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DOE OSTI2025

Guiding center equations for the magnetic dipole

Since the discovery of Van Allen radiation belts in the 1960s, observations of energetic ions trapped in the Earth's dipole magnetic field have illustrated the remarkable confinement properties of this configuration. As such, it has been used for confining a hot plasma for nuclear fusion studies, starting from the pioneering work of Bo Lehnert and Akira Hasegawa, in the Levitated Dipole Experiment (LDX) at MIT until 2011 and in the RT-1 experiment at the University of Tokyo. More recently, the dipole has been subject to a renewed interest for fusion studies by a couple of startups and for smaller applications as a cold plasma source. While the equilibrium and magneto-hydrodynamic stability of the dipole have been investigated quite in detail, neoclassical properties of the dipole are comparatively much less known: the dipole is more known in geophysics than in fusion science. For this reason, in this paper, we propose a set of Hamiltonian, guiding-center equations to describe the motion of electrons and ions in a magnetic dipole configuration. We also developed a code, and we show the main features of particle motion, benchmarking our results with the analytical solutions for the bounce and precession motion, which are well documented in the literature. We also draw some general conclusions for the neoclassical transport in usual toroidal confinement schemes, such as the tokamak and the stellarator, pointing out the unique advantages of the dipole in confining energetic particles.

Hamiltonian mechanics↗

DOE OSTI2021

Fog Formation Related to Gravity Currents Interacting with Coastal Topography

An interesting mixing-fog event was identified during IOP7 of the C-FOG project, where a cold front arriving from the north-east collided with the Downs peninsula in Ferryland, Newfoundland, to produce foggy conditions. A comprehensive set of field observations suggests that this collision caused turbulent mixing of nearly saturated ambient air with an almost saturated cold front, creating conditions for mixing fog. Additionally, laboratory experiments were performed to study the interaction of lock-exchange induced gravity currents with a (rectangular) obstacle to delve into physical processes underlying this phenomenon. Instantaneous velocity and density fields were obtained using particle image velocimetry and planar laser-induced fluorescence. The observations suggest that the obstacle starts affecting the approaching gravity-current propagation at an upstream distance of 2 H and, upon collision, the mixing is taking place over a spatial scale of 0.83 H , where H is the depth of the ambient fluid layer. The time for largerscale turbulent stirring to permeate to the smallest scales of turbulence and activate the condensation nuclei was estimated as 3t * , where t* = √H/g' is the intrinsic time scale of the gravity current and g' the reduced gravity. Extrapolation of results to IOP7 showed a good agreement with observations.

54 ENVIRONMENTAL SCIENCES↗

NASA NTRS2016

Interdecadal Trichodesmium Variability in Cold North Atlantic Waters

Studies of the nitrogen cycle in the ocean generally assume that the distribution of the marine diazotroph, Trichodesmium, is restricted to warm, tropical, and subtropical oligotrophic waters. Here we show evidence that Trichodesmium are widely distributed in the North Atlantic. We report an approximately vefold increase during the 1980s and 1990s in Trichodesmium presence near the British Isles with respect to the average over the last 50 years. A potential explanation is an increase in the Saharan dust source starting in the 1980s, coupled with changes in North Atlantic winds that opened a pathway for dust transport. Results from a coarse-resolution model in which winds vary but iron deposition is climatologically fixed suggest frequent nitrogen limitation in the region and reversals of the Portugal current, but it does not simulate the observed changes in Trichodesmium. Our results suggest that Trichodesmium may be capable of growth at temperatures below 20C and challenge assumptions about their latitudinal distribution. Therefore, we need to reevaluate assumptions about the temperature limitations of Trichodesmium and the dinitrogen (N2) xation capabilities of extratropical strains, which may have important implications for the global nitrogen budget.

Rivero-Calle, Sara↗

DOE OSTI2023

Metal-insulator transition and magnetism of SU(3) fermions in the square lattice

We study the SU(3) symmetric Fermi-Hubbard model (FHM) in the square lattice at 1/3-filling using numerically exact determinant quantum Monte Carlo and numerical linked-cluster expansion techniques. We present the different regimes of the model in the T–U plane, which are characterized by local and short-range correlations, and capture signatures of the metal-insulator transition and magnetic crossovers. These signatures are detected as the temperature scales characterizing the rise of the compressibility, and an interaction-dependent change in the sign of the diagonal spin-spin correlation function. The analysis of the compressibility estimates the location of the metal-insulator quantum critical point at U c /t ~ 6, and provides a temperature scale for observing Mott physics at finite T. Furthermore, from the analysis of the spin-spin correlation function we observe that for U/t ≳ 6 and T ~ J = 4⁢t 2 /U there is a development of a short-range two-sublattice (2SL) antiferromagnetic structure, as well as an emerging three-sublattice (3SL) antiferromagnetic structure as the temperature is lowered below T/J ≲ 0.57. This crossover from 2SL to 3SL magnetic ordering agrees with Heisenberg limit predictions, and has observable effects on the density of on-site pairs. Finally, we describe how the features of the regimes in the T–U plane can be explored with alkaline-earth-like atoms in optical lattices with currently achieved experimental techniques and temperatures. Furthermore, the results discussed in this paper provide a starting point for the exploration of the SU(3) FHM upon doping.

74 ATOMIC AND MOLECULAR PHYSICS↗

DOE OSTI2023

Quick Start to Electrifying Your School Bus Fleet

Learn how electric school buses can work for your district by understanding the basics of electrification. Understand what is needed to electrify your fleet, how much it costs, and how the process will effect your greenhouse gas emission impacts.

ADVANCED PROPULSION SYSTEMS↗

NASA NTRS1998

A Long-Term Space Astrophysics Research Program. An X-Ray Perspective of the Components and Structure of Galaxies

We present optical and archival X-ray data on the disturbed morphology radio elliptical NGC 1316 (Fornax A) that displays numerous low surface brightness shells, loops and tails. An extended (81x27 min or 9x3 kpc) emission line region (EELR) at a projected distance of 35 kpc from the nucleus has been discovered in a approximately 9Ox35 kpc, approximately 3.Ox1O(solar luminosity(B)) tidal tail. The position and extreme size of the EELR suggest it is related to the merger process. We suggest that the ionization mechanism of the EELR is shock excitation, and the gas is remnant from the merger progenitor. X-ray emission is detected near two tidal tails. Hot, approximately 5 x 10(exp 6)K gas is probably the predominant gas component in the tidal tail ISM. However based on the current tidal tail (cold + warm + hot) gas mass, a large fraction of the tidal tail progenitor gas may already reside in the nucleus of NGC 1316. The numerous and varied tidal tail system suggests that a disk-disk or disk-E merger could have taken place greater than or equal to 1 Gyr ago, whilst a low mass, gas rich galaxy started to merge approximately 0.5 Gyr ago.

Fabbiano, G.↗

DOE OSTI2022

Flex-PCB Quench Antenna Developments at FNAL

We report flexible printed-circuit-board-based quench antenna arrays have been developed at FNAL since 2017. They proved to be low-noise, low-cost, sensitive, and non-invasive sensors for quench characterization in superconducting magnets, having the potential to extend even to quench detection. Starting with applications of small area sensors of this type, we have explored feasibility for operations at high pressure, and have invested in multi-channel quench antenna arrays covering the complete area of the innermost magnet layer of the conductor. We've also tested and optimized sensor geometry and relative orientations to increase sensitivity and spatial resolution. Beyond developments of warm and cold bore antennas, we've progressed to concepts which attach quench antennas to the conductor surfaces of accelerator magnets. Multiple programs and projects at FNAL and collaborating institutions benefited from this work already and our plans target further extensions of capabilities and applicability of these devices. In this paper we present the logic behind the development steps taken so far, status of our work and direction of near-term research on quench antennas at Fermilab.

43 PARTICLE ACCELERATORS↗

NASA NTRS2009

Mars Balloon Flight Test Results

This paper describes a set of four Earth atmosphere flight test experiments on prototype helium superpressure balloons designed for Mars. Three of the experiments explored the problem of aerial deployment and inflation, using the cold, low density environment of the Earth's stratosphere at an altitude of 30-32 km as a proxy for the Martian atmosphere. Auxiliary carrier balloons were used in three of these test flights to lift the Mars balloon prototype and its supporting system from the ground to the stratosphere where the experiment was conducted. In each case, deployment and helium inflation was initiated after starting a parachute descent of the payload at 5 Pa dynamic pressure, thereby mimicking the conditions expected at Mars after atmospheric entry and high speed parachute deceleration. Upward and downward looking video cameras provided real time images from the flights, with additional data provided by onboard temperature, pressure and GPS sensors. One test of a 660 cc pumpkin balloon was highly successful, achieving deployment, inflation and separation of the balloon from the flight train at the end of inflation; however, some damage was incurred on the balloon during this process. Two flight tests of 12 m diameter spherical Mylar balloons were not successful, although some lessons were learned based on the failure analyses. The final flight experiment consisted of a ground-launched 12 m diameter spherical Mylar balloon that ascended to the designed 30.3 km altitude and successfully floated for 9.5 hours through full noontime daylight and into darkness, after which the telemetry system ran out of electrical power and tracking was lost. The altitude excursions for this last flight were +/-75 m peak to peak, indicating that the balloon was essentially leak free and functioning correctly. This provides substantial confidence that this balloon design will fly for days or weeks at Mars if it can be deployed and inflated without damage.

deployment↗

DOE OSTI2025

Capacity Design Method for Integrated Convective/Radiant Terminals to Guarantee Overall and Local Environment

To achieve energy efficiency in the operation of heating devices and ensure thermal comfort in indoor environments, the integrated convective/radiant terminals have become an important development direction for heating systems. This study selected a 14 m 2 bedroom hot summer and cold winter region in China as a case study. Computational Fluid Dynamics (CFD) methodology was used to investigate the design of integrated convective/radiant terminals to ensure thermal comfort for both the entire room and partial space. The results indicate that focusing on partial space during the steady-state stage can achieve energy savings of 31.1% compared to guaranteeing the entire room. Additionally, during the start-up stage, there is a significant reduction of convective unit capacity by 17.6% when the start-up time is 15 minutes. These findings provide data support for the design and engineering applications of products of integrated convective/radiant terminals. Besides, the excess convection ratios for the entire room and partial space are specified as 0.69 to 0.80 and 0.73 to 0.83, respectively.

Chi, Junjie↗

NASA NTRS1973

Improvements in and test results for the 2 to 15 kilowatt Brayton cycle electrical subsystem

The electrical subsystem of the 2- to 15-kW Brayton power conversion system consists of the auxiliary electrical equipment required for an integrated, self-contained system. For the last 2 years the electrical subsystem has been undergoing extensive tests. The first year of testing resulted in determining the performance characteristics of the electrical subsystem. During the second year several significant changes and improvements were investigated. An inverter designed for motor starting the alternator performed successfully. Some of the changes that have been made are a new alternator speed pickup, which is independent of the alternator output voltage; new, more efficient power supplies for the control system; and a volts-per-hertz reference for the alternator voltage regulator. Test data were taken on the temperature distribution of the electrical subsystem at startup conditions over a cold-plate temperature range of 25 to -50 C.

Vrancik, J. E.↗

NASA NTRS2001

Predictability of Zonal Means During Boreal Summer

This study examines the predictability of seasonal means during boreal summer. The results are based on ensembles of June-July-August (JJA) simulations (started in mid May) carried out with the NASA Seasonal-to-Interannual Prediction Project (NSIPP-1) atmospheric general circulation model (AGCM) forced with observed sea surface temperatures (SSTS) and sea ice for the years 1980-1999. We find that the predictability of the JJA extra-tropical height field is primarily in the zonal mean component of the response to the SST anomalies. This contrasts with the cold season (January-February-March) when the predictability of seasonal means in the boreal extratropics is primarily in the wave component of the El Nino/Southern Oscillation (ENSO) response. Two patterns dominate the interannual variability of the ensemble mean JJA zonal mean height field. One has maximum variance in the tropical/subtropical upper troposphere, while the other has substantial variance in middle latitudes of both hemispheres. Both are symmetric with respect to the equator. A regression analysis suggests that the tropical/subtropical pattern is associated with SST anomalies in the far eastern tropical Pacific and the Indian Ocean, while the middle latitude pattern is forced by SST anomalies in the tropical Pacific just east of the dateline. The two leading zonal height patterns are reproduced in model runs forced with the two leading JJA SST patterns of variability. A comparison with observations shows a signature of the middle latitude pattern that is consistent with the occurrence of dry and wet summers over the United States. We hypothesize that both patterns, while imposing only weak constraints on extratropical warm season continental-scale climates, may play a role in the predilection for drought or pluvial conditions.

Schubert, Siegfried↗

NASA NTRS2005

Performance test results of a skutterudite-based unicouple with a metallic coating

A performance test of a Skutterudite-based unicouple (MAY-04) with a metallic coating to suppress the sublimation of antimony from the legs near the hot junction is performed in vacuum (~ 9 x10-7 torr) for ~ 2,000 hours at hot and cold junction temperatures of 892.1 + 11.9 K and 316.1 + 5.5 K, respectively. The p-leg is made of CeFe3.5Co0.5Sb12 and the n-leg is made of CoSb3. Presented are the measured voltage-current characteristics, electrical power, open-circuit voltage, and Seebeck coefficients of the legs as functions of cumulative test time. Also presented is the estimate of the conversion efficiency, shortly (~ 96 hrs) after the start of test. To demonstrate the effectiveness of the metallic coating, the measurements for MAY-04 are compared with those of two uncoated unicouples of the same leg materials (MAR-03 and JUN-03), which had been tested earlier. The cross-sectional areas of the legs in MAY-04 are larger than those in MAR-03 and JUN-03, tested in argon cover gas at ~ 0.051-0.068 MPa for 450 and 1200 hours, respectively. The open circuit voltage, Voc (204 mV) of MAY-04 at Beginning-Of-Test (BOT) is almost the same as that of MAR-03, but higher than that of JUN-03 (~180 mV). Although the argon gas effectively decreased antimony loss from legs of MAR-03 and JUN-03, marked degradations in performance occurred with time in these tests. Conversely, the metallic coating in MAY-04 effectively reduced the performance degradation with cumulative test time. The estimated peak efficiency of MAY-04, shortly after BOT (10.65%) is only ~ 0.37 percentage point lower than the theoretical value, assuming zero side heat losses and zero contact resistance per leg. The peak power of MAY- 04 decreased by only ~12%, from its BOT value of ~1.6 We to ~ 1.4 We after ~ 2,000 of cumulative testing

Caillat, Thierry↗

NASA NTRS2015

Exposing Microorganisms in the Stratosphere for Planetary Protection Project

Earths stratosphere is similar to the surface of Mars: rarified air which is dry, cold, and irradiated. E-MIST is a balloon payload that has 4 independently rotating skewers that hold known quantities of spore-forming bacteria isolated from spacecraft assembly facilities at NASA. Knowing the survival profile of microbes in the stratosphere can uniquely contribute to NASA Planetary Protection for Mars.Objectives 1. Collect environmental data in the stratosphere to understand factors impacting microbial survival. 2. Determine of surviving microbes (compared to starting quantities). 3. Examine microbial DNA mutations induced by stratosphere exposure.

Technology Portfolio System↗

NASA NTRSDate not supplied

TPSAS-NF1676L-26990-DND

The warm phase ENSO event (El Nino) of 2015/2016 produced significant perturbations to the Tropical Pacific, from sea surface to tropical tropopause and above. Although there have been 3 El Ninos during the modern "A-Train" era, the most recent El Nino started earlier in the year, was located farther west and was stronger than those of 2006/7 and 2009/10. Using A-Train observations, we show that during the 2015/16 El Nino the center of convective activity moved from the tropical western Pacific (TWP) to the central Pacific, just to the east of the dateline. This caused a record amount of cloud ice to occur near or above the environmental cold-point tropopause. Coincidently there was a large positive anomaly in tropical lower stratospheric water vapor, warming of the tropopause over the TWP, and changes to the stratospheric QBO. Using ten+ years of A-Train data and the MERRA-2 reanalysis fields, we explore the observed relationships between the 3D patterns of cloud ice, water vapor, ozone, aerosols and other trace gases in the tropical Pacific, and correlations with the ENSO and QBO cycles.

Melody A. Avery↗

NASA NTRS2008

From the Big Bang to the Nobel Prize and on to James Webb Space Telescope

The Big Bang 13.7 billion years ago started the expansion of our piece of the universe, and portions of it stopped expanding and made stars, galaxies, planets, and people. I summarize the history of the universe, and explain how humans have learned about its size, its expansion, and its constituents. The COBE (Cosmic Background Explorer) mission measured the remnant heat radiation from the Big Bang, showed that its color (spectrum) matches the predictions perfectly, and discovered hot and cold spots in the radiation that reveal the primordial density variations that enabled us to exist. My current project, the James Webb Space Telescope (JWST), is the planned successor to the Hubble Space Telescope, and will extend its scientific discoveries to ever greater distances and ever closer to the Big Bang itself. Its infrared capabilities enable it to see inside dust clouds to study the formation of stars and planets, and it may reveal the atmospheric properties of planets around other stars. Planned for launch in 2013, it is an international project led by NASA along with the European and Canadian Space Agencies.

Mather, John C.↗

NASA NTRS2009

Lunar Reconnaissance Orbiter (LRO) Rapid Thermal Design Development

The Lunar Reconnaissance Orbiter (LRO) project had a rapid development schedule starting with project conception in spring of 2004, instrument and launch vehicle selection late in 2005 and then launch in early 2009. The lunar thermal environment is one of the harshest in our solar system with the heavy infrared loading of the moon due to low albedo, lack of lunar atmosphere, and low effective regolith conduction. This set of constraints required a thermal design which maximized performance (minimized radiator area and cold control heater power) and minimized thermal hardware build at the orbiter level (blanketing, and heater service). The orbiter design located most of the avionics on an isothermalized heat pipe panel called the IsoThermal Panel (ITP). The ITP was coupled by dual bore heat pipes to an Optical Solar Reflector (OSR) covered heat pipe radiator. By coupling all of the avionics to one system, the hardware was simplified. The seven instruments were mainly heritage instruments which resulted in their desired radiators being located by their heritage design. This minimized instrument redesigns and therefore allowed them to be delivered earlier, though it resulted in a more complex orbiter level blanket and heater service design. Three of the instruments were mounted on a tight pointing M55J optical bench that needed to be covered in heaters to maintain pointing. Two were mounted to spacecraft controlled radiators. One was mounted to the ITP Dual Bores. The last was mounted directly to the bus structure on the moon facing panel. The propulsion system utilized four-20 pound insertion thrusters and eight-5 pound attitude control thrusters (ACS) in addition to 1000 kg of fuel in two large tanks. The propulsion system had a heater cylinder and a heated mounting deck for the insertion thrusters which coupled most of the propulsion design together simplifying the heater design. The High Gain Antenna System (HGAS) and Solar Array System (SAS) used dual axis actuator gimbal systems. HGAS required additional boom heaters to cool the approximately 10 W of RF losses thru the rotary joints and wave guides from the 40 W Ka system. By design this module needed a fair amount of heater, blanketing, and radiator complexity. The SAS system required a separate cable wrap radiator to help cool the Solar Array harness which dissipated 30 W thru the actuators and cable wraps. This module also was complex.

Baker, Charles↗

NASA NTRS2007

Deep Space Network Antenna Logic Controller

The Antenna Logic Controller (ALC) software controls and monitors the motion control equipment of the 4,000-metric-ton structure of the Deep Space Network 70-meter antenna. This program coordinates the control of 42 hydraulic pumps, while monitoring several interlocks for personnel and equipment safety. Remote operation of the ALC runs via the Antenna Monitor & Control (AMC) computer, which orchestrates the tracking functions of the entire antenna. This software provides a graphical user interface for local control, monitoring, and identification of faults as well as, at a high level, providing for the digital control of the axis brakes so that the servo of the AMC may control the motion of the antenna. Specific functions of the ALC also include routines for startup in cold weather, controlled shutdown for both normal and fault situations, and pump switching on failure. The increased monitoring, the ability to trend key performance characteristics, the improved fault detection and recovery, the centralization of all control at a single panel, and the simplification of the user interface have all reduced the required workforce to run 70-meter antennas. The ALC also increases the antenna availability by reducing the time required to start up the antenna, to diagnose faults, and by providing additional insight into the performance of key parameters that aid in preventive maintenance to avoid key element failure. The ALC User Display (AUD) is a graphical user interface with hierarchical display structure, which provides high-level status information to the operation of the ALC, as well as detailed information for virtually all aspects of the ALC via drill-down displays. The operational status of an item, be it a function or assembly, is shown in the higher-level display. By pressing the item on the display screen, a new screen opens to show more detail of the function/assembly. Navigation tools and the map button allow immediate access to all screens.

Ahlstrom, Harlow↗

NASA NTRS2018

Evaluating the Calibration of Aqua MODIS Bands 33, 35, and 36 During Blackbody Warm-Up Cool-Down Events

Aqua MODIS is the second MODIS instrument of NASA's Earth Observation System and has operated for over sixteen years since its launch in 2002. MODIS has sixteen thermal emissive bands (TEBs) located on two separate cold focal plane assemblies (CFPA). The TEBs are calibrated every scan using observations of an onboard blackbody (BB) and a space view port. Low saturation temperatures (Tsat) of Aqua MODIS bands 33, 35, and 36 cause these bands to saturate when the BB temperature is higher than their Tsat values during a BB warm-up cool-down (WUCD) cycle, therefore impacting the ability to perform nominal calibration. In addition, starting from around 2006, the CFPA temperature showed gradual variation from its nominally-controlled operating temperature due to a loss of its radiative cooler margin and the magnitude of its fluctuation reaching a maximum in 2013. The MODIS Characterization Support Team currently uses a correction that is dependent on the CFPA temperature to provide a gain estimate for the saturated scans during the BB WUCD. This gain estimation has been implemented in the Aqua MODIS Collection 6 (C6) and C6.1 L1B products. This paper evaluates the quality of the calibrated radiance of Aqua MODIS bands 33, 35, and 36 using simultaneous nadir observations from the Atmospheric Infrared Sounder (AIRS), which is also onboard the Aqua satellite. Our analysis results show that the differences between AIRS and Aqua MODIS can be controlled well within the fluctuation range compared to the periods when the BB signals for these bands are not saturated.

Li, Yonghong↗