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Brown, Michael

Publications and source records attributed to Brown, Michael.

15 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Editorial: Resolving atmospheric flow in complex environments: recent experiments in terrain and forest canopies

The characterization of atmospheric flows in complex environments, which may include steep terrain slopes and heterogeneous vegetation and/or forest cover, is a long-standing challenge in boundary-layer meteorology. Atmospheric observations are complicated by the presence of transient, terrain-induced flow features, forest-canopy-atmosphere interactions, and atmospheric stability effects, not to mention the logistical hurdles involved with instrument deployment, data analysis, and quality control. Furthermore, challenges in atmospheric modeling arise due to numerical errors associated with complex terrain flows, as well as reliance on simplified parameterizations for unresolved processes such as turbulent mixing and land-surface or forest-canopy-atmosphere interactions. These modeling challenges are exacerbated in the so-called “gray zone,” wherein features of interest have length scales that are similar to the model grid spacing, or when the principal flow layer is smaller than the grid spacing (e.g., slope flows).

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Mark-18A Cold Runs

The Savannah River National Laboratory (SRNL) is tasked by the National Nuclear Security Administration (NNSA) to recover highly valued isotopes from irradiated Mark-18A (Mk-18A) targets. The Savannah River Site (SRS) has sixty-five Mk-18A targets available for the recovery of the high valued materials. The sixty-five Mk-18A targets are currently stored in the L-Area Basin and will be removed one at a time and individually transported to SRNL. Upon receipt at SRNL, the Mk-18A target material will be removed from the confinement, dissolved, chemically separated, and calcined to a stable oxide. The flowsheet is designed to recover the plutonium as well as the trivalent actinides. The remaining unrecovered material will be discarded to the high activity drain (HAD) system in SRNL. A specially designed cask was procured for transport of the targets from L-Area to SRNL. Once received at SRNL, the targets will be loaded into the back of Cell 7 and resized as they enter the cell. The resized targets (1/4 lengths) will then be processed one at a time through the following processes: caustic dissolution and filtration; acidic dissolution and filtration, Reillex anion exchange, diglycolamide (DGA) cation exchange; and DGA calcination. This processing will result in two product streams. The first is an aqueous plutonium solution which will be removed from the shielded cells and taken to a glovebox for further purification and conversion to an oxide. The second is a calcined oxide containing the Am and Cm as well as other lanthanide fission products which will be removed from the shielded cells using a bagless transfer system. Both materials will be packaged for shipment to Oak Ridge National Laboratory (ORNL). All equipment to carry out this process was designed, procured or fabricated, and installed in a mock-up facility (716-4A) at SRS to allow for simulation testing in a non-radioactive area. This equipment was then dismantled and transferred from 716-4A to 773-A and installed in the SRNL Shielded Cells. After installation in the shielded cells facility testing was performed using water followed by surrogates and cold chemicals. Issues were identified during these evaluations, including equipment issues as well as technical challenges. Many of the issues were rectified during performance of the cold runs, and the remaining have a resolution identified. Table ES-1 provides a summary of all issues identified during the cold run operations, as well as the status and identified resolutions to outstanding issues.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2023

Clustering of red sequence galaxies in the fourth data release of the Kilo-Degree Survey

We present a sample of luminous red sequence galaxies as the basis for a study of the large-scale structure in the fourth data release of the Kilo-Degree Survey. The selected galaxies are defined by a red sequence template, in the form of a data-driven model of the colour-magnitude relation conditioned on redshift. In this work, the red sequence template was built using the broad-band optical+near infrared photometry of KiDS-VIKING and the overlapping spectroscopic data sets. The selection process involved estimating the red sequence redshifts, assessing the purity of the sample and estimating the underlying redshift distributions of redshift bins. After performing the selection, we mitigated the impact of survey properties on the observed number density of galaxies by assigning photometric weights to the galaxies. We measured the angular two-point correlation function of the red galaxies in four redshift bins and constrain the large-scale bias of our red sequence sample assuming a fixed ΛCDM cosmology. We find consistent linear biases for two luminosity-threshold samples (‘dense’ and ‘luminous’). We find that our constraints are well characterised by the passive evolution model.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Analysis of wave mode content in fully turbulent, moderately collisional plasma laboratory experiment and kinetic simulation

Our major goal for the project was to make magnetic field and plasma density fluctuation measurements using identical diagnostic and acquisition setups on two different laboratory-based turbulent plasma devices: SSX at Swarthmore College and a new plasma source in development at Bryn Mawr College (BMX). We used single-point correlation and k-filtering metrics using these experimental measurements. These metrics were compared to kinetic simulations of the experimental environments in order to determine wave mode content of the laboratory turbulence.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2022

We Must Stop Fossil Fuel Emissions to Protect Permafrost Ecosystems

Climate change is an existential threat to the vast global permafrost domain. The diverse human cultures, ecological communities, and biogeochemical cycles of this tenth of the planet depend on the persistence of frozen conditions. The complexity, immensity, and remoteness of permafrost ecosystems make it difficult to grasp how quickly things are changing and what can be done about it. Here, we summarize terrestrial and marine changes in the permafrost domain with an eye toward global policy. While many questions remain, we know that continued fossil fuel burning is incompatible with the continued existence of the permafrost domain as we know it. If we fail to protect permafrost ecosystems, the consequences for human rights, biosphere integrity, and global climate will be severe. The policy implications are clear: the faster we reduce human emissions and draw down atmospheric CO 2 , the more of the permafrost domain we can save. Emissions reduction targets must be strengthened and accompanied by support for local peoples to protect intact ecological communities and natural carbon sinks within the permafrost domain. Some proposed geoengineering interventions such as solar shading, surface albedo modification, and vegetation manipulations are unproven and may exacerbate environmental injustice without providing lasting protection. Conversely, astounding advances in renewable energy have reopened viable pathways to halve human greenhouse gas emissions by 2030 and effectively stop them well before 2050. We call on leaders, corporations, researchers, and citizens everywhere to acknowledge the global importance of the permafrost domain and work towards climate restoration and empowerment of Indigenous and immigrant communities in these regions.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Efficient Thermal Processes Using Alternating Electromagnetic Field for Methodical and Selective Release of Hydrogen Isotopes

The controlled and selective release of hydrogen isotopes from Lanthanum-Nickel-Aluminum (LANA) materials was achieved using an alternating electromagnetic field (AEMF). Here, in the presence of the AEMF, the rate of desorption for D 2 was faster than for H 2 . In a closed system, compared to control experiments with helium, hydrogen-loaded LANA samples showed a significant increase in pressure which illustrates the desorption of hydrogen from the applied AEMF. An exponential increase in the hydrogen release rate was observed with increased AEMF strength. Additionally, hydrogen release from LANA confined in a subzero environment (-78°C) using an AEMF was demonstrated. These results demonstrate that the LANA material can be heated directly using alternating electromagnetic fields rather than indirectly to rapidly and selectively desorb hydrogen isotopes. The rapid response and difference in desorption kinetics for different hydrogen isotopes in the presence of the alternating electromagnetic fields provide a promising pathway for applications requiring controlled release of hydrogen and separation of its isotopes.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2020

Taylor State Merging at SSX: Experiment and Simulation

We describe experiments and simulations of dynamical merging with two Taylor state plasmas in a Swarthmore Spheromak Experiment (SSX) device. Taylor states are formed by magnetized plasma guns at opposite ends of the device. We performed experiments with Taylor states of both senses of magnetic helicity (right-handed twist or left-handed twist). We present results of both counter-helicity merging (one side left-handed, the other right-handed) and co-helicity merging (both sides left-handed). Experiments show significant ion heating, consistent with magnetic reconnection. We suggest that the merged, warm state could be a suitable target for future magneto-inertial fusion experiments. Magnetohydrodynamic simulations of these experiments reveal the structure of the final relaxed, merged state.

Brown, Michael↗
DOE OSTI2020

Controlled Release of Hydrogen Isotopes from Hydride-Magnetic Nanomaterials

In this work, hydrogen isotopes in the form of protium and deuterium were rapidly desorbed from magnetic-hydride iron oxide-palladium (Fe 2 O 3 -Pd) hybrid nanomaterials using an alternating magnetic field (AMF). Palladium, a hydride material with a well-known hydrogen isotope effect, was deposited on Fe 2 O 3 magnetic nanoparticle support by solution chemistries and used as a hydrogen isotope storage component. The morphological, structural, optical, and magnetic studies reveal that the Fe 2 O 3 -Pd nanoparticles (NPs) are hybrid structures exhibiting both hydrogen isotope storage (Pd) and magnetic (Fe 2 O 3 ) properties. The hydrogen isotope sorption/desorption behavior of metal hydride-magnetic nanomaterials was assessed by isothermal pressure-composition response curves (isotherms). The amount and rate of hydrogen isotope gas release was tuned by simply adjusting the strength of the magnetic field strength applied. Protium and deuterium displayed a similar loading capacity, namely H/M 0.55 and H/M=0.45, but different plateau pressures. Significant differences in the kinetics of release for protium and deuterium during magnetic heating were observed. A series of magnetically induced charge-discharge cycling experiments were conducted showing that this is a highly reproducible and robust process

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Real-time predictive sensor network and deployable sensor

Deployable, predictive sensor systems may form a sensor network configured to provide environmental data in real-time or near-real-time. The sensors may be deployable sensors that can be launched and/or airdropped in areas that may be contaminated or otherwise unsafe for humans to enter. The predictive sensor network may include sensor tetrapods that may include anemometers for measuring wind speed, radiation sensors, gaseous contaminant sensors, biological sensors, and/or any other desired sensor type. These sensors may inform wind, transport and dispersion models in real-time. The sensor tetrapods may be satellite-linked, linked via a cellular network, linked via RF line-of-sight, a wireless communication link, and/or another compatible wireless network to a wind, dispersal, and deposition model that provides a dispersion pattern, a deposition pattern, and a wind pattern to enable a high-quality remote assessment of the changing scene in real-time.

Hehlen, Markus↗
DOE OSTI2018

Temperature and Lifetime Measurements in the SSX Wind Tunnel

We describe ion and electron temperature measurements in the Swarthmore Spheromak Experiment (SSX) MHD wind tunnel with the goal of understanding limitations on the lifetime of our Taylor-state plasma. A simple model based on the equilibrium eigenvalue and Spitzer resistivity predicted the lifetime satisfactorily during the first phase of the plasma evolution. We measured an average T e along a chord by taking the ratio of the C I I I 97.7 nm to C I V 155 nm line intensities using a vacuum ultraviolet (VUV) monochromator. We also recorded local measurements of T e and n e using a double Langmuir probe in order to inform our interpretation of the VUV data. Our results indicated that the plasma decayed inductively during a large part of the evolution. Ion Doppler spectroscopy measurements suggested that ions cooled more slowly than would be expected from thermal equilibration with the electrons, which maintained a constant temperature throughout the lifetime of the plasma.

Kaur, Manjit (ORCID:0000000160086676)↗
NASA NTRS2016

Solar System Observations with the James Webb Space Telescope

The James Webb Space Telescope (JWST) will enable a wealth of new scientific investigations in the near- and mid-infrared, with sensitivity and spatial/spectral resolution greatly surpassing its predecessors. In this paper, we focus upon Solar System science facilitated by JWST, discussing the most current information available concerning JWST instrument properties and observing techniques relevant to planetary science. We also present numerous example observing scenarios for a wide variety of Solar System targets to illustrate the potential of JWST science to the Solar System community. This paper updates and supersedes the Solar System white paper published by the JWST Project in 2010. It is based both on that paper and on a workshop held at the annual meeting of the Division for Planetary Sciences in Reno, NV, in 2012.

Kuiper belt↗
NASA NTRS2014

Solar System Observations with JWST

The James Webb Space Telescope will enable a wealth of new scientific investigations in the near- and mid- infrared, with sensitivity and spatial-spectral resolution greatly surpassing its predecessors. In this paper, we focus upon Solar System science facilitated by JWST, discussing the most current information available concerning JWST instrument properties and observing techniques relevant to planetary science. We also present numerous example observing scenarios for a wide variety of Solar System targets to illustrate the potential of JWST science to the Solar System community. This paper updates and supersedes the Solar System white paper published by the JWST Project in 2010 (Lunine et al., 2010). It is based both on that paper and on a workshop held at the annual meeting of the Division for Planetary Sciences in Reno, NV in 2012.

Infrared observations↗