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Results for “Relativistic charge distribution”

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.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

A bi-directional charged particle telescope to observe flux, energy spectrum and angular distribution of relativistic and non-relativistic particles

A Charged Particle Telescope (CPT) was designed, fabricated and calibrated to make the following observations: (1) discrimination between various singly charged particles, e.g., electrons, muons and protons, in about 5 to 100 MeV energy range; (2) measurement of the flux and the energy of the charged particles incident to the telescope from two opposite directions and stopping in the telescope, thus obtaining flux and energy spectrum of downward and upward moving charged particles; and (3) measurement of the broad angular distribution of selected particles as a function of azimuthal angle. This telescope can be used to study low energy electron, muon and proton energy spectra. The experiment was flown in a high altitude balloon from Hyderabad, India, in December 1984. This same equipment is also useful in ground level electron, muon spectrum study.

Verma, S. D.↗
DOE OSTI2025

Relativistic approach to manipulating angular distribution of charged particles via kinetic equations

Deflection angles of charged particles interacting with materials play a critical role in various plasma applications. The development of a mathematically well-posed kinetic collision operator that accounts for deflection angles of strong Coulomb interactions remains a fundamental open problem. This paper presents a relativistic method for modifying the electromagnetic field in an anisotropic and adjustable manner to manipulate a system of charged particles, specifically by the transfer of angular momentum from a superluminal wave source to particles at specific times and locations. The method provides a mechanism to influence the scattering outcomes of strong interactions by manipulating the angular distribution of particles, and thus the deflection angles of their interactions with a solid surface, without requiring detailed knowledge of the kinetic collision operator. To this end, we demonstrate how a specific type of singularity, generated by Maxwell's equations for a superluminal wave source at the boundary of the plasma, can modify the electromagnetic field in a highly directional manner. The proposed method can lead to the development of novel approaches for controlling interactions of charged particles with a material in plasma systems. Published by the American Physical Society 2025

Moini, Nima (ORCID:0009000929568824)↗
DOE OSTI2021

Fast Faraday cup for measuring the longitudinal distribution of particle charge density in non-relativistic beams

A Fast Faraday cup includes a group of electrodes including a ground electrode having a through hole and a collector electrode configured with a blind hole that functions a collector hole. The electrodes are configured to allow a beam (e.g., a non-relativistic beam) to fall onto the ground electrode so that the through hole cuts a beamlet that flies into the collector hole and facilitates measurement of the longitudinal distribution of particle charge density in the beam. The diameters, depths, spacing and alignment of the collector hole and the through hole are controllable to enable the Fast Faraday day cup to operate with a fast response time (e.g., fine time resolution) and capture secondary particles.

Sun, Ding↗
DOE OSTI2023

Fast faraday cup for measuring the longitudinal distribution of particle charge density in non-relativistic beams

A Fast Faraday Cup includes a group of electrodes including a grounded electrode having a through hole and a collector electrode configured with a blind hole that functions a collector hole. The electrodes are configured to allow a beam (e.g., a non-relativistic beam) to fall onto the grounded electrode so that the through hole cuts a beamlet that flies into the collector hole and facilitates measurement of the longitudinal distribution of particle charge density in the beam. The diameters, depths, spacing and alignment of the collector hole and the through hole are controllable to enable the Fast Faraday day cup to operate with a fast response time (e.g., fine time resolution) and capture secondary particles.

Sun, Ding↗
DOE OSTI2021

Nuclear charge densities in spherical and deformed nuclei: Toward precise calculations of charge radii

Precise measurements of atomic transitions affected by electron-nucleus hyperfine interactions offer sensitivity to explore basic properties of the atomic nucleus and study fundamental symmetries, including the search for new physics beyond the standard model of particle physics. Specifically, such measurements, augmented by atomic and nuclear calculations, will enable extraction of the higher-order radial moments of the charge-density distribution in spherical and deformed nuclei. The new data impose higher precision requirements on a theoretical description. The nuclear charge density is composed of the proton point distribution folded with the nucleonic charge distributions. The latter induce subtle relativistic corrections due to the coupling of nucleon magnetic moments with the nuclear spin-orbit density. Additional corrections come from the effect of center-of-mass projection. We assess the precision of nuclear charge density calculations by studying the behavior of relativistic and center-of-mass motion corrections to the second and fourth charge radial moments. Special attention has been paid to the magnetic spin-orbit density associated with the local variations of the spin-orbit current. The calculations for semimagic and open-shell nuclei are performed in the framework of self-consistent mean-field theory using quantified energy density functionals and density-dependent pairing forces. We used the general expression for the spin-orbit form factor that is valid for spherical and deformed nuclei. We studied the impact of various correction terms on the charge radii, fourth radial moments, diffraction radii, and surface thickness of spherical and deformed nuclei. The spin-orbit corrections to charge radial moments and surface thickness show strong shell fluctuations which can make an appreciable effect when aiming at high-precision predictions of isotopic shifts. The inclusion of relativistic and center-of-mass corrections impacts the quality of energy density functionals optimized to charge radii data. To establish reliable constraints on the existence of new forces from isotope shift measurements, precise calculations of nuclear charge densities of deformed nuclei are needed. The proper inclusion of the spin-orbit charge density and other correction terms is essential when aiming at extraction of subtle effects which become particularly visible in isotopic trends. It is also important when developing high-quality nuclear energy density functionals optimized using heterogeneous datasets involving absolute charge radii, differential charge radii, and charge form factor properties deduced from electron-scattering data.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Impact of a minority relativistic electron tail interacting with a thermal plasma containing high-atomic-number impurities

A minority relativistic electron component can arise in both laboratory and naturally-occurring plasmas. In the presence of high-atomic-number ion species, the ion charge state distribution at low bulk electron temperature can be dominated by relativistic electrons, even though their density is orders of magnitude lower. This is due to the relativistic enhancement of the collisional excitation and ionization cross sections. The resulting charge state effect can dramatically impact the radiative power loss rate and the related Bethe stopping power of relativistic electrons in a dilute plasma.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Transition radiation light sources

Transition radiation from nanotubes, nanosheets, and nanoparticles and in particular, boron nitride nanomaterials, can be utilized for the generation of light. Wavelengths of light of interest for microchip lithography, including 13.5 nm (91.8 eV) and 6.7 nm (185 eV), can be generated at useful intensities, by transition radiation light sources. Light useful for monitoring relativistic charged particle beam characteristics such as spatial distribution and intensity can be generated.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

Transition radiation light sources

Transition radiation from nanotubes, nanosheets, and nanoparticles and in particular, boron nitride nanomaterials, can be utilized for the generation of light. Wavelengths of light of interest for microchip lithography, including 13.5 nm (91.8 eV) and 6.7 nm (185 eV), can be generated at useful intensities, by transition radiation light sources. Light useful for monitoring relativistic charged particle beam characteristics such as spatial distribution and intensity can be generated.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Measurement of the Neutron Electromagnetic Form Factors at High Momentum Transfer Using a Polarized 3He Target at Jefferson Lab

Ever since the composite structure of nucleons was uncovered, many experiments have been commissioned with the purpose of extracting parameters that shape our understanding of this structure. Form factors are powerful tools that rest at the forefront of the nucleon structure study. In the non-relativistic limit, they describe the magnetic and charge distributions inside the nucleon. The GEn-II experiment, which ran in Hall A of Jefferson Lab as a part of the SuperBigbite Spectrometer (SBS) program, aimed to extract the ratio of the neutron’s electric to magnetic Sachs form factors (GnE/GnM. This was accomplished using the double polarization technique: scattering polarized electrons with initial energies up to 8.45 GeV off high-density polarized 3He targets. The experiment was a coincidence measurement, with the scattered electrons detected in the BigBite Spectrometer and the recoil nucleons in a hadron calorimeter, a part of the SuperBigbite Spectrometer. The convection-style target cells used in this experiment have a 60cm long target chamber, an increase from the 40 cm cell used in the most recent polarized 3He target experiment. In addition, the cells were optically pumped from two sides of the pumping chamber. These improvements in design and functionality introduced world-record-breaking luminosity. This thesis presents preliminary results of the GEn-II experiment for the following 4-momentum transfer (Q2) values: 2.93, 6.76, and 9.78 GeV2, in addition to target performance and preliminary polarimetry results.

Presley, Hunter [Univ. of Virginia, Charlottesvill↗
NASA NTRS1979

Cosmology of a charged universe

The Proca generalization of electrodynamics admits the possibility that the universe could possess a net electric charge uniformly distributed throughout space, while possessing no electric field. A general-relativistic model of cosmological expansion dominated by such a charged background has been calculated, and is consistent with present observational limits on the Hubble constant, the deceleration parameter, and the age of the universe. However, if this cosmology applied at the present epoch, the very early expansion of the universe would have been too rapid for cosmological nucleosynthesis or thermalization of the background radiation to have occurred. Hence, domination of the present expansion by background charge appears to be incompatible with the 3-K background and big-bang production of light elements. If the present background charge density were sufficiently small (but not strictly zero), expansion from the epoch of nucleosynthesis would proceed according to the conventional scenario, but the energy due to the background charge would have dominated at some earlier epoch. This last possibility leads to equality of pressure and energy density in the primordial universe.

Barnes, A.↗
DOE OSTI2023

Scaling approach to nuclear structure in high-energy heavy-ion collisions

In high-energy heavy-ion collisions, the initial condition of the produced quark-gluon plasma (QGP) and its evolution are sensitive to collective nuclear structure parameters describing the shape and radial profiles of the nuclei. Here, we find a general scaling relation between these parameters and many experimental observables such as elliptic flow, triangular flow, and particle multiplicity distribution. In particular, the ratios of observables between two isobar systems depend only on the differences of these parameters, but not on the details of the final state interactions, hence offering a new way to constrain the QGP initial condition. Using this scaling relation, we show how the structure parameters of $^{96}_{44}$Ru and $^{96}_{40}$Zr conspire to produce the rich centrality dependences of these ratios, as measured by the STAR Collaboration. Our scaling approach demonstrates that isobar collisions are a precision tool to probe the initial condition of heavy-ion collisions, as well as the collective nuclear structures, including the neutron skin, of the atomic nuclei across energy scales.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Understanding how minority relativistic electron populations may dominate charge state balance and radiative cooling of a post-thermal quench tokamak plasma

Minority relativistic electron populations can occur in a range of complex plasmas. Of specific interest is when runaway electrons form among the presence of high-atomic-number ion species in a tokamak plasma discharge. It has been recently demonstrated that ion charge state distributions and radiation losses at low bulk electron temperatures can be dominated by relativistic electrons, even though their density is orders of magnitude lower. Furthermore, this was attributed to the relativistic enhancement of electron impact inelastic cross sections. In this work, we provide a closer inspection of the atomic physics underpinning this effect. We also demonstrate the consequences of runaway enhanced scattering on post-disruption tokamak fusion discharges with neon and argon impurities present. Effects on charge state distributions, radiation and spectral characteristics, and reduced-order modeling considerations are discussed.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2022

Nuclear charge radii of Na isotopes: Interplay of atomic and nuclear theory

The accuracy of atomic theory calculations limits the extraction of nuclear charge radii from isotope shift measurements of odd-proton nuclei. For Na isotopes, though precise spectroscopic measurements have existed for more than half a century, calculations by different methods offer a wide range of values. Here, we present accurate atomic calculations to reliably extract the Na charge radii. By combining experimental matter radii with nuclear coupled-cluster calculations based on nucleon-nucleon and three-nucleon forces, we constrain the parameters obtained from the atomic calculations. Furthermore, this study guides atomic theory and highlights the importance of using accurate atomic and nuclear computations in our understanding of the size of light nuclei.

20 ≤ A ≤ 38↗
NASA NTRS1984

Electron capture by U(91+) and U(92+) and ionization of U(90+) and U(91+)

U(92+)/U(91+) and U(91+)/U(90+) electron-capture and ionization cross sections and equilibrium charge-state distributions are measured experimentally in mylar, Cu and Ta of varying thickness. Relativistic U(68+) ions at 437 or 962 MeV/nucleon are produced by a heavy-ion linear accelerator and synchrotron in tandem and passed through the target material into a magnetic specrometer and position-sensitive proportional counter for evaluation of charge states. The results are presented graphically and discussed. At 962 MeV/nucleon, beams containing 85 percent bare U(92+) nuclei are obtained using 150-mg/sq cm Cu or 85-mg/sq cm Ta; at 437 MeV/nucleon, 50 percent bare U(92+) nuclei are obtained with 90-mg/sq cm Cu. The techniques decribed can be applied to produce beams of bare U nuclei for acceleration to ultrarelativistic speeds or beams of few-electron U for atomic-physics experiments on quantum electrodynamics.

Gould, H.↗
DOE OSTI2022

Measuring neutron skin by grazing isobaric collisions

Neutron skin thickness (Δr np ) of nuclei and the inferred nuclear symmetry energy are of critical importance to nuclear physics and astrophysics. It is traditionally measured by nuclear processes with significant theoretical uncertainties. We recently proposed an indirect measurement of the Δr np by charged hadron multiplicities in central isobaric collisions at relativistic energies, which are sensitive to nuclear densities. In this Letter, we propose a direct measurement of the Δr np by using net-charge multiplicities in ultra-peripheral (grazing) collisions of those isobars, under the assumption that they are simple superimposition of nucleon-nucleon interactions. Here, we illustrate this novel approach by the TRENTO and URQMD models.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Collision-energy dependence of the Breit-Wheeler process in heavy-ion collisions and its application to nuclear charge radius measurements

The collision energy dependence of the cross section and the transverse momentum distribution of dielectrons from the Breit-Wheeler process in heavy-ion collisions are computed in the lowest-order QED and found to be sensitive to the nuclear charge distribution and the infrared divergence of the ultra-Lorentz-boosted Coulomb field. Within a given experimental kinematic acceptance, the cross section is found to increase while the pair transverse momentum ($\sqrt{\langle{p^2_T}\rangle}$) decreases with increasing beam energy. We demonstrate that the transverse-momentum component of Weizsäcker-Williams photons is due to the finite extent of the charge source and electric field component in the longitudinal direction. We further clarify the connection between the nuclear charge distribution and the kinematics of produced e + e - from the Breit-Wheeler process, and propose a criterion for the validity of the Breit-Wheeler process in relativistic heavy-ion collisions. Following this approach we demonstrate that the experimental measurements of the Breit-Wheeler process in ultrarelativistic heavy-ion collisions can be used to quantitatively constrain the nuclear charge radius. The extracted parameters show sensitivity to the impact parameter dependence, and can be used to study the initial-state and final-state effects in hadronic interactions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1982

On the geometric nature of high energy nucleus-nucleus reaction cross sections

Within the context of a high energy double-folding optical potential approximation to the exact nucleus-nucleus multiple-scattering series, eikonal scattering theory is used to investigate the validity of geometric reaction cross sections in relativistic heavy ion collisions. The potential used includes a finite range interaction and nuclear single-particle densities extracted from nuclear charge distributions by unfolding the finite proton charge distribution. Pauli correlation effects are also included in an approximate way. The sensitivity of the predictions to the assumed interaction, Pauli correlation approximation, and nuclear density distributions is investigated. These results are in agreement with early predictions concerning the geometric nature of relativistic heavy ion collisions and in disagreement with a recent analysis, utilizing the zero range approximation, which suggested otherwise. Reasons for the lack of agreement between the analyses are also presented. Finally, approximate applicability limits for geometric reaction cross sections are determined.

Townsend, L. W.↗