons. We measure the rotation angle due to such a possible "cosmological birefringence" to be 0.55 degrees +/-0.82 degrees (random) +/-0.5 degrees (systematic) using QUaD's 100 and 150 GHz temperature-curl and gradient-curl spectra over the spectra over the multipole range 200<l<2000, consistent with null, and constrain Lorentz-violating interactions to <2 x 10;{-43} GeV (68% confidence limit). This is the best constraint to date on electrodynamic parity violation on cosmological scales.
    Physical Review Letters 04/2009; 102(16):161302. · 7.73 Impact Factor
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    ABSTRACT: We report results from the second and third seasons of observation with the QUaD experiment. Angular power spectra of the cosmic microwave background are derived for both temperature and polarization at both 100 GHz and 150 GHz, and as cross-frequency spectra. All spectra are subjected to an extensive set of jackknife tests to probe for possible systematic contamination. For the implemented data cuts and processing technique such contamination is undetectable. We analyze the difference map formed between the 100 and 150 GHz bands and find no evidence of foreground contamination in polarization. The spectra are then combined to form a single set of results which are shown to be consistent with the prevailing LCDM model. The sensitivity of the polarization results is considerably better than that of any previous experiment—for the first time multiple acoustic peaks are detected in the E-mode power spectrum at high significance.
    The Astrophysical Journal 02/2009; 692(2):1247. · 6.73 Impact Factor
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    ABSTRACT: We describe the QUaD experiment, a millimeter-wavelength polarimeter designed to observe the cosmic microwave background (CMB) from a site at the South Pole. The experiment comprises a 2.64 m Cassegrain telescope equipped with a cryogenically cooled receiver containing an array of 62 polarization-sensitive bolometers. The focal plane contains pixels at two different frequency bands, 100 GHz and 150 GHz, with angular resolutions of 5' and 35, respectively. The high angular resolution allows observation of CMB temperature and polarization anisotropies over a wide range of scales. The instrument commenced operation in early 2005 and collected science data during three successive Austral winter seasons of observation.
    The Astrophysical Journal 02/2009; 692(2):1221. · 6.73 Impact Factor
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    ABSTRACT: QUaD is a bolometric CMB polarimeter sited at the South Pole, operating at frequencies of 100 and 150 GHz. In this paper we report preliminary results from the first season of operation (austral winter 2005). All six CMB power spectra are presented derived as cross spectra between the 100 and 150 GHz maps using 67 days of observation in a low foreground region of approximately 60 deg2. These data are a small fraction of the data acquired to date. The measured spectra are consistent with the ΛCDM cosmological model. We perform jackknife tests that indicate that the observed signal has negligible contamination from instrumental systematics. In addition, by using a frequency jackknife we find no evidence for foreground contamination.
    The Astrophysical Journal 12/2008; 674(1):22. · 6.73 Impact Factor
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    ABSTRACT: We describe a new high-sensitivity experiment for observing cosmic microwave background (CMB) anisotropies. The instrument is a two-element interferometer operating at 33 GHz with a ∼3 GHz bandwidth. It is installed on the high and dry Teide Observatory site on Tenerife where successful beam-switching observations have been made at this frequency. Two realizations of the interferometer have been tested with element separations of 11.9λ and 16.7λ. The resulting angular resolution of ∼2° was chosen to explore the amplitude of CMB structure on the large angular scale side of the Doppler (acoustic) peak. It is found that observations are unaffected by water vapour for more than 70 per cent of the time when the sensitivity is limited by the receiver noise alone. Observations over several months are expected to give an rms noise level of ∼10--20 2 μK covering ∼100 resolution elements. Preliminary results show stable operation of the interferometer with the detection of discrete radio sources as well as the Galactic plane at Dec. =+41° and −29°.
    Monthly Notices of the Royal Astronomical Society 09/2008; 305(2):399 - 408. · 5.52 Impact Factor

Publication Stats

417 Citations
143.13 Total Impact Points

Institutions

  • 1997–2012
    • The University of Manchester
      • • Jodrell Bank Centre for Astrophysics
      • • School of Physics and Astronomy
      Manchester, ENG, United Kingdom
  • 2004–2010
    • Cardiff University
      • School of Physics and Astronomy
      Cardiff, WLS, United Kingdom
    • University of Wales
      Cardiff, Wales, United Kingdom
  • 2009
    • Stanford University
      • Kavli Institute for Particle Physics and Cosmology (KIPAC)
      Stanford, CA, United States