Bradley R. Johnson
A5002022623- Radio Astronomy Observations and Technology
- Superconducting and THz Device Technology
- Cosmology and Gravitation Theories
- Astronomy and Astrophysical Research
- Dark Matter and Cosmic Phenomena
- Geophysics and Gravity Measurements
- Microwave Engineering and Waveguides
- Astrophysics and Cosmic Phenomena
- Galaxies: Formation, Evolution, Phenomena
- Glass properties and applications
- Phase-change materials and chalcogenides
- Physics of Superconductivity and Magnetism
- Scientific Research and Discoveries
- Coastal and Marine Dynamics
- Chalcogenide Semiconductor Thin Films
- Pulsars and Gravitational Waves Research
- Astrophysics and Star Formation Studies
- Stellar, planetary, and galactic studies
- Adaptive optics and wavefront sensing
- Radio Frequency Integrated Circuit Design
- Spacecraft and Cryogenic Technologies
- Advanced ceramic materials synthesis
- Photonic and Optical Devices
- Gamma-ray bursts and supernovae
- Geomagnetism and Paleomagnetism Studies
University of Virginia
2020-2025
Davidson College
2023-2024
Virginia Commonwealth University
2023
U.S. Army Engineer Research and Development Center
2009-2023
United States Army
2011-2023
Oak Ridge National Laboratory
2007-2022
Medical College of Wisconsin
2018-2022
Fermi National Accelerator Laboratory
2022
University of Chicago
2022
University of Oxford
2006-2021
The application of lithium (Li) metal anodes in rechargeable batteries is hindered by Li dendrite growth during deposition and low Coulombic efficiency (CE), where the nonaqueous electrolyte plays a critical role. In this work, effects different carbonate solvents salts on morphology CE were systematically investigated. Typically, cyclic carbonates favor formation uniform films improve more than linear do. Several specific that are conventionally used as solid interphase (SEI) additives...
A technological milestone for experiments employing transition edge sensor bolometers operating at sub-Kelvin temperature is the deployment of detector arrays with 100s-1000s bolometers. One key technology such readout multiplexing: ability to read out many sensors simultaneously on same set wires. This paper describes a frequency-domain multiplexed system which has been developed and deployed APEX-SZ South Pole Telescope millimeter wavelength receivers. In this system, array divided into...
The Probe of Inflation and Cosmic Origins (PICO) is a proposed probe-scale space mission consisting an imaging polarimeter operating in frequency bands between 20 800 GHz. We describe the science achievable by PICO, which has sensitivity equivalent to more than 3300 Planck missions, technical implementation, schedule cost.
We present the requirements, design, and evaluation of cryogenic continuously rotating half-wave plate (CHWP) for Simons Observatory (SO). SO is a cosmic microwave background polarization experiment at Parque Astronómico de Atacama in northern Chile that covers wide range angular scales using both small (⌀0.42 m) large (⌀6 aperture telescopes. In particular, telescopes (SATs) focus on primordial B-mode polarization. To this end, SATs employ CHWP to modulate incident light 8 Hz, suppressing...
Porphyromonas gingivalis is a suspected pathogen in rapidly progressive periodontitis (RPP). We have determined the anti-P. serum immunoglobulin G (IgG) isotype response and avidity subclass titer distributions for 30 RPP patients age-, sex-, race-matched healthy subjects by using enzyme-linked immunosorbent assay technology. Patients control were classified as seropositive if their total IgG to P. was twofold or more than median subjects. The predominant antibody responses both IgG2 IgG3,...
EBEX is a NASA-funded balloon-borne experiment designed to measure the polarization of cosmic microwave background (CMB). Observations will be made using 1432 transition edge sensor (TES) bolometric detectors read out with frequency multiplexed SQuIDs. observe in three bands centered at 150, 250, and 410 GHz, 768, 384, 280 each band, respectively. This broad coverage provide valuable information about polarized foreground signals from dust. The sky modulated an achromatic half wave plate...
Measurements of cosmic microwave background (CMB) spectral distortions have profound implications for our understanding physical processes taking place over a vast window in cosmological history. Foreground contamination is unavoidable such measurements and detailed signal–foreground separation will be necessary to extract science. In this paper, we present Markov chain Monte Carlo based distortion detection forecasts the presence Galactic extragalactic foregrounds range possible...
A millimeter-wave survey over half the sky, that spans frequencies in range of 30 to 350 GHz, and is both an order magnitude deeper higher-resolution than currently funded surveys would yield enormous gain understanding fundamental physics astrophysics. By providing such a deep, high-resolution (about 0.5 uK-arcmin noise 15 arcsecond resolution at 150 GHz), CMB-HD will enable major advances. It allow 1) use gravitational lensing primordial microwave background map distribution matter on...
Inflation may provide unique insight into the physics at highest available energy scales that cannot be replicated in any realistic terrestrial experiment. Features primordial power spectrum are generically predicted a wide class of models inflation and its alternatives, observationally one most overlooked channels for finding evidence non-minimal inflationary models. Constraints from observations cosmic microwave background cover widest range feature frequencies, but sensitive constraints...
We present an analysis of the longest timescale microlensing events discovered by MACHO Collaboration during a 7 year survey Galactic bulge. find 6 that exhibit very strong parallax signals due, in part, to accurate photometric data from GMAN and MPS collaborations. The fit parameters are used likelihood analysis, which is able estimate distance masses lens objects based upon standard model velocity distribution. This indicates most likely 5 lenses > 1 Msun, suggests substantial fraction...
We present observations of microlensing event MACHO-98-BLG-35 which reached a peak magnification factor almost 80. These by the Microlensing Planet Search (MPS) and MOA Collaborations place strong constraints on possible planetary system lens star show intriguing evidence for low mass planet with fraction $4\times 10^{-5} \leq ε\leq 2\times 10^{-4}$. A giant $ε= 10^{-3}$ is excluded from 95% region between 0.4 2.5 $R_E$ star, where Einstein ring radius lens. This exclusion more extensive...
We fit the data for binary lens microlensing event MACHO 98-SMC-1 from five different collaborations and find two distinct solutions characterized by separation d mass ratio q: (d,q) = (0.54,0.50) (3.65,0.36), where is in units of Einstein radius. However, relative proper motion very similar solutions, 1.30 km s-1 kpc-1 1.48 kpc-1, thus confirming that Small Magellanic Cloud. The close can be either rotating or approximately static but wide must at to its maximum allowed rate consistent with...
We present a broadband waveguide ortho-mode transducer for the WR10 band that was designed CLOVER, an astrophysics experiment aiming to characterize polarization of cosmic microwave background radiation. The design, based on turnstile junction, manufactured and then tested using millimeter-wave vector network analyzer. average measured return loss isolation were -22 dB -45 dB, respectively, across entire
Hysteretic behavior was studied in a series of Fe thin films, grown by molecular beam epitaxy, having different grain sizes and on substrates. Major minor loops first order reversal curves (FORCs) were collected to investigate magnetization mechanisms domain under magnetic histories. The loop coefficient major coercivity increase with decreasing size due higher defect concentration resisting wall movement. First allowed estimation the contribution irreversible reversible susceptibilities...
CMB-S4 is a proposed experiment to map the polarization of Cosmic Microwave Background (CMB) nearly cosmic variance limit for angular scales that are accessible from ground. The science goals and capabilities in illuminating inflation, measuring sum neutrino masses, searching relativistic relics early universe, characterizing dark energy matter, mapping matter distribution universe have been described Science Book. This Technology Book companion volume ambitious CMB-S4, "Stage-4" experiment,...
The Probe of Inflation and Cosmic Origins (PICO) is an imaging polarimeter that will scan the sky for 5 years in 21 frequency bands spread between 799 GHz. It produce full-sky surveys intensity polarization with a final combined-map noise level 0.87 $\mu$K arcmin required specifications, equivalent to 3300 Planck missions, our current best-estimate would have 0.61 (6400 missions). PICO either determine energy scale inflation by detecting tensor scalar ratio at $r=5\times 10^{-4}~(5\sigma)$,...
The Probe of Inflation and Cosmic Origins (PICO) is a NASA-funded study Probe-class mission concept. toplevel science objectives are to probe the physics Big Bang by measuring or constraining energy scale inflation, fundamental number light particles in Universe sum neutrino masses, measure reionization history Universe, understand mechanisms driving cosmic star formation history, galactic magnetic field. PICO would have multiple frequency bands between 21 799 GHz, survey entire sky,...
CMB-HD is a proposed millimeter-wave survey over half the sky that would be ultra-deep (0.5 uK-arcmin) and have unprecedented resolution (15 arcseconds at 150 GHz). Such answer many outstanding questions about fundamental physics of Universe. Major advances 1.) use gravitational lensing primordial microwave background to map distribution matter on small scales (k~10 h Mpc^(-1)), which probes dark particle properties. It will also allow 2.) measurements thermal kinetic Sunyaev-Zel'dovich...
Abstract The Simons Observatory (SO) is a cosmic microwave background survey experiment that includes small-aperture telescopes (SATs) observing from an altitude of 5200 m in the Atacama Desert Chile. SO SATs will cover six spectral bands between 27 and 280 GHz to search for primordial B-modes sensitivity σ ( r ) = 0.002, with quantified systematic errors well below this value. Each SAT self-contained cryogenic telescope 35° field view, 42 cm diameter optical aperture, 40 K half-wave plate,...
Abstract The Simons Observatory will map the temperature and polarization over half of sky at millimeter wavelengths in six spectral bands from Atacama Desert Chile. These data provide new insights into genesis, content, history our Universe, astrophysics galaxies galaxy clusters, objects solar system, time-varying astrophysical phenomena. This ambitious instrument suite, initially comprising three 0.5 m diameter small aperture telescopes one 6 large telescope, is designed using a common...
The Simons Observatory (SO) is a ground-based cosmic microwave background (CMB) survey experiment that currently consists of three 0.42m small-aperture telescopes (SATs) and one 6m large-aperture telescope (LAT), located at an elevation 5200m in the Atacama Desert Chile. At LAT's focal plane, SO will install >62,000 transition-edge sensor detectors across 13 optics tubes (OTs) within Large Aperture Telescope Receiver (LATR), largest cryogenic camera ever built to observe CMB. Here we report...