Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “MAGNETIC COMPRESSION”

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 1,549 records · Page 86
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Generation of Pc 1 waves by the ion temperature anisotropy associated with fast shocks caused by sudden impulses

The high correlation of Pc 1 events with magnetospheric compressions is known. A mechanism is proposed which leads to the generation of Pc 1 waves. The interaction of a dynamic pressure pulse with the earth's bow shock leads to the formation of a weak fast-mode shock propagating into the magnetoshealth. The shock wave can pass right through a tangential discontinuity (magnetopause) and into the magnetosphere, without disturbing either of the structures. In a quasiperpendicular geometry, the shock wave exhibits anisotropic heating. This anisotropy drives unstable ion-cyclotron waves which can contribute to the generation of the Pc 1 waves which are detected. The viability of the mechanism is demonstrated with simulations. This mechanism could explain the peak in the occurrence of observed Pc 1 waves in the postnoon sector where a field-aligned discontinuity in the solar wind would most often be parallel to the magnetopause surface due to the average Parker-spiral magnetic-field configuration.

Mandt, M. E.↗
DOE OSTI2015

Investigation of compression of puffing neon by deuterium current and plasma sheath in plasma focus discharge

This paper presents the results of the research of the influence of compressed neon, injected by the gas-puff nozzle in front of the anode axis by the deuterium current and plasma sheath on the evolution of the pinch, and neutron production at the current of 2 MA. The intense soft X-ray emission shows the presence of neon in the central region of the pinch. During the implosion and stopping of the plasma sheath, the deuterium plasma penetrates into the internal neon layer. The total neutron yield of 10{sup 10}–10{sup 11} has a similar level as in the pure deuterium shots. The neutron and hard X-ray pulses from fusion D-D reaction are as well emitted both in the phase of the stopping implosion and during the evolution of instabilities at the transformation of plasmoidal structures and constrictions composed in this configuration from both gases. The fast deuterons can be accelerated at the decay of magnetic field of the current filaments in these structures.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Strain-driven oxygen vacancy ordering in LaNiO 3 thin films revealed by integrated differential phase contrast imaging in scanning transmission electron microscopy

Rare-earth nickelates, such as LaNiO 3 (LNO), exhibit complex electronic properties, with ordered oxygen vacancies (OOV) influencing conductivity and magnetic behavior. We investigate the structural stability of strain-induced OOV phases in LNO thin films grown on SrTiO 3 substrates and the impact of Ruddlesden–Popper (RP) faults. Using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and integrated differential phase contrast (iDPC) STEM imaging, we conducted atomic-scale structural and compositional analyses of OOV. Geometric phase analysis (GPA) was employed to measure the strain in fault-free and RP fault regions, while density functional theory (DFT) calculations explored different OOV arrangements in the LNO phase. Simulated iDPC-STEM imaging of energy-stabilized structures was performed to correlate with experimental results. Here, our findings reveal superstructure modulation in the chemical composition and atomic-scale lattice structure in LNO, primarily due to the formation of the OOV in Ni–O layers of the LaNiO 2.5 phase. The out-of-plane compressive strain of about 2% stabilizes this phase, reducing the strain, diminishing OOV, and transforming them into LNO.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Channeling acceleration in crystals and nanostructures and studies of solid plasmas: new opportunities

In this study, plasma wakefield acceleration (PWFA) has shown illustrious progress and resulted in an impressive demonstration of tens of GeV particle acceleration in meter-long single structures. To reach even higher energies in the 1 TeV to 10 TeV range, a promising scheme is channeling acceleration in solid-density plasmas within crystals or nanostructures. The E336 experiment studies the beam-nanotarget interaction with the highly compressed electron bunches available at the FACET-II accelerator. These studies furthermore involve an in-depth research on dynamics of beam-plasma instabilities in ultra-dense plasma, its development and suppression in structured media like carbon nanotubes and crystals, and its potential use to transversely modulate the electron bunch.

43 PARTICLE ACCELERATORS↗
DOE OSTI2024

Effect of parallel flow on resonant layer responses in high beta plasmas

Abstract Resonant layers in a tokamak respond to non-axisymmetric magnetic perturbations by amplifying the mode amplitude and balancing the plasma rotation through magnetic reconnection and force balance, respectively. This resonant response can be characterized by local layer parameters and especially by a single quantity in the linear regime, the so-called inner-layer Δ. The computation of Δ under two-fluid drift-MHD formalism has been progressed by reducing the order of the system in the phase space, where the shielding current is approximated as being only carried by electrons, a posteriori . In this study, we relax the approximation and compute Δ accounted for by the parallel flow associated with the ion shielding current. The posteriori is numerically verified in great agreement with the original SLAYER developed in a previous paper (J.-K. Park 2022 Phys. Plasmas 29 072506). Extending the resonant layer response theory to high β plasmas, our research findings answer two important questions: how the parallel flow influences the resonant layer response and why the parallel flow effect appears in high β plasmas. The complicated plasma compression in high β regime allows the parallel flow response to give rise to the ion shielding current, which not only shifts the zero-crossing condition of the ExB flow but also enhances the field penetration threshold. Technically, the Riccati matrix transformation method is adapted to handle the numerical stiffness due to the increased order of the system. The high fidelity of this numerical method makes use of further extension of the model to higher-order systems to take other physical phenomena into account. This work is envisaged to predict the resonant layer response under high β fusion reactor conditions.

Lee, Yeongsun (ORCID:000000034474416X)↗
DOE OSTI2023

Phonon mixing in the charge density wave state of ScV6Sn6

Abstract Kagomé metals are widely recognized, versatile platforms for exploring topological properties, unconventional electronic correlations, magnetic frustration, and superconductivity. In the R V 6 Sn 6 family of materials ( R = Sc, Y, Lu), ScV 6 Sn 6 hosts an unusual charge density wave ground state as well as structural similarities with the A V 3 Sb 5 system ( A = K, Cs, Rb). In this work, we combine Raman scattering spectroscopy with first-principles lattice dynamics calculations to reveal phonon mixing processes in the charge density wave state of ScV 6 Sn 6 . In the low temperature phase, we find at least four new peaks in the vicinity of the V-containing totally symmetric mode near 240 cm −1 suggesting that the density wave acts to mix modes of P 6/ m m m and $$R\bar{3}m$$ R 3 ¯ m symmetry - a result that we quantify by projecting phonons of the high symmetry state onto those of the lower symmetry structure. We also test the stability of the short-range ordered density wave state under compression and propose that both physical and chemical pressure quench the effect. We discuss these findings in terms of symmetry and the structure-property trends that can be unraveled in this system.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS2017

Charger 1: A New Facility for Z-Pinch Research

Charger 1 is a multipurpose pulsed power laboratory located on Redstone Arsenal, with a focus on fusion propulsion relevant experiments involving testing z-pinch diodes, pulsed magnetic nozzle and other related physics experiments. UAH and its team of pulsed power researchers are investigating ways to increase and optimize fusion production from Charger 1. Currently the team has reached high-power testing. Due to the unique safety issues related to high power operations the UAH/MSFC team has slowed repair efforts to develop safety and operations protocols. The facility is expected to be operational by the time DZP 2017 convenes. Charger 1 began life as the Decade Module 2, an experimental prototype built to prove the Decade Quad pinch configuration. The system was donated to UAH by the Defense Threat Reduction Agency (DRTA) in 2012. For the past 5 years a UAH/MSFC/Boeing team has worked to refurbish, assemble and test the system. With completion of high power testing in summer 2017 Charger 1 will become operational for experimentation. Charger 1 utilizes a Marx Bank of 72 100-kV capacitors that are charged in parallel and discharged in series. The Marx output is compressed to a pulse width of approximately 200 ns via a pulse forming network of 32 coaxial stainless steel tubes using water as a dielectric. After pulse compression a set of SF6 switches are triggered, allowing the wave front to propagate through the output line to the load. Charger 1 is capable of storing 572-kJ of energy and time compressing discharge to less than 250 ns discharge time producing a discharge of about 1 TW of discharge with 1 MV and 1 MA peak voltage and current, respectively. This capability will be used to study energy yield scaling and physics from solid density target as applied to advanced propulsion research.

Taylor, Brian↗
DOE OSTI2015

Collision of plane thermonuclear detonation waves in a preliminarily compressed DT mixture

The paper deals with a one-dimensional problem on symmetric irradiation of a plane DT fuel layer with a thickness 2H and density ρ{sub 0} ⩽ 100ρ{sub s} (where ρ{sub s} is the density of the DT fuel in the solid state at atmospheric pressure and a temperature of 4 K) by two identical monoenergetic proton beams with a kinetic energy of 1 MeV, an intensity of 10{sup 19} W/cm{sup 2}, and a duration of 50 ps. The problem is solved in the framework of one-fluid two-temperature hydrodynamic model that takes into account the equation of state for hydrogen, electron and ion heat conductivities, kinetics of the DT reaction, plasma self-radiation, and plasma heating by α-particles. The irradiation of the fuel results in the appearance of two counterpropagating detonation waves to the fronts of which rarefaction waves are adjacent. The efficiency of the DT reaction after the collision (reflection from the plane of symmetry) of the detonation waves depends on the spatial homogeneity of thermodynamic functions between the fronts of the reflected detonation waves. At Hρ{sub 0} ≈ 1 g/cm{sup 2}, the gain factor is G ≈ 200, whereas at Hρ{sub 0} ≈ 5 g/cm{sup 2}, it is G > 2000. As applied to a cylindrical target that is ignited from ends and in which the cylinder with the fuel is surrounded by a heavy magnetized shell, the obtained values of the burn-up and gain factors are maximum possible. To estimate the ignition energy E{sub ig} of a cylindrical target by using solutions to the one-dimensional problem, a quasi-one-dimensional model is developed. The model assumes that the main mechanism of target ignition is fuel heating by α-particles. The trajectories of α-particles are limited by a cylindrical surface with a given radius, which is a parameter of the model and is identified with the fuel radius in the target and the radii of the irradiating proton beams. This model reproduces the well-known theoretical dependence E{sub ig} ∼ ρ{sub 0}{sup −2} and yields E{sub ig} = 160 kJ as a lower estimate of the ignition energy for ρ{sub 0} = 100ρ{sub s} ≈ 22 g/cm{sup 3}.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2015

Tracing the 4000 year history of organic thin films: From monolayers on liquids to multilayers on solids

The recorded history of organic monolayer and multilayer thin films spans approximately 4000 years. Fatty-acid-based monolayers were deposited on water by the ancients for applications ranging from fortune telling in King Hammurabi's time (∼1800 BC, Mesopotamia) to stilling choppy waters for sailors and divers as reported by the Roman philosopher Pliny the Elder in ∼78 AD, and then much later (1774) by the peripatetic American statesman and natural philosopher Benjamin Franklin, to Japanese “floating-ink” art (suminagashi) developed ∼1000 years ago. The modern science of organic monolayers began in the late-1800s/early-1900s with experiments by Lord Rayleigh and the important development by Agnes Pockels, followed two decades later by Irving Langmuir, of the tools and technology to measure the surface tension of liquids, the surface pressure of organic monolayers deposited on water, interfacial properties, molecular conformation of the organic layers, and phase transitions which occur upon compressing the monolayers. In 1935, Katherine Blodgett published a landmark paper showing that multilayers can be synthesized on solid substrates, with controlled thickness and composition, using an apparatus now known as the Langmuir-Blodgett (L-B) trough. A disadvantage of LB films for some applications is that they form weak physisorbed bonds to the substrate. In 1946, Bigelow, Pickett, and Zisman demonstrated, in another seminal paper, the growth of organic self-assembled monolayers (SAMs) via spontaneous adsorption from solution, rather than from the water/air interface, onto SiO{sub 2} and metal substrates. SAMs are close-packed two-dimensional organic crystals which exhibit strong covalent bonding to the substrate. The first multicomponent adsorbed monolayers and multilayer SAMs were produced in the early 1980s. Langmuir monolayers, L-B multilayers, and self-assembled mono- and multilayers have found an extraordinarily broad range of applications including controlled wetting, adhesion, electrochemistry, biocompatibility, molecular recognition, biosensing, cell biology, non-linear optics, molecular electronics, solar cells, read/write/erase memory, and magnetism.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Stochastic Ion Acceleration by the Ion-cyclotron Instability in a Growing Magnetic Field

Using 1D and 2D particle-in-cell simulations of a plasma with a growing magnetic field ${\boldsymbol{B}}$, we show herein that ions can be stochastically accelerated by the ion-cyclotron (IC) instability. As ${\boldsymbol{B}}$ grows, an ion pressure anisotropy ${p}_{\perp ,i}\gt {p}_{| | ,i}$ arises due to the adiabatic invariance of the ion magnetic moment (${p}_{| | ,i}$ and $p_{⊥,i}$ are the ion pressures parallel and perpendicular to ${\boldsymbol{B}}$). When initially $β_ i$ = 0.5 (${\beta }_{i}\equiv 8\pi {p}_{i}/| {\boldsymbol{B}}{| }^{2}$, where $p_i$ is the ion isotropic pressure), the pressure anisotropy is limited mainly by inelastic pitch-angle scattering provided by the IC instability, which in turn produces a nonthermal tail in the ion energy spectrum. After ${\boldsymbol{B}}$ is amplified by a factor of ~2.7, this tail can be approximated as a power law of index ~3.4 plus two nonthermal bumps and accounts for 2%–3% of the ions and ~18% of their kinetic energy. On the contrary, when initially $β_i$ = 2, the ion scattering is dominated by the mirror instability, and the acceleration is suppressed. This implies that efficient ion acceleration requires that initially, $β_{i} \lesssim$ 1. Although we focus on cases where ${\boldsymbol{B}}$ is amplified by plasma shear, we check that the acceleration occurs similarly if ${\boldsymbol{B}}$ grows due to plasma compression. Our results are valid in a subrelativistic regime where the ion thermal energy is ~10% of the ion rest-mass energy. This acceleration process can thus be relevant in the inner region of low-luminosity accretion flows around black holes.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

Interaction of Strain Refined Precipitates and Recrystallized Grains in Nb-Ti Microalloyed Steel during Continuous Casting, Hot-Core Heavy Reduction Rolling, and Reheating Process

Hot-core heavy reduction rolling (HHR{sup 2}) is an energy-saving process that directly rolls continuously cast slabs at the end of solidification that have a large temperature gradient. Here, we elucidated the interaction of strain refined precipitates and recrystallized grains in Nb-Ti microalloyed steel during continuous casting, hot-core heavy reduction rolling, and reheating process. Furthermore, theoretical models were established to calculate recrystallization driving force and pinning force at temperatures in the range of 850-1300 °C by a two-stage interrupted compression test using a Gleeble-3800 thermomechanical simulator. The study indicated that a random dispersion of strain refined precipitates with a size range of ~ 6-10 nm was obtained in the hot-core heavy reduction rolled slab, which was different from the coarse and uneven distribution of precipitates in a conventional slab. Upon reheating, the austenite grains in the hot-core heavy reduction rolled slab were significantly refined and evenly distributed along the thickness direction. This is attributed to the random dispersion of strain refined precipitates formed in the HHR{sup 2} process.

36 MATERIALS SCIENCE↗
NASA NTRS2006

Plasma Circulation in the Magnetosphere

We investigate the global structure and dynamics of plasma circulation produced by prototypical solar wind disturbances of the interplanetary magnetic field and dynamic pressure. We track the global circulation and energization of solar wind, polar wind, and auroral wind plasmas throughout the magnetosphere, until they precipitate or escape into the downstream solar wind. We use the full equations of motion of the plasma ions within fields produced by a global MHD simulation of the dynamic solar wind interaction. We use the dynamic hot plasma density and Poynting energy flux specified at the inner boundary of the MHD simulation as drivers of conjugate ion outflow fluxes using local empirical relations obtained from the FAST and Polar missions. Birkeland currents computed by the MHD code are used to derive a field-parallel potential drop from a Knight-like relation [as modified by Lyons and Evans, 1980]. This potential drop is applied to each ion as an initial bulk energy, added to a thermal heating driven by the locally incident Poynting flux. The solar wind pressure increase case (B(sub Y) = 5; B(sub z) = 0 nT) produces an immediate substorm owing to compression of pre-existing plasmas. The SB(sub z), interval (embedded in NB(sub z)) produces a substorm after about one hour of development. Both disturbances enhance the auroral wind flux and heavy ion pressure of the magnetosphere substantially, with complex dynamic structuring by auroral acceleration vortexes and dynamic reconnection. Comparisons are made with observations during disturbed periods including the Halloween 2003 super-storm and other periods.

Moore, T. E.↗
NASA NTRS2001

Bioengineered anterior cruciate ligament

The present invention provides a method for producing an anterior cruciate ligament ex vivo. The method comprises seeding pluripotent stem cells in a three dimensional matrix, anchoring the seeded matrix by attachment to two anchors, and culturing the cells within the matrix under conditions appropriate for cell growth and regeneration, while subjecting the matrix to one or more mechanical forces via movement of one or both of the attached anchors. Bone marrow stromal cells are preferably used as the pluripotent cells in the method. Suitable matrix materials are materials to which cells can adhere, such as a gel made from collagen type I. Suitable anchor materials are materials to which the matrix can attach, such as Goinopra coral and also demineralized bone. Optimally, the mechanical forces to which the matrix is subjected mimic mechanical stimuli experienced by an anterior cruciate ligament in vivo. This is accomplished by delivering the appropriate combination of tension, compression, torsion, and shear, to the matrix. The bioengineered ligament which is produced by this method is characterized by a cellular orientation and/or matrix crimp pattern in the direction of the applied mechanical forces, and also by the production of collagen type I, collagen type III, and fibronectin proteins along the axis of mechanical load produced by the mechanical forces. Optimally, the ligament produced has fiber bundles which are arranged into a helical organization. The method for producing an anterior cruciate ligament can be adapted to produce a wide range of tissue types ex vivo by adapting the anchor size and attachment sites to reflect the size of the specific type of tissue to be produced, and also adapting the specific combination of forces applied, to mimic the mechanical stimuli experienced in vivo by the specific type of tissue to be produced. The methods of the present invention can be further modified to incorporate other stimuli experienced in vivo by the particular developing tissue, some examples of the stimuli being chemical stimuli, and electro-magnetic stimuli. Some examples of tissue which can be produced include other ligaments in the body (hand, wrist, elbow, knee), tendon, cartilage, bone, muscle, and blood vessels.

Altman, Gregory↗
NASA NTRS2015

The Hopper: A Wearable Robotic Device Testbed for Micro-Gravity Bone-Loading Proof-of-Concept

Wearable robotic systems are showing increased potential for addressing crew countermeasures needs. Wearable robots offer a compactness, programmability, and eccentric loading capability not present in more conventional exercise equipment. Correspondingly, advancements in the man to machine interface has progressed, allowing for higher loads to be applied directly to the person in new and novel ways. Recently, the X1 exoskeleton, a lower extremity wearable robot originally designed for mobility assistance and rehabilitation, underwent human subject testing to assess its potential as a knee dynamometer. This was of interest to NASA physiologists because currently strength is not assessed in flight due to hardware limitations, and thus there is a poor understanding of the time course of in-flight changes to muscle strength. The study concluded that the X1 compared well with the Biodex, the "gold standard" in terrestrial dynamometry, with coefficients of variation less than 6.0%. In a following study, the X1 powered ankle was evaluated for its efficacy in exercising calf muscles. Current on-orbit countermeasures equipment does not adequately protect the calf from atrophy. The results of this study were also positive (targeted muscle activity demonstrated via comparing pre- and post-exercise magnetic resonance imaging T2 measurements), again showing the efficacy of wearable robotic devices for addressing the countermeasure needs of our astronauts. Based on these successes and lessons learned, the Grasshopper was co-developed between IHMC (Florida Institute for Human and Machine Cognition) and NASA. The Grasshopper, or the Hopper for short, is a wearable robotic device designed to address muscle and bone density loss for astronauts spending extended periods of time in micro-gravity. The Grasshopper connects to the user's torso like a hiking backpack, over the shoulders and around the waist. At the feet are footplates that strap to the user. There are two actuators, one at each "knee" joint, which are capable of high fidelity torque control. Because the Hopper uses motors instead of gravity to create the load on the user, the device is suited for use on space missions. Exercise in zero-gravity conditions is critical to maintain muscle strength and bone mass. In operation, the actuators try to fold up, or collapse, the device, putting a compressive load between the user's feet and torso. This force is similar to carrying a heavy backpack. The user then bends and extends his or her knees, replicating a weightlifting squat exercise. The applied load is precisely controlled by a computer, and can be programmed to simulate gravitation loads or any desired load prescription, such as free-weight squat exercise. It is even possible to perform eccentric exercises, or negatives, without the need for a spotter. Because the hip joints, as well as the spine and long leg bones, are in the applied load path, there is the potential to stimulate bone growth, countering the typical bone loss when astronauts return from extended duration space travel.

Beck, C. E.↗
DOE OSTI2015

OPTICAL HYDROGEN ABSORPTION CONSISTENT WITH A THIN BOW SHOCK LEADING THE HOT JUPITER HD 189733B

Bow shocks are ubiquitous astrophysical phenomena resulting from the supersonic passage of an object through a gas. Recently, pre-transit absorption in UV metal transitions of the hot Jupiter (HJ) exoplanets HD 189733b and WASP12-b have been interpreted as being caused by material compressed in a planetary bow shock. Here we present a robust detection of a time-resolved pre-transit, as well as in-transit absorption signature around the HJ exoplanet HD 189733b using high spectral resolution observations of several hydrogen Balmer lines. The line shape of the pre-transit feature and the shape of the timeseries absorption provide the strongest constraints on the morphology and physical characteristics of extended structures around an exoplanet. The in-transit measurements confirm the previous exospheric Hα detection, although the absorption depth measured here is ∼50% lower. The pre-transit absorption feature occurs 125 minutes before the predicted optical transit, a projected linear distance from the planet to the stellar disk of 7.2 R{sub p}. The absorption strength observed in the Balmer lines indicates an optically thick, but physically small, geometry. We model this signal as the early ingress of a planetary bow shock. If the bow shock is mediated by a planetary magnetosphere, the large standoff distance derived from the model suggests a large planetary magnetic field strength of B{sub eq} = 28 G. Better knowledge of exoplanet magnetic field strengths is crucial to understanding the role these fields play in planetary evolution and the potential development of life on planets in the habitable zone.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Enhanced magnetostriction through dilute Ce doping of Fe-Ga

Doping of magnetostrictive galfenol (Fe 82 Ga 18 , in at.%) with rare-earth elements significantly enhances magnetostriction, with the largest gains achieved in textured melt-spun ribbons. Here, it is demonstrated that even extremely dilute Ce, as little as 65 ppm, can double the magnetostrictive response of galfenol when coupled with an appropriate heat treatment. This improvement is correlated with a compression of the host lattice, both of which reach their maximum extent at the calculated solubility limit of Ce in in body-centered cubic (bcc) galfenol, ~ 50 ppm. Beyond this point, excess Ce segregates into CeGa 2 , which forms an interdendritic network throughout the sample at high Ce levels and cannot be resolutionized through heat treatments. These findings point to the importance of solubility limits (i.e., equilibrium thermodynamics) in determining appropriate doping levels or heat treatment couples to optimize magnetostrictive performance, confirming that overdoping is actively detrimental to both material properties and cost.

36 MATERIALS SCIENCE↗
NASA NTRS2012

Coronal Mass Ejection-driven Shocks and the Associated Sudden Commencements-sudden Impulses

Interplanetary (IP) shocks are mainly responsible for the sudden compression of the magnetosphere, causing storm sudden commencement (SC) and sudden impulses (SIs) which are detected by ground-based magnetometers. On the basis of the list of 222 IP shocks compiled by Gopalswamy et al., we have investigated the dependence of SC/SIs amplitudes on the speed of the coronal mass ejections (CMEs) that drive the shocks near the Sun as well as in the interplanetary medium. We find that about 91% of the IP shocks were associated with SC/SIs. The average speed of the SC/SI-associated CMEs is 1015 km/s, which is almost a factor of 2 higher than the general CME speed. When the shocks were grouped according to their ability to produce type II radio burst in the interplanetary medium, we find that the radio-loud (RL) shocks produce a much larger SC/SI amplitude (average approx. 32 nT) compared to the radio-quiet (RQ) shocks (average approx. 19 nT). Clearly, RL shocks are more effective in producing SC/SIs than the RQ shocks. We also divided the IP shocks according to the type of IP counterpart of interplanetary CMEs (ICMEs): magnetic clouds (MCs) and nonmagnetic clouds. We find that the MC-associated shock speeds are better correlated with SC/SI amplitudes than those associated with non-MC ejecta. The SC/SI amplitudes are also higher for MCs than ejecta. Our results show that RL and RQ type of shocks are important parameters in producing the SC/SI amplitude.

Coronal mass ejections↗
DOE OSTI2024

Unraveling sources of emission heterogeneity in Silicon Vacancy color centers with cryo-cathodoluminescence microscopy

Diamond color centers have proven to be versatile quantum emitters and exquisite sensors of stress, temperature, electric and magnetic fields, and biochemical processes. Among color centers, the silicon-vacancy (SiV - ) defect exhibits high brightness, minimal phonon coupling, narrow optical linewidths, and high degrees of photon indistinguishability. Yet the creation of reliable and scalable SiV - -based color centers has been hampered by heterogeneous emission, theorized to originate from surface imperfections, crystal lattice strain, defect symmetry, or other lattice impurities. Here, we advance high-resolution cryo-electron microscopy combined with cathodolumines cence spectroscopy and 4D scanning transmission electron microscopy (STEM) to elucidate the structural sources of heterogeneity in SiV - emission from nanodiamond with sub-nanometer-scale resolution. Our diamond nanoparticles are grown directly on TEM membranes from molecular-level seedings, representing the natural formation conditions of color centers in diamond. We show that individual subcrystallites within a single nanodiamond exhibit distinct zero-phonon line (ZPL) energies and differences in brightness that can vary by 0.1 meV in energy and over 70% in brightness. These changes are correlated with the atomic-scale lattice structure. We find that ZPL blue shifts result from tensile strain, while ZPL red shifts are due to compressive strain. We also find that distinct crystallites host distinct densities of SiV - emitters and that grain boundaries impact SiV - emission significantly. Finally, we interrogate nanodiamonds as small as 40 nm in diameter and show that these diamonds exhibit no spatial change to their ZPL energy. Our work provides a foundation for atomic-scale structure-emission correlation, e.g., of single atomic defects in a range of quantum and two-dimensional materials.

36 MATERIALS SCIENCE↗