219 research outputs found
WSPEC: A waveguide filter-bank focal plane array spectrometer for millimeter wave astronomy and cosmology
Imaging and spectroscopy at (sub-)millimeter wavelengths are key frontiers in
astronomy and cosmology. Large area spectral surveys with moderate spectral
resolution (R=50-200) will be used to characterize large scale structure and
star formation through intensity mapping surveys in emission lines such as the
CO rotational transitions. Such surveys will also be used to study the SZ
effect, and will detect the emission lines and continuum spectrum of individual
objects. WSPEC is an instrument proposed to target these science goals. It is a
channelizing spectrometer realized in rectangular waveguide, fabricated using
conventional high-precision metal machining. Each spectrometer is coupled to
free space with a machined feed horn, and the devices are tiled into a 2D array
to fill the focal plane of the telescope. The detectors will be aluminum
Lumped-Element Kinetic Inductance Detectors (LEKIDs). To target the CO lines
and SZ effect, we will have bands at 135-175 GHz and 190-250 GHz, each
Nyquist-sampled at R~200 resolution. Here we discuss the instrument concept and
design, and successful initial testing of a WR10 (i.e. 90 GHz) prototype
spectrometer. We recently tested a WR5 (180 GHz) prototype to verify that the
concept works at higher frequencies, and also designed a resonant backshort
structure that may further increase the optical efficiency. We are making
progress towards integrating a spectrometer with a LEKID array and deploying a
prototype device to a telescope for first light.Comment: 7 pages, 4 figures, submitted to Journal of Low Temperature Physic
Magnetic field dependence of the internal quality factor and noise performance of lumped-element kinetic inductance detectors
We present a technique for increasing the internal quality factor of kinetic
inductance detectors (KIDs) by nulling ambient magnetic fields with a properly
applied magnetic field. The KIDs used in this study are made from thin-film
aluminum, they are mounted inside a light-tight package made from bulk
aluminum, and they are operated near . Since the thin-film
aluminum has a slightly elevated critical temperature (), it therefore transitions before the package (), which also serves as a magnetic shield. On cooldown, ambient
magnetic fields as small as approximately can produce
vortices in the thin-film aluminum as it transitions because the bulk aluminum
package has not yet transitioned and therefore is not yet shielding. These
vortices become trapped inside the aluminum package below
and ultimately produce low internal quality factors in the thin-film
superconducting resonators. We show that by controlling the strength of the
magnetic field present when the thin film transitions, we can control the
internal quality factor of the resonators. We also compare the noise
performance with and without vortices present, and find no evidence for excess
noise beyond the increase in amplifier noise, which is expected with increasing
loss.Comment: 5 pages, 4 figure
Far infrared polarimeter with very low instrumental polarization
After a short analysis of the main problems involved in the construction of a
Far Infrared polarimeter with very low instrumental noise, we describe the
instrument that will be employed at MITO telescope to search for calibration
sources and investigate polarization near the CMB anisotropy peaks in the next
campaign (Winter 2002-03).Comment: 9 pages, 5 figures, to appear in SPIE conference proceedings
"Astronomical telescopes and instrumentation
A millimeter-wave kinetic inductance detector camera for long-range imaging through optical obscurants
Millimeter-wave imaging provides a promising option for long-range target detection through optical obscurants such as fog, which often occur in marine environments. Given this motivation, we are currently developing a 150 GHz polarization-sensitive imager using a relatively new type of superconducting pair-breaking detector, the kinetic inductance detector (KID). This imager will be paired with a 1.5 m telescope to obtain an angular resolution of 0.09° over a 3.5° field of view using 3,840 KIDs. We have fully characterized a prototype KID array, which shows excellent performance with noise strongly limited by the irreducible fluctuations from the ambient temperature background. Full-scale KID arrays are now being fabricated and characterized for a planned demonstration in a maritime environment later this year
MKID development for SuperSpec: an on-chip, mm-wave, filter-bank spectrometer
SuperSpec is an ultra-compact spectrometer-on-a-chip for millimeter and
submillimeter wavelength astronomy. Its very small size, wide spectral
bandwidth, and highly multiplexed readout will enable construction of powerful
multibeam spectrometers for high-redshift observations. The spectrometer
consists of a horn-coupled microstrip feedline, a bank of narrow-band
superconducting resonator filters that provide spectral selectivity, and
Kinetic Inductance Detectors (KIDs) that detect the power admitted by each
filter resonator. The design is realized using thin-film lithographic
structures on a silicon wafer. The mm-wave microstrip feedline and spectral
filters of the first prototype are designed to operate in the band from 195-310
GHz and are fabricated from niobium with at Tc of 9.2K. The KIDs are designed
to operate at hundreds of MHz and are fabricated from titanium nitride with a
Tc of 2K. Radiation incident on the horn travels along the mm-wave microstrip,
passes through the frequency-selective filter, and is finally absorbed by the
corresponding KID where it causes a measurable shift in the resonant frequency.
In this proceedings, we present the design of the KIDs employed in SuperSpec
and the results of initial laboratory testing of a prototype device. We will
also briefly describe the ongoing development of a demonstration instrument
that will consist of two 500-channel, R=700 spectrometers, one operating in the
1-mm atmospheric window and the other covering the 650 and 850 micron bands.Comment: As submitted, except that "in prep" references have been update
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