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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

A portable on-axis laser-heating system for near-90° X-ray spectroscopy: application to ferropericlase and iron silicide

A portable IR fiber laser-heating system, optimized for X-ray emission spectroscopy (XES) and nuclear inelastic scattering (NIS) spectroscopy with signal collection through the radial opening of diamond anvil cells near 90°with respect to the incident X-ray beam, is presented. The system offers double-sided on-axis heating by a single laser source and zero attenuation of incoming X-rays other than by the high-pressure environment. A description of the system, which has been tested for pressures above 100 GPa and temperatures up to 3000 K, is given. The XES spectra of laser-heated Mg 0.67 Fe 0.33 O demonstrate the potential to map the iron spin state in the pressure–temperature range of the Earth's lower mantle, and the NIS spectra of laser-heated FeSi give access to the sound velocity of this candidate of a phase inside the Earth's core. This portable system represents one of the few bridges across the gap between laser heating and high-resolution X-ray spectroscopies with signal collection near 90°.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS2005

Protection against UV and X-ray cataracts using dynamic light scattering

Static and dynamic light scattering (SLS and DLS) analysis was used to investigate the aggregation of lens proteins in a hyperbaric oxygen (HBO)/guinea pig in vivo model for nuclear cataract. Nuclear cataract, an opacity which occurs in the center of the lens, is a major type of human maturity-onset cataract for which the cause is not well-understood. HBO is commonly used in major hospitals for treating complications such as poor wound healing due to impaired blood circulation. It is known that treatment of human patients with HBO for extended periods of time can produce nuclear cataract. Guinea pigs, initially 18 months old, were treated with HBO (2.5 atm of 100% O2 for 2.5 hr) 3x per week for 7 months to increase tie level of lens nuclear light scattering. Age-matched animals were used for controls. The eyes of the animals were analyzed in vivo using an integrated static and DLS fiber optic probe in collaboration with the NASA group. DLS in vivo was used to measure the size of lens proteins at 50 different locations across the optical axis of the guinea pig lens.

Giblin, Frank J.↗
DOE OSTI2024

Suppression of diffraction in deep-inelastic scattering on nuclei and dynamical mechanism of leading twist nuclear shadowing

Abstract Using the leading twist approach (LTA) to nuclear shadowing, we calculate the ratios of diffractive and usual parton distributions for a heavy nucleus (Pb) and the proton,$$ {R}_{A/p}=\left({f}_{i/A}^{D(3)}/{f}_{i/A}\right)/\left({f}_{i/p}^{D(3)}/{f}_{i/p}\right) $$ R A / p = f i / A D 3 / f i / A / f i / p D 3 / f i / p , for coherent and summed (coherent plus quasi-elastic) nuclear deep-inelastic scattering. We find thatR A/p ≈ 0.5 − 1 for quarks as well as for the ratio of the diffractive and total cross sections$$ {\left[\left({d\sigma}_{\textrm{diff}}/{d M}_X^2\right)/{\sigma}_{\textrm{tot}}\right]}_{eA}/{\left[\left({d\sigma}_{\textrm{diff}}/{d M}_X^2\right)/{\sigma}_{\textrm{tot}}\right]}_{ep} $$ dσ diff / dM X 2 / σ tot eA / dσ diff / dM X 2 / σ tot ep andR A/p ≈ 0.5 − 1.3 for gluons in a broad range ofx, including the kinematics of the Electron-Ion Collider, which reaffirms the difference from the nuclear enhancement ofR A/p predicted in the gluon saturation framework. We demonstrate that the magnitude ofR A/p is controlled by the cross section of the interaction of hadronic fluctuations of the virtual photon with target nucleons, which explains an enhancement ofR A/p in the color dipole model and its suppression in LTA. We argue that the black disk limit corresponds toR A/p = 1 and$$ {R}_{A/p}^{\textrm{coh}} $$ R A / p coh = 0.86 for the summed and coherent scattering, respectively. Relying on an intuitive definition of the saturation scale, we show that the ratio of the saturation scales of a heavy nucleus and proton$$ {Q}_{sA}^2(b)/{Q}_{sp}^2(b)\approx 1 $$ Q sA 2 b / Q sp 2 b ≈ 1 at small impact parametersbdue to the strong leading twist nuclear shadowing and diluteness of the nuclear density.

Physics↗
DOE OSTI2024

Momentum informed muon scattering tomography for monitoring spent nuclear fuels in dry storage cask

Development of an effective monitoring method for spent nuclear fuel (SNF) in a dry storage cask (DSC) is important to meet the increasing demand for dry storage investigations. The DSC investigation should provide information about the quantity of stored SNF, and quality assurance of materials should be possible without opening the cask. However, traditional nondestructive examination (NDE) methods such as x-rays are difficult to deploy for DSC investigation because a typical DSC is intentionally designed to shield against radiation. To address this challenge, cosmic ray muons (CRMs) are used as an alternative NDE radiation probe because they can easily penetrate an entire DSC system; however, a wide application of muons is often hindered due to the naturally low CRM flux (~10 4 muons/m 2 /min). This paper introduces a newly proposed imaging algorithm, momentum-informed muon scattering tomography (MMST) , and presents how a limitation of the current muon scattering tomography technique has been addressed by measuring muon momentum. To demonstrate its functionality, a commercial DSC with 24 pressurized light water reactor fuel assemblies (FAs) and the MMST system were designed in GEANT4. Three noticeable improvements were observed for MMST system as a DSC investigation tool: (1) a signal stabilization, (2) an enhanced capability to differentiate various materials, and (3) statistically increased precision to identify and locate missing FAs. The results show that MMST improves the investigation accuracy from 79 to 98% when one FA is missing and 51% to 88% when one-half FA is missing. The advancement of the NDE technique using CRM for DSC verification is expected to resolve long-standing problems in increasing demand for DSC inspections and nuclear security.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2022

Sub Coulomb barrier d+ 208 Pb scattering in the time-dependent basis function approach

We employ the non-perturbative time-dependent basis function (tBF) approach to study the scattering of the deuteron on 208 Pb below the Coulomb barrier. We obtain the bound and discretized scattering states of the projectile, which form the basis representation of the tBF approach, by diagonalizing a realistic Hamiltonian in a large harmonic oscillator basis. We find that the higher-order inelastic scattering effects are noticeable for sub barrier scatterings with the tBF method. We have successfully reproduced experimental sub Coulomb barrier elastic cross section ratios with the tBF approach by considering only the electric dipole (E1) component of the Coulomb interaction between the projectile and the target during scatterings. Here, we find that the correction of the polarization potential to the Rutherford trajectory is dominant in reproducing the data at very low bombarding energies, whereas the role of internal transitions of the deuteron projectile induced by the E1 interaction during the scattering becomes increasingly significant at higher bombarding energies.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1994

An ASCA observation of the Seyfert 2 galaxy Markarian 3

We report preliminary results of an ASCA observation of the Seyfert 2 galaxy Markarian 3 (Mkn 3). Comparison with previous Ginga and Broad-Band X-ray Telescope (BBXRT) observations shows that the observed hard X-ray luminosity above 4 keV decreased by a factor of approximately 3 (intrinsic luminosity by almost a factor of 6) in a period of approximately 3.6 yr. On the other hand, the soft luminosity has not varied significantly in approximately 13 yr, lending support to the extended nature of the soft emission, perhaps dominated by scattering of the nuclear X-rays. ASCA resolves the Fe K line emission into at least two components for the first time. The dominant component at 6.4 keV has an equivalent width of approximately 860 eV and full width at half maximum (FWHM) approximately equals 10(exp 4) km/sec, while the second component has an equivalent width of approximately 190 eV and appears to be narrower than the first. The total intensity of the Fe K emission decreased by factor of over 3 in response to the decrease in the continuum level, implying that a substantial part of the dominant Fe K emission must originate in a region smaller than that responsible for the soft emission. The variability provides direct evidence that the hard X-ray continuum and Fe K line in this Seyfert 2 are being observed directly through the nuclear obscuring material, not in scattered light.

Iwasawa, Kazushi↗
DOE OSTI2020

Simultaneous observation of nuclear and electronic dynamics by ultrafast electron diffraction

Simultaneous observation of nuclear and electronic motion is crucial for a complete understanding of molecular dynamics in excited electronic states. It is challenging for a single experiment to independently follow both electronic and nuclear dynamics at the same time. In this paper we show that ultrafast electron diffraction can be used to simultaneously record both electronic and nuclear dynamics in isolated pyridine molecules, naturally disentangling the two components. Electronic state changes (S 1 →S 0 internal conversion) were reflected by a strong transient signal in small-angle inelastic scattering, and nuclear structural changes (ring puckering) were monitored by large-angle elastic diffraction. Supported by ab initio nonadiabatic molecular dynamics and diffraction simulations, our experiment provides a clear view of the interplay between electronic and nuclear dynamics of the photoexcited pyridine molecule.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Electron ionization via dark matter-electron scattering and the Migdal effect

There are currently several existing and proposed experiments designed to probe sub-GeV dark matter (DM) using electron ionization in various materials. The projected signal rates for these experiments assume that this ionization yield arises only from DM scattering directly off electron targets, ignoring secondary ionization contributions from DM scattering off nuclear targets. We investigate the validity of this assumption and show that if sub-GeV DM couples with comparable strength to both protons and electrons, as would be the case for a dark photon mediator, the ionization signal from atomic scattering via the Migdal effect scales with the atomic number Z and 3-momentum transfer q as Z 2 q 2 . The result is that the Migdal effect is always subdominant to electron scattering when the mediator is light, but that Migdal-induced ionization can dominate over electron scattering for heavy mediators and DM masses in the hundreds of MeV range. We put these two ionization processes on identical theoretical footing, address some theoretical uncertainties in the choice of atomic wave functions used to compute rates, and discuss the implications for DM scenarios where the Migdal process dominates, including for XENON10, XENON100, and the recent XENON1T results on light DM scattering.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Color glass condensate meets high twist expansion

We establish the correspondence between two well-known frameworks for quantum chromodynamics (QCD) multiple scattering in nuclear media: the color glass condensate (CGC) and the high-twist (HT) expansion formalism. We argue that a consistent matching between both frameworks, in their common domain of validity, is achieved by incorporating the subeikonal longitudinal momentum phase in the CGC formalism, which mediates the transition between coherent and incoherent scattering. We perform a detailed calculation and analysis of direct photon production in proton-nucleus scattering as a concrete example to establish the matching between HT and CGC up to twist-4, including initial- and final-state interactions, as well as their interferences. The techniques developed in this work can be adapted to other processes in electron-nucleus and proton-nucleus collisions, and they provide a potential avenue for a unified picture of dilute-dense dynamics in nuclear media.

quantum chromodynamics↗
NASA NTRS1984

An abrasion-ablation model description of galactic heavy-ion fragmentation

The fragmentation of high-energy galactic heavy ions by nuclear interactions with arbitrary target nuclei is described within the context of a simple abrasion-ablation fragmentation model. The abrasion part of the theory utilizes a quantum-mechanical formalism based upon an optical model potential approximation to the exact nucleus-nucleus multiple-scattering series. Nuclear charge distributions of the excited prefragments are calculated using either a hypergeometric distribution or a method based upon the zero-point oscillations of the giant dipole resonance. The excitation energy of the prefragment is estimated from the geometric clean-cut abrasion-ablation model. The decay probabilities for the various particle emission channels, in the ablation stage of the fragmentation, are obtained from the EVAP-4 Monte Carlo computer program. Elemental production cross sections for 1.88-GeV/nucleon iron colliding with carbon, silver, and lead targets are calculated and compared with experimental data and with the predictions from the semiempirical relations of Silberberg and Tsao.

Townsend, L. W.↗
NASA NTRS1985

Bolometric detection of neutrinos

Elastic neutrino scattering off electrons in crystalline silicon at 1-10 mK results in measurable temperature changes in macroscopic amounts of material, even for low-energy (less than 0.41-MeV) pp neutrinos from the sun. New detectors for bolometric measurement of low-energy neutrino interactions, including coherent nuclear elastic scattering, are proposed. A new and more sensitive search for oscillations of reactor antineutrinos is practical (about 100 kg of Si), and would lay the groundwork for a more ambitious measurement of the spectrum of pp, Be-7, and B-8 solar neutrinos, and of supernovae anywhere in the Galaxy (about 10 tons of Si).

Cabrera, B.↗
DOE OSTI2020

Parity- and Time-Reversal-Violating Nuclear Forces

Parity-violating and time-reversal conserving (PVTC) and parity-violating and time-reversal-violating (PVTV) forces in nuclei form only a tiny component of the total interaction between nucleons. The study of these tiny forces can nevertheless be of extreme interest because they allow one to obtain information on fundamental symmetries using nuclear systems. The PVTC interaction derives from the weak interaction between the quarks inside nucleons and nuclei, therefore the study of PVTC effects opens a window on the quark-quark weak interaction. The PVTV interaction is sensitive to more exotic interactions at the fundamental level, in particular to strong CP violation in the Standard Model Lagrangian, or even to exotic phenomena predicted in various beyond-the-Standard-Model scenarios. The presence of these interactions can be revealed either by studying various asymmetries in polarized scattering of nuclear systems, or by measuring the presence of non-vanishing permanent electric dipole moments of nucleons, nuclei and diamagnetic atoms and molecules. In this contribution, we review the derivation of the nuclear PVTC and PVTV interactions within various frameworks. We focus in particular on the application of chiral effective field theory, which allows for a more strict connection with the fundamental interactions at the quark level. We investigate PVTC and PVTV effects induced by these potentials on several few-nucleon observables, such as the longitudinal asymmetries in proton-proton scattering and the 3 He($\vec{n}$,p) 3 H reaction, the radiative neutron-proton capture, and the electric dipole moments of the deuteron and the trinucleon system.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Benchmarking intra-nuclear cascade models for neutrino scattering with relativistic optical potentials

The description of final-state interactions (FSI) in the large phase space probed in neutrino experiments poses a great challenge. In neutrino experiments, which operate under semi-inclusive conditions, cascade models are commonly used for this task, while under exclusive conditions FSI can be treated with relativistic optical potentials (ROP). We formulate conditions under which the ROP approach and cascade model can be directly compared. We feed the NEUT cascade with events from a relativistic distorted-wave impulse approximation calculation that uses the real part of an optical potential. Cuts on the missing energy of the resulting events are applied to define a set of events that can be directly compared to RDWIA calculations with the full optical potential. The NEUT cascade and ROP agree for proton kinetic energies $T_p > 150$ MeV for carbon, oxygen and calcium nuclei when a realistic nuclear density is used to introduce events in the cascade. For $T_p < 100$ MeV the ROP and NEUT cross sections differ in shape and differences in magnitude are larger than 50 %. Single transverse variables allow to distinguish different approaches to FSI, but due to a large non-QE contribution the comparison to T2K data does not give an unambiguous view of FSI. We discuss electron scattering and argue that with a cut in missing energy FSI can be studied with minimal confounding factors in e.g. $e4\nu$. The agreement of the ROP and NEUT for T2K conditions lends confidence to these models as a tool in oscillation analyses for sufficiently large nucleon kinetic energies. These results urge for caution when a cascade model is applied for small nucleon energies. The assessment of model assumptions relevant to this region are strongly encouraged. This paper provides novel constraints on cascade models from proton-nucleus scattering that can be easily applied to other neutrino event generators.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

An all-digital associated particle imaging system for the 3D determination of isotopic distributions

Associated particle imaging (API) is a non-destructive nuclear technique for the 3D determination of isotopic distributions. By detecting the alpha particle associated with the emitted neutron in the deuterium–tritium fusion reaction with a position- and time-resolving detector, the direction of the 14.1 MeV neutron and its time of emission can be determined. Employing this method, isotope characteristic gamma rays emitted in inelastic neutron scattering events can be correlated with the neutron interaction location. Here, an API system consisting of a sealed-type neutron generator, gamma detectors, and a position-sensitive alpha detector was designed, constructed, and characterized. The system was tested with common soil elements and shown to be sensitive to 12 C, 16 O, 28 Si, 27 Al, and 56 Fe. New aspects of our approach are the use of a yttrium–aluminum–perovskite scintillator, using a sapphire window instead of a fiber-optic faceplate for light transport to the photomultiplier, and the all-digital data acquisition system. We present a description of the system with simulations and experimental results that show a position resolution on the alpha detector of 1 mm, a depth resolution using a LaBr 3 detector of 6.2 cm, and an angular resolution of 4.5°. Additionally, we present single-element gamma response measurements for the elements mentioned above together with a comparison to Monte Carlo simulations (MCNP6).

47 OTHER INSTRUMENTATION↗
DOE OSTI2025

Particle-in-cell simulations of burning inertial confinement fusion capsule implosions

Anomalies observed in the neutron spectral shift of high-yield shots at the National Ignition Facility (NIF) suggest the presence of suprathermal ions [E. P. Hartouni et al., Nat. Phys. 19, 72 (2023)], implying that kinetic effects play a significant role in burning inertial confinement fusion (ICF) plasmas. Furthermore, recent measurements of reaction-in-flight (RIF) neutrons offer a direct probe of the stopping power in the burning fuel region of high-energy alpha particles and up-scattered fuel ions. We have developed the particle-in-cell code PICNIC, an exactly energy-conserving particle-in-cell Monte-Carlo collision (PIC-MCC) code to simulate the burn stage in ICF. We present results from 1D spherical simulations of NIF shot N210808, which was the first to exceed the Lawson criterion for laser fusion. We find that the suprathermal ions generated by large-angle Rutherford and nuclear elastic scattering (NES) with fusion alphas produce an alpha knock-on neutron (AKN) signal consistent with the extent and relative yield of the AKN spectrum identified in ignition experiments at the NIF. Furthermore, we also find that the inclusion of large-angle scattering physics does not explain the anomalously large spectral shift observed in the experiment.

High-energy-density plasmas↗
DOE OSTI2021

Diamond channel-cut crystals for high-heat-load beam-multiplexing narrow-band X-ray monochromators

Next-generation high-brilliance X-ray photon sources call for new X-ray optics. Here we demonstrate the possibility of using monolithic diamond channel-cut crystals as high-heat-load beam-multiplexing narrow-band mechanically stable X-ray monochromators with high-power X-ray beams at cutting-edge high-repetition-rate X-ray free-electron laser (XFEL) facilities. The diamond channel-cut crystals fabricated and characterized in these studies are designed as two-bounce Bragg reflection monochromators directing 14.4 or 12.4 keV X-rays within a 15 meV bandwidth to 57 Fe or 45 Sc nuclear resonant scattering experiments, respectively. The crystal design allows out-of-band X-rays transmitted with minimal losses to alternative simultaneous experiments. Only ≲2% of the incident ∼100 W X-ray beam is absorbed in the 50 µm-thick first diamond crystal reflector, ensuring that the monochromator crystal is highly stable. Other X-ray optics applications of diamond channel-cut crystals are anticipated.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗