Astronomical surveys of the cosmic microwave background (CMB) and large-scale structure (LSS) have provided empirical answers to many of the most profound questions in cosmology and particle ...astrophysics. In particular, these measurements have yielded some of the strongest pieces of evidence for Lambda-CDM, the prevailing standard model of cosmology describing the composition and underlying physics of the universe. Upcoming surveys aim to provide further insights --- for example, putting improved constraints on the properties and nature of dark energy, detecting the sum of the neutrino masses, and stress testing the standard cosmological model. In this dissertation, I discuss the design and integrated performance of SPT-3G, the third survey receiver operating on the South Pole Telescope (a 10-meter diameter telescope designed for high-resolution observations of the CMB). In particular, I provide details on the design, development, testing, and performance of the SPT-3G optical and cryogenics systems. Following this discussion, I present the first galaxy cluster sample constructed using SPT-3G survey data from the 2019 and 2020 observing seasons. The catalog contains 2457 candidates over 1500 square degrees, selected via the Sunyaev-Zel'dovich (SZ) effect with signal-to-noise ratios greater than 5. Because the formation history of galaxy clusters strongly depended on the universe's physical conditions through time, measuring the abundance of galaxy clusters provides a unique way to probe the evolution of LSS. The initial catalog presented in this work demonstrates the significant improvement in SZ-detection sensitivity provided by the SPT-3G survey. In combination with optical/infrared measurements of the cluster candidates' redshifts and masses, the catalog is poised to put new constraints on cosmology, specifically on the nature of dark energy and neutrino mass.
The South Pole Telescope SPT-3G camera utilizes Ti/Au transition edge sensors (TESs). A key requirement for these sensors is reproducibility and long-term stability of the superconducting (SC) ...transitions. Here, we discuss the impact of electrical contacts design and materials on the shape of the SC transitions. Using scanning electron microscope, atomic force microscope, and optical differential interference contrast microscopy, we observed the presence of unexpected defects of morphological nature on the titanium surface and their evolution in time in proximity to Nb contacts. We found direct correlation between the variations of the morphology and the SC transition shape. Experiments with different diffusion barriers between TES and Nb leads were performed to clarify the origin of this problem. We have demonstrated that the reproducibility of superconducting transitions can be significantly improved by preventing diffusion processes in the TES–leads contact areas.
The third-generation South Pole Telescope camera is designed to measure the cosmic microwave background across three frequency bands (95, 150 and 220 GHz) with ~16,000 transition-edge sensor (TES) ...bolometers. Each multichroic pixel on a detector wafer has a broadband sinuous antenna that couples power to six TESs, one for each of the three observing bands and both polarization directions, via lumped element filters. Ten detector wafers populate the focal plane, which is coupled to the sky via a large-aperture optical system. Here we present the frequency band characterization with Fourier transform spectroscopy, measurements of optical time constants, beam properties, and optical and polarization efficiencies of the focal plane. The detectors have frequency bands consistent with our simulations, and have high average optical efficiency which is 86%, 77% and 66% for the 95, 150 and 220 GHz detectors. The time constants of the detectors are mostly between 0.5 ms and 5 ms. The beam is round with the correct size, and the polarization efficiency is more than 90% for most of the bolometers
To investigate the clinical and magnetic resonance imaging (MRI) characteristics of patients with varicella zoster virus (VZV) reactivation involving the cranial nerves and central nervous system ...(CNS).
This is a retrospective, multi-center case-series of 37 patients with VZV infection affecting the cranial nerves and CNS.
The median age was 71 years IQR 51.5-76; 21 (57%) were men. Cerebrospinal fluid (CSF) was available in 24/37 (65%); median CSF white blood cell count was 11 IQR 2-23 cells/μL and protein was 45.5 IQR 34.5-75.5 mg/dL. VZV polymerase chain reaction (PCR) assays were positive in 6/21 (29%) CSF and 8/9 (89%) ocular samples. Clinical involvement included the optic nerve in 12 (32%), other cranial nerves in 20 (54%), brain parenchyma in 12 (32%) and spinal cord or nerve roots in 4 (11%).
Twenty-seven/28 immunocompetent patients' MRIs were available for review (96%). Of the 27, 18 had T1 postcontrast fat saturated sequences without motion artifact to evaluate for cranial nerve enhancement and optic perineuritis (OPN). Eight/18 (44%) demonstrated OPN. All 8 experienced vision loss: 3 optic neuritis, 1 acute retinal necrosis, and 3 CNS vasculitis with 1 central and 1 branch retinal artery occlusion and 1 uveitis. Diplopic patients had cranial nerve and cavernous sinus enhancement.
All immunosuppressed patients were imaged. Seven/9 (88%) had extensive neuraxis involvement, including encephalitis, vasculitis and transverse myelitis; one case had OPN.
OPN is a frequent manifestation in VZV-associated vision loss among immunocompetent patients. Immunosuppressed patients had greater neuraxis involvement. Optimizing MRI protocols may improve early diagnosis in VZV reactivation.
•OPN is a frequent manifestation in VZV-associated vision loss among immunocompetent patients.•Immunosuppressed patients had greater neuraxis involvement, including the spinal cord and vasculitis.•Optimizing MRI protocols may improve early diagnosis in VZV reactivation.
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