20 research outputs found
Studies of Systematic Uncertainties for Simons Observatory: Optical Effects and Sensitivity Considerations
No full textInternational audienceThe Simons Observatory (SO) is a new experiment that aims to measure the cosmic microwave background (CMB) in temperature and polarization. SO will measure the polarized sky over a large range of microwave frequencies and angular scales using a combination of small () and large () aperture telescopes and will be located in the Atacama Desert in Chile. This work is part of a series of papers studying calibration, sensitivity, and systematic errors for SO. In this paper, we discuss current efforts to model optical systematic effects, how these have been used to guide the design of the SO instrument, and how these studies can be used to inform instrument design of future experiments like CMB-S4. While optical systematics studies are underway for both the small aperture and large aperture telescopes, we limit the focus of this paper to the more mature large aperture telescope design for which our studies include: pointing errors, optical distortions, beam ellipticity, cross-polar response, instrumental polarization rotation and various forms of sidelobe pickup
Studies of Systematic Uncertainties for Simons Observatory: Polarization Modulator Related Effects
No full textInternational audienceThe Simons Observatory (SO) will observe the temperature and polarization anisotropies of the cosmic microwave background (CMB) over a wide range of frequencies (27 to 270 GHz) and angular scales by using both small (0.5 m) and large (6 m) aperture telescopes. The SO small aperture telescopes will target degree angular scales where the primordial B-mode polarization signal is expected to peak. The incoming polarization signal of the small aperture telescopes will be modulated by a cryogenic, continuously-rotating half-wave plate (CRHWP) to mitigate systematic effects arising from slowly varying noise and detector pair-differencing. In this paper, we present an assessment of some systematic effects arising from using a CRHWP in the SO small aperture systems. We focus on systematic effects associated with structural properties of the HWP and effects arising when operating a HWP, including the amplitude of the HWP synchronous signal (HWPSS), and I -> P (intensity to polarization) leakage that arises from detector non-linearity in the presence of a large HWPSS. We demonstrate our ability to simulate the impact of the aforementioned systematic effects in the time domain. This important step will inform mitigation strategies and design decisions to ensure that SO will meet its science goals
Safety and efficacy of recombinant human interleukin 10 in chronic active Crohn's disease. Crohn's Disease IL-10 Cooperative Study Group
No full textInterleukin (IL)-10 is a cytokine with potent anti-inflammatory properties. We investigated the safety and efficacy of different doses of human recombinant (rhu)IL-10 in patients with Crohn's disease (CD). A prospective, multicenter, double-blind, placebo-controlled study was conducted in 329 therapy-refractory patients with CD. Clinical improvement was defined by a reduction of the Crohn's Disease Activity Index (CDAI) by 100 points or more and clinical remission by a decrease of the CDAI to <150 points. At selected centers, patients underwent ileocolonoscopies and activation of the nuclear factor-kappa B (NF-kappa B) system was assessed in biopsy specimens. Subcutaneous treatment with rhuIL-10 over 28 days induced a fully reversible, dose-dependent decrease in hemoglobin and thrombocyte counts but no clinically significant side effects. No differences in the induction of remission were observed between rhuIL-10 groups (1 microg, 18% [9.6-29.2]; 4 microg, 20% [11.3-32.2]; 8 microg, 20% [11.1-31.8]; 20 microg, 28% [18-40.7]; and placebo, 18% [9.6-29.6]). Clinical improvement was observed in 46% (33.7-59) in the 8-microg/kg rhuIL-10 group in comparison with 27% (17-39.6) in patients taking placebo. Responders to rhuIL-10 showed inhibition of NF-kappaB p65 activation in contrast to nonresponders. Up to 8 microg/kg of rhuIL-10 was well tolerated. A tendency toward clinical improvement but not remission was observed in the 8-microg/kg dose group. Further studies should delineate which subgroups of patients with CD benefit from rhuIL-10 therap
The Simons Observatory: overview of data acquisition, control, monitoring, and computer infrastructure
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The Simons Observatory: gain, bandpass and polarization-angle calibration requirements for B-mode searches
No full textInternational audienceWe quantify the calibration requirements for systematic uncertainties for next-generation ground-based observatories targeting the large-angle B-mode polarization of the Cosmic Microwave Background, with a focus on the Simons Observatory (SO). We explore uncertainties on gain calibration, bandpass center frequencies, and polarization angles, including the frequency variation of the latter across the bandpass. We find that gain calibration and bandpass center frequencies must be known to percent levels or less to avoid biases on the tensor-to-scalar ratio r on the order of Δ r∼10-3, in line with previous findings. Polarization angles must be calibrated to the level of a few tenths of a degree, while their frequency variation between the edges of the band must be known to O(10) degrees. Given the tightness of these calibration requirements, we explore the level to which residual uncertainties on these systematics would affect the final constraints on r if included in the data model and marginalized over. We find that the additional parameter freedom does not degrade the final constraints on r significantly, broadening the error bar by O(10%) at most. We validate these results by reanalyzing the latest publicly available data from the collaboration within an extended parameter space covering both cosmological, foreground and systematic parameters. Finally, our results are discussed in light of the instrument design and calibration studies carried out within SO
The Simons Observatory: gain, bandpass and polarization-angle calibration requirements for B-mode searches
No full text
The Simons Observatory:Instrument overview
No full textThe Simons Observatory (SO) will make precision temperature and polarization measurements of the cosmic microwave background (CMB) using a series of telescopes which will cover angular scales between 1 arcminute and tens of degrees, contain over 40,000 detectors, and sample frequencies between 27 and 270 GHz. SO will consist of a six-meter-aperture telescope coupled to over 20,000 detectors along with an array of half-meter aperture refractive cameras, coupled to an additional 20,000+ detectors. The unique combination of large and small apertures in a single CMB observatory, which will be located in the Atacama Desert at an altitude of 5190 m, will allow us to sample a wide range of angular scales over a common survey area. SO will measure fundamental cosmological parameters of our universe, find high redshift clusters via the Sunyaev-Zeldovich effect, constrain properties of neutrinos, and seek signatures of dark matter through gravitational lensing. The complex set of technical and science requirements for this experiment has led to innovative instrumentation solutions which we will discuss. The large aperture telescope will couple to a cryogenic receiver that is 2.4 m in diameter and over 2 m long, creating a number of interesting technical challenges. Concurrently, we are designing an array of half-meter-aperture cryogenic cameras which also have compelling design challenges. We will give an overview of the drivers for and designs of the SO telescopes and the cryogenic cameras that will house the cold optical components and detector arrays.</p
The Simons Observatory: Design, integration, and testing of the small aperture telescopes
No full textInternational audienceThe Simons Observatory (SO) is a cosmic microwave background (CMB) survey experiment that includes small-aperture telescopes (SATs) observing from an altitude of 5,200 m in the Atacama Desert in Chile. The SO SATs will cover six spectral bands between 27 and 280 GHz to search for primordial B-modes to a sensitivity of , with quantified systematic errors well below this value. Each SAT is a self-contained cryogenic telescope with a 35 field of view, 42 cm diameter optical aperture, 40 K half-wave plate, 1 K refractive optics, and TES detectors. We describe the nominal design of the SATs and present details about the integration and testing for one operating at 93 and 145 GHz
The Simons Observatory: Science goals and forecasts
No full textInternational audienceThe Simons Observatory (SO) is a new cosmic microwave background experiment being built on Cerro Toco in Chile, due to begin observations in the early 2020s. We describe the scientific goals of the experiment, motivate the design, and forecast its performance. SO will measure the temperature and polarization anisotropy of the cosmic microwave background in six frequency bands centered at: 27, 39, 93, 145, 225 and 280 GHz. The initial configuration of SO will have three small-aperture 0.5-m telescopes and one large-aperture 6-m telescope, with a total of 60,000 cryogenic bolometers. Our key science goals are to characterize the primordial perturbations, measure the number of relativistic species and the mass of neutrinos, test for deviations from a cosmological constant, improve our understanding of galaxy evolution, and constrain the duration of reionization. The small aperture telescopes will target the largest angular scales observable from Chile, mapping ≈ 10% of the sky to a white noise level of 2 μK-arcmin in combined 93 and 145 GHz bands, to measure the primordial tensor-to-scalar ratio, r, at a target level of σ(r)=0.003. The large aperture telescope will map ≈ 40% of the sky at arcminute angular resolution to an expected white noise level of 6 μK-arcmin in combined 93 and 145 GHz bands, overlapping with the majority of the Large Synoptic Survey Telescope sky region and partially with the Dark Energy Spectroscopic Instrument. With up to an order of magnitude lower polarization noise than maps from the Planck satellite, the high-resolution sky maps will constrain cosmological parameters derived from the damping tail, gravitational lensing of the microwave background, the primordial bispectrum, and the thermal and kinematic Sunyaev-Zel'dovich effects, and will aid in delensing the large-angle polarization signal to measure the tensor-to-scalar ratio. The survey will also provide a legacy catalog of 16,000 galaxy clusters and more than 20,000 extragalactic sources
