Search NASA⌕ Search

SEARCH · Search NASA

Results for “ELECTROMAGNETIC INTERACTIONS”

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 1,585 records · Page 88
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Reinvestigation of the level structures of the N=49 isotones 89 Zr and 91 Mo

Here, excited states of 89 Zr and 91 Mo have been investigated using the fusion reaction 6 Li+ 89 Y at beam energy of 34 MeV. Based on new experimental data, about 16 (13) new transitions have been added to the level scheme of 89 Zr ( 91 Mo). The level structures are investigated in the framework of the spherical-basis shell model using the effective interactions JUN45 and GWBXG. Reasonable agreement is obtained between the experimental results and the calculations. The calculated results indicate the newly proposed states are characterized by proton excitations from the 1f 5/2 , 2p 3/2 , 2p 1/2 orbits to the high-j 1g 9/2 orbit. The systematic features of low lying states in the N = 49 isotones are discussed.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Electron scattering on A = 3 nuclei from quantum Monte Carlo based approaches

We perform first-principle calculations of electron-nucleus scattering on 3 He and 3 H using the Green's function Monte Carlo method and two approaches based on the factorization of the final hadronic state: the spectral-function formalism and the short-time approximation. These three methods are benchmarked among each other and compared to the experimental data for the longitudinal and transverse electromagnetic response functions of 3 He, and the inclusive cross sections of both 3 He and 3 H. Since these three approaches are based on the same description of nuclear dynamics of the initial target state, comparing their results enables a precise quantification of the uncertainties inherent to factorization schemes. At sufficiently large values of the momentum transfer, we find an excellent agreement of the Green's function Monte Carlo calculation with experimental data and with both the spectral-function formalism and the short-time approximation. Here, we also analyze the relevance of relativistic effects, whose inclusion becomes crucial to explain data at high momentum and energy transfer.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Unique Forbidden Beta Decays at Zero Momentum Transfer

We report an exploratory study of the 𝒪⁡(𝛼) structure-dependent electromagnetic radiative corrections to unique first-forbidden nuclear beta decays. We show that the insertion of angular momentum into the nuclear matrix element by the virtual or real photon exchange opens up the decay at vanishing nuclear recoil momentum which was forbidden at tree level, leading to a dramatic change in the decay spectrum not anticipated in existing studies. We discuss its implications for precision tests on the standard model and searches for new physics.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Non-Markovian dynamics of a superconducting qubit in an open multimode resonator

In this work, we study the dynamics of a transmon qubit that is capacitively coupled to an open multimode superconducting resonator. Our effective equations are derived by eliminating resonator degrees of freedom while encoding their effect in the Green's function of the electromagnetic background. We account for the dissipation of the resonator exactly by employing a spectral representation for the Green's function in terms of a set of non-Hermitian modes and show that it is possible to derive effective Heisenberg-Langevin equations without resorting to the rotating-wave, two-level, Born, or Markov approximations. A well-behaved time-domain perturbation theory is derived to systematically account for the nonlinearity of the transmon. We apply this method to the problem of spontaneous emission, capturing accurately the non-Markovian features of the qubit dynamics, valid for any qubit-resonator coupling strength.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Applicability of semiclassical theories in the strong-field plasma regime

For many purposes, classical plasma dynamics models can work surprisingly well, even for strong electromagnetic fields, approaching the Schwinger critical fields, and high frequencies, approaching the Compton frequency. However, the applicability of classical models tends to depend rather sensitively on the details of the problem. In the present paper, we study the specific case of plasma oscillations to draw a line between the classical and quantum relativistic regimes. Here, due to the field geometry of study, mechanisms like radiation reaction and Breit-Wheeler pair production, which tend to be important for electromagnetic fields, are rather effectively suppressed. Moreover, we find that the polarization current due to the electron spin is generally negligible for frequencies below the Compton frequency, compared with the free current, whose magnitude is well-approximated by the classical Vlasov theory. However, we show that pair creation due to the Schwinger mechanism can sometimes be important for surprisingly modest field strengths, of the order of 10% of the critical field or even smaller. A rough guideline for when the classical Vlasov theory can be applied is given.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Space Charge Effects in Low Energy Magnetized Electron Beams

Magnetized electron cooling of the ion beam is one of the major approaches towards obtaining the required high luminosity in the proposed Electron-Ion Collider (EIC). To increase the cooling efficiency, a bunched electron beam with a high bunch charge and high repetition rate is required. However, these features can combine to enhance the collective interactions, such as the space charge effect. A magnetized electron beam was successfully generated at the Thomas Jefferson National Accelerator Facility (JLab) using a compact, 300 kV DC high voltage photo-gun with an inverted insulator geometry and bi-alkali antimonide photocathode. The beam magnetization was characterized using a modest diagnostic beamline to measure beam sizes, rotation angles, and normalized transverse emittance as a function of magnetic field at the photocathode, laser spot size, and gun high-voltage. Simultaneously, simulations were performed using the A Space Charge Tracking Algorithm (ASTRA) and General Particle Tracer (GPT) programs. Further, sustained high average current magnetized beam up to 28 mA was demonstrated, and the photocathode lifetime for different magnetized electron beam currents was investigated. In the second part of the project, the space charge effect in low-energy magnetized electron beams was studied and compared with GPT simulations. The high bunch charge studies showed evidence of space charge current limitations starting at 0.3 nC and limited the maximum delivered bunch charge to 0.7 nC. To reach the high bunch charge goal of a few nC, the existing DC photo-gun design was modified using CST Studio Suite’s electromagnetic field solver, and a way to cancel the beam deflection exerted by the non-symmetric nature of the inverted insulator photo-gun geometry was discovered. This thesis presents a detailed description of the generation, characterization, and simulation of high current, high bunch charge magnetized electron beams at JLab, as well as the modified photo-gun design. Together with measurements and simulations, the purpose of this thesis is to provide a solid background on the theoretical aspects and the experimental challenges associated with magnetized electron beams for accelerator applications.

Wijethunga, W M Sajini↗
DOE OSTI2022

Ab initio coupled-cluster calculations of ground and dipole excited states in He 8

We perform coupled-cluster calculations of ground- and dipole excited-state properties of the 8 He halo nucleus with nucleon-nucleon and three-nucleon interactions from chiral effective field theory, both with and without explicit delta degrees of freedom. By increasing the precision in our coupled-cluster calculations via the inclusion of leading-order three-particle three-hole excitations in the cluster operator, we obtain a ground-state energy and a charge radius that are consistent with experiment, albeit with a slight underbinding. We also investigate the excited states induced by the electric dipole operator and present a discussion on the Thomas-Reiche-Kuhn and cluster sum rules. Lastly, we compute the electric dipole polarizability, providing a theoretical benchmark for future experimental determinations that will study this exotic nucleus.

6 ≤ A ≤ 19↗
DOE OSTI2022

Robust ab initio prediction of nuclear electric quadrupole observables by scaling to the charge radius

Meaningful predictions for electric quadrupole (E2) observables from ab initio nuclear theory are necessary, if the ab initio description of collective correlations is to be confronted with experiment, as well as to provide predictive power for unknown E2 observables. However, converged results for E2 observables are notoriously challenging to obtain in ab initio no-core configuration interaction (NCCI) approaches. Matrix elements of the E2 operator are sensitive to the large-distance tails of the nuclear wave function, which converge slowly in an oscillator basis expansion. Similar convergence challenges beset ab initio prediction of the nuclear charge radius. We demonstrate that the convergence patterns of the E2 and radius observables are strongly correlated, and that meaningful predictions for the absolute scale of E2 observables may be made by calibrating to the experimentally-known ground-state charge radius. Here, we illustrate by providing robust ab initio predictions for several E2 transition strengths and quadrupole moments in p-shell nuclei, in cases where experimental results are available for comparison.

6 ≤ A ≤ 19↗
DOE OSTI2023

Measurement of the $\textit{B}(\textit{E}2 ↑)$ strengths of 36 Ca and 38 Ca

In this work, the $B(E2, 0^+_1 → 2^+_1)$ strengths of 36 Ca and 38 Ca are measured to be 131(20) $e^2\text{fm}^4$ and 101(11) $e^2\text{fm}^4$, respectively. The $\textit{B}(\textit{E}2)$ value for 36 Ca required a measurement of the p/γ branching ratio because the 2 + state is proton unbound. This branching ratio is $B_p$=0.087(8). These $\textit{B}(\textit{E}2)$ and branching-ratio values can be reproduced in the shell-model with the ZMB2 interaction, an interaction that predicts the $\textit{Z} = 20 \textit{sd}$-shell closure is incomplete with large proton pf-shell occupancies in the ground state. These occupancies are at odds with other shell-model and energy-density-functional calculations of 36 Ca. New data are used to provide an update on constraints of the density dependence of the symmetry energy through mirror charge-radii differences as well as to help reduce uncertainties of the astrophysical important 35 K(p,γ) reaction.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Nonlinear ionization dynamics of hot dense plasma observed in a laser-plasma amplifier

Understanding the behaviour of matter under conditions of extreme temperature, pressure, density and electromagnetic fields has profound effects on our understanding of cosmologic objects and the formation of the universe. Lacking direct access to such objects, our interpretation of observed data mainly relies on theoretical models. However, such models, which need to encompass nuclear physics, atomic physics and plasma physics over a huge dynamic range in the dimensions of energy and time, can only provide reliable information if we can benchmark them to experiments under well-defined laboratory conditions. Due to the plethora of effects occurring in this kind of highly excited matter, characterizing isolated dynamics or obtaining direct insight remains challenging. High-density plasmas are turbulent and opaque for radiation below the plasma frequency and allow only near-surface insight into ionization processes with visible wavelengths. Here, the output of a high-harmonic seeded laser-plasma amplifier using eight-fold ionized krypton as the gain medium operating at a 32.8 nm wavelength is ptychographically imaged. A complex-valued wavefront is observed in the extreme ultraviolet (XUV) beam with high resolution. Ab initio spatio-temporal Maxwell–Bloch simulations show excellent agreement with the experimental observations, revealing overionization of krypton in the plasma channel due to nonlinear laser-plasma interactions, successfully validating this four-dimensional multiscale model. This constitutes the first experimental observation of the laser ion abundance reshaping a laser-plasma amplifier. The presented approach shows the possibility of directly modelling light-plasma interactions in extreme conditions, such as those present during the early times of the universe, with direct experimental verification.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Electroexcitation of Nucleon Resonances and Emergence of Hadron Mass

Developing an understanding of phenomena driven by the emergence of hadron mass (EHM) is one of the most challenging problems in the Standard Model. This discussion focuses on the impact of results on nucleon resonance (𝑁 ∗ ) electroexcitation amplitudes (or 𝛾 𝑣 𝑝𝑁 ∗ electrocouplings) obtained from experiments during the 6 GeV era in Hall B at Jefferson Lab on understanding EHM. Analyzed using continuum Schwinger function methods (CSMs), these results have revealed new pathways for the elucidation of EHM. A good description of the Δ(1232)3/2 + , 𝑁(1440)1/2 + , and Δ(1600)3/2 + electrocouplings, achieved by CSM analyses that express a realistic dressed quark mass function, sheds light on the strong interaction dynamics underlying EHM. Extensions to 𝑁 ∗ studies for higher-mass states are outlined, as well as experimental results anticipated in the 12 GeV era at Jefferson Lab and those that would be enabled by a further increase in the beam energy to 22 GeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Onset of band structure in 70 Ga

Excited states in the odd-odd nucleus 70 Ga were studied using the 62 Ni( 14 C, αpn) fusion-evaporation reaction at the John D. Fox Superconducting Accelerator Laboratory at Florida State University with a 50 MeV beam. Depopulating γ rays were measured in coincidence with a Compton-suppressed Ge array consisting of three Clover detectors and seven single-crystal detectors. Analysis of γ–γ coincidences led to the addition of 16 new transitions to the 70 Ga level scheme, including transitions associated with the onset of a new positive-parity band structure likely based on the πg 9/2 ⊗ νg 9/2 configuration. Spins and parities were assigned using directional correlation of oriented nuclei (DCO) ratios and linear polarization measurements. Shell-model calculations with the JUN45 effective interaction reproduce the excitation energies of the positive-parity states reasonably well but predict negative-parity states that are typically 400–500 keV lower than observed. Furthermore, total Routhian surface calculations for the lowest positive-parity configuration with signature α = 0 indicate significant triaxiality (γ ≈ −20°) and the development of competing non-collective excitations at J = 8, corresponding to the experimentally observed onset of the positive-parity band. Similar features are found in the calculated surfaces for the lowest negative-parity states with α = 0.

59 ≤ A ≤ 89↗
DOE OSTI2015

Helicon modes in uniform plasmas. III. Angular momentum

Helicons are electromagnetic waves with helical phase fronts propagating in the whistler mode in magnetized plasmas and solids. They have similar properties to electromagnetic waves with angular momentum in free space. Helicons are circularly polarized waves carrying spin angular momentum and orbital angular momentum due to their propagation around the ambient magnetic field B{sub 0}. These properties have not been considered in the community of researchers working on helicon plasma sources, but are the topic of the present work. The present work focuses on the field topology of helicons in unbounded plasmas, not on helicon source physics. Helicons are excited in a large uniform laboratory plasma with a magnetic loop antenna whose dipole axis is aligned along or across B{sub 0}. The wave fields are measured in orthogonal planes and extended to three dimensions (3D) by interpolation. Since density and B{sub 0} are uniform, small amplitude waves from loops at different locations can be superimposed to generate complex antenna patterns. With a circular array of phase shifted loops, whistler modes with angular and axial wave propagation, i.e., helicons, are generated. Without boundaries radial propagation also arises. The azimuthal mode number m can be positive or negative while the field polarization remains right-hand circular. The conservation of energy and momentum implies that these field quantities are transferred to matter which causes damping or reflection. Wave-particle interactions with fast electrons are possible by Doppler shifted resonances. The transverse Doppler shift is demonstrated. Wave-wave interactions are also shown by showing collisions between different helicons. Whistler turbulence does not always have to be created by nonlinear wave-interactions but can also be a linear superposition of waves from random sources. In helicon collisions, the linear and/or orbital angular momenta can be canceled, which results in a great variety of field topologies. The work will be contrasted to the research on helicon plasma sources.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2022

SPACE: 3D parallel solvers for Vlasov-Maxwell and Vlasov-Poisson equations for relativistic plasmas with atomic transformations

A parallel, relativistic, three-dimensional particle-in-cell code SPACE has been developed for the simulation of electromagnetic fields, relativistic particle beams, and plasmas. In addition to the standard second-order Particle-in-Cell (PIC) algorithm, SPACE includes efficient novel algorithms to resolve atomic physics processes such as multi-level ionization of plasma atoms, recombination, and electron attachment to dopants in dense neutral gases. SPACE also contains a highly adaptive particle-based method, called Adaptive Particle-in-Cloud (AP-Cloud), for solving the Vlasov-Poisson problems. It eliminates the traditional Cartesian mesh of PIC and replaces it with an adaptive octree data structure. The code's algorithms, structure, capabilities, parallelization strategy, and performance have been discussed. Additionally, typical examples of SPACE applications to accelerator science and engineering problems are described.

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

Variational Self-Consistent Theory for Beam-Loaded Cavities

A new variational theory is presented for beam loading in microwave cavities. The beam{field interaction is formulated as a dynamical interaction whose stationarity according to Hamilton’s principle will naturally lead to steady-state solutions that indicate how a cavity’s resonant frequency, Q and optimal coupling coefficient will detune as a result of the beam loading. A driven cavity Lagrangian is derived from first principles, including the effects of cavity wall losses, input power and beam interaction. The general formulation is applied to a typical klystron input cavity to predict the appropriate detuning parameters required to maximize the gain (or modulation depth) in the average Lorentz factor boost, (Δ γ). Numerical examples are presented, showing agreement with the general detuning trends previously observed in the literature. The developed formulation carries several advantages for beam-loaded cavity structures. It provides a self-consistent model for the dynamical (nonlinear) beam{field interaction, a procedure for maximizing gain under beam-loading conditions, and a useful set of parameters to guide cavity-shape optimization during the design of beam-loaded systems. Enhanced clarity of the physical picture underlying the problem seems to be gained using this approach, allowing straightforward inclusion or exclusion of different field configurations in the calculation and expressing the final results in terms of measurable quantities. Two field configurations are discussed for the klystron input cavity, using finite magnetic confinement or no confinement at all. Formulating the problem in a language that is directly accessible to the powerful techniques found in Hamiltonian dynamics and canonical transformations may potentially carry an additional advantage in terms of analytical computational gains, under suitable conditions

43 PARTICLE ACCELERATORS↗
DOE OSTI2024

Off-shell pion properties: Electromagnetic form factors and light-front wave functions

The off-shell pion electromagnetic form factors are explored with corresponding off-shell light-front wave functions modeled by constituent quark and antiquark. We apply the Mandelstam approach for the microscopic computation of the form factors relating the model parameters with the pion decay constant and charge radius. Analyzing the existing data on the cross sections for the Sullivan process, 1 H(e,e',π + )⁢n, Charged pion form factor between Q 2 = 0.60, and 2.45 GeV 2 . I. Measurements of the cross section for the 1 H⁡(e,e'⁢π + )⁢n reaction, we extract the off-shell pion form factor using the relation derived from the generalized Ward-Takahashi identity for the pion electromagnetic current. They are compared with our previous results from exactly solvable manifestly covariant model of a (3+1)-dimensional fermion field theory. We find that the adopted constituent quark model reproduces the extracted off-shell form factor F 1 ⁡(Q 2 ,t) from the experimental data within a few percent difference and matches well with our previous theoretical simulation which exhibits a variation of about 10% for the extracted off-shell pion form factor g(Q 2 ,t). We also identify the pion valence parton distribution function (PDF) and transverse momentum distribution (TMD) in terms of the light-front wave function and discuss their off-shell properties.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

The time resolved measurement of ultrashort terahertz-band electric fields without an ultrashort probe

The time-resolved detection of ultrashort pulsed THz-band electric field temporal profiles without an ultrashort laser probe is demonstrated. A non-linear interaction between a narrow-bandwidth optical probe and the THz pulse transposes the THz spectral intensity and phase information to the optical region, thereby generating an optical pulse whose temporal electric field envelope replicates the temporal profile of the real THz electric field. This optical envelope is characterised via an autocorrelation based FROG (frequency resolved optical gating) measurement, hence revealing the THz temporal profile. The combination of a narrow-bandwidth, long duration, optical probe, and self-referenced FROG makes the technique inherently immune to timing jitter between the optical probe and THz pulse and may find particular application where the THz field is not initially generated via ultrashort laser methods, such as the measurement of longitudinal electron bunch profiles in particle accelerators.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Noise dependence with pile-up in the ATLAS Tile Calorimeter. Pile-up noise studies in the ATLAS TileCal calorimeter

The Tile Calorimeter, TileCal, is the central hadronic calorimeter of the ATLAS experiment, positioned between the electromagnetic calorimeter and the muon chambers. It comprises alternating layers of steel (as absorber material) and plastic (as active material), known as tiles. Between 2009 and 2012, the LHC has performed better than expected producing proton-proton collisions at a very high rate. These conditions are really challenging when dealing with the energy measurements in the calorimeter since not only the energy from an interesting event will be measured but a component coming from other collisions, which are difficult to distinguish from the interesting one, will also be present. This component is referred to as pile-up noise. Studies carried out to better understand how pile-up affects calorimeter noise under different circumstances are described. (author)

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗