77 research outputs found
Millimeter-Wave Polarimeters Using Kinetic Inductance Detectors for TolTEC and Beyond
Microwave Kinetic Inductance Detectors (MKIDs) provide a compelling path
forward to the large-format polarimeter, imaging, and spectrometer arrays
needed for next-generation experiments in millimeter-wave cosmology and
astronomy. We describe the development of feedhorn-coupled MKID detectors for
the TolTEC millimeter-wave imaging polarimeter being constructed for the
50-meter Large Millimeter Telescope (LMT). Observations with TolTEC are planned
to begin in early 2019. TolTEC will comprise 7,000 polarization sensitive
MKIDs and will represent the first MKID arrays fabricated and deployed on
monolithic 150 mm diameter silicon wafers -- a critical step towards future
large-scale experiments with over detectors. TolTEC will operate in
observational bands at 1.1, 1.4, and 2.0 mm and will use dichroic filters to
define a physically independent focal plane for each passband, thus allowing
the polarimeters to use simple, direct-absorption inductive structures that are
impedance matched to incident radiation. This work is part of a larger program
at NIST-Boulder to develop MKID-based detector technologies for use over a wide
range of photon energies spanning millimeter-waves to X-rays. We present the
detailed pixel layout and describe the methods, tools, and flexible design
parameters that allow this solution to be optimized for use anywhere in the
millimeter and sub-millimeter bands. We also present measurements of prototype
devices operating in the 1.1 mm band and compare the observed optical
performance to that predicted from models and simulations.Comment: 7 pages, 4 figures, 1 table. Submitted to Journal of Low Temperature
Physic
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
The relation between the column density structures and the magnetic field orientation in the Vela C molecular complex
We statistically evaluated the relative orientation between gas column density structures, inferred from Herschel submillimetre observations, and the magnetic field projected on the plane of sky, inferred from polarized thermal emission of Galactic dust observed by the Balloon-borne Large-Aperture Submillimetre Telescope for Polarimetry (BLASTPol) at 250, 350, and 500 μm, towards the Vela C molecular complex. First, we find very good agreement between the polarization orientations in the three wavelength-bands, suggesting that, at the considered common angular resolution of 3.0 that corresponds to a physical scale of approximately 0.61 pc, the inferred magnetic field orientation is not significantly affected by temperature or dust grain alignment effects. Second, we find that the relative orientation between gas column density structures and the magnetic field changes progressively with increasing gas column density, from mostly parallel or having no preferred orientation at low column densities to mostly perpendicular at the highest column densities. This observation is in agreement with previous studies by the Planck collaboration towards more nearby molecular clouds. Finally, we find a correspondence between (a) the trends in relative orientation between the column density structures and the projected magnetic field; and (b) the shape of the column density probability distribution functions (PDFs). In the sub-regions of Vela C dominated by one clear filamentary structure, or "ridges", where the high-column density tails of the PDFs are flatter, we find a sharp transition from preferentially parallel or having no preferred relative orientation at low column densities to preferentially perpendicular at highest column densities. In the sub-regions of Vela C dominated by several filamentary structures with multiple orientations, or "nests", where the maximum values of the column density are smaller than in the ridge-like sub-regions and the high-column density tails of the PDFs are steeper, such a transition is also present, but it is clearly less sharp than in the ridge-like sub-regions. Both of these results suggest that the magnetic field is dynamically important for the formation of density structures in this region
The Balloon-Borne Large Aperture Submillimeter Telescope Observatory
The BLAST Observatory is a proposed superpressure balloon-borne polarimeter
designed for a future ultra-long duration balloon campaign from Wanaka, New
Zealand. To maximize scientific output while staying within the stringent
superpressure weight envelope, BLAST will feature new 1.8m off-axis optical
system contained within a lightweight monocoque structure gondola. The payload
will incorporate a 300L He cryogenic receiver which will cool 8,274
microwave kinetic inductance detectors (MKIDs) to 100mK through the use of an
adiabatic demagnetization refrigerator (ADR) in combination with a He
sorption refrigerator all backed by a liquid helium pumped pot operating at 2K.
The detector readout utilizes a new Xilinx RFSOC-based system which will run
the next-generation of the BLAST-TNG KIDPy software. With this instrument we
aim to answer outstanding questions about dust dynamics as well as provide
community access to the polarized submillimeter sky made possible by
high-altitude observing unrestricted by atmospheric transmission. The BLAST
Observatory is designed for a minimum 31-day flight of which 70 will be
dedicated to observations for BLAST scientific goals and the remaining 30
will be open to proposals from the wider astronomical community through a
shared-risk proposals program.Comment: Presented at SPIE Ground-based and Airborne Telescopes VIII, December
13-18, 202
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