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DOE OSTI2019

$D$ meson Semileptonic Decay Form Factors at $q^2 = 0$

We discuss preliminary results for the vector form factors $f_+^{\{\pi,K\}}$ at zero-momentum transfer for the decays $D\to\pi\ell\nu$ and $D\to K \ell\nu$ using MILC's $N_f = 2+1+1$ HISQ ensembles at four lattice spacings, $a \approx 0.042, 0.06, 0.09$, and 0.12 fm, and various HISQ quark masses down to the (degenerate) physical light quark mass. We use the kinematic constraint $f_+(q^2)= f_0(q^2)$ at $q^2 = 0$ to determine the vector form factor from our study of the scalar current, which yields $f_0(0)$. Results are extrapolated to the continuum physical point in the framework of hard pion/kaon SU(3) heavy-meson-staggered $\chi$PT and Symanzik effective theory. Our calculation improves upon the precision achieved in existing lattice-QCD calculations of the vector form factors at $q^2=0$. We show the values of the CKM matrix elements $|V_{cs}|$ and $|V_{cd}|$ that we would obtain using our preliminary results for the form factors together with recent experimental results, and discuss the implications of these values for the second row CKM unitarity.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

NASA NTRS2007

Plasma Measurements in an Integrated-System FARAD Thruster

Pulsed inductive plasma accelerators are spacecraft propulsion devices in which energy is stored in a capacitor and then discharged through an inductive coil. The device is electrodeless, inducing a current sheet in a plasma located near the face of the coil. The propellant is accelerated and expelled at a high exhaust velocity (order of 10 km/s) through the interaction of the plasma current and the induced magnetic field. The Faraday Accelerator with RF-Assisted Discharge (FARAD) thruster[1,2] is a type of pulsed inductive plasma accelerator in which the plasma is preionized by a mechanism separate from that used to form the current sheet and accelerate the gas. Employing a separate preionization mechanism allows for the formation of an inductive current sheet at much lower discharge energies and voltages than those used in previous pulsed inductive accelerators like the Pulsed Inductive Thruster (PIT). A benchtop FARAD thruster was designed following guidelines and similarity performance parameters presented in Refs. [3,4]. This design is described in detail in Ref. [5]. In this paper, we present the temporally and spatially resolved measurements of the preionized plasma and inductively-accelerated current sheet in the FARAD thruster operating with a Vector Inversion Generator (VIG) to preionize the gas and a Bernardes and Merryman circuit topology to provide inductive acceleration. The acceleration stage operates on the order of 100 J/pulse. Fast-framing photography will be used to produce a time-resolved, global view of the evolving current sheet. Local diagnostics used include a fast ionization gauge capable of mapping the gas distribution prior to plasma initiation; direct measurement of the induced magnetic field using B-dot probes, induced azimuthal current measurement using a mini-Rogowski coil, and direct probing of the number density and electron temperature using triple probes.

Polzin, K. A.↗

DOE OSTI2017

On the He–McKellar–Wilkens phase of an electric dipole

The He–McKellar–Wilkens (HMW) phase of an electric dipole moving in a static magnetic field is derived by explicitly considering the interaction between the currents associated with the moving dipole and the magnetic vector potential. Conditions for the observation of the HMW phase in different field configurations are investigated. A practical setup is proposed that provides essentially a radial magnetic field with inverse radial dependence for the observation of the HMW phase with magnetic field alone. Possible magnetic field control of exciton current in an open ring setup is discussed. - Highlights: • Conditions for the observation of the HMW phase in different field configurations are investigated. • A practical setup is proposed that for the observation of the HMW phase with magnetic field alone. • Possible magnetic field control of exciton current in an open ring setup is discussed.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2020

Giant momentum-dependent spin splitting in centrosymmetric low-$\textit{Z}$ antiferromagnets

The energy vs crystal momentum $\textit{E(k)}$ diagram for a solid (band structure) constitutes the road map for navigating its optical, magnetic, and transport properties. By selecting crystals with specific atom types, composition, and symmetries, one could design a target band structure and thus desired properties. A particularly attractive outcome would be to design energy bands that are split into spin components with a momentum-dependent splitting, as envisioned by Pekar and Rashba, enabling spintronic application. The current paper provides “design principles” for wave-vector dependent spin splitting (SS) of energy bands that parallel the traditional Dresselhaus and Rashba spin-orbit coupling (SOC)–induced splitting, but originates from a fundamentally different source—antiferromagnetism. Here, we identify a few generic antiferromagnetic (AFM) prototypes with distinct SS patterns using magnetic symmetry design principles. These tools allow also the identification of specific AFM compounds with SS belonging to different prototypes. A specific compound—centrosymmetric tetragonal MnF 2 —is used via density functional band-structure calculations to quantitatively illustrate one type of AFM SS. Unlike the traditional SOC-induced effects restricted to noncentrosymmetric crystals, we show that antiferromagnetic-induced spin splitting broadens the playing field to include even centrosymmetric compounds, and gives SS comparable in magnitude to the best known (“giant’” SOC effects, even without traditional SOC, and consequently does not rely on the often-unstable high atomic number elements required for high SOC. We envision that use of the current design principles to identify an optimal antiferromagnet with spin-split energy bands would be beneficial for efficient spin-charge conversion and spin-orbit torque applications without the burden of requiring compounds containing heavy elements.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2014

Computation of stationary 3D halo currents in fusion devices with accuracy control

This paper addresses the calculation of the resistive distribution of halo currents in three-dimensional structures of large magnetic confinement fusion machines. A Neumann electrokinetic problem is solved on a geometry so complicated that complementarity is used to monitor the discretization error. An irrotational electric field is obtained by a geometric formulation based on the electric scalar potential, whereas three geometric formulations are compared to obtain a solenoidal current density: a formulation based on the electric vector potential and two geometric formulations inspired from mixed and mixed-hybrid Finite Elements. The electric vector potential formulation is usually considered impractical since an enormous computing power is wasted by the topological pre-processing it requires. To solve this challenging problem, we present novel algorithms based on lazy cohomology generators that enable to save orders of magnitude computational time with respect to all other state-of-the-art solutions proposed in literature. Believing that our results are useful in other fields of scientific computing, the proposed algorithm is presented as a detailed pseudocode in such a way that it can be easily implemented.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2023

Genomic Characterization and Wetland Occurrence of a Novel Campylobacter Isolate from Canada Geese

Populations of resident, non-migratory Canada geese are rapidly increasing. Canada geese are known to transmit viral and bacterial diseases, posing a possible threat to human health. The most prevalent pathogens vectored by geese are Campylobacter species, yet the current understanding of the identity and virulence of these pathogens is limited. In our previous study, we observed a high prevalence of Campylobacter spp. in the Banklick Creek wetland—a constructed treatment wetland (CTW) located in northern KY (USA) used to understand sources of fecal contamination originating from humans and waterfowl frequenting the area. To identify the types of Campylobacter spp. found contaminating the CTW, we performed genetic analyses of Campylobacter 16s ribosomal RNA amplified from CTW water samples and collected fecal material from birds frequenting those areas. Our results showed a high occurrence of a Campylobacter canadensis-like clade from the sampling sites. Whole-genome sequence analyses of an isolate from Canada goose fecal material, called MG1, were used to confirm the identity of the CTW isolates. Further, we examined the phylogenomic position, virulence gene content, and antimicrobial resistance gene profile of MG1. Lastly, we developed an MG1-specific real-time PCR assay and confirmed the presence of MG1 in Canada goose fecal samples surrounding the CTW. Our findings reveal that the Canada goose-vectored Campylobacter sp. MG1 is a novel isolate compared to C. canadensis that possesses possible zoonotic potential, which may be of human health concern.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2024

Charm physics with overlap fermions on 2+1-flavor domain wall fermion configurations*

Decay constants of pseudoscalar mesons D, D s , η c , and vector mesons D*, D$^{*}_{s}$, J/ψ are determined from the N f = 2 + 1 lattice QCD at a lattice spacing a ~ 0.08 fm. For vector mesons, the decay constants defined by tensor currents are given in the $\overline{MS}$ scheme at 2 GeV. The calculation is performed on domain wall fermion configurations generated by the RBC-UKQCD collaborations and the overlap fermion action is used for the valence quarks. Comparing the current results with our previous results at a coarser lattice spacing a ~ 0.11 fm provides a better understanding of the discretization error. We obtain $f$$^{T}_{D^*_s}$($\overline{MS}$, 2 GeV)/f D$^{*}_{s}$ = 0.909(18) with a better precision than our previous result. Combining our f D$^{*}_{s}$ = 277(11) MeV with the total width of D$^{*}_{s}$ determined in a recent study gives a branching fraction 4.26(52) x 10 –5 for D$^{*}_{s}$ leptonic decay.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

NASA NTRS1993

Field-aligned currents in the Jovian magnetosphere during the Ulysses flyby

The data recorded by the dual vector helium/fluxgate magnetometer flown onboard the Ulysses spacecraft during the flyby of Jupiter in February 1992 are analyzed with the aim of identifying the presence of field-aligned current signatures. Field-aligned current flow is expected wherever stress is being transmitted electromagnetically along the magnetic field direction. Sources of such currents at Jupiter are departures within the magnetosphere from corotation, momentum transfer from the solar wind, or centrifugally driven magnetospheric outflow. It is pointed out that the azimuthal field component provides a simple first-order means of monitoring the presence of currents, the currents occurring in regions where the azimuthal component changes significantly. The data from both inbound and outbound passes show evidence of 'leading' and 'lagging' azimuthal field signatures where the field bends out of the meridian, and which are signatures symptomatic of current systems associated with departures from corotation. On the outbound pass, the most intense signatures are found where the field switches from a configuration symptomatic of the field lagging corotation to a configuration representing the field leading. The latter configuration also corresponds to a tail-like displacement of the field and, indeed, the magnetometer data alone cannot distinguish the source of the current system, which could be due to solar wind magnetosphere coupling or which may arise from internal stress imbalance.

Dougherty, M. K.↗

DOE OSTI2015

Precision vector control of a superconducting RF cavity driven by an injection locked magnetron

The technique presented in this paper enables the regulation of both radio frequency amplitude and phase in narrow band devices such as a Superconducting RF (SRF) cavity driven by constant power output devices i.e. magnetrons [1]. The ability to use low cost high efficiency magnetrons for accelerator RF power systems, with tight vector regulation, presents a substantial cost savings in both construction and operating costs - compared to current RF power system technology. An operating CW system at 2.45 GHz has been experimentally developed. Vector control of an injection locked magnetron has been extensively tested and characterized with a SRF cavity as the load. Amplitude dynamic range of 30 dB, amplitude stability of 0.3% r.m.s, and phase stability of 0.26 degrees r.m.s. has been demonstrated.

43 PARTICLE ACCELERATORS↗

DOE OSTI2013

RAVEN: a GUI and an Artificial Intelligence Engine in a Dynamic PRA Framework

Increases in computational power and pressure for more accurate simulations and estimations of accident scenario consequences are driving the need for Dynamic Probabilistic Risk Assessment (PRA) [1] of very complex models. While more sophisticated algorithms and computational power address the back end of this challenge, the front end is still handled by engineers that need to extract meaningful information from the large amount of data and build these complex models. Compounding this problem is the difficulty in knowledge transfer and retention, and the increasing speed of software development. The above-described issues would have negatively impacted deployment of the new high fidelity plant simulator RELAP-7 (Reactor Excursion and Leak Analysis Program) at Idaho National Laboratory. Therefore, RAVEN that was initially focused to be the plant controller for RELAP-7 will help mitigate future RELAP-7 software engineering risks. In order to accomplish this task, Reactor Analysis and Virtual Control Environment (RAVEN) has been designed to provide an easy to use Graphical User Interface (GUI) for building plant models and to leverage artificial intelligence algorithms in order to reduce computational time, improve results, and help the user to identify the behavioral pattern of the Nuclear Power Plants (NPPs). In this paper we will present the GUI implementation and its current capability status. We will also introduce the support vector machine algorithms and show our evaluation of their potentiality in increasing the accuracy and reducing the computational costs of PRA analysis. In this evaluation we will refer to preliminary studies performed under the Risk Informed Safety Margins Characterization (RISMC) project of the Light Water Reactors Sustainability (LWRS) campaign [3]. RISMC simulation needs and algorithm testing are currently used as a guidance to prioritize RAVEN developments relevant to PRA.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2015

Limit on Tensor Currents from Li 8 β Decay

In the standard model, the weak interaction is formulated with a purely vector-axial-vector ($V\text{-}A$) structure. Without restriction on the chirality of the neutrino, the most general limits on tensor currents from nuclear ${\beta}$ decay are dominated by a single measurement of the ${\beta}\text{-}\overline{{\nu}}$ correlation in $^{6}\mathrm{He}$ ${\beta}$ decay dating back over a half century. In the present paper, the ${\beta}\text{-}\overline{{\nu}}\text{-}{\alpha}$ correlation in the ${\beta}$ decay of $^{8}\mathrm{Li}$ and subsequent ${\alpha}$-particle breakup of the ${^{8}\mathrm{Be}}^{*}$ daughter was measured. The results are consistent with a purely $V\text{-}A$ interaction and in the case of couplings to right-handed neutrinos (${C}_{T}={-}{C}_{T}^{{'}}$) limits the tensor fraction to $|{C}_{T}/{C}_{A}{|}^{2}<0.011$ (95.5% C.L.). Finally, the measurement confirms the $^{6}\mathrm{He}$ result using a different nuclear system and employing modern ion-trapping techniques subject to different systematic uncertainties.

74 ATOMIC AND MOLECULAR PHYSICS↗

DOE OSTI2025

Constraining non-standard neutrino interactions with neutral current events at long-baseline oscillation experiments

We explore, for the first time, neutral-curren t events at long-baseline experiments to constrain vector and axial-vector neutrino non-standard interactions (NSI) with quarks. We leverage the flavor dependence of NSIs to perform an oscillation analysis in the neutral- current channel. We first introduce a framework to parametrize the effect of NSI on the cross section. Then, as an example, we analyze NOvA neutral-current data which provides significantly improved constraints on the axial-vector NSI parameters ${\varepsilon}_{\mu \mu}^A$, ${\varepsilon}_{\tau \tau}^A$ and ${\varepsilon}_{e\mu}^A$. This is highly complementary to constraints from SNO data, which, differently from long-baseline neutral current data, is not sensitive to isospin conserving NSIs ${\varepsilon}_u^A$ = ${\varepsilon}_d^A$. Additionally, we disfavor large values of the diagonal vectorial NSI ${\varepsilon}_{\mu \mu}^{VV}$ and ${\varepsilon}_{\tau \tau}^V$ which originate from the LMA-Dark solution. We also highlight the complementarity between NSI searches at oscillation experiments using charged current and neutral current channels.

neutrino interactions↗

DOE OSTI2026

Simple algorithm for polarized parton evolution

We present an algorithm to include the correlation between the production and decay planes of gluons in a parton-shower simulation. The technique is based on identifying the charge currents responsible for the creation and annihilation of the vector field. It is applicable in both the hard-collinear and the soft wide-angle region. As a function of the number of particles, the algorithm scales linear in computing time and memory. We demonstrate agreement with fixed-order perturbative calculations in the relevant kinematical limits, and present a new observable that can be used to probe correlations beyond current-current interactions.

Höche, Stefan [Fermi National Accelerator Laborato↗

NASA NTRS1985

Calculation of secondary-electron escape currents from inclined-spacecraft surfaces in a magnetic field

In low Earth orbit, the geomagnetic field B(vector) is strong enough that secondary electrons emitted from spacecraft surfaces have an average gyroradius much smaller than typical dimensions of large spacecraft. This implies that escape of secondaries will be strongly inhibited on surfaces which are nearly parallel to B(vector), even if a repelling electric field exists outside them. This effect is likely to make an important contribution to the current balance and hence the equilibrium potential of such surfaces, making high voltage charging of them more likely. Numerically calculated escaping secondary electron fluxes are presented for these conditions. For use in numerical spacecraft charging simulations, an analytic curve fit to these results is given which is accurate to within 3% of the emitted current.

Laframboise, J. G.↗

NASA NTRS1994

Filamentary current structures in the postnoon sector: Observations from UARS

During an intense geomagentic storm (Kp 7+) that began at approximately 1830 UT on October 1, 1991, the Upper Atmosphere Research Satellite (UARS) satellite encountered the dayside postnoon auroral oval. On two consecutive crossings of the northern hemisphere between 2040 and 2240 UT, the vector magnetometer detected region 1 and 2 Birkeland and ionospheric currents in the postnoon sector. Low-energy electron events were observed near 1400 MLT within a narrow portion of the region 1 current system. Simultaneous magnetic field measurements revealed the presence of intense (approximately 20 microA/sq m) bipolar filament current structures embedded in the auroral oval. The upward-directed currents were associated with the more concentrated region of precipitating electrons. Ions associated with the more intense flux of low-energy electrons exhibited a dispersion signature typical of an ion velocity filter. The dispersion, aligned along the orbit, exhibited higher-energy ions at lower latitudes and earlier local times. The colocation of filament currents and ion dispersion signatures at such late postnoon local times is not consistent with typical E x B 'cusp' dispersions. These features more likely result from dayside boundary wave phenomena.

Bythrow, P. F.↗

DOE OSTI2024

Global fit of electron and neutrino elastic scattering data to determine the strange quark contribution to the vector and axial form factors of the nucleon

We present a global fit of neutral-current elastic (NCE) neutrino-scattering data and parity-violating electron-scattering (PVES) data with the goal of determining the strange quark contribution to the vector and axial form factors of the proton. Previous fits of this form included data from a variety of PVES experiments (PVA4, HAPPEx, G0, SAMPLE) and the NCE neutrino and anti-neutrino data from BNL E734. These fits did not constrain the strangeness contribution to the axial form factor G A s ( Q 2 ) at low Q 2 very well because there was no NCE data for Q 2 < 0.45 GeV 2 . Our new fit includes for the first time MiniBooNE NCE data from both neutrino and antineutrino scattering; this experiment used a hydrocarbon target and so a model of the neutrino interaction with the carbon nucleus was required. Three different nuclear models have been employed: a relativistic Fermi gas model, the superscaling approximation model, and a spectral function model. We find a tremendous improvement in the constraint of G A s ( Q 2 ) at low Q 2 compared to previous work, although more data is needed from NCE measurements that focus on exclusive single-proton final states, for example from MicroBooNE. Published by the American Physical Society 2024

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2012

ANALYSIS ON CORRELATIONS BETWEEN SUBSURFACE KINETIC HELICITY AND PHOTOSPHERIC CURRENT HELICITY IN ACTIVE REGIONS

An investigation on correlations between photospheric current helicity and subsurface kinetic helicity is carried out by analyzing vector magnetograms and subsurface velocities for two rapidly developing active regions. The vector magnetograms are from the Solar Dynamics Observatory/Helioseismic and Magnetic Imager (SDO/HMI) observed Stokes parameters, and the subsurface velocity is from time-distance data-analysis pipeline using HMI Dopplergrams. Over a span of several days, the evolution of the weighted current helicity shows a tendency similar to that of the weighted subsurface kinetic helicity, attaining a correlation coefficient above 0.60 for both active regions. Additionally, there seems to be a phase lag between the evolutions of the unweighted current and subsurface kinetic helicities for one of the active regions. The good correlation between these two helicities indicates that there is some intrinsic connection between the interior dynamics and photospheric magnetic twistedness inside active regions, which may help to interpret the well-known hemispheric preponderance of current-helicity distribution.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2019

Investigation of Fourth-leg for Common-mode Noise Reduction in Three-level Neutral Point Clamped Inverter Fed Motor Drive

The four-leg topology has been applied to two-level inverters for common-mode (CM) noise elimination. To achieve zero common-mode voltage (CMV), the zero vector typically used in the two-level inverter is not allowed. As a result, the reference cannot be synthesized by nearest three vectors, which introduces a penalty in dc voltage utilization and current THD. This paper applies the fourth-leg to three-level neutral point clamped (NPC) inverter fed motor drives. Unlike the case in the two-level inverter, the reference can be synthesized by the nearest three vectors while zero CMV can be achieved at the same time in a three-level inverter with the fourth-leg. The topology and modulation are presented. The fourth-leg filter structures are investigated, and a fourth-leg filter structure which decouples the fourth-leg from the main circuit power level is proposed for high power applications. The experiment results on a three-level NPC inverter show that with the fourth-leg and presented modulation applied, the CM noise has been significantly reduced, and around 25 dB attenuation can be observed at the first noise peak in the electromagnetic interference (EMI) frequency range.

Chen, Ruirui↗