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DOE OSTI2023

Kernel Buffer Volume Fraction Margin of the AGR Designed Fuel Particle

Modeling results used to assess the fuel performance of the TRISO-coated fuel particles as a function of kernel/buffer volume fraction include SiC tangential stress, formation of the buffer/IPyC gap, particle temperature profile, internal particle pressure, fission gas released from the kernel, probability of fuel particle failure, and fission product diffusion. These results were evaluated at two burnup levels and irradiation temperatures to bound expected steady-state irradiation conditions. In general, increasing the kernel/buffer volume fraction increases the SiC stress and subsequently the failure probability of a fuel particle when compared to the AGR designed particle. There was little impact on the fission product diffusion through the particle as the kernel/buffer volume fraction increased.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2016

Correlations between jets and charged particles in PbPb and pp collisions at $ \sqrt{s_{\mathrm{NN}}}=2.76 $ TeV

The quark-gluon plasma is studied via medium-induced changes to correlations between jets and charged particles in PbPb collisions compared to pp reference data. This analysis uses data sets from PbPb and pp collisions with integrated luminosities of 166 μb –1 and 5.3 pb –1 , respectively, collected at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV. The angular distributions of charged particles are studied as a function of relative pseudorapidity (Δη) and relative azimuthal angle (ΔΦ) with respect to reconstructed jet directions. Charged particles are correlated with all jets with transverse momentum ($p_{\mathrm{T}}$) above 120 GeV, and with the leading and subleading jets (the highest and second-highest in $p_{\mathrm{T}}$, respectively) in a selection of back-to-back dijet events. Modifications in PbPb data relative to pp reference data are characterized as a function of PbPb collision centrality and charged particle $p_{\mathrm{T}}$. A centrality-dependent excess of low-$p_{\mathrm{T}}$ particles is present for all jets studied, and is most pronounced in the most central events. This excess of low-$p_{\mathrm{T}}$ particles follows a Gaussian-like distribution around the jet axis, and extends to large relative angles of Δη ≈ 1 and ΔΦ ≈ 1.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2015

The Influence of Constitutional Supercooling on the Distribution of Te-particles in Melt-Grown CZT

A section of a vertical gradient freeze Cd 0.9 Zn 0.1 Te boule approximately 2100-mm 3 with a planar area of 300-mm 2 was prepared and examined using transmitted IR microscopy at various magnifications to determine the three-dimensional spatial and size distributions of Te-particles over large longitudinal and radial length scales. Te-particle density distributions were determined as a function of longitudinal and radial positions in these strips and exhibited a multi-modal lognormal size density distribution that indicated a slight preference for increasing size with longitudinal growth time, while showing a pronounced cellular network structure. Higher magnification images revealed a typical Rayleigh-instability pearl string morphology with large and small satellite droplets. This study includes solidification experiments in small crucibles of 30:70 mixtures of Cd:Te performed over a wide range of cooling rates that clearly demonstrated a growth instability with Te-particle capture that is suggested to be responsible for one of the peaks in the size distribution using size discrimination visualization. The results are discussed with regard to a manifold Te-particle genesis history as Te-particle direct capture from melt-solid growth instabilities due to constitutional supercooling and as Te-particle formation from the breakup of Te-ribbons via a Rayleigh-Plateau instability.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2023

Characterization of solid particle candidates for application in thermal energy storage and concentrating solar power systems

Thermal energy storage (TES) enables concentrating solar power to remain competitive in the renewable energy mix by firming up intermittent solar resource and providing grid services such as load shifting. Free from siting constraints, stand-alone TES systems show promise as a low-cost alternative to traditional pumped-storage hydropower or compressed air energy storage. At the core of all TES technologies is a storage medium, the selection of which governs many aspects of system design and operation. Although the majority of commercial installations utilize molten salts, solid particles can demonstrate stability over wider temperature ranges. This amounts to increased energy storage densities and corresponding reductions in system cost which is essential in achieving low-cost energy storage. In this work, eight solid particle candidates are systematically identified and screened for application in a specific particle-TES system. The five most promising candidates (CARBO CP and HSP, calcined flint clay (CFC), brown fused alumina (BFA), and silica sand) are further characterized by size and morphology for fluidization suitability, flowability for particle transport, and thermal stability. Calcined flint clay and brown fused alumina are eventually down-selected due to thermal instability at the target operational temperature of 1200 °C. Although the physical characteristics of CARBO outperform silica sand in all categories examined, the marginal performance gains are considered insufficient to justify the additional media cost so silica sand is selected as the leading candidate. Within the silica sand (α-quartz) space, the high end of Geldart Group B particles is identified to satisfy the target fluidization regime for the application of interest without compromising particle flowability. Here, in focused testing, Silica 460 is shown to exhibit sufficient stability through long-duration (500-hour) thermal and cyclic testing (1200 °C), 10-hour testing at 1400 °C, and in contact with candidate refractory containment materials. Finally, an average heat capacity of 1.1 J/g∙ °C is measured over 300-1200 °C with a quartz inversion enthalpy (ΔH α-β ) of 10.7J/g.

14 SOLAR ENERGY↗

DOE OSTI2011

Kinetics of illuminated complex plasmas considering Mie scattering by spherical dust particles with a size distribution

In this paper Mie scattering of light by dust particles having Mathis, Rumpl, and Nordsieek power law distribution of size has been incorporated in the formulation of the kinetics of an illuminated complex plasma which takes into account the ionization of neutral atoms by an external agency, ion-electron recombination, photoemission of electrons by the dust particles, and accretion of electrons and ions on the surface of the particles; the number and energy balance of the constituent species has also been taken into account. An interesting conclusion is that unlike the usual case (when Mie scattering is neglected) the charge on a particle is not proportional to the radius and that for certain sets of parameters the smaller particles are negatively charged while the larger particles, carry positive charge.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2011

Wave-particle interactions in rotating mirrors

Wave-particle interactions in ExB rotating plasmas feature an unusual effect: particles are diffused by waves in both potential energy and kinetic energy. This wave-particle interaction generalizes the alpha channeling effect, in which radio frequency waves are used to remove alpha particles collisionlessly at low energy. In rotating plasmas, the alpha particles may be removed at low energy through the loss cone, and the energy lost may be transferred to the radial electric field. This eliminates the need for electrodes in the mirror throat, which have presented serious technical issues in past rotating plasma devices. A particularly simple way to achieve this effect is to use a high azimuthal mode number perturbation on the magnetic field. Rotation can also be sustained by waves in plasmas without a kinetic energy source. This type of wave has been considered for plasma centrifuges used for isotope separation. Energy may also be transferred from the electric field to particles or waves, which may be useful for ion heating and energy generation.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2011

On Influence of Neutrals on Dust Particle Charging in Complex Plasmas in the Presence of Electromagnetic Radiation

Effects associated with neutral component of complex (dusty) ionospheric plasmas which affect dust particle charging are studied. Microscopic ion currents on dust particles with taking into account ion-neutral interaction are presented. Calculations are performed both for the case of negative charges of dust particles, when the influence of Solar radiation on dust particle charging processes is negligible, and for the case of positive charges which is realized in the presence of sufficiently intensive UV or X-ray radiation. We also carry out investigation of the electron heating due to the photoelectric effect. We show that the efficiency of electron heating depends on the density of neutral component of the plasma. As result, we determine altitudes where the influence of the neutral plasma component on dust particle charging processes as well as the electron heating effect are significant and should be taken into account under consideration of the ionospheric complex plasmas. In particular, we show that the effects considered could be important for the description of noctilucent clouds, polar mesosphere summer echoes, and some other physical phenomena associated with dust particles in the ionosphere.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2016

Coupled electrostatic and material surface stresses yield anomalous particle interactions and deformation

Like-charges repel, and opposite charges attract. This fundamental tenet is a result of Coulomb's law. However, the electrostatic interactions between dielectric particles remain topical due to observations of like-charged particle attraction and the self-assembly of colloidal systems. Here, we show, using both an approximate description and an exact solution of Maxwell's equations, that nonlinear charged particle forces result even for linear material systems and can be responsible for anomalous electrostatic interactions such as like-charged particle attraction and oppositely charged particle repulsion. Furthermore, these electrostatic interactions and the deformation of such particles have fundamental implications for our understanding of macroscopic electrodynamics.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2022

Quasilinear theory of general electromagnetic fluctuations including discrete particle effects for magnetized plasmas: General analysis

The general quasilinear Fokker–Planck kinetic equation for the gyrophase-averaged plasma particle distribution functions in magnetized plasmas is derived, making no restrictions on the energy of the particles and on the frequency of the electromagnetic fluctuations and avoiding the often made Coulomb approximation of the electromagnetic interactions. Here, the inclusion of discrete particle effects breaks the dichotomy of nonlinear kinetic plasma theory divided into the test particle and the test fluctuation approximation because it provides expression of both the non-collective and collective electromagnetic fluctuation spectra in terms of the plasma particle distribution functions. Within the validity of the quasilinear approach, the resulting full quasilinear transport equation can be regarded as a determining nonlinear equation for the time evolution of the plasma particle distribution functions.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2011

An imaging co-axial tube electrodynamic trap for manipulation of charged particles

A tubular particle trapping device was designed and fabricated using two co-axial electrically conductive tubes with diameters of 5 mm and 7 mm, respectively. The device was integrated with an imaging camera and optical fiber bundle for real time monitoring of trapped particle motion. Charged microparticles of 3 to 50 m diameter can be suspended in air at ambient pressure using the device utilizing a quadrupole potential with an alternating voltage of amplitude 300 V to 750 V and frequency of 30 Hz to 140 Hz. Controlled trapping of a single particle or multiple particles can be achieved by tuning the voltage amplitude. The particle remained trapped when the entire assembly was translated or rotated. The device can be used as a manipulator for charged particle transport and repositioning.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2010

Optomechanical approach to cooling of small polarizable particles in a strongly pumped ring cavity

Cavity cooling of an atom works best on a cyclic optical transition in the strong coupling regime near resonance, where small-cavity photon numbers suffice for trapping and cooling. A straightforward application to the cooling of the translational motion of other polarizable particles without sharply defined two-level transitions (such as molecules) fails as optical pumping transfers the particle into uncoupled states. An alternative operation in the far-off-resonant regime generates only very slow cooling due to the reduced field-particle coupling. We suggest one can overcome this by using a strongly driven ring cavity operated in the sideband cooling regime. The dynamics can be mapped onto the optomechanics setup with a movable mirror and allows one to take advantage of a collectively enhanced field-particle coupling by large photon numbers. A linearized analytical treatment confirmed by full numerical quantum simulations predicts fast cooling despite the off-resonant small single-particle-single-photon coupling. Even ground-state translational cooling (in the external potential) can be obtained by tuning the cavity field close to the Anti-stokes sideband for sufficiently high trapping frequency. Numerical simulations show quantum jumps of the particle between the lowest two trapping levels, which can be directly and continuously monitored via scattered light intensity detection.

74 ATOMIC AND MOLECULAR PHYSICS↗

DOE OSTI2012

Integration of Heat Transfer, Stress, and Particle Trajectory Simulation

Calabazas Creek Research, Inc. developed and currently markets Beam Optics Analyzer (BOA) in the United States and abroad. BOA is a 3D, charged particle optics code that solves the electric and magnetic fields with and without the presence of particles. It includes automatic and adaptive meshing to resolve spatial scales ranging from a few millimeters to meters. It is fully integrated with CAD packages, such as SolidWorks, allowing seamless geometry updates. The code includes iterative procedures for optimization, including a fully functional, graphical user interface. Recently, time dependent, particle in cell capability was added, pushing particles synchronically under quasistatic electromagnetic fields to obtain particle bunching under RF conditions. A heat transfer solver was added during this Phase I program. Completed tasks include: (1) Added a 3D finite element heat transfer solver with adaptivity; (2) Determined the accuracy of the linear heat transfer field solver to provide the basis for development of higher order solvers in Phase II; (3) Provided more accurate and smoother power density fields; and (4) Defined the geometry using the same CAD model, while maintaining different meshes, and interfacing the power density field between the particle simulator and heat transfer solvers. These objectives were achieved using modern programming techniques and algorithms. All programming was in C++ and parallelization in OpenMP, utilizing state-of-the-art multi-core technology. Both x86 and x64 versions are supported. The GUI design and implementation used Microsoft Foundation Class.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2011

PLASMA WAKE EXCITATION BY LASERS OR PARTICLE BEAMS

Plasma accelerators may be driven by the ponderomotive force of an intense laser or the space-charge force of a charged particle beam. Plasma wake excitation driven by lasers or particle beams is examined, and the implications of the different physical excitation mechanisms for accelerator design are discussed. Plasma-based accelerators have attracted considerable attention owing to the ultrahigh field gradients sustainable in a plasma wave, enabling compact accelerators. These relativistic plasma waves are excited by displacing electrons in a neutral plasma. Two basic mechanisms for excitation of plasma waves are actively being researched: (i) excitation by the nonlinear ponderomotive force (radiation pressure) of an intense laser or (ii) excitation by the space-charge force of a dense charged particle beam. There has been significant recent experimental success using lasers and particle beam drivers for plasma acceleration. In particular, for laser-plasma accelerators (LPAs), the demonstration at LBNL in 2006 of high-quality, 1 GeV electron beams produced in approximately 3 cm plasma using a 40 TW laser. In 2007, for beam-driven plasma accelerators, or plasma-wakefield accelerators (PWFAs), the energy doubling over a meter to 42 GeV of a fraction of beam electrons on the tail of an electron beam by the plasma wave excited by the head was demonstrated at SLAC. These experimental successes have resulted in further interest in the development of plasma-based acceleration as a basis for a linear collider, and preliminary collider designs using laser drivers and beam drivers are being developed. The different physical mechanisms of plasma wave excitation, as well as the typical characteristics of the drivers, have implications for accelerator design. In the following, we identify the similarities and differences between wave excitation by lasers and particle beams. The field structure of the plasma wave driven by lasers or particle beams is discussed, as well as the regimes of operation (linear and nonlinear wave). Limitations owing to driver emittance are also discussed.

43 PARTICLE ACCELERATORS↗

DOE OSTI2016

Particle Resuspension Simulation Capability to Substantiate DOE-HDBK-3010 Data

The data provided in the U.S. Department of Energy (DOE) Handbook, DOE-HDBK-3010 provides data such as airborne release fractions and respirable fractions which are widely used in safety analysis and facility design. These fractions are often used as conservative bounds, despite the fact that the original data may have been obtained at a different scale or in a different configuration than the end application. The use of computational techniques to augment these data can be used to extend laboratory-scale data applicability to facility-scale decisions. Our prior report described an approach using Sandia National Laboratories (SNL) computer codes to simulate particle releases from various accident scenarios. The relevant physics controlling the particle resuspension phenomena can be highly problem-dependent. They can include surface tension for particles or surfaces with liquid present, van der Waals forces for small particles, electrostatic forces for charged particles, and mechanical interactions with surface features larger than the particles sizes. The complexity of this phenomenon and recent developments have been described in a recent review by Henry and Minier. (authors)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2010

Recombination algorithms and jet substructure: Pruning as a tool for heavy particle searches

We discuss jet substructure in recombination algorithms for QCD jets and single jets from heavy particle decays. We demonstrate that the jet algorithm can introduce significant systematic effects into the substructure. By characterizing these systematic effects and the substructure from QCD, splash-in, and heavy particle decays, we identify a technique, pruning, to better identify heavy particle decays into single jets and distinguish them from QCD jets. Pruning removes protojets typical of soft, wide-angle radiation, improves the mass resolution of jets reconstructing heavy particle decays, and decreases the QCD background to these decays. We show that pruning provides significant improvements over unpruned jets in identifying top quarks and W bosons and separating them from a QCD background, and may be useful in a search for heavy particles.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2014

Ice Nucleation of Bare and Sulfuric Acid-coated Mineral Dust Particles and Implication for Cloud Properties

Ice nucleation properties of different dust species coated with soluble material are not well understood. We determined the ice nucleation ability of bare and sulfuric acid coated mineral dust particles as a function of temperature (-25 to -35 deg C) and relative humidity with respect to water (RHw). Five different mineral dust species: Arizona test dust (ATD), illite, montmorillonite, quartz and kaolinite were dry dispersed and size-selected at 150 nm and exposed to sulfuric acid vapors in the coating apparatus. The condensed sulfuric acid soluble mass fraction per particle was estimated from the cloud condensation nuclei activated fraction measurements. The fraction of dust particles nucleating ice at various temperatures and RHw was determined using a compact ice chamber. In water-subsaturated conditions, compared to bare dust particles, we found that only coated ATD particles showed suppression of ice nucleation ability while other four dust species did not showed the effect of coating on the fraction of particles nucleating ice. The results suggest that interactions between the dust surface and sulfuric acid vapor are important, such that interactions may or may not modify the surface via chemical reactions with sulfuric acid. At water-supersaturated conditions we did not observed the effect of coating, i.e. the bare and coated dust particles had similar ice nucleation behavior.

Kulkarni, Gourihar R.↗

DOE OSTI2013

Chemical Characterization of Individual Particles and Residuals of Cloud Droplets and Ice Crystals Collected On Board Research Aircraft in the ISDAC 2008 Study

Although it has been shown that size of atmospheric particles has a direct correlation with their ability to act as cloud droplet and ice nuclei, the influence of composition of freshly emitted and aged particles in nucleation processes is poorly understood. In this work we combine data from field measurements of ice nucleation with chemical imaging of the sampled particles to link aerosol composition with ice nucleation ability. Field measurements and sampling were conducted during the Indirect and Semidirect Aerosols Campaign (ISDAC) over Barrow, Alaska, in the springtime of 2008. In-situ ice nucleation measurements were conducted using a Continuous Flow Diffusion Chamber (CFDC). Measured number concentrations of ice nuclei (IN) varied from frequent values of 0.01 per liter to more than 10 per liter. Residuals of airborne droplets and ice crystals were collected through a counterflow virtual impactor (CVI). The compositions of individual atmospheric particles and the residuals were studied using Computer Controlled Scanning Electron Microscopy with Energy Dispersive X-ray analysis (CCSEM/EDX) and Scanning Transmission X-ray Microscopy coupled with Near Edge X-ray Absorption Fine Structure spectroscopy (STXM/NEXAFS). Chemical analysis of cloud particle residuals collected during an episode of high ice nucleation suggests that both size and composition may influence aerosol's ability to act as IN. The STXM/NEXAFS chemical composition maps of individual residuals have characteristic structures of either inorganic or black carbon cores coated by organic materials. In a separate flight, particle samples from a biomass burning plume were collected. Although it has previously been suggested that episodes of biomass burning contribute to increased numbers of highly effective ice nuclei, in this episode we observed that only a small fraction were effective ice nuclei. Most of the particles from the biomass plume episode were smaller in size and were composed of homogeneous organic material without identifiable cores.

Environmental Molecular Sciences Laboratory↗

DOE OSTI2019

X-ray Phase Contrast Imaging of the Impact of a Single HMX Particle in a Polymeric Matrix

A thorough understanding of the mechanisms by which high explosives (HEs) are shock initiated, especially at the particle scale, is still in demand. One approach to explain shock initiation phenomenon is hot spot theory, which suggests that distributed energy in energetic material is localized due to shock or impact to generate the high temperatures for ignition. Here, we focus on the impact response of a HE polycrystalline particle, specifically HMX, in a polymer matrix. This represents a simplified analog of a traditional polymer-bonded explosive (PBX) formulation. A light gas gun, together with high-speed x-ray phase contrast imaging (PCI), was used to study the impact response of a single particle of production-grade HMX in a Sylgard-184® matrix. The high-speed x-ray PCI allows for real-time visualization of HE particle behavior. The experiments revealed that, at impact velocities of ~ 200 m s -1 , the energetic particle was cracked and crushed. When the impact velocity was increased to 445 m s -1 , a significant volume expansion of the particle was observed. This volume expansion is considered to be the result of chemical reaction within the HE particle.

42 ENGINEERING↗