Search NASA⌕ Search

SEARCH · Search NASA

Results for “HALL EFFECT”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS2020

Uncertainty in Electric Propulsion Erosion Measurements

Uncertainty in erosion rates as measured by different methods is discussed and quantified. The work focuses on case studies from components on the Hall Effect Rocket with Magnetic Shielding (HERMeS) Hall thruster, but the methods can be extended for many electric propulsion applications. The primary method used for evaluating erosion is non-contact profilometry of masked and exposed components. Accurate quantification of the erosion rates of components is critical to determining lifetime and is therefore critical to mission planning purposes.

Jonathan A Mackey↗
DOE OSTI2025

Interplay of superconducting, metallic, and crystalline states of composite fermions at 𝜈 = $\frac{1}{6}$ in wide quantum wells

Evidence for developing fractional quantum Hall effect (FQHE) at filling fraction 𝜈 = 1/6 and 1/8 was recently reported in wide GaAs quantum wells [Wang et al., Phys. Rev. Lett. 134, 046502 (2025)]. In this article, we theoretically investigate the nature of the state at 𝜈 = 1/6 as a function of the quantum well width and the density by considering composite-fermion (CF) crystals, CF Fermi sea, and various kinds of paired CF states. The 𝑓-wave paired state has the lowest energy among the paired CF states. However, for parameters of interest, the energies of the CF crystal, the CF Fermi liquid, and the 𝑓-wave paired CF state are too close to distinguish. We, therefore, predict that 𝑖𝑓 the FQHE at 𝜈 = 1/6 is experimentally confirmed, this state would be an 𝑓-wave paired state of CFs, which can be verified by measurement of its thermal Hall conductance. Exact diagonalization studies on clean systems with up to eight electrons show that the ground states at 𝜈 = 𝑛/(6⁢𝑛 ± 1) are incompressible for all widths and densities we have considered, and are well described by the corresponding Laughlin and Jain states. We propose a phase diagram for large quantum well widths and densities in which at zero disorder, incompressible FQHE states are stabilized at 𝜈 = 𝑛/(6⁢𝑛 ± 1) and 𝜈 = 1/6, but in between these fillings the CF crystal is stabilized. We also present a qualitative discussion on the effects of disorder and propose a schematic phase diagram based on it. With disorder, which creates a spatial variation in the filling factor, two regimes are identified: (i) for small disorder, when the incompressible states percolate at the special fillings, FQHE with quantized Hall plateaus and vanishing longitudinal resistance should occur; and (ii) for larger disorder, when the CF crystal percolates, the longitudinal resistance rises with decreasing temperature but the domains of FQHE liquid produce minima at the special filling factors. Here, experiments are consistent with the latter scenario. We also mention a possible connection of the phase diagram presented here to a puzzling behavior observed for the fractional quantum anomalous Hall effect in pentalayer graphene.

Composite fermions↗
DOE OSTI2026

Anisotropy, frustration, and saddle point in the twisted kagome compound ErPdPb

The kagome lattice, with its inherent geometric frustration, provides a rich platform for exploring intriguing magnetic phenomena and topological electronic structures. In reduced-symmetry structures, such as twisted kagome systems involving rare earth elements, additional anisotropy can arise, enabling intriguing properties including spin-ice states, magnetocaloric effects, noncollinear magnetic ordering, and the anomalous Hall effect. Here, we report the synthesis of single crystals of ErPdPb, which features a twisted kagome lattice net of Er atoms within the hexagonal ZrNiAl-type structure, and we investigate its magnetic, electronic, and thermal properties. The material exhibits a highly anisotropic, correlated magnetic state below 2.7 K, as evidenced by magnetic, transport, and heat capacity measurements. Density functional theory (DFT) calculations indicate strong easy-axis anisotropy, consistent with experiment and crystal-field expectations, as well as quasi-one-dimensional bands and a spin-split saddle point at the zone center. Here, the coexistence of competing magnetic interactions along different crystallographic directions suggests an inherent degree of frustration. ErPdPb thus provides a promising platform for exploring the interplay of frustration, anisotropy, and electronic structure in a twisted kagome lattice.

Antiferromagnets↗
NASA NTRS2009

Integrity of the Plasma Magnetic Nozzle

This report examines the physics governing certain aspects of plasma propellant flow through a magnetic nozzle, specifically the integrity of the interface between the plasma and the nozzle s magnetic field. The injection of 100s of eV plasma into a magnetic flux nozzle that converts thermal energy into directed thrust is fundamental to enabling 10 000s of seconds specific impulse and 10s of kW/kg specific power piloted interplanetary propulsion. An expression for the initial thickness of the interface is derived and found to be approx.10(exp -2) m. An algorithm is reviewed and applied to compare classical resistivity to gradient-driven microturbulent (anomalous) resistivity, in terms of the spatial rate and time integral of resistive interface broadening, which can then be related to the geometry of the nozzle. An algorithm characterizing plasma temperature, density, and velocity dependencies is derived and found to be comparable to classical resistivity at local plasma temperatures of approx. 200 eV. Macroscopic flute-mode instabilities in regions of "adverse magnetic curvature" are discussed; a growth rate formula is derived and found to be one to two e-foldings of the most unstable Rayleigh-Taylor (RT) mode. After establishing the necessity of incorporating the Hall effect into Ohm s law (allowing full Hall current to flow and concomitant plasma rotation), a critical nozzle length expression is derived in which the interface thickness is limited to about 1 ion gyroradius.

Gerwin, Richard A.↗
DOE OSTI2024

Path integral approach to quantum anomalies in interacting models

The prediction and subsequent discovery of topological semimetal phases of matter in solid state systems has instigated a surge of activity investigating the exotic properties of these unusual materials. Among these are transport signatures which can be attributed to the chiral anomaly; the breaking of classical chiral symmetry in a quantum theory. This remarkable quantum phenomenon, first discovered in the context of particle physics has now found new life in condensed-matter physics, connecting topological quantum matter and band theory with effective field theoretic models. In this paper we investigate the interplay between interactions and the chiral anomaly in field theories inspired by semimetals using Fujikawa's path integral method. Starting from models in one spatial dimension we discuss how the presence of interactions can affect the consequences of the chiral anomaly leading to renormalization of excitations and their transport properties. This is then generalized to the three-dimensional case where we show that the anomalous response of the system, namely, the chiral magnetic and quantum Hall effects, are modified by the presence of interactions. These properties are investigated further through the identification of anomalous modes which exist within interacting Weyl semimetals. These massive excitations are nonperturbative in nature and are a direct consequence of the chiral anomaly. The effects of interactions on mixed axial-gravitational anomalies are then investigated and the conditions required for interaction effects to be observed are discussed.

Anomalies↗
DOE OSTI2024

Structural and Electronic Properties of Indium-Doped n-type Cd-Se-Te Crystals

Here, we present a comprehensive investigation into the potential of n-type indium-doped cadmium selenide telluride (CST:In) as a high-performance candidate for solar cell applications, without the need for resource-intensive post-growth treatments that are required for CdTe:In. We compared undoped CST and CST:In crystals under different growth conditions, analyzing their structural and electronic properties using x-ray diffraction (XRD), electron probe microanalysis (EPMA), current-voltage (IV) and Hall effect measurements, time-resolved photoluminescence (TRPL), optical transmission, and photoluminescence (PL) mapping. The results reveal that as-grown CST:In crystals achieve nearly 100% carrier activation, yielding an electron concentration of 9.5x1018 cm -3 , mobility of 653 cm 2 /V.s and a 5 ns lifetime which approaches the radiative limit. Furthermore, comparison of PL maps from crystal growths having different cooling profiles suggests a strong effect of cooling rate on selenium segregation and cubic/hexagonal/polytype phase distribution. Slower cooling leads to a more homogeneous cubic structure with lower Se segregation, while a faster cooling rate results in increased Se segregation, and twin boundaries and stacking faults with polytypic and hexagonal character.

14 SOLAR ENERGY↗
DOE OSTI2024

Hole‐Carrier‐Dominant Transport in 2D Single‐Crystal Copper

Abstract In 2D noble metals like copper, the carrier scattering at grain boundaries has obscured the intrinsic nature of electronic transport. However, it is demonstrated that the intrinsic nature of transport by hole carriers in 2D copper can be revealed by growing thin films without grain boundaries. As even a slight deviation from the twin boundary is perceived as grain boundaries by electrons, it is only through the thorough elimination of grain boundaries that the hidden hole‐like attribute of 2D single‐crystal copper can be unmasked. Two types of Fermi surfaces, a large hexagonal Fermi surface centered at the zone center and the triangular Fermi surface around the zone corner, tightly matching to the calculated Fermi surface topology, confirmed by angle‐resolved photoemission spectroscopy (ARPES) measurements and vivid nonlinear Hall effects of the 2D single‐crystal copper account for the presence of hole carriers experimentally. This breakthrough suggests the potential to manipulate the majority carrier polarity in metals by means of grain boundary engineering in a 2D geometry.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Plumbene: a comprehensive review of theoretical and experimental advances

Plumbene, a two-dimensional (2D) material consisting of a single layer of lead (Pb) atoms in a honeycomb lattice, stands as a pioneering addition to the elemental 2D material family. Here, this comprehensive review encapsulates the theoretical predictions and experimental advancements that underscore its potential. With properties shaped by significant spin-orbit coupling and structural buckling, plumbene offers a playground for phenomena like the quantum spin Hall effect, superconductivity, and topological phase transitions. Despite promising theoretical insights, experimental realization has encountered challenges, primarily due to high reactivity of Pb and the need for precise fabrication conditions. This paper critically examines the electronic, thermal, mechanical, and topological attributes of plumbene, alongside synthesis methods, functionalization techniques, and substrate effects. It further proposes directions for addressing synthesis challenges and integrating plumbene into advanced technologies, particularly in electronic, spintronic, and quantum computing applications. This review aims to bridge the gap between theoretical potential and experimental progress, fostering a deeper understanding of this intriguing material.

2D materials↗
NASA NTRS1995

(abstract) An Assessment of Electric Propulsion Research, Development, and Application in the United States

This paper will discuss the development of Electric Propulsion technology in the U.S. from the 1960's to the present. It will summarize the various activities related to arcjets, resistojets, pulsed plasma thrustors, magneto-plasma-dynamic thrustors, ion engines, and more recently the evaluation of Hall effect thrustors of the SPT or Anode Layer type developed in Russia. Also, demonstration test flight and actual mission applications will be summarized. Finally, the future application of electric propulsion to near-term commercial communications satellites and planetary missions will be projected. This history is rich in diversity, and has involved a succession of types of thrustors, propellants, and electric power sources. With the recent use of arcjets on commercial communication satellites and the flight tests of ion engines for this application, it appears that electric propulsion is finally on the verge of wide spread application.

ion engines electric propulsion arcjets resistojet↗
NASA NTRS2017

Reconfiguration of NASA GRC's Vacuum Facility 6 for Testing of Advanced Electric Propulsion System (AEPS) Hardware

The NASA Hall Effect Rocket with Magnetic Shielding (HERMeS) 12.5 kilowatt Hall thruster has been the subject of extensive technology maturation in preparation for development into a flight propulsion system. The HERMeS thruster is being developed and tested at NASA GRC and NASA JPL through support of the Space Technology Mission Directorate and is intended to be used as the electric propulsion system on the Power and Propulsion Element of the recently announced Deep Space Gateway. The Advanced Electric Propulsion System (AEPS) contract was awarded to Aerojet Rocketdyne to develop the HERMeS system into a flight system for use by NASA. To address the hardware test needs of the AEPS project, NASA GRC launched an effort to reconfigure Vacuum Facility 6 for high-power electric propulsion testing including upgrades and reconfigurations necessary to conduct performance, plasma plume, and system level integration testing. Results of the verification and validation testing with HERMeS Technology Demonstration Unit (TDU) 1 and TDU-3 Hall thrusters are also included.

ion engines↗
NASA NTRS2016

Reconfiguration of NASA GRC's Vacuum Facility 6 for Testing of Advanced Electric Propulsion System (AEPS) Hardware

The NASA Hall Effect Rocket with Magnetic Shielding (HERMeS) 12.5 kilowatt Hall thruster has been the subject of extensive technology maturation in preparation for development into a flight propulsion system. The HERMeS thruster is being developed and tested at NASA GRC and NASA JPL through support of the Space Technology Mission Directorate and is intended to be used as the electric propulsion system on the Power and Propulsion Element of the recently announced Deep Space Gateway. The Advanced Electric Propulsion System (AEPS) contract was awarded to Aerojet Rocketdyne to develop the HERMeS system into a flight system for use by NASA. To address the hardware test needs of the AEPS project, NASA GRC launched an effort to reconfigure Vacuum Facility 6 for high-power electric propulsion testing including upgrades and reconfigurations necessary to conduct performance, plasma plume, and system level integration testing. Results of the verification and validation testing with HERMeS Technology Demonstration Unit (TDU) 1 and TDU-3 Hall thrusters are also included.

life (durability)↗
NASA NTRS2018

Reconfiguration of NASA GRC's Vacuum Facility 6 for Testing of Advanced Electric Propulsion System (AEPS) Hardware

The NASA Hall Effect Rocket with Magnetic Shielding (HERMeS) 12.5 kW Hall thruster has been the subject of extensive technology maturation in preparation for development into a flight propulsion system. The HERMeS thruster is being developed and tested at NASA GRC and NASA JPL through support of the Space Technology Mission Directorate (STMD) and is intended to be used as the electric propulsion system on the Power and Propulsion Element (PPE) of the recently announced Deep Space Gateway (DSG). The Advanced Electric Propulsion System (AEPS) contract was awarded to Aerojet-Rocketdyne to develop the HERMeS system into a flight system for use by NASA. To address the hardware test needs of the AEPS project, NASA GRC launched an effort to reconfigure Vacuum Facility 6 (VF-6) for high-power electric propulsion testing including upgrades and reconfigurations necessary to conduct performance, plasma plume, and system level integration testing. Results of the verification and validation testing with HERMeS Technology Demonstration Unit (TDU)-1 and TDU-3 Hall thrusters are also included.

Peterson, Peter Y.↗
NASA NTRS2018

Long Duration Wear Test of the NASA HERMeS Hall Thruster

The NASA Hall Effect Rocket with Magnetic Shielding (HERMeS) 12.5-kW Hall thruster is the subject of extensive technology maturation by NASA GRC and JPL in preparation for development into a flight propulsion system. As part of this on-going effort, a series of three wear tests have been conducted to identify erosion phenomena and the accompanying failure modes as well as to validate service-life models for magnetically-shielded thrusters. This paper presents an overview and summary of the results obtained over the first 1715 hours of the third wear test, which has the overall goal of serving as a pathfinder to identify and correct design or facility issues prior to the flight qualification campaign. Overall, negligible changes in performance and stability are observed as a function of operating time as well as relative to previous wear tests. Erosion of the inner and outer front pole covers is shown to vary by 76-300 percent as a function of discharge voltage and by up to 40 percent as a function of magnetic field strength. Shifting the cathode position upstream relative to the pole covers is shown to reduce keeper erosion rates by 84 percent, which supports this approach for mitigating the elevated keeper wear observed during previous wear tests.

Frieman, Jason D.↗