Physics Commons^™

Petawatt-Laser-Driven Wakefield Acceleration Of Electrons To 2 Gev In 10^{17} Cm^{-3} Plasma, Xiaoming Wang, Rafal B. Zgadzaj, Neil Fazel, Sunghwan A. Yi, X. Zhang, Watson Henderson, Yen-Yu Zhang, Rick Korzekwa, Hai-En Tsai, C.-H. Pai, Zhengyan Li, Hernan Quevedo, Gilliss Dyer, Erhard W. Gaul, Mikael Martinez, Aaron Bernstein, Ted Borger, M. Spinks, M. Donovan, Serguei Y. Kalmykov, Vladimir N. Khudik, Gennady Shvets, Todd Ditmire, Michael C. Downer

Serge Youri Kalmykov

Electron self-injection into a laser-plasma accelerator (LPA) driven by the Texas Petawatt (TPW) laser is reported at plasma densities 1.7 - 6.2 x 10^{17} cm^{-3}. Energy and charge of the electron beam, ranging from 0.5 GeV to 2 GeV and tens to hundreds of pC, respectively, depended strongly on laser beam quality and plasma density. Angular beam divergence was consistently around 0.5 mrad (FWHM), while shot-to-shot pointing fluctuations were limited to ±1.4 mrad rms. Betatron x-rays with tens of keV photon energy are also clearly observed.

Sub-Millimeter-Scale, 100-Mev-Class Quasi-Monoenergetic Laser Plasma Accelerator Based On All-Optical Control Of Dark Current In The Blowout Regime, Serguei Y. Kalmykov, Xavier Davoine, Bradley A. Shadwick

Serge Youri Kalmykov

It is demonstrated that by negatively chirping the frequency of a 20-fs, 15-TW driving laser pulse with an ultrabroad bandwidth (corresponding to a sub-2-cycle transform-limited duration it is possible to prevent early compression of the pulse into an optical shock, thus reducing expansion of the accelerating plasma bucket (electron density "bubble") and delaying dephasing of self-injected and accelerated electrons. These features help suppress unwanted continuous self-injection (dark current) in the blowout regime, making possible to use the entire dephasing length to generate low-background, quasi-monoenergetic 200-MeV-scale electron beams from sub-mm-length, dense plasmas (n_{e0} = 1.3 x 10^{19} cm^{−3}).

Oscillator Strength Measurements Of The 5s6s 1s0→5snp 1p1 Rydberg Transitions Of Strontium, S. U. Haq, M. A. Kalyar, M. Rafiq, R. Ali, Naveed K. Piracha, M. A. Baig

Naveed K. Piracha

We report the experimentally determined oscillator strengths for the 5s6s 1S0→5snp 1P1 Rydberg transitions of strontium using two-step excitation in conjunction with a thermionic diode ion detector. The absolute photoionization cross section from the 5s6s 1S0 excited state has been determined by adjusting the polarization vector of the ionizing laser beam parallel, perpendicular, and at the magic angle with respect to that of the exciting dye laser. The measured absolute value of the photoionization cross section 0.9±0.2 Mb at the 5s threshold is used to extract the f values of the 5s6s 1S0→5snp 1P1 (26≤n≤73) Rydberg transitions. The oscillator strength …

Toward High-Performance Nanostructured Thermoelectric Materials: The Progress Of Bottom-Up Solution Chemistry Approaches, Yixin Zhao, Jeffrey S. Dyck, Clemens Burda

Jeffrey Dyck

Significant research effort has recently gone into the synthesis of thermoelectric nanomaterials through different chemical approaches since nanomaterials chemistry became a promising strategy for improving thermoelectric performance. Different thermoelectric nanocrystals, especially PbTe, Bi2Te3 and CoSb3, with various compositions and morphologies have been successfully prepared by solvo/hydrothermal, electrochemical, and ligand-based synthesis methods. Such nanoscale materials show not only substantial reduction in thermal conductivity due to increased phonon scattering at nanoscale grain boundaries and lower densities of phonon states but possibly also an enhancement in thermopower due to electronic quantum size effects. More recently, the notoriously low power factors of thermoelectric nanomaterials …

Structure Inhomogeneities, Shallow Defects, And Charge Transport In The Series Of Thermoelectric Materials K2bi8−Xsbxse13, Jeffrey S. Dyck, T. Kyratski, E. Hatzikraniotis, K. M. Paraskevopoulos, C. D. Malliakas, C. Uher, M. G. Kanatzidis

Jeffrey Dyck

The charge transport properties of the low-dimensional thermoelectric materials K2Bi8-xSbxSe13 (02Bi8-xSbxSe13 was analyzed on the basis of the classical semiconductor theory and discussed in the context of recent band calculations. The results suggest that the K2Bi8-xSbxSe13 materials possess coexisting domains with semimetallic and semiconducting characters whose ratio is influenced by the value of x and by local defects. The extent and relative distribution of these domains control the charge transport properties. Electron diffraction experiments performed on samples of K2Bi8-xSbxSe13 with x=1.6 show evidence for such domains by indicating regions with long range ordering of K+/Bi3+ atoms and regions with increased …

Data Curation Is For Everyone! The Case For Master's And Baccalaureate Institutional Engagement With Data Curation, Yasmeen Shorish

Yasmeen Shorish

This article describes the fundamental challenges to data curation, how these challenges may be compounded for smaller institutions, and how data management is an essential and manageable component of data curation. Data curation is often discussed within the confines of large, research universities. As a result, master’s and baccalaureate institutions may be left with the impression that they cannot engage with data curation. However, by proactively engaging with faculty, libraries of all sizes can build closer relationships and help educate faculty on data documentation and organization best practices. Experiences from one master’s comprehensive institution as it engages with data management …

A Comparison Of Short-Range Molecular Order In Bent-Core And Rod-Like Nematic Liquid Crystals, S. Chakraborty, J. T. Gleeson, Antal Jákli, Samuel Sprunt

Antal Jakli

Thermotropic liquid crystals exhibit strongly temperature-dependent positional correlations among molecules in the nematic phase above the transition to a smectic-A or C phase. However, even in the absence of a lower temperature smectic phase, nematics composed of reduced symmetry molecules (bent-core mesogens, for example) reveal small angle X-ray scattering (SAXS) patterns with features similar to those associated with pretransitional smectic order. We report on a quantitative analysis and comparison of two-dimensional SAXS data on a bent-core nematic compound (lacking a smectic phase) and a rod-like nematic (exhibiting a nematic to smectic-C transition). This analysis demonstrates that a nanostructure based on …

Defect Structure Of Sb2−Xcrxte3 Single Crystals, Jeffrey Dyck, J. HoráK, P. C. Quayle, Č. DrašAr, P. LošT’ÁK, C. Uher

Jeffrey Dyck

Single crystals of Sb2Te3 doped with Cr (cCr=0–6×1020 cm-3) were prepared by the Bridgman method. The measurements of the Hall coefficient reveal a nonmonotonous dependence of hole concentrations on the Cr content in the crystal. The hole concentration decreases at low content of Cr, while at higher content of Cr it increases again. However, according to magnetic measurements, Cr atoms enter the structure and form uncharged substitutional defects CrSb×, which cannot affect the free carrier concentration directly. The observed dependence can be elucidated by means of a point defect model. The model is based on an assumption that defect structure …

Viscoelasticity, Dielectric Anisotropy, And Birefringence In The Nematic Phase Of Three Four-Ring Bent-Core Liquid Crystals With An L-Shaped Molecular Frame, Nejmettin Acvi, Volodymyr Borshch, Dipika Debnath Sarkar, Rahul Deb, Gude Venkatesh, Taras Turiv, Sergij V. Shiyanovskii, Nandiraju V. S. Rao, Oleg Lavrentovich

Oleg Lavrentovich

Molecular shape is an important factor in determining the material properties of thermotropic liquid crystals (LCs). We synthesized and investigated several LC compounds formed by asymmetrically bent molecules with a rigid four-ring core in the shape of the letter 'L'. We measured the temperature dependencies of dielectric permittivities, birefringence, splay K-1 and bend K-3 elastic constants, splay viscosity eta(splay) and flow viscosities eta(parallel to) and eta(perpendicular to). The bend-splay anisotropy delta K-31 - K-3 - K-1 is negative, similar to the case of nematic LCs formed by symmetrically bent molecules of V-shape. The dielectric anisotropy Delta epsilon and birefringence are …

Quantum Dots As Liquid Crystal Dopants, Javad Mirzaei, Mitya Reznikov, Torsten Hegmann

Torsten Hegmann

Liquid crystal nanoscience, a field exploring the mutually beneficial combination of the unique properties of nanoscale materials and fluid, yet ordered liquid crystalline phases, is increasingly focusing on semiconductor quantum dots. In one major research thrust, the anisotropic properties of the liquid crystal host are sought to facilitate the assembly of quantum dots into arrays, in another, both size-and shape-dependent optical and electronic properties of quantum dots are used to manipulate optical, electro-optical and alignment properties of liquid crystalline materials. This feature article reviews recent accomplishments and new insights in this fascinating area of soft matter nanocomposites including work from …

Electron Self-Injection Into An Evolving Plasma Bubble: Quasi-Monoenergetic Laser-Plasma Acceleration In The Blowout Regime, Serguei Y. Kalmykov, A. Beck, S. A. Yi, V. N. Khudik, Michael C. Downer, E. Lefebvre, Bradley Allan Shadwick, Donald Umstadter

Serge Youri Kalmykov

An electron density bubble driven in a rarefied uniform plasma by a slowly evolving laser pulse goes through periods of adiabatically slow expansions and contractions. Bubble expansion causes robust self-injection of initially quiescent plasma electrons, whereas stabilization and contraction terminate self-injection thus limiting injected charge; concomitant phase space rotation reduces the bunch energy spread. In regimes relevant to experiments with hundred terawatt- to petawatt-class lasers, bubble dynamics and, hence, the self-injection process are governed primarily by the driver evolution. Collective transverse fields of the trapped electron bunch reduce the accelerating gradient and slow down phase space rotation. Bubble expansion followed …

Negative Index Metamaterials Based On Metal-Dielectric Nanocomposites For Imaging Applications, L. Menon, W. T. Lu, A. L. Friedman, S. P. Bennett, D. Heiman, S. Sridhar

Srinivas Sridhar

Negative index metamaterials are demonstrated based on metal-dielectric nanocomposites prepared using a versatile bottom-up nanofabrication approach. The method involves the incorporation of vertically aligned metal nanowires such as Au and Ag inside dielectric aluminum oxide nanotemplates. Optical absorbance measurements show resonance peaks corresponding to the transverse and longitudinal surface plasmon modes. A quantitative model based on effective medium theory is in excellent agreement with experimental data, and points to specific composite configurations and wavelength regimes where such structures can have applications as negative refraction media for imaging.

Possible Room-Temperature Ferromagnetism In Hydrogenated Carbon Nanotubes, Adam L. Friedman, Hyunkyung Chun, Yung Joon Jung, Don Heiman, Evan R. Glaser, Latika Menon

Yung Joon Jung

We find that ferromagnetism can be induced in carbon nanotubes (CNTs) by introducing hydrogen. Multiwalled CNTs grown inside porous alumina templates contain a large density of defects resulting in significant hydrogen uptake when annealed at high temperatures. This hydrogen incorporation produces H-complex and adatom magnetism which generates a sizable ferromagnetic moment and a Curie temperature near TC=1000  K. We studied the conditions for the incorporation of hydrogen, the temperature-dependent magnetic behavior, and the dependence of the ferromagnetism on the size of the nanotubes.

Possible Room-Temperature Ferromagnetism In Hydrogenated Carbon Nanotubes, Adam L. Friedman, Hyunkyung Chun, Yung Joon Jung, Don Heiman, Evan R. Glaser, Latika Menon

Donald Heiman

We find that ferromagnetism can be induced in carbon nanotubes (CNTs) by introducing hydrogen. Multiwalled CNTs grown inside porous alumina templates contain a large density of defects resulting in significant hydrogen uptake when annealed at high temperatures. This hydrogen incorporation produces H-complex and adatom magnetism which generates a sizable ferromagnetic moment and a Curie temperature near TC=1000  K. We studied the conditions for the incorporation of hydrogen, the temperature-dependent magnetic behavior, and the dependence of the ferromagnetism on the size of the nanotubes.

Negative Index Metamaterials Based On Metal-Dielectric Nanocomposites For Imaging Applications, L. Menon, W. T. Lu, A. L. Friedman, S. P. Bennett, D. Heiman, S. Sridhar

Donald Heiman

Negative index metamaterials are demonstrated based on metal-dielectric nanocomposites prepared using a versatile bottom-up nanofabrication approach. The method involves the incorporation of vertically aligned metal nanowires such as Au and Ag inside dielectric aluminum oxide nanotemplates. Optical absorbance measurements show resonance peaks corresponding to the transverse and longitudinal surface plasmon modes. A quantitative model based on effective medium theory is in excellent agreement with experimental data, and points to specific composite configurations and wavelength regimes where such structures can have applications as negative refraction media for imaging.

Negative Index Metamaterials Based On Metal-Dielectric Nanocomposites For Imaging Applications, L. Menon, W. T. Lu, A. L. Friedman, S. P. Bennett, D. Heiman, S. Sridhar

Latika Menon

Negative index metamaterials are demonstrated based on metal-dielectric nanocomposites prepared using a versatile bottom-up nanofabrication approach. The method involves the incorporation of vertically aligned metal nanowires such as Au and Ag inside dielectric aluminum oxide nanotemplates. Optical absorbance measurements show resonance peaks corresponding to the transverse and longitudinal surface plasmon modes. A quantitative model based on effective medium theory is in excellent agreement with experimental data, and points to specific composite configurations and wavelength regimes where such structures can have applications as negative refraction media for imaging.

Super-Resolution Imaging Using A Three-Dimensional Metamaterials Nanolens, B. D. F. Casse, W. T. Lu, Y. J. Huang, E. Gultepe, L. Menon, S. Sridhar

Latika Menon

Super-resolution imaging beyond Abbe's diffraction limit can be achieved by utilizing an optical medium or "metamaterial" that can either amplify or transport the decaying near-field evanescent waves that carry subwavelength features of objects. Earlier approaches at optical frequencies mostly utilized the amplification of evanescent waves in thin metallic films or metal-dielectric multilayers, but were restricted to very small thicknesses (⪡λ, wavelength) and accordingly short object-image distances, due to losses in the material. Here, we present an experimental demonstration of super-resolution imaging by a low-loss three-dimensional metamaterial nanolens consisting of aligned gold nanowires embedded in a porous alumina matrix. This composite …

Enhanced Optical Anderson Localization Effects In Modulated Bloch Lattices, Ramy El-Ganainy, Mohammad-Ali Miri, Demetrios N. Christodoulides

Ramy El-Ganainy

We study Anderson localization dynamics in periodically modulated optical Bloch arrays. Using an effective model, we show that, in such arrangements, even a weak disorder may play an important role and can lead to enhanced Anderson localization effects.

Application Of The Transfer Matrix Method To Reflection Gratings In Positive And Negative Index Materials, Han Li

Han Li

No abstract provided.

Energy Conservation In Large Buildings, A. Rosenfeld, David W. Hafemeister

Anatoly Rozenfeld

As energy prices rise, newly energy aware designers use better tools and technology to create energy efficient buildings. Thus the U.S. office stock (average age 20 years) uses 250 kBTU/ft2 of resource energy, but the guzzler of 1972 uses 500 (up × 2), and the 1986 ASHRAE standards call for 100–125 (less than 25% of their 1972 ancestors). Surprisingly, the first real cost of these efficient buildings has not risen since 1972. Scaling laws are used to calculate heat gains and losses of buildings to obtain the ΔT(free) which can be as large as 15–30 °C (30–60 °F) for large …

Local Pt Invariance And Supersymmetric Parametric Oscillators, Ramy El-Ganainy, Konstantinos G. Makris, Demetrios N. Christodoulides

Ramy El-Ganainy

We introduce the concept of local parity-time symmetric (PT) invariance in optical waveguides (or cavity) structures. Starting from a Lagrangian formalism, we establish the connection between light dynamics in these configurations and the seemingly different physics of “supersymmetric” parametric oscillators. Using this powerful tool, we present analytical solutions for optical beam propagation in local PT-invariant coupled systems and we show that the intensity tunneling between the two channels critically depends on the initial conditions. For unbalanced inputs, symmetric as well as asymmetric power evolution can be observed depending on the excitation channel. On the other hand, under certain physical conditions, …

Review Of Treatment Of Error In Second Language Student Writing By Dana R. Ferris, Melanie C. González

Melanie González

Magnetism Of Zno Nanoparticles: Dependence On Crystallite Size And Surfactant Coating, Aaron P. Thurber, Geoffrey L. Beausoleil Ii, Gordon A. Alanko, Joshua Anghel, Michael S. Jones, Lydia M. Johnson, Jianhui Zhang, Charles B. Hanna, Dmitri A. Tenne, Alex Punnoose

Charles Hanna

Many recent reports on magnetism in otherwise nonmagnetic oxides have demonstrated that nanoparticle size, surfactant coating, or doping with magnetic ions produces room-temperature ferromagnetism. Specifically, ZnO has been argued to be a room-temperature ferromagnet through all three of these methods in various experimental studies. For this reason, we have prepared a series of 1% Fe doped ZnO nanoparticle samples using a single forced hydrolysis co-precipitation synthesis method from the same precursors, while varying size (6 – 15 nm) and surface coating concentration to study the combined effects of these two parameters. Size was controlled by modifying the water concentration. Surfactant …

Size, Surface Structure, And Doping Effects On Ferromagnetism In Sno2, Gordon A. Alanko, Aaron Thurber, Charles Hanna, Alex Punnoose

Charles Hanna

The effects of crystallite size, surface structure, and dopants on the magnetic properties of semiconducting oxides are highly controversial. In this work, Fe:SnO₂ nanoparticles were prepared by four wet-chemical methods, with Fe concentration varying from 0% to 20%. Analysis confirmed pure single-phase cassiterite with a crystallite size of 2.6 ± 0.1 nm that decreased with increasing. Fe% doped substitutionally as Fe³⁺. Pure SnO₂ showed highly reproducible weak magnetization that varied significantly with synthesis method. Interestingly, doping SnO₂ with Fe < 2.5% produced enhanced magnetic moments in all syntheses; the maximum of 1.6 × 10⁻⁴ µ_B/Fe ion at 0.1% Fe doping was much larger than the 2.6 × …

Workshop Addresses Aviation Community, Jennifer Meehan, Joseph Kunches

Jennifer (Jinni) Meehan

No abstract provided.

The Second Annual Space Weather Community Operations Workshop: Advancing Operations Into The Next Decade, Jennifer Meehan, Jared Fulgham, Kent Tobiska

Jennifer (Jinni) Meehan

No abstract provided.

Search For Biaxiality In A Shape-Persistent Bent-Core Nematic Liquid Crystal, Young-Ki Kim, Madhabi Majumdar, Bohdan I. Senyuk, Luana Tortora, Jens Seltmann, Matthias Lehmann, Antal Jakli, Jim T. Gleeson, Oleg Lavrentovich, Samuel Sprunt

Antal Jakli

Using a range of optical techniques, we have probed the nature of orientational order in a thermotropic bent-core liquid crystal, which features a shape-persistent molecular architecture designed to promote a biaxial nematic phase. In the upper range of the nematic phase (enantiotropic regime), dynamic light scattering reveals strong fluctuations attributable to the biaxial order parameter, in addition to the usual uniaxial director modes. Assuming a Landau-type expansion of the orientational free energy, we estimate the correlation length associated with these fluctuations to be similar to 100 nm. At lower temperatures, and mainly in the monotropic regime of the nematic, we …

Double Layer In Ionic Liquids: Overscreening Versus Crowding, Martin Z. Bazant, Brian D. Storey, Alexei A. Kornyshev

Brian Storey

We develop a simple Landau-Ginzburg-type continuum theory of solvent-free ionic liquids and use it to predict the structure of the electrical double layer. The model captures overscreening from short-range correlations, dominant at small voltages, and steric constraints of finite ion sizes, which prevail at large voltages. Increasing the voltage gradually suppresses overscreening in favor of the crowding of counterions in a condensed inner layer near the electrode. This prediction, the ion profiles, and the capacitance-voltage dependence are consistent with recent computer simulations and experiments on room-temperature ionic liquids, using a correlation length of order the ion size.

Mixture Segregation Within Sonoluminescence Bubbles, Brian D. Storey, Andrew J. Szeri

Brian Storey

This paper concerns a relaxation of the assumption of uniform mixture composition in the interior of sonoluminescence bubbles. Intense temperature and pressure gradients within the bubble drive relative mass diffusion which overwhelms diffusion driven by concentration gradients. This thermal and pressure diffusion results in a robust compositional inhomogeneity in the bubble which lasts several orders of magnitude longer than the temperature peak or light pulse at the main collapse of the bubble. This effect has important consequences for control of sonoluminescence, gas dynamics, sonochemistry, and the physics of light production.

Switch Yard Operation In Thermal Power Plant(Katpp Jhalawar Rajasthan), Radhey Shyam Meena Er.

Radhey Shyam Meena

Switchyard Provides the facilities for switching ,protection & Control of electric power. To handle high Voltage power with proper Safety measures. To isolate the noises coming from the grid with true 50Hz power SWITCH YARD IS IMPORTANT PART IN THERMAL PLANT. IN KALISINDH THERMAL 400KV AND 220KV SWITCH YARD LOCATED.