167 research outputs found
Design and construction of a carbon fiber gondola for the SPIDER balloon-borne telescope
We introduce the light-weight carbon fiber and aluminum gondola designed for the Spider balloon-borne telescope. Spider is designed to measure the polarization of the Cosmic Microwave Background radiation with unprecedented sensitivity and control of systematics in search of the imprint of inflation: a period of exponential expansion in the early Universe. The requirements of this balloon-borne instrument put tight constrains on the mass budget of the payload. The Spider gondola is designed to house the experiment and guarantee its operational and structural integrity during its balloon-borne flight, while using less than 10% of the total mass of the payload. We present a construction method for the gondola based on carbon fiber reinforced polymer tubes with aluminum inserts and aluminum multi-tube joints. We describe the validation of the model through Finite Element Analysis and mechanical tests
SPIDER: CMB Polarimetry from the Edge of Space
Spider is a balloon-borne instrument designed to map the polarization of the millimeter-wave sky at large angular scales. Spider targets the B-mode signature of primordial gravitational waves in the cosmic microwave background (CMB), with a focus on mapping a large sky area with high fidelity at multiple frequencies. Spider ’s first long-duration balloon (LDB) flight in January 2015 deployed a total of 2400 antenna-coupled transition-edge sensors (TESs) at 90 GHz and 150 GHz. In this work we review the design and in-flight performance of the Spider instrument, with a particular focus on the measured performance of the detectors and instrument in a space-like loading and radiation environment. Spider ’s second flight in December 2018 will incorporate payload upgrades and new receivers to map the sky at 285 GHz, providing valuable information for cleaning polarized dust emission from CMB maps
A New Limit on CMB Circular Polarization from SPIDER
We present a new upper limit on cosmic microwave background (CMB) circular polarization from the 2015 flight of SPIDER, a balloon-borne telescope designed to search for B-mode linear polarization from cosmic inflation. Although the level of circular polarization in the CMB is predicted to be very small, experimental limits provide a valuable test of the underlying models. By exploiting the nonzero circular-to-linear polarization coupling of the half-wave plate polarization modulators, data from SPIDER's 2015 Antarctic flight provide a constraint on Stokes V at 95 and 150 GHz in the range 33 < ℓ < 307. No other limits exist over this full range of angular scales, and SPIDER improves on the previous limit by several orders of magnitude, providing 95% C.L. constraints on ℓ(ℓ + 1)C^(VV)_ ℓ/(2π) ranging from 141 to 255 μK^2 at 150 GHz for a thermal CMB spectrum. As linear CMB polarization experiments become increasingly sensitive, the techniques described in this paper can be applied to obtain even stronger constraints on circular polarization
Pre-flight integration and characterization of the SPIDER balloon-borne telescope
We present the results of integration and characterization of the Spider instrument after the 2013 pre-flight campaign. Spider is a balloon-borne polarimeter designed to probe the primordial gravitational wave signal in the degree-scale B-mode polarization of the cosmic microwave background. With six independent telescopes housing over 2000 detectors in the 94 GHz and 150 GHz frequency bands, Spider will map 7.5% of the sky with a depth of 11 to 14 μK•arcmin at each frequency, which is a factor of ~5 improvement over Planck. We discuss the integration of the pointing, cryogenic, electronics, and power sub-systems, as well as pre-flight characterization of the detectors and optical systems. Spider is well prepared for a December 2014 flight from Antarctica, and is expected to be limited by astrophysical foreground emission, and not instrumental sensitivity, over the survey region
280 GHz Focal Plane Unit Design and Characterization for the Spider-2 Suborbital Polarimeter
We describe the construction and characterization of the 280 GHz bolometric focal plane units (FPUs) to be deployed on the second flight of the balloon-borne Spider instrument. These FPUs are vital to Spider’s primary science goal of detecting or placing an upper limit on the amplitude of the primordial gravitational wave signature in the cosmic microwave background (CMB) by constraining the B-mode contamination in the CMB from Galactic dust emission. Each 280 GHz focal plane contains a 16×16 grid of corrugated silicon feedhorns coupled to an array of aluminum–manganese transition-edge sensor (TES) bolometers fabricated on 150 mm diameter substrates. In total, the three 280 GHz FPUs contain 1530 polarization-sensitive bolometers (765 spatial pixels) optimized for the low loading environment in flight and read out by time-division SQUID multiplexing. In this paper, we describe the mechanical, thermal, and magnetic shielding architecture of the focal planes and present cryogenic measurements which characterize yield and the uniformity of several bolometer parameters. The assembled FPUs have high yields, with one array as high as 95% including defects from wiring and readout. We demonstrate high uniformity in device parameters, finding the median saturation power for each TES array to be ∼ 3 pW at 300 mK with a less than 6% variation across each array at
SPIDER: a balloon-borne CMB polarimeter for large angular scales
We describe SPIDER, a balloon-borne instrument to map the polarization of the
millimeter-wave sky with degree angular resolution. Spider consists of six
monochromatic refracting telescopes, each illuminating a focal plane of
large-format antenna-coupled bolometer arrays. A total of 2,624 superconducting
transition-edge sensors are distributed among three observing bands centered at
90, 150, and 280 GHz. A cold half-wave plate at the aperture of each telescope
modulates the polarization of incoming light to control systematics. Spider's
first flight will be a 20-30-day Antarctic balloon campaign in December 2011.
This flight will map \sim8% of the sky to achieve unprecedented sensitivity to
the polarization signature of the gravitational wave background predicted by
inflationary cosmology. The Spider mission will also serve as a proving ground
for these detector technologies in preparation for a future satellite mission.Comment: 12 pages, 6 figures; as published in the conference proceedings for
SPIE Millimeter, Submillimeter, and Far-Infrared Detectors and
Instrumentation for Astronomy V (2010
Safety of Gabapentin Prescribed for Any Indication in a Large Clinical Cohort of 571,718 US Veterans with and without Alcohol Use Disorder.
BACKGROUND: Gabapentin is prescribed for seizures and pain and has efficacy for treating alcohol use disorder (AUD) starting at doses of 900 milligrams per day (mg/d). Recent evidence suggests safety concerns associated with gabapentin including adverse neurologic effects. Individuals with hepatitis C (HCV), HIV, or AUD may be at increased risk due to comorbidities and potential medication interactions. METHODS: We identified patients prescribed gabapentin for ? 60 days for any indication between 2002 and 2015. We propensity-score matched each gabapentin-exposed patient with up to 5 gabapentin-unexposed patients. We followed patients for 2 years or until diagnosed with (i) falls or fractures, or (ii) altered mental status using validated ICD-9 diagnostic codes. We used Poisson regression to estimate incidence rates and relative risk (RR) of these adverse events in association with gabapentin exposure overall and stratified by age, race/ethnicity, sex, HCV, HIV, AUD, and dose. RESULTS: Incidence of falls or fractures was 1.81 per 100 person-years (PY) among 140,310 gabapentin-exposed and 1.34/100 PY among 431,408 gabapentin-unexposed patients (RR 1.35, 95% confidence interval [CI] 1.28 to 1.44). Incidence of altered mental status was 1.08/100 PY among exposed and 0.97/100 PY among unexposed patients, RR of 1.12 (95% CI 1.04 to 1.20). Excess risk of falls or fractures associated with gabapentin exposure was observed in all subgroups except patients with HCV, HIV, or AUD; however, these groups had elevated incidence regardless of exposure. There was a clear dose-response relationship for falls or fractures with highest risk observed among those prescribed ? 2,400 mg/d (RR 1.90, 95% CI 1.50 to 2.40). Patients were at increased risk for altered mental status at doses 600 to 2,399 mg/d; however, low number of events in the highest dose category limited power to detect a statistically significant association ? 2,400 mg/d. CONCLUSIONS: Gabapentin is associated with falls or fractures and altered mental status. Clinicians should be monitoring gabapentin safety, especially at doses ? 600 mg/d, in patients with and without AUD
280 GHz Focal Plane Unit Design and Characterization for the SPIDER-2 Suborbital Polarimeter
We describe the construction and characterization of the 280 GHz bolometric
focal plane units (FPUs) to be deployed on the second flight of the
balloon-borne SPIDER instrument. These FPUs are vital to SPIDER's primary
science goal of detecting or placing an upper limit on the amplitude of the
primordial gravitational wave signature in the cosmic microwave background
(CMB) by constraining the B-mode contamination in the CMB from Galactic dust
emission. Each 280 GHz focal plane contains a 16 x 16 grid of corrugated
silicon feedhorns coupled to an array of aluminum-manganese transition-edge
sensor (TES) bolometers fabricated on 150 mm diameter substrates. In total, the
three 280 GHz FPUs contain 1,530 polarization sensitive bolometers (765 spatial
pixels) optimized for the low loading environment in flight and read out by
time-division SQUID multiplexing. In this paper we describe the mechanical,
thermal, and magnetic shielding architecture of the focal planes and present
cryogenic measurements which characterize yield and the uniformity of several
bolometer parameters. The assembled FPUs have high yields, with one array as
high as 95% including defects from wiring and readout. We demonstrate high
uniformity in device parameters, finding the median saturation power for each
TES array to be ~3 pW at 300 mK with a less than 6% variation across each array
at one standard deviation. These focal planes will be deployed alongside the 95
and 150 GHz telescopes in the SPIDER-2 instrument, slated to fly from McMurdo
Station in Antarctica in December 2018
SPIDER: CMB Polarimetry from the Edge of Space
Spider is a balloon-borne instrument designed to map the polarization of the millimeter-wave sky at large angular scales. Spider targets the B-mode signature of primordial gravitational waves in the cosmic microwave background (CMB), with a focus on mapping a large sky area with high fidelity at multiple frequencies. Spider ’s first long-duration balloon (LDB) flight in January 2015 deployed a total of 2400 antenna-coupled transition-edge sensors (TESs) at 90 GHz and 150 GHz. In this work we review the design and in-flight performance of the Spider instrument, with a particular focus on the measured performance of the detectors and instrument in a space-like loading and radiation environment. Spider ’s second flight in December 2018 will incorporate payload upgrades and new receivers to map the sky at 285 GHz, providing valuable information for cleaning polarized dust emission from CMB maps
Pointing control for the SPIDER balloon-borne telescope
We present the technology and control methods developed for the pointing system of the Spider experiment. Spider is a balloon-borne polarimeter designed to detect the imprint of primordial gravitational waves in the polarization of the Cosmic Microwave Background radiation. We describe the two main components of the telescope’s azimuth drive: the reaction wheel and the motorized pivot. A 13 kHz PI control loop runs on a digital signal processor, with feedback from fibre optic rate gyroscopes. This system can control azimuthal speed with < 0.02 deg/s RMS error. To control elevation, Spider uses stepper-motor-driven linear actuators to rotate the cryostat, which houses the optical instruments, relative to the outer frame. With the velocity in each axis controlled in this way, higher-level control loops on the onboard flight computers can implement the pointing and scanning observation modes required for the experiment. We have accomplished the non-trivial task of scanning a 5000 lb payload sinusoidally in azimuth at a peak acceleration of 0.8 deg/s^2, and a peak speed of 6 deg/s. We can do so while reliably achieving sub-arcminute pointing control accuracy
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