616 research outputs found
Development of Lumped Element Kinetic Inductance Detectors for NIKA
Lumped-element kinetic inductance detectors(LEKIDs) have recently shown
considerable promise as direct absorption mm-wavelength detectors for
astronomical applications. One major research thrust within the N\'eel Iram
Kids Array (NIKA) collaboration has been to investigate the suitability of
these detectors for deployment at the 30-meter IRAM telescope located on Pico
Veleta in Spain. Compared to microwave kinetic inductance detectors (MKID),
using quarter wavelength resonators, the resonant circuit of a LEKID consists
of a discrete inductance and capacitance coupled to a feedline. A high and
constant current density distribution in the inductive part of these resonators
makes them very sensitive. Due to only one metal layer on a silicon substrate,
the fabrication is relatively easy. In order to optimize the LEKIDs for this
application, we have recently probed a wide variety of individual resonator and
array parameters through simulation and physical testing. This included
determining the optimal feed-line coupling, pixel geometry, resonator
distribution within an array (in order to minimize pixel cross-talk), and
resonator frequency spacing. Based on these results, a 144-pixel Aluminum array
was fabricated and tested in a dilution fridge with optical access, yielding an
average optical NEP of ~2E-16 W/Hz^1/2 (best pixels showed NEP = 6E-17 W/Hz^1/2
under 4-8 pW loading per pixel). In October 2010 the second prototype of LEKIDs
has been tested at the IRAM 30 m telescope. A new LEKID geometry for 2
polarizations will be presented. Also first optical measurements of a titanium
nitride array will be discussed.Comment: 5 pages, 12 figures; ISSTT 2011 Worksho
A Titanium Nitride Absorber for Controlling Optical Crosstalk in Horn-Coupled Aluminum LEKID Arrays for Millimeter Wavelengths
We discuss the design and measured performance of a titanium nitride (TiN)
mesh absorber we are developing for controlling optical crosstalk in
horn-coupled lumped-element kinetic inductance detector arrays for
millimeter-wavelengths. This absorber was added to the fused silica
anti-reflection coating attached to previously-characterized, 20-element
prototype arrays of LEKIDs fabricated from thin-film aluminum on silicon
substrates. To test the TiN crosstalk absorber, we compared the measured
response and noise properties of LEKID arrays with and without the TiN mesh.
For this test, the LEKIDs were illuminated with an adjustable, incoherent
electronic millimeter-wave source. Our measurements show that the optical
crosstalk in the LEKID array with the TiN absorber is reduced by 66\% on
average, so the approach is effective and a viable candidate for future
kilo-pixel arrays.Comment: 7 pages, 5 figures, accepted for publication in the Journal of Low
Temperature Physic
Measurements of Sunyaev-Zel'dovich Effect Scaling Relations for Clusters of Galaxies
We present new measurements of the Sunyaev-Zel'dovich (SZ) effect from
clusters of galaxies using the Sunyaev-Zel'dovich Infrared Experiment (SuZIE
II). We combine these new measurements with previous cluster observations with
the SuZIE instrument to form a sample of 15 clusters of galaxies. For this
sample we calculate the central Comptonization, y, and the integrated SZ flux
decrement, S, for each of our clusters. We find that the integrated SZ flux is
a more robust observable derived from our measurements than the central
Comptonization due to inadequacies in the spatial modelling of the
intra-cluster gas with a standard Beta model. This is highlighted by comparing
our central Comptonization results with values calculated from measurements
using the BIMA and OVRO interferometers. On average, the SuZIE calculated
central Comptonizations are approximately 60% higher in the cooling flow
clusters than the interferometric values, compared to only approximately 12%
higher in the non-cooling flow clusters. We believe this discrepancy to be in
large part due to the spatial modelling of the intra-cluster gas. From our
cluster sample we construct y-T and S-T scaling relations. The y-T scaling
relation is inconsistent with what we would expect for self-similar clusters;
however this result is questionable because of the large systematic uncertainty
in the central Comptonization. The S-T scaling relation has a slope and
redshift evolution consistent with what we expect for self-similar clusters
with a characteristic density that scales with the mean density of the
universe. We rule out zero redshift evolution of the S-T relation at 90%
confidence.Comment: Accepted to Astrophysical Journal. 52 pages, 14 tables, 7 figures
;replaced to match ApJ accepted versio
Status of SuperSpec: A Broadband, On-Chip Millimeter-Wave Spectrometer
SuperSpec is a novel on-chip spectrometer we are developing for multi-object,
moderate resolution (R = 100 - 500), large bandwidth (~1.65:1) submillimeter
and millimeter survey spectroscopy of high-redshift galaxies. The spectrometer
employs a filter bank architecture, and consists of a series of half-wave
resonators formed by lithographically-patterned superconducting transmission
lines. The signal power admitted by each resonator is detected by a lumped
element titanium nitride (TiN) kinetic inductance detector (KID) operating at
100-200 MHz. We have tested a new prototype device that is more sensitive than
previous devices, and easier to fabricate. We present a characterization of a
representative R=282 channel at f = 236 GHz, including measurements of the
spectrometer detection efficiency, the detector responsivity over a large range
of optical loading, and the full system optical efficiency. We outline future
improvements to the current system that we expect will enable construction of a
photon-noise-limited R=100 filter bank, appropriate for a line intensity
mapping experiment targeting the [CII] 158 micron transition during the Epoch
of ReionizationComment: 16 pages, 10 figures, Proceedings of the SPIE Astronomical Telescopes
+ Instrumentation 2014 Conference, Vol 9153, Millimeter, Submillimeter, and
Far-Infrared Detectors and Instrumentation for Astronomy VI
Horn-Coupled, Commercially-Fabricated Aluminum Lumped-Element Kinetic Inductance Detectors for Millimeter Wavelengths
We discuss the design, fabrication, and testing of prototype horn-coupled,
lumped-element kinetic inductance detectors (LEKIDs) designed for cosmic
microwave background (CMB) studies. The LEKIDs are made from a thin aluminum
film deposited on a silicon wafer and patterned using standard
photolithographic techniques at STAR Cryoelectronics, a commercial device
foundry. We fabricated twenty-element arrays, optimized for a spectral band
centered on 150 GHz, to test the sensitivity and yield of the devices as well
as the multiplexing scheme. We characterized the detectors in two
configurations. First, the detectors were tested in a dark environment with the
horn apertures covered, and second, the horn apertures were pointed towards a
beam-filling cryogenic blackbody load. These tests show that the multiplexing
scheme is robust and scalable, the yield across multiple LEKID arrays is 91%,
and the noise-equivalent temperatures (NET) for a 4 K optical load are in the
range 26\thinspace\pm6 \thinspace \mu \mbox{K} \sqrt{\mbox{s}}
A Search for Cosmic Microwave Background Anisotropies on Arcminute Scales with Bolocam
We have surveyed two science fields totaling one square degree with Bolocam
at 2.1 mm to search for secondary CMB anisotropies caused by the Sunyaev-
Zel'dovich effect (SZE). The fields are in the Lynx and Subaru/XMM SDS1 fields.
Our survey is sensitive to angular scales with an effective angular multipole
of l_eff = 5700 with FWHM_l = 2800 and has an angular resolution of 60
arcseconds FWHM. Our data provide no evidence for anisotropy. We are able to
constrain the level of total astronomical anisotropy, modeled as a flat
bandpower in C_l, with frequentist 68%, 90%, and 95% CL upper limits of 590,
760, and 830 uKCMB^2. We statistically subtract the known contribution from
primary CMB anisotropy, including cosmic variance, to obtain constraints on the
SZE anisotropy contribution. Now including flux calibration uncertainty, our
frequentist 68%, 90% and 95% CL upper limits on a flat bandpower in C_l are
690, 960, and 1000 uKCMB^2. When we instead employ the analytic spectrum
suggested by Komatsu and Seljak (2002), and account for the non-Gaussianity of
the SZE anisotropy signal, we obtain upper limits on the average amplitude of
their spectrum weighted by our transfer function of 790, 1060, and 1080
uKCMB^2. We obtain a 90% CL upper limit on sigma8, which normalizes the power
spectrum of density fluctuations, of 1.57. These are the first constraints on
anisotropy and sigma8 from survey data at these angular scales at frequencies
near 150 GHz.Comment: 68 pages, 17 figures, 2 tables, accepted for publication in Ap
High Spectral Resolution Measurement of the Sunyaev–Zel'dovich Effect Null with Z-Spec
The Sunyaev-Zel'dovich (SZ) effect spectrum crosses through a null where ΔT_CMB = 0 near ν_0 = 217 GHz. In a cluster of galaxies, ν0 can be shifted from the canonical thermal SZ effect value by corrections to the SZ effect scattering due to the properties of the inter-cluster medium. We have measured the SZ effect in the hot galaxy cluster RX J 1347.5 – 1145 with Z-Spec, an R ~ 300 grating spectrometer sensitive between 185 and 305 GHz. These data comprise a high spectral resolution measurement around the null of the SZ effect and clearly exhibit the transition from negative to positive ΔT_CMB over the Z-Spec band. The SZ null position is measured to be ν_0 = 225.8 ± 2.5(stat.) ± 1.2(sys.) GHz, which differs from the canonical null frequency by 3.0σ and is evidence for modifications to the canonical thermal SZ effect shape. Assuming the measured shift in ν0 is due only to relativistic corrections to the SZ spectrum, we place the limit kT_e = 17.1 ± 5.3 keV from the zero-point measurement alone. By simulating the response of the instrument to the sky, we are able to generate likelihood functions in {y_0, T_e, v_pec} space. For v_pec = 0 km s^(–1), we measure the best-fitting SZ model to be y_0 = 4.6^(+0.6)_(–0.9) × 10^(–4), T_e, 0 = 15.2^(+12)_(–7.4) keV. When v pec is allowed to vary, a most probable value of v_pec = + 450 ± 810 km s^(–1) is found
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
A strained silicon cold electron bolometer using Schottky contacts
We describe optical characterisation of a strained silicon cold electron bolometer (CEB), operating on a 350 mK stage, designed for absorption of millimetre-wave radiation. The silicon cold electron bolometer utilises Schottky contacts between a superconductor and an n++ doped silicon island to detect changes in the temperature of the charge carriers in the silicon, due to variations in absorbed radiation. By using strained silicon as the absorber, we decrease the electron-phonon coupling in the device and increase the responsivity to incoming power. The strained silicon absorber is coupled to a planar aluminium twin-slot antenna designed to couple to 160 GHz and that serves as the superconducting contacts. From the measured optical responsivity and spectral response, we calculate a maximum optical efficiency of 50% for radiation coupled into the device by the planar antenna and an overall noise equivalent power, referred to absorbed optical power, of 1.1×10−16 W Hz−1/2 when the detector is observing a 300 K source through a 4 K throughput limiting aperture. Even though this optical system is not optimized, we measure a system noise equivalent temperature difference of 6 mK Hz−1/2. We measure the noise of the device using a cross-correlation of time stream data, measured simultaneously with two junction field-effect transistor amplifiers, with a base correlated noise level of 300 pV Hz−1/2 and find that the total noise is consistent with a combination of photon noise, current shot noise, and electron-phonon thermal noise
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