36,329 research outputs found
A LEKID-based CMB instrument design for large-scale observations in Greenland
We present the results of a feasibility study, which examined deployment of a
ground-based millimeter-wave polarimeter, tailored for observing the cosmic
microwave background (CMB), to Isi Station in Greenland. The instrument for
this study is based on lumped-element kinetic inductance detectors (LEKIDs) and
an F/2.4 catoptric, crossed-Dragone telescope with a 500 mm aperture. The
telescope is mounted inside the receiver and cooled to K by a
closed-cycle He refrigerator to reduce background loading on the detectors.
Linearly polarized signals from the sky are modulated with a metal-mesh
half-wave plate that is rotated at the aperture stop of the telescope with a
hollow-shaft motor based on a superconducting magnetic bearing. The modular
detector array design includes at least 2300 LEKIDs, and it can be configured
for spectral bands centered on 150~GHz or greater. Our study considered
configurations for observing in spectral bands centered on 150, 210 and
267~GHz. The entire polarimeter is mounted on a commercial precision rotary air
bearing, which allows fast azimuth scan speeds with negligible vibration and
mechanical wear over time. A slip ring provides power to the instrument,
enabling circular scans (360 degrees of continuous rotation). This mount, when
combined with sky rotation and the latitude of the observation site, produces a
hypotrochoid scan pattern, which yields excellent cross-linking and enables
34\% of the sky to be observed using a range of constant elevation scans. This
scan pattern and sky coverage combined with the beam size (15~arcmin at
150~GHz) makes the instrument sensitive to in the angular
power spectra
BICEP2 II: Experiment and Three-Year Data Set
We report on the design and performance of the BICEP2 instrument and on its
three-year data set. BICEP2 was designed to measure the polarization of the
cosmic microwave background (CMB) on angular scales of 1 to 5 degrees
(=40-200), near the expected peak of the B-mode polarization signature of
primordial gravitational waves from cosmic inflation. Measuring B-modes
requires dramatic improvements in sensitivity combined with exquisite control
of systematics. The BICEP2 telescope observed from the South Pole with a 26~cm
aperture and cold, on-axis, refractive optics. BICEP2 also adopted a new
detector design in which beam-defining slot antenna arrays couple to
transition-edge sensor (TES) bolometers, all fabricated on a common substrate.
The antenna-coupled TES detectors supported scalable fabrication and
multiplexed readout that allowed BICEP2 to achieve a high detector count of 500
bolometers at 150 GHz, giving unprecedented sensitivity to B-modes at degree
angular scales. After optimization of detector and readout parameters, BICEP2
achieved an instrument noise-equivalent temperature of 15.8 K sqrt(s). The
full data set reached Stokes Q and U map depths of 87.2 nK in square-degree
pixels (5.2 K arcmin) over an effective area of 384 square degrees within
a 1000 square degree field. These are the deepest CMB polarization maps at
degree angular scales to date. The power spectrum analysis presented in a
companion paper has resulted in a significant detection of B-mode polarization
at degree scales.Comment: 30 pages, 24 figure
ACBAR: The Arcminute Cosmology Bolometer Array Receiver
We describe the Arcminute Cosmology Bolometer Array Receiver (ACBAR); a
multifrequency millimeter-wave receiver designed for observations of the Cosmic
Microwave Background (CMB) and the Sunyaev-Zel'dovich effect in clusters of
galaxies. The ACBAR focal plane consists of a 16-pixel, background-limited, 240
mK bolometer array that can be configured to observe simultaneously at 150,
220, 280, and 350 GHz. With 4-5' FWHM Gaussian beam sizes and a 3 degree
azimuth chop, ACBAR is sensitive to a wide range of angular scales. ACBAR was
installed on the 2 m Viper telescope at the South Pole in January 2001. We
describe the design of the instrument and its performance during the 2001 and
2002 observing seasons.Comment: 59 pages, 16 figures -- updated to reflect version published in ApJ
The BOOMERANG North America Instrument: a balloon-borne bolometric radiometer optimized for measurements of cosmic background radiation anisotropies from 0.3 to 4 degrees
We describe the BOOMERANG North America (BNA) instrument, a balloon-borne
bolometric radiometer designed to map the Cosmic Microwave Background (CMB)
radiation with 0.3 deg resolution over a significant portion of the sky. This
receiver employs new technologies in bolometers, readout electronics,
millimeter-wave optics and filters, cryogenics, scan and attitude
reconstruction. All these subsystems are described in detail in this paper. The
system has been fully calibrated in flight using a variety of techniques which
are described and compared. It has been able to obtain a measurement of the
first peak in the CMB angular power spectrum in a single balloon flight, few
hours long, and was a prototype of the BOOMERANG Long Duration Balloon (BLDB)
experiment.Comment: 40 pages, 22 figures, submitted to Ap
Ultra High Energy Cosmology with POLARBEAR
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.Comment: 8 pages, 6 figures, DPF 2011 conference proceeding
The AzTEC mm-Wavelength Camera
AzTEC is a mm-wavelength bolometric camera utilizing 144 silicon nitride
micromesh detectors. Herein we describe the AzTEC instrument architecture and
its use as an astronomical instrument. We report on several performance metrics
measured during a three month observing campaign at the James Clerk Maxwell
Telescope, and conclude with our plans for AzTEC as a facility instrument on
the Large Millimeter Telescope.Comment: 13 pages, 15 figures, accepted for publication in Monthly Notice
Instrumental performance and results from testing of the BLAST-TNG receiver, submillimeter optics, and MKID arrays
Polarized thermal emission from interstellar dust grains can be used to map
magnetic fields in star forming molecular clouds and the diffuse interstellar
medium (ISM). The Balloon-borne Large Aperture Submillimeter Telescope for
Polarimetry (BLASTPol) flew from Antarctica in 2010 and 2012 and produced
degree-scale polarization maps of several nearby molecular clouds with
arcminute resolution. The success of BLASTPol has motivated a next-generation
instrument, BLAST-TNG, which will use more than 3000 linear polarization
sensitive microwave kinetic inductance detectors (MKIDs) combined with a 2.5m
diameter carbon fiber primary mirror to make diffraction-limited observations
at 250, 350, and 500 m. With 16 times the mapping speed of BLASTPol,
sub-arcminute resolution, and a longer flight time, BLAST-TNG will be able to
examine nearby molecular clouds and the diffuse galactic dust polarization
spectrum in unprecedented detail. The 250 m detector array has been
integrated into the new cryogenic receiver, and is undergoing testing to
establish the optical and polarization characteristics of the instrument.
BLAST-TNG will demonstrate the effectiveness of kilo-pixel MKID arrays for
applications in submillimeter astronomy. BLAST-TNG is scheduled to fly from
Antarctica in December 2017 for 28 days and will be the first balloon-borne
telescope to offer a quarter of the flight for "shared risk" observing by the
community.Comment: Presented at SPIE Millimeter, Submillimeter, and Far-Infrared
Detectors and Instrumentation for Astronomy VIII, June 29th, 201
Antenna-coupled TES bolometers used in BICEP2, Keck array, and SPIDER
We have developed antenna-coupled transition-edge sensor (TES) bolometers for
a wide range of cosmic microwave background (CMB) polarimetry experiments,
including BICEP2, Keck Array, and the balloon borne SPIDER. These detectors
have reached maturity and this paper reports on their design principles,
overall performance, and key challenges associated with design and production.
Our detector arrays repeatedly produce spectral bands with 20%-30% bandwidth at
95, 150, or 220~GHz. The integrated antenna arrays synthesize symmetric
co-aligned beams with controlled side-lobe levels. Cross-polarized response on
boresight is typically ~0.5%, consistent with cross-talk in our multiplexed
readout system. End-to-end optical efficiencies in our cameras are routinely
35% or higher, with per detector sensitivities of NET~300 uKrts. Thanks to the
scalability of this design, we have deployed 2560 detectors as 1280 matched
pairs in Keck Array with a combined instantaneous sensitivity of ~9 uKrts, as
measured directly from CMB maps in the 2013 season. Similar arrays have
recently flown in the SPIDER instrument, and development of this technology is
ongoing.Comment: 16 pgs, 20 fig
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