441 research outputs found
Multi-mode TES bolometer optimization for the LSPE-SWIPE instrument
In this paper we explore the possibility of using transition edge sensor
(TES) detectors in multi-mode configuration in the focal plane of the Short
Wavelength Instrument for the Polarization Explorer (SWIPE) of the
balloon-borne polarimeter Large Scale Polarization Explorer (LSPE) for the
Cosmic Microwave Background (CMB) polarization. This study is motivated by the
fact that maximizing the sensitivity of TES bolometers, under the augmented
background due to the multi-mode design, requires a non trivial choice of
detector parameters. We evaluate the best parameter combination taking into
account scanning strategy, noise constraints, saturation power and operating
temperature of the cryostat during the flight.Comment: in Journal of Low Temperature Physics, 05 January 201
Cosmic Microwave Background Temperature at Galaxy Clusters
We have deduced the cosmic microwave background (CMB) temperature in the Coma
cluster (A1656, ), and in A2163 () from spectral
measurements of the Sunyaev-Zel'dovich (SZ) effect over four passbands at radio
and microwave frequencies. The resulting temperatures at these redshifts are
K and K, respectively. These values confirm the expected
relation , where K is the value
measured by the COBE/FIRAS experiment. Alternative scaling relations that are
conjectured in non-standard cosmologies can be constrained by the data; for
example, if or , then
and (at 95% confidence). We
briefly discuss future prospects for more precise SZ measurements of at
higher redshifts.Comment: 13 pages, 1 figure, ApJL accepted for publicatio
Absolute calibration and beam reconstruction of MITO (a ground-based instrument in the millimetric region)
An efficient sky data reconstruction derives from a precise characterization
of the observing instrument. Here we describe the reconstruction of
performances of a single-pixel 4-band photometer installed at MITO (Millimeter
and Infrared Testagrigia Observatory) focal plane. The strategy of differential
sky observations at millimeter wavelengths, by scanning the field of view at
constant elevation wobbling the subreflector, induces a good knowledge of beam
profile and beam-throw amplitude, allowing efficient data recovery. The
problems that arise estimating the detectors throughput by drift scanning on
planets are shown. Atmospheric transmission, monitored by skydip technique, is
considered for deriving final responsivities for the 4 channels using planets
as primary calibrators.Comment: 14 pages, 6 fiugres, accepted for pubblication by New Astronomy (25
March
Triple Experiment Spectrum of the Sunyaev-Zeldovich Effect in the Coma Cluster: H_0
The Sunyaev-Zeldovich (SZ) effect was previously measured in the Coma cluster
by the Owens Valley Radio Observatory and Millimeter and IR Testa Grigia
Observatory experiments and recently also with the Wilkinson Microwave
Anisotropy Probe satellite. We assess the consistency of these results and
their implications on the feasibility of high-frequency SZ work with
ground-based telescopes. The unique data set from the combined measurements at
six frequency bands is jointly analyzed, resulting in a best-fit value for the
Thomson optical depth at the cluster center, tau_{0}=(5.35 \pm 0.67) 10^{-3}.
The combined X-ray and SZ determined properties of the gas are used to
determine the Hubble constant. For isothermal gas with a \beta density profile
we derive H_0 = 84 \pm 26 km/(s\cdot Mpc); the (1\sigma) error includes only
observational SZ and X-ray uncertainties.Comment: 11 pages, 1 figur
Atomic layer deposition of Ru from CpRu(CO2)Et using O2 gas and O2 plasma
The metalorganic precursor cyclopentadienylethyl(dicarbonyl)ruthenium (CpRu(CO)2Et) was used to develop an atomic layer deposition (ALD) process for ruthenium. O2 gas and O2 plasma were employed as reactants. For both processes, thermal and plasma-assisted ALD, a relatively high growth-per-cycle of - 1 Å was obtained. The Ru films were dense and polycrystalline, regardless of the reactant, yielding a resistivity of - 16 µO¿cm. The O2 plasma not only enhanced the Ru nucleation on the TiN substrates but also led to an increased roughness compared to thermal ALD
MAD-4-MITO, a Multi Array of Detectors for ground-based mm/submm SZ observations
The last few years have seen a large development of mm technology and
ultra-sensitive detectors devoted to microwave astronomy and astrophysics. The
possibility to deal with large numbers of these detectors assembled into
multi--pixel imaging systems has greatly improved the performance of microwave
observations, even from ground--based stations, especially combining the power
of multi--band detectors with their new imaging capabilities. Hereafter, we
will present the development of a multi--pixel solution devoted to
Sunyaev--Zel'dovich observations from ground--based telescopes, that is going
to be operated from the Millimetre and Infrared Testagrigia Observatory.Comment: 5 pages, 3 figures, to be published in th eProceedings of the 2K1BC
Workshop, July 9-13, 2001 - Breuil-Cervini
Kinetic Inductance Detectors for the OLIMPO experiment: design and pre-flight characterization
We designed, fabricated, and characterized four arrays of horn--coupled,
lumped element kinetic inductance detectors (LEKIDs), optimized to work in the
spectral bands of the balloon-borne OLIMPO experiment. OLIMPO is a 2.6 m
aperture telescope, aimed at spectroscopic measurements of the
Sunyaev-Zel'dovich (SZ) effect. OLIMPO will also validate the LEKID technology
in a representative space environment. The corrected focal plane is filled with
diffraction limited horn-coupled KID arrays, with 19, 37, 23, 41 active pixels
respectively at 150, 250, 350, and 460GHz. Here we report on the full
electrical and optical characterization performed on these detector arrays
before the flight. In a dark laboratory cryostat, we measured the resonator
electrical parameters, such as the quality factors and the electrical
responsivities, at a base temperature of 300mK. The measured average
resonator s are 1.7, 7.0, 1.0, and
1.0 for the 150, 250, 350, and 460GHz arrays, respectively.
The average electrical phase responsivities on resonance are 1.4rad/pW,
1.5rad/pW, 2.1rad/pW, and 2.1rad/pW; the electrical noise
equivalent powers are 45, 160,
80, and 140, at 12 Hz. In the OLIMPO
cryostat, we measured the optical properties, such as the noise equivalent
temperatures (NET) and the spectral responses. The measured NETs are
, , ,
and , at 12 Hz; under 78, 88, 92, and 90 mK
Rayleigh-Jeans blackbody load changes respectively for the 150, 250, 350, and
460 GHz arrays. The spectral responses were characterized with the OLIMPO
differential Fourier transform spectrometer (DFTS) up to THz frequencies, with
a resolution of 1.8 GHz.Comment: Published on JCA
Redshift Dependence of the CMB Temperature from S-Z Measurements
We have determined the CMB temperature, , at redshifts in the range
0.023-0.546, from multi-frequency measurements of the S-Z effect towards 13
clusters. We extract the parameter in the redshift scaling
, which contrasts the prediction of the standard
model () with that in non-adiabatic evolution conjectured in some
alternative cosmological models. The statistical analysis is based on two main
approaches: using ratios of the S-Z intensity change, , thus taking
advantage of the weak dependence of the ratios on IC gas properties, and using
directly the measurements. In the former method dependence on the
Thomson optical depth and gas temperature is only second order in these
quantities. In the second method we marginalize over these quantities which
appear to first order in the intensity change. The marginalization itself is
done in two ways - by direct integrations, and by a Monte Carlo Markov Chain
approach. Employing these different methods we obtain two sets of results that
are consistent with , in agreement with the prediction of the
standard model.Comment: Accepted for publication in Ap
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