Experimental Characterization of Electron-Beam-Driven Wakefield Modes in a Dielectric-Woodpile Cartesian Symmetric Structure

NASA Astrophysics Data System (ADS)

Hoang, P. D.; Andonian, G.; Gadjev, I.; Naranjo, B.; Sakai, Y.; Sudar, N.; Williams, O.; Fedurin, M.; Kusche, K.; Swinson, C.; Zhang, P.; Rosenzweig, J. B.

2018-04-01

Photonic structures operating in the terahertz (THz) spectral region enable the essential characteristics of confinement, modal control, and electric field shielding for very high gradient accelerators based on wakefields in dielectrics. We report here an experimental investigation of THz wakefield modes in a three-dimensional photonic woodpile structure. Selective control in exciting or suppressing of wakefield modes with a nonzero transverse wave vector is demonstrated by using drive beams of varying transverse ellipticity. Additionally, we show that the wakefield spectrum is insensitive to the offset position of strongly elliptical beams. These results are consistent with analytic theory and three-dimensional simulations and illustrate a key advantage of wakefield systems with Cartesian symmetry: the suppression of transverse wakes by elliptical beams.

Investigation of Molecular Exchange Using DEXSY with Ultra-High Pulsed Field Gradients

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gratz, Marcel; Galvosas, Petrik

2008-12-05

Diffusion exchange spectroscopy has been employed for the investigation of water exchange between different regions of a cosmetic lotion as well as for the exchange of n-pentane between the inter- and intra-crystalline space in zeolite NaX. We successfully combined this two-dimensional (2D) NMR experiment with methods for the application of ultra-high pulsed field gradients of up to 35 T/m, resulting in observation times and mixing times as short as 2 ms and 2.8 ms, respectively.

Interaction of an ultrarelativistic electron bunch train with a W-band accelerating structure: High power and high gradient

DOE PAGES

Wang, D.; Antipov, S.; Jing, C.; ...

2016-02-05

Electron beam interaction with high frequency structures (beyond microwave regime) has a great impact on future high energy frontier machines. We report on the generation of multimegawatt pulsed rf power at 91 GHz in a planar metallic accelerating structure driven by an ultrarelativistic electron bunch train. This slow-wave wakefield device can also be used for high gradient acceleration of electrons with a stable rf phase and amplitude which are controlled by manipulation of the bunch train. To achieve precise control of the rf pulse properties, a two-beam wakefield interferometry method was developed in which the rf pulse, due to themore » interference of the wakefields from the two bunches, was measured as a function of bunch separation. As a result, measurements of the energy change of a trailing electron bunch as a function of the bunch separation confirmed the interferometry method.« less

High Gradient Accelerator Research

DOE Office of Scientific and Technical Information (OSTI.GOV)

Temkin, Richard

The goal of the MIT program of research on high gradient acceleration is the development of advanced acceleration concepts that lead to a practical and affordable next generation linear collider at the TeV energy level. Other applications, which are more near-term, include accelerators for materials processing; medicine; defense; mining; security; and inspection. The specific goals of the MIT program are: • Pioneering theoretical research on advanced structures for high gradient acceleration, including photonic structures and metamaterial structures; evaluation of the wakefields in these advanced structures • Experimental research to demonstrate the properties of advanced structures both in low-power microwave coldmore » test and high-power, high-gradient test at megawatt power levels • Experimental research on microwave breakdown at high gradient including studies of breakdown phenomena induced by RF electric fields and RF magnetic fields; development of new diagnostics of the breakdown process • Theoretical research on the physics and engineering features of RF vacuum breakdown • Maintaining and improving the Haimson / MIT 17 GHz accelerator, the highest frequency operational accelerator in the world, a unique facility for accelerator research • Providing the Haimson / MIT 17 GHz accelerator facility as a facility for outside users • Active participation in the US DOE program of High Gradient Collaboration, including joint work with SLAC and with Los Alamos National Laboratory; participation of MIT students in research at the national laboratories • Training the next generation of Ph. D. students in the field of accelerator physics.« less

Particle-in-cell simulation of x-ray wakefield acceleration and betatron radiation in nanotubes

DOE PAGES

Zhang, Xiaomei; Tajima, Toshiki; Farinella, Deano; ...

2016-10-18

Though wakefield acceleration in crystal channels has been previously proposed, x-ray wakefield acceleration has only recently become a realistic possibility since the invention of the single-cycled optical laser compression technique. We investigate the acceleration due to a wakefield induced by a coherent, ultrashort x-ray pulse guided by a nanoscale channel inside a solid material. By two-dimensional particle-in-cell computer simulations, we show that an acceleration gradient of TeV/cm is attainable. This is about 3 orders of magnitude stronger than that of the conventional plasma-based wakefield accelerations, which implies the possibility of an extremely compact scheme to attain ultrahigh energies. In additionmore » to particle acceleration, this scheme can also induce the emission of high energy photons at ~O(10–100) MeV. Here, our simulations confirm such high energy photon emissions, which is in contrast with that induced by the optical laser driven wakefield scheme. In addition to this, the significantly improved emittance of the energetic electrons has been discussed.« less

Directional solidification at ultra-high thermal gradient

NASA Technical Reports Server (NTRS)

Flemings, M. C.; Lee, D. S.; Neff, M. A.

1980-01-01

A high gradient controlled solidification (HGC) furnace was designed and operated at gradients up to 1800 C/cm to continuously produce aluminum alloys. Rubber '0' rings for the water cooling chamber were eliminated, while still maintaining water cooling directly onto the solidified metal. An HGC unit for high temperature ferrous alloys was also designed. Successful runs were made with cast iron, at thermal gradients up to 500 C/cm.

Measurement of Transverse Wakefields Induced by a Misaligned Positron Bunch in a Hollow Channel Plasma Accelerator.

PubMed

Lindstrøm, C A; Adli, E; Allen, J M; An, W; Beekman, C; Clarke, C I; Clayton, C E; Corde, S; Doche, A; Frederico, J; Gessner, S J; Green, S Z; Hogan, M J; Joshi, C; Litos, M; Lu, W; Marsh, K A; Mori, W B; O'Shea, B D; Vafaei-Najafabadi, N; Yakimenko, V

2018-03-23

Hollow channel plasma wakefield acceleration is a proposed method to provide high acceleration gradients for electrons and positrons alike: a key to future lepton colliders. However, beams which are misaligned from the channel axis induce strong transverse wakefields, deflecting beams and reducing the collider luminosity. This undesirable consequence sets a tight constraint on the alignment accuracy of the beam propagating through the channel. Direct measurements of beam misalignment-induced transverse wakefields are therefore essential for designing mitigation strategies. We present the first quantitative measurements of transverse wakefields in a hollow plasma channel, induced by an off-axis 20 GeV positron bunch, and measured with another 20 GeV lower charge trailing positron probe bunch. The measurements are largely consistent with theory.

Measurement of Transverse Wakefields Induced by a Misaligned Positron Bunch in a Hollow Channel Plasma Accelerator

NASA Astrophysics Data System (ADS)

Lindstrøm, C. A.; Adli, E.; Allen, J. M.; An, W.; Beekman, C.; Clarke, C. I.; Clayton, C. E.; Corde, S.; Doche, A.; Frederico, J.; Gessner, S. J.; Green, S. Z.; Hogan, M. J.; Joshi, C.; Litos, M.; Lu, W.; Marsh, K. A.; Mori, W. B.; O'Shea, B. D.; Vafaei-Najafabadi, N.; Yakimenko, V.

2018-03-01

Hollow channel plasma wakefield acceleration is a proposed method to provide high acceleration gradients for electrons and positrons alike: a key to future lepton colliders. However, beams which are misaligned from the channel axis induce strong transverse wakefields, deflecting beams and reducing the collider luminosity. This undesirable consequence sets a tight constraint on the alignment accuracy of the beam propagating through the channel. Direct measurements of beam misalignment-induced transverse wakefields are therefore essential for designing mitigation strategies. We present the first quantitative measurements of transverse wakefields in a hollow plasma channel, induced by an off-axis 20 GeV positron bunch, and measured with another 20 GeV lower charge trailing positron probe bunch. The measurements are largely consistent with theory.

Staging optics considerations for a plasma wakefield acceleration linear collider

NASA Astrophysics Data System (ADS)

Lindstrøm, C. A.; Adli, E.; Allen, J. M.; Delahaye, J. P.; Hogan, M. J.; Joshi, C.; Muggli, P.; Raubenheimer, T. O.; Yakimenko, V.

2016-09-01

Plasma wakefield acceleration offers acceleration gradients of several GeV/m, ideal for a next-generation linear collider. The beam optics requirements between plasma cells include injection and extraction of drive beams, matching the main beam beta functions into the next cell, canceling dispersion as well as constraining bunch lengthening and chromaticity. To maintain a high effective acceleration gradient, this must be accomplished in the shortest distance possible. A working example is presented, using novel methods to correct chromaticity, as well as scaling laws for a high energy regime.

Terahertz Frequency Electron Driven Dielectric Wakefield in Cartesian Symmetric and Photonic Structures

NASA Astrophysics Data System (ADS)

Hoang, Phuc Dinh

Recent works have established that electron beam driven wakefield not only can serve as a viable source for coherent narrow band terahertz radiation but also as a future candidate for high gradient compact linear accelerators. It has also been pointed out that concentric cylindrical dielectric structures, while being very efficient in extracting the energy of the drive beam, which leads to GeV/m gradient level, are susceptible to excitation of transverse modes which give unwanted trajectory kicks and cause beam breakup instabilities. At the same time, temporary high field induced dielectric conductivity was observed in the same system where in response to high field, charge carriers were injected to the conduction band of the dielectric resulting in anomalous dissipation of the wake. Evidence of this point shall be presented in this thesis. First, in order to address the issue of deflection modes, a solution was proposed to use slab structures. Exploiting the Cartesian symmetry, and the wakefield response thereof, a dielectric wakefield system, where both the structure and the beam are flat, may achieve zero net transverse deflection forces. Second, in order to confine high field to the vacuum region away from the dielectric, thus avoiding all high field related problems, photonic band gap materials may be used. Also known as photonic crystals, these structures give rise to defect modes which are confined only to the defect (vacuum) region. Further shaping of the vacuum/dielectric interface, for example by periodic corrugation, not only reduces the field across the interface on the dielectric side by 1/epsilon as consequence of boundary condition, but also brings about further options of tailoring the field. Motivated by these issues, in this thesis, through a series of relevant analytic calculations, simulations, and experiments, the possibility of using Cartesian symmetric, photonic structures for dielectric wakefield will be assessed.

Measurement of Transverse Wakefields Induced by a Misaligned Positron Bunch in a Hollow Channel Plasma Accelerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lindstrom, C. A.; Adli, E.; Allen, J. M.

Hollow channel plasma wakefield acceleration is a proposed method to provide high acceleration gradients for electrons and positrons alike: a key to future lepton colliders. However, beams which are misaligned from the channel axis induce strong transverse wakefields, deflecting beams and reducing the collider luminosity. This undesirable consequence sets a tight constraint on the alignment accuracy of the beam propagating through the channel. Direct measurements of beam misalignment-induced transverse wakefields are therefore essential for designing mitigation strategies. We present the first quantitative measurements of transverse wakefields in a hollow plasma channel, induced by an off-axis 20 GeV positron bunch, andmore » measured with another 20 GeV lower charge trailing positron probe bunch. Furthermore, the measurements are largely consistent with theory.« less

Measurement of Transverse Wakefields Induced by a Misaligned Positron Bunch in a Hollow Channel Plasma Accelerator

DOE PAGES

Lindstrom, C. A.; Adli, E.; Allen, J. M.; ...

2018-03-23

Hollow channel plasma wakefield acceleration is a proposed method to provide high acceleration gradients for electrons and positrons alike: a key to future lepton colliders. However, beams which are misaligned from the channel axis induce strong transverse wakefields, deflecting beams and reducing the collider luminosity. This undesirable consequence sets a tight constraint on the alignment accuracy of the beam propagating through the channel. Direct measurements of beam misalignment-induced transverse wakefields are therefore essential for designing mitigation strategies. We present the first quantitative measurements of transverse wakefields in a hollow plasma channel, induced by an off-axis 20 GeV positron bunch, andmore » measured with another 20 GeV lower charge trailing positron probe bunch. Furthermore, the measurements are largely consistent with theory.« less

Demonstration of a positron beam-driven hollow channel plasma wakefield accelerator

NASA Astrophysics Data System (ADS)

Gessner, Spencer; Adli, Erik; Allen, James M.; An, Weiming; Clarke, Christine I.; Clayton, Chris E.; Corde, Sebastien; Delahaye, J. P.; Frederico, Joel; Green, Selina Z.; Hast, Carsten; Hogan, Mark J.; Joshi, Chan; Lindstrøm, Carl A.; Lipkowitz, Nate; Litos, Michael; Lu, Wei; Marsh, Kenneth A.; Mori, Warren B.; O'Shea, Brendan; Vafaei-Najafabadi, Navid; Walz, Dieter; Yakimenko, Vitaly; Yocky, Gerald

2016-06-01

Plasma wakefield accelerators have been used to accelerate electron and positron particle beams with gradients that are orders of magnitude larger than those achieved in conventional accelerators. In addition to being accelerated by the plasma wakefield, the beam particles also experience strong transverse forces that may disrupt the beam quality. Hollow plasma channels have been proposed as a technique for generating accelerating fields without transverse forces. Here we demonstrate a method for creating an extended hollow plasma channel and measure the wakefields created by an ultrarelativistic positron beam as it propagates through the channel. The plasma channel is created by directing a high-intensity laser pulse with a spatially modulated profile into lithium vapour, which results in an annular region of ionization. A peak decelerating field of 230 MeV m-1 is inferred from changes in the beam energy spectrum, in good agreement with theory and particle-in-cell simulations.

Three electron beams from a laser-plasma wakefield accelerator and the energy apportioning question

PubMed Central

Yang, X.; Brunetti, E.; Gil, D. Reboredo; Welsh, G. H.; Li, F. Y.; Cipiccia, S.; Ersfeld, B.; Grant, D. W.; Grant, P. A.; Islam, M. R.; Tooley, M. P.; Vieux, G.; Wiggins, S. M.; Sheng, Z. M.; Jaroszynski, D. A.

2017-01-01

Laser-wakefield accelerators are compact devices capable of delivering ultra-short electron bunches with pC-level charge and MeV-GeV energy by exploiting the ultra-high electric fields arising from the interaction of intense laser pulses with plasma. We show experimentally and through numerical simulations that a high-energy electron beam is produced simultaneously with two stable lower-energy beams that are ejected in oblique and counter-propagating directions, typically carrying off 5–10% of the initial laser energy. A MeV, 10s nC oblique beam is ejected in a 30°–60° hollow cone, which is filled with more energetic electrons determined by the injection dynamics. A nC-level, 100s keV backward-directed beam is mainly produced at the leading edge of the plasma column. We discuss the apportioning of absorbed laser energy amongst the three beams. Knowledge of the distribution of laser energy and electron beam charge, which determine the overall efficiency, is important for various applications of laser-wakefield accelerators, including the development of staged high-energy accelerators. PMID:28281679

Demonstration of a positron beam-driven hollow channel plasma wakefield accelerator

DOE PAGES

Gessner, Spencer; Adli, Erik; Allen, James M.; ...

2016-06-02

Plasma wakefield accelerators have been used to accelerate electron and positron particle beams with gradients that are orders of magnitude larger than those achieved in conventional accelerators. In addition to being accelerated by the plasma wakefield, the beam particles also experience strong transverse forces that may disrupt the beam quality. Hollow plasma channels have been proposed as a technique for generating accelerating fields without transverse forces. In this study, we demonstrate a method for creating an extended hollow plasma channel and measure the wakefields created by an ultrarelativistic positron beam as it propagates through the channel. The plasma channel ismore » created by directing a high-intensity laser pulse with a spatially modulated profile into lithium vapour, which results in an annular region of ionization. A peak decelerating field of 230 MeV m -1 is inferred from changes in the beam energy spectrum, in good agreement with theory and particle-in-cell simulations.« less

Demonstration of a positron beam-driven hollow channel plasma wakefield accelerator

PubMed Central

Gessner, Spencer; Adli, Erik; Allen, James M.; An, Weiming; Clarke, Christine I.; Clayton, Chris E.; Corde, Sebastien; Delahaye, J. P.; Frederico, Joel; Green, Selina Z.; Hast, Carsten; Hogan, Mark J.; Joshi, Chan; Lindstrøm, Carl A.; Lipkowitz, Nate; Litos, Michael; Lu, Wei; Marsh, Kenneth A.; Mori, Warren B.; O'Shea, Brendan; Vafaei-Najafabadi, Navid; Walz, Dieter; Yakimenko, Vitaly; Yocky, Gerald

2016-01-01

Plasma wakefield accelerators have been used to accelerate electron and positron particle beams with gradients that are orders of magnitude larger than those achieved in conventional accelerators. In addition to being accelerated by the plasma wakefield, the beam particles also experience strong transverse forces that may disrupt the beam quality. Hollow plasma channels have been proposed as a technique for generating accelerating fields without transverse forces. Here we demonstrate a method for creating an extended hollow plasma channel and measure the wakefields created by an ultrarelativistic positron beam as it propagates through the channel. The plasma channel is created by directing a high-intensity laser pulse with a spatially modulated profile into lithium vapour, which results in an annular region of ionization. A peak decelerating field of 230 MeV m−1 is inferred from changes in the beam energy spectrum, in good agreement with theory and particle-in-cell simulations. PMID:27250570

Experimental realization of underdense plasma photocathode wakefield acceleration at FACET

NASA Astrophysics Data System (ADS)

Scherkl, Paul

2017-10-01

Novel electron beam sources from compact plasma accelerator concepts currently mature into the driving technology for next generation high-energy physics and light source facilities. Particularly electron beams of ultra-high brightness could pave the way for major advances for both scientific and commercial applications, but their generation remains tremendously challenging. The presentation outlines the experimental demonstration of the world's first bright electron beam source from spatiotemporally synchronized laser pulses injecting electrons into particle-driven plasma wakefields at FACET. Two distinctive types of operation - laser-triggered density downramp injection (``Plasma Torch'') and underdense plasma photocathode acceleration (``Trojan Horse'') - and their intermediate transitions are characterized and contrasted. Extensive particle-in-cell simulations substantiate the presentation of experimental results. In combination with novel techniques to minimize the beam energy spread, the acceleration scheme presented here promises ultra-high beam quality and brightness.

Short-range wakefields generated in the blowout regime of plasma-wakefield acceleration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stupakov, G.

In the past, calculation of wakefields generated by an electron bunch propagating in a plasma has been carried out in linear approximation, where the plasma perturbation can be assumed small and plasma equations of motion linearized. This approximation breaks down in the blowout regime where a high-density electron driver expels plasma electrons from its path and creates a cavity void of electrons in its wake. Here in this paper, we develop a technique that allows us to calculate short-range longitudinal and transverse wakes generated by a witness bunch being accelerated inside the cavity. Our results can be used for studiesmore » of the beam loading and the hosing instability of the witness bunch in plasma-wakefield and laser-wakefield acceleration.« less

Short-range wakefields generated in the blowout regime of plasma-wakefield acceleration

NASA Astrophysics Data System (ADS)

Stupakov, G.

2018-04-01

In the past, calculation of wakefields generated by an electron bunch propagating in a plasma has been carried out in linear approximation, where the plasma perturbation can be assumed small and plasma equations of motion linearized. This approximation breaks down in the blowout regime where a high-density electron driver expels plasma electrons from its path and creates a cavity void of electrons in its wake. In this paper, we develop a technique that allows us to calculate short-range longitudinal and transverse wakes generated by a witness bunch being accelerated inside the cavity. Our results can be used for studies of the beam loading and the hosing instability of the witness bunch in plasma-wakefield and laser-wakefield acceleration.

Short-range wakefields generated in the blowout regime of plasma-wakefield acceleration

DOE PAGES

Stupakov, G.

2018-04-02

In the past, calculation of wakefields generated by an electron bunch propagating in a plasma has been carried out in linear approximation, where the plasma perturbation can be assumed small and plasma equations of motion linearized. This approximation breaks down in the blowout regime where a high-density electron driver expels plasma electrons from its path and creates a cavity void of electrons in its wake. Here in this paper, we develop a technique that allows us to calculate short-range longitudinal and transverse wakes generated by a witness bunch being accelerated inside the cavity. Our results can be used for studiesmore » of the beam loading and the hosing instability of the witness bunch in plasma-wakefield and laser-wakefield acceleration.« less

UNDULATOR-BASED LASER WAKEFIELD ACCELERATOR ELECTRON BEAM DIAGNOSTIC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bakeman, M.S.; Fawley, W.M.; Leemans, W. P.

to couple the THUNDER undulator to the LOASIS Lawrence Berkeley National Laboratory (LBNL) laser wakefield accelerator (LWFA). Currently the LWFA has achieved quasi-monoenergetic electron beams with energies up to 1 GeV. These ultra-short, high-peak-current, electron beams are ideal for driving a compact XUV free electron laser (FEL). Understanding the electron beam properties such as the energy spread and emittance is critical for achieving high quality light sources with high brightness. By using an insertion device such as an undulator and observing changes in the spontaneous emission spectrum, the electron beam energy spread and emittance can be measured with high precision.more » The initial experiments will use spontaneous emission from 1.5 m of undulator. Later experiments will use up to 5 m of undulator with a goal of a high gain, XUV FEL.« less

Giga-electronvolt electrons due to a transition from laser wakefield acceleration to plasma wakefield acceleration

NASA Astrophysics Data System (ADS)

Masson-Laborde, P. E.; Mo, M. Z.; Ali, A.; Fourmaux, S.; Lassonde, P.; Kieffer, J. C.; Rozmus, W.; Teychenné, D.; Fedosejevs, R.

2014-12-01

We show through experiments that a transition from laser wakefield acceleration (LWFA) regime to a plasma wakefield acceleration (PWFA) regime can drive electrons up to energies close to the GeV level. Initially, the acceleration mechanism is dominated by the bubble created by the laser in the nonlinear regime of LWFA, leading to an injection of a large number of electrons. After propagation beyond the depletion length, leading to a depletion of the laser pulse, whose transverse ponderomotive force is not able to sustain the bubble anymore, the high energy dense bunch of electrons propagating inside bubble will drive its own wakefield by a PWFA regime. This wakefield will be able to trap and accelerate a population of electrons up to the GeV level during this second stage. Three dimensional particle-in-cell simulations support this analysis and confirm the scenario.

Probing plasma wakefields using electron bunches generated from a laser wakefield accelerator

NASA Astrophysics Data System (ADS)

Zhang, C. J.; Wan, Y.; Guo, B.; Hua, J. F.; Pai, C.-H.; Li, F.; Zhang, J.; Ma, Y.; Wu, Y. P.; Xu, X. L.; Mori, W. B.; Chu, H.-H.; Wang, J.; Lu, W.; Joshi, C.

2018-04-01

We show experimental results of probing the electric field structure of plasma wakes by using femtosecond relativistic electron bunches generated from a laser wakefield accelerator. Snapshots of laser-driven linear wakes in plasmas with different densities and density gradients are captured. The spatiotemporal evolution of the wake in a plasma density up-ramp is recorded. Two parallel wakes driven by a laser with a main spot and sidelobes are identified in the experiment and reproduced in simulations. The capability of this new method for capturing the electron- and positron-driven wakes is also shown via 3D particle-in-cell simulations.

Giga-electronvolt electrons due to a transition from laser wakefield acceleration to plasma wakefield acceleration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Masson-Laborde, P. E., E-mail: paul-edouard.masson-laborde@cea.fr; Teychenné, D.; Mo, M. Z.

2014-12-15

We show through experiments that a transition from laser wakefield acceleration (LWFA) regime to a plasma wakefield acceleration (PWFA) regime can drive electrons up to energies close to the GeV level. Initially, the acceleration mechanism is dominated by the bubble created by the laser in the nonlinear regime of LWFA, leading to an injection of a large number of electrons. After propagation beyond the depletion length, leading to a depletion of the laser pulse, whose transverse ponderomotive force is not able to sustain the bubble anymore, the high energy dense bunch of electrons propagating inside bubble will drive its ownmore » wakefield by a PWFA regime. This wakefield will be able to trap and accelerate a population of electrons up to the GeV level during this second stage. Three dimensional particle-in-cell simulations support this analysis and confirm the scenario.« less

Capturing relativistic wakefield structures in plasmas using ultrashort high-energy electrons as a probe

DOE PAGES

Zhang, C. J.; Hua, J. F.; Xu, X. L.; ...

2016-07-11

A new method capable of capturing coherent electric field structures propagating at nearly the speed of light in plasma with a time resolution as small as a few femtoseconds is proposed. This method uses a few femtoseconds long relativistic electron bunch to probe the wake produced in a plasma by an intense laser pulse or an ultra-short relativistic charged particle beam. As the probe bunch traverses the wake, its momentum is modulated by the electric field of the wake, leading to a density variation of the probe after free-space propagation. This variation of probe density produces a snapshot of themore » wake that can directly give many useful information of the wake structure and its evolution. Furthermore, this snapshot allows detailed mapping of the longitudinal and transverse components of the wakefield. We develop a theoretical model for field reconstruction and verify it using 3-dimensional particle-in-cell (PIC) simulations. This model can accurately reconstruct the wakefield structure in the linear regime, and it can also qualitatively map the major features of nonlinear wakes. As a result, the capturing of the injection in a nonlinear wake is demonstrated through 3D PIC simulations as an example of the application of this new method.« less

High-pressure liquid chromatographic gradient mixer

DOEpatents

Daughton, C.G.; Sakaji, R.H.

1982-09-08

A gradient mixer effects the continuous mixing of any two miscible solvents without excessive decay or dispersion of the resultant isocratic effluent or of a linear or exponential gradient. The two solvents are fed under low or high pressure by means of two high performance liquid chromatographic pumps. The mixer comprises a series of ultra-low dead volume stainless steel tubes and low dead volume chambers. The two solvent streams impinge head-on at high fluxes. This initial nonhomogeneous mixture is then passed through a chamber packed with spirally-wound wires which cause turbulent mixing thereby homogenizing the mixture with minimum band-broadening.

Short-pulse, high-energy radiation generation from laser-wakefield accelerated electron beams

NASA Astrophysics Data System (ADS)

Schumaker, Will

2013-10-01

Recent experimental results of laser wakefield acceleration (LWFA) of ~GeV electrons driven by the 200TW HERCULES and the 400TW ASTRA-GEMINI laser systems and their subsequent generation of photons, positrons, and neutrons are presented. In LWFA, high-intensity (I >1019 W /cm2), ultra-short (τL < 1 / (2 πωpe)) laser pulses drive highly nonlinear plasma waves which can trap ~ nC of electrons and accelerate them to ~GeV energies over ~cm lengths. These electron beams can then be converted by a high-Z target via bremsstrahlung into low-divergence (< 20 mrad) beams of high-energy (<600 MeV) photons and subsequently into positrons via the Bethe-Heitler process. By increasing the material thickness and Z, the resulting Ne+ /Ne- ratio can approach unity, resulting in a near neutral density plasma jet. These quasi-neutral beams are presumed to retain the short-pulse (τL < 40 fs) characteristic of the electron beam, resulting in a high peak density of ne- /e+ ~ 1016 cm-3 , making the source an excellent candidate for laboratory study of astrophysical leptonic jets. Alternatively, the electron beam can be interacted with a counter-propagating, ultra-high intensity (I >1021 W /cm2) laser pulse to undergo inverse Compton scattering and emit a high-peak brightness beam of high-energy photons. Preliminary results and experimental sensitivities of the electron-laser beam overlap are presented. The high-energy photon beams can be spectrally resolved using a forward Compton scattering spectrometer. Moreover, the photon flux can be characterized by a pixelated scintillator array and by nuclear activation and (γ,n) neutron measurements from the photons interacting with a secondary solid target. Monte-Carlo simulations were performed using FLUKA to support the yield estimates. This research was supported by DOE/NSF-PHY 0810979, NSF CAREER 1054164, DARPA AXiS N66001-11-1-4208, SF/DNDO F021166, and the Leverhulme Trust ECF-2011-383.

Longitudinal gas-density profilometry for plasma-wakefield acceleration targets

NASA Astrophysics Data System (ADS)

Schaper, Lucas; Goldberg, Lars; Kleinwächter, Tobias; Schwinkendorf, Jan-Patrick; Osterhoff, Jens

2014-03-01

Precise tailoring of plasma-density profiles has been identified as one of the critical points in achieving stable and reproducible conditions in plasma wakefield accelerators. Here, the strict requirements of next generation plasma-wakefield concepts, such as hybrid-accelerators, with densities around 1017 cm-3 pose challenges to target fabrication as well as to their reliable diagnosis. To mitigate these issues we combine target simulation with fabrication and characterization. The resulting density profiles in capillaries with gas jet and multiple in- and outlets are simulated with the fluid code OpenFOAM. Satisfactory simulation results then are followed by fabrication of the desired target shapes with structures down to the 10 μm level. The detection of Raman scattered photons using lenses with large collection solid angle allows to measure the corresponding longitudinal density profiles at different number densities and allows a detection sensitivity down to the low 1017 cm-3 density range at high spatial resolution. This offers the possibility to gain insight into steep density gradients as for example in gas jets and at the plasma-to-vacuum transition.

Two-Color Laser High-Harmonic Generation in Cavitated Plasma Wakefields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schroeder, Carl; Benedetti, Carlo; Esarey, Eric

2016-10-03

A method is proposed for producing coherent x-rays via high-harmonic generation using a laser interacting with highly-stripped ions in cavitated plasma wakefields. Two laser pulses of different colors are employed: a long-wavelength pulse for cavitation and a short-wavelength pulse for harmonic generation. This method enables efficient laser harmonic generation in the sub-nm wavelength regime.

High pressure liquid chromatographic gradient mixer

DOEpatents

Daughton, Christian G.; Sakaji, Richard H.

1985-01-01

A gradient mixer which effects the continuous mixing of any two miscible solvents without excessive decay or dispersion of the resultant isocratic effluent or of a linear or exponential gradient. The two solvents are fed under low or high pressure by means of two high performance liquid chromatographic pumps. The mixer comprises a series of ultra-low dead volume stainless steel tubes and low dead volume chambers. The two solvent streams impinge head-on at high fluxes. This initial nonhomogeneous mixture is then passed through a chamber packed with spirally-wound wires which cause turbulent mixing thereby homogenizing the mixture with minimum "band-broadening".

A high power, high density helicon discharge for the plasma wakefield accelerator experiment AWAKE

NASA Astrophysics Data System (ADS)

Buttenschön, B.; Fahrenkamp, N.; Grulke, O.

2018-07-01

A plasma cell prototype for the plasma wakefield accelerator experiment AWAKE based on a helicon discharge is presented. In the 1 m long prototype module a multiple antenna helicon discharge with an rf power density of 100 MW m‑3 is established. Based on the helicon dispersion relation, a linear scaling of plasma density with magnetic field is observed for rf frequencies above the lower hybrid frequency, ω LH ≤ 0.8ω rf. Density profiles are highest on the device axis and show shallow radial gradients, thus providing a relatively constant plasma density in the center over a radial range of Δr ≈ 10 mm with less than 10% variation. Peak plasma densities up to 7 × 1020 m‑3 are transiently achieved with a reproducibility that is sufficient for AWAKE. The results are in good agreement with power balance calculations.

GeV Electrons due to a Transition from Laser Wakefield Acceleration to Plasma Wakefield Acceleration

NASA Astrophysics Data System (ADS)

Mo, M. Z.; Masson-Laborde, P.-E.; Ali, A.; Fourmaux, S.; Lassonde, P.; Kieffer, J.-C.; Rozmus, W.; Teychenné, D.; Fedosejevs, R.

2014-10-01

The Laser Wakefield Acceleration (LWFA) experiments performed with the 200 TW laser system located at the Canadian Advanced Laser Light Source facility at INRS, Varennes (Québec) observed at relatively high plasma densities (1 × 1019cm-3) electron bunches of GeV energy gain, more than double of the predicted energy using Lu's scaling law. This energy boost phenomena can be attributed to a transition from LWFA regime to a plasma wakefield acceleration (PWFA) regime. In the first stage, the acceleration mechanism is dominated by the bubble created by the laser in the regime of LWFA, leading to an injection of a large number of electrons. After propagation beyond the depletion length, where the laser pulse is depleted and it can no longer sustain the bubble anymore, the dense bunch of high energy electrons propagating inside the bubble will drive its own wakefield in the PWFA regime that can trap and accelerate a secondary population of electrons up to the GeV level. 3D particle-in-cell simulations support this analysis, and confirm the scenario.

Improvements to laser wakefield accelerated electron beam stability, divergence, and energy spread using three-dimensional printed two-stage gas cell targets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vargas, M.; Schumaker, W.; He, Z.-H.

2014-04-28

High intensity, short pulse lasers can be used to accelerate electrons to ultra-relativistic energies via laser wakefield acceleration (LWFA) [T. Tajima and J. M. Dawson, Phys. Rev. Lett. 43, 267 (1979)]. Recently, it was shown that separating the injection and acceleration processes into two distinct stages could prove beneficial in obtaining stable, high energy electron beams [Gonsalves et al., Nat. Phys. 7, 862 (2011); Liu et al., Phys. Rev. Lett. 107, 035001 (2011); Pollock et al., Phys. Rev. Lett. 107, 045001 (2011)]. Here, we use a stereolithography based 3D printer to produce two-stage gas targets for LWFA experiments on themore » HERCULES laser system at the University of Michigan. We demonstrate substantial improvements to the divergence, pointing stability, and energy spread of a laser wakefield accelerated electron beam compared with a single-stage gas cell or gas jet target.« less

Near field plasmonic gradient effects on high vacuum tip-enhanced Raman spectroscopy.

PubMed

Fang, Yurui; Zhang, Zhenglong; Chen, Li; Sun, Mengtao

2015-01-14

Near field gradient effects in high vacuum tip-enhanced Raman spectroscopy (HV-TERS) are a recent developing ultra-sensitive optical and spectral analysis technology on the nanoscale, based on the plasmons and plasmonic gradient enhancement in the near field and under high vacuum. HV-TERS can not only be used to detect ultra-sensitive Raman spectra enhanced by surface plasmon, but also to detect clear molecular IR-active modes enhanced by strongly plasmonic gradient. Furthermore, the molecular overtone modes and combinational modes can also be experimentally measured, where the Fermi resonance and Darling-Dennison resonance were successfully observed in HV-TERS. Theoretical calculations using electromagnetic field theory firmly supported experimental observation. The intensity ratio of the plasmon gradient term over the linear plasmon term can reach values greater than 1. Theoretical calculations also revealed that with the increase in gap distance between tip and substrate, the decrease in the plasmon gradient was more significant than the decrease in plasmon intensity, which is the reason that the gradient Raman can be only observed in the near field. Recent experimental results of near field gradient effects on HV-TERS were summarized, following the section of the theoretical analysis.

A Stable High-Energy Electron Source from Laser Wakefield Acceleration

NASA Astrophysics Data System (ADS)

Zhang, Ping; Zhao, Baozhen; Liu, Cheng; Yan, Wenchao; Golovin, Grigory; Banerjee, Sudeep; Chen, Shouyuan; Haden, Daniel; Fruhling, Colton; Umstadter, Donald

2016-10-01

The stability of the electron source from laser wake-field acceleration (LWFA) is essential for applications, such as novel x-ray sources and fundamental experiments in high field physics. To obtain such a stable source, we used an optimal laser pulse and a novel gas nozzle. The high-power laser pulse on target was focused to a diffraction-limited spot by the use of adaptive wavefront correction and the pulse duration was transform limited by the use of spectral feedback control. An innovative design for the nozzle led to a stable, flat-top profile with diameters of 4 mm and 8 mm with a high Mach-number ( 6). In experiments to generate high-energy electron beams by LWFA, we were able to obtain reproducible results with beam energy of 800 MeV and charge >10 pC. Higher charge but broader energy spectrum resulted when the plasma density was increased. These developments have resulted in a laser-driven wakefield accelerator that is stable and robust. With this device, we show that narrowband high-energy x-rays beams can be generated by the inverse-Compton scattering process. This accelerator has also been used in recent experiments to study nonlinear effects in the interaction of high-energy electron beams with ultraintense laser pulses. This material is based upon work supported by NSF No. PHY-153700; US DOE, Office of Science, BES, # DE-FG02-05ER15663; AFOSR # FA9550-11-1-0157; and DHS DNDO # HSHQDC-13-C-B0036.

Observation of Wakefield Suppression in a Photonic-Band-Gap Accelerator Structure

DOE PAGES

Simakov, Evgenya I.; Arsenyev, Sergey A.; Buechler, Cynthia E.; ...

2016-02-10

We report experimental observation of higher order mode (HOM) wakefield suppression in a room-temperature traveling-wave photonic band gap (PBG) accelerating structure at 11.700 GHz. It has been long recognized that PBG structures have potential for reducing long-range wakefields in accelerators. The first ever demonstration of acceleration in a room-temperature PBG structure was conducted in 2005. Since then, the importance of PBG accelerator research has been recognized by many institutions. However, the full experimental characterization of the wakefield spectrum and demonstration of wakefield suppression when the accelerating structure is excited by an electron beam has not been performed to date. Wemore » conducted an experiment at the Argonne Wakefield Accelerator (AWA) test facility and observed wakefields excited by a single high charge electron bunch when it passes through a PBG accelerator structure. Lastly, excellent HOM suppression properties of the PBG accelerator were demonstrated in the beam test.« less

Microstructural imaging of the human brain with a 'super-scanner': 10 key advantages of ultra-strong gradients for diffusion MRI.

PubMed

Jones, D K; Alexander, D C; Bowtell, R; Cercignani, M; Dell'Acqua, F; McHugh, D J; Miller, K L; Palombo, M; Parker, G J M; Rudrapatna, U S; Tax, C M W

2018-05-22

The key component of a microstructural diffusion MRI 'super-scanner' is a dedicated high-strength gradient system that enables stronger diffusion weightings per unit time compared to conventional gradient designs. This can, in turn, drastically shorten the time needed for diffusion encoding, increase the signal-to-noise ratio, and facilitate measurements at shorter diffusion times. This review, written from the perspective of the UK National Facility for In Vivo MR Imaging of Human Tissue Microstructure, an initiative to establish a shared 300 mT/m-gradient facility amongst the microstructural imaging community, describes ten advantages of ultra-strong gradients for microstructural imaging. Specifically, we will discuss how the increase of the accessible measurement space compared to a lower-gradient systems (in terms of Δ, b-value, and TE) can accelerate developments in the areas of 1) axon diameter distribution mapping; 2) microstructural parameter estimation; 3) mapping micro-vs macroscopic anisotropy features with gradient waveforms beyond a single pair of pulsed-gradients; 4) multi-contrast experiments, e.g. diffusion-relaxometry; 5) tractography and high-resolution imaging in vivo and 6) post mortem; 7) diffusion-weighted spectroscopy of metabolites other than water; 8) tumour characterisation; 9) functional diffusion MRI; and 10) quality enhancement of images acquired on lower-gradient systems. We finally discuss practical barriers in the use of ultra-strong gradients, and provide an outlook on the next generation of 'super-scanners'. Copyright © 2018. Published by Elsevier Inc.

Ultra-High Accelerating Gradients in Radio-Frequency Cryogenic Copper Structures

NASA Astrophysics Data System (ADS)

Cahill, Alexander David

Normal conducting radio-frequency (rf) particle accelerators have many applications, including colliders for high energy physics, high-intensity synchrotron light sources, non-destructive testing for security, and medical radiation therapy. In these applications, the accelerating gradient is an important parameter. Specifically for high energy physics, increasing the accelerating gradient extends the potential energy reach and is viewed as a way to mitigate their considerable cost. Furthermore, a gradient increase will enable for more compact and thus accessible free electron lasers (FELs). The major factor limiting larger accelerating gradients is vacuum rf breakdown. Basic physics of this phenomenon has been extensively studied over the last few decades. During which, the occurrence of rf breakdowns was shown to be probabilistic, and can be characterized by a breakdown rate. The current consensus is that vacuum rf breakdowns are caused by movements of crystal defects induced by periodic mechanical stress. The stress may be caused by pulsed surface heating and large electric fields. A compelling piece of evidence that supports this hypothesis is that accelerating structures constructed from harder materials exhibit larger accelerating gradients for similar breakdown rates. One possible method to increase sustained electric fields in copper cavities is to cool them to temperatures below 77 K, where the rf surface resistance and coefficient of thermal expansion decrease, while the yield strength (which correlates with hardness) and thermal conductivity increase. These changes in material properties at low temperature increases metal hardness and decreases the mechanical stress from exposure to rf electromagnetic fields. To test the validity of the improvement in breakdown rate, experiments were conducted with cryogenic accelerating cavities in the Accelerator Structure Test Area (ASTA) at SLAC National Accelerator Laboratory. A short 11.4 GHz standing wave

Excitation of wakefields in a relativistically hot plasma created by dying non-linear plasma wakefields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sahai, A. A.; Katsouleas, T. C.; Gessner, S.

2012-12-21

We study the various physical processes and their timescales involved in the excitation of wakefields in relativistically hot plasma. This has relevance to the design of a high repetition-rate plasma wakefield collider in which the plasma has not had time to cool between bunches in addition to understanding the physics of cosmic jets in relativistically hot astrophysical plasmas. When the plasma is relativistically hot (plasma temperature near m{sub e}c{sup 2}), the thermal pressure competes with the restoring force of ion space charge and can reduce or even eliminate the accelerating field of a wake. We will investigate explicitly the casemore » where the hot plasma is created by a preceding Wakefield drive bunch 10's of picoseconds to many nanoseconds ahead of the next drive bunch. The relativistically hot plasma is created when the excess energy (not coupled to the driven e{sup -} bunch) in the wake driven by the drive e{sup -} bunch is eventually converted into thermal energy on 10's of picosecond timescale. We will investigate the thermalization and diffusion processes of this non-equilibrium plasma on longer time scales, including the effects of ambi-polar diffusion of ions driven by hot electron expansion, possible Columbic explosion of ions producing higher ionization states and ionization of surrounding neutral atoms via collisions with hot electrons. Preliminary results of the transverse and longitudinal wakefields at different timescales of separation between a first and second bunch are presented and a possible experiment to study this topic at the FACET facility is described.« less

Coexistence of colossal stress and texture gradients in sputter deposited nanocrystalline ultra-thin metal films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuru, Yener; Welzel, Udo; Mittemeijer, Eric J.

2014-12-01

This paper demonstrates experimentally that ultra-thin, nanocrystalline films can exhibit coexisting colossal stress and texture depth gradients. Their quantitative determination is possible by X-ray diffraction experiments. Whereas a uniform texture by itself is known to generally cause curvature in so-called sin{sup 2}ψ plots, it is shown that the combined action of texture and stress gradients provides a separate source of curvature in sin{sup 2}ψ plots (i.e., even in cases where a uniform texture does not induce such curvature). On this basis, the texture and stress depth profiles of a nanocrystalline, ultra-thin (50 nm) tungsten film could be determined.

Ultra-thin and -broadband microwave magnetic absorber enhanced by phase gradient metasurface incorporation

NASA Astrophysics Data System (ADS)

Fan, Ya; Wang, Jiafu; Li, Yongfeng; Pang, Yongqiang; Zheng, Lin; Xiang, Jiayu; Zhang, Jieqiu; Qu, Shaobo

2018-05-01

Based on the effect of anomalous reflection and refraction caused by the circularly cross-polarized phase gradient metasurface (PGM), an ultra-thin and -broadband composite absorber composed of metasurface and conventional magnetic absorbing film is proposed and demonstrated in this paper. In the case of keeping nearly the same thickness of absorbing layer, the equivalent thickness of magnetic absorbing film is enlarged by the effect of anomalous reflection and refraction, resulting in the expansion and improvement of the absorbing bandwidth and efficiency in low microwave frequency. A biarc metallic sub-cell for circularly crossed polarization is adopted to form a broadband phase gradient, by the means of rotating the Pancharatnam–Berry phases. As indicated in the experimental results, the fabricated 3.6 mm-thick absorber can averagely absorb microwave energy with the specular reflection below  ‑10 dB in the frequency interval of 2–12 GHz, which shows a good match with simulated results. Due to ultra-thin thickness and ultra-wide operating bandwidth, the proposed application of PGM in absorbing can provide an alternative way to enhance the absorbing property of current absorbing materials.

Experimental high gradient testing of a 17.1 GHz photonic band-gap accelerator structure

DOE PAGES

Munroe, Brian J.; Zhang, JieXi; Xu, Haoran; ...

2016-03-29

In this paper, we report the design, fabrication, and high gradient testing of a 17.1 GHz photonic band-gap (PBG) accelerator structure. Photonic band-gap (PBG) structures are promising candidates for electron accelerators capable of high-gradient operation because they have the inherent damping of high order modes required to avoid beam breakup instabilities. The 17.1 GHz PBG structure tested was a single cell structure composed of a triangular array of round copper rods of radius 1.45 mm spaced by 8.05 mm. The test assembly consisted of the test PBG cell located between conventional (pillbox) input and output cells, with input power ofmore » up to 4 MW from a klystron supplied via a TM 01 mode launcher. Breakdown at high gradient was observed by diagnostics including reflected power, downstream and upstream current monitors and visible light emission. The testing procedure was first benchmarked with a conventional disc-loaded waveguide structure, which reached a gradient of 87 MV=m at a breakdown probability of 1.19 × 10 –1 per pulse per meter. The PBG structure was tested with 100 ns pulses at gradient levels of less than 90 MV=m in order to limit the surface temperature rise to 120 K. The PBG structure reached up to 89 MV=m at a breakdown probability of 1.09 × 10 –1 per pulse per meter. These test results show that a PBG structure can simultaneously operate at high gradients and low breakdown probability, while also providing wakefield damping.« less

Transition from wakefield generation to soliton formation.

PubMed

Holkundkar, Amol R; Brodin, Gert

2018-04-01

It is well known that when a short laser pulse propagates in an underdense plasma, it induces longitudinal plasma oscillations at the plasma frequency after the pulse, typically referred to as the wakefield. However, for plasma densities approaching the critical density, wakefield generation is suppressed, and instead the EM-pulse (electromagnetic pulse) undergoes nonlinear self-modulation. In this article we have studied the transition from the wakefield generation to formation of quasi-solitons as the plasma density is increased. For this purpose we have applied a one-dimensional relativistic cold fluid model, which has also been compared with particle-in-cell simulations. A key result is that the energy loss of the EM-pulse due to wakefield generation has its maximum for a plasma density of the order 10% of the critical density, but that wakefield generation is sharply suppressed when the density is increased further.

Transition from wakefield generation to soliton formation

NASA Astrophysics Data System (ADS)

Holkundkar, Amol R.; Brodin, Gert

2018-04-01

It is well known that when a short laser pulse propagates in an underdense plasma, it induces longitudinal plasma oscillations at the plasma frequency after the pulse, typically referred to as the wakefield. However, for plasma densities approaching the critical density, wakefield generation is suppressed, and instead the EM-pulse (electromagnetic pulse) undergoes nonlinear self-modulation. In this article we have studied the transition from the wakefield generation to formation of quasi-solitons as the plasma density is increased. For this purpose we have applied a one-dimensional relativistic cold fluid model, which has also been compared with particle-in-cell simulations. A key result is that the energy loss of the EM-pulse due to wakefield generation has its maximum for a plasma density of the order 10% of the critical density, but that wakefield generation is sharply suppressed when the density is increased further.

Generation of high-field narrowband terahertz radiation by counterpropagating plasma wakefields

NASA Astrophysics Data System (ADS)

Timofeev, I. V.; Annenkov, V. V.; Volchok, E. P.

2017-10-01

It is found that nonlinear interaction of plasma wakefields driven by counterpropagating laser or particle beams can efficiently generate high-power electromagnetic radiation at the second harmonic of the plasma frequency. Using a simple analytical theory and particle-in-cell simulations, we show that this phenomenon can be attractive for producing high-field ( ˜10 MV/cm) tunable terahertz radiation with a narrow line width. For laser drivers produced by existing petawatt-class systems, this nonlinear process opens the way to the generation of gigawatt, multi-millijoule terahertz pulses which are not presently available for any other generating schemes.

Towards Attosecond High-Energy Electron Bunches: Controlling Self-Injection in Laser-Wakefield Accelerators Through Plasma-Density Modulation

NASA Astrophysics Data System (ADS)

Tooley, M. P.; Ersfeld, B.; Yoffe, S. R.; Noble, A.; Brunetti, E.; Sheng, Z. M.; Islam, M. R.; Jaroszynski, D. A.

2017-07-01

Self-injection in a laser-plasma wakefield accelerator is usually achieved by increasing the laser intensity until the threshold for injection is exceeded. Alternatively, the velocity of the bubble accelerating structure can be controlled using plasma density ramps, reducing the electron velocity required for injection. We present a model describing self-injection in the short-bunch regime for arbitrary changes in the plasma density. We derive the threshold condition for injection due to a plasma density gradient, which is confirmed using particle-in-cell simulations that demonstrate injection of subfemtosecond bunches. It is shown that the bunch charge, bunch length, and separation of bunches in a bunch train can be controlled by tailoring the plasma density profile.

Enhanced electron yield from laser-driven wakefield acceleration in high-Z gas jets.

PubMed

Mirzaie, Mohammad; Hafz, Nasr A M; Li, Song; Liu, Feng; He, Fei; Cheng, Ya; Zhang, Jie

2015-10-01

An investigation of the electron beam yield (charge) form helium, nitrogen, and neon gas jet plasmas in a typical laser-plasma wakefield acceleration experiment is carried out. The charge measurement is made by imaging the electron beam intensity profile on a fluorescent screen into a charge coupled device which was cross-calibrated with an integrated current transformer. The dependence of electron beam charge on the laser and plasma conditions for the aforementioned gases are studied. We found that laser-driven wakefield acceleration in low Z-gas jet targets usually generates high-quality and well-collimated electron beams with modest yields at the level of 10-100 pC. On the other hand, filamentary electron beams which are observed from high-Z gases at higher densities reached much higher yields. Evidences for cluster formation were clearly observed in the nitrogen gas jet target, where we received the highest electron beam charge of ∼1.7 nC. Those intense electron beams will be beneficial for the applications on the generation of bright X-rays, gamma rays radiations, and energetic positrons via the bremsstrahlung or inverse-scattering processes.

Post-mortem inference of the human hippocampal connectivity and microstructure using ultra-high field diffusion MRI at 11.7 T.

PubMed

Beaujoin, Justine; Palomero-Gallagher, Nicola; Boumezbeur, Fawzi; Axer, Markus; Bernard, Jeremy; Poupon, Fabrice; Schmitz, Daniel; Mangin, Jean-François; Poupon, Cyril

2018-06-01

The human hippocampus plays a key role in memory management and is one of the first structures affected by Alzheimer's disease. Ultra-high magnetic resonance imaging provides access to its inner structure in vivo. However, gradient limitations on clinical systems hinder access to its inner connectivity and microstructure. A major target of this paper is the demonstration of diffusion MRI potential, using ultra-high field (11.7 T) and strong gradients (750 mT/m), to reveal the extra- and intra-hippocampal connectivity in addition to its microstructure. To this purpose, a multiple-shell diffusion-weighted acquisition protocol was developed to reach an ultra-high spatio-angular resolution with a good signal-to-noise ratio. The MRI data set was analyzed using analytical Q-Ball Imaging, Diffusion Tensor Imaging (DTI), and Neurite Orientation Dispersion and Density Imaging models. High Angular Resolution Diffusion Imaging estimates allowed us to obtain an accurate tractography resolving more complex fiber architecture than DTI models, and subsequently provided a map of the cross-regional connectivity. The neurite density was akin to that found in the histological literature, revealing the three hippocampal layers. Moreover, a gradient of connectivity and neurite density was observed between the anterior and the posterior part of the hippocampus. These results demonstrate that ex vivo ultra-high field/ultra-high gradients diffusion-weighted MRI allows the mapping of the inner connectivity of the human hippocampus, its microstructure, and to accurately reconstruct elements of the polysynaptic intra-hippocampal pathway using fiber tractography techniques at very high spatial/angular resolutions.

High-quality electron beams from beam-driven plasma accelerators by wakefield-induced ionization injection.

PubMed

Martinez de la Ossa, A; Grebenyuk, J; Mehrling, T; Schaper, L; Osterhoff, J

2013-12-13

We propose a new and simple strategy for controlled ionization-induced trapping of electrons in a beam-driven plasma accelerator. The presented method directly exploits electric wakefields to ionize electrons from a dopant gas and capture them into a well-defined volume of the accelerating and focusing wake phase, leading to high-quality witness bunches. This injection principle is explained by example of three-dimensional particle-in-cell calculations using the code OSIRIS. In these simulations a high-current-density electron-beam driver excites plasma waves in the blowout regime inside a fully ionized hydrogen plasma of density 5×10(17)cm-3. Within an embedded 100  μm long plasma column contaminated with neutral helium gas, the wakefields trigger ionization, trapping of a defined fraction of the released electrons, and subsequent acceleration. The hereby generated electron beam features a 1.5 kA peak current, 1.5  μm transverse normalized emittance, an uncorrelated energy spread of 0.3% on a GeV-energy scale, and few femtosecond bunch length.

Spatial Control of Laser Wakefield Accelerated Electron Beams

NASA Astrophysics Data System (ADS)

Maksimchuk, A.; Behm, K.; Zhao, T.; Joglekar, A. S.; Hussein, A.; Nees, J.; Thomas, A. G. R.; Krushelnick, K.; Elle, J.; Lucero, A.; Samarin, G. M.; Sarry, G.; Warwick, J.

2017-10-01

The laser wakefield experiments to study and control spatial properties of electron beams were performed using HERCULES laser at the University of Michigan at power of 100 TW. In the first experiment multi-electron beam generation was demonstrated using co-propagating, parallel laser beams with a π-phase shift mirror and showing that interaction between the wakefields can cause injection to occur for plasma and laser parameters in which a single wakefield displays no significant injection. In the second experiment a magnetic triplet quadrupole system was used to refocus and stabilize electron beams at the distance of 60 cm from the interaction region. This produced a 10-fold increase in remote gamma-ray activation of 63Cu using a lead converter. In the third experiment measurements of un-trapped electrons with high transverse momentum produce a 500 mrad (FWHM) ring. This ring is formed by electrons that receive a forward momentum boost by traversing behind the bubble and its size is inversely proportional to the plasma density. The characterization of divergence and charge of this electron ring may reveal information about the wakefield structure and trapping potential. Supported by U.S. Department of Energy and the National Nuclear Security Administration and Air Force Office of Scientific Research.

Plasma Wakefield Acceleration of an Intense Positron Beam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blue, B

2004-04-21

The Plasma Wakefield Accelerator (PWFA) is an advanced accelerator concept which possess a high acceleration gradient and a long interaction length for accelerating both electrons and positrons. Although electron beam-plasma interactions have been extensively studied in connection with the PWFA, very little work has been done with respect to positron beam-plasma interactions. This dissertation addresses three issues relating to a positron beam driven plasma wakefield accelerator. These issues are (a) the suitability of employing a positron drive bunch to excite a wake; (b) the transverse stability of the drive bunch; and (c) the acceleration of positrons by the plasma wakemore » that is driven by a positron bunch. These three issues are explored first through computer simulations and then through experiments. First, a theory is developed on the impulse response of plasma to a short drive beam which is valid for small perturbations to the plasma density. This is followed up with several particle-in-cell (PIC) simulations which study the experimental parameter (bunch length, charge, radius, and plasma density) range. Next, the experimental setup is described with an emphasis on the equipment used to measure the longitudinal energy variations of the positron beam. Then, the transverse dynamics of a positron beam in a plasma are described. Special attention is given to the way focusing, defocusing, and a tilted beam would appear to be energy variations as viewed on our diagnostics. Finally, the energy dynamics imparted on a 730 {micro}m long, 40 {micro}m radius, 28.5 GeV positron beam with 1.2 x 10{sup 10} particles in a 1.4 meter long 0-2 x 10{sup 14} e{sup -}/cm{sup 3} plasma is described. First the energy loss was measured as a function of plasma density and the measurements are compared to theory. Then, an energy gain of 79 {+-} 15 MeV is shown. This is the first demonstration of energy gain of a positron beam in a plasma and it is in good agreement with the

Observation of Wakefields and Resonances in Coherent Synchrotron Radiation

NASA Astrophysics Data System (ADS)

Billinghurst, B. E.; Bergstrom, J. C.; Baribeau, C.; Batten, T.; Dallin, L.; May, T. E.; Vogt, J. M.; Wurtz, W. A.; Warnock, R.; Bizzozero, D. A.; Kramer, S.

2015-05-01

We report on high resolution measurements of resonances in the spectrum of coherent synchrotron radiation (CSR) at the Canadian Light Source (CLS). The resonances permeate the spectrum at wave number intervals of 0.074 cm-1 , and are highly stable under changes in the machine setup (energy, bucket filling pattern, CSR in bursting or continuous mode). Analogous resonances were predicted long ago in an idealized theory as eigenmodes of a smooth toroidal vacuum chamber driven by a bunched beam moving on a circular orbit. A corollary of peaks in the spectrum is the presence of pulses in the wakefield of the bunch at well-defined spatial intervals. Through experiments and further calculations we elucidate the resonance and wakefield mechanisms in the CLS vacuum chamber, which has a fluted form much different from a smooth torus. The wakefield is observed directly in the 30-110 GHz range by rf diodes, and indirectly by an interferometer in the THz range. The wake pulse sequence found by diodes is less regular than in the toroidal model, and depends on the point of observation, but is accounted for in a simulation of fields in the fluted chamber. Attention is paid to polarization of the observed fields, and possible coherence of fields produced in adjacent bending magnets. Low frequency wakefield production appears to be mainly local in a single bend, but multibend effects cannot be excluded entirely, and could play a role in high frequency resonances. New simulation techniques have been developed, which should be invaluable in further work.

Betatron radiation based diagnostics for plasma wakefield accelerated electron beams at the SPARC_LAB test facility

NASA Astrophysics Data System (ADS)

Shpakov, V.; Anania, M. P.; Biagioni, A.; Chiadroni, E.; Cianchi, A.; Curcio, A.; Dabagov, S.; Ferrario, M.; Filippi, F.; Marocchino, A.; Paroli, B.; Pompili, R.; Rossi, A. R.; Zigler, A.

2016-09-01

Recent progress with wake-field acceleration has shown a great potential in providing high gradient acceleration fields, while the quality of the beams remains relatively poor. Precise knowledge of the beam size at the exit from the plasma and matching conditions for the externally injected beams are the key for improvement of beam quality. Betatron radiation emitted by the beam during acceleration in the plasma is a powerful tool for the transverse beam size measurement, being also non-intercepting. In this work we report on the technical solutions chosen at SPARC_LAB for such diagnostics tool, along with expected parameters of betatron radiation.

Generation of annular, high-charge electron beams at the Argonne wakefield accelerator

NASA Astrophysics Data System (ADS)

Wisniewski, E. E.; Li, C.; Gai, W.; Power, J.

2012-12-01

We present and discuss the results from the experimental generation of high-charge annular(ring-shaped)electron beams at the Argonne Wakefield Accelerator (AWA). These beams were produced by using laser masks to project annular laser profiles of various inner and outer diameters onto the photocathode of an RF gun. The ring beam is accelerated to 15 MeV, then it is imaged by means of solenoid lenses. Transverse profiles are compared for different solenoid settings. Discussion includes a comparison with Parmela simulations, some applications of high-charge ring beams,and an outline of a planned extension of this study.

LCLS X-Ray FEL Output Performance in the Presence of Highly Time-Dependent Undulator Wakefields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fawley, W.M.; /LBL, Berkeley; Bane, K.L.F.

Energy loss due to wakefields within a long undulator, if not compensated by an appropriate tapering of the magnetic field strength, can degrade the FEL process by detuning the resonant FEL frequency. The wakefields arise from the vacuum chamber wall resistivity, its surface roughness, and abrupt changes in its aperture. For LCLS parameters, the resistive-wall component is the most critical and depends upon the chamber material (e.g., Cu) and its radius. Of recent interest[1] is the so-called ''AC'' component of the resistive-wall wake which can lead to strong variations on very short timescales (e.g., {approx} 20 fs). To study themore » expected performance of the LCLS in the presence of these wakefields, we have made an extensive series of start-to-end SASE simulations with tracking codes PARMELA and ELEGANT, and time-dependent FEL simulation codes GENESIS1.3 and GINGER. We discuss the impact of the wakefield losses upon output energy, spectral bandwidth, and temporal envelope of the output FEL pulse, as well as the benefits of a partial compensation of the time-dependent wake losses obtained with a slight z-dependent taper in the undulator field. We compare the taper results to those predicted analytically[2].« less

LCLS X-Ray FEL Output Performance in the Presence of HighlyTime-Dependent Undulator Wakefields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bane, Karl L.F.; Emma, Paul; Huang, Heinz-Dieter Nuhn

Energy loss due to wakefields within a long undulator, if not compensated by an appropriate tapering of the magnetic field strength, can degrade the FEL process by detuning the resonant FEL frequency. The wakefields arise from the vacuum chamber wall resistivity, its surface roughness, and abrupt changes in its aperture. For LCLS parameters, the resistive-wall component is the most critical and depends upon the chamber material (e.g., Cu) and its radius. Of recent interest[1] is the so-called ''AC'' component of the resistive-wall wake which can lead to strong variations on very short timescales (e.g., {approx} 20 0fs). To study themore » expected performance of the LCLS in the presence of these wakefields, we have made an extensive series of start-to-end SASE simulations with tracking codes PARMELA and ELEGANT, and time-dependent FEL simulation codes GENESIS1.3 and GINGER. We discuss the impact of the wakefield losses upon output energy, spectral bandwidth, and temporal envelope of the output FEL pulse, as well as the benefits of a partial compensation of the time-dependent wake losses obtained with a slight z-dependent taper in the undulator field. We compare the taper results to those predicted analytically[2].« less

Plasma Wake-field Acceleration in the Blow-out Regime

NASA Astrophysics Data System (ADS)

Barov, Nikolai; Rosenzweig, James

1999-11-01

Recent experiments at Argonne National Laboratory, investigating the blow-out regime of the plasma wake-field accelerator, are discussed. These experiments achieved stable underdense (beam denser than the ambient plasma density) beam transport, and measured average acceleration of 25 MV/m, corresponding to peak wave fields of over 60 MVm. A comparison of the results to simulation is given, and the physics of the system is discussed. Potential for improvements in performance and achieved acceleration gradient, as well as accelerated beam quality are examined within the context of the next generation of experiments at the Fermilab Test Facility. The status of these experiments will be given.

High-sensitivity silicon ultraviolet p+-i-n avalanche photodiode using ultra-shallow boron gradient doping

DOE PAGES

Xia, Zhenyang; Zang, Kai; Liu, Dong; ...

2017-08-21

Photo detection of ultraviolet (UV) light remains a challenge since the penetration depth of UV light is limited to the nanometer scale. Therefore, the doping profile and electric field in the top nanometer range of the photo detection devices become critical. Traditional UV photodetectors usually use a constant doping profile near the semiconductor surface, resulting in a negligible electric field, which limits the photo-generated carrier collection efficiency of the photodetector. Here, we demonstrate, via the use of an optimized gradient boron doping technique, that the carrier collection efficiency and photo responsivity under the UV wavelength region have been enhanced. Moreover,more » the ultrathin p+-i-n junction shows an avalanche gain of 2800 and an ultra-low junction capacitance (sub pico-farad), indicating potential applications in the low timing jitter single photon detection area.« less

High-sensitivity silicon ultraviolet p+-i-n avalanche photodiode using ultra-shallow boron gradient doping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xia, Zhenyang; Zang, Kai; Liu, Dong

Photo detection of ultraviolet (UV) light remains a challenge since the penetration depth of UV light is limited to the nanometer scale. Therefore, the doping profile and electric field in the top nanometer range of the photo detection devices become critical. Traditional UV photodetectors usually use a constant doping profile near the semiconductor surface, resulting in a negligible electric field, which limits the photo-generated carrier collection efficiency of the photodetector. Here, we demonstrate, via the use of an optimized gradient boron doping technique, that the carrier collection efficiency and photo responsivity under the UV wavelength region have been enhanced. Moreover,more » the ultrathin p+-i-n junction shows an avalanche gain of 2800 and an ultra-low junction capacitance (sub pico-farad), indicating potential applications in the low timing jitter single photon detection area.« less

A practical approach for predicting retention time shifts due to pressure and temperature gradients in ultra-high-pressure liquid chromatography.

PubMed

Åsberg, Dennis; Chutkowski, Marcin; Leśko, Marek; Samuelsson, Jörgen; Kaczmarski, Krzysztof; Fornstedt, Torgny

2017-01-06

Large pressure gradients are generated in ultra-high-pressure liquid chromatography (UHPLC) using sub-2μm particles causing significant temperature gradients over the column due to viscous heating. These pressure and temperature gradients affect retention and ultimately result in important selectivity shifts. In this study, we developed an approach for predicting the retention time shifts due to these gradients. The approach is presented as a step-by-step procedure and it is based on empirical linear relationships describing how retention varies as a function of temperature and pressure and how the average column temperature increases with the flow rate. It requires only four experiments on standard equipment, is based on straightforward calculations, and is therefore easy to use in method development. The approach was rigorously validated against experimental data obtained with a quality control method for the active pharmaceutical ingredient omeprazole. The accuracy of retention time predictions was very good with relative errors always less than 1% and in many cases around 0.5% (n=32). Selectivity shifts observed between omeprazole and the related impurities when changing the flow rate could also be accurately predicted resulting in good estimates of the resolution between critical peak pairs. The approximations which the presented approach are based on were all justified. The retention factor as a function of pressure and temperature was studied in an experimental design while the temperature distribution in the column was obtained by solving the fundamental heat and mass balance equations for the different experimental conditions. We strongly believe that this approach is sufficiently accurate and experimentally feasible for this separation to be a valuable tool when developing a UHPLC method. After further validation with other separation systems, it could become a useful approach in UHPLC method development, especially in the pharmaceutical industry where

A preliminary design of the collinear dielectric wakefield accelerator

NASA Astrophysics Data System (ADS)

Zholents, A.; Gai, W.; Doran, S.; Lindberg, R.; Power, J. G.; Strelnikov, N.; Sun, Y.; Trakhtenberg, E.; Vasserman, I.; Jing, C.; Kanareykin, A.; Li, Y.; Gao, Q.; Shchegolkov, D. Y.; Simakov, E. I.

2016-09-01

A preliminary design of the multi-meter long collinear dielectric wakefield accelerator that achieves a highly efficient transfer of the drive bunch energy to the wakefields and to the witness bunch is considered. It is made from 0.5 m long accelerator modules containing a vacuum chamber with dielectric-lined walls, a quadrupole wiggler, an rf coupler, and BPM assembly. The single bunch breakup instability is a major limiting factor for accelerator efficiency, and the BNS damping is applied to obtain the stable multi-meter long propagation of a drive bunch. Numerical simulations using a 6D particle tracking computer code are performed and tolerances to various errors are defined.

High field terahertz pulse generation from plasma wakefield driven by tailored laser pulses

NASA Astrophysics Data System (ADS)

Chen, Zi-Yu

2013-06-01

A scheme to generate high field terahertz (THz) pulses by using tailored laser pulses interaction with a gas target is proposed. The laser wakefield based THz source is emitted from the asymmetric laser shape induced plasma transverse transient net currents. Particle-in-cell simulations show that THz emission with electric filed strength over 1 GV/cm can be obtained with incident laser at 1×1019 W/cm2 level, and the corresponding energy conversion efficiency is more than 10-4. The intensity scaling holds up to high field strengths. Such a source also has a broad tunability range in amplitude, frequency spectra, and temporal shape.

High temperature-ultra performance liquid chromatography-mass spectrometry for the metabonomic analysis of Zucker rat urine.

PubMed

Gika, Helen G; Theodoridis, Georgios; Extance, Jon; Edge, Anthony M; Wilson, Ian D

2008-08-15

The applicability and potential of using elevated temperatures and sub 2-microm porous particles in chromatography for metabonomics/metabolomics was investigated using, for the first time, solvent temperatures higher than the boiling point of water (up to 180 degrees C) and thermal gradients to reduce the use of organic solvents. Ultra performance liquid chromatography, combined with mass spectrometry, was investigated for the global metabolite profiling of the plasma and urine of normal and Zucker (fa/fa) obese rats (a well established disease animal model). "Isobaric" high temperature chromatography, where the temperature and flow rate follow a gradient program, was developed and evaluated against a conventional organic solvent gradient. LC-MS data were first examined by established chromatographic criteria in order to evaluate the chromatographic performance and next were treated by special peak picking algorithms to allow the application of multivariate statistics. These studies showed that, for urine (but not plasma), chromatography at elevated temperatures provided better results than conventional reversed-phase LC with higher peak capacity and better peak asymmetry. From a systems biology point of view, better group clustering and separation was obtained with a larger number of variables of high importance when using high temperature-ultra performance liquid chromatography (HT-UPLC) compared to conventional solvent gradients.

Theory and measurements of emittance preservation in plasma wakefield acceleration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Frederico, Joel

2016-12-01

In this dissertation, we examine the preservation and measurement of emittance in the plasma wakefield acceleration blowout regime. Plasma wakefield acceleration (PWFA) is a revolutionary approach to accelerating charged particles that has been demonstrated to have the potential for gradients orders of magnitude greater than traditional approaches. The application of PWFA to the design of a linear collider will make new high energy physics research possible, but the design parameters must first be shown to be competitive with traditional methods. Emittance preservation is necessary in the design of a linear collider in order to maximize luminosity. We examine the conditionsmore » necessary for circular symmetry in the PWFA blowout regime, and demonstrate that current proposals meet these bounds. We also present an application of beam lamentation which describes the process of beam parameter and emittance matching. We show that the emittance growth saturates as a consequence of energy spread in the beam. The initial beam parameters determine the amount of emittance growth, while the contribution of energy spread is negligible. We also present a model for ion motion in the presence of a beam that is much more dense than the plasma. By combining the model of ion motion and emittance growth, we find the emittance growth due to ion motion is minimal in the case of marginal ion motion. In addition, we present a simulation that validates the ion motion model, which is under further development to examine emittance growth of both marginal and pronounced ion motion. Finally, we present a proof-of-concept of an emittance measurement which may enable the analysis of emittance preservation in future PWFA experiments.« less

Beam manipulation for resonant plasma wakefield acceleration

NASA Astrophysics Data System (ADS)

Chiadroni, E.; Alesini, D.; Anania, M. P.; Bacci, A.; Bellaveglia, M.; Biagioni, A.; Bisesto, F. G.; Cardelli, F.; Castorina, G.; Cianchi, A.; Croia, M.; Gallo, A.; Di Giovenale, D.; Di Pirro, G.; Ferrario, M.; Filippi, F.; Giribono, A.; Marocchino, A.; Mostacci, A.; Petrarca, M.; Piersanti, L.; Pioli, S.; Pompili, R.; Romeo, S.; Rossi, A. R.; Scifo, J.; Shpakov, V.; Spataro, B.; Stella, A.; Vaccarezza, C.; Villa, F.

2017-09-01

Plasma-based acceleration has already proved the ability to reach ultra-high accelerating gradients. However the step towards the realization of a plasma-based accelerator still requires some effort to guarantee high brightness beams, stability and reliability. A significant improvement in the efficiency of PWFA has been demonstrated so far accelerating a witness bunch in the wake of a higher charge driver bunch. The transformer ratio, therefore the energy transfer from the driver to the witness beam, can be increased by resonantly exciting the plasma with a properly pre-shaped drive electron beam. Theoretical and experimental studies of beam manipulation for resonant PWFA will be presented here.

Wakefields in Coherent Synchrotron Radiation

NASA Astrophysics Data System (ADS)

Billinghurst, Brant E.; Bergstrom, J. C.; Baribeau, C.; Batten, T.; Dallin, L.; May, Tim E.; Vogt, J. M.; Wurtz, Ward A.; Warnock, Robert L.; Bizzozero, D. A.; Kramer, S.; Michaelian, K. H.

2016-06-01

When the electron bunches in a storage ring are sufficiently short the electrons act coherently producing radiation several orders of magnitude more intense than normal synchrotron radiation. This is referred to as Coherent Syncrotron Radiation (CSR). Due to the potential of CSR to provide a good source of Terahertz radiation for our users, the Canadian Light Source (CLS) has been researching the production and application of CSR. CSR has been produced at the CLS for many years, and has been used for a number of applications. However, resonances that permeate the spectrum at wavenumber intervals of 0.074 cm-1, and are highly stable under changes in the machine setup, have hampered some experiments. Analogous resonances were predicted long ago in an idealized theory. Through experiments and further calculations we elucidate the resonance and wakefield mechanisms in the CLS vacuum chamber. The wakefield is observed directly in the 30-110 GHz range by rf diodes. These results are consistent with observations made by the interferometer in the THz range. Also discussed will be some practical examples of the application of CSR for the study of condensed phase samples using both transmission and Photoacoustic techniques.

Enhancement of absorption and color contrast in ultra-thin highly absorbing optical coatings

NASA Astrophysics Data System (ADS)

Kats, Mikhail A.; Byrnes, Steven J.; Blanchard, Romain; Kolle, Mathias; Genevet, Patrice; Aizenberg, Joanna; Capasso, Federico

2013-09-01

Recently a new class of optical interference coatings was introduced which comprises ultra-thin, highly absorbing dielectric layers on metal substrates. We show that these lossy coatings can be augmented by an additional transparent subwavelength layer. We fabricated a sample comprising a gold substrate, an ultra-thin film of germanium with a thickness gradient, and several alumina films. The experimental reflectivity spectra showed that the additional alumina layer increases the color range that can be obtained, in agreement with calculations. More generally, this transparent layer can be used to enhance optical absorption, protect against erosion, or as a transparent electrode for optoelectronic devices.

Advances in high gradient normal conducting accelerator structures

DOE PAGES

Simakov, Evgenya Ivanovna; Dolgashev, Valery A.; Tantawi, Sami G.

2018-03-09

Here, this paper reviews the current state-of-the-art in understanding the phenomena of ultra-high vacuum radio-frequency (rf) breakdown in accelerating structures and the efforts to improve stable operation of the structures at accelerating gradients above 100 MV/m. Numerous studies have been conducted recently with the goal of understanding the dependence of the achievable accelerating gradients and breakdown rates on the frequency of operations, the geometry of the structure, material and method of fabrication, and operational temperature. Tests have been conducted with single standing wave accelerator cells as well as with the multi-cell traveling wave structures. Notable theoretical effort was directed atmore » understanding the physical mechanisms of the rf breakdown and its statistical behavior. Finally, the achievements presented in this paper are the result of the large continuous self-sustaining collaboration of multiple research institutions in the United States and worldwide.« less

Advances in high gradient normal conducting accelerator structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simakov, Evgenya Ivanovna; Dolgashev, Valery A.; Tantawi, Sami G.

Here, this paper reviews the current state-of-the-art in understanding the phenomena of ultra-high vacuum radio-frequency (rf) breakdown in accelerating structures and the efforts to improve stable operation of the structures at accelerating gradients above 100 MV/m. Numerous studies have been conducted recently with the goal of understanding the dependence of the achievable accelerating gradients and breakdown rates on the frequency of operations, the geometry of the structure, material and method of fabrication, and operational temperature. Tests have been conducted with single standing wave accelerator cells as well as with the multi-cell traveling wave structures. Notable theoretical effort was directed atmore » understanding the physical mechanisms of the rf breakdown and its statistical behavior. Finally, the achievements presented in this paper are the result of the large continuous self-sustaining collaboration of multiple research institutions in the United States and worldwide.« less

Effect of pulse profile and chirp on a laser wakefield generation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang Xiaomei; Shen Baifei; Ji Liangliang

2012-05-15

A laser wakefield driven by an asymmetric laser pulse with/without chirp is investigated analytically and through two-dimensional particle-in-cell simulations. For a laser pulse with an appropriate pulse length compared with the plasma wavelength, the wakefield amplitude can be enhanced by using an asymmetric un-chirped laser pulse with a fast rise time; however, the growth is small. On the other hand, the wakefield can be greatly enhanced for both positively chirped laser pulse having a fast rise time and negatively chirped laser pulse having a slow rise time. Simulations show that at the early laser-plasma interaction stage, due to the influencemore » of the fast rise time the wakefield driven by the positively chirped laser pulse is more intense than that driven by the negatively chirped laser pulse, which is in good agreement with analytical results. At a later time, since the laser pulse with positive chirp exhibits opposite evolution to the one with negative chirp when propagating in plasma, the wakefield in the latter case grows more intensely. These effects should be useful in laser wakefield acceleration experiments operating at low plasma densities.« less

Experimental measurements of rf breakdowns and deflecting gradients in mm-wave metallic accelerating structures

DOE PAGES

Dal Forno, Massimo; Dolgashev, Valery; Bowden, Gordon; ...

2016-05-03

We present an experimental study of a high-gradient metallic accelerating structure at sub-THz frequencies, where we investigated the physics of rf breakdowns. Wakefields in the structure were excited by an ultrarelativistic electron beam. We present the first quantitative measurements of gradients and metal vacuum rf breakdowns in sub-THz accelerating cavities. When the beam travels off axis, a deflecting field is induced in addition to the longitudinal field. We measured the deflecting forces by observing the displacement and changes in the shape of the electron bunch. This behavior can be exploited for subfemtosecond beam diagnostics.

Numerical Calculations of Short-Range Wakefields of Collimators

NASA Astrophysics Data System (ADS)

Ng, C. K.

2001-12-01

The performance of future linear colliders are limited by the effect of short-range collimator wakefields on the beam. The beam quality is sensitive to the positioning of collimators at the end of the linac. The determination of collimator wakefields has been difficult, largely because of the scarcity of measurement data, and of the limitation of applicability of analytical results to realistic structures. In this paper, numerical methods using codes such as MAFIA are used to determine a series of tapered collimators with rectangular apertures that have been built for studies at SLAC (Stanford Linear Accelerator Center). We will study the dependences of the wakefield on the collimator taper angle, the collimator gap as well as the bunch length. Calculations are also compared with measurements.

Collective effects on the wakefield and stopping power of an ion beam pulse in plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Ling-yu; University of Chinese Academy of Sciences, Beijing 100049; Zhao, Xiao-ying

A two-dimensional (2D) particle-in-cell simulation is carried out to study the collective effects on the wakefield and stopping power for a hydrogen ion beam pulse propagation in hydrogen plasmas. The dependence of collective effects on the beam velocity and density is obtained and discussed. For the beam velocity, it is found that the collective effects have the strongest impact on the wakefield as well as the stopping power in the case of the intermediate beam velocities, in which the stopping power is also the largest. For the beam density, it is found that at low beam densities, the collective contributionmore » to the stopping power increase linearly with the increase of the beam density, which corresponds well to the results calculated using the dielectric theory. However, at high beam densities, our results show that after reaching a maximum value, the collective contribution to the stopping power starts to decrease significantly with the increase of the beam density. Besides, at high beam densities, the wakefield loses typical V-shaped cone structures, and the wavelength of the oscillation wakefield increases as the beam density increases.« less

Beam-driven acceleration in ultra-dense plasma media

DOE PAGES

Shin, Young-Min

2014-09-15

Accelerating parameters of beam-driven wakefield acceleration in an extremely dense plasma column has been analyzed with the dynamic framed particle-in-cell plasma simulator, and compared with analytic calculations. In the model, a witness beam undergoes a TeV/m scale alternating potential gradient excited by a micro-bunched drive beam in a 10 25 m -3 and 1.6 x 10 28 m -3 plasma column. The acceleration gradient, energy gain, and transformer ratio have been extensively studied in quasi-linear, linear-, and blowout-regimes. The simulation analysis indicated that in the beam-driven acceleration system a hollow plasma channel offers 20 % higher acceleration gradient by enlargingmore » the channel radius (r) from 0.2 Ap to 0.6 .Ap in a blowout regime. This paper suggests a feasibility of TeV/m scale acceleration with a hollow crystalline structure (e.g. nanotubes) of high electron plasma density.« less

Trains of electron micro-bunches in plasma wake-field acceleration

NASA Astrophysics Data System (ADS)

Lécz, Zsolt; Andreev, Alexander; Konoplev, Ivan; Seryi, Andrei; Smith, Jonathan

2018-07-01

Plasma-based charged particle accelerators have been intensively investigated in the past three decades due to their capability to open up new horizons in accelerator science and particle physics yielding electric field accelerating gradient more than three orders of magnitudes higher than in conventional devices. At the current stage the most advanced and reliable mechanism for accelerating electrons is based on the propagation of an intense laser pulse or a relativistic electron beam in a low density gaseous target. In this paper we concentrate on the electron beam-driven plasma wake-field acceleration and demonstrate using 3D PiC simulations that a train of electron micro-bunches with ∼10 fs period can be generated behind the driving beam propagating in a density down-ramp. We will discuss the conditions and properties of the micro-bunches generated aiming at understanding and study of multi-bunch mechanism of injection. It is show that the periodicity and duration of micro-bunches can be controlled by adjusting the plasma density gradient and driving beam charge.

Directed high-power THz radiation from transverse laser wakefield excited in an electron density filament

NASA Astrophysics Data System (ADS)

Kalmykov, Serge; Englesbe, Alexander; Elle, Jennifer; Domonkos, Matthew; Schmitt-Sody, Andreas

2017-10-01

A tightly focused femtosecond, weakly relativistic laser pulse partially ionizes the ambient gas, creating a string (a ``filament'') of electron density, locally reducing the nonlinear index and compensating for the self-focusing effect caused by bound electrons. While maintaining the filament over many Rayleigh lengths, the pulse drives inside it a three-dimensional (3D) wave of charge separation - the plasma wake. If the pulse waist size is much smaller than the Langmuir wavelength, electron current in the wake is mostly transverse. Electrons, driven by the wake across the sharp radial boundary of the filament, lose coherence within 2-3 periods of wakefield oscillations, and the wake decays. The laser pulse is thus accompanied by a short-lived, almost aperiodic electron current coupled to the sharp index gradient. The comprehensive 3D hydrodynamic model shows that this structure emits a broad-band THz radiation, with the highest power emitted in the near-forward direction. The THz radiation pattern contains information on wake currents surrounding the laser pulse, thus serving as an all-optical diagnostic tool. The results are tested in cylindrical and full 3D PIC simulations using codes WAKE and EPOCH.

Self-injection of electrons in a laser-wakefield accelerator by using longitudinal density ripple

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dahiya, Deepak; Sharma, A. K.; Sajal, Vivek

By introducing a longitudinal density ripple (periodic modulation in background plasma density), we demonstrate self-injection of electrons in a laser-wakefield accelerator. The wakefield driven plasma wave, in presence of density ripple excites two side band waves of same frequency but different wave numbers. One of these side bands, having smaller phase velocity compared to wakefield driven plasma wave, preaccelerates the background plasma electrons. Significant number of these preaccelerated electrons get trapped in the laser-wakefield and further accelerated to higher energies.

Effects of the quadrupole wakefields in a passive streaker

DOE PAGES

Craievich, Paolo; Lutman, Alberto A.

2016-10-05

A novel method based on transverse wakefields has been recently proposed to characterize the temporal profile of a relativistic electron bunch. The electron bunch is streaked by the interaction with the transverse wakefield excited when the electrons travel off-axis in a device called the passive streaker. Furthermore, for the large transverse off-axis offsets required to effectively streak the electron bunch, higher order modes can be excited. The time-dependent quadrupole wakefield of the dielectric-lined structure can cause a significant enlargement of the transverse profile at the screen. Consequently, the measurement resolution is decreased also at the bunch tail. We report onmore » how the temporal profile can be effectively reconstructed also including the defocusing effect for a given transverse beam distribution at the passive streaker.« less

High-efficiency polarization conversion phase gradient metasurface for wideband anomalous reflection

NASA Astrophysics Data System (ADS)

Zhang, Jiameng; Yang, Lan; Li, Linpeng; Zhang, Tong; Li, Haihong; Wang, Qingmin; Hao, Yanan; Lei, Ming; Bi, Ke

2017-07-01

An ultra-wideband polarization conversion metasurface based on S-shaped metallic structure is designed and prepared. The simulation results show that the polarization conversion bandwidth is 14 GHz for linearly polarized normally incident electromagnetic waves and the cross-polarized reflectance is more than 99% in the range of 10.3 GHz-20.5 GHz. On the premise of high reflection efficiency, the reflective phase can be regulated by changing the geometrical parameter of the S-shaped metallic structure. A phase gradient metasurface composed of six periodically arrayed S-shaped unit cells is proposed and further demonstrated both numerically and experimentally. The specular cross-polarization reflection of the phase gradient metasurface is below -10 dB, which shows a good performance on manipulating the direction of the reflected electromagnetic waves.

Enhancement of Electron Acceleration in Laser Wakefields by Random Fields

NASA Astrophysics Data System (ADS)

Tataronis, J. A.; Petržílka, V.

1999-11-01

There is increasing evidence that intense laser pulses can accelerate electrons to high energies. The energy appears to increase with the distance over which the electrons are accelerated. This is difficult to explain by electron trapping in a single wakefield wave.^1 We demonstrate that enhanced electron acceleration can arise in inhomogeneous laser wakefields through the effects of spontaneously excited random fields. This acceleration mechanism is analogous to fast electron production by random fields near rf antennae in fusion devices and helicon plasma sources.^2 Electron acceleration in a transverse laser wave due to random field effects was recently found.^3 In the present study we solve numerically the governing equations of an ensemble of test electrons in a longitudinal electric wakefield perturbed by random fields. [1pt] Supported by the Czech grant IGA A1043701 and the U.S. DOE under grant No. DE-FG02-97ER54398. [1pt] 1. A. Pukhov and J. Meyer-ter-Vehn, in Superstrong Fields in Plasmas, AIP Conf. Proc. 426, p. 93 (1997). 2. V. Petržílka, J. A. Tataronis, et al., in Proc. Varenna - Lausanne Fusion Theory Workshop, p. 95 (1998). 3. J. Meyer-ter-Vehn and Z. M. Sheng, Phys. Plasmas 6, 641 (1999).

Applications of laser wakefield accelerator-based light sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Albert, Felicie; Thomas, Alec G. R.

Laser-wakefield accelerators (LWFAs) were proposed more than three decades ago, and while they promise to deliver compact, high energy particle accelerators, they will also provide the scientific community with novel light sources. In a LWFA, where an intense laser pulse focused onto a plasma forms an electromagnetic wave in its wake, electrons can be trapped and are now routinely accelerated to GeV energies. From terahertz radiation to gamma-rays, this article reviews light sources from relativistic electrons produced by LWFAs, and discusses their potential applications. Betatron motion, Compton scattering and undulators respectively produce x-rays or gamma-rays by oscillating relativistic electrons inmore » the wakefield behind the laser pulse, a counter-propagating laser field, or a magnetic undulator. Other LWFA-based light sources include bremsstrahlung and terahertz radiation. Here, we first evaluate the performance of each of these light sources, and compare them with more conventional approaches, including radio frequency accelerators or other laser-driven sources. We have then identified applications, which we discuss in details, in a broad range of fields: medical and biological applications, military, defense and industrial applications, and condensed matter and high energy density science.« less

Applications of laser wakefield accelerator-based light sources

DOE PAGES

Albert, Felicie; Thomas, Alec G. R.

2016-10-01

Laser-wakefield accelerators (LWFAs) were proposed more than three decades ago, and while they promise to deliver compact, high energy particle accelerators, they will also provide the scientific community with novel light sources. In a LWFA, where an intense laser pulse focused onto a plasma forms an electromagnetic wave in its wake, electrons can be trapped and are now routinely accelerated to GeV energies. From terahertz radiation to gamma-rays, this article reviews light sources from relativistic electrons produced by LWFAs, and discusses their potential applications. Betatron motion, Compton scattering and undulators respectively produce x-rays or gamma-rays by oscillating relativistic electrons inmore » the wakefield behind the laser pulse, a counter-propagating laser field, or a magnetic undulator. Other LWFA-based light sources include bremsstrahlung and terahertz radiation. Here, we first evaluate the performance of each of these light sources, and compare them with more conventional approaches, including radio frequency accelerators or other laser-driven sources. We have then identified applications, which we discuss in details, in a broad range of fields: medical and biological applications, military, defense and industrial applications, and condensed matter and high energy density science.« less

Self-consistent Simulation of Microparticle and Ion Wakefield Configuration

NASA Astrophysics Data System (ADS)

Sanford, Dustin; Brooks, Beau; Ellis, Naoki; Matthews, Lorin; Hyde, Truell

2017-10-01

In a complex plasma, positively charged ions often have a directed flow with respect to the negatively charged dust grains. The resulting interaction between the dust and the flowing plasma creates an ion wakefield downstream from the dust particles, with the resulting positive space region modifying the interaction between the grains and contributing to the observed dynamics and equilibrium structure of the system. Here we present a proof of concept method that uses a molecular dynamics simulation to model the ion wakefield allowing the dynamics of the dust particles to be determined self-consistently. The trajectory of each ion is calculated including the forces from all other ions, which are treated as ``Yukawa particles'' and shielded from thermal electrons and the forces of the charged dust particles. Both the dust grain charge and the wakefield structure are also self-consistently determined for various particle configurations. The resultant wakefield potentials are then used to provide dynamic simulations of dust particle pairs. These results will be employed to analyze the formation and dynamics of field-aligned chains in CASPER's PK4 experiment onboard the International Space Station, allowing examination of extended dust chains without the masking force of gravity. This work was supported by the National Science Foundation under Grants PHY-1414523 and PHY-1740203.

Radiation pressure injection in laser-wakefield acceleration

NASA Astrophysics Data System (ADS)

Liu, Y. L.; Kuramitsu, Y.; Isayama, S.; Chen, S. H.

2018-01-01

We investigated the injection of electrons in laser-wakefield acceleration induced by a self-modulated laser pulse by a two dimensional particle-in-cell simulation. The localized electric fields and magnetic fields are excited by the counter-streaming flows on the surface of the ion bubble, owing to the Weibel or two stream like instability. The electrons are injected into the ion bubble from the sides of it and then accelerated by the wakefield. Contrary to the conventional wave breaking model, the injection of monoenergetic electrons are mainly caused by the electromagnetic process. A simple model was proposed to address the instability, and the growth rate was verified numerically and theoretically.

High-efficiency acceleration in the laser wakefield by a linearly increasing plasma density

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dong, Kegong; Wu, Yuchi; Zhu, Bin

The acceleration length and the peak energy of the electron beam are limited by the dephasing effect in the laser wakefield acceleration with uniform plasma density. Based on 2D-3V particle in cell simulations, the effects of a linearly increasing plasma density on the electron acceleration are investigated broadly. Comparing with the uniform plasma density, because of the prolongation of the acceleration length and the gradually increasing accelerating field due to the increasing plasma density, the electron beam energy is twice higher in moderate nonlinear wakefield regime. Because of the lower plasma density, the linearly increasing plasma density can also avoidmore » the dark current caused by additional injection. At the optimal acceleration length, the electron energy can be increased from 350 MeV (uniform) to 760 MeV (linearly increasing) with the energy spread of 1.8%, the beam duration is 5 fs and the beam waist is 1.25 μm. This linearly increasing plasma density distribution can be achieved by a capillary with special gas-filled structure, and is much more suitable for experiment.« less

Mary Wakefield: Health Resources and Services Administrator. Interview.

PubMed

Wakefield, Mary

2014-06-01

Dr. Mary Wakefield is the administrator of the Health Resources and Services Administration. She came from the University of North Dakota, where she directed the Center for Rural Health. She has served as director of the Center for Health Policy, Research and Ethics at George Mason University and has worked with the World Health Organization's Global Programme on AIDS in Geneva, Switzerland. She is a fellow in the American Academy of Nursing and was elected to the Institute of Medicine of the National Academies. A native of North Dakota, Wakefield holds a doctoral degree in nursing from the University of Texas.

High flux femtosecond x-ray emission from the electron-hose instability in laser wakefield accelerators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dong, C. F.; Zhao, T. Z.; Behm, K.

Here, bright and ultrashort duration x-ray pulses can be produced by through betatron oscillations of electrons during laser wakefield acceleration (LWFA). Our experimental measurements using the Hercules laser system demonstrate a dramatic increase in x-ray flux for interaction distances beyond the depletion/dephasing lengths, where the initial electron bunch injected into the first wake bucket catches up with the laser pulse front and the laser pulse depletes. A transition from an LWFA regime to a beam-driven plasma wakefield acceleration regime consequently occurs. The drive electron bunch is susceptible to the electron-hose instability and rapidly develops large amplitude oscillations in its tail,more » which leads to greatly enhanced x-ray radiation emission. We measure the x-ray flux as a function of acceleration length using a variable length gas cell. 3D particle-in-cell simulations using a Monte Carlo synchrotron x-ray emission algorithm elucidate the time-dependent variations in the radiation emission processes.« less

High flux femtosecond x-ray emission from the electron-hose instability in laser wakefield accelerators

NASA Astrophysics Data System (ADS)

Dong, C. F.; Zhao, T. Z.; Behm, K.; Cummings, P. G.; Nees, J.; Maksimchuk, A.; Yanovsky, V.; Krushelnick, K.; Thomas, A. G. R.

2018-04-01

Bright and ultrashort duration x-ray pulses can be produced by through betatron oscillations of electrons during laser wakefield acceleration (LWFA). Our experimental measurements using the Hercules laser system demonstrate a dramatic increase in x-ray flux for interaction distances beyond the depletion/dephasing lengths, where the initial electron bunch injected into the first wake bucket catches up with the laser pulse front and the laser pulse depletes. A transition from an LWFA regime to a beam-driven plasma wakefield acceleration regime consequently occurs. The drive electron bunch is susceptible to the electron-hose instability and rapidly develops large amplitude oscillations in its tail, which leads to greatly enhanced x-ray radiation emission. We measure the x-ray flux as a function of acceleration length using a variable length gas cell. 3D particle-in-cell simulations using a Monte Carlo synchrotron x-ray emission algorithm elucidate the time-dependent variations in the radiation emission processes.

High flux femtosecond x-ray emission from the electron-hose instability in laser wakefield accelerators

DOE PAGES

Dong, C. F.; Zhao, T. Z.; Behm, K.; ...

2018-04-24

Here, bright and ultrashort duration x-ray pulses can be produced by through betatron oscillations of electrons during laser wakefield acceleration (LWFA). Our experimental measurements using the Hercules laser system demonstrate a dramatic increase in x-ray flux for interaction distances beyond the depletion/dephasing lengths, where the initial electron bunch injected into the first wake bucket catches up with the laser pulse front and the laser pulse depletes. A transition from an LWFA regime to a beam-driven plasma wakefield acceleration regime consequently occurs. The drive electron bunch is susceptible to the electron-hose instability and rapidly develops large amplitude oscillations in its tail,more » which leads to greatly enhanced x-ray radiation emission. We measure the x-ray flux as a function of acceleration length using a variable length gas cell. 3D particle-in-cell simulations using a Monte Carlo synchrotron x-ray emission algorithm elucidate the time-dependent variations in the radiation emission processes.« less

Microchip capillary gel electrophoresis using programmed field strength gradients for the ultra-fast analysis of genetically modified organisms in soybeans.

PubMed

Kim, Yun-Jeong; Chae, Joon-Seok; Chang, Jun Keun; Kang, Seong Ho

2005-08-12

We have developed a novel method for the ultra-fast analysis of genetically modified organisms (GMOs) in soybeans by microchip capillary gel electrophoresis (MCGE) using programmed field strength gradients (PFSG) in a conventional glass double-T microchip. Under the programmed electric field strength and 0.3% poly(ethylene oxide) sieving matrix, the GMO in soybeans was analyzed within only 11 s of the microchip. The MCGE-PFSG method was a program that changes the electric field strength during GMO analysis, and was also applied to the ultra-fast analysis of PCR products. Compared to MCGE using a conventional and constantly applied electric field, the MCGE-PFSG analysis generated faster results without the loss of resolving power and reproducibility for specific DNA fragments (100- and 250-bp DNA) of GM-soybeans. The MCGE-PFSG technique may prove to be a new tool in the GMO analysis due to its speed, simplicity, and high efficiency.

Energy boost in laser wakefield accelerators using sharp density transitions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Döpp, A.; Guillaume, E.; Thaury, C.

The energy gain in laser wakefield accelerators is limited by dephasing between the driving laser pulse and the highly relativistic electrons in its wake. Since this phase depends on both the driver and the cavity length, the effects of dephasing can be mitigated with appropriate tailoring of the plasma density along propagation. Preceding studies have discussed the prospects of continuous phase-locking in the linear wakefield regime. However, most experiments are performed in the highly non-linear regime and rely on self-guiding of the laser pulse. Due to the complexity of the driver evolution in this regime, it is much more difficultmore » to achieve phase locking. As an alternative, we study the scenario of rapid rephasing in sharp density transitions, as was recently demonstrated experimentally. Starting from a phenomenological model, we deduce expressions for the electron energy gain in such density profiles. The results are in accordance with particle-in-cell simulations, and we present gain estimations for single and multiple stages of rephasing.« less

Optimization of gas-filled quartz capillary discharge waveguide for high-energy laser wakefield acceleration

NASA Astrophysics Data System (ADS)

Qin, Zhiyong; Li, Wentao; Liu, Jiansheng; Liu, Jiaqi; Yu, Changhai; Wang, Wentao; Qi, Rong; Zhang, Zhijun; Fang, Ming; Feng, Ke; Wu, Ying; Ke, Lintong; Chen, Yu; Wang, Cheng; Li, Ruxin; Xu, Zhizhan

2018-04-01

A hydrogen-filled capillary discharge waveguide made of quartz is presented for high-energy laser wakefield acceleration (LWFA). The experimental parameters (discharge current and gas pressure) were optimized to mitigate ablation by a quantitative analysis of the ablation plasma density inside the hydrogen-filled quartz capillary. The ablation plasma density was obtained by combining a spectroscopic measurement method with a calibrated gas transducer. In order to obtain a controllable plasma density and mitigate the ablation as much as possible, the range of suitable parameters was investigated. The experimental results demonstrated that the ablation in the quartz capillary could be mitigated by increasing the gas pressure to ˜7.5-14.7 Torr and decreasing the discharge current to ˜70-100 A. These optimized parameters are promising for future high-energy LWFA experiments based on the quartz capillary discharge waveguide.

Dynamics of electron injection in a laser-wakefield accelerator

NASA Astrophysics Data System (ADS)

Xu, J.; Buck, A.; Chou, S.-W.; Schmid, K.; Shen, B.; Tajima, T.; Kaluza, M. C.; Veisz, L.

2017-08-01

The detailed temporal evolution of the laser-wakefield acceleration process with controlled injection, producing reproducible high-quality electron bunches, has been investigated. The localized injection of electrons into the wakefield has been realized in a simple way—called shock-front injection—utilizing a sharp drop in plasma density. Both experimental and numerical results reveal the electron injection and acceleration process as well as the electron bunch's temporal properties. The possibility to visualize the plasma wave gives invaluable spatially resolved information about the local background electron density, which in turn allows for an efficient suppression of electron self-injection before the controlled process of injection at the sharp density jump. Upper limits for the electron bunch duration of 6.6 fs FWHM, or 2.8 fs (r.m.s.) were found. These results indicate that shock-front injection not only provides stable and tunable, but also few-femtosecond short electron pulses for applications such as ultrashort radiation sources, time-resolved electron diffraction or for the seeding of further acceleration stages.

High gradient tests of metallic mm-wave accelerating structures

DOE PAGES

Dal Forno, Massimo; Dolgashev, Valery; Bowden, Gordon; ...

2017-05-10

This study explores the physics of vacuum rf breakdowns in high gradient mm-wave accelerating structures. We performed a series of experiments with 100 GHz and 200 GHz metallic accelerating structures, at the Facility for Advanced Accelerator Experimental Tests (FACET) at the SLAC National Accelerator Laboratory. This paper presents the experimental results of rf tests of 100 GHz travelling-wave accelerating structures, made of hard copper-silver alloy. The results are compared with pure hard copper structures. The rf fields were excited by the FACET ultra-relativistic electron beam. The accelerating structures have open geometries, 10 cm long, composed of two halves separated bymore » a variable gap. The rf frequency of the fundamental accelerating mode depends on the gap size and can be changed from 90 GHz to 140 GHz. The measured frequency and pulse length are consistent with our simulations. When the beam travels off-axis, a deflecting field is induced in addition to the decelerating longitudinal field. We measured the deflecting forces by observing the displacement of the electron bunch and used this measurement to verify the expected accelerating gradient. We present the first quantitative measurement of rf breakdown rates in 100 GHz copper-silver accelerating structure, which was 10 –3 per pulse, with peak electric field of 0.42 GV/m, an accelerating gradient of 127 MV/m, at a pulse length of 2.3 ns. The goal of our studies is to understand the physics of gradient limitations in order to increase the energy reach of future accelerators.« less

High gradient tests of metallic mm-wave accelerating structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dal Forno, Massimo; Dolgashev, Valery; Bowden, Gordon

This study explores the physics of vacuum rf breakdowns in high gradient mm-wave accelerating structures. We performed a series of experiments with 100 GHz and 200 GHz metallic accelerating structures, at the Facility for Advanced Accelerator Experimental Tests (FACET) at the SLAC National Accelerator Laboratory. This paper presents the experimental results of rf tests of 100 GHz travelling-wave accelerating structures, made of hard copper-silver alloy. The results are compared with pure hard copper structures. The rf fields were excited by the FACET ultra-relativistic electron beam. The accelerating structures have open geometries, 10 cm long, composed of two halves separated bymore » a variable gap. The rf frequency of the fundamental accelerating mode depends on the gap size and can be changed from 90 GHz to 140 GHz. The measured frequency and pulse length are consistent with our simulations. When the beam travels off-axis, a deflecting field is induced in addition to the decelerating longitudinal field. We measured the deflecting forces by observing the displacement of the electron bunch and used this measurement to verify the expected accelerating gradient. We present the first quantitative measurement of rf breakdown rates in 100 GHz copper-silver accelerating structure, which was 10 –3 per pulse, with peak electric field of 0.42 GV/m, an accelerating gradient of 127 MV/m, at a pulse length of 2.3 ns. The goal of our studies is to understand the physics of gradient limitations in order to increase the energy reach of future accelerators.« less

Innovative single-shot diagnostics for electrons from laser wakefield acceleration at FLAME

NASA Astrophysics Data System (ADS)

Bisesto, F. G.; Anania, M. P.; Cianchi, A.; Chiadroni, E.; Curcio, A.; Ferrario, M.; Pompili, R.; Zigler, A.

2017-07-01

Plasma wakefield acceleration is the most promising acceleration technique known nowadays, able to provide very high accelerating fields (> 100 GV/m), enabling acceleration of electrons to GeV energy in few centimeters. Here we present all the plasma related activities currently underway at SPARC_LAB exploiting the high power laser FLAME. In particular, we will give an overview of the single shot diagnostics employed: Electro Optic Sampling (EOS) for temporal measurement and Optical Transition Radiation (OTR) for an innovative one shot emittance measurements. In detail, the EOS technique has been employed to measure for the first time the longitudinal profile of electric field of fast electrons escaping from a solid target, driving the ions and protons acceleration, and to study the impact of using different target shapes. Moreover, a novel scheme for one shot emittance measurements based on OTR, developed and tested at SPARC_LAB LINAC, used in an experiment on electrons from laser wakefield acceleration still undergoing, will be shown.

Ultra High Bypass Integrated System Test

NASA Image and Video Library

2015-09-14

NASA’s Environmentally Responsible Aviation Project, in collaboration with the Federal Aviation Administration (FAA) and Pratt & Whitney, completed testing of an Ultra High Bypass Ratio Turbofan Model in the 9’ x 15’ Low Speed Wind Tunnel at NASA Glenn Research Center. The fan model is representative of the next generation of efficient and quiet Ultra High Bypass Ratio Turbofan Engine designs.

Ultra-high-pressure liquid chromatography-tandem mass spectrometry method for the determination of alkylphenols in soil.

PubMed

Wang, Jing; Pan, Hefang; Liu, Zhengzheng; Ge, Fei

2009-03-20

A novel method has been developed for the determination of alkylphenols in soil by ultra-high-pressure liquid chromatography employing small particle sizes, combined with tandem mass spectrometry. Soil samples were extracted with pressurized liquid extraction (PLE) and then cleaned with solid-phase extraction (SPE). The extracts were separated on C18 column (1.7 microm, 50 mm x 2.1mm) with a gradient elution and a mobile phase consisting of water and acetonitrile, and then detected by an electrospray ionization tandem mass spectrometry in negative ion mode with multiple reaction monitoring (MRM). Compared with traditional liquid chromatography, it took ultra-high-pressure liquid chromatography much less time to analyze alkylphenols. Additionally, the ultra-high-pressure liquid chromatography/tandem mass spectrometry method produces satisfactory reliability, sensitivity, and accuracy. The average recoveries of the three target analytes were 74.0-103.4%, with the RSD<15%. The calibration curves for alkylphenols were linear within the range of 0.01-0.4 microg/ml, with the correlation coefficients greater than 0.99. When 10 g soil sample was used for analysis, the limits of quantification (LOQs) of the three alkylphenols were all 1.0 microg/kg.

Ultra-low emittance electron beam generation using ionization injection in a plasma beatwave accelerator

NASA Astrophysics Data System (ADS)

Schroeder, Carl; Benedetti, Carlo; Esarey, Eric; Leemans, Wim

2017-10-01

Ultra-low emittance beams can be generated using ionization injection of electrons into a wakefield excited by a plasma beatwave accelerator. This all-optical method of electron beam generation uses three laser pulses of different colors. Two long-wavelength laser pulses, with frequency difference equal to the plasma frequency, resonantly drive a plasma wave without fully ionizing a gas. A short-wavelength injection laser pulse (with a small ponderomotive force and large peak electric field), co-propagating and delayed with respect to the beating long-wavelength lasers, ionizes a fraction of the remaining bound electrons at a trapped wake phase, generating an electron beam that is accelerated in the wakefield. Using the beating of long-wavelength pulses to generate the wakefield enables atomically-bound electrons to remain at low ionization potentials, reducing the required amplitude of the ionization pulse, and, hence, the initial transverse momentum and emittance of the injected electrons. An example is presented using two lines of a CO2 laser to form a plasma beatwave accelerator to drive the wake and a frequency-doubled Ti:Al2O3 laser for ionization injection. Supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

Beam-Dynamics Analysis of Long-Range Wakefield Effects on the SCRF Cavities at the Fast Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shin, Young-Min; Bishofberger, Kip; Carlsten, Bruce

Long-range wakefields in superconducting RF (SCRF) cavities create complicated effects on beam dynamics in SCRF-based FEL beamlines. The driving bunch excites effectively an infinite number of structure modes (including HOMs) which oscillate within the SCRF cavity. Couplers with loads are used to damp the HOMs. However, these HOMs can persist for long periods of time in superconducting structures, which leads to long-range wakefields. Clear understanding of the long-range wakefield effects is a critical element for risk mitigation of future SCRF accelerators such as XFEL at DESY, LCLS-II XFEL, and MaRIE XFEL. We are currently developing numerical tools for simulating long-rangemore » wakefields in SCRF accelerators and plan to experimentally verify the tools by measuring these wakefields at the Fermilab Accelerator Science and Technology (FAST) facility. This paper previews the experimental conditions at the FAST 50 MeV beamline based on the simulation results.« less

Acceleration of on-axis and ring-shaped electron beams in wakefields driven by Laguerre-Gaussian pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Guo-Bo; Key Laboratory for Laser Plasmas; Chen, Min, E-mail: minchen@sjtu.edu.cn, E-mail: yanyunma@126.com

2016-03-14

The acceleration of electron beams with multiple transverse structures in wakefields driven by Laguerre-Gaussian pulses has been studied through three-dimensional (3D) particle-in-cell simulations. Under different laser-plasma conditions, the wakefield shows different transverse structures. In general cases, the wakefield shows a donut-like structure and it accelerates the ring-shaped hollow electron beam. When a lower plasma density or a smaller laser spot size is used, besides the donut-like wakefield, a central bell-like wakefield can also be excited. The wake sets in the center of the donut-like wake. In this case, both a central on-axis electron beam and a ring-shaped electron beam aremore » simultaneously accelerated. Further, reducing the plasma density or laser spot size leads to an on-axis electron beam acceleration only. The research is beneficial for some potential applications requiring special pulse beam structures, such as positron acceleration and collimation.« less

Comparison of ultra high performance supercritical fluid chromatography, ultra high performance liquid chromatography, and gas chromatography for the separation of synthetic cathinones.

PubMed

Carnes, Stephanie; O'Brien, Stacey; Szewczak, Angelica; Tremeau-Cayel, Lauriane; Rowe, Walter F; McCord, Bruce; Lurie, Ira S

2017-09-01

A comparison of ultra high performance supercritical fluid chromatography, ultra high performance liquid chromatography, and gas chromatography for the separation of synthetic cathinones has been conducted. Nine different mixtures of bath salts were analyzed in this study. The three different chromatographic techniques were examined using a general set of controlled synthetic cathinones as well as a variety of other synthetic cathinones that exist as positional isomers. Overall 35 different synthetic cathinones were analyzed. A variety of column types and chromatographic modes were examined for developing each separation. For the ultra high performance supercritical fluid chromatography separations, analyses were performed using a series of Torus and Trefoil columns with either ammonium formate or ammonium hydroxide as additives, and methanol, ethanol or isopropanol organic solvents as modifiers. Ultra high performance liquid chromatographic separations were performed in both reversed phase and hydrophilic interaction chromatographic modes using SPP C18 and SPP HILIC columns. Gas chromatography separations were performed using an Elite-5MS capillary column. The orthogonality of ultra high performance supercritical fluid chromatography, ultra high performance liquid chromatography, and gas chromatography was examined using principal component analysis. For the best overall separation of synthetic cathinones, the use of ultra high performance supercritical fluid chromatography in combination with gas chromatography is recommended. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Terahertz-driven linear electron acceleration

PubMed Central

Nanni, Emilio A.; Huang, Wenqian R.; Hong, Kyung-Han; Ravi, Koustuban; Fallahi, Arya; Moriena, Gustavo; Dwayne Miller, R. J.; Kärtner, Franz X.

2015-01-01

The cost, size and availability of electron accelerators are dominated by the achievable accelerating gradient. Conventional high-brightness radio-frequency accelerating structures operate with 30–50 MeV m−1 gradients. Electron accelerators driven with optical or infrared sources have demonstrated accelerating gradients orders of magnitude above that achievable with conventional radio-frequency structures. However, laser-driven wakefield accelerators require intense femtosecond sources and direct laser-driven accelerators suffer from low bunch charge, sub-micron tolerances and sub-femtosecond timing requirements due to the short wavelength of operation. Here we demonstrate linear acceleration of electrons with keV energy gain using optically generated terahertz pulses. Terahertz-driven accelerating structures enable high-gradient electron/proton accelerators with simple accelerating structures, high repetition rates and significant charge per bunch. These ultra-compact terahertz accelerators with extremely short electron bunches hold great potential to have a transformative impact for free electron lasers, linear colliders, ultrafast electron diffraction, X-ray science and medical therapy with X-rays and electron beams. PMID:26439410

Terahertz-driven linear electron acceleration

DOE PAGES

Nanni, Emilio A.; Huang, Wenqian R.; Hong, Kyung-Han; ...

2015-10-06

The cost, size and availability of electron accelerators are dominated by the achievable accelerating gradient. Conventional high-brightness radio-frequency accelerating structures operate with 30–50 MeVm -1 gradients. Electron accelerators driven with optical or infrared sources have demonstrated accelerating gradients orders of magnitude above that achievable with conventional radio-frequency structures. However, laser-driven wakefield accelerators require intense femtosecond sources and direct laser-driven accelerators suffer from low bunch charge, sub-micron tolerances and sub-femtosecond timing requirements due to the short wavelength of operation. Here we demonstrate linear acceleration of electrons with keV energy gain using optically generated terahertz pulses. Terahertz-driven accelerating structures enable high-gradient electron/protonmore » accelerators with simple accelerating structures, high repetition rates and significant charge per bunch. As a result, these ultra-compact terahertz accelerators with extremely short electron bunches hold great potential to have a transformative impact for free electron lasers, linear colliders, ultrafast electron diffraction, X-ray science and medical therapy with X-rays and electron beams.« less

Hot spots and dark current in advanced plasma wakefield accelerators

DOE PAGES

Manahan, G. G.; Deng, A.; Karger, O.; ...

2016-01-29

Dark current can spoil witness bunch beam quality and acceleration efficiency in particle beam-driven plasma wakefield accelerators. In advanced schemes, hot spots generated by the drive beam or the wakefield can release electrons from higher ionization threshold levels in the plasma media. Likewise, these electrons may be trapped inside the plasma wake and will then accumulate dark current, which is generally detrimental for a clear and unspoiled plasma acceleration process. The strategies for generating clean and robust, dark current free plasma wake cavities are devised and analyzed, and crucial aspects for experimental realization of such optimized scenarios are discussed.

Towards ultra-high ductility TRIP-assisted multiphase steels controlled by strain gradient plasticity effects

NASA Astrophysics Data System (ADS)

Hatami, M. K.; Pardoen, T.; Lacroix, G.; Berke, P.; Jacques, P. J.; Massart, T. J.

2017-01-01

TRansformation Induced Plasticity (TRIP) is a very effective mechanism to increase the strain hardening capacity of multiphase steels containing a fraction of metastable austenite, leading to both high strength and large uniform elongation. Excellent performances have been reached in the past 20 years, with recent renewed interest through the development of the 3rd generation of high strength steels often involving a TRIP effect. The microstructure and composition optimization is complex due to the interplay of coupled effects on the transformation kinetics and work hardening such as phase stability, size of retained austenite grains, temperature and loading path. In particular, recent studies have shown that the TRIP effect can only be quantitatively captured for realistic microstructures if strain gradient plasticity effects are taken into account, although direct experimental validation of this claim is missing. Here, an original computational averaging scheme is developed for predicting the elastoplastic response of TRIP aided multiphase steels based on a strain gradient plasticity model. The microstructure is represented by an aggregate of many elementary unit cells involving each a fraction of retained austenite with a specified stability. The model parameters, involving the transformation kinetics, are identified based on experimental tensile tests performed at different temperatures. The model is further assessed towards original experiments, involving temperature changes during deformation. A classical size independent plasticity model is shown unable to capture the TRIP effect on the mechanical response. Conversely, the strain gradient formulation properly predicts substantial variations of the strain hardening with deformation and temperature, hence of the uniform elongation in good agreement with the experiments. A parametric study is performed to get more insight on the effect of the material length scale as well as to determine optimum transformation

Fluid simulation of relativistic electron beam driven wakefield in a cold plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bera, Ratan Kumar; Sengupta, Sudip; Das, Amita

Excitation of wakefield in a cold homogeneous plasma, driven by an ultra-relativistic electron beam is studied in one dimension using fluid simulation techniques. For a homogeneous rigid beam having density (n{sub b}) less than or equal to half the plasma density (n{sub 0}), simulation results are found to be in good agreement with the analytical work of Rosenzweig [Phys. Rev. Lett. 58, 555 (1987)]. Here, Rosenzweig's work has been analytically extended to regimes where the ratio of beam density to plasma density is greater than half and results have been verified using simulation. Further in contrast to Rosenzweig's work, ifmore » the beam is allowed to evolve in a self-consistent manner, several interesting features are observed in simulation viz. splitting of the beam into beam-lets (for l{sub b} > λ{sub p}) and compression of the beam (for l{sub b} < λ{sub p}), l{sub b} and λ{sub p}, respectively, being the initial beam length and plasma wavelength.« less

Two-color hybrid laser wakefield and direct laser accelerator

NASA Astrophysics Data System (ADS)

Zhang, Xi; Khudik, V.; Bernstein, A.; Downer, M.; Shvets, G.

2017-03-01

We propose and investigate the concept of two-color laser wakefield and direct acceleration (LWDA) scheme in the regime of moderate (10 TW scale) laser powers. The concept utilizes two unequal frequency laser pulses: the leading long-wavelength (λ0 = 0.8 µm) wakefield laser pulse driving a nonlinear plasma wake, and a trailing short-wavelength (λDLA = λ0/2) DLA laser pulse. The combination of the large electric field, yet small ponderomotive pressure of the DLA pulse is shown to be advantageous for producing a higher energy and larger charge electron beam compared with the single frequency LWDA. The sensitivity of the dual-frequency LWDA to synchronization time jitter is also reduced.

High field gradient particle accelerator

DOEpatents

Nation, J.A.; Greenwald, S.

1989-05-30

A high electric field gradient electron accelerator utilizing short duration, microwave radiation, and capable of operating at high field gradients for high energy physics applications or at reduced electric field gradients for high average current intermediate energy accelerator applications is disclosed. Particles are accelerated in a smooth bore, periodic undulating waveguide, wherein the period is so selected that the particles slip an integral number of cycles of the r.f. wave every period of the structure. This phase step of the particles produces substantially continuous acceleration in a traveling wave without transverse magnetic or other guide means for the particle. 10 figs.

High field gradient particle accelerator

DOEpatents

Nation, John A.; Greenwald, Shlomo

1989-01-01

A high electric field gradient electron accelerator utilizing short duration, microwave radiation, and capable of operating at high field gradients for high energy physics applications or at reduced electric field gradients for high average current intermediate energy accelerator applications. Particles are accelerated in a smooth bore, periodic undulating waveguide, wherein the period is so selected that the particles slip an integral number of cycles of the r.f. wave every period of the structure. This phase step of the particles produces substantially continuous acceleration in a traveling wave without transverse magnetic or other guide means for the particle.

Time-resolved measurements with streaked diffraction patterns from electrons generated in laser plasma wakefield

NASA Astrophysics Data System (ADS)

He, Zhaohan; Nees, John; Hou, Bixue; Krushelnick, Karl; Thomas, Alec; Beaurepaire, Benoît; Malka, Victor; Faure, Jérôme

2013-10-01

Femtosecond bunches of electrons with relativistic to ultra-relativistic energies can be robustly produced in laser plasma wakefield accelerators (LWFA). Scaling the electron energy down to sub-relativistic and MeV level using a millijoule laser system will make such electron source a promising candidate for ultrafast electron diffraction (UED) applications due to the intrinsic short bunch duration and perfect synchronization with the optical pump. Recent results of electron diffraction from a single crystal gold foil, using LWFA electrons driven by 8-mJ, 35-fs laser pulses at 500 Hz, will be presented. The accelerated electrons were collimated with a solenoid magnetic lens. By applying a small-angle tilt to the magnetic lens, the diffraction pattern can be streaked such that the temporal evolution is separated spatially on the detector screen after propagation. The observable time window and achievable temporal resolution are studied in pump-probe measurements of photo-induced heating on the gold foil.

Radially polarized, half-cycle, attosecond pulses from laser wakefields through coherent synchrotronlike radiation.

PubMed

Li, F Y; Sheng, Z M; Chen, M; Yu, L L; Meyer-ter-Vehn, J; Mori, W B; Zhang, J

2014-10-01

Attosecond bursts of coherent synchrotronlike radiation are found when driving ultrathin relativistic electron disks in a quasi-one-dimensional regime of wakefield acceleration, in which the laser waist is larger than the wake wavelength. The disks of overcritical density shrink radially due to focusing wakefields, thus providing the transverse currents for the emission of an intense, radially polarized, half-cycle pulse of about 100 attoseconds in duration. The electromagnetic pulse first focuses to a peak intensity (7×10(20)W/cm(2)) 10 times larger than the driving pulse and then emerges as a conical beam. Basic dynamics of the radiative process are derived analytically and in agreement with particle-in-cell simulations. By making use of gas targets instead of solids to form the ultrathin disks, this method allows for high repetition rates required for applications.

Chemical fingerprint of Ganmaoling granule by double-wavelength ultra high performance liquid chromatography and ultra high performance liquid chromatography with quadrupole time-of-flight mass spectrometry.

PubMed

Lou, Qiong; Ye, Xiaolan; Zhou, Yingyi; Li, Hua; Song, Fenyun

2015-06-01

A method incorporating double-wavelength ultra high performance liquid chromatography with quadrupole time-of-flight mass spectrometry was developed for the investigation of the chemical fingerprint of Ganmaoling granule. The chromatographic separations were performed on an ACQUITY UPLC HSS C18 column (2.1 × 50 mm, 1.8 μm) at 30°C using gradient elution with water/formic acid (1%) and acetonitrile at a flow rate of 0.4 mL/min. A total of 11 chemical constituents of Ganmaoling granule were identified from their molecular weight, UV spectra, tandem mass spectrometry data, and retention behavior by comparing the results with those of the reference standards or literature. And 25 peaks were selected as the common peaks for fingerprint analysis to evaluate the similarities among 25 batches of Ganmaoling granule. The results of principal component analysis and orthogonal projection to latent structures discriminant analysis showed that the important chemical markers that could distinguish the different batches were revealed as 4,5-di-O-caffeoylquinic acid, 3,5-di-O-caffeoylquinic acid, and 4-O-caffeoylquinic acid. This is the first report of the ultra high performance liquid chromatography chemical fingerprint and component identification of Ganmaoling granule, which could lay a foundation for further studies of Ganmaoling granule. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of Electric Field Gradient on Sub-nanometer Spatial Resolution of Tip-enhanced Raman Spectroscopy

PubMed Central

Meng, Lingyan; Yang, Zhilin; Chen, Jianing; Sun, Mengtao

2015-01-01

Tip-enhanced Raman spectroscopy (TERS) with sub-nanometer spatial resolution has been recently demonstrated experimentally. However, the physical mechanism underlying is still under discussion. Here we theoretically investigate the electric field gradient of a coupled tip-substrate system. Our calculations suggest that the ultra-high spatial resolution of TERS can be partially attributed to the electric field gradient effect owning to its tighter spatial confinement and sensitivity to the infrared (IR)-active of molecules. Particularly, in the case of TERS of flat-lying H2TBPP molecules,we find the electric field gradient enhancement is the dominating factor for the high spatial resolution, which qualitatively coincides with previous experimental report. Our theoretical study offers a new paradigm for understanding the mechanisms of the ultra-high spatial resolution demonstrated in tip-enhanced spectroscopy which is of importance but neglected. PMID:25784161

ICPP: Relativistic Plasma Physics with Ultra-Short High-Intensity Laser Pulses

NASA Astrophysics Data System (ADS)

Meyer-Ter-Vehn, Juergen

2000-10-01

Recent progress in generating ultra-short high-intensity laser pulses has opened a new branch of relativistic plasma physics, which is discussed in this talk in terms of particle-in-cell (PIC) simulations. These pulses create small plasma volumes of high-density plasma with plasma fields above 10^12 V/m and 10^8 Gauss. At intensities beyond 10^18 W/cm^2, now available from table-top systems, they drive relativistic electron currents in self-focussing plasma channels. These currents are close to the Alfven limit and allow to study relativistic current filamentation. A most remarkable feature is the generation of well collimated relativistic electron beams emerging from the channels with energies up to GeV. In dense matter they trigger cascades of gamma-rays, e^+e^- pairs, and a host of nuclear and particle processes. One of the applications may be fast ignition of compressed inertial fusion targets. Above 10^23 W/cm^2, expected to be achieved in the future, solid-density matter becomes relativistically transparent for optical light, and the acceleration of protons to multi-GeV energies is predicted in plasma layers less than 1 mm thick. These results open completely new perspectives for plasma-based accelerator schemes. Three-dimensional PIC simulations turn out to be the superior tool to explore the relativistic plasma kinetics at such intensities. Results obtained with the VLPL code [1] are presented. Different mechanisms of particle acceleration are discussed. Both laser wakefield and direct laser acceleration in plasma channels (by a mechanism similar to inverse free electron lasers) have been identified. The latter describes recent MPQ experimental results. [1] A. Pukhov, J. Plasma Physics 61, 425 - 433 (1999): Three-dimensional electromagnetic relativistic particle-in-cell code VLPL (Virtual Laser Plasma Laboratory).

Wakefield computations for a corrugated pipe as a beam dechirper for FEL applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ng, C. K.; Bane, K. L.F.

A beam “dechirper” based on a corrugated, metallic vacuum chamber has been proposed recently to cancel residual energy chirp in a beam before it enters the undulator in a linac-based X-ray FEL. Rather than the round geometry that was originally proposed, we consider a pipe composed of two parallel plates with corrugations. The advantage is that the strength of the wake effect can be tuned by adjusting the separation of the plates. The separation of the plates is on the order of millimeters, and the corrugations are fractions of a millimeter in size. The dechirper needs to be meters longmore » in order to provide sufficient longitudinal wakefield to cancel the beam chirp. Considerable computation resources are required to determine accurately the wakefield for such a long structure with small corrugation gaps. Combining the moving window technique and parallel computing using multiple processors, the time domain module in the parallel finite-element electromagnetic suite ACE3P allows efficient determination of the wakefield through convergence studies. In this paper, we will calculate the longitudinal, dipole and quadrupole wakefields for the dechirper and compare the results with those of analytical and field matching approaches.« less

Quantile Regression for Analyzing Heterogeneity in Ultra-high Dimension

PubMed Central

Wang, Lan; Wu, Yichao

2012-01-01

Ultra-high dimensional data often display heterogeneity due to either heteroscedastic variance or other forms of non-location-scale covariate effects. To accommodate heterogeneity, we advocate a more general interpretation of sparsity which assumes that only a small number of covariates influence the conditional distribution of the response variable given all candidate covariates; however, the sets of relevant covariates may differ when we consider different segments of the conditional distribution. In this framework, we investigate the methodology and theory of nonconvex penalized quantile regression in ultra-high dimension. The proposed approach has two distinctive features: (1) it enables us to explore the entire conditional distribution of the response variable given the ultra-high dimensional covariates and provides a more realistic picture of the sparsity pattern; (2) it requires substantially weaker conditions compared with alternative methods in the literature; thus, it greatly alleviates the difficulty of model checking in the ultra-high dimension. In theoretic development, it is challenging to deal with both the nonsmooth loss function and the nonconvex penalty function in ultra-high dimensional parameter space. We introduce a novel sufficient optimality condition which relies on a convex differencing representation of the penalized loss function and the subdifferential calculus. Exploring this optimality condition enables us to establish the oracle property for sparse quantile regression in the ultra-high dimension under relaxed conditions. The proposed method greatly enhances existing tools for ultra-high dimensional data analysis. Monte Carlo simulations demonstrate the usefulness of the proposed procedure. The real data example we analyzed demonstrates that the new approach reveals substantially more information compared with alternative methods. PMID:23082036

Generation of high quality electron beams via ionization injection in a plasma wakefield accelerator

NASA Astrophysics Data System (ADS)

Vafaei-Najafabadi, Navid; Joshi, Chan; E217 SLAC Collaboration

2016-10-01

Ionization injection in a beam driven plasma wakefield accelerator has been used to generate electron beams with over 30 GeV of energy in a 130 cm of lithium plasma. The experiments were performed using the 3 nC, 20.35 GeV electron beam at the FACET facility of the SLAC National Accelerator Laboratory as the driver of the wakefield. The ionization of helium atoms in the up ramp of a lithium plasma were injected into the wake and over the length of acceleration maintained an emittance on the order of 30 mm-mrad, which was an order of magnitude smaller than the drive beam, albeit with an energy spread of 10-20%. The process of ionization injection occurs due to an increase in the electric field of the drive beam as it pinches through its betatron oscillations. Thus, this energy spread is attributed to the injection region encompassing multiple betatron oscillations. In this poster, we will present evidence through OSIRIS simulations of producing an injected beam with percent level energy spread and low emittance by designing the plasma parameters appropriately, such that the ionization injection occurs over a very limited distance of one betatron cycle. Work at UCLA was supported by the NSF Grant Number PHY-1415386 and DOE Grant Number DE-SC0010064. Work at SLAC was supported by DOE contract number DE-AC02-76SF00515. Simulations used the Hoffman cluster at UCLA.

Beam-based measurements of long-range transverse wakefields in the Compact Linear Collider main-linac accelerating structure

DOE PAGES

Zha, Hao; Latina, Andrea; Grudiev, Alexej; ...

2016-01-20

The baseline design of CLIC (Compact Linear Collider) uses X-band accelerating structures for its main linacs. In order to maintain beam stability in multibunch operation, long-range transverse wakefields must be suppressed by 2 orders of magnitude between successive bunches, which are separated in time by 0.5 ns. Such strong wakefield suppression is achieved by equipping every accelerating structure cell with four damping waveguides terminated with individual rf loads. A beam-based experiment to directly measure the effectiveness of this long-range transverse wakefield and benchmark simulations was made in the FACET test facility at SLAC using a prototype CLIC accelerating structure. Furthermore,more » the experiment showed good agreement with the simulations and a strong suppression of the wakefields with an unprecedented minimum resolution of 0.1 V/(pC mm m).« less

Intrinsic advantages of packed capillaries over narrow-bore columns in very high-pressure gradient liquid chromatography.

PubMed

Gritti, Fabrice; McDonald, Thomas; Gilar, Martin

2016-06-17

250μm×100mm fused silica glass capillaries were packed with 1.8μm high-strength silica (HSS) fully porous particles. They were prepared without bulky stainless steel endfittings and metal frits, which both generate significant sample dispersion. The isocratic efficiencies and gradient peak capacities of these prototype capillary columns were measured for small molecules (n-alkanophenones) using a home-made ultra-low dispersive micro-HPLC instrument. Their resolution power was compared to that of standard 2.1mm×100mm very high-pressure liquid chromatography (vHPLC) narrow-bore columns packed with the same particles. The results show that, for the same column efficiency (25000 plates) and gradient steepness (0.04min(-1)), the peak capacity of the 250μm i.d. capillary columns is systematically 15-20% higher than that of the 2.1mm i.d. narrow-bore columns. A validated model of gradient chromatography enabled one to predict accurately the observed peak capacities of the capillary columns for non-linear solvation strength retention behavior and under isothermal conditions. Thermodynamics applied to the eluent quantified the temperature difference for the thermal gradients in both capillary and narrow-bore columns. Experimental data revealed that the gradient peak capacity is more affected by viscous heating than the column efficiency. Unlike across 2.1mm i.d. columns, the changes in eluent composition across the 250μm i.d. columns during the gradient is rapidly relaxed by transverse dispersion. The combination of (1) the absence of viscous heating and (2) the high uniformity of the eluent composition across the diameter of capillary columns explains the intrinsic advantage of capillary over narrow-bore columns in gradient vHPLC. Copyright © 2016 Elsevier B.V. All rights reserved.

Transverse oscillations in plasma wakefield experiments at FACET

NASA Astrophysics Data System (ADS)

Adli, E.; Lindstrøm, C. A.; Allen, J.; Clarke, C. I.; Frederico, J.; Gessner, S. J.; Green, S. Z.; Hogan, M. J.; Litos, M. D.; White, G. R.; Yakimenko, V.; An, W.; Clayton, C. E.; Marsh, K. A.; Mori, W. B.; Joshi, C.; Vafaei-Najafabadi, N.; Corde, S.; Lu, W.

2016-09-01

We study transverse effects in a plasma wakefield accelerator. Experimental data from FACET with asymmetry in the beam-plasma system is presented. Energy dependent centroid oscillations are observed on the accelerated part of the charge. The experimental results are compared to PIC simulations and theoretical estimates.

DOE-HEP Final Report for 2013-2016: Studies of plasma wakefields for high repetition-rate plasma collider, and Theoretical study of laser-plasma proton and ion acceleration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Katsouleas, Thomas C.; Sahai, Aakash A.

2016-08-08

There were two goals for this funded project: 1. Studies of plasma wakefields for high repetition-rate plasma collider, and 2. Theoretical study of laser-plasma proton and ion acceleration. For goal 1, an analytical model was developed to determine the ion-motion resulting from the interaction of non-linear “blow-out” wakefields excited by beam-plasma and laser-plasma interactions. This is key to understanding the state of the plasma at timescales of 1 picosecond to a few 10s of picoseconds behind the driver-energy pulse. More information can be found in the document. For goal 2, we analytically and computationally analyzed the longitudinal instabilities of themore » laser-plasma interactions at the critical layer. Specifically, the process of “Doppler-shifted Ponderomotive bunching” is significant to eliminate the very high-energy spread and understand the importance of chirping the laser pulse frequency. We intend to publish the results of the mixing process in 2-D. We intend to publish Chirp-induced transparency. More information can be found in the document.« less

Modeling Two-Stage Bunch Compression With Wakefields: Macroscopic Properties And Microbunching Instability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bosch, R.A.; Kleman, K.J.; /Wisconsin U., SRC

2011-09-08

In a two-stage compression and acceleration system, where each stage compresses a chirped bunch in a magnetic chicane, wakefields affect high-current bunches. The longitudinal wakes affect the macroscopic energy and current profiles of the compressed bunch and cause microbunching at short wavelengths. For macroscopic wavelengths, impedance formulas and tracking simulations show that the wakefields can be dominated by the resistive impedance of coherent edge radiation. For this case, we calculate the minimum initial bunch length that can be compressed without producing an upright tail in phase space and associated current spike. Formulas are also obtained for the jitter in themore » bunch arrival time downstream of the compressors that results from the bunch-to-bunch variation of current, energy, and chirp. Microbunching may occur at short wavelengths where the longitudinal space-charge wakes dominate or at longer wavelengths dominated by edge radiation. We model this range of wavelengths with frequency-dependent impedance before and after each stage of compression. The growth of current and energy modulations is described by analytic gain formulas that agree with simulations.« less

High-energy coherent terahertz radiation emitted by wide-angle electron beams from a laser-wakefield accelerator

NASA Astrophysics Data System (ADS)

Yang, Xue; Brunetti, Enrico; Jaroszynski, Dino A.

2018-04-01

High-charge electron beams produced by laser-wakefield accelerators are potentially novel, scalable sources of high-power terahertz radiation suitable for applications requiring high-intensity fields. When an intense laser pulse propagates in underdense plasma, it can generate femtosecond duration, self-injected picocoulomb electron bunches that accelerate on-axis to energies from 10s of MeV to several GeV, depending on laser intensity and plasma density. The process leading to the formation of the accelerating structure also generates non-injected, sub-picosecond duration, 1–2 MeV nanocoulomb electron beams emitted obliquely into a hollow cone around the laser propagation axis. These wide-angle beams are stable and depend weakly on laser and plasma parameters. Here we perform simulations to characterise the coherent transition radiation emitted by these beams if passed through a thin metal foil, or directly at the plasma–vacuum interface, showing that coherent terahertz radiation with 10s μJ to mJ-level energy can be produced with an optical to terahertz conversion efficiency up to 10‑4–10‑3.

Resistive wall wakefields of short bunches at cryogenic temperatures

DOE PAGES

Stupakov, G.; Bane, K. L. F.; Emma, P.; ...

2015-03-19

In this study, we present calculations of the longitudinal wakefields at cryogenic temperatures for extremely short bunches, characteristic for modern x-ray free electron lasers. The calculations are based on the equations for the surface impedance in the regime of the anomalous skin effect in metals. This paper extends and complements an earlier analysis of B. Podobedov, Phys. Rev. ST Accel. Beams 12, 044401 (2009). into the region of very high frequencies associated with bunch lengths in the micron range. We study in detail the case of a rectangular bunch distribution for parameters of interest of LCLS-II with a superconducting undulator.

Analytical model for electromagnetic radiation from a wakefield excited by intense short laser pulses in an unmagnetized plasma

NASA Astrophysics Data System (ADS)

Chen, Zi-Yu; Chen, Shi; Dan, Jia-Kun; Li, Jian-Feng; Peng, Qi-Xian

2011-10-01

A simple one-dimensional analytical model for electromagnetic emission from an unmagnetized wakefield excited by an intense short-pulse laser in the nonlinear regime has been developed in this paper. The expressions for the spectral and angular distributions of the radiation have been derived. The model suggests that the origin of the radiation can be attributed to the violent sudden acceleration of plasma electrons experiencing the accelerating potential of the laser wakefield. The radiation process could help to provide a qualitative interpretation of existing experimental results, and offers useful information for future laser wakefield experiments.

Announcing Workshop on High Gradient RF

Science.gov Websites

Cavities at Argonne National Laboratory Workshop on High Gradient RF October 7-9, 2003 Agenda Accommodation Argonne Guest House SLAC Workshop August 2000 Attendees ANL Map High energy physics and other the gradient limits of these devices. Although the limits on high fields in rf cavities have been

Betatron x-ray radiation in the self-modulated wakefield acceleration regime (Conference Presentation)

NASA Astrophysics Data System (ADS)

Albert, Felicie

2017-05-01

Betatron x-ray radiation, driven by electrons from laser-wakefield acceleration, has unique properties to probe high energy density (HED) plasmas and warm dense matter. Betatron radiation is produced when relativistic electrons oscillate in the plasma wake of a laser pulse. Its properties are similar to those of synchrotron radiation, with a 1000 fold shorter pulse. This presentation will focus on the experimental challenges and results related to the development of betatron radiation in the self modulated regime of laser wakefield acceleration. We observed multi keV Betatron x-rays from a self-modulated laser wakefield accelerator. The experiment was performed at the Jupiter Laser Facility, LLNL, by focusing the Titan short pulse beam (4-150 J, 1 ps) onto the edge of a Helium gas jet at electronic densities around 1019 cm-3. For the first time on this laser system, we used a long focal length optic, which produced a laser normalized potential a0 in the range 1-3. Under these conditions, electrons are accelerated by the plasma wave created in the wake of the light pulse. As a result, intense Raman satellites, which measured shifts depend on the electron plasma density, were observed on the laser spectrum transmitted through the target. Electrons with energies up to 200 MeV, as well as Betatron x-rays with critical energies around 20 keV, were measured. OSIRIS 2D PIC simulations confirm that the electrons gain energy both from the plasma wave and from their interaction with the laser field.

MGH-USC Human Connectome Project Datasets with Ultra-High b-Value Diffusion MRI

PubMed Central

Fan, Qiuyun; Witzel, Thomas; Nummenmaa, Aapo; Van Dijk, Koene R.A.; Van Horn, John D.; Drews, Michelle K.; Somerville, Leah H.; Sheridan, Margaret A.; Santillana, Rosario M.; Snyder, Jenna; Hedden, Trey; Shaw, Emily E.; Hollinshead, Marisa O.; Renvall, Ville; Zanzonico, Roberta; Keil, Boris; Cauley, Stephen; Polimeni, Jonathan R.; Tisdall, Dylan; Buckner, Randy L.; Wedeen, Van J.; Wald, Lawrence L.; Toga, Arthur W.; Rosen, Bruce R.

2015-01-01

The MGH-USC CONNECTOM MRI scanner housed at the Massachusetts General Hospital (MGH) is a major hardware innovation of the Human Connectome Project (HCP). The 3T CONNECTOM scanner is capable of producing magnetic field gradient of up to 300 mT/m strength for in vivo human brain imaging, which greatly shortens the time spent on diffusion encoding, and decreases the signal loss due to T2 decay. To demonstrate the capability of the novel gradient system, data of healthy adult participants were acquired for this MGH-USC Adult Diffusion Dataset (N=35), minimally preprocessed, and shared through the Laboratory of Neuro Imaging Image Data Archive (LONI IDA) and the WU-Minn Connectome Database (ConnecomeDB). Another purpose of sharing the data is to facilitate methodological studies of diffusion MRI (dMRI) analyses utilizing high diffusion contrast, which perhaps is not easily feasible with standard MR gradient system. In addition, acquisition of the MGH-Harvard-USC Lifespan Dataset is currently underway to include 120 healthy participants ranging from 8 to 90 years old, which will also be shared through LONI IDA and ConnectomeDB. Here we describe the efforts of the MGH-USC HCP consortium in acquiring and sharing the ultra-high b-value diffusion MRI data and provide a report on data preprocessing and access. We conclude with a demonstration of the example data, along with results of standard diffusion analyses, including q-ball Orientation Distribution Function (ODF) reconstruction and tractography. PMID:26364861

Ultra-high Temperature Emittance Measurements for Space and Missile Applications

NASA Technical Reports Server (NTRS)

Rogers, Jan; Crandall, David

2009-01-01

Advanced modeling and design efforts for many aerospace components require high temperature emittance data. Applications requiring emittance data include propulsion systems, radiators, aeroshells, heatshields/thermal protection systems, and leading edge surfaces. The objective of this work is to provide emittance data at ultra-high temperatures. MSFC has a new instrument for the measurement of emittance at ultra-high temperatures, the Ultra-High Temperature Emissometer System (Ultra-HITEMS). AZ Technology Inc. developed the instrument, designed to provide emittance measurements over the temperature range 700-3500K. The Ultra-HITEMS instrument measures the emittance of samples, heated by lasers, in vacuum, using a blackbody source and a Fourier Transform Spectrometer. Detectors in a Nicolet 6700 FT-IR spectrometer measure emittance over the spectral range of 0.4-25 microns. Emitted energy from the specimen and output from a Mikron M390S blackbody source at the same temperature with matched collection geometry are measured. Integrating emittance over the spectral range yields the total emittance. The ratio provides a direct measure of total hemispherical emittance. Samples are heated using lasers. Optical pyrometry provides temperature data. Optical filters prevent interference from the heating lasers. Data for Inconel 718 show excellent agreement with results from literature and ASTM 835. Measurements taken from levitated spherical specimens provide total hemispherical emittance data; measurements taken from flat specimens mounted in the chamber provide near-normal emittance data. Data from selected characterization studies will be presented. The Ultra-HITEMS technique could advance space and missile technologies by advancing the knowledge base and the technology readiness level for ultra-high temperature materials.

Simulation of Ionization Effects for High-Density Positron Drivers in future Plasma Wakefield Experiments

NASA Astrophysics Data System (ADS)

Dimitrov, D. A.; Bruhwiler, D. L.; Busby, R.; Cary, J. R.; Esarey, E.; Leemans, W.

2003-10-01

Recent particle-in-cell simulations have shown [1] that the self-fields of an electron beam driver in a plasma wakefield accelerator can tunnel ionize neutral Li, leading to plasma wake dynamics differing significantly from that of a preionized plasma. It has also been shown, for the case of a preionized plasma, that the plasma wake of a positron driver differs strongly [2] from that of an electron driver. We will present particle- in-cell simulations, using the OOPIC [3] code, showing the effects of tunneling ionization on the plasma wake generated by high-density electron and positron drivers. The results will be compared to previous work on electron drivers with tunneling ionization and positron drivers without ionization. Parameters relevant to the E-164 and E-164x experiments at SLAC will be considered. [1] D.L. Bruhwiler et al., Phys. Plasmas 10 (2003), p. 2022. [2] S. Lee et al., Phys. Rev. E 64, 045501(R) (2001). [3] D.L. Bruhwiler et al., Phys. Rev. ST-AB 4, 101302 (2001).

Magnetoelectric Transverse Gradient Sensor with High Detection Sensitivity and Low Gradient Noise

PubMed Central

2017-01-01

We report, theoretically and experimentally, the realization of a high detection performance in a novel magnetoelectric (ME) transverse gradient sensor based on the large ME effect and the magnetic field gradient (MFG) technique in a pair of magnetically-biased, electrically-shielded, and mechanically-enclosed ME composites having a transverse orientation and an axial separation. The output voltage of the gradient sensor is directly obtained from the transverse MFG-induced difference in ME voltage between the two ME composites and is calibrated against transverse MFGs to give a high detection sensitivity of 0.4–30.6 V/(T/m), a strong common-mode magnetic field noise rejection rate of <−14.5 dB, a small input-output nonlinearity of <10 ppm, and a low gradient noise of 0.16–620 nT/m/Hz in a broad frequency range of 1 Hz–170 kHz under a small baseline of 35 mm. An analysis of experimental gradient noise spectra obtained in a magnetically-unshielded laboratory environment reveals the domination of the pink (1/f) noise, dielectric loss noise, and power-frequency noise below 3 kHz, in addition to the circuit noise above 3 kHz, in the gradient sensor. The high detection performance, together with the added merit of passive and direct ME conversion by the large ME effect in the ME composites, makes the gradient sensor suitable for the passive, direct, and broadband detection of transverse MFGs. PMID:29068428

Magnetoelectric Transverse Gradient Sensor with High Detection Sensitivity and Low Gradient Noise.

PubMed

Zhang, Mingji; Or, Siu Wing

2017-10-25

We report, theoretically and experimentally, the realization of a high detection performance in a novel magnetoelectric (ME) transverse gradient sensor based on the large ME effect and the magnetic field gradient (MFG) technique in a pair of magnetically-biased, electrically-shielded, and mechanically-enclosed ME composites having a transverse orientation and an axial separation. The output voltage of the gradient sensor is directly obtained from the transverse MFG-induced difference in ME voltage between the two ME composites and is calibrated against transverse MFGs to give a high detection sensitivity of 0.4-30.6 V/(T/m), a strong common-mode magnetic field noise rejection rate of <-14.5 dB, a small input-output nonlinearity of <10 ppm, and a low gradient noise of 0.16-620 nT/m/ Hz in a broad frequency range of 1 Hz-170 kHz under a small baseline of 35 mm. An analysis of experimental gradient noise spectra obtained in a magnetically-unshielded laboratory environment reveals the domination of the pink (1/ f ) noise, dielectric loss noise, and power-frequency noise below 3 kHz, in addition to the circuit noise above 3 kHz, in the gradient sensor. The high detection performance, together with the added merit of passive and direct ME conversion by the large ME effect in the ME composites, makes the gradient sensor suitable for the passive, direct, and broadband detection of transverse MFGs.

Breaking the Attosecond, Angstrom and TV/M Field Barriers with Ultra-Fast Electron Beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rosenzweig, James; Andonian, Gerard; Fukasawa, Atsushi

2012-06-22

Recent initiatives at UCLA concerning ultra-short, GeV electron beam generation have been aimed at achieving sub-fs pulses capable of driving X-ray free-electron lasers (FELs) in single-spike mode. This use of very low Q beams may allow existing FEL injectors to produce few-100 attosecond pulses, with very high brightness. Towards this end, recent experiments at the LCLS have produced {approx}2 fs, 20 pC electron pulses. We discuss here extensions of this work, in which we seek to exploit the beam brightness in FELs, in tandem with new developments in cryogenic undulator technology, to create compact accelerator-undulator systems that can lase belowmore » 0.15 {angstrom}, or be used to permit 1.5 {angstrom} operation at 4.5 GeV. In addition, we are now developing experiments which use the present LCLS fs pulses to excite plasma wakefields exceeding 1 TV/m, permitting a table-top TeV accelerator for frontier high energy physics applications.« less

9 GeV energy gain in a beam-driven plasma wakefield accelerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Litos, M.; Adli, E.; Allen, J. M.

2016-02-15

An electron beam has gained a maximum energy of 9 GeV per particle in a 1.3 m-long electron beam-driven plasma wakefield accelerator. The amount of charge accelerated in the spectral peak was 28.3 pC, and the root-mean-square energy spread was 5.0%. The mean accelerated charge and energy gain per particle of the 215 shot data set was 115 pC and 5.3 GeV, respectively, corresponding to an acceleration gradient of 4.0 GeV m -1 at the spectral peak. Moreover, the mean energy spread of the data set was 5.1%. Our results are consistent with the extrapolation of the previously reported energymore » gain results using a shorter, 36 cm-long plasma source to within 10%, evincing a non-evolving wake structure that can propagate distances of over a meter in length. Wake-loading effects were evident in the data through strong dependencies observed between various spectral properties and the amount of accelerated charge.« less

Capturing Structural Dynamics in Crystalline Silicon Using Chirped Electrons from a Laser Wakefield Accelerator

PubMed Central

He, Z.-H.; Beaurepaire, B.; Nees, J. A.; Gallé, G.; Scott, S. A.; Pérez, J. R. Sánchez; Lagally, M. G.; Krushelnick, K.; Thomas, A. G. R.; Faure, J.

2016-01-01

Recent progress in laser wakefield acceleration has led to the emergence of a new generation of electron and X-ray sources that may have enormous benefits for ultrafast science. These novel sources promise to become indispensable tools for the investigation of structural dynamics on the femtosecond time scale, with spatial resolution on the atomic scale. Here, we demonstrate the use of laser-wakefield-accelerated electron bunches for time-resolved electron diffraction measurements of the structural dynamics of single-crystal silicon nano-membranes pumped by an ultrafast laser pulse. In our proof-of-concept study, we resolve the silicon lattice dynamics on a picosecond time scale by deflecting the momentum-time correlated electrons in the diffraction peaks with a static magnetic field to obtain the time-dependent diffraction efficiency. Further improvements may lead to femtosecond temporal resolution, with negligible pump-probe jitter being possible with future laser-wakefield-accelerator ultrafast-electron-diffraction schemes. PMID:27824086

Capturing Structural Dynamics in Crystalline Silicon Using Chirped Electrons from a Laser Wakefield Accelerator

DOE PAGES

He, Z. -H.; Beaurepaire, B.; Nees, J. A.; ...

2016-11-08

Recent progress in laser wakefield acceleration has led to the emergence of a new generation of electron and X-ray sources that may have enormous benefits for ultrafast science. These novel sources promise to become indispensable tools for the investigation of structural dynamics on the femtosecond time scale, with spatial resolution on the atomic scale. Here in this paper, we demonstrate the use of laser-wakefield-accelerated electron bunches for time-resolved electron diffraction measurements of the structural dynamics of single-crystal silicon nano-membranes pumped by an ultrafast laser pulse. In our proof-of-concept study, we resolve the silicon lattice dynamics on a picosecond time scalemore » by deflecting the momentum-time correlated electrons in the diffraction peaks with a static magnetic field to obtain the time-dependent diffraction efficiency. Further improvements may lead to femtosecond temporal resolution, with negligible pump-probe jitter being possible with future laser-wakefield-accelerator ultrafast-electron-diffraction schemes.« less

Optimization of the LCLS X-Ray FEL Output Performance in the Presence of Strong Undulator Wakefields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reiche, S.; /UCLA; Bane, K.L.F.

The Linac Coherent Light Source (LCLS) Free-Electron Laser will operate in the wavelength range of 1.5 to 15 Angstroms. Energy loss due to wakefields within the long undulator can degrade the FEL process by detuning the resonant FEL frequency. The wakefields arise from the vacuum chamber wall resistivity, its surface roughness, and abrupt changes in its aperture. For LCLS parameters, the resistive component is the most critical and depends upon the chamber material (e.g. Cu) and its radius. To study the expected performance in the presence of these wakefields, we make a series of start-to-end simulations with tracking codes PARMELAmore » and ELEGANT and time-dependent FEL simulation codes Genesis 1.3 and Ginger. We discuss the impact of the wakefield on output energy, spectral bandwidth, and temporal envelope of the output FEL pulse, as well as the benefits of a partial compensation obtained with a slight z dependent taper in the undulator field. We compare these results to those obtained by decreasing the bunch charge or increasing the vacuum chamber radius. We also compare our results to those predicted in concurrent analytical work.« less

Organic field effect transistor with ultra high amplification

NASA Astrophysics Data System (ADS)

Torricelli, Fabrizio

2016-09-01

High-gain transistors are essential for the large-scale circuit integration, high-sensitivity sensors and signal amplification in sensing systems. Unfortunately, organic field-effect transistors show limited gain, usually of the order of tens, because of the large contact resistance and channel-length modulation. Here we show organic transistors fabricated on plastic foils enabling unipolar amplifiers with ultra-gain. The proposed approach is general and opens up new opportunities for ultra-large signal amplification in organic circuits and sensors.

Laser-wakefield accelerators as hard x-ray sources for 3D medical imaging of human bone

PubMed Central

Cole, J. M.; Wood, J. C.; Lopes, N. C.; Poder, K.; Abel, R. L.; Alatabi, S.; Bryant, J. S. J.; Jin, A.; Kneip, S.; Mecseki, K.; Symes, D. R.; Mangles, S. P. D.; Najmudin, Z.

2015-01-01

A bright μm-sized source of hard synchrotron x-rays (critical energy Ecrit > 30 keV) based on the betatron oscillations of laser wakefield accelerated electrons has been developed. The potential of this source for medical imaging was demonstrated by performing micro-computed tomography of a human femoral trabecular bone sample, allowing full 3D reconstruction to a resolution below 50 μm. The use of a 1 cm long wakefield accelerator means that the length of the beamline (excluding the laser) is dominated by the x-ray imaging distances rather than the electron acceleration distances. The source possesses high peak brightness, which allows each image to be recorded with a single exposure and reduces the time required for a full tomographic scan. These properties make this an interesting laboratory source for many tomographic imaging applications. PMID:26283308

Ultra-high quality factors in superconducting niobium cavities in ambient magnetic fields up to 190 mG

DOE PAGES

Romanenko, A.; Grassellino, A.; Crawford, A. C.; ...

2014-12-10

Ambient magnetic field, if trapped in the penetration depth, leads to the residual resistance and therefore sets the limit for the achievable quality factors in superconducting niobium resonators for particle accelerators. Here, we show that a complete expulsion of the magnetic flux can be performed and leads to: (1) record quality factors Q > 2 x 10¹¹ up to accelerating gradient of 22 MV/m; (2) Q ~ 3 x 10¹⁰ at 2 K and 16 MV/m in up to 190 mG magnetic fields. This is achieved by large thermal gradients at the normal/superconducting phase front during the cooldown. Our findingsmore » open up a way to ultra-high quality factors at low temperatures and show an alternative to the sophisticated magnetic shielding implemented in modern superconducting accelerators.« less

Formal thought disorder in people at ultra-high risk of psychosis

PubMed Central

Weinstein, Sara; Stahl, Daniel; Day, Fern; Valmaggia, Lucia; Rutigliano, Grazia; De Micheli, Andrea; Fusar-Poli, Paolo; McGuire, Philip

2017-01-01

Background Formal thought disorder is a cardinal feature of psychosis. However, the extent to which formal thought disorder is evident in ultra-high-risk individuals and whether it is linked to the progression to psychosis remains unclear. Aims Examine the severity of formal thought disorder in ultra-high-risk participants and its association with future psychosis. Method The Thought and Language Index (TLI) was used to assess 24 ultra-high-risk participants, 16 people with first-episode psychosis and 13 healthy controls. Ultra-high-risk individuals were followed up for a mean duration of 7 years (s.d.=1.5) to determine the relationship between formal thought disorder at baseline and transition to psychosis. Results TLI scores were significantly greater in the ultra-high-risk group compared with the healthy control group (effect size (ES)=1.2), but lower than in people with first-episode psychosis (ES=0.8). Total and negative TLI scores were higher in ultra-high-risk individuals who developed psychosis, but this was not significant. Combining negative TLI scores with attenuated psychotic symptoms and basic symptoms predicted transition to psychosis (P=0.04; ES=1.04). Conclusions TLI is beneficial in evaluating formal thought disorder in ultra-high-risk participants, and complements existing instruments for the evaluation of psychopathology in this group. Declaration of interests None. Copyright and usage © The Royal College of Psychiatrists 2017. This is an open access article distributed under the terms of the Creative Commons Non-Commercial, No Derivatives (CC BY-NC-ND) license. PMID:28713586

Ultra High Energy Cosmic Rays: Strangelets?

NASA Astrophysics Data System (ADS)

Xu, Ren-Xin; Wu, Fei

2003-06-01

The conjecture that ultra-high-energy cosmic rays (UHECRs) are actually strangelets is discussed. Besides the reason that strangelets can do as cosmic rays beyond the Greisen-Zatsepin-Kuzmin-cutoff, another argument to support the conjecture is addressed by the study of formation of TeV-scale microscopic black holes when UHECRs bombarding bare strange stars. It is proposed that the exotic quark surface of a bare strange star could be an effective astro-laboratory in the investigations of the extra dimensions and of the detection of ultra-high-energy neutrino fluxes. The flux of neutrinos (and other point-like particles) with energy larger than 2.3×1020 eV could be expected to be smaller than 10-26 cm-2 s-1 if there are two extra spatial dimensions.

Comparative study of active plasma lenses in high-quality electron accelerator transport lines

NASA Astrophysics Data System (ADS)

van Tilborg, J.; Barber, S. K.; Benedetti, C.; Schroeder, C. B.; Isono, F.; Tsai, H.-E.; Geddes, C. G. R.; Leemans, W. P.

2018-05-01

Electrically discharged active plasma lenses (APLs) are actively pursued in compact high-brightness plasma-based accelerators due to their high-gradient, tunable, and radially symmetric focusing properties. In this manuscript, the APL is experimentally compared with a conventional quadrupole triplet, highlighting the favorable reduction in the energy dependence (chromaticity) in the transport line. Through transport simulations, it is explored how the non-uniform radial discharge current distribution leads to beam-integrated emittance degradation and a charge density reduction at focus. However, positioning an aperture at the APL entrance will significantly reduce emittance degradation without additional loss of charge in the high-quality core of the beam. An analytical model is presented that estimates the emittance degradation from a short beam driving a longitudinally varying wakefield in the APL. Optimizing laser plasma accelerator operation is discussed where emittance degradation from the non-uniform discharge current (favoring small beams inside the APL) and wakefield effects (favoring larger beam sizes) is minimized.

Comparative study of active plasma lenses in high-quality electron accelerator transport lines

DOE Office of Scientific and Technical Information (OSTI.GOV)

van Tilborg, J.; Barber, S. K.; Benedetti, C.

Electrically discharged active plasma lenses (APLs) are actively pursued in compact high-brightness plasma-based accelerators due to their high-gradient, tunable, and radially symmetric focusing properties. In this paper, the APL is experimentally compared with a conventional quadrupole triplet, highlighting the favorable reduction in the energy dependence (chromaticity) in the transport line. Through transport simulations, it is explored how the non-uniform radial discharge current distribution leads to beam-integrated emittance degradation and a charge density reduction at focus. However, positioning an aperture at the APL entrance will significantly reduce emittance degradation without additional loss of charge in the high-quality core of the beam.more » An analytical model is presented that estimates the emittance degradation from a short beam driving a longitudinally varying wakefield in the APL. Finally, optimizing laser plasma accelerator operation is discussed where emittance degradation from the non-uniform discharge current (favoring small beams inside the APL) and wakefield effects (favoring larger beam sizes) is minimized.« less

Comparative study of active plasma lenses in high-quality electron accelerator transport lines

DOE PAGES

van Tilborg, J.; Barber, S. K.; Benedetti, C.; ...

2018-03-13

Electrically discharged active plasma lenses (APLs) are actively pursued in compact high-brightness plasma-based accelerators due to their high-gradient, tunable, and radially symmetric focusing properties. In this paper, the APL is experimentally compared with a conventional quadrupole triplet, highlighting the favorable reduction in the energy dependence (chromaticity) in the transport line. Through transport simulations, it is explored how the non-uniform radial discharge current distribution leads to beam-integrated emittance degradation and a charge density reduction at focus. However, positioning an aperture at the APL entrance will significantly reduce emittance degradation without additional loss of charge in the high-quality core of the beam.more » An analytical model is presented that estimates the emittance degradation from a short beam driving a longitudinally varying wakefield in the APL. Finally, optimizing laser plasma accelerator operation is discussed where emittance degradation from the non-uniform discharge current (favoring small beams inside the APL) and wakefield effects (favoring larger beam sizes) is minimized.« less

MGH-USC Human Connectome Project datasets with ultra-high b-value diffusion MRI.

PubMed

Fan, Qiuyun; Witzel, Thomas; Nummenmaa, Aapo; Van Dijk, Koene R A; Van Horn, John D; Drews, Michelle K; Somerville, Leah H; Sheridan, Margaret A; Santillana, Rosario M; Snyder, Jenna; Hedden, Trey; Shaw, Emily E; Hollinshead, Marisa O; Renvall, Ville; Zanzonico, Roberta; Keil, Boris; Cauley, Stephen; Polimeni, Jonathan R; Tisdall, Dylan; Buckner, Randy L; Wedeen, Van J; Wald, Lawrence L; Toga, Arthur W; Rosen, Bruce R

2016-01-01

The MGH-USC CONNECTOM MRI scanner housed at the Massachusetts General Hospital (MGH) is a major hardware innovation of the Human Connectome Project (HCP). The 3T CONNECTOM scanner is capable of producing a magnetic field gradient of up to 300 mT/m strength for in vivo human brain imaging, which greatly shortens the time spent on diffusion encoding, and decreases the signal loss due to T2 decay. To demonstrate the capability of the novel gradient system, data of healthy adult participants were acquired for this MGH-USC Adult Diffusion Dataset (N=35), minimally preprocessed, and shared through the Laboratory of Neuro Imaging Image Data Archive (LONI IDA) and the WU-Minn Connectome Database (ConnectomeDB). Another purpose of sharing the data is to facilitate methodological studies of diffusion MRI (dMRI) analyses utilizing high diffusion contrast, which perhaps is not easily feasible with standard MR gradient system. In addition, acquisition of the MGH-Harvard-USC Lifespan Dataset is currently underway to include 120 healthy participants ranging from 8 to 90 years old, which will also be shared through LONI IDA and ConnectomeDB. Here we describe the efforts of the MGH-USC HCP consortium in acquiring and sharing the ultra-high b-value diffusion MRI data and provide a report on data preprocessing and access. We conclude with a demonstration of the example data, along with results of standard diffusion analyses, including q-ball Orientation Distribution Function (ODF) reconstruction and tractography. Copyright © 2015 Elsevier Inc. All rights reserved.

Operation of a high-gradient superconducting radio-frequency cavity with a non-evaporable getter pump

DOE PAGES

Ciovati, G.; Geng, R.; Lushtak, Y.; ...

2016-10-28

The use of non-evaporable getter (NEG) pumps in particle accelerators has increased significantly over the past few years because of their large pumping speed, particularly for hydrogen, compared to the size of the pump. A concern about using such pumps in superconducting radio-frequency (SRF) accelerators is the possibility of shedding particulates which could then migrate into the SRF cavities and produce field emission, therefore degrading the cavity performance. One option to mitigate such issue is to use sintered getter materials which intrinsically offer superior mechanical and particle retention properties. In this article we present the results from cryogenic RF testsmore » of a high-gradient SRF cavity after being evacuated several times with an NEG pump equipped with sintered getter disks and placed in close proximity to the cavity. Here, the results showed that the cavity performance was not affected by the pump up to the quench gradient of 34 MV/m. As a result of this study, two such NEG pumps have been installed next to a cryomodule in the CEBAF accelerator to maintain ultra-high vacuum in the SRF cryomodule and two adjacent warm girder sections.« less

Fusion: ultra-high-speed and IR image sensors

NASA Astrophysics Data System (ADS)

Etoh, T. Goji; Dao, V. T. S.; Nguyen, Quang A.; Kimata, M.

2015-08-01

Most targets of ultra-high-speed video cameras operating at more than 1 Mfps, such as combustion, crack propagation, collision, plasma, spark discharge, an air bag at a car accident and a tire under a sudden brake, generate sudden heat. Researchers in these fields require tools to measure the high-speed motion and heat simultaneously. Ultra-high frame rate imaging is achieved by an in-situ storage image sensor. Each pixel of the sensor is equipped with multiple memory elements to record a series of image signals simultaneously at all pixels. Image signals stored in each pixel are read out after an image capturing operation. In 2002, we developed an in-situ storage image sensor operating at 1 Mfps 1). However, the fill factor of the sensor was only 15% due to a light shield covering the wide in-situ storage area. Therefore, in 2011, we developed a backside illuminated (BSI) in-situ storage image sensor to increase the sensitivity with 100% fill factor and a very high quantum efficiency 2). The sensor also achieved a much higher frame rate,16.7 Mfps, thanks to the wiring on the front side with more freedom 3). The BSI structure has another advantage that it has less difficulties in attaching an additional layer on the backside, such as scintillators. This paper proposes development of an ultra-high-speed IR image sensor in combination of advanced nano-technologies for IR imaging and the in-situ storage technology for ultra-highspeed imaging with discussion on issues in the integration.

Enhanced betatron radiation by steering a laser-driven plasma wakefield with a tilted shock front

NASA Astrophysics Data System (ADS)

Yu, Changhai; Liu, Jiansheng; Wang, Wentao; Li, Wentao; Qi, Rong; Zhang, Zhijun; Qin, Zhiyong; Liu, Jiaqi; Fang, Ming; Feng, Ke; Wu, Ying; Ke, Lintong; Chen, Yu; Wang, Cheng; Xu, Yi; Leng, Yuxin; Xia, Changquan; Li, Ruxin; Xu, Zhizhan

2018-03-01

We have experimentally realized a scheme to enhance betatron radiation by manipulating transverse oscillation of electrons in a laser-driven plasma wakefield with a tilted shock front (TSF). Very brilliant betatron x-rays have been produced with significant enhancement both in photon yield and peak energy but almost maintain the e-beam energy spread and charge. Particle-in-cell simulations indicate that the accelerated electron beam (e beam) can acquire a very large transverse oscillation amplitude with an increase in more than 10-fold, after being steered into the deflected wakefield due to the refraction of the driving laser at the TSF. Spectral broadening of betatron radiation can be suppressed owing to the small variation in the peak energy of the low-energy-spread e beam in a plasma wiggler regime. It is demonstrated that the e-beam generation, refracting, and wiggling can act as a whole to realize the concurrence of monoenergetic e beams and bright x-rays in a compact laser-wakefield accelerator.

Electron self-injection due to a plasma density downramp and gas ionization in a plasma wakefield accelerator in the blowout regime

NASA Astrophysics Data System (ADS)

Yi, S. A.; D'Avignon, E. C.; Khudik, V.; Shvets, G.

2010-11-01

We study self-injection into a plasma wakefield accelerator (PWFA) in the blowout regime analytically and through particle-in-cell (PIC) simulations. We propose a new injection mechanism into a plasma wakefield accelerator, where growth of the blowout region is enabled through a slow decrease in background plasma density along the direction of propagation. Deepening of the potential well due to this growth causes a reduction of electron Hamiltonian in the co-moving frame. This reduction depends on the shape of the blowout region, its growth rate, and impact parameter of the electron. When the reduction is greater than mc^2 [1,2], the electron becomes trapped inside the bubble. We demonstrate this effect using analytic expressions for the bubble potentials [3], and estimate plasma density gradients, and beam charge and size required for injection. We also apply the injection criterion to electron trapping through gas ionization. This work is supported by the US DOE grants DE-FG02-04ER41321 and DE-FG02-07ER54945. [1] S. Kalmykov, S.A. Yi, V. Khudik, and G. Shvets, Phys. Rev. Lett. 103, 135004 (2009). [2] S.A. Yi, V. Khudik, S. Kalmykov, and G. Shvets, Plasma Phys. Contr. Fus., in press. [3] W. Lu, C. Huang, M. Zhou, M. Tzoufras et al., Phys. Plasmas 13, 056709 (2006).

Effects of Higher-Order Relativistic Nonlinearity and Wakefield During a Moderately Intense Laser Pulse Propagation in a Plasma Channel

NASA Astrophysics Data System (ADS)

Liu, Ming-Ping; Liu, Bing-Bing; Liu, San-Qiu; Zhang, Fu-Yang; Liu, Jie

2013-08-01

Using a variational approach, the propagation of a moderately intense laser pulse in a parabolic preformed plasma channel is investigated. The effects of higher-order relativistic nonlinearity (HRN) and wakefield are included. The effect of HRN serves as an additional defocusing mechanism and has the same order of magnitude in the spot size as that of the transverse wakefield (TWF). The effect of longitudinal wakefield is much larger than those of HRN and TWF for an intense laser pulse with the pulse length equaling the plasma wavelength. The catastrophic focusing of the laser spot size would be prevented in the present of HRN and then it varies with periodic focusing oscillations.

Brain MR imaging at ultra-low radiofrequency power.

PubMed

Sarkar, Subhendra N; Alsop, David C; Madhuranthakam, Ananth J; Busse, Reed F; Robson, Philip M; Rofsky, Neil M; Hackney, David B

2011-05-01

To explore the lower limits for radiofrequency (RF) power-induced specific absorption rate (SAR) achievable at 1.5 T for brain magnetic resonance (MR) imaging without loss of tissue signal or contrast present in high-SAR clinical imaging in order to create a potentially viable MR method at ultra-low RF power to image tissues containing implanted devices. An institutional review board-approved HIPAA-compliant prospective MR study design was used, with written informed consent from all subjects prior to MR sessions. Seven healthy subjects were imaged prospectively at 1.5 T with ultra-low-SAR optimized three-dimensional (3D) fast spin-echo (FSE) and fluid-attenuated inversion-recovery (FLAIR) T2-weighted sequences and an ultra-low-SAR 3D spoiled gradient-recalled acquisition in the steady state T1-weighted sequence. Corresponding high-SAR two-dimensional (2D) clinical sequences were also performed. In addition to qualitative comparisons, absolute signal-to-noise ratios (SNRs) and contrast-to-noise ratios (CNRs) for multicoil, parallel imaging acquisitions were generated by using a Monte Carlo method for quantitative comparison between ultra-low-SAR and high-SAR results. There were minor to moderate differences in the absolute tissue SNR and CNR values and in qualitative appearance of brain images obtained by using ultra-low-SAR and high-SAR techniques. High-SAR 2D T2-weighted imaging produced slightly higher SNR, while ultra-low-SAR 3D technique not only produced higher SNR for T1-weighted and FLAIR images but also higher CNRs for all three sequences for most of the brain tissues. The 3D techniques adopted here led to a decrease in the absorbed RF power by two orders of magnitude at 1.5 T, and still the image quality was preserved within clinically acceptable imaging times. RSNA, 2011

Progress of plasma wakefield self-modulation experiments at FACET

NASA Astrophysics Data System (ADS)

Adli, E.; Berglyd Olsen, V. K.; Lindstrøm, C. A.; Muggli, P.; Reimann, O.; Vieira, J. M.; Amorim, L. D.; Clarke, C. I.; Gessner, S. J.; Green, S. Z.; Hogan, M. J.; Litos, M. D.; O`Shea, B. D.; Yakimenko, V.; Clayton, C.; Marsh, K. A.; Mori, W. B.; Joshi, C.; Vafaei-Najafabadi, N.; Williams, O.

2016-09-01

Simulations and theory predict that long electron and positron beams may under favorable conditions self-modulate in plasmas. We report on the progress of experiments studying the self-modulation instability in plasma wakefield experiments at FACET. The experimental results obtained so far, while not being fully conclusive, appear to be consistent with the presence of the self-modulation instability.

[Extreme (complicated, ultra-high) refractive errors: terminological misconceptions!?

PubMed

Avetisov, S E

2018-01-01

The article reviews development mechanisms of different refractive errors accompanied by marked defocus of light rays reaching the retina. Terminology used for such ametropias includes terms extreme, ultra-high and complicated. Justification of their usage for primary ametropias, whose symptom complex is based on changes in axial eye length, is an ongoing discussion. To comply with thesaurus definitions of 'diagnosis' and 'pathogenesis', to characterize refractive and anatomical-functional disorders in patients with primary ametropias it is proposed to use the terms 'hyperaxial and hypoaxial syndromes' with elaboration of specific symptoms instead of such expressions as extreme (ultra-high) myopia and hypermetropia.

Ultra-long high-sensitivity Φ-OTDR for high spatial resolution intrusion detection of pipelines.

PubMed

Peng, Fei; Wu, Han; Jia, Xin-Hong; Rao, Yun-Jiang; Wang, Zi-Nan; Peng, Zheng-Pu

2014-06-02

An ultra-long phase-sensitive optical time domain reflectometry (Φ-OTDR) that can achieve high-sensitivity intrusion detection over 131.5km fiber with high spatial resolution of 8m is presented, which is the longest Φ-OTDR reported to date, to the best of our knowledge. It is found that the combination of distributed Raman amplification with heterodyne detection can extend the sensing distance and enhances the sensitivity substantially, leading to the realization of ultra-long Φ-OTDR with high sensitivity and spatial resolution. Furthermore, the feasibility of applying such an ultra-long Φ-OTDR to pipeline security monitoring is demonstrated and the features of intrusion signal can be extracted with improved SNR by using the wavelet detrending/denoising method proposed.

Analysis of trace halocarbon contaminants in ultra high purity helium

NASA Technical Reports Server (NTRS)

Fewell, Larry L.

1994-01-01

This study describes the analysis of ultra high purity helium. Purification studies were conducted and containment removal was effected by the utilization of solid adsorbent purge-trap systems at cryogenic temperatures. Volatile organic compounds in ultra high purity helium were adsorbed on a solid adsorbent-cryogenic trap, and thermally desorbed trace halocarbon and other contaminants were analyzed by combined gas chromatography-mass spectrometry.

The Origin of Ultra-Faint Galaxies

NASA Astrophysics Data System (ADS)

Sand, David

2017-08-01

We request 24 orbits of HST/ACS to obtain imaging in F606W and F814W of apparent tidal features in two ultra-faint dwarf galaxies: Hercules and Leo V. This will enable us to test whether the stars in ultra- faint galaxies-as a population-have been affected by Galactic tides. Most of the new dwarfs show signs of tidal interaction in ground-based photometry, several have measured ellipticities greater than 0.5, and kinematics of a subset show velocity gradients. These ubiquitous hints for tidal effects among distant dwarfs is particularly surprising and suggestive. If most ultra-faint dwarfs are disturbed by tides, then recent tests of galaxy formation in the near field have unstable foundations.HST resolution provides an opportunity to assess whether tidal features (accompanied by tentative kinematic gradients) seen in ground-based observations of Hercules and Leo V are genuine or are instead clumps of compact background galaxies masquerading as stellar debris. In Hercules, a further test is possible: searching for a distance gradient along the stretched body of the galaxy. Parallel pointings will sample similar dwarf-centric radii away from the tidal features, assuring an unambiguous result. Whether we confirm or rule out the presence of stellar loss in these objects, the consequences are important-the origin of the ultra-faint dwarfs tells us the lower limit to both galaxy formation and the number of dark matter subhalos inhabiting the Milky Way.This program is only possible with HST: its exquisite resolution can separate compact galaxies from main sequence dwarf stars at faint magnitudes, which even the best multi-band ground-based schemes struggle with.

Ultra-High Surface Speed for Metal Removal, Artillery Shell

DTIC Science & Technology

1981-07-01

TECHNICAL LIBRARY "y/a^^cr^ AD-E400 660 CONTRACTOR REPORT ARLCD-CR- 81019 ULTRA-HIGH SURFACE SPEED FOR METAL REMOVAL, ARTILLERY SHELL RICHARD F...Report ARLCD-CR- 81019 2. GOVT ACCESSION NO. 3. RECIPIENT’S CATALOG NUMBER 4. TITLE (and Subtitle) ULTRA-HIGH SURFACE SPEED FOR METAL...UNIT* tuiPPtO 1 MIL -STD-43CA i, ASTM A-274-64 EF A1SI~1340 SEHI FIN FORGING STEEL 6 RC SQ ■ IP 120093* a LIFTS 38 PCS

Ultra-low noise supercontinuum source for ultra-high resolution optical coherence tomography at 1300 nm

NASA Astrophysics Data System (ADS)

Gonzalo, I. B.; Maria, M.; Engelsholm, R. D.; Feuchter, T.; Leick, L.; Moselund, P. M.; Podoleanu, A.; Bang, O.

2018-02-01

Supercontinuum (SC) sources are of great interest for many applications due to their ultra-broad optical bandwidth, good beam quality and high power spectral density [1]. In particular, the high average power over large bandwidths makes SC light sources excellent candidates for ultra-high resolution optical coherence tomography (UHR-OCT) [2-5]. However, conventional SC sources suffer from high pulse-to-pulse intensity fluctuations as a result of the noise-sensitive nonlinear effects involved in the SC generation process [6-9]. This intensity noise from the SC source can limit the performance of OCT, resulting in a reduced signal-to-noise ratio (SNR) [10-12]. Much work has been done to reduce the noise of the SC sources for instance with fiber tapers [7,8] or increasing the repetition rate of the pump laser for averaging in the spectrometer [10,12]. An alternative approach is to use all-normal dispersion (ANDi) fibers [13,14] to generate SC light from well-known coherent nonlinear processes [15-17]. In fact, reduction of SC noise using ANDi fibers compared to anomalous dispersion SC pumped by sub-picosecond pulses has been recently demonstrated [18], but a cladding mode was used to stabilize the ANDi SC. In this work, we characterize the noise performance of a femtosecond pumped ANDi based SC and a commercial SC source in an UHR-OCT system at 1300 nm. We show that the ANDi based SC presents exceptional noise properties compared to a commercial source. An improvement of 5 dB in SNR is measured in the UHR-OCT system, and the noise behavior resembles that of a superluminiscent diode. This preliminary study is a step forward towards development of an ultra-low noise SC source at 1300 nm for ultra-high resolution OCT.

Development and characterization of plasma targets for controlled injection of electrons into laser-driven wakefields

NASA Astrophysics Data System (ADS)

Kleinwaechter, Tobias; Goldberg, Lars; Palmer, Charlotte; Schaper, Lucas; Schwinkendorf, Jan-Patrick; Osterhoff, Jens

2012-10-01

Laser-driven wakefield acceleration within capillary discharge waveguides has been used to generate high-quality electron bunches with GeV-scale energies. However, owing to fluctuations in laser and plasma conditions in combination with a difficult to control self-injection mechanism in the non-linear wakefield regime these bunches are often not reproducible and can feature large energy spreads. Specialized plasma targets with tailored density profiles offer the possibility to overcome these issues by controlling the injection and acceleration processes. This requires precise manipulation of the longitudinal density profile. Therefore our target concept is based on a capillary structure with multiple gas in- and outlets. Potential target designs are simulated using the fluid code OpenFOAM and those meeting the specified criteria are fabricated using femtosecond-laser machining of structures into sapphire plates. Density profiles are measured over a range of inlet pressures utilizing gas-density profilometry via Raman scattering and pressure calibration with longitudinal interferometry. In combination these allow absolute density mapping. Here we report the preliminary results.

Mid-infrared ultra-high-Q resonators based on fluoride crystalline materials

NASA Astrophysics Data System (ADS)

Lecaplain, C.; Javerzac-Galy, C.; Gorodetsky, M. L.; Kippenberg, T. J.

2016-11-01

The unavailability of highly transparent materials in the mid-infrared has been the main limitation in the development of ultra-sensitive molecular sensors or cavity-based spectroscopy applications. Whispering gallery mode microresonators have attained ultra-high-quality (Q) factor resonances in the near-infrared and visible. Here we report ultra-high Q factors in the mid-infrared using polished alkaline earth metal fluoride crystals. Using an uncoated chalcogenide tapered fibre as a high-ideality coupler in the mid-infrared, we study via cavity ringdown technique the losses of BaF2, CaF2, MgF2 and SrF2 microresonators. We show that MgF2 is limited by multiphonon absorption by studying the temperature dependence of the Q factor. In contrast, in SrF2 and BaF2 the lower multiphonon absorption leads to ultra-high Q factors at 4.5 μm. These values correspond to an optical finesse of , the highest value achieved for any type of mid-infrared resonator to date.

Mid-infrared ultra-high-Q resonators based on fluoride crystalline materials

PubMed Central

Lecaplain, C.; Javerzac-Galy, C.; Gorodetsky, M. L.; Kippenberg, T. J.

2016-01-01

The unavailability of highly transparent materials in the mid-infrared has been the main limitation in the development of ultra-sensitive molecular sensors or cavity-based spectroscopy applications. Whispering gallery mode microresonators have attained ultra-high-quality (Q) factor resonances in the near-infrared and visible. Here we report ultra-high Q factors in the mid-infrared using polished alkaline earth metal fluoride crystals. Using an uncoated chalcogenide tapered fibre as a high-ideality coupler in the mid-infrared, we study via cavity ringdown technique the losses of BaF2, CaF2, MgF2 and SrF2 microresonators. We show that MgF2 is limited by multiphonon absorption by studying the temperature dependence of the Q factor. In contrast, in SrF2 and BaF2 the lower multiphonon absorption leads to ultra-high Q factors at 4.5 μm. These values correspond to an optical finesse of , the highest value achieved for any type of mid-infrared resonator to date. PMID:27869119

Mid-infrared ultra-high-Q resonators based on fluoride crystalline materials.

PubMed

Lecaplain, C; Javerzac-Galy, C; Gorodetsky, M L; Kippenberg, T J

2016-11-21

The unavailability of highly transparent materials in the mid-infrared has been the main limitation in the development of ultra-sensitive molecular sensors or cavity-based spectroscopy applications. Whispering gallery mode microresonators have attained ultra-high-quality (Q) factor resonances in the near-infrared and visible. Here we report ultra-high Q factors in the mid-infrared using polished alkaline earth metal fluoride crystals. Using an uncoated chalcogenide tapered fibre as a high-ideality coupler in the mid-infrared, we study via cavity ringdown technique the losses of BaF 2 , CaF 2 , MgF 2 and SrF 2 microresonators. We show that MgF 2 is limited by multiphonon absorption by studying the temperature dependence of the Q factor. In contrast, in SrF 2 and BaF 2 the lower multiphonon absorption leads to ultra-high Q factors at 4.5 μm. These values correspond to an optical finesse of , the highest value achieved for any type of mid-infrared resonator to date.

Multi-gigaelectronvolt acceleration of positrons in a self-loaded plasma wakefield.

PubMed

Corde, S; Adli, E; Allen, J M; An, W; Clarke, C I; Clayton, C E; Delahaye, J P; Frederico, J; Gessner, S; Green, S Z; Hogan, M J; Joshi, C; Lipkowitz, N; Litos, M; Lu, W; Marsh, K A; Mori, W B; Schmeltz, M; Vafaei-Najafabadi, N; Walz, D; Yakimenko, V; Yocky, G

2015-08-27

Electrical breakdown sets a limit on the kinetic energy that particles in a conventional radio-frequency accelerator can reach. New accelerator concepts must be developed to achieve higher energies and to make future particle colliders more compact and affordable. The plasma wakefield accelerator (PWFA) embodies one such concept, in which the electric field of a plasma wake excited by a bunch of charged particles (such as electrons) is used to accelerate a trailing bunch of particles. To apply plasma acceleration to electron-positron colliders, it is imperative that both the electrons and their antimatter counterpart, the positrons, are efficiently accelerated at high fields using plasmas. Although substantial progress has recently been reported on high-field, high-efficiency acceleration of electrons in a PWFA powered by an electron bunch, such an electron-driven wake is unsuitable for the acceleration and focusing of a positron bunch. Here we demonstrate a new regime of PWFAs where particles in the front of a single positron bunch transfer their energy to a substantial number of those in the rear of the same bunch by exciting a wakefield in the plasma. In the process, the accelerating field is altered--'self-loaded'--so that about a billion positrons gain five gigaelectronvolts of energy with a narrow energy spread over a distance of just 1.3 metres. They extract about 30 per cent of the wake's energy and form a spectrally distinct bunch with a root-mean-square energy spread as low as 1.8 per cent. This ability to transfer energy efficiently from the front to the rear within a single positron bunch makes the PWFA scheme very attractive as an energy booster to an electron-positron collider.

Evaluation of 1.0 mm i.d. column performances on ultra high pressure liquid chromatography instrumentation.

PubMed

Lestremau, François; Wu, Di; Szücs, Roman

2010-07-23

The present study focuses on the evaluation of 1.0 mm i.d. (internal diameter) columns on a commercial Ultra-High Pressure system. These systems have been developed specifically to operate columns with small volumes, typically 2.1 mm i.d., by reducing extra-column volume dispersion. The use of columns with smaller i.d. results in a reduced solvent consumption and required sample volume. The evaluation of the columns was carried out with samples containing neutral and pharmaceutical compounds. In isocratic mode, the extra-column volume produced additional band broadening leading to poor performances compared to equivalent 2.1 mm i.d. columns. By increasing the length of the column, the influence of the extra-column bandspreading could be reduced and 75,000 plates were obtained when four columns were coupled. In gradient mode, the effect of the extra-column contribution on efficiency was limited and about 80% of the performance of the 2.1 mm i.d. columns was obtained. Optimum conditions in gradient mode were further investigated by changing flow rate, gradient time and column length. A different approach of the calculation of peak capacity was also considered for the comparison of the influence of these different parameters. Copyright (c) 2010 Elsevier B.V. All rights reserved.

Correcting Concomitant Gradient Distortion in Microtesla Magnetic Resonance Imaging

NASA Astrophysics Data System (ADS)

Myers, Whittier

2005-03-01

Progress in ultra-low field magnetic resonance imaging (MRI) using an untuned gradiometer coupled to a Superconducting Quantum Interference Device (SQUID) has resulted in three-dimensional images with an in-plane resolution of 2 mm. Protons in samples up to 80 mm in size were prepolarized in a 100 mT field, manipulated by ˜100 μT/m gradients for image encoding, and detected by the SQUID in the ˜65 μT precession field. Maxwell's equations prohibit a unidirectional magnetic field gradient. While the additional concomitant gradients can be neglected in high-field MRI, they distort high-resolution images of large samples taken in microtesla precession fields. We propose two methods to mitigate such distortion: raising the precession field during image encoding, and software post-processing. Both approaches are demonstrated using computer simulations and MRI images. Simulations show that the combination of these techniques can correct the concomitant gradient distortion present in a 4-mm resolution image of an object the size of a human brain with a precession field of 50 μT. Supported by USDOE.

Beyond injection: Trojan horse underdense photocathode plasma wakefield acceleration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hidding, B.; Rosenzweig, J. B.; Xi, Y.

2012-12-21

An overview on the underlying principles of the hybrid plasma wakefield acceleration scheme dubbed 'Trojan Horse' acceleration is given. The concept is based on laser-controlled release of electrons directly into a particle-beam-driven plasma blowout, paving the way for controlled, shapeable electron bunches with ultralow emittance and ultrahigh brightness. Combining the virtues of a low-ionization-threshold underdense photocathode with the GV/m-scale electric fields of a practically dephasing-free beam-driven plasma blowout, this constitutes a 4th generation electron acceleration scheme. It is applicable as a beam brightness transformer for electron bunches from LWFA and PWFA systems alike. At FACET, the proof-of-concept experiment 'E-210: Trojanmore » Horse Plasma Wakefield Acceleration' has recently been approved and is in preparation. At the same time, various LWFA facilities are currently considered to host experiments aiming at stabilizing and boosting the electron bunch output quality via a trojan horse afterburner stage. Since normalized emittance and brightness can be improved by many orders of magnitude, the scheme is an ideal candidate for light sources such as free-electron-lasers and those based on Thomson scattering and betatron radiation alike.« less

Ultra-compact Marx-type high-voltage generator

DOEpatents

Goerz, David A.; Wilson, Michael J.

2000-01-01

An ultra-compact Marx-type high-voltage generator includes individual high-performance components that are closely coupled and integrated into an extremely compact assembly. In one embodiment, a repetitively-switched, ultra-compact Marx generator includes low-profile, annular-shaped, high-voltage, ceramic capacitors with contoured edges and coplanar extended electrodes used for primary energy storage; low-profile, low-inductance, high-voltage, pressurized gas switches with compact gas envelopes suitably designed to be integrated with the annular capacitors; feed-forward, high-voltage, ceramic capacitors attached across successive switch-capacitor-switch stages to couple the necessary energy forward to sufficiently overvoltage the spark gap of the next in-line switch; optimally shaped electrodes and insulator surfaces to reduce electric field stresses in the weakest regions where dissimilar materials meet, and to spread the fields more evenly throughout the dielectric materials, allowing them to operate closer to their intrinsic breakdown levels; and uses manufacturing and assembly methods to integrate the capacitors and switches into stages that can be arranged into a low-profile Marx generator.

Wakefield Simulation of CLIC PETS Structure Using Parallel 3D Finite Element Time-Domain Solver T3P

DOE Office of Scientific and Technical Information (OSTI.GOV)

Candel, A.; Kabel, A.; Lee, L.

In recent years, SLAC's Advanced Computations Department (ACD) has developed the parallel 3D Finite Element electromagnetic time-domain code T3P. Higher-order Finite Element methods on conformal unstructured meshes and massively parallel processing allow unprecedented simulation accuracy for wakefield computations and simulations of transient effects in realistic accelerator structures. Applications include simulation of wakefield damping in the Compact Linear Collider (CLIC) power extraction and transfer structure (PETS).

Analysis of radial and longitudinal force of plasma wakefield generated by a chirped pulse laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghasemi, Leila; Afhami, Saeedeh; Eslami, Esmaeil, E-mail: eeslami@iust.ac.ir

2015-08-15

In present paper, the chirp effect of an electromagnetic pulse via an analytical model of wakefield generation is studied. Different types of chirps are employed in this study. Our results show that by the use of nonlinear chirped pulse the longitudinal wakefield and focusing force is stronger than that of linear chirped pulse. It is indicated that quadratic nonlinear chirped pulses are globally much efficient than periodic nonlinear chirped pulses. Our calculations also predict that in nonlinear chirped pulse case, the overlap of focusing and accelerating regions is broader than that achieved in linear chirped pulse.

Design Method For Ultra-High Resolution Linear CCD Imagers

NASA Astrophysics Data System (ADS)

Sheu, Larry S.; Truong, Thanh; Yuzuki, Larry; Elhatem, Abdul; Kadekodi, Narayan

1984-11-01

This paper presents the design method to achieve ultra-high resolution linear imagers. This method utilizes advanced design rules and novel staggered bilinear photo sensor arrays with quadrilinear shift registers. Design constraint in the detector arrays and shift registers are analyzed. Imager architecture to achieve ultra-high resolution is presented. The characteristics of MTF, aliasing, speed, transfer efficiency and fine photolithography requirements associated with this architecture are also discussed. A CCD imager with advanced 1.5 um minimum feature size was fabricated. It is intended as a test vehicle for the next generation small sampling pitch ultra-high resolution CCD imager. Standard double-poly, two-phase shift registers were fabricated at an 8 um pitch using the advanced design rules. A special process step that blocked the source-drain implant from the shift register area was invented. This guaranteed excellent performance of the shift registers regardless of the small poly overlaps. A charge transfer efficiency of better than 0.99995 and maximum transfer speed of 8 MHz were achieved. The imager showed excellent performance. The dark current was less than 0.2 mV/ms, saturation 250 mV, adjacent photoresponse non-uniformity ± 4% and responsivity 0.7 V/ μJ/cm2 for the 8 μm x 6 μm photosensor size. The MTF was 0.6 at 62.5 cycles/mm. These results confirm the feasibility of the next generation ultra-high resolution CCD imagers.

Design of a High Thermal Gradient Bridgman Furnace

NASA Technical Reports Server (NTRS)

LeCroy, J. E.; Popok, D. P.

1994-01-01

The Advanced Automated Directional Solidification Furnace (AADSF) is a Bridgman-Stockbarger microgravity processing facility, designed and manifested to first fly aboard the second United States Microgravity Payload (USMP-2) Space Shuttle mission. The AADSF was principally designed to produce high axial thermal gradients, and is particularly suitable for metals solidification experiments, including non-dilute alloys. To accommodate a wider range of experimental conditions, the AADSF is equipped with a reconfigurable gradient zone. The overall design of the AADSF and the relationship between gradient zone design and furnace performance are described. Parametric thermal analysis was performed and used to select gradient zone design features that fulfill the high thermal gradient requirements of the USMP-2 experiment. The thermal model and analytical procedure, and parametric results leading to the first flight gradient zone configuration, are presented. Performance for the USMP-2 flight experiment is also predicted, and analysis results are compared to test data.

Precision optical slit for high heat load or ultra high vacuum

DOEpatents

Andresen, Nord C.; DiGennaro, Richard S.; Swain, Thomas L.

1995-01-01

This invention relates generally to slits used in optics that must be precisely aligned and adjusted. The optical slits of the present invention are useful in x-ray optics, x-ray beam lines, optical systems in which the entrance slit is critical for high wavelength resolution. The invention is particularly useful in ultra high vacuum systems where lubricants are difficult to use and designs which avoid the movement of metal parts against one another are important, such as monochrometers for high wavelength resolution with ultra high vacuum systems. The invention further relates to optical systems in which temperature characteristics of the slit materials is important. The present invention yet additionally relates to precision slits wherein the opposing edges of the slit must be precisely moved relative to a center line between the edges with each edge retaining its parallel orientation with respect to the other edge and/or the center line.

Ion Motion Induced Emittance Growth of Matched Electron Beams in Plasma Wakefields.

PubMed

An, Weiming; Lu, Wei; Huang, Chengkun; Xu, Xinlu; Hogan, Mark J; Joshi, Chan; Mori, Warren B

2017-06-16

Plasma-based acceleration is being considered as the basis for building a future linear collider. Nonlinear plasma wakefields have ideal properties for accelerating and focusing electron beams. Preservation of the emittance of nano-Coulomb beams with nanometer scale matched spot sizes in these wakefields remains a critical issue due to ion motion caused by their large space charge forces. We use fully resolved quasistatic particle-in-cell simulations of electron beams in hydrogen and lithium plasmas, including when the accelerated beam has different emittances in the two transverse planes. The projected emittance initially grows and rapidly saturates with a maximum emittance growth of less than 80% in hydrogen and 20% in lithium. The use of overfocused beams is found to dramatically reduce the emittance growth. The underlying physics that leads to the lower than expected emittance growth is elucidated.

Ultra high resolution imaging of the human head at 8 tesla: 2K x 2K for Y2K.

PubMed

Robitaille, P M; Abduljalil, A M; Kangarlu, A

2000-01-01

To acquire ultra high resolution MRI images of the human brain at 8 Tesla within a clinically acceptable time frame. Gradient echo images were acquired from the human head of normal subjects using a transverse electromagnetic resonator operating in quadrature and tuned to 340 MHz. In each study, a group of six images was obtained containing a total of 208 MB of unprocessed information. Typical acquisition parameters were as follows: matrix = 2,000 x 2,000, field of view = 20 cm, slice thickness = 2 mm, number of excitations (NEX) = 1, flip angle = 45 degrees, TR = 750 ms, TE = 17 ms, receiver bandwidth = 69.4 kHz. This resulted in a total scan time of 23 minutes, an in-plane resolution of 100 microm, and a pixel volume of 0.02 mm3. The ultra high resolution images acquired in this study represent more than a 50-fold increase in in-plane resolution relative to conventional 256 x 256 images obtained with a 20 cm field of view and a 5 mm slice thickness. Nonetheless, the ultra high resolution images could be acquired both with adequate image quality and signal to noise. They revealed numerous small venous structures throughout the image plane and provided reasonable delineation between gray and white matter. The elevated signal-to-noise ratio observed in ultra high field magnetic resonance imaging can be utilized to acquire images with a level of resolution approaching the histological level under in vivo conditions. However, brain motion is likely to degrade the useful resolution. This situation may be remedied in part with cardiac gating. Nonetheless, these images represent a significant advance in our ability to examine small anatomical features with noninvasive imaging methods.

Effects of Ionization in a Laser Wakefield Accelerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

McGuffey, C.; Schumaker, W.; Matsuoka, T.

2010-11-04

Experimental results are presented from studies of the ionization injection process in laser wakefield acceleration using the Hercules laser with laser power up to 100 TW. Gas jet targets consisting of gas mixtures reduced the density threshold required for electron injection and increased the maximum beam charge. Gas mixture targets produced smooth beams even at densities which would produce severe beam breakup in pure He targets and the divergence was found to increase with gas mixture pressure.

Gradient twinned 304 stainless steels for high strength and high ductility

DOE PAGES

Chen, Aiying; Liu, Jiabin; Wang, Hongtao; ...

2016-04-23

Gradient materials often have attractive mechanical properties that outperform uniform microstructure counterparts. It remains a difficult task to investigate and compare the performance of various gradient microstructures due to the difficulty of fabrication, the wide range of length scales involved, and their respective volume percentage variations. We have investigated four types of gradient microstructures in 304 stainless steels that utilize submicrotwins, nanotwins, nanocrystalline-, ultrafine- and coarse-grains as building blocks. Tensile tests reveal that the gradient microstructure consisting of submicrotwins and nanotwins has a persistent and stable work hardening rate and yields an impressive combination of high strength and high ductility,more » leading to a toughness that is nearly 50% higher than that of the coarse-grained counterpart. Ex- and in-situ transmission electron microscopy indicates that nanoscale and submicroscale twins help to suppress and limit martensitic phase transformation via the confinement of martensite within the twin lamellar. Twinning and detwinning remain active during tensile deformation and contribute to the work hardening behavior. We discuss the advantageous properties of using submicrotwins as the main load carrier and nanotwins as the strengthening layers over those coarse and nanocrystalline grains. Furthermore, our work uncovers a new gradient design strategy to help metals and alloys achieve high strength and high ductility.« less

Generation of Ramped Current Profiles in Relativistic Electron Beams Using Wakefields in Dielectric Structures

DOE PAGES

Andonian, G.; Barber, S.; O’Shea, F. H.; ...

2017-02-03

We show that temporal pulse tailoring of charged-particle beams is essential to optimize efficiency in collinear wakefield acceleration schemes. In this Letter, we demonstrate a novel phase space manipulation method that employs a beam wakefield interaction in a dielectric structure, followed by bunch compression in a permanent magnet chicane, to longitudinally tailor the pulse shape of an electron beam. This compact, passive, approach was used to generate a nearly linearly ramped current profile in a relativistic electron beam experiment carried out at the Brookhaven National Laboratory Accelerator Test Facility. Here, we report on these experimental results including beam and wakefieldmore » diagnostics and pulse profile reconstruction techniques.« less

Two-screen single-shot electron spectrometer for laser wakefield accelerated electron beams.

PubMed

Soloviev, A A; Starodubtsev, M V; Burdonov, K F; Kostyukov, I Yu; Nerush, E N; Shaykin, A A; Khazanov, E A

2011-04-01

The laser wakefield acceleration electron beams can essentially deviate from the axis of the system, which distinguishes them greatly from beams of conventional accelerators. In case of energy measurements by means of a permanent-magnet electron spectrometer, the deviation angle can affect accuracy, especially for high energies. A two-screen single-shot electron spectrometer that correctly allows for variations of the angle of entry is considered. The spectrometer design enables enhancing accuracy of measuring narrow electron beams significantly as compared to a one-screen spectrometer with analogous magnetic field, size, and angular acceptance. © 2011 American Institute of Physics

Precision optical slit for high heat load or ultra high vacuum

DOEpatents

Andresen, N.C.; DiGennaro, R.S.; Swain, T.L.

1995-01-24

This invention relates generally to slits used in optics that must be precisely aligned and adjusted. The optical slits of the present invention are useful in x-ray optics, x-ray beam lines, optical systems in which the entrance slit is critical for high wavelength resolution. The invention is particularly useful in ultra high vacuum systems where lubricants are difficult to use and designs which avoid the movement of metal parts against one another are important, such as monochromators for high wavelength resolution with ultra high vacuum systems. The invention further relates to optical systems in which temperature characteristics of the slit materials is important. The present invention yet additionally relates to precision slits wherein the opposing edges of the slit must be precisely moved relative to a center line between the edges with each edge retaining its parallel orientation with respect to the other edge and/or the center line. 21 figures.

Ultra-high strain in epitaxial silicon carbide nanostructures utilizing residual stress amplification

NASA Astrophysics Data System (ADS)

Phan, Hoang-Phuong; Nguyen, Tuan-Khoa; Dinh, Toan; Ina, Ginnosuke; Kermany, Atieh Ranjbar; Qamar, Afzaal; Han, Jisheng; Namazu, Takahiro; Maeda, Ryutaro; Dao, Dzung Viet; Nguyen, Nam-Trung

2017-04-01

Strain engineering has attracted great attention, particularly for epitaxial films grown on a different substrate. Residual strains of SiC have been widely employed to form ultra-high frequency and high Q factor resonators. However, to date, the highest residual strain of SiC was reported to be limited to approximately 0.6%. Large strains induced into SiC could lead to several interesting physical phenomena, as well as significant improvement of resonant frequencies. We report an unprecedented nanostrain-amplifier structure with an ultra-high residual strain up to 8% utilizing the natural residual stress between epitaxial 3C-SiC and Si. In addition, the applied strain can be tuned by changing the dimensions of the amplifier structure. The possibility of introducing such a controllable and ultra-high strain will open the door to investigating the physics of SiC in large strain regimes and the development of ultra sensitive mechanical sensors.

Ion Motion Induced Emittance Growth of Matched Electron Beams in Plasma Wakefields

DOE Office of Scientific and Technical Information (OSTI.GOV)

An, Weiming; Lu, Wei; Huang, Chengkun

2017-06-14

Plasma-based acceleration is being considered as the basis for building a future linear collider. Nonlinear plasma wakefields have ideal properties for accelerating and focusing electron beams. Preservation of the emittance of nano-Coulomb beams with nanometer scale matched spot sizes in these wakefields remains a critical issue due to ion motion caused by their large space charge forces. We use fully resolved quasistatic particle-in-cell simulations of electron beams in hydrogen and lithium plasmas, including when the accelerated beam has different emittances in the two transverse planes. The projected emittance initially grows and rapidly saturates with a maximum emittance growth of lessmore » than 80% in hydrogen and 20% in lithium. The use of overfocused beams is found to dramatically reduce the emittance growth. In conclusion, the underlying physics that leads to the lower than expected emittance growth is elucidated.« less

High-power all-fiber ultra-low noise laser

NASA Astrophysics Data System (ADS)

Zhao, Jian; Guiraud, Germain; Pierre, Christophe; Floissat, Florian; Casanova, Alexis; Hreibi, Ali; Chaibi, Walid; Traynor, Nicholas; Boullet, Johan; Santarelli, Giorgio

2018-06-01

High-power ultra-low noise single-mode single-frequency lasers are in great demand for interferometric metrology. Robust, compact all-fiber lasers represent one of the most promising technologies to replace the current laser sources in use based on injection-locked ring resonators or multi-stage solid-state amplifiers. Here, a linearly polarized high-power ultra-low noise all-fiber laser is demonstrated at a power level of 100 W. Special care has been taken in the study of relative intensity noise (RIN) and its reduction. Using an optimized servo actuator to directly control the driving current of the pump laser diode, we obtain a large feedback bandwidth of up to 1.3 MHz. The RIN reaches - 160 dBc/Hz between 3 and 20 kHz.

Ultra high vacuum broad band high power microwave window

DOEpatents

Nguyen-Tuong, V.; Dylla, H.F. III

1997-11-04

An improved high vacuum microwave window has been developed that utilizes high density polyethylene coated on two sides with SiOx, SiNx, or a combination of the two. The resultant low dielectric and low loss tangent window creates a low outgassing, low permeation seal through which broad band, high power microwave energy may be passed. No matching device is necessary and the sealing technique is simple. The features of the window are broad band transmission, ultra-high vacuum compatibility with a simple sealing technique, low voltage standing wave ratio, high power transmission and low cost. 5 figs.

Ultra high vacuum broad band high power microwave window

DOEpatents

Nguyen-Tuong, Viet; Dylla, III, Henry Frederick

1997-01-01

An improved high vacuum microwave window has been developed that utilizes high density polyethylene coated on two sides with SiOx, SiNx, or a combination of the two. The resultant low dielectric and low loss tangent window creates a low outgassing, low permeation seal through which broad band, high power microwave energy may be passed. No matching device is necessary and the sealing technique is simple. The features of the window are broad band transmission, ultra-high vacuum compatibility with a simple sealing technique, low voltage standing wave ratio, high power transmission and low cost.

Disrupted latent inhibition in individuals at ultra high-risk for developing psychosis.

PubMed

Kraus, Michael; Rapisarda, Attilio; Lam, Max; Thong, Jamie Y J; Lee, Jimmy; Subramaniam, Mythily; Collinson, Simon L; Chong, Siow Ann; Keefe, Richard S E

2016-12-01

The addition of off-the-shelf cognitive measures to established prodromal criteria has resulted in limited improvement in the prediction of conversion to psychosis. Tests that assess cognitive processes central to schizophrenia might better identify those at highest risk. The latent inhibition paradigm assesses a subject's tendency to ignore irrelevant stimuli, a process integral to healthy perceptual and cognitive function that has been hypothesized to be a key deficit underlying the development of schizophrenia. In this study, 142 young people at ultra high-risk for developing psychosis and 105 controls were tested on a within-subject latent inhibition paradigm. Additionally, we later inquired about the strategy that each subject employed to complete the test, and further investigated the relationship between reported strategy and the extent of latent inhibition exhibited. Unlike controls, ultra high-risk subjects did not demonstrate a significant latent inhibition effect. This difference between groups became greater when controlling for strategy. The lack of latent inhibition effect in our ultra high-risk sample suggests that individuals at ultra high-risk for psychosis are impaired in their allocation of attentional resources based on past predictive value of repeated stimuli. This fundamental deficit in the allocation of attention may contribute to the broader array of cognitive impairments and clinical symptoms displayed by individuals at ultra high-risk for psychosis.

Search for ultra high energy astrophysical neutrinos with the ANITA experiment

NASA Astrophysics Data System (ADS)

Romero-Wolf, Andrew

2010-12-01

This work describes a search for cosmogenic neutrinos at energies above 1018 eV with the Antarctic Impulsive Transient Antenna (ANITA). ANITA is a balloon-borne radio interferometer designed to measure radio impulsive emission from particle showers produced in the Antarctic ice-sheet by ultra-high energy neutrinos (UHEnu). Flying at 37 km altitude the ANITA detector is sensitive to 1M km3 of ice and is expected to produce the highest exposure to ultra high energy neutrinos to date. The design, flight performance, and analysis of the first flight of ANITA in 2006 are the subject of this dissertation. Due to sparse anthropogenic backgrounds throughout the Antarctic continent, the ANITA analysis depends on high resolution directional reconstruction. An interferometric method was developed that not only provides high resolution but is also sensitive to very weak radio emissions. The results of ANITA provide the strongest constraints on current ultra-high energy neutrino models. In addition there was a serendipitous observation of ultra-high energy cosmic ray geosynchrotron emissions that are of distinct character from the expected neutrino signal. This thesis includes a study of the radio Cherenkov emission from ultra-high energy electromagnetic showers in ice in the time-domain. All previous simulations computed the radio pulse frequency spectrum. I developed a purely time-domain algorithm for computing radiation using the vector potentials of charged particle tracks. The results are fully consistent with previous frequency domain calculations and shed new light into the properties of the radio pulse in the time domain. The shape of the pulse in the time domain is directly related to the depth development of the excess charge in the shower and its width to the observation angle with respect to the Cherenkov direction. This information can be of great practical importance for interpreting actual data.

Imaging frontostriatal function in ultra-high-risk, early, and chronic schizophrenia during executive processing.

PubMed

Morey, Rajendra A; Inan, Seniha; Mitchell, Teresa V; Perkins, Diana O; Lieberman, Jeffrey A; Belger, Aysenil

2005-03-01

Individuals experiencing prodromal symptoms of schizophrenia (ultra-high-risk group) demonstrate impaired performance on tasks of executive function, attention, and working memory. The neurobiological underpinnings of such executive deficits in ultra-high-risk individuals remains unclear. We assessed frontal and striatal functions during a visual oddball continuous performance task, in ultra-high-risk, early, and chronic schizophrenic patients with the use of functional magnetic resonance imaging. Cross-sectional case-control design. Community; outpatient clinic. Patients Fifty-two individuals (control, n = 16; ultra-high risk, n = 10; early, n = 15; chronic, n = 11) from a referred clinical sample and age- and sex-matched control volunteers underwent scanning. Percentage of active voxels and percentage signal change calculated for the anterior cingulate gyrus (ACG), middle frontal gyrus (MFG), inferior frontal gyrus (IFG), basal ganglia, and thalamus. Performance on the visual oddball task was measured with percentage of hits and d' (a measure based on the hit rate and the false-alarm rate). The ultra-high-risk group showed significantly smaller differential activation between task-relevant and task-irrelevant stimuli in the frontal regions (ACG, IFG, MFG) than the control group. Frontostriatal activation associated with target stimuli in the early and chronic groups was significantly lower than the control group, while the ultra-high-risk group showed a trend toward the early group. Our findings suggest that prefrontal function begins to decline before the onset of syndromally defined illness and hence may represent a vulnerability marker in assessing the risk of developing psychotic disorders among ultra-high-risk individuals.

Wakefield acceleration in planetary atmospheres: A possible source of MeV electrons. The collisionless case

NASA Astrophysics Data System (ADS)

Arrayás, M.; Cubero, D.; Montanya, J.; Seviour, R.; Trueba, J. L.

2018-07-01

Intense electromagnetic pulses interacting with a plasma can create a wake of plasma oscillations. Electrons trapped in such oscillations can be accelerated under certain conditions to very high energies. We study the optimal conditions for the wakefield acceleration to produce MeV electrons in planetary plasmas under collisionless conditions. The conditions for the optimal plasma densities can be found in the Earth atmosphere at higher altitudes than 10-15 km, which are the altitudes where lightning leaders can take place.

Ultra Fast, High Rep Rate, High Voltage Spark Gap Pulser

DTIC Science & Technology

1995-07-01

current rise time. The spark gap was designed to have a coaxial geometry reducing its inductance. Provisions were made to pass flowing gas between the...ULTRA FAST, HIGH REP RATE, HIGH VOLTAGE SPARK GAP PULSER Robert A. Pastore Jr., Lawrence E. Kingsley, Kevin Fonda, Erik Lenzing Electrophysics and...Modeling Branch AMSRL-PS-EA Tel.: (908)-532-0271 FAX: (908)-542-3348 U.S. Army Research Laboratory Physical Sciences Directorate Ft. Monmouth

Fast and sensitive analysis of beta blockers by ultra-high-performance liquid chromatography coupled with ultra-high-resolution TOF mass spectrometry.

PubMed

Tomková, Jana; Ondra, Peter; Kocianová, Eva; Václavík, Jan

2017-07-01

This paper presents a method for the determination of acebutolol, betaxolol, bisoprolol, metoprolol, nebivolol and sotalol in human serum by liquid-liquid extraction and ultra-high-performance liquid chromatography coupled with ultra-high-resolution TOF mass spectrometry. After liquid-liquid extraction, beta blockers were separated on a reverse-phase analytical column (Acclaim RS 120; 100 × 2.1 mm, 2.2 μm). The total run time was 6 min for each sample. Linearity, limit of detection, limit of quantification, matrix effects, specificity, precision, accuracy, recovery and sample stability were evaluated. The method was successfully applied to the therapeutic drug monitoring of 108 patients with hypertension. This method was also used for determination of beta blockers in 33 intoxicated patients. Copyright © 2016 John Wiley & Sons, Ltd.

Quasi-stable injection channels in a wakefield accelerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wiltshire-Turkay, Mara; Farmer, John P.; Pukhov, Alexander

2016-05-15

The influence of initial position on the acceleration of externally injected electrons in a plasma wakefield is investigated. Test-particle simulations show previously unobserved complex structure in the parameter space, with quasi-stable injection channels forming for particles injected in narrow regions away from the wake centre. Particles injected into these channels remain in the wake for a considerable time after dephasing and as a result achieve significantly higher energy than their neighbours. The result is relevant to both the planning and optimisation of experiments making use of external injection.

High-quality electron beam generation and bright betatron radiation from a cascaded laser wakefield accelerator (Conference Presentation)

NASA Astrophysics Data System (ADS)

Liu, Jiansheng; Wang, Wentao; Li, Wentao; Qi, Rong; Zhang, Zhijun; Yu, Changhai; Wang, Cheng; Liu, Jiaqi; Qing, Zhiyong; Ming, Fang; Xu, Yi; Leng, Yuxin; Li, Ruxin; Xu, Zhizhan

2017-05-01

One of the major goals of developing laser wakefiled accelerators (LWFAs) is to produce compact high-energy electron beam (e-beam) sources, which are expected to be applied in developing compact x-ray free-electron lasers and monoenergetic gamma-ray sources. Although LWFAs have been demonstrated to generate multi-GeV e-beams, to date they are still failed to produce high quality e beams with several essential properties (narrow energy spread, small transverse emittance and high beam charge) achieved simultaneously. Here we report on the demonstration of a high-quality cascaded LWFA experimentally via manipulating electron injection, seeding in different periods of the wakefield, as well as controlling energy chirp for the compression of energy spread. The cascaded LWFA was powered by a 1-Hz 200-TW femtosecond laser facility at SIOM. High-brightness e beams with peak energies in the range of 200-600 MeV, 0.4-1.2% rms energy spread, 10-80 pC charge, and 0.2 mrad rms divergence are experimentally obtained. Unprecedentedly high 6-dimensional (6-D) brightness B6D,n in units of A/m2/0.1% was estimated at the level of 1015-16, which is very close to the typical brightness of e beams from state-of-the-art linac drivers and several-fold higher than those of previously reported LWFAs. Furthermore, we propose a scheme to minimize the energy spread of an e beam in a cascaded LWFA to the one-thousandth-level by inserting a stage to compress its longitudinal spatial distribution via velocity bunching. In this scheme, three-segment plasma stages are designed for electron injection, e-beam length compression, and e-beam acceleration, respectively. A one-dimensional theory and two-dimensional particle-in-cell simulations have demonstrated this scheme and an e beam with 0.2% rms energy spread and low transverse emittance could be generated without loss of charge. Based on the high-quality e beams generated in the LWFA, we have experimentally realized a new scheme to enhance the

BAKABLE ULTRA-HIGH VACUUM VALVE

DOEpatents

Mark, J.T.; Gantz, I.H.

1962-07-10

S>This patent relates to a valve useful in applications involving successively closing and opening a communication between a chamber evacuated to an ultra-high vacuum condition of the order of 10/sup -10/ millimeters of mercury and another chamber or the ambient. The valve is capable of withstanding extended baking at 450 deg C and repeated opening and closing without repiacement of the valve seat (approximately 200 cycle limit). The seal is formed by mutual interdiffusion weld, coerced by a pneumatic actuator. (AEC)

Spacewalking_in_Ultra_High_Definition

NASA Image and Video Library

2017-07-21

Ever wonder what the spacewalker sees while you’re looking at him or her? Here’s your answer, courtesy of NASA astronaut Jack Fischer. This Ultra High Definition clip shows Fischer outside the International Space Station during a spacewalk on Expedition 51 in May 2017, and the view from a small camera attached to his spacesuit at the same time. Music by Joakim Karud. _______________________________________ FOLLOW THE SPACE STATION! Twitter: https://twitter.com/Space_Station Facebook: https://www.facebook.com/ISS Instagram: https://instagram.com/iss/

Modeling Laser Wakefield Accelerators in a Lorentz Boosted Frame

NASA Astrophysics Data System (ADS)

Vay, J.-L.; Geddes, C. G. R.; Benedetti, C.; Bruhwiler, D. L.; Cormier-Michel, E.; Cowan, B. M.; Cary, J. R.; Grote, D. P.

2010-11-01

Modeling of laser-plasma wakefield accelerators in an optimal frame of reference has been shown to produce up to three orders of magnitude speed-up in calculations from first principles of stages in the 100 MeV-10 GeV energy range. Maximum obtainable speedups calculated using linear theory predict that higher speedups are attainable, in the range of 4-6 orders of magnitude for stages in the energy range of 10 GeV-1 TeV respectively. Practical limitations have been reported and discussed which have prevented reaching these speedups so far, including a violent high frequency numerical instability. The limitations are briefly reviewed and discussed in this paper, as well as their mitigation. It is also reported that the high frequency numerical instability can be controlled effectively using novel numerical techniques that have been implemented in the Particle-In-Cell code Warp, and that 5 and 6 orders of magnitude speedups were demonstrated on 100 GeV and 1 TeV stages respectively, verifying the scaling of plasma accelerators to very high energies, and providing highly efficient tools for the detailed designs of experiments on new lasers such as BELLA.

Simultaneous determination of four alkaloids in Lindera aggregata by ultra-high-pressure liquid chromatography-tandem mass spectrometry.

PubMed

Han, Zheng; Zheng, Yunliang; Chen, Na; Luan, Lianjun; Zhou, Changxin; Gan, Lishe; Wu, Yongjiang

2008-11-28

A new separation and quantification method using liquid chromatography under ultra-high-pressure in combination with tandem mass spectrometry (MS/MS) was developed for simultaneous determination of four alkaloids in Lindera aggregata. The analysis was performed on an Acquity UPLC BEH C(18) column (50mmx2.1mm, 1.7microm particle size; Waters, Milford, MA, USA) utilizing a gradient elution profile and a mobile phase consisting of (A) water containing 10mM ammonium acetate adjusted to pH 3 with acetic acid and (B) acetonitrile. An electrospray ionization (ESI)-tandem interface in the positive mode was employed prior to mass spectrometric detection. The calibration curve was linear over the range of 17.1-856ng for boldine, 42.4-2652ng for norboldine, 6.1-304ng for reticuline and 0.5-50ng for linderegatine, respectively. The average recoveries ranged from 99.2 to 101.4% with RSDs< or =2.7%. Then, four L. aggregata samples from different batches were analyzed using the established method. The results indicated that ultra-high-pressure liquid chromatography-tandem mass spectrometry provided improved chromatographic parameters resulting in significantly increased sample throughput including lower solvent consumption and lower limits of quantitation (LOQs) for most of target analytes compared to previous method employing conventional high-performance liquid chromatography (HPLC) separation. So, the established method was validated, sensitive and reliable for the determination of four alkaloids in L. aggregata.

Fabrication of high wettability gradient on copper substrate

NASA Astrophysics Data System (ADS)

Huang, Ding-Jun; Leu, Tzong-Shyng

2013-09-01

Copper is one of the most widely used materials in condensation heat transfer. Recently there has been great interest in improving the condensation heat transfer efficiency through copper surface modification. In this study, we describe the fabrication processes of how copper surfaces were modified to be superhydrophilic (CA ≤ 10°) and superhydrophobic (CA > 150°) by means of H2O2 immersion and fluorination with Teflon. The wettability gradient of copper surfaces with contact angles (CA) changing from superhydrophilic to superhydrophobic are also demonstrated. Unlike previous studies on gradient surfaces in which the wettability gradient is controlled either non-precisely or entirely uncontrolled, in this study, the contact angles along wettability gradient copper surfaces vary with a precisely designed gradient. It is demonstrated that a high wettability gradient copper surface can be successfully fabricated using photolithography to define the area ratios between superhydrophilic and superhydrophobic patterns within a short distance. The fabricated wettability gradient of copper surfaces is expected to be able to enhance the condensation heat transfer efficiency.

Ultra-high vacuum compatible induction-heated rod casting furnace

NASA Astrophysics Data System (ADS)

Bauer, A.; Neubauer, A.; Münzer, W.; Regnat, A.; Benka, G.; Meven, M.; Pedersen, B.; Pfleiderer, C.

2016-06-01

We report the design of a radio-frequency induction-heated rod casting furnace that permits the preparation of polycrystalline ingots of intermetallic compounds under ultra-high vacuum compatible conditions. The central part of the system is a bespoke water-cooled Hukin crucible supporting a casting mold. Depending on the choice of the mold, typical rods have a diameter between 6 mm and 10 mm and a length up to 90 mm, suitable for single-crystal growth by means of float-zoning. The setup is all-metal sealed and may be baked out. We find that the resulting ultra-high vacuum represents an important precondition for processing compounds with high vapor pressures under a high-purity argon atmosphere up to 3 bars. Using the rod casting furnace, we succeeded to prepare large high-quality single crystals of two half-Heusler compounds, namely, the itinerant antiferromagnet CuMnSb and the half-metallic ferromagnet NiMnSb.

Ultra-high vacuum compatible induction-heated rod casting furnace.

PubMed

Bauer, A; Neubauer, A; Münzer, W; Regnat, A; Benka, G; Meven, M; Pedersen, B; Pfleiderer, C

2016-06-01

We report the design of a radio-frequency induction-heated rod casting furnace that permits the preparation of polycrystalline ingots of intermetallic compounds under ultra-high vacuum compatible conditions. The central part of the system is a bespoke water-cooled Hukin crucible supporting a casting mold. Depending on the choice of the mold, typical rods have a diameter between 6 mm and 10 mm and a length up to 90 mm, suitable for single-crystal growth by means of float-zoning. The setup is all-metal sealed and may be baked out. We find that the resulting ultra-high vacuum represents an important precondition for processing compounds with high vapor pressures under a high-purity argon atmosphere up to 3 bars. Using the rod casting furnace, we succeeded to prepare large high-quality single crystals of two half-Heusler compounds, namely, the itinerant antiferromagnet CuMnSb and the half-metallic ferromagnet NiMnSb.

Multistage Coupling of Laser-Wakefield Accelerators with Curved Plasma Channels.

PubMed

Luo, J; Chen, M; Wu, W Y; Weng, S M; Sheng, Z M; Schroeder, C B; Jaroszynski, D A; Esarey, E; Leemans, W P; Mori, W B; Zhang, J

2018-04-13

Multistage coupling of laser-wakefield accelerators is essential to overcome laser energy depletion for high-energy applications such as TeV-level electron-positron colliders. Current staging schemes feed subsequent laser pulses into stages using plasma mirrors while controlling electron beam focusing with plasma lenses. Here a more compact and efficient scheme is proposed to realize the simultaneous coupling of the electron beam and the laser pulse into a second stage. A partly curved channel, integrating a straight acceleration stage with a curved transition segment, is used to guide a fresh laser pulse into a subsequent straight channel, while the electrons continue straight. This scheme benefits from a shorter coupling distance and continuous guiding of the electrons in plasma while suppressing transverse beam dispersion. Particle-in-cell simulations demonstrate that the electron beam from a previous stage can be efficiently injected into a subsequent stage for further acceleration while maintaining high capture efficiency, stability, and beam quality.

Multistage Coupling of Laser-Wakefield Accelerators with Curved Plasma Channels

NASA Astrophysics Data System (ADS)

Luo, J.; Chen, M.; Wu, W. Y.; Weng, S. M.; Sheng, Z. M.; Schroeder, C. B.; Jaroszynski, D. A.; Esarey, E.; Leemans, W. P.; Mori, W. B.; Zhang, J.

2018-04-01

Multistage coupling of laser-wakefield accelerators is essential to overcome laser energy depletion for high-energy applications such as TeV-level electron-positron colliders. Current staging schemes feed subsequent laser pulses into stages using plasma mirrors while controlling electron beam focusing with plasma lenses. Here a more compact and efficient scheme is proposed to realize the simultaneous coupling of the electron beam and the laser pulse into a second stage. A partly curved channel, integrating a straight acceleration stage with a curved transition segment, is used to guide a fresh laser pulse into a subsequent straight channel, while the electrons continue straight. This scheme benefits from a shorter coupling distance and continuous guiding of the electrons in plasma while suppressing transverse beam dispersion. Particle-in-cell simulations demonstrate that the electron beam from a previous stage can be efficiently injected into a subsequent stage for further acceleration while maintaining high capture efficiency, stability, and beam quality.

Multistage Coupling of Laser-Wakefield Accelerators with Curved Plasma Channel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luo, J.; Chen, M.; Wu, W. Y.

Multistage coupling of laser-wakefield accelerators is essential to overcome laser energy depletion for high-energy applications such as TeV level electron-positron colliders. Current staging schemes feed subsequent laser pulses into stages using plasma mirrors, while controlling electron beam focusing with plasma lenses. Here a more compact and efficient scheme is proposed to realize simultaneous coupling of the electron beam and the laser pulse into a second stage. Furthermore, a curved channel with transition segment is used to guide a fresh laser pulse into a subsequent straight channel, while allowing the electrons to propagate in a straight channel. This scheme then benefitsmore » from a shorter coupling distance and continuous guiding of the electrons in plasma, while suppressing transverse beam dispersion. Within moderate laser parameters, particle-in-cell simulations demonstrate that the electron beam from a previous stage can be efficiently injected into a subsequent stage for further acceleration, while maintaining high capture efficiency, stability, and beam quality.« less

Multistage Coupling of Laser-Wakefield Accelerators with Curved Plasma Channel

DOE PAGES

Luo, J.; Chen, M.; Wu, W. Y.; ...

2018-04-10

Multistage coupling of laser-wakefield accelerators is essential to overcome laser energy depletion for high-energy applications such as TeV level electron-positron colliders. Current staging schemes feed subsequent laser pulses into stages using plasma mirrors, while controlling electron beam focusing with plasma lenses. Here a more compact and efficient scheme is proposed to realize simultaneous coupling of the electron beam and the laser pulse into a second stage. Furthermore, a curved channel with transition segment is used to guide a fresh laser pulse into a subsequent straight channel, while allowing the electrons to propagate in a straight channel. This scheme then benefitsmore » from a shorter coupling distance and continuous guiding of the electrons in plasma, while suppressing transverse beam dispersion. Within moderate laser parameters, particle-in-cell simulations demonstrate that the electron beam from a previous stage can be efficiently injected into a subsequent stage for further acceleration, while maintaining high capture efficiency, stability, and beam quality.« less

Why do high-redshift galaxies show diverse gas-phase metallicity gradients?

NASA Astrophysics Data System (ADS)

Ma, Xiangcheng; Hopkins, Philip F.; Feldmann, Robert; Torrey, Paul; Faucher-Giguère, Claude-André; Kereš, Dušan

2017-04-01

Recent spatially resolved observations of galaxies at z ˜ 0.6-3 reveal that high-redshift galaxies show complex kinematics and a broad distribution of gas-phase metallicity gradients. To understand these results, we use a suite of high-resolution cosmological zoom-in simulations from the Feedback in Realistic Environments project, which include physically motivated models of the multiphase interstellar medium, star formation and stellar feedback. Our simulations reproduce the observed diversity of kinematic properties and metallicity gradients, broadly consistent with observations at z ˜ 0-3. Strong negative metallicity gradients only appear in galaxies with a rotating disc, but not all rotationally supported galaxies have significant gradients. Strongly perturbed galaxies with little rotation always have flat gradients. The kinematic properties and metallicity gradient of a high-redshift galaxy can vary significantly on short time-scales, associated with starburst episodes. Feedback from a starburst can destroy the gas disc, drive strong outflows and flatten a pre-existing negative metallicity gradient. The time variability of a single galaxy is statistically similar to the entire simulated sample, indicating that the observed metallicity gradients in high-redshift galaxies reflect the instantaneous state of the galaxy rather than the accretion and growth history on cosmological time-scales. We find weak dependence of metallicity gradient on stellar mass and specific star formation rate (sSFR). Low-mass galaxies and galaxies with high sSFR tend to have flat gradients, likely due to the fact that feedback is more efficient in these galaxies. We argue that it is important to resolve feedback on small scales in order to produce the diverse metallicity gradients observed.

Extremely short relativistic-electron-bunch generation in the laser wakefield via novel bunch injection scheme

NASA Astrophysics Data System (ADS)

Khachatryan, A. G.; van Goor, F. A.; Boller, K.-J.; Reitsma, A. J.; Jaroszynski, D. A.

2004-12-01

Recently a new electron-bunch injection scheme for the laser wakefield accelerator has been proposed [

Efficient injection of radiation-pressure-accelerated sub-relativistic protons into laser wakefield acceleration based on 10 PW lasers

NASA Astrophysics Data System (ADS)

Liu, M.; Weng, S. M.; Wang, H. C.; Chen, M.; Zhao, Q.; Sheng, Z. M.; He, M. Q.; Li, Y. T.; Zhang, J.

2018-06-01

We propose a hybrid laser-driven ion acceleration scheme using a combination target of a solid foil and a density-tailored background plasma. In the first stage, a sub-relativistic proton beam can be generated by radiation pressure acceleration in intense laser interaction with the solid foil. In the second stage, this sub-relativistic proton beam is further accelerated by the laser wakefield driven by the same laser pulse in a near-critical-density background plasma with decreasing density profile. The propagating velocity of the laser front and the phase velocity of the excited wakefield wave are effectively lowered at the beginning of the second stage. By decreasing the background plasma density gradually from near critical density along the laser propagation direction, the wake travels faster and faster, while it accelerates the protons. Consequently, the dephasing between the protons and the wake is postponed and an efficient wakefield proton acceleration is achieved. This hybrid laser-driven proton acceleration scheme can be realized by using ultrashort laser pulses at the peak power of 10 PW for the generation of multi-GeV proton beams.

Laser pulse propagation in inhomogeneous magnetoplasma channels and wakefield acceleration

NASA Astrophysics Data System (ADS)

Sharma, B. S.; Jain, Archana; Jaiman, N. K.; Gupta, D. N.; Jang, D. G.; Suk, H.; Kulagin, V. V.

2014-02-01

Wakefield excitation in a preformed inhomogeneous parabolic plasma channel by an intense relativistic (≃1019 W/cm2) circularly polarized Gaussian laser pulse is investigated analytically and numerically in the presence of an external longitudinal magnetic field. A three dimensional envelope equation for the evolution of the laser pulse is derived, which includes the effect of the nonparaxial and applied external magnetic field. A relation for the channel radius with the laser spot size is derived and examines numerically to see the external magnetic field effect. It is observed that the channel radius depends on the applied external magnetic field. An analytical expression for the wakefield is derived and validated with the help of a two dimensional particle in cell (2D PIC) simulation code. It is shown that the electromagnetic nature of the wakes in an inhomogeneous plasma channel makes their excitation nonlocal, which results in change of fields with time and external magnetic field due to phase mixing of the plasma oscillations with spatially varying frequencies. The magnetic field effect on perturbation of the plasma density and decreasing length is also analyzed numerically. In addition, it has been shown that the electron energy gain in the inhomogeneous parabolic magnetoplasma channel can be increased significantly compared with the homogeneous plasma channel.

Analysis of radial and longitudinal field of plasma wakefield generated by a Laguerre-Gauss laser pulse

DOE Office of Scientific and Technical Information (OSTI.GOV)

Firouzjaei, Ali Shekari; Shokri, Babak

In the present paper, we study the wakes known as the donut wake which is generated by Laguerre-Gauss (LG) laser pulses. Effects of the special spatial profile of a LG pulse on the radial and longitudinal wakefields are presented via an analytical model in a weakly non-linear regime in two dimensions. Different aspects of the donut-shaped wakefields have been analyzed and compared with Gaussian-driven wakes. There is also some discussion about the accelerating-focusing phase of the donut wake. Variations of longitudinal and radial wakes with laser amplitude, pulse length, and pulse spot size have been presented and discussed. Finally, wemore » present the optimum pulse duration for such wakes.« less

Experimental Evidence of Radiation Reaction in the Collision of a High-Intensity Laser Pulse with a Laser-Wakefield Accelerated Electron Beam

NASA Astrophysics Data System (ADS)

Cole, J. M.; Behm, K. T.; Gerstmayr, E.; Blackburn, T. G.; Wood, J. C.; Baird, C. D.; Duff, M. J.; Harvey, C.; Ilderton, A.; Joglekar, A. S.; Krushelnick, K.; Kuschel, S.; Marklund, M.; McKenna, P.; Murphy, C. D.; Poder, K.; Ridgers, C. P.; Samarin, G. M.; Sarri, G.; Symes, D. R.; Thomas, A. G. R.; Warwick, J.; Zepf, M.; Najmudin, Z.; Mangles, S. P. D.

2018-02-01

The dynamics of energetic particles in strong electromagnetic fields can be heavily influenced by the energy loss arising from the emission of radiation during acceleration, known as radiation reaction. When interacting with a high-energy electron beam, today's lasers are sufficiently intense to explore the transition between the classical and quantum radiation reaction regimes. We present evidence of radiation reaction in the collision of an ultrarelativistic electron beam generated by laser-wakefield acceleration (ɛ >500 MeV ) with an intense laser pulse (a0>10 ). We measure an energy loss in the postcollision electron spectrum that is correlated with the detected signal of hard photons (γ rays), consistent with a quantum description of radiation reaction. The generated γ rays have the highest energies yet reported from an all-optical inverse Compton scattering scheme, with critical energy ɛcrit>30 MeV .

Search for Ultra-High Energy Photons with the Pierre Auger Observatory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Homola, Piotr

One of key scientific objectives of the Pierre Auger Observatory is the search for ultra-high energy photons. Such photons could originate either in the interactions of energetic cosmic-ray nuclei with the cosmic microwave background (so-called cosmogenic photons) or in the exotic scenarios, e.g. those assuming a production and decay of some hypothetical super-massive particles. The latter category of models would imply relatively large fluxes of photons with ultra-high energies at Earth, while the former, involving interactions of cosmic-ray nuclei with the microwave background - just the contrary: very small fractions. The investigations on the data collected so far in themore » Pierre Auger Observatory led to placing very stringent limits to ultra-high energy photon fluxes: below the predictions of the most of the exotic models and nearing the predicted fluxes of the cosmogenic photons. In this paper the status of these investigations and perspectives for further studies are summarized.« less

Spectrum bandwidth narrowing of Thomson scattering X-rays with energy chirped electron beams from laser wakefield acceleration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Tong; Chen, Min, E-mail: minchen@sjtu.edu.cn; Li, Fei-Yu

2014-01-06

We study incoherent Thomson scattering between an ultrashort laser pulse and an electron beam accelerated from a laser wakefield. The energy chirp effects of the accelerated electron beam on the final radiation spectrum bandwidth are investigated. It is found that the scattered X-ray radiation has the minimum spectrum width and highest intensity as electrons are accelerated up to around the dephasing point. Furthermore, it is proposed that the electron acceleration process inside the wakefield can be studied by use of 90° Thomson scattering. The dephasing position and beam energy chirp can be deduced from the intensity and bandwidth of themore » scattered radiation.« less

Variable high gradient permanent magnet quadrupole (QUAPEVA)

NASA Astrophysics Data System (ADS)

Marteau, F.; Ghaith, A.; N'Gotta, P.; Benabderrahmane, C.; Valléau, M.; Kitegi, C.; Loulergue, A.; Vétéran, J.; Sebdaoui, M.; André, T.; Le Bec, G.; Chavanne, J.; Vallerand, C.; Oumbarek, D.; Cosson, O.; Forest, F.; Jivkov, P.; Lancelot, J. L.; Couprie, M. E.

2017-12-01

Different applications such as laser plasma acceleration, colliders, and diffraction limited light sources require high gradient quadrupoles, with strength that can reach up to 200 T/m for a typical 10 mm bore diameter. We present here a permanent magnet based quadrupole (so-called QUAPEVA) composed of a Halbach ring and surrounded by four permanent magnet cylinders. Its design including magnetic simulation modeling enabling us to reach 201 T/m with a gradient variability of 45% and mechanical issues are reported. Magnetic measurements of seven systems of different lengths are presented and confirmed the theoretical expectations. The variation of the magnetic center while changing the gradient strength is ±10 μm. A triplet of QUAPEVA magnets is used to efficiently focus a beam with large energy spread and high divergence that is generated by a Laser Plasma Acceleration source for a free electron laser demonstration and has enabled us to perform beam based alignment and control the dispersion of the beam.

Method transfer from high-pressure liquid chromatography to ultra-high-pressure liquid chromatography. II. Temperature and pressure effects.

PubMed

Åsberg, Dennis; Samuelsson, Jörgen; Leśko, Marek; Cavazzini, Alberto; Kaczmarski, Krzysztof; Fornstedt, Torgny

2015-07-03

The importance of the generated temperature and pressure gradients in ultra-high-pressure liquid chromatography (UHPLC) are investigated and compared to high-pressure liquid chromatography (HPLC). The drug Omeprazole, together with three other model compounds (with different chemical characteristics, namely uncharged, positively and negatively charged) were used. Calculations of the complete temperature profile in the column at UHPLC conditions showed, in our experiments, a temperature difference between the inlet and outlet of 16 °C and a difference of 2 °C between the column center and the wall. Through van't Hoff plots, this information was used to single out the decrease in retention factor (k) solely due to the temperature gradient. The uncharged solute was least affected by temperature with a decrease in k of about 5% while for charged solutes the effect was more pronounced, with k decreases up to 14%. A pressure increase of 500 bar gave roughly 5% increase in k for the uncharged solute, while omeprazole and the other two charged solutes gave about 25, 20 and 15% increases in k, respectively. The stochastic model of chromatography was applied to estimate the dependence of the average number of adsorption/desorption events (n) and the average time spent by a molecule in the stationary phase (τs) on temperature and pressure on peak shape for the tailing, basic solute. Increasing the temperature yielded an increase in n and decrease in τs which resulted in less skew at high temperatures. With increasing pressure, the stochastic modeling gave interesting results for the basic solute showing that the skew of the peak increased with pressure. The conclusion is that pressure effects are more pronounced for both retention and peak shape than the temperature effects for the polar or charged compounds in our study. Copyright © 2015 Elsevier B.V. All rights reserved.

Laser beam welding of new ultra-high strength and supra-ductile steels

NASA Astrophysics Data System (ADS)

Dahmen, Martin

2015-03-01

Ultra-high strength and supra-ductile are entering fields of new applications. Those materials are excellent candidates for modern light-weight construction and functional integration. As ultra-high strength steels the stainless martensitic grade 1.4034 and the bainitic steel UNS 53835 are investigated. For the supra-ductile steels stand two high austenitic steels with 18 and 28 % manganese. As there are no processing windows an approach from the metallurgical base on is required. Adjusting the weld microstructure the Q+P and the QT steels require weld heat treatment. The HSD steel is weldable without. Due to their applications the ultra-high strength steels are welded in as-rolled and strengthened condition. Also the reaction of the weld on hot stamping is reflected for the martensitic grades. The supra-ductile steels are welded as solution annealed and work hardened by 50%. The results show the general suitability for laser beam welding.

Energy spread minimization in a cascaded laser wakefield accelerator via velocity bunching

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Zhijun; Li, Wentao; Wang, Wentao

2016-05-15

We propose a scheme to minimize the energy spread of an electron beam (e-beam) in a cascaded laser wakefield accelerator to the one-thousandth-level by inserting a stage to compress its longitudinal spatial distribution. In this scheme, three-segment plasma stages are designed for electron injection, e-beam length compression, and e-beam acceleration, respectively. The trapped e-beam in the injection stage is transferred to the zero-phase region at the center of one wakefield period in the compression stage where the length of the e-beam can be greatly shortened owing to the velocity bunching. After being seeded into the third stage for acceleration, themore » e-beam can be accelerated to a much higher energy before its energy chirp is compensated owing to the shortened e-beam length. A one-dimensional theory and two-dimensional particle-in-cell simulations have demonstrated this scheme and an e-beam with 0.2% rms energy spread and low transverse emittance could be generated without loss of charge.« less

Manganese oxide micro-supercapacitors with ultra-high areal capacitance

NASA Astrophysics Data System (ADS)

Wang, Xu; Myers, Benjamin D.; Yan, Jian; Shekhawat, Gajendra; Dravid, Vinayak; Lee, Pooi See

2013-05-01

A symmetric micro-supercapacitor is constructed by electrochemically depositing manganese oxide onto micro-patterned current collectors. High surface-to-volume ratio of manganese oxide and short diffusion distance between electrodes give an ultra-high areal capacitance of 56.3 mF cm-2 at a current density of 27.2 μA cm-2.A symmetric micro-supercapacitor is constructed by electrochemically depositing manganese oxide onto micro-patterned current collectors. High surface-to-volume ratio of manganese oxide and short diffusion distance between electrodes give an ultra-high areal capacitance of 56.3 mF cm-2 at a current density of 27.2 μA cm-2. Electronic supplementary information (ESI) available: Experimental procedures; optical images of micro-supercapacitors; areal capacitances of samples M-0.3C, M-0.6C and M-0.9C; illustration of interdigital finger electrodes; Nyquist plot of Co(OH)2 deposited on micro-electrodes. See DOI: 10.1039/c3nr00210a

Sweating the small stuff: simulating dwarf galaxies, ultra-faint dwarf galaxies, and their own tiny satellites

NASA Astrophysics Data System (ADS)

Wheeler, Coral Rose

2016-06-01

The high dark matter content and the shallow potential wells of low mass galaxies (10^3 Msun < Mstar < 10^9.5 Msun) make them excellent testbeds for differing theories of galaxy formation. Additionally, the recent up-tick in the number and detail of Local Group dwarf galaxy observations provides a rich dataset for comparison to simulations that attempt to answer important questions in near field cosmology: why are there so few observed dwarfs compared to the number predicted by simulations? What shuts down star formation in ultra-faint galaxies? Why do dwarfs have inverted age gradients and what does it take to convert a dwarf irregular (dIrrs) into a dwarf spheroidal (dSph) galaxy?We to attempt to answer these questions by running ultra-high resolution cosmological FIRE simulations of isolated dwarf galaxies. We predict that many ultra-faint dwarfs should exist as satellites of more massive isolated Local Group dwarfs. The ultra-faints (Mstar < 10^4 Msun) formed in these simulations have uniformly ancient stellar populations (> 10 Gyr), having had their star formation shut down by reionization. Additionally, we show that the kinematics and ellipticities of isolated simulated dwarf centrals are consistent with observed dSphs satellites without the need for harassment from a massive host. We further show that most (but not all) observed *isolated* dIrrs in the Local Volume also have dispersion-supported stellar populations, contradicting the previous view that these objects are rotating. Finally, we investigate the stellar age gradients in dwarfs — showing that early mergers and strong feedback can create an inverted gradient, with the older stars occupying larger galactocentric radii.These results offer an interesting direction in testing models that attempt to solve dark matter problems via explosive feedback episodes. Can the same models that create large cores in simulated dwarfs preserve the mild stellar rotation that is seen in a minority of isolated d

Comparison of the response of four aerosol detectors used with ultra high pressure liquid chromatography.

PubMed

Hutchinson, Joseph P; Li, Jianfeng; Farrell, William; Groeber, Elizabeth; Szucs, Roman; Dicinoski, Greg; Haddad, Paul R

2011-03-25

The responses of four different types of aerosol detectors have been evaluated and compared to establish their potential use as a universal detector in conjunction with ultra high pressure liquid chromatography (UHPLC). Two charged-aerosol detectors, namely Corona CAD and Corona Ultra, and also two different types of light-scattering detectors (an evaporative light scattering detector, and a nano-quantity analyte detector [NQAD]) were evaluated. The responses of these detectors were systematically investigated under changing experimental and instrumental parameters, such as the mobile phase flow-rate, analyte concentration, mobile phase composition, nebulizer temperature, evaporator temperature, evaporator gas flow-rate and instrumental signal filtering after detection. It was found that these parameters exerted non-linear effects on the responses of the aerosol detectors and must therefore be considered when designing analytical separation conditions, particularly when gradient elution is performed. Identical reversed-phase gradient separations were compared on all four aerosol detectors and further compared with UV detection at 200 nm. The aerosol detectors were able to detect all 11 analytes in a test set comprising species having a variety of physicochemical properties, whilst UV detection was applicable only to those analytes containing chromophores. The reproducibility of the detector response for 11 analytes over 10 consecutive separations was found to be approximately 5% for the charged-aerosol detectors and approximately 11% for the light-scattering detectors. The tested analytes included semi-volatile species which exhibited a more variable response on the aerosol detectors. Peak efficiencies were generally better on the aerosol detectors in comparison to UV detection and particularly so for the light-scattering detectors which exhibited efficiencies of around 110,000 plates per metre. Limits of detection were calculated using different mobile phase

New-type steel plate with ultra high crack-arrestability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ishikawa, T.; Nomiyama, Y.; Hagiwara, Y.

1995-12-31

A new-type steel plate has been developed by controlling the microstructure of the surface layers. The surface layer consists of ultra fine grain ferrite microstructure, which provides excellent fracture toughness even at cryogenic temperature. When an unstable brittle crack propagates in the developed steel plate, shear-lips can be easily formed due to the surface layers with ultra fine grain microstructure. Since unstable running crack behavior is strongly affected by side-ligaments (shear-lips), which are associated with extensive plastic deformation, enhanced formation of the shear-lips can improve crack arrestability. This paper describes the developed steel plates of HT500MPa tensile strength class formore » shipbuilding use. Fracture mechanics investigations using large-scale fracture testings (including ultrawide duplex ESSO tests) clarified that the developed steel plates have ultra high crack-arrestability. It was also confirmed that the plates possess sufficient properties, including weldability and workability, for ship building use.« less

Application of ultra-high performance concrete to bridge girders.

DOT National Transportation Integrated Search

2009-02-01

"Ultra-High Performance Concrete (UHPC) is a new class of concrete that has superior performance characteristics : compared to conventional concrete. The enhanced strength and durability properties of UHPC are mainly due to optimized : particle grada...

Plasma Accelerators Race to 10 GeV and Beyond

NASA Astrophysics Data System (ADS)

Katsouleas, Tom

2005-10-01

This paper reviews the concepts, recent progress and current challenges for realizing the tremendous electric fields in relativistic plasma waves for applications ranging from tabletop particle accelerators to high-energy physics. Experiments in the 90's on laser-driven plasma wakefield accelerators at several laboratories around the world demonstrated the potential for plasma wakefields to accelerate intense bunches of self-trapped particles at rates as high as 100 GeV/m in mm-scale gas jets. These early experiments offered impressive gradients but large energy spread (100%) and short interaction lengths. Major breakthroughs have recently occurred on both fronts. Three groups (LBL-US, LOA-France and RAL-UK) have now entered a new regime of laser wakefield acceleration resulting in 100 MeV mono-energetic beams with up to nanoCoulombs of charge and very small angular spread. Simulations suggest that current lasers are just entering this new regime, and the scaling to higher energies appears attractive. In parallel with the progress in laser-driven wakefields, particle-beam driven wakefield accelerators are making large strides. A series of experiments using the 30 GeV beam of the Stanford Linear Accelerator Center (SLAC) has demonstrated high-gradient acceleration of electrons and positrons in meter-scale plasmas. The UCLA/USC/SLAC collaboration has accelerated electrons beyond 1 GeV and is aiming at 10 GeV in 30 cm as the next step toward a ``plasma afterburner,'' a concept for doubling the energy of a high-energy collider in a few tens of meters of plasma. In addition to wakefield acceleration, these and other experiments have demonstrated the rich physics bounty to be reaped from relativistic beam-plasma interactions. This includes plasma lenses capable of focusing particle beams to the highest density ever produced, collective radiation mechanisms capable of generating high-brightness x-ray beams, collective refraction of particles at a plasma interface, and

Study on creep of fiber reinforced ultra-high strength concrete based on strength

NASA Astrophysics Data System (ADS)

Peng, Wenjun; Wang, Tao

2018-04-01

To complement the creep performance of ultra-high strength concrete, the long creep process of fiber reinforced concrete was studied in this paper. The long-term creep process and regularity of ultra-high strength concrete with 0.5% PVA fiber under the same axial compression were analyzed by using concrete strength (C80/C100/C120) as a variable. The results show that the creep coefficient of ultra-high strength concrete decreases with the increase of concrete strength. Compared with ACI209R (92), GL2000 models, it is found that the predicted value of ACI209R (92) are close to the experimental value, and the creep prediction model suitable for this experiment is proposed based on ACI209R (92).

Field Evaluation of Ultra-High Pressure Water Systems for Runway Rubber Removal

DTIC Science & Technology

2014-04-01

ER D C/ G SL T R- 14 -1 1 Field Evaluation of Ultra-High Pressure Water Systems for Runway Rubber Removal G eo te ch ni ca l a nd S tr...Field Evaluation of Ultra-High Pressure Water Systems for Runway Rubber Removal Aaron B. Pullen Applied Research Associates, Inc. 421 Oak Avenue...collaboration with Applied Research Associates, Inc. (ARA). Several types of commercial UHPW water blasting systems were tested on an ungrooved portland cement

Ultra high vacuum test setup for electron gun

NASA Astrophysics Data System (ADS)

Pandiyar, M. L.; Prasad, M.; Jain, S. K.; Kumar, R.; Hannurkar, P. R.

2008-05-01

Ultra High Vacuum (UHV) test setup for electron gun testing has been developed. The development of next generation light sources and accelerators require development of klystron as a radio frequency power source, and in turn electron gun. This UHV electron gun test setup can be used to test the electron guns ranging from high average current, quasi-continuous wave to high peak current, single pulse etc. An electron gun has been designed, fabricated, assembled and tested for insulation up to 80 kV under the programme to develop high power klystron for future accelerators. Further testing includes the electron emission parameters characterization of the cathode, as it determines the development of a reliable and efficient electron gun with high electron emission current and high life time as well. This needs a clean ultra high vacuum to study these parameters particularly at high emission current. The cathode emission current, work function and vapour pressure of cathode surface material at high temperature studies will further help in design and development of high power electron gun The UHV electron gun test setup consists of Turbo Molecular Pump (TMP), Sputter Ion Pump (SIP), pressure gauge, high voltage and cathode power supplies, current measurement device, solenoid magnet and its power supply, residual gas analyser etc. The ultimate vacuum less than 2×10-9 mbar was achieved. This paper describes the UHV test setup for electron gun testing.

Bond behavior of reinforcing steel in ultra-high performance concrete.

DOT National Transportation Integrated Search

2014-10-01

Ultra-High Performance Concrete (UHPC) is a relatively new class of advanced cementitious composite : materials, which exhibits high compressive [above 21.7 ksi (150 MPa)] and tensile [above 0.72 ksi (5 MPa)] : strengths. The discrete steel fiber rei...

Stability condition for the drive bunch in a collinear wakefield accelerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baturin, S. S.; Zholents, A.

The beam breakup instability of the drive bunch in the structure-based collinear wakefield accelerator is considered and a stabilizing method is proposed. The method includes using the specially designed beam focusing channel, applying the energy chirp along the electron bunch, and keeping energy chirp constant during the drive bunch deceleration. A stability condition is derived that defines the limit on the accelerating field for the witness bunch.

Observation of High Transformer Ratio of Shaped Bunch Generated by an Emittance-Exchange Beam Line.

PubMed

Gao, Q; Ha, G; Jing, C; Antipov, S P; Power, J G; Conde, M; Gai, W; Chen, H; Shi, J; Wisniewski, E E; Doran, D S; Liu, W; Whiteford, C E; Zholents, A; Piot, P; Baturin, S S

2018-03-16

Collinear wakefield acceleration has been long established as a method capable of generating ultrahigh acceleration gradients. Because of the success on this front, recently, more efforts have shifted towards developing methods to raise the transformer ratio (TR). This figure of merit is defined as the ratio of the peak acceleration field behind the drive bunch to the peak deceleration field inside the drive bunch. TR is always less than 2 for temporally symmetric drive bunch distributions and therefore recent efforts have focused on generating asymmetric distributions to overcome this limitation. In this Letter, we report on using the emittance-exchange method to generate a shaped drive bunch to experimentally demonstrate a TR≈5 in a dielectric wakefield accelerator.

Optimization of the combined proton acceleration regime with a target composition scheme

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yao, W. P.; Graduate School, China Academy of Engineering Physics, Beijing 100088; Li, B. W., E-mail: li-baiwen@iapcm.ac.cn

A target composition scheme to optimize the combined proton acceleration regime is presented and verified by two-dimensional particle-in-cell simulations by using an ultra-intense circularly polarized (CP) laser pulse irradiating an overdense hydrocarbon (CH) target, instead of a pure hydrogen (H) one. The combined acceleration regime is a two-stage proton acceleration scheme combining the radiation pressure dominated acceleration (RPDA) stage and the laser wakefield acceleration (LWFA) stage sequentially together. Protons get pre-accelerated in the first stage when an ultra-intense CP laser pulse irradiating an overdense CH target. The wakefield is driven by the laser pulse after penetrating through the overdense CHmore » target and propagating in the underdense tritium plasma gas. With the pre-accelerate stage, protons can now get trapped in the wakefield and accelerated to much higher energy by LWFA. Finally, protons with higher energies (from about 20 GeV up to about 30 GeV) and lower energy spreads (from about 18% down to about 5% in full-width at half-maximum, or FWHM) are generated, as compared to the use of a pure H target. It is because protons can be more stably pre-accelerated in the first RPDA stage when using CH targets. With the increase of the carbon-to-hydrogen density ratio, the energy spread is lower and the maximum proton energy is higher. It also shows that for the same laser intensity around 10{sup 22} W cm{sup −2}, using the CH target will lead to a higher proton energy, as compared to the use of a pure H target. Additionally, proton energy can be further increased by employing a longitudinally negative gradient of a background plasma density.« less

Influence of measuring algorithm on shape accuracy in the compensating turning of high gradient thin-wall parts

NASA Astrophysics Data System (ADS)

Wang, Tao; Wang, Guilin; Zhu, Dengchao; Li, Shengyi

2015-02-01

In order to meet the requirement of aerodynamics, the infrared domes or windows with conformal and thin-wall structure becomes the development trend of high-speed aircrafts in the future. But these parts usually have low stiffness, the cutting force will change along with the axial position, and it is very difficult to meet the requirement of shape accuracy by single machining. Therefore, on-machine measurement and compensating turning are used to control the shape errors caused by the fluctuation of cutting force and the change of stiffness. In this paper, on the basis of ultra precision diamond lathe, a contact measuring system with five DOFs is developed to achieve on-machine measurement of conformal thin-wall parts with high accuracy. According to high gradient surface, the optimizing algorithm is designed on the distribution of measuring points by using the data screening method. The influence rule of sampling frequency is analyzed on measuring errors, the best sampling frequency is found out based on planning algorithm, the effect of environmental factors and the fitting errors are controlled within lower range, and the measuring accuracy of conformal dome is greatly improved in the process of on-machine measurement. According to MgF2 conformal dome with high gradient, the compensating turning is implemented by using the designed on-machine measuring algorithm. The shape error is less than PV 0.8μm, greatly superior compared with PV 3μm before compensating turning, which verifies the correctness of measuring algorithm.

Plasma-based wakefield accelerators as sources of axion-like particles

NASA Astrophysics Data System (ADS)

Burton, David A.; Noble, Adam

2018-03-01

We estimate the average flux density of minimally-coupled axion-like particles (ALPs) generated by a laser-driven plasma wakefield propagating along a constant strong magnetic field. Our calculations suggest that a terrestrial source based on this approach could generate a pulse of ALPs whose flux density is comparable to that of solar ALPs at Earth. This mechanism is optimal for ALPs with mass in the range of interest of contemporary experiments designed to detect dark matter using microwave cavities.

Vacuum Bloch-Siegert shift in Landau polaritons with ultra-high cooperativity

NASA Astrophysics Data System (ADS)

Li, Xinwei; Bamba, Motoaki; Zhang, Qi; Fallahi, Saeed; Gardner, Geoff C.; Gao, Weilu; Lou, Minhan; Yoshioka, Katsumasa; Manfra, Michael J.; Kono, Junichiro

2018-06-01

A two-level system resonantly interacting with an a.c. magnetic or electric field constitutes the physical basis of diverse phenomena and technologies. However, Schrödinger's equation for this seemingly simple system can be solved exactly only under the rotating-wave approximation, which neglects the counter-rotating field component. When the a.c. field is sufficiently strong, this approximation fails, leading to a resonance-frequency shift known as the Bloch-Siegert shift. Here, we report the vacuum Bloch-Siegert shift, which is induced by the ultra-strong coupling of matter with the counter-rotating component of the vacuum fluctuation field in a cavity. Specifically, an ultra-high-mobility two-dimensional electron gas inside a high-Q terahertz cavity in a quantizing magnetic field revealed ultra-narrow Landau polaritons, which exhibited a vacuum Bloch-Siegert shift up to 40 GHz. This shift, clearly distinguishable from the photon-field self-interaction effect, represents a unique manifestation of a strong-field phenomenon without a strong field.

Ultra high vacuum seal arrangement

DOEpatents

Flaherty, Robert

1981-01-01

Arrangement for demountably sealing two concentric metallic tubes in an ultra high vacuum system which facilitates remote actuation. A tubular seal includes integral spaced lips which circumferentially engage the metallic tubes. The lips plastically deform the metallic tubes by mechanical forces resulting from a martensite to austenite transformation of the tubular seal upon application of a predetermined temperature. The sealing force is released upon application of another temperature which causes a transformation from the stronger austenite to the weaker martensite. Use of a dual acting sealing ring and driving ring circumferentially contacting the sealing ring is particularly applicable to sealing larger diameter concentric metallic members.

Production of Ultra-Light Normal Incidence Mirrors

NASA Technical Reports Server (NTRS)

Jones, Ruth; Muntele, Iulia; Muntele, Claudiu; Zimmerman, Robert L.; Ila, Daryush; Burdine, Robert V. (Technical Monitor)

2002-01-01

Mirrors fabrication for large aperture telescopes is an important aspect in space exploration programs. One of the cost effective techniques to obtain such mirrors is electroplating of Ni-Co alloys from sulfamate solution. The Center for Irradiation of Materials at Alabama A&M University - Research Institute has been involved in a NASA-MSFC project for producing ultra-light Ni-Co alloy mirrors since the summer of year 2000. The goal of this project is to obtain ultra-light, high strength electroformed large aperture normal incidence replicated mirrors, (weighting less than 5 kg/m2), free of stress, with a good figure and reproducible thickness variation. In order to simplify the control of parameters such as temperature gradient, concentration gradient, distribution of the electric field lines and flow control, the proposed geometry involves a cylindrical main tank contained in another cylindrical tank, which plays the role of a weir. Designs were created to accommodate the new horizontal position of the mandrel and the pipes fitting through the outer tank's lid. The inner tank contains the working electrodes and a series of sensors for monitoring temperature, flow, stress and pH. The outer tank holds the electric heaters, the filters and a part of the piping system. Another two tanks complete the setup and serve for rinsing/preheating and equilibrating the electroplating bath. This paper will describe advantages of the new experimental setup and the parameters achieved in the electroplating bath for the proposed geometry.

Design of Ultra-High-Power-Density Machine Optimized for Future Aircraft

NASA Technical Reports Server (NTRS)

Choi, Benjamin B.

2004-01-01

The NASA Glenn Research Center's Structural Mechanics and Dynamics Branch is developing a compact, nonpolluting, bearingless electric machine with electric power supplied by fuel cells for future "more-electric" aircraft with specific power in the projected range of 50 hp/lb, whereas conventional electric machines generate usually 0.2 hp/lb. The use of such electric drives for propulsive fans or propellers depends on the successful development of ultra-high-power-density machines. One possible candidate for such ultra-high-power-density machines, a round-rotor synchronous machine with an engineering current density as high as 20,000 A/sq cm, was selected to investigate how much torque and power can be produced.

Spatially-Resolved Characterization Techniques to Investigate Impact Damage in Ultra-High Performance Concretes

DTIC Science & Technology

2013-04-01

Concretes G eo te ch n ic al a n d S tr u ct u re s La b or at or y Robert D. Moser, Paul G. Allison, and Mei Q. Chandler April 2013 Approved...Impact Damage in Ultra-High Performance Concretes Robert D. Moser, Paul G. Allison, and Mei Q. Chandler Geotechnical and Structures Laboratory US...Portland Cement concrete (OPC) and Ultra-High Performance Concretes (UHPCs) under high-strain impact and penetration loads at lower length scales

Ultra-high density diffraction grating

DOEpatents

Padmore, Howard A.; Voronov, Dmytro L.; Cambie, Rossana; Yashchuk, Valeriy V.; Gullikson, Eric M.

2012-12-11

A diffraction grating structure having ultra-high density of grooves comprises an echellette substrate having periodically repeating recessed features, and a multi-layer stack of materials disposed on the echellette substrate. The surface of the diffraction grating is planarized, such that layers of the multi-layer stack form a plurality of lines disposed on the planarized surface of the structure in a periodical fashion, wherein lines having a first property alternate with lines having a dissimilar property on the surface of the substrate. For example, in one embodiment, lines comprising high-Z and low-Z materials alternate on the planarized surface providing a structure that is suitable as a diffraction grating for EUV and soft X-rays. In some embodiments, line density of between about 10,000 lines/mm to about 100,000 lines/mm is provided.

Intense γ ray generated by refocusing laser pulse on wakefield accelerated electrons

NASA Astrophysics Data System (ADS)

Feng, Jie; Wang, Jinguang; Li, Yifei; Zhu, Changqing; Li, Minghua; He, Yuhang; Li, Dazhang; Wang, Weimin; Chen, Liming

2017-09-01

Ultrafast x/γ ray emission from the combination of laser wake-field acceleration and plasma mirror has been investigated as a promising Thomson scattering source. However, the photon energy and yield of radiation are limited to the intensity of reflected laser pulses. We use the 2D particle in cell simulation to demonstrate that a 75TW driven laser pulse can be refocused on the accelerated electron bunches through a hemispherical plasma mirror with a small f number of 0.25. The energetic electrons with the maximum energy about 350 MeV collide with the reflected laser pulse of a0 = 3.82 at the focal spot, producing high order multi-photon Thomson scattering, and resulting in the scattering spectrum which extends up to 21.2 MeV. Such a high energy γ ray source could be applied to photonuclear reaction and materials science.

Prototyping high-gradient mm-wave accelerating structures

DOE PAGES

Nanni, Emilio A.; Dolgashev, Valery A.; Haase, Andrew; ...

2017-01-01

We present single-cell accelerating structures designed for high-gradient testing at 110 GHz. The purpose of this work is to study the basic physics of ultrahigh vacuum RF breakdown in high-gradient RF accelerators. The accelerating structures are π-mode standing-wave cavities fed with a TM 01 circular waveguide. The structures are fabricated using precision milling out of two metal blocks, and the blocks are joined with diffusion bonding and brazing. The impact of fabrication and joining techniques on the cell geometry and RF performance will be discussed. First prototypes had a measured Q 0 of 2800, approaching the theoretical design value ofmore » 3300. The geometry of these accelerating structures are as close as practical to singlecell standing-wave X-band accelerating structures more than 40 of which were tested at SLAC. This wealth of X-band data will serve as a baseline for these 110 GHz tests. Furthermore, the structures will be powered with short pulses from a MW gyrotron oscillator. RF power of 1 MW may allow an accelerating gradient of 400 MeV/m to be reached.« less

High-energy green supercapacitor driven by ionic liquid electrolytes as an ultra-high stable next-generation energy storage device

NASA Astrophysics Data System (ADS)

Thangavel, Ranjith; Kannan, Aravindaraj G.; Ponraj, Rubha; Thangavel, Vigneysh; Kim, Dong-Won; Lee, Yun-Sung

2018-04-01

Development of supercapacitors with high energy density and long cycle life using sustainable materials for next-generation applications is of paramount importance. The ongoing challenge is to elevate the energy density of supercapacitors on par with batteries, while upholding the power and cyclability. In addition, attaining such superior performance with green and sustainable bio-mass derived compounds is very crucial to address the rising environmental concerns. Herein, we demonstrate the use of watermelon rind, a bio-waste from watermelons, towards high energy, and ultra-stable high temperature green supercapacitors with a high-voltage ionic liquid electrolyte. Supercapacitors assembled with ultra-high surface area, hierarchically porous carbon exhibits a remarkable performance both at room temperature and at high temperature (60 °C) with maximum energy densities of ∼174 Wh kg-1 (25 °C), and 177 Wh kg-1 (60 °C) - based on active mass of both electrodes. Furthermore, an ultra-high specific power of ∼20 kW kg-1 along with an ultra-stable cycling performance with 90% retention over 150,000 cycles has been achieved even at 60 °C, outperforming supercapacitors assembled with other carbon based materials. These results demonstrate the potential to develop high-performing, green energy storage devices using eco-friendly materials for next generation electric vehicles and other advanced energy storage systems.

Accurate modeling of the hose instability in plasma wakefield accelerators

DOE PAGES

Mehrling, T. J.; Benedetti, C.; Schroeder, C. B.; ...

2018-05-20

Hosing is a major challenge for the applicability of plasma wakefield accelerators and its modeling is therefore of fundamental importance to facilitate future stable and compact plasma-based particle accelerators. In this contribution, we present a new model for the evolution of the plasma centroid, which enables the accurate investigation of the hose instability in the nonlinear blowout regime. Lastly, it paves the road for more precise and comprehensive studies of hosing, e.g., with drive and witness beams, which were not possible with previous models.

Accurate modeling of the hose instability in plasma wakefield accelerators

NASA Astrophysics Data System (ADS)

Mehrling, T. J.; Benedetti, C.; Schroeder, C. B.; Martinez de la Ossa, A.; Osterhoff, J.; Esarey, E.; Leemans, W. P.

2018-05-01

Hosing is a major challenge for the applicability of plasma wakefield accelerators and its modeling is therefore of fundamental importance to facilitate future stable and compact plasma-based particle accelerators. In this contribution, we present a new model for the evolution of the plasma centroid, which enables the accurate investigation of the hose instability in the nonlinear blowout regime. It paves the road for more precise and comprehensive studies of hosing, e.g., with drive and witness beams, which were not possible with previous models.

Accurate modeling of the hose instability in plasma wakefield accelerators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mehrling, T. J.; Benedetti, C.; Schroeder, C. B.

Hosing is a major challenge for the applicability of plasma wakefield accelerators and its modeling is therefore of fundamental importance to facilitate future stable and compact plasma-based particle accelerators. In this contribution, we present a new model for the evolution of the plasma centroid, which enables the accurate investigation of the hose instability in the nonlinear blowout regime. Lastly, it paves the road for more precise and comprehensive studies of hosing, e.g., with drive and witness beams, which were not possible with previous models.

Transformer ratio saturation in a beam-driven wakefield accelerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Farmer, J. P.; Martorelli, R.; Pukhov, A.

We show that for beam-driven wakefield acceleration, the linearly ramped, equally spaced train of bunches typically considered to optimise the transformer ratio only works for flat-top bunches. Through theory and simulation, we explain that this behaviour is due to the unique properties of the plasma response to a flat-top density profile. Calculations of the optimal scaling for a train of Gaussian bunches show diminishing returns with increasing bunch number, tending towards saturation. For a periodic bunch train, a transformer ratio of 23 was achieved for 50 bunches, rising to 40 for a fully optimised beam.

BLIPPED (BLIpped Pure Phase EncoDing) high resolution MRI with low amplitude gradients

NASA Astrophysics Data System (ADS)

Xiao, Dan; Balcom, Bruce J.

2017-12-01

MRI image resolution is proportional to the maximum k-space value, i.e. the temporal integral of the magnetic field gradient. High resolution imaging usually requires high gradient amplitudes and/or long spatial encoding times. Special gradient hardware is often required for high amplitudes and fast switching. We propose a high resolution imaging sequence that employs low amplitude gradients. This method was inspired by the previously proposed PEPI (π Echo Planar Imaging) sequence, which replaced EPI gradient reversals with multiple RF refocusing pulses. It has been shown that when the refocusing RF pulse is of high quality, i.e. sufficiently close to 180°, the magnetization phase introduced by the spatial encoding magnetic field gradient can be preserved and transferred to the following echo signal without phase rewinding. This phase encoding scheme requires blipped gradients that are identical for each echo, with low and constant amplitude, providing opportunities for high resolution imaging. We now extend the sequence to 3D pure phase encoding with low amplitude gradients. The method is compared with the Hybrid-SESPI (Spin Echo Single Point Imaging) technique to demonstrate the advantages in terms of low gradient duty cycle, compensation of concomitant magnetic field effects and minimal echo spacing, which lead to superior image quality and high resolution. The 3D imaging method was then applied with a parallel plate resonator RF probe, achieving a nominal spatial resolution of 17 μm in one dimension in the 3D image, requiring a maximum gradient amplitude of only 5.8 Gauss/cm.

Generation, and applications of stable, 100-500-MeV, dark-current-free beams, from a laser-wakefield accelerator

NASA Astrophysics Data System (ADS)

Banerjee, Sudeep

2011-10-01

This talk will report the production of high energy, quasi-monoenergetic electron bunches without the low-energy electron background that is typically detected from self-injected laser-wakefield accelerators. These electron bunches are produced when the accelerator is operated in the blowout regime, and the laser and plasma parameters are optimized. High-contrast, high power (30-60 TW) and ultra-short-duration (30 fs) laser pulses are focused onto He-gas-jet targets. The high energy (300-400 MeV) monoenergetic (energy spread < 10%) beams are characterized by 1-4-mrad divergence, pointing stability of 1-2 mrad, and a few-percent shot-to-shot fluctuation of peak energy. The results are scalable: the beam energy can be tuned by appropriate choice of acceleration length, laser power and plasma density. Three-dimensional particle-in-cell simulations show that these electron beams are generated when the accelerator is operated near the self-injection threshold, which suppresses dark current (continuous injection in the first bucket). Suppression of dark current is required to minimize noise, improve the quality of secondary radiation sources, and minimize shielding requirements for high repetition-rate operation. Also reported, is the application of this novel electron-beam source to radiography of dense objects with sub-millimeter spatial resolution. In this case, the energetic electron beam is incident on a 2''-thick steel target with embedded voids, which are detected with image plates. Current progress on the generation of GeV energy electron beams with petawatt peak power laser pulses, from the upgraded DIOCLES laser system, will also be discussed. Work supported by U. S. DOE grants DEFG02-05ER15663, DE-FG02-08ER55000; DARPA grant FA9550-09-1-0009; DTRA grant HDTRA1-11-C-0001 and, DHS grant 2007-DN-007-ER0007-02. The laser is supported by AFOSR contracts FA 9550-08-1-0232, FA9550-07-1-0521.

Exploration of very high gradient cavities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eremeev, Grigory

2011-07-01

Several of the 9-cell ILC cavities processed at Jlab within ongoing ILC R&D program have shown interesting behavior at high fields, such as mode mixing and sudden field emission turn-on during quench. Equipped with thermometry and oscillating superleak transducer (OST) system for quench detection, we couple our RF measurements with local dissipation measurements. In this contribution we report on our findings with high gradient SRF cavities.

Link and Network Layers Design for Ultra-High-Speed Terahertz-Band Communications Networks

DTIC Science & Technology

2017-01-01

throughput, and identify the optimal parameter values for their design (Sec. 6.2.3). Moreover, we validate and test the scheme with experimental data obtained...LINK AND NETWORK LAYERS DESIGN FOR ULTRA-HIGH- SPEED TERAHERTZ-BAND COMMUNICATIONS NETWORKS STATE UNIVERSITY OF NEW YORK (SUNY) AT BUFFALO JANUARY...TYPE FINAL TECHNICAL REPORT 3. DATES COVERED (From - To) FEB 2015 – SEP 2016 4. TITLE AND SUBTITLE LINK AND NETWORK LAYERS DESIGN FOR ULTRA-HIGH

Characterization of peak capacity of microbore liquid chromatography columns using gradient kinetic plots.

PubMed

Hetzel, Terence; Blaesing, Christina; Jaeger, Martin; Teutenberg, Thorsten; Schmidt, Torsten C

2017-02-17

The performance of micro-liquid chromatography columns with an inner diameter of 0.3mm was investigated on a dedicated micro-LC system for gradient elution. Core-shell as well as fully porous particle packed columns were compared on the basis of peak capacity and gradient kinetic plot limits. The results for peak capacity showed the superior performance of columns packed with sub-2μm fully porous particles compared to 3.0μm fully porous and 2.7μm core-shell particles within a range of different gradient time to column void time ratios. For ultra-fast chromatography a maximum peak capacity of 16 can be obtained using a 30s gradient for the sub-2μm fully porous particle packed column. A maximum peak capacity of 121 can be achieved using a 5min gradient. In addition, the influence of an alternative detector cell on the basis of optical waveguide technology and contributing less to system variance was investigated showing an increased peak capacity for all applied gradient time/column void time ratios. Finally, the influence of pressure was evaluated indicating increased peak capacity for maximum performance whereas a limited benefit for ultra-fast chromatography with gradient times below 30s was observed. Copyright © 2017 Elsevier B.V. All rights reserved.

Nonlinear evolutions of an ultra-intense ultra-short laser pulse in a rarefied plasma through a new quasi-static theory

NASA Astrophysics Data System (ADS)

Yazdanpanah, J.

2018-02-01

In this paper, we present a new description of self-consistent wake excitation by an intense short laser pulse, based on applying the quasi-static approximation (slow variations of the pulse-envelope) in the instantaneous Lorentz-boosted pulse co-moving frame (PCMF), and best verify our results through comparison with particle-in-cell simulations. According to this theory, the plasma motion can be treated perturbatively in the PCMF due to its high initial-velocity and produces a quasi-static wakefield in this frame. The pulse envelope, on the other hand, is governed by a form of the Schrödinger equation in the PCMF, in which the wakefield acts as an effective potential. In this context, pulse evolutions are characterized by local conservation laws resulted from this equation and subjected to Lorentz transformation into the laboratory frame. Using these conservation laws, precise formulas are obtained for spatiotemporal pulse evolutions and related wakefield variations at initial stages, and new equations are derived for instantaneous group velocity and carrier frequency. In addition, based on properties of the Schrödinger equation, spectral-evolutions of the pulse are described and the emergence of an anomalous dispersion branch with linear relation ω ≈ ck (c is the light speed) is predicted. Our results are carefully discussed versus previous publications and the significance of our approach is described by showing almost all suggestive definitions of group-velocity based on energy arguments fail to reproduce our formula and correctly describe the instantaneous pulse-velocity.

Adaptive sensor-based ultra-high accuracy solar concentrator tracker

NASA Astrophysics Data System (ADS)

Brinkley, Jordyn; Hassanzadeh, Ali

2017-09-01

Conventional solar trackers use information of the sun's position, either by direct sensing or by GPS. Our method uses the shading of the receiver. This, coupled with nonimaging optics design allows us to achieve ultra-high concentration. Incorporating a sensor based shadow tracking method with a two stage concentration solar hybrid parabolic trough allows the system to maintain high concentration with acute accuracy.

High-efficiency water-loaded microwave antenna in ultra-high-frequency band

NASA Astrophysics Data System (ADS)

Gong, Zilun; Bartone, Chris; Yang, Fuyi; Yao, Jie

2018-03-01

High-index dielectrics are widely used in microwave antennas to control the radiation characteristics. Liquid water, with a high dielectric index at microwave frequency, is an interesting material to achieving tunable functionalities. Here, we demonstrate a water-loaded microwave antenna system that has high loss-tolerance and wideband tunability enabled by fluidity. Our simulation and experimental results show that the resonance frequency can be effectively tuned by the size of loading water. Furthermore, the antenna systems with water loading can achieve high radiation efficiency (>90%) in the ultra-high-frequency (0.3-3 GHz) band. This work brings about opportunities in realistic tunable microwave antenna designs enabled by liquid.

Electron self-injection in the donut bubble wakefield

NASA Astrophysics Data System (ADS)

Firouzjaei, Ali Shekari; Shokri, Babak

2018-05-01

We investigate electron self-injection in a donut bubble wakefield driven by a Laguerre-Gauss laser pulse. The present work discusses the electron capture by modeling the analytical donut bubble field. We discuss the self-injection of the electrons from plasma for various initial conditions and then compare the results. We show that the donut bubble can trap plasma electrons forming a hollow beam. We present the phase spaces and longitudinal momentum evolution for the trapped electrons in the bubble and discuss their characteristic behaviors and stability. It will be shown that the electrons self-injected in the front are ideal for applications in which a good stability and low energy spread are essential.

UltraSail CubeSat Solar Sail Flight Experiment

NASA Technical Reports Server (NTRS)

Carroll, David; Burton, Rodney; Coverstone, Victoria; Swenson, Gary

2013-01-01

, while using solar photon pressure to slew the spin axis. Vacuum tests have also verified that electrostatic and molecular adhesion forces can substantially be eliminated by making the film electrically conductive, reducing the peel force of the film off the storage roll to levels of 100s of micro-N. The innovation demonstrated the capability of deploying a six-micron aluminum- coated film from a reel through a slit in vacuum. The innovation also demonstrated a spin-stabilized method for deploying a long reel of solar sail film using solar pressure to spin-up and orbit raise the satellite, and also a gravity gradient method for deploying a long reel of solar sail film using solar pressure to orbit raise the satellite. The solar sail mass fraction of 25% is consistent with high specific impulse ion systems, but without the added weight and cost of a power source and processing unit. The large sail area, coupled with low film density, is giving UltraSail a high payload fraction. The UltraSail deployment scheme unrolls a micrometerscale reflection-coated polyimide film from a storage mandrel to a maximum length of several kilometers with the aid of a blade tip satellite.

Ultra-compact high-performance MCT MWIR engine

NASA Astrophysics Data System (ADS)

Lutz, H.; Breiter, R.; Eich, D.; Figgemeier, H.; Oelmaier, R.; Rutzinger, S.; Schenk, H.; Wendler, J.

2017-02-01

Size, weight and power (SWaP) reduction is highly desired by applications such as sights for the dismounted soldier or small gimbals for UAVs. But why have high performance and small size of IR systems inevitably exclude each other? Namely, recent development progress in the fields of miniature cryocoolers, short dewars and high operating temperature (HOT) FPAs combined with pitch size reduction opens the door for very compact MWIR-modules while keeping high electro-optical performance. Now, AIM has realized first prototypes of an ultra-compact high-performance MWIR engine in a total volume of only 18cl (60mm length x 60mm height x 50mm width). Impressive SWaP characteristics are completed by a total weight below 400g and a power consumption < 4W in basic imaging mode. The engine consists of a XGA-format (1024x768) MCT detector array with 10μm pitch and a low power consuming ROIC. It is cooled down to a typical operating temperature of 160K by the miniature linear cryocooler SX020. The dewar uses a short coldfinger and is designed to reduce the heat load as much as possible. The cooler drive electronics is implemented in the CCE layout in order to reduce the required space of the printed boards and to save power. Uncorrected 14bit video data is provided via Camera Link. Optionally, a small image processing board can be stacked on top of the CCE to gain access to basic functions such as BPR, 2- point NUC and dynamic reduction. This paper will present the design, functionalities and performance data of the ultra-compact MCT MWIR engine operated at HOT.

Improved performance of laser wakefield acceleration by tailored self-truncated ionization injection

NASA Astrophysics Data System (ADS)

Irman, A.; Couperus, J. P.; Debus, A.; Köhler, A.; Krämer, J. M.; Pausch, R.; Zarini, O.; Schramm, U.

2018-04-01

We report on tailoring ionization-induced injection in laser wakefield acceleration so that the electron injection process is self-truncating following the evolution of the plasma bubble. Robust generation of high-quality electron beams with shot-to-shot fluctuations of the beam parameters better than 10% is presented in detail. As a novelty, the scheme was found to enable well-controlled yet simple tuning of the injected charge while preserving acceleration conditions and beam quality. Quasi-monoenergetic electron beams at several 100 MeV energy and 15% relative energy spread were routinely demonstrated with a total charge of the monoenergetic feature reaching 0.5 nC. Finally these unique beam parameters, suggesting unprecedented peak currents of several 10 kA, are systematically related to published data on alternative injection schemes.

PFISR GPS tracking mode for researching high-latitude ionospheric electron density gradients associated with GPS scintillation

NASA Astrophysics Data System (ADS)

Loucks, D. C.; Palo, S. E.; Pilinski, M.; Crowley, G.; Azeem, S. I.; Hampton, D. L.

2016-12-01

Ionospheric behavior in the high-latitudes can significantly impact Ultra High Frequency (UHF) signals in the 300 MHz to 3 GHz band, resulting in degradation of Global Positioning System (GPS) position solutions and satellite communications interruptions. To address these operational concerns, a need arises to identify and understand the ionospheric structure that leads to disturbed conditions in the Arctic. Structures in the high-latitude ionosphere are known to change on the order of seconds or less, can be decameters to kilometers in scale, and elongate across magnetic field lines at auroral latitudes. Nominal operations at Poker Flat Incoherent Scatter Radar (PFISR) give temporal resolution on the order of minutes, and range resolution on the order of tens of kilometers, while specialized GPS receivers available for ionospheric sensing have a 100Hz observation sampling rate. One of these, ASTRA's Connected Autonomous Space Environment Sensor (CASES) is used for this study. We have developed a new GPS scintillation tracking mode for PFISR to address open scientific questions regarding temporal and spatial electron density gradients. The mode will be described, a number of experimental campaigns will be analyzed, and results and lessons learned will be presented.

Bond Behavior of Reinforcing Steel in Ultra-High Performance Concrete

DOT National Transportation Integrated Search

2014-11-01

Ultra-high performance concrete (UHPC) has garnered interest from the highway infrastructure community for its greatly enhanced mechanical and durability properties. The objective of this research is to extensively evaluate the factors that affect bo...

Waste heat recovery with ultra high-speed turbomachinery

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vakkilainen, E.; Larjola, J.; Lindgren, O.

1984-08-01

A new ORC heat recovery system which converts waste heat to electricity has been developed in Lappeenranta University of Technology with support from Department of Energy in Finnish Ministry of Trade and Industry. Use of ultra high-speed turbomachinery (10 000 rpm - 200 000 rpm) promises lower unit costs, higher efficiencies and fast amortization rate, 2,4 - 3,0 years.

[Reparative Osteogenesis and Angiogenesis in Low Intensity Electromagnetic Radiation of Ultra-High Frequency].

PubMed

Iryanov, Y M; Kiryanov, N A

2015-01-01

Non-drug correction of reparative bone tissue regeneration in different pathological states - one of the most actual problems of modern medicine. Our aim was to conduct morphological analysis of the influence of electromagnetic radiation of ultra-high frequency and low intensity on reparative osteogenesis and angiogenesis in fracture treatment under transosseous osteosynthesis. A controlled nonrandomized study was carried out. In the experiment conducted on rats we modeled tibial fracture with reposition and fixation of the bone fragments both in control and experimental groups. In the animals of the experimental group the fracture zone was exposed to low intensity electromagnetic radiation of ultra-high frequency. Exposure simulation was performed in the control group. The operated bones were examined using radiography, light and electronic microscopy, X-ray electronic probe microanalysis. It has been established that electromagnetic radiation of ultra-high frequency sessions in fracture treatment stimulate secretory activity and degranulation of mast cells, produce microcirculatory bed vascular permeability increase, endotheliocyte migration phenotype expression, provide endovascular endothelial outgrowth formation, activate reparative osteogenesis and angiogenesis while fracture reparation becomes the one of the primary type. The full periosteal, intermediary and intraosteal bone union was defined in 28 days. Among the therapeutic benefits of electromagnetic radiation of ultra-high frequency in fracture treatment we can detect mast cell secretorv activity stimulation and endovascular anziozenesis activation.

Development of Non-Proprietary Ultra-High Performance Concrete : Final Report

DOT National Transportation Integrated Search

2017-12-01

Ultra-high performance concrete (UHPC) has mechanical and durability properties that far exceed those of conventional concrete. Particularly, UHPC has compressive and post-cracking tensile strengths of around 20 ksi and 0.72 ksi, respectively. Thus, ...

Development of 873 nm Raman Seed Pulse for Raman-seeded Laser Wakefield Acceleration

NASA Astrophysics Data System (ADS)

Grigsby, F.; Peng, D.; Downer, M. C.

2004-12-01

By using a Raman-shifted seed pulse coincident with a main driving pulse, laser wakefields can be generated with sub-relativistic intensity, coherent control and high repetition rate in the self-modulated regime. Experimentally, the generation of a chirped Stokes laser pulse by inserting a solid state Raman shifter, Ba(NO3)2, into a CPA system before the compressor (to suppress self-phase modulation) will be described. We will also report on design, modeling and experimental demonstration of a novel compressor for the Stokes pulse that uses a mismatched grating pair to achieve a near transform-limited seed pulse. Finally, we will describe the design, simulation and current status of Raman-seeded LWFA experiments that use this novel source.

Inactivation of Bacillus spores inoculated in milk by Ultra High Pressure Homogenization.

PubMed

Amador Espejo, Genaro Gustavo; Hernández-Herrero, M M; Juan, B; Trujillo, A J

2014-12-01

Ultra High-Pressure Homogenization treatments at 300 MPa with inlet temperatures (Ti) of 55, 65, 75 and 85 °C were applied to commercial Ultra High Temperature treated whole milk inoculated with Bacillus cereus, Bacillus licheniformis, Bacillus sporothermodurans, Bacillus coagulans, Geobacillus stearothermophilus and Bacillus subtilis spores in order to evaluate the inactivation level achieved. Ultra High-Pressure Homogenization conditions at 300 MPa with Ti = 75 and 85 °C were capable of a spore inactivation of ∼5 log CFU/mL. Furthermore, under these processing conditions, commercial sterility (evaluated as the complete inactivation of the inoculated spores) was obtained in milk, with the exception of G. stearothermophilus and B. subtilis treated at 300 MPa with Ti = 75 °C. The results showed that G. stearothermophilus and B. subtilis have higher resistance to the Ultra High-Pressure Homogenization treatments applied than the other microorganisms inoculated and that a treatment performed at 300 MPa with Ti = 85 °C was necessary to completely inactivate these microorganisms at the spore level inoculated (∼1 × 10(6) CFU/mL). Besides, a change in the resistance of B. licheniformis, B. sporothermodurans, G. stearothermophilus and B. subtilis spores was observed as the inactivation obtained increased remarkably in treatments performed with Ti between 65 and 75 °C. This study provides important evidence of the suitability of UHPH technology for the inactivation of spores in high numbers, leading to the possibility of obtaining commercially sterile milk. Copyright © 2014 Elsevier Ltd. All rights reserved.

Generating multi-GeV electron bunches using single stage laser wakefield acceleration in a 3D nonlinear regime

NASA Astrophysics Data System (ADS)

Lu, W.; Tzoufras, M.; Joshi, C.; Tsung, F. S.; Mori, W. B.; Vieira, J.; Fonseca, R. A.; Silva, L. O.

2007-06-01

The extraordinary ability of space-charge waves in plasmas to accelerate charged particles at gradients that are orders of magnitude greater than in current accelerators has been well documented. We develop a phenomenological framework for laser wakefield acceleration (LWFA) in the 3D nonlinear regime, in which the plasma electrons are expelled by the radiation pressure of a short pulse laser, leading to nearly complete blowout. Our theory provides a recipe for designing a LWFA for given laser and plasma parameters and estimates the number and the energy of the accelerated electrons whether self-injected or externally injected. These formulas apply for self-guided as well as externally guided pulses (e.g. by plasma channels). We demonstrate our results by presenting a sample particle-in-cell (PIC) simulation of a 30fs, 200 TW laser interacting with a 0.75 cm long plasma with density 1.5×1018cm-3 to produce an ultrashort (10 fs) monoenergetic bunch of self-injected electrons at 1.5 GeV with 0.3 nC of charge. For future higher-energy accelerator applications, we propose a parameter space, which is distinct from that described by Gordienko and Pukhov [Phys. Plasmas 12, 043109 (2005)PHPAEN1070-664X10.1063/1.1884126] in that it involves lower plasma densities and wider spot sizes while keeping the intensity relatively constant. We find that this helps increase the output electron beam energy while keeping the efficiency high.

Preprocessing of gravity gradients at the GOCE high-level processing facility

NASA Astrophysics Data System (ADS)

Bouman, Johannes; Rispens, Sietse; Gruber, Thomas; Koop, Radboud; Schrama, Ernst; Visser, Pieter; Tscherning, Carl Christian; Veicherts, Martin

2009-07-01

One of the products derived from the gravity field and steady-state ocean circulation explorer (GOCE) observations are the gravity gradients. These gravity gradients are provided in the gradiometer reference frame (GRF) and are calibrated in-flight using satellite shaking and star sensor data. To use these gravity gradients for application in Earth scienes and gravity field analysis, additional preprocessing needs to be done, including corrections for temporal gravity field signals to isolate the static gravity field part, screening for outliers, calibration by comparison with existing external gravity field information and error assessment. The temporal gravity gradient corrections consist of tidal and nontidal corrections. These are all generally below the gravity gradient error level, which is predicted to show a 1/ f behaviour for low frequencies. In the outlier detection, the 1/ f error is compensated for by subtracting a local median from the data, while the data error is assessed using the median absolute deviation. The local median acts as a high-pass filter and it is robust as is the median absolute deviation. Three different methods have been implemented for the calibration of the gravity gradients. All three methods use a high-pass filter to compensate for the 1/ f gravity gradient error. The baseline method uses state-of-the-art global gravity field models and the most accurate results are obtained if star sensor misalignments are estimated along with the calibration parameters. A second calibration method uses GOCE GPS data to estimate a low-degree gravity field model as well as gravity gradient scale factors. Both methods allow to estimate gravity gradient scale factors down to the 10-3 level. The third calibration method uses high accurate terrestrial gravity data in selected regions to validate the gravity gradient scale factors, focussing on the measurement band. Gravity gradient scale factors may be estimated down to the 10-2 level with this

High longitudinal relaxivity of ultra-small gadolinium oxide prepared by microsecond laser ablation in diethylene glycol

NASA Astrophysics Data System (ADS)

Luo, Ningqi; Tian, Xiumei; Xiao, Jun; Hu, Wenyong; Yang, Chuan; Li, Li; Chen, Dihu

2013-04-01

Ultra-small gadolinium oxide (Gd2O3) can be used as T1-weighted Magnetic Resonance Imaging (MRI) contrast agent own to its high longitudinal relaxivity (r1) and has attracted intensive attention in these years. In this paper, ultra-small Gd2O3 nanoparticles of 3.8 nm in diameter have been successfully synthesized by a microsecond laser ablating a gadolinium (Gd) target in diethylene glycol (DEG). The growth inhibition effect induced by the large viscosity of DEG makes it possible to synthesize ultra-small Gd2O3 by laser ablation in DEG. The r1 value and T1-weighted MR images are measured by a 3.0 T MRI spectroscope. The results show these nanoparticles with a high r1 value of 9.76 s-1 mM-1 to be good MRI contrast agents. We propose an explanation for the high r1 value of ultra-small Gd2O3 by considering the decreasing factor (surface to volume ratio of the nanoparticles, S/V) and the increasing factor (water hydration number of the Gd3+ on Gd2O3 surface, q), which offer a new look into the relaxivity studies of MRI contrast agents. Our research provides a new approach to preparing ultra-small Gd2O3 of high r1 value by laser ablation in DEG and develops the understanding of high relaxivity of ultra-small Gd2O3 MRI contrast agents.

Accuracy of Gradient Reconstruction on Grids with High Aspect Ratio

NASA Technical Reports Server (NTRS)

Thomas, James

2008-01-01

Gradient approximation methods commonly used in unstructured-grid finite-volume schemes intended for solutions of high Reynolds number flow equations are studied comprehensively. The accuracy of gradients within cells and within faces is evaluated systematically for both node-centered and cell-centered formulations. Computational and analytical evaluations are made on a series of high-aspect-ratio grids with different primal elements, including quadrilateral, triangular, and mixed element grids, with and without random perturbations to the mesh. Both rectangular and cylindrical geometries are considered; the latter serves to study the effects of geometric curvature. The study shows that the accuracy of gradient reconstruction on high-aspect-ratio grids is determined by a combination of the grid and the solution. The contributors to the error are identified and approaches to reduce errors are given, including the addition of higher-order terms in the direction of larger mesh spacing. A parameter GAMMA characterizing accuracy on curved high-aspect-ratio grids is discussed and an approximate-mapped-least-square method using a commonly-available distance function is presented; the method provides accurate gradient reconstruction on general grids. The study is intended to be a reference guide accompanying the construction of accurate and efficient methods for high Reynolds number applications

Ultra-high vacuum photoelectron linear accelerator

DOEpatents

Yu, David U.L.; Luo, Yan

2013-07-16

An rf linear accelerator for producing an electron beam. The outer wall of the rf cavity of said linear accelerator being perforated to allow gas inside said rf cavity to flow to a pressure chamber surrounding said rf cavity and having means of ultra high vacuum pumping of the cathode of said rf linear accelerator. Said rf linear accelerator is used to accelerate polarized or unpolarized electrons produced by a photocathode, or to accelerate thermally heated electrons produced by a thermionic cathode, or to accelerate rf heated field emission electrons produced by a field emission cathode.

The effect of cognitive remediation in individuals at ultra-high risk for psychosis: a systematic review.

PubMed

Glenthøj, Louise Birkedal; Hjorthøj, Carsten; Kristensen, Tina Dam; Davidson, Charlie Andrew; Nordentoft, Merete

2017-01-01

Cognitive deficits are prominent features of the ultra-high risk state for psychosis that are known to impact functioning and course of illness. Cognitive remediation appears to be the most promising treatment approach to alleviate the cognitive deficits, which may translate into functional improvements. This study systematically reviewed the evidence on the effectiveness of cognitive remediation in the ultra-high risk population. The electronic databases MEDLINE, PsycINFO, and Embase were searched using keywords related to cognitive remediation and the UHR state. Studies were included if they were peer-reviewed, written in English, and included a population meeting standardized ultra-high risk criteria. Six original research articles were identified. All the studies provided computerized, bottom-up-based cognitive remediation, predominantly targeting neurocognitive function. Four out of five studies that reported a cognitive outcome found cognitive remediation to improve cognition in the domains of verbal memory, attention, and processing speed. Two out of four studies that reported on functional outcome found cognitive remediation to improve the functional outcome in the domains of social functioning and social adjustment. Zero out of the five studies that reported such an outcome found cognitive remediation to affect the magnitude of clinical symptoms. Research on the effect of cognitive remediation in the ultra-high risk state is still scarce. The current state of evidence indicates an effect of cognitive remediation on cognition and functioning in ultra-high risk individuals. More research on cognitive remediation in ultra-high risk is needed, notably in large-scale trials assessing the effect of neurocognitive and/or social cognitive remediation on multiple outcomes.

Gas-Enhanced Ultra-High Shear Mixing: A Concept and Applications

NASA Astrophysics Data System (ADS)

Czerwinski, Frank; Birsan, Gabriel

2017-04-01

The processes of mixing, homogenizing, and deagglomeration are of paramount importance in many industries for modifying properties of liquids or liquid-based dispersions at room temperature and treatment of molten or semi-molten alloys at high temperatures, prior to their solidification. To implement treatments, a variety of technologies based on mechanical, electromagnetic, and ultrasonic principles are used commercially or tested at the laboratory scale. In a large number of techniques, especially those tailored toward metallurgical applications, the vital role is played by cavitation, generation of gas bubbles, and their interaction with the melt. This paper describes a novel concept exploring an integration of gas injection into the shear zone with ultra-high shear mixing. As revealed via experiments with a prototype of the cylindrical rotor-stator apparatus and transparent media, gases injected radially through the high-speed rotor generate highly refined bubbles of high concentration directly in the shear zone of the mixer. It is believed that an interaction of large volume of fine gas bubbles with the liquid, superimposed on ultra-high shear, will enhance mixing capabilities and cause superior refining and homogenizing of the liquids or solid-liquid slurries, thus allowing their effective property modification.

Controlled droplet transport to target on a high adhesion surface with multi-gradients

PubMed Central

Deng, Siyan; Shang, Weifeng; Feng, Shile; Zhu, Shiping; Xing, Yan; Li, Dan; Hou, Yongping; Zheng, Yongmei

2017-01-01

We introduce multi-gradients including Laplace pressure gradient, wettable gradient and wettable different gradient on a high adhesion surface via special wedge-pattern and improved anodic oxidation method. As a result of the cooperative effect mentioned above, controlled directional motion of a droplet on a high adhesion surface is realized, even when the surface is turned upside down. The droplet motion can be predicted and the movement distances can be controlled by simply adjusting the wedge angle and droplet volume. More interestingly, when Laplace pressure gradient is introduced on a V-shaped wettable gradient surface, two droplets can move toward one another as designed. PMID:28368020

Metabolomic characterization of rhubarb species by capillary electrophoresis and ultra-high-pressure liquid chromatography.

PubMed

Tseng, Yufeng Jane; Kuo, Chun-Ting; Wang, San-Yuan; Liao, Hsiao-Wei; Chen, Guan-Yuan; Ku, Yuan-Ling; Shao, Wei-Cheng; Kuo, Ching-Hua

2013-10-01

This study developed CE and ultra-high-pressure LC (UHPLC) methods coupled with UV detectors to characterize the metabolomic profiles of different rhubarb species. The optimal CE conditions used a BGE with 15 mM sodium tetraborate, 15 mM sodium dihydrogen phosphate monohydrate, 30 mM sodium deoxycholate, and 30% ACN v/v at pH 8.3. The optimal UHPLC conditions used a mobile phase composed of 0.05% phosphate buffer and ACN with gradient elution. The gradient profile increased linearly from 10 to 21% ACN within the first 25 min, then increased to 33% ACN for the next 10 min. It took another 5 min to reach the 65% ACN, then for the next 5 min, it stayed unchanged. Sixteen samples of Rheum officinale and Rheum tanguticum collected from various locations were analyzed by CE and UHPLC methods. The metabolite profiles of CE were aligned and baseline corrected before chemometric analysis. Metabolomic signatures of rhubarb species from CE and UHPLC were clustered using principle component analysis and distance-based redundancy analysis; the clusters were not only able to discriminate different species but also different cultivation regions. Similarity measurements were performed by calculating the correlation coefficient of each sample with the authentic samples. Hybrid rhizome was clearly identified through similarity measurement of UHPLC metabolite profile and later confirmed by gene sequencing. The present study demonstrated that CE and UHPLC are efficient and effective tools to identify and authenticate herbs even coupled with simple detectors. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ultra-high speed vacuum pump system with first stage turbofan and second stage turbomolecular pump

DOEpatents

Jostlein, Hans

2006-04-04

An ultra-high speed vacuum pump evacuation system includes a first stage ultra-high speed turbofan and a second stage conventional turbomolecular pump. The turbofan is either connected in series to a chamber to be evacuated, or is optionally disposed entirely within the chamber. The turbofan employs large diameter rotor blades operating at high linear blade velocity to impart an ultra-high pumping speed to a fluid. The second stage turbomolecular pump is fluidly connected downstream from the first stage turbofan. In operation, the first stage turbofan operates in a pre-existing vacuum, with the fluid asserting only small axial forces upon the rotor blades. The turbofan imparts a velocity to fluid particles towards an outlet at a high volume rate, but moderate compression ratio. The second stage conventional turbomolecular pump then compresses the fluid to pressures for evacuation by a roughing pump.

Automatic Beam Path Analysis of Laser Wakefield Particle Acceleration Data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rubel, Oliver; Geddes, Cameron G.R.; Cormier-Michel, Estelle

2009-10-19

Numerical simulations of laser wakefield particle accelerators play a key role in the understanding of the complex acceleration process and in the design of expensive experimental facilities. As the size and complexity of simulation output grows, an increasingly acute challenge is the practical need for computational techniques that aid in scientific knowledge discovery. To that end, we present a set of data-understanding algorithms that work in concert in a pipeline fashion to automatically locate and analyze high energy particle bunches undergoing acceleration in very large simulation datasets. These techniques work cooperatively by first identifying features of interest in individual timesteps,more » then integrating features across timesteps, and based on the information derived perform analysis of temporally dynamic features. This combination of techniques supports accurate detection of particle beams enabling a deeper level of scientific understanding of physical phenomena than hasbeen possible before. By combining efficient data analysis algorithms and state-of-the-art data management we enable high-performance analysis of extremely large particle datasets in 3D. We demonstrate the usefulness of our methods for a variety of 2D and 3D datasets and discuss the performance of our analysis pipeline.« less

High power tests of an electroforming cavity operating at 11.424 GHz

NASA Astrophysics Data System (ADS)

Dolgashev, V. A.; Gatti, G.; Higashi, Y.; Leonardi, O.; Lewandowski, J. R.; Marcelli, A.; Rosenzweig, J.; Spataro, B.; Tantawi, S. G.; Yeremian, D. A.

2016-03-01

The achievement of ultra high accelerating gradients is mandatory in order to fabricate compact accelerators at 11.424 GHz for scientific and industrial applications. An extensive experimental and theoretical program to determine a reliable ultra high gradient operation of the future linear accelerators is under way in many laboratories. In particular, systematic studies on the 11.424 GHz frequency accelerator structures, R&D on new materials and the associated microwave technology are in progress to achieve accelerating gradients well above 120 MeV/m. Among the many, the electroforming procedure is a promising approach to manufacture high performance RF devices in order to avoid the high temperature brazing and to produce precise RF structures. We report here the characterization of a hard high gradient RF accelerating structure at 11.424 GHz fabricated using the electroforming technique. Low-level RF measurements and high power RF tests carried out at the SLAC National Accelerator Laboratory on this prototype are presented and discussed. In addition, we present also a possible layout where the water-cooling of irises based on the electroforming process has been considered for the first time.

Acceleration and evolution of a hollow electron beam in wakefields driven by a Laguerre-Gaussian laser pulse

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Guo-Bo; College of Science, National University of Defense Technology, Changsha 410073; Chen, Min, E-mail: minchen@sjtu.edu.cn, E-mail: yanyunma@126.com

2016-03-15

We show that a ring-shaped hollow electron beam can be injected and accelerated by using a Laguerre-Gaussian laser pulse and ionization-induced injection in a laser wakefield accelerator. The acceleration and evolution of such a hollow, relativistic electron beam are investigated through three-dimensional particle-in-cell simulations. We find that both the ring size and the beam thickness oscillate during the acceleration. The beam azimuthal shape is angularly dependent and evolves during the acceleration. The beam ellipticity changes resulting from the electron angular momenta obtained from the drive laser pulse and the focusing forces from the wakefield. The dependence of beam ring radiusmore » on the laser-plasma parameters (e.g., laser intensity, focal size, and plasma density) is studied. Such a hollow electron beam may have potential applications for accelerating and collimating positively charged particles.« less

Proposed Ultra-High Sensitivity High-Frequency Gravitational Wave Detector

NASA Astrophysics Data System (ADS)

Baker, Robert M. L.; Stephenson, Gary V.; Li, Fangyu

2008-01-01

The paper discusses the proposed improvement of a High-Frequency Relic Gravitational Wave (HFRGW) detector designed by Li, Baker, Fang, Stephenson and Chen in order to greatly improve its sensitivity. The improved detector is inspired by the Laser Interferometer Gravitational Observatory or LIGO, but is sensitive to the high-frequency end of the gravitational-wave spectrum. As described in prior papers it utilizes the Gertsenshtein effect, which introduces the conversion of gravitational waves to electromagnetic (EM) waves in the presence of a static magnetic field. Such a conversion, if it leads to photons moving in a direction perpendicular to the plane of the EM waves and the magnetic field, will allow for ultra-high sensitivity HFRGW detection. The use of sensitive microwave, single photon detectors such as a circuit QED and/or the Rydberg Atom Cavity Detector, or off-the-shelf detectors, could lead to such detection. When the EM-detection photons are focused at the microwave detectors by fractal-membrane reflectors sensitivity is also improved. Noise sources external to the HFRGW detector will be eliminated by placing a tight mosaic of superconducting tiles (e.g., YBCO) and/or fractal membranes on the interior surface of the detector's cryogenic containment vessel in order to provide a perfect Faraday cage. Internal thermal noise will be eliminated by means of a microwave absorbing (or reflecting) interior enclosure shaped to conform to a high-intensity continuous microwave Gaussian beam (GB), will reduce any background photon flux (BPF) noise radiated normal to the GB's axis. Such BPF will be further attenuated by a series of microwave absorbing baffles forming tunnels to the sensitive microwave detectors on each side of the GB and at right angles to the static magnetic field. A HFGW detector of bandwidth of 1 KHz to 10 KHz or less in the GHz band has been selected. It is concluded that the utilization of the new ultra-high-sensitivity microwave detectors

Wakefield potentials of corrugated structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Novokhatski, A.

A corrugated structure, which is used in “dechirper” devices, is usually a pipe or two plates with small corrugations (bumps) on the walls. There is a good single-mode description of the wake potentials excited by a relativistic bunch if the wave length of the mode is much longer than the distance between the bumps in the pipe. However, ultrashort bunches, which are now used in free electron lasers, excite much higher frequency fields and the corresponding wake potentials will be very different from the single-mode description. We have made analyses of these wake potentials based on a numerical solution ofmore » Maxwell’s equations. It was confirmed that the behavior of the wakefields of ultrashort bunches in corrugated structures is not much different from the fields excited usually in accelerating structures where the wake potentials are described by the exponential function. For a practical application we present results for the SLAC “dechirper.” We also carried out calculations for a similar device, that was installed and measured at the Pohang Accelerator Laboratory, Korea. As a result, we find very good agreement with the experimental results.« less

Wakefield potentials of corrugated structures

DOE PAGES

Novokhatski, A.

2015-10-22

A corrugated structure, which is used in “dechirper” devices, is usually a pipe or two plates with small corrugations (bumps) on the walls. There is a good single-mode description of the wake potentials excited by a relativistic bunch if the wave length of the mode is much longer than the distance between the bumps in the pipe. However, ultrashort bunches, which are now used in free electron lasers, excite much higher frequency fields and the corresponding wake potentials will be very different from the single-mode description. We have made analyses of these wake potentials based on a numerical solution ofmore » Maxwell’s equations. It was confirmed that the behavior of the wakefields of ultrashort bunches in corrugated structures is not much different from the fields excited usually in accelerating structures where the wake potentials are described by the exponential function. For a practical application we present results for the SLAC “dechirper.” We also carried out calculations for a similar device, that was installed and measured at the Pohang Accelerator Laboratory, Korea. As a result, we find very good agreement with the experimental results.« less

Design of Ultra-High Temperature Ceramics for Improved Performance

DTIC Science & Technology

2009-02-28

e.g., grain boundary chemistry or change in impurity concentrations) or physical (e.g., residual stress) effects. 600 co 500 a. oi400 c CD i...SA037 Effects of oxygen content on the properties of supcr-high-teiiiperature resistant Si-AI- C fibers D.f. Zhao (National University of Defense...of Technology, China) 15:05 S A034 Oxyacetylene ablation behavior of carbon fibers reinforced carbon matrix and ultra-high temperature

mrsFAST-Ultra: a compact, SNP-aware mapper for high performance sequencing applications.

PubMed

Hach, Faraz; Sarrafi, Iman; Hormozdiari, Farhad; Alkan, Can; Eichler, Evan E; Sahinalp, S Cenk

2014-07-01

High throughput sequencing (HTS) platforms generate unprecedented amounts of data that introduce challenges for processing and downstream analysis. While tools that report the 'best' mapping location of each read provide a fast way to process HTS data, they are not suitable for many types of downstream analysis such as structural variation detection, where it is important to report multiple mapping loci for each read. For this purpose we introduce mrsFAST-Ultra, a fast, cache oblivious, SNP-aware aligner that can handle the multi-mapping of HTS reads very efficiently. mrsFAST-Ultra improves mrsFAST, our first cache oblivious read aligner capable of handling multi-mapping reads, through new and compact index structures that reduce not only the overall memory usage but also the number of CPU operations per alignment. In fact the size of the index generated by mrsFAST-Ultra is 10 times smaller than that of mrsFAST. As importantly, mrsFAST-Ultra introduces new features such as being able to (i) obtain the best mapping loci for each read, and (ii) return all reads that have at most n mapping loci (within an error threshold), together with these loci, for any user specified n. Furthermore, mrsFAST-Ultra is SNP-aware, i.e. it can map reads to reference genome while discounting the mismatches that occur at common SNP locations provided by db-SNP; this significantly increases the number of reads that can be mapped to the reference genome. Notice that all of the above features are implemented within the index structure and are not simple post-processing steps and thus are performed highly efficiently. Finally, mrsFAST-Ultra utilizes multiple available cores and processors and can be tuned for various memory settings. Our results show that mrsFAST-Ultra is roughly five times faster than its predecessor mrsFAST. In comparison to newly enhanced popular tools such as Bowtie2, it is more sensitive (it can report 10 times or more mappings per read) and much faster (six times or

MDOT aims for lower-cost ultra-high performance concrete : research spotlight.

DOT National Transportation Integrated Search

2016-08-01

In recent years, several vendors have developed ultra-high performance : concrete (UHPC) that surpasses traditional concrete mixes by offering : exceptional freeze-thaw resistance, reduced susceptibility to cracking : and far less reinforcement corro...

Multilayer ultra-high-temperature ceramic coatings

DOEpatents

Loehman, Ronald E [Albuquerque, NM; Corral, Erica L [Tucson, AZ

2012-03-20

A coated carbon-carbon composite material with multiple ceramic layers to provide oxidation protection from ultra-high-temperatures, where if the carbon-carbon composite material is uninhibited with B.sub.4C particles, then the first layer on the composite material is selected from ZrB.sub.2 and HfB.sub.2, onto which is coated a layer of SiC coated and if the carbon-carbon composite material is inhibited with B.sub.4C particles, then protection can be achieved with a layer of SiC and a layer of either ZrB.sub.2 and HfB.sub.2 in any order.

Ultra-high-speed variable focus optics for novel applications in advanced imaging

NASA Astrophysics Data System (ADS)

Kang, S.; Dotsenko, E.; Amrhein, D.; Theriault, C.; Arnold, C. B.

2018-02-01

With the advancement of ultra-fast manufacturing technologies, high speed imaging with high 3D resolution has become increasingly important. Here we show the use of an ultra-high-speed variable focus optical element, the TAG Lens, to enable new ways to acquire 3D information from an object. The TAG Lens uses sound to adjust the index of refraction profile in a liquid and thereby can achieve focal scanning rates greater than 100 kHz. When combined with a high-speed pulsed LED and a high-speed camera, we can exploit this phenomenon to achieve high-resolution imaging through large depths. By combining the image acquisition with digital image processing, we can extract relevant parameters such as tilt and angle information from objects in the image. Due to the high speeds at which images can be collected and processed, we believe this technique can be used as an efficient method of industrial inspection and metrology for high throughput applications.

NASA / Pratt and Whitney Collaborative Partnership Research in Ultra High Bypass Cycle Propulsion Concepts

NASA Technical Reports Server (NTRS)

Hughes, Chris; Lord, Wed

2008-01-01

Current collaborative research with Pratt & Whitney on Ultra High Bypass Engine Cycle noise, performance and emissions improvements as part of the Subsonic Fixed Wing Project Ultra High Bypass Engine Partnership Element is discussed. The Subsonic Fixed Wing Project goals are reviewed, as well as their relative technology level compared to previous NASA noise program goals. Progress toward achieving the Subsonic Fixed Wing Project goals over the 2008 fiscal year by the UHB Partnership in this area of research are reviewed. The current research activity in Ultra High Bypass Engine Cycle technology, specifically the Pratt & Whitney Geared Turbofan, at NASA and Pratt & Whitney are discussed including the contributions each entity bring toward the research project, and technical plans and objectives. Pratt & Whitney Geared Turbofan current and future technology and business plans are also discussed, including the role the NASA SFW UHB partnership plays toward achieving those goals.

Wakefield Computations for the CLIC PETS using the Parallel Finite Element Time-Domain Code T3P

DOE Office of Scientific and Technical Information (OSTI.GOV)

Candel, A; Kabel, A.; Lee, L.

In recent years, SLAC's Advanced Computations Department (ACD) has developed the high-performance parallel 3D electromagnetic time-domain code, T3P, for simulations of wakefields and transients in complex accelerator structures. T3P is based on advanced higher-order Finite Element methods on unstructured grids with quadratic surface approximation. Optimized for large-scale parallel processing on leadership supercomputing facilities, T3P allows simulations of realistic 3D structures with unprecedented accuracy, aiding the design of the next generation of accelerator facilities. Applications to the Compact Linear Collider (CLIC) Power Extraction and Transfer Structure (PETS) are presented.

Dynamics of electron injection and acceleration driven by laser wakefield in tailored density profiles

DOE PAGES

Lee, Patrick; Maynard, G.; Audet, T. L.; ...

2016-11-16

The dynamics of electron acceleration driven by laser wakefield is studied in detail using the particle-in-cell code WARP with the objective to generate high-quality electron bunches with narrow energy spread and small emittance, relevant for the electron injector of a multistage accelerator. Simulation results, using experimentally achievable parameters, show that electron bunches with an energy spread of ~11% can be obtained by using an ionization-induced injection mechanism in a mm-scale length plasma. By controlling the focusing of a moderate laser power and tailoring the longitudinal plasma density profile, the electron injection beginning and end positions can be adjusted, while themore » electron energy can be finely tuned in the last acceleration section.« less

Electron diffraction using ultrafast electron bunches from a laser-wakefield accelerator at kHz repetition rate

NASA Astrophysics Data System (ADS)

He, Z.-H.; Thomas, A. G. R.; Beaurepaire, B.; Nees, J. A.; Hou, B.; Malka, V.; Krushelnick, K.; Faure, J.

2013-02-01

We show that electron bunches in the 50-100 keV range can be produced from a laser wakefield accelerator using 10 mJ, 35 fs laser pulses operating at 0.5 kHz. It is shown that using a solenoid magnetic lens, the electron bunch distribution can be shaped. The resulting transverse and longitudinal coherence is suitable for producing diffraction images from a polycrystalline 10 nm aluminum foil. The high repetition rate, the stability of the electron source, and the fact that its uncorrelated bunch duration is below 100 fs make this approach promising for the development of sub-100 fs ultrafast electron diffraction experiments.

Advanced optical systems for ultra high energy cosmic rays detection

NASA Astrophysics Data System (ADS)

Gambicorti, L.; Pace, E.; Mazzinghi, P.

2017-11-01

A new advanced optical system is proposed and analysed in this work with the purpose to improve the photons collection efficiency of Multi-AnodePhotoMultipliers (MAPMT) detectors, which will be used to cover large focal surface of instruments dedicated to the Ultra High Energy Cosmic Rays (UHECRs, above 1019eV) and Ultra High Energy Neutrino (UHEN) detection. The employment of the advanced optical system allows to focus all photons inside the sensitive area of detectors and to improve the signal-to-noise ratios in the wavelength range of interest (300-400nm), thus coupling imaging and filtering capability. Filter is realised with a multilayer coating to reach high transparency in UV range and with a sharp cut-off outside. In this work the applications on different series of PMTs have been studied and results of simulations are shown. First prototypes have been realised. Finally, this paper proposes another class of adapters to be optically coupled on each pixel of MAPMT detector selected, consisting of non-imaging concentrators as Winston cones.

Examining the association between social cognition and functioning in individuals at ultra-high risk for psychosis.

PubMed

Cotter, Jack; Bartholomeusz, Cali; Papas, Alicia; Allott, Kelly; Nelson, Barnaby; Yung, Alison R; Thompson, Andrew

2017-01-01

Social and role functioning are compromised for the majority of individuals at ultra-high risk of psychosis, and it is important to identify factors that contribute to this functional decline. This study aimed to investigate social cognitive abilities, which have previously been linked to functioning in schizophrenia, as potential factors that impact social, role and global functioning in ultra-high risk patients. A total of 30 ultra-high risk patients were recruited from an established at-risk clinical service in Melbourne, Australia, and completed a battery of social cognitive, neurocognitive, clinical and functioning measures. We examined the relationships between all four core domains of social cognition (emotion recognition, theory of mind, social perception and attributional style), neurocognitive, clinical and demographic variables with three measures of functioning (the Global Functioning Social and Role scales and the Social and Occupational Functioning Assessment Scale) using correlational and multiple regression analyses. Performance on a visual theory of mind task (visual jokes task) was significantly correlated with both concurrent role ( r = 0.425, p = 0.019) and global functioning ( r = 0.540, p = 0.002). In multivariate analyses, it also accounted for unique variance in global, but not role functioning after adjusting for negative symptoms and stress. Social functioning was not associated with performance on any of the social cognition tasks. Among specific social cognitive abilities, only a test of theory of mind was associated with functioning in our ultra-high risk sample. Further longitudinal research is needed to examine the impact of social cognitive deficits on long-term functional outcome in the ultra-high risk group. Identifying social cognitive abilities that significantly impact functioning is important to inform the development of targeted intervention programmes for ultra-high risk individuals.

Temporal profile measurements of relativistic electron bunch based on wakefield generation

DOE PAGES

Bettoni, S.; Craievich, P.; Lutman, A. A.; ...

2016-02-25

A complete characterization of the time-resolved longitudinal beam phase space is important to optimize the final performances of an accelerator, and in particular this is crucial for Free Electron Laser (FEL) facilities. In this study we propose a novel method to characterize the profile of a relativistic electron bunch by passively streaking the beam using its self-interaction with the transverse wakefield excited by the bunch itself passing off-axis through a dielectric-lined or a corrugated waveguide. Results of a proof-of-principle experiment at the SwissFEL Injector Test Facility are discussed.

High-performance radial AMTEC cell design for ultra-high-power solar AMTEC systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hendricks, T.J.; Huang, C.

1999-07-01

Alkali Metal Thermal to Electric Conversion (AMTEC) technology is rapidly maturing for potential application in ultra-high-power solar AMTEC systems required by potential future US Air Force (USAF) spacecraft missions in medium-earth and geosynchronous orbits (MEO and GEO). Solar thermal AMTEC power systems potentially have several important advantages over current solar photovoltaic power systems in ultra-high-power spacecraft applications for USAF MEO and GEO missions. This work presents key aspects of radial AMTEC cell design to achieve high cell performance in solar AMTEC systems delivering larger than 50 kW(e) to support high power USAF missions. These missions typically require AMTEC cell conversionmore » efficiency larger than 25%. A sophisticated design parameter methodology is described and demonstrated which establishes optimum design parameters in any radial cell design to satisfy high-power mission requirements. Specific relationships, which are distinct functions of cell temperatures and pressures, define critical dependencies between key cell design parameters, particularly the impact of parasitic thermal losses on Beta Alumina Solid Electrolyte (BASE) area requirements, voltage, number of BASE tubes, and system power production for both maximum power-per-BASE-area and optimum efficiency conditions. Finally, some high-level system tradeoffs are demonstrated using the design parameter methodology to establish high-power radial cell design requirements and philosophy. The discussion highlights how to incorporate this methodology with sophisticated SINDA/FLUINT AMTEC cell modeling capabilities to determine optimum radial AMTEC cell designs.« less

Development of Non-Proprietary Ultra-High Performance Concrete : Project Summary Report

DOT National Transportation Integrated Search

2017-12-01

Ultra-high performance concrete (UHPC) has mechanical and durability properties that far exceed those of conventional concrete. Thus, elements made with UHPC can be thinner/lighter than elements made with conventional concrete. The enhanced durabilit...

Device for wavefront correction in an ultra high power laser

DOEpatents

Ault, Earl R.; Comaskey, Brian J.; Kuklo, Thomas C.

2002-01-01

A system for wavefront correction in an ultra high power laser. As the laser medium flows past the optical excitation source and the fluid warms its index of refraction changes creating an optical wedge. A system is provided for correcting the thermally induced optical phase errors.

High-power ultra-broadband frequency comb from ultraviolet to infrared by high-power fiber amplifiers.

PubMed

Yang, Kangwen; Li, Wenxue; Yan, Ming; Shen, Xuling; Zhao, Jian; Zeng, Heping

2012-06-04

A high-power ultra-broadband frequency comb covering the spectral range from ultraviolet to infrared was generated directly by nonlinear frequency conversion of a multi-stage high-power fiber comb amplifier. The 1030-nm infrared spectral fraction of a broadband Ti:sapphire femtosecond frequency comb was power-scaled up to 100 W average power by using a large-mode-area fiber chirped-pulse amplifier. We obtained a frequency-doubled green comb at 515 nm and frequency-quadrupled ultraviolet pulses at 258 nm with the average power of 12.8 and 1.62 W under the input infrared power of 42.2 W, respectively. The carrier envelope phase stabilization was accomplished with an ultra-narrow line-width of 1.86 mHz and a quite low accumulated phase jitter of 0.41 rad, corresponding to a timing jitter of 143 as.

High-gradient SRF R&D for ILC at Jefferson Lab

DOE Office of Scientific and Technical Information (OSTI.GOV)

Geng, Rongli; Crawford, Anthony; Ciovati, Gianluigi

2008-10-01

Jefferson Lab plays an active role in high-gradient SRF R&D in the frame work of the internationally coordinated ILC S0 program. The S0 aim is to push the yield at 35 MV/m in 9-cell cavities. So far, twelve cavities have been electropolishing (EP) processed and RF tested by using the state-of-the-art recipes at JLab, in close collaboration with FNAL and KEK. Seven of them reached a best gradient of over 31.5 MV/m. Understanding gradient limiting mechanisms in real 9-cell cavities is an important component of our studies. Thermometry and high-resolution optical inspection are used to locate and understand the sourcemore » of gradient limits. Experimenting with selective cavities is still a necessary method for process optimization. One example is the first demonstration of 35 MV/m without detectable Bremsstrahlung X-ray after a light EP is applied to a previously heavy BCP etched 7-cell cavity. Some new understanding has been gained with regard to quench behaviors, field emission behaviors as« less

Ultra-high density aligned Carbon-nanotube with controled nano-morphology for supercapacitors

NASA Astrophysics Data System (ADS)

Ghaffari, Mehdi; Zhao, Ran; Liu, Yang; Zhou, Yue; Cheng, Jiping; Guzman de Villoria, Roberto; Wardle, B. L.; Zhang, Q. M.

2012-02-01

Recent advances in fabricating controlled-morphology vertically aligned carbon nanotubes (VA-CNTs) with ultrahigh volume fractioncreate unique opportunities for developing unconventional supercapacitors with ultra-high energy density, power density, and long charge/discharge cycle life.Continuous paths through inter-VA-CNT channels allow fast ion transport, and high electrical conduction of the aligned CNTs in the composite electrodes lead to fast discharge speed. We investigate the charge-discharge characteristics of VA-CNTs with >20 vol% of CNT and ionic liquids as electrolytes. By employing both the electric and electromechanical spectroscopes, as well as nanostructured materials characterization, the ion transport and storage behaviors in porous electrodes are studied. The results suggest pathways for optimizing the electrode morphology in supercapacitorsusing ultra-high volume fraction VA-CNTs to further enhance performance.

Development of a Family of Ultra-High Performance Concrete Pi-Girders

DOT National Transportation Integrated Search

2014-01-01

Ultra-high performance concrete (UHPC) is an advanced cementitious composite material, which tends to exhibit superior properties such as exceptional durability, increased strength, and long-term stability. (See references 1-4.) The use of existing s...

Ultra-high performance concrete for Michigan bridges, material performance : phase I.

DOT National Transportation Integrated Search

2008-10-13

One of the latest advancements in concrete technology is Ultra-High Performance Concrete (UHPC). UHPC is : defined as concretes attaining compressive strengths exceeding 25 ksi (175 MPa). It is a fiber-reinforced, denselypacked : concrete material wh...

High gradient RF test results of S-band and C-band cavities for medical linear accelerators

NASA Astrophysics Data System (ADS)

Degiovanni, A.; Bonomi, R.; Garlasché, M.; Verdú-Andrés, S.; Wegner, R.; Amaldi, U.

2018-05-01

TERA Foundation has proposed and designed hadrontherapy facilities based on novel linacs, i.e. high gradient linacs which accelerate either protons or light ions. The overall length of the linac, and therefore its cost, is almost inversely proportional to the average accelerating gradient. With the scope of studying the limiting factors for high gradient operation and to optimize the linac design, TERA, in collaboration with the CLIC Structure Development Group, has conducted a series of high gradient experiments. The main goals were to study the high gradient behavior and to evaluate the maximum gradient reached in 3 and 5.7 GHz structures to direct the design of medical accelerators based on high gradient linacs. This paper summarizes the results of the high power tests of 3.0 and 5.7 GHz single-cell cavities.

Integrated computational study of ultra-high heat flux cooling using cryogenic micro-solid nitrogen spray

NASA Astrophysics Data System (ADS)

Ishimoto, Jun; Oh, U.; Tan, Daisuke

2012-10-01

A new type of ultra-high heat flux cooling system using the atomized spray of cryogenic micro-solid nitrogen (SN2) particles produced by a superadiabatic two-fluid nozzle was developed and numerically investigated for application to next generation super computer processor thermal management. The fundamental characteristics of heat transfer and cooling performance of micro-solid nitrogen particulate spray impinging on a heated substrate were numerically investigated and experimentally measured by a new type of integrated computational-experimental technique. The employed Computational Fluid Dynamics (CFD) analysis based on the Euler-Lagrange model is focused on the cryogenic spray behavior of atomized particulate micro-solid nitrogen and also on its ultra-high heat flux cooling characteristics. Based on the numerically predicted performance, a new type of cryogenic spray cooling technique for application to a ultra-high heat power density device was developed. In the present integrated computation, it is clarified that the cryogenic micro-solid spray cooling characteristics are affected by several factors of the heat transfer process of micro-solid spray which impinges on heated surface as well as by atomization behavior of micro-solid particles. When micro-SN2 spraying cooling was used, an ultra-high cooling heat flux level was achieved during operation, a better cooling performance than that with liquid nitrogen (LN2) spray cooling. As micro-SN2 cooling has the advantage of direct latent heat transport which avoids the film boiling state, the ultra-short time scale heat transfer in a thin boundary layer is more possible than in LN2 spray. The present numerical prediction of the micro-SN2 spray cooling heat flux profile can reasonably reproduce the measurement results of cooling wall heat flux profiles. The application of micro-solid spray as a refrigerant for next generation computer processors is anticipated, and its ultra-high heat flux technology is expected

Caveats when Analyzing Ultra-high Molar Mass Polymers by SEC

USDA-ARS?s Scientific Manuscript database

The analysis of ultra-high molar mass (M > 1 million g/mol) polymers via size-exclusion chromatography (SEC) presents a number of non-trivial challenges. Dissolution and full solvation may take days, as is the case for cellulose dissolution in non-complexing non degrading solvents; very low concent...

Study of Volumetrically Heated Ultra-High Energy Density Plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rocca, Jorge J.

2016-10-27

Heating dense matter to millions of degrees is important for applications, but requires complex and expensive methods. The major goal of the project was to demonstrate using a compact laser the creation of a new ultra-high energy density plasma regime characterized by simultaneous extremely high temperature and high density, and to study it combining experimental measurements and advanced simulations. We have demonstrated that trapping of intense femtosecond laser pulses deep within ordered nanowire arrays can heat near solid density matter into a new ultra hot plasma regime. Extreme electron densities, and temperatures of several tens of million degrees were achievedmore » using laser pulses of only 0.5 J energy from a compact laser. Our x-ray spectra and simulations showed that extremely highly ionized plasma volumes several micrometers in depth are generated by irradiation of gold and Nickel nanowire arrays with femtosecond laser pulses of relativistic intensities. We obtained extraordinarily high degrees of ionization (e.g. we peeled 52 electrons from gold atoms, and up to 26 electrons from nickel atoms). In the process we generated Gigabar pressures only exceeded in the central hot spot of highly compressed thermonuclear fusion plasmas.. The plasma created after the dissolved wires expand, collide, and thermalize, is computed to have a thermal energy density of 0.3 GJ cm -3 and a pressure of 1-2 Gigabar. These are pressures only exceeded in highly compressed thermonuclear fusion plasmas. Scaling these results to higher laser intensities promises to create plasmas with temperatures and pressures exceeding those in the center of the sun.« less

Differential renal effects of candesartan at high and ultra-high doses in diabetic mice–potential role of the ACE2/AT2R/Mas axis

PubMed Central

Callera, Glaucia E.; Antunes, Tayze T.; Correa, Jose W.; Moorman, Danielle; Gutsol, Alexey; He, Ying; Cat, Aurelie Nguyen Dinh; Briones, Ana M.; Montezano, Augusto C.; Burns, Kevin D.; Touyz, Rhian M.

2016-01-01

High doses of Ang II receptor (AT1R) blockers (ARBs) are renoprotective in diabetes. Underlying mechanisms remain unclear. We evaluated whether high/ultra-high doses of candesartan (ARB) up-regulate angiotensin-converting enzyme 2 (ACE2)/Ang II type 2 receptor (AT2R)/Mas receptor [protective axis of the of the renin–angiotensin system (RAS)] in diabetic mice. Systolic blood pressure (SBP), albuminuria and expression/activity of RAS components were assessed in diabetic db/db and control db/+ mice treated with increasing candesartan doses (intermediate, 1 mg/kg/d; high, 5 mg/kg/d; ultra-high, 25 and 75 mg/kg/d; 4 weeks). Lower doses candesartan did not influence SBP, but ultra-high doses reduced SBP in both groups. Plasma glucose and albuminuria were increased in db/db compared with db/+ mice. In diabetic mice treated with intermediate dose candesartan, renal tubular damage and albuminuria were ameliorated and expression of ACE2, AT2R and Mas and activity of ACE2 were increased, effects associated with reduced ERK1/2 phosphorylation, decreased fibrosis and renal protection. Ultra-high doses did not influence the ACE2/AT2R/Mas axis and promoted renal injury with increased renal ERK1/2 activation and exaggerated fibronectin expression in db/db mice. Our study demonstrates dose-related effects of candesartan in diabetic nephropathy: intermediate–high dose candesartan is renoprotective, whereas ultra-high dose candesartan induces renal damage. Molecular processes associated with these effects involve differential modulation of the ACE2/AT2R/Mas axis: intermediate–high dose candesartan up-regulating RAS protective components and attenuating pro-fibrotic processes, and ultra-high doses having opposite effects. These findings suggest novel mechanisms through the protective RAS axis, whereby candesartan may ameliorate diabetic nephropathy. Our findings also highlight potential injurious renal effects of ultra-high dose candesartan in diabetes. PMID:27612496

Determination of boundaries between ranges of high and low gradient of beam profile.

PubMed

Wendykier, Jacek; Bieniasiewicz, Marcin; Grządziel, Aleksandra; Jedynak, Tadeusz; Kośniewski, Wiktor; Reudelsdorf, Marta; Wendykier, Piotr

2016-01-01

This work addresses the problem of treatment planning system commissioning by introducing a new method of determination of boundaries between high and low gradient in beam profile. The commissioning of a treatment planning system is a very important task in the radiation therapy. One of the main goals of this task is to compare two field profiles: measured and calculated. Applying points of 80% and 120% of nominal field size can lead to the incorrect determination of boundaries, especially for small field sizes. The method that is based on the beam profile gradient allows for proper assignment of boundaries between high and low gradient regions even for small fields. TRS 430 recommendations for commissioning were used. The described method allows a separation between high and low gradient, because it directly uses the value of the gradient of a profile. For small fields, the boundaries determined by the new method allow a commissioning of a treatment planning system according to the TRS 430, while the point of 80% of nominal field size is already in the high gradient region. The method of determining the boundaries by using the beam profile gradient can be extremely helpful during the commissioning of the treatment planning system for Intensity Modulated Radiation Therapy or for other techniques which require very small field sizes.

High-gradient permanent magnet apparatus and its use in particle collection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, Mengdawn; Ludtka, Gerard Michael; Avens, Larry R.

A high-gradient permanent magnet apparatus for capturing paramagnetic particles, the apparatus comprising: (i) at least two permanent magnets positioned with like poles facing each other; (ii) a ferromagnetic spacer separating the like poles; and (iii) a magnetizable porous filling material in close proximity to the at least two permanent magnets. Also described is a method for capturing paramagnetic particles in which a gas or liquid sample containing the paramagnetic particles is contacted with the high-gradient permanent magnet apparatus described above; wherein, during the contacting step, the gas or liquid sample contacts the magnetizable porous filling material of the high-gradient permanentmore » magnet apparatus, and at least a portion of the paramagnetic particles in the gas or liquid sample is captured on the magnetizable porous filling material.« less

High and ultra-high resolution metabolite mapping of the human brain using 1H FID MRSI at 9.4T.

PubMed

Nassirpour, Sahar; Chang, Paul; Henning, Anke

2018-03-01

Magnetic resonance spectroscopic imaging (MRSI) is a promising technique for mapping the spatial distribution of multiple metabolites in the human brain. These metabolite maps can be used as a diagnostic tool to gain insight into several biochemical processes and diseases in the brain. In comparison to lower field strengths, MRSI at ultra-high field strengths benefits from a higher signal to noise ratio (SNR) as well as higher chemical shift dispersion, and hence spectral resolution. This study combines the benefits of an ultra-high field magnet with the advantages of an ultra-short TE and TR single-slice FID-MRSI sequence (such as negligible J-evolution and loss of SNR due to T 2 relaxation effects) and presents the first metabolite maps acquired at 9.4T in the healthy human brain at both high (voxel size of 97.6µL) and ultra-high (voxel size of 24.4µL) spatial resolutions in a scan time of 11 and 46min respectively. In comparison to lower field strengths, more anatomically-detailed maps with higher SNR from a larger number of metabolites are shown. A total of 12 metabolites including glutamate (Glu), glutamine (Gln), N-acetyl-aspartyl-glutamate (NAAG), Gamma-aminobutyric acid (GABA) and glutathione (GSH) are reliably mapped. Comprehensive description of the methodology behind these maps is provided. Copyright © 2016 Elsevier Inc. All rights reserved.

Ultra-High Temperature Materials Characterization for Propulsion Applications

NASA Technical Reports Server (NTRS)

Rogers, Jan; Hyers, Robert

2007-01-01

Propulsion system efficiency increases as operating temperatures are increased. Some very high-temperature materials are being developed, including refractory metal alloys, carbides, borides, and silicides. System design requires data for materials properties at operating temperatures. Materials property data are not available for many materials of interest at the desired operating temperatures (up to approx. 3000 K). The objective of this work is to provide important physical property data at ultra-high temperatures. The MSFC Electrostatic levitation (ESL) facility can provide measurements of thermophysical properties which include: creep strength, density and thermal expansion for materials being developed for propulsion applications. The ESL facility uses electrostatic fields to position samples between electrodes during processing and characterization studies. Because the samples float between the electrodes during studies, they are free from any contact with a container or test apparatus. This provides a high purity environment for the study of high-temperature, reactive materials. ESL can be used to process a wide variety of materials including metals, alloys, ceramics, glasses and semiconductors. The MSFC ESL has provided non-contact measurements of properties of materials up to 3400 C. Density and thermal expansion are measured by analyzing digital images of the sample at different temperatures. Our novel, non-contact method for measuring creep uses rapid rotation to deform the sample. Digital images of the deformed samples are analyzed to obtain the creep properties, which match those obtained using ASTM Standard E-139 for Nb at 1985 C. Data from selected ESL-based characterization studies will be presented. The ESL technique could support numerous propulsion technologies by advancing the knowledge base and the technology readiness level for ultra-high temperature materials. Applications include non-eroding nozzle materials and lightweight, high

Ultra high spatial and temporal resolution breast imaging at 7T.

PubMed

van de Bank, B L; Voogt, I J; Italiaander, M; Stehouwer, B L; Boer, V O; Luijten, P R; Klomp, D W J

2013-04-01

There is a need to obtain higher specificity in the detection of breast lesions using MRI. To address this need, Dynamic Contrast-Enhanced (DCE) MRI has been combined with other structural and functional MRI techniques. Unfortunately, owing to time constraints structural images at ultra-high spatial resolution can generally not be obtained during contrast uptake, whereas the relatively low spatial resolution of functional imaging (e.g. diffusion and perfusion) limits the detection of small lesions. To be able to increase spatial as well as temporal resolution simultaneously, the sensitivity of MR detection needs to increase as well as the ability to effectively accelerate the acquisition. The required gain in signal-to-noise ratio (SNR) can be obtained at 7T, whereas acceleration can be obtained with high-density receiver coil arrays. In this case, morphological imaging can be merged with DCE-MRI, and other functional techniques can be obtained at higher spatial resolution, and with less distortion [e.g. Diffusion Weighted Imaging (DWI)]. To test the feasibility of this concept, we developed a unilateral breast coil for 7T. It comprises a volume optimized dual-channel transmit coil combined with a 30-channel receive array coil. The high density of small coil elements enabled efficient acceleration in any direction to acquire ultra high spatial resolution MRI of close to 0.6 mm isotropic detail within a temporal resolution of 69 s, high spatial resolution MRI of 1.5 mm isotropic within an ultra high temporal resolution of 6.7 s and low distortion DWI at 7T, all validated in phantoms, healthy volunteers and a patient with a lesion in the right breast classified as Breast Imaging Reporting and Data System (BI-RADS) IV. Copyright © 2012 John Wiley & Sons, Ltd.

High gradient RF test results of S-band and C-band cavities for medical linear accelerators

DOE PAGES

Degiovanni, A.; Bonomi, R.; Garlasche, M.; ...

2018-02-09

TERA Foundation has proposed and designed hadrontherapy facilities based on novel linacs, i.e. high gradient linacs which accelerate either protons or light ions. The overall length of the linac, and therefore its cost, is almost inversely proportional to the average accelerating gradient. With the scope of studying the limiting factors for high gradient operation and to optimize the linac design, TERA, in collaboration with the CLIC Structure Development Group, has conducted a series of high gradient experiments. The main goals were to study the high gradient behavior and to evaluate the maximum gradient reached in 3 and 5.7 GHz structuresmore » to direct the design of medical accelerators based on high gradient linacs. Lastly, this paper summarizes the results of the high power tests of 3.0 and 5.7 GHz single-cell cavities.« less

High gradient RF test results of S-band and C-band cavities for medical linear accelerators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Degiovanni, A.; Bonomi, R.; Garlasche, M.

TERA Foundation has proposed and designed hadrontherapy facilities based on novel linacs, i.e. high gradient linacs which accelerate either protons or light ions. The overall length of the linac, and therefore its cost, is almost inversely proportional to the average accelerating gradient. With the scope of studying the limiting factors for high gradient operation and to optimize the linac design, TERA, in collaboration with the CLIC Structure Development Group, has conducted a series of high gradient experiments. The main goals were to study the high gradient behavior and to evaluate the maximum gradient reached in 3 and 5.7 GHz structuresmore » to direct the design of medical accelerators based on high gradient linacs. Lastly, this paper summarizes the results of the high power tests of 3.0 and 5.7 GHz single-cell cavities.« less

Structural Analysis of Titan's Tholins by Ultra-High Resolution Mass Spectrometry

NASA Astrophysics Data System (ADS)

Vuitton, V.; Frisari, M.; Thissen, R.; Dutuit, O.; Bonnet, J.-Y.; Quirico, E.; Sciamma O'Brien, E.; Szopa, C.; Carrasco, N.; Somogyi, A.; Smith, M.; Hörst, S. M.; Yelle, R.

2010-04-01

We propose here a systematic ultra-high resolution mass spectrometry and MS/MS study in order to provide a more coherent and complete characterization of the structure of the molecules making up the soluble fraction of the Titan tholins.

Bremsstrahlung hard x-ray source driven by an electron beam from a self-modulated laser wakefield accelerator

NASA Astrophysics Data System (ADS)

Lemos, N.; Albert, F.; Shaw, J. L.; Papp, D.; Polanek, R.; King, P.; Milder, A. L.; Marsh, K. A.; Pak, A.; Pollock, B. B.; Hegelich, B. M.; Moody, J. D.; Park, J.; Tommasini, R.; Williams, G. J.; Chen, Hui; Joshi, C.

2018-05-01

An x-ray source generated by an electron beam produced using a Self-Modulated Laser Wakefield Accelerator (SM-LWFA) is explored for use in high energy density science facilities. By colliding the electron beam, with a maximum energy of 380 MeV, total charge of >10 nC and a divergence of 64 × 100 mrad, from a SM-LWFA driven by a 1 ps 120 J laser, into a high-Z foil, an x/gamma-ray source was generated. A broadband bremsstrahlung energy spectrum with temperatures ranging from 0.8 to 2 MeV was measured with an almost 2 orders of magnitude flux increase when compared with other schemes using LWFA. GEANT4 simulations were done to calculate the source size and divergence.

The Bendability of Ultra High strength Steels

NASA Astrophysics Data System (ADS)

Hazra, S. K.; Efthymiadis, P.; Alamoudi, A.; Kumar, R. L. V.; Shollock, B.; Dashwood, R.

2016-08-01

Automotive manufacturers have been reducing the weight of their vehicles to meet increasingly stringent environmental legislation that reflects public demand. A strategy is to use higher strength materials for parts with reduced cross-sections. However, such materials are less formable than traditional grades. The frequent result is increased processing and piece costs. 3D roll forming is a novel and flexible process: it is estimated that a quarter of the structure of a vehicle can be made with a single set of tooling. Unlike stamping, this process requires material with low work hardening rates. In this paper, we present results of ultra high strength steels that have low elongation in a tension but display high formability in bending through the suppression of the necking response.

Development of Non-Proprietary Ultra-High Performance Concrete : Research Topic Statement

DOT National Transportation Integrated Search

2014-05-29

Ultra-high performance concrete became commercially available in the U.S. in 2000. Since then, UHPC has been actively promoted by the Federal Highway Administration. UHPC has mostly been used in the U.S. for field-cast connections of prefabricated br...

Ionic liquid gating on atomic layer deposition passivated GaN: Ultra-high electron density induced high drain current and low contact resistance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Hong; Du, Yuchen; Ye, Peide D., E-mail: yep@purdue.edu

2016-05-16

Herein, we report on achieving ultra-high electron density (exceeding 10{sup 14 }cm{sup −2}) in a GaN bulk material device by ionic liquid gating, through the application of atomic layer deposition (ALD) of Al{sub 2}O{sub 3} to passivate the GaN surface. Output characteristics demonstrate a maximum drain current of 1.47 A/mm, the highest reported among all bulk GaN field-effect transistors, with an on/off ratio of 10{sup 5} at room temperature. An ultra-high electron density exceeding 10{sup 14 }cm{sup −2} accumulated at the surface is confirmed via Hall-effect measurement and transfer length measurement. In addition to the ultra-high electron density, we also observe a reductionmore » of the contact resistance due to the narrowing of the Schottky barrier width on the contacts. Taking advantage of the ALD surface passivation and ionic liquid gating technique, this work provides a route to study the field-effect and carrier transport properties of conventional semiconductors in unprecedented ultra-high charge density regions.« less

A swimming pool array for ultra high energy showers

NASA Astrophysics Data System (ADS)

Yodh, Gaurang B.; Shoup, Anthony; Barwick, Steve; Goodman, Jordan A.

1992-11-01

A very preliminary design concept for an array using water Cherenkov counters, built out of commercially available backyard swimming pools, to sample the electromagnetic and muonic components of ultra high energy showers at large lateral distances is presented. The expected performance of the pools is estimated using the observed lateral distributions by scintillator and water Cherenkov arrays at energies above 1019 eV and simulations.

Gradient Magnitude Similarity Deviation: A Highly Efficient Perceptual Image Quality Index.

PubMed

Xue, Wufeng; Zhang, Lei; Mou, Xuanqin; Bovik, Alan C

2014-02-01

It is an important task to faithfully evaluate the perceptual quality of output images in many applications, such as image compression, image restoration, and multimedia streaming. A good image quality assessment (IQA) model should not only deliver high quality prediction accuracy, but also be computationally efficient. The efficiency of IQA metrics is becoming particularly important due to the increasing proliferation of high-volume visual data in high-speed networks. We present a new effective and efficient IQA model, called gradient magnitude similarity deviation (GMSD). The image gradients are sensitive to image distortions, while different local structures in a distorted image suffer different degrees of degradations. This motivates us to explore the use of global variation of gradient based local quality map for overall image quality prediction. We find that the pixel-wise gradient magnitude similarity (GMS) between the reference and distorted images combined with a novel pooling strategy-the standard deviation of the GMS map-can predict accurately perceptual image quality. The resulting GMSD algorithm is much faster than most state-of-the-art IQA methods, and delivers highly competitive prediction accuracy. MATLAB source code of GMSD can be downloaded at http://www4.comp.polyu.edu.hk/~cslzhang/IQA/GMSD/GMSD.htm.

Simple, rapid, and environmentally friendly method for the separation of isoflavones using ultra-high performance supercritical fluid chromatography.

PubMed

Wu, Wenjie; Zhang, Yuan; Wu, Hanqiu; Zhou, Weie; Cheng, Yan; Li, Hongna; Zhang, Chuanbin; Li, Lulu; Huang, Ying; Zhang, Feng

2017-07-01

Isoflavones are natural substances that exhibit hormone-like pharmacological activities. The separation of isoflavones remains an analytical challenge because of their similar structures. We show that ultra-high performance supercritical fluid chromatography can be an appropriate tool to achieve the fast separation of 12 common dietary isoflavones. Among the five tested columns the Torus DEA column was found to be the most effective column for the separation of these isoflavones. The impact of individual parameters on the retention time and separation factor was evaluated. These parameters were optimized to develop a simple, rapid, and green method for the separation of the 12 target analytes. It only took 12.91 min using gradient elution with methanol as an organic modifier and formic acid as an additive. These isoflavones were determined with limit of quantitation ranging from 0.10 to 0.50 μg/mL, which was sufficient for reliable determination of various matrixes. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Generation of a large volume of clinically relevant nanometre-sized ultra-high-molecular-weight polyethylene wear particles for cell culture studies

PubMed Central

Ingham, Eileen; Fisher, John; Tipper, Joanne L

2014-01-01

It has recently been shown that the wear of ultra-high-molecular-weight polyethylene in hip and knee prostheses leads to the generation of nanometre-sized particles, in addition to micron-sized particles. The biological activity of nanometre-sized ultra-high-molecular-weight polyethylene wear particles has not, however, previously been studied due to difficulties in generating sufficient volumes of nanometre-sized ultra-high-molecular-weight polyethylene wear particles suitable for cell culture studies. In this study, wear simulation methods were investigated to generate a large volume of endotoxin-free clinically relevant nanometre-sized ultra-high-molecular-weight polyethylene wear particles. Both single-station and six-station multidirectional pin-on-plate wear simulators were used to generate ultra-high-molecular-weight polyethylene wear particles under sterile and non-sterile conditions. Microbial contamination and endotoxin levels in the lubricants were determined. The results indicated that microbial contamination was absent and endotoxin levels were low and within acceptable limits for the pharmaceutical industry, when a six-station pin-on-plate wear simulator was used to generate ultra-high-molecular-weight polyethylene wear particles in a non-sterile environment. Different pore-sized polycarbonate filters were investigated to isolate nanometre-sized ultra-high-molecular-weight polyethylene wear particles from the wear test lubricants. The use of the filter sequence of 10, 1, 0.1, 0.1 and 0.015 µm pore sizes allowed successful isolation of ultra-high-molecular-weight polyethylene wear particles with a size range of < 100 nm, which was suitable for cell culture studies. PMID:24658586

Generation of a large volume of clinically relevant nanometre-sized ultra-high-molecular-weight polyethylene wear particles for cell culture studies.

PubMed

Liu, Aiqin; Ingham, Eileen; Fisher, John; Tipper, Joanne L

2014-04-01

It has recently been shown that the wear of ultra-high-molecular-weight polyethylene in hip and knee prostheses leads to the generation of nanometre-sized particles, in addition to micron-sized particles. The biological activity of nanometre-sized ultra-high-molecular-weight polyethylene wear particles has not, however, previously been studied due to difficulties in generating sufficient volumes of nanometre-sized ultra-high-molecular-weight polyethylene wear particles suitable for cell culture studies. In this study, wear simulation methods were investigated to generate a large volume of endotoxin-free clinically relevant nanometre-sized ultra-high-molecular-weight polyethylene wear particles. Both single-station and six-station multidirectional pin-on-plate wear simulators were used to generate ultra-high-molecular-weight polyethylene wear particles under sterile and non-sterile conditions. Microbial contamination and endotoxin levels in the lubricants were determined. The results indicated that microbial contamination was absent and endotoxin levels were low and within acceptable limits for the pharmaceutical industry, when a six-station pin-on-plate wear simulator was used to generate ultra-high-molecular-weight polyethylene wear particles in a non-sterile environment. Different pore-sized polycarbonate filters were investigated to isolate nanometre-sized ultra-high-molecular-weight polyethylene wear particles from the wear test lubricants. The use of the filter sequence of 10, 1, 0.1, 0.1 and 0.015 µm pore sizes allowed successful isolation of ultra-high-molecular-weight polyethylene wear particles with a size range of < 100 nm, which was suitable for cell culture studies.

SMUVS: Spitzer Matching survey of the UltraVISTA ultra-deep Stripes

NASA Astrophysics Data System (ADS)

Caputi, Karina; Ashby, Matthew; Fazio, Giovanni; Huang, Jiasheng; Dunlop, James; Franx, Marijn; Le Fevre, Olivier; Fynbo, Johan; McCracken, Henry; Milvang-Jensen, Bo; Muzzin, Adam; Ilbert, Olivier; Somerville, Rachel; Wechsler, Risa; Behroozi, Peter; Lu, Yu

2014-12-01

We request 2026.5 hours to homogenize the matching ultra-deep IRAC data of the UltraVISTA ultra-deep stripes, producing a final area of ~0.6 square degrees with the deepest near- and mid-IR coverage existing in any such large area of the sky (H, Ks, [3.6], [4.5] ~ 25.3-26.1 AB mag; 5 sigma). The UltraVISTA ultra-deep stripes are contained within the larger COSMOS field, which has a rich collection of multi-wavelength, ancillary data, making it ideal to study different aspects of galaxy evolution with high statistical significance and excellent redshift accuracy. The UltraVISTA ultra-deep stripes are the region of the COSMOS field where these studies can be pushed to the highest redshifts, but securely identifying high-z galaxies, and determining their stellar masses, will only be possible if ultra-deep mid-IR data are available. Our IRAC observations will allow us to: 1) extend the galaxy stellar mass function at redshifts z=3 to z=5 to the intermediate mass regime (M~5x10^9-10^10 Msun), which is critical to constrain galaxy formation models; 2) gain a factor of six in the area where it is possible to effectively search for z>=6 galaxies and study their properties; 3) measure, for the first time, the large-scale structure traced by an unbiased galaxy sample at z=5 to z=7, and make the link to their host dark matter haloes. This cannot be done in any other field of the sky, as the UltraVISTA ultra-deep stripes form a quasi-contiguous, regular-shape field, which has a unique combination of large area and photometric depth. 4) provide a unique resource for the selection of secure z>5 targets for JWST and ALMA follow up. Our observations will have an enormous legacy value which amply justifies this new observing-time investment in the COSMOS field. Spitzer cannot miss this unique opportunity to open up a large 0.6 square-degree window to the early Universe.

Case study: dairies utilizing ultra-high stock density grazing in the Northeast

USDA-ARS?s Scientific Manuscript database

Ultra-high stock density (UHSD) grazing has gained interest in the forage industry. However, little credible research exists to support anecdotal claims that forage and soil improvement occur through trampling high proportions (75+%) of mature forage into the soil by grazing dense groups of cattle o...

Fast log P determination by ultra-high-pressure liquid chromatography coupled with UV and mass spectrometry detections.

PubMed

Henchoz, Yveline; Guillarme, Davy; Martel, Sophie; Rudaz, Serge; Veuthey, Jean-Luc; Carrupt, Pierre-Alain

2009-08-01

Ultra-high-pressure liquid chromatography (UHPLC) systems able to work with columns packed with sub-2 microm particles offer very fast methods to determine the lipophilicity of new chemical entities. The careful development of the most suitable experimental conditions presented here will help medicinal chemists for high-throughput screening (HTS) log P(oct) measurements. The approach was optimized using a well-balanced set of 38 model compounds and a series of 28 basic compounds such as beta-blockers, local anesthetics, piperazines, clonidine, and derivatives. Different organic modifiers and hybrid stationary phases packed with 1.7-microm particles were evaluated in isocratic as well as gradient modes, and the advantages and limitations of tested conditions pointed out. The UHPLC approach offered a significant enhancement over the classical HPLC methods, by a factor 50 in the lipophilicity determination throughput. The hyphenation of UHPLC with MS detection allowed a further increase in the throughput. Data and results reported herein prove that the UHPLC-MS method can represent a progress in the HTS-measurement of lipophilicity due to its speed (at least a factor of 500 with respect to HPLC approaches) and to an extended field of application.

Ultra-flexible nanocarriers for enhanced topical delivery of a highly lipophilic antioxidative molecule for skin cancer chemoprevention.

PubMed

Boakye, Cedar H A; Patel, Ketan; Doddapaneni, Ravi; Bagde, Arvind; Behl, Gautam; Chowdhury, Nusrat; Safe, Stephen; Singh, Mandip

2016-07-01

In this study, we developed cationic ultra-flexible nanocarriers (UltraFLEX-Nano) to surmount the skin barrier structure and to potentiate the topical delivery of a highly lipophilic antioxidative diindolylmethane derivative (DIM-D) for the inhibition of UV-induced DNA damage and skin carcinogenesis. UltraFLEX-Nano was prepared with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, 1,2-dioleoyl-3-trimethylammonium-propane, cholesterol and tween-80 by ethanolic injection method; was characterized by Differential Scanning Calorimetric (DSC), Fourier Transform Infrared (FT-IR) and Atomic Force Microscopic (phase-imaging) analyses and permeation studies were performed in dermatomed human skin. The efficacy of DIM-D-UltraFLEX-Nano for skin cancer chemoprevention was evaluated in UVB-induced skin cancer model in vivo. DIM-D-UltraFLEX-Nano formed a stable mono-dispersion (110.50±0.71nm) with >90% encapsulation of DIM-D that was supported by HPLC, DSC, FT-IR and AFM phase imaging. The blank formulation was non-toxic to human embryonic kidney cells. UltraFLEX-Nano was vastly deformable and highly permeable across the stratum corneum; there was significant (p<0.01) skin deposition of DIM-D for UltraFLEX-Nano that was superior to PEG solution (13.83-fold). DIM-D-UltraFLEX-Nano pretreatment delayed the onset of UVB-induced tumorigenesis (2 weeks) and reduced (p<0.05) the number of tumors observed in SKH-1 mice (3.33-fold), which was comparable to pretreatment with sunscreen (SPF30). Also, DIM-D-UltraFLEX-Nano caused decrease (p<0.05) in UV-induced DNA damage (8-hydroxydeoxyguanosine), skin inflammation (PCNA), epidermal hyperplasia (c-myc, CyclinD1), immunosuppression (IL10), cell survival (AKT), metastasis (Vimentin, MMP-9, TIMP1) but increase in apoptosis (p53 and p21). UltraFLEX-Nano was efficient in enhancing the topical delivery of DIM-D. DIM-D-UltraFLEX-Nano was efficacious in delaying skin tumor incidence and multiplicity in SKH mice comparable to sunscreen (SPF30

Systematic Calibration for Ultra-High Accuracy Inertial Measurement Units.

PubMed

Cai, Qingzhong; Yang, Gongliu; Song, Ningfang; Liu, Yiliang

2016-06-22

An inertial navigation system (INS) has been widely used in challenging GPS environments. With the rapid development of modern physics, an atomic gyroscope will come into use in the near future with a predicted accuracy of 5 × 10(-6)°/h or better. However, existing calibration methods and devices can not satisfy the accuracy requirements of future ultra-high accuracy inertial sensors. In this paper, an improved calibration model is established by introducing gyro g-sensitivity errors, accelerometer cross-coupling errors and lever arm errors. A systematic calibration method is proposed based on a 51-state Kalman filter and smoother. Simulation results show that the proposed calibration method can realize the estimation of all the parameters using a common dual-axis turntable. Laboratory and sailing tests prove that the position accuracy in a five-day inertial navigation can be improved about 8% by the proposed calibration method. The accuracy can be improved at least 20% when the position accuracy of the atomic gyro INS can reach a level of 0.1 nautical miles/5 d. Compared with the existing calibration methods, the proposed method, with more error sources and high order small error parameters calibrated for ultra-high accuracy inertial measurement units (IMUs) using common turntables, has a great application potential in future atomic gyro INSs.

Simultaneous structural and environmental loading of an ultra-high performance concrete component

DOT National Transportation Integrated Search

2010-07-01

Ultra-high performance concrete (UHPC) is an advanced cementitious composite material which tends to exhibit superior properties such as increased durability, strength, and long-term stability. This experimental investigation focused on the flexural ...

Ultra-high-throughput Production of III-V/Si Wafer for Electronic and Photonic Applications

PubMed Central

Geum, Dae-Myeong; Park, Min-Su; Lim, Ju Young; Yang, Hyun-Duk; Song, Jin Dong; Kim, Chang Zoo; Yoon, Euijoon; Kim, SangHyeon; Choi, Won Jun

2016-01-01

Si-based integrated circuits have been intensively developed over the past several decades through ultimate device scaling. However, the Si technology has reached the physical limitations of the scaling. These limitations have fuelled the search for alternative active materials (for transistors) and the introduction of optical interconnects (called “Si photonics”). A series of attempts to circumvent the Si technology limits are based on the use of III-V compound semiconductor due to their superior benefits, such as high electron mobility and direct bandgap. To use their physical properties on a Si platform, the formation of high-quality III-V films on the Si (III-V/Si) is the basic technology ; however, implementing this technology using a high-throughput process is not easy. Here, we report new concepts for an ultra-high-throughput heterogeneous integration of high-quality III-V films on the Si using the wafer bonding and epitaxial lift off (ELO) technique. We describe the ultra-fast ELO and also the re-use of the III-V donor wafer after III-V/Si formation. These approaches provide an ultra-high-throughput fabrication of III-V/Si substrates with a high-quality film, which leads to a dramatic cost reduction. As proof-of-concept devices, this paper demonstrates GaAs-based high electron mobility transistors (HEMTs), solar cells, and hetero-junction phototransistors on Si substrates. PMID:26864968

Imprinting high-gradient topographical structures onto optical surfaces using magnetorheological finishing: manufacturing corrective optical elements for high-power laser applications.

PubMed

Menapace, Joseph A; Ehrmann, Paul E; Bayramian, Andrew J; Bullington, Amber; Di Nicola, Jean-Michel G; Haefner, Constantin; Jarboe, Jeffrey; Marshall, Christopher; Schaffers, Kathleen I; Smith, Cal

2016-07-01

Corrective optical elements form an important part of high-precision optical systems. We have developed a method to manufacture high-gradient corrective optical elements for high-power laser systems using deterministic magnetorheological finishing (MRF) imprinting technology. Several process factors need to be considered for polishing ultraprecise topographical structures onto optical surfaces using MRF. They include proper selection of MRF removal function and wheel sizes, detailed MRF tool and interferometry alignment, and optimized MRF polishing schedules. Dependable interferometry also is a key factor in high-gradient component manufacture. A wavefront attenuating cell, which enables reliable measurement of gradients beyond what is attainable using conventional interferometry, is discussed. The results of MRF imprinting a 23 μm deep structure containing gradients over 1.6 μm / mm onto a fused-silica window are presented as an example of the technique's capabilities. This high-gradient element serves as a thermal correction plate in the high-repetition-rate advanced petawatt laser system currently being built at Lawrence Livermore National Laboratory.

Ultra-high resolution computed tomography imaging

DOEpatents

Paulus, Michael J.; Sari-Sarraf, Hamed; Tobin, Jr., Kenneth William; Gleason, Shaun S.; Thomas, Jr., Clarence E.

2002-01-01

A method for ultra-high resolution computed tomography imaging, comprising the steps of: focusing a high energy particle beam, for example x-rays or gamma-rays, onto a target object; acquiring a 2-dimensional projection data set representative of the target object; generating a corrected projection data set by applying a deconvolution algorithm, having an experimentally determined a transfer function, to the 2-dimensional data set; storing the corrected projection data set; incrementally rotating the target object through an angle of approximately 180.degree., and after each the incremental rotation, repeating the radiating, acquiring, generating and storing steps; and, after the rotating step, applying a cone-beam algorithm, for example a modified tomographic reconstruction algorithm, to the corrected projection data sets to generate a 3-dimensional image. The size of the spot focus of the beam is reduced to not greater than approximately 1 micron, and even to not greater than approximately 0.5 microns.

Effects of the ultra-high pressure on structure and α-glucosidase inhibition of polysaccharide from Astragalus.

PubMed

Zhu, Zhen-Yuan; Luo, You; Dong, Guo-Ling; Ren, Yuan-Yuan; Chen, Li-Jing; Guo, Ming-Zhu; Wang, Xiao-Ting; Yang, Xue-Ying; Zhang, Yongmin

2016-06-01

A novel homogeneous polysaccharide fraction (APS) was extracted from Astragalus by hot water and purified by Sephadex G-100 and G-75 column. Its molecular weight was 693kDa. APS and APS with ultra-high pressure treatment exhibited significant inhibitory abilities on a-glucosidase, inhibition rate from high to low in order was 400MPa-APS, 300MPa-APS, 500MPa-APS and APS. The inhibition ​percentage of 400MPa-APS (1.5mg/mL) was 49% (max.). This suggested that the inhibitory activity of APS on a-glucosidase was improved by ultra-high pressure treatment. FT-IR, SEM, CD spectra, atomic force microscope and Congo red test analysis of APS and 400MPa-APS showed ultra-high pressure treatment didn't change the preliminary structure but had an effect on its advanced structure. Copyright © 2016 Elsevier B.V. All rights reserved.

Ultra high speed image processing techniques. [electronic packaging techniques

NASA Technical Reports Server (NTRS)

Anthony, T.; Hoeschele, D. F.; Connery, R.; Ehland, J.; Billings, J.

1981-01-01

Packaging techniques for ultra high speed image processing were developed. These techniques involve the development of a signal feedthrough technique through LSI/VLSI sapphire substrates. This allows the stacking of LSI/VLSI circuit substrates in a 3 dimensional package with greatly reduced length of interconnecting lines between the LSI/VLSI circuits. The reduced parasitic capacitances results in higher LSI/VLSI computational speeds at significantly reduced power consumption levels.

Ultra-high pressure LC for astaxanthin determination in shrimp by-products and active food packaging.

PubMed

Sanches-Silva, A; Ribeiro, T; Albuquerque, T G; Paseiro, P; Sendón, R; de Quirós, A Bernaldo; López-Cervantes, J; Sánchez-Machado, D I; Soto Valdez, H; Angulo, I; Aurrekoetxea, G P; Costa, H S

2013-06-01

Nowadays, there is increasing interest in natural antioxidants from food by-products. Astaxanthin is a potent antioxidant and one of the major carotenoids in crustaceans and salmonids. An ultra-high pressure liquid chromatographic method was developed and validated for the determination of astaxanthin in shrimp by-products, and its migration from new packaging materials to food simulants was also studied. The method uses an UPLC® BEH guard-column (2.1 × 5 mm, 1.7 µm particle size) and an UPLC® BEH analytical column (2.1 × 50 mm, 1.7 µm particle size). Chromatographic separation was achieved using a programmed gradient mobile phase consisting of (A) acetonitrile-methanol (containing 0.05 m ammonium acetate)-dichloromethane (75:20:5, v/v/v) and (B) ultrapure water. This method was evaluated with respect to validation parameters such as linearity, precision, limit of detection, limit of quantification and recovery. Low-density polyethylene films were prepared with different amounts of the lipid fraction of fermented shrimp waste by extrusion, and migration was evaluated into food simulants (isooctane and ethanol 95%, v/v). Migration was not detected under the tested conditions. Copyright © 2012 John Wiley & Sons, Ltd.

Highly informative multiclass profiling of lipids by ultra-high performance liquid chromatography - Low resolution (quadrupole) mass spectrometry by using electrospray ionization and atmospheric pressure chemical ionization interfaces.

PubMed

Beccaria, Marco; Inferrera, Veronica; Rigano, Francesca; Gorynski, Krzysztof; Purcaro, Giorgia; Pawliszyn, Janusz; Dugo, Paola; Mondello, Luigi

2017-08-04

A simple, fast, and versatile method, using an ultra-high performance liquid chromatography system coupled with a low resolution (single quadrupole) mass spectrometer was optimized to perform multiclass lipid profiling of human plasma. Particular attention was made to develop a method suitable for both electrospray ionization and atmospheric pressure chemical ionization interfaces (sequentially in positive- and negative-ion mode), without any modification of the chromatographic conditions (mobile phase, flow-rate, gradient, etc.). Emphasis was given to the extrapolation of the structural information based on the fragmentation pattern obtained using atmospheric pressure chemical ionization interface, under each different ionization condition, highlighting the complementary information obtained using the electrospray ionization interface, of support for related molecule ions identification. Furthermore, mass spectra of phosphatidylserine and phosphatidylinositol obtained using the atmospheric pressure chemical ionization interface are reported and discussed for the first time. Copyright © 2017 Elsevier B.V. All rights reserved.

Microstructure of ultra high performance concrete containing lithium slag.

PubMed

He, Zhi-Hai; Du, Shi-Gui; Chen, Deng

2018-04-03

Lithium slag (LS) is discharged as a byproduct in the process of the lithium carbonate, and it is very urgent to explore an efficient way to recycle LS in order to protect the environments and save resources. Many available supplementary cementitious materials for partial replacement of cement and/or silica fume (SF) can be used to prepare ultra high performance concrete (UHPC). The effect of LS to replace SF partially by weight used as a supplementary cementitious material (0%, 5%, 10% and 15% of binder) on the compressive strengths and microstructure evolution of UHPC has experimentally been studied by multi-techniques including mercury intrusion porosimetry, scanning electron microscope and nanoindentation technique. The results show that the use of LS degrades the microstructure of UHPC at early ages, and however, the use of LS with the appropriate content improves microstructure of UHPC at later ages. The hydration products of UHPC are mainly dominated by ultra-high density calcium-silicate-hydrate (UHD C-S-H) and interfacial transition zone (ITZ) in UHPC has similar compact microstructure with the matrix. The use of LS improves the hydration degree of UHPC and increases the elastic modulus of ITZ in UHPC. LS is a promising substitute for SF for preparation UHPC. Copyright © 2018 Elsevier B.V. All rights reserved.

Development of Non-Proprietary Ultra High Performance Concrete : Final Presentation : November, 2017

DOT National Transportation Integrated Search

2017-11-01

Ultra-high performance concrete (UHPC) has mechanical and durability properties that far exceed those of conventional concrete. Particularly, UHPC has compressive and post-cracking tensile strengths of around 20 ksi and 0.72 ksi, respectively. Thus, ...

Prescribed Velocity Gradients for Highly Viscous SPH Fluids with Vorticity Diffusion.

PubMed

Peer, Andreas; Teschner, Matthias

2017-12-01

Working with prescribed velocity gradients is a promising approach to efficiently and robustly simulate highly viscous SPH fluids. Such approaches allow to explicitly and independently process shear rate, spin, and expansion rate. This can be used to, e.g., avoid interferences between pressure and viscosity solvers. Another interesting aspect is the possibility to explicitly process the vorticity, e.g., to preserve the vorticity. In this context, this paper proposes a novel variant of the prescribed-gradient idea that handles vorticity in a physically motivated way. In contrast to a less appropriate vorticity preservation that has been used in a previous approach, vorticity is diffused. The paper illustrates the utility of the vorticity diffusion. Therefore, comparisons of the proposed vorticity diffusion with vorticity preservation and additionally with vorticity damping are presented. The paper further discusses the relation between prescribed velocity gradients and prescribed velocity Laplacians which improves the intuition behind the prescribed-gradient method for highly viscous SPH fluids. Finally, the paper discusses the relation of the proposed method to a physically correct implicit viscosity formulation.

Hexagonal gradient scheme with RF spoiling improves spoiling performance for high-flip-angle fast gradient echo imaging.

PubMed

Hess, Aaron T; Robson, Matthew D

2017-03-01

To present a framework in which time-varying gradients are applied with RF spoiling to reduce unwanted signal, particularly at high flip angles. A time-varying gradient spoiler scheme compatible with RF spoiling is defined, in which spoiler gradients cycle through the vertices of a hexagon, which we call hexagonal spoiling. The method is compared with a traditional constant spoiling gradient both in the transition to and in the steady state. Extended phase graph (EPG) simulations, phantom acquisitions, and in vivo images were used to assess the method. Simulations, phantom and in vivo experiments showed that unwanted signal was markedly reduced by employing hexagonal spoiling, both in the transition to and in the steady state. For adipose tissue at 1.5 Tesla, the unwanted signal in the steady state with a 60 ° flip angle was reduced from 22% with constant spoiling to 2% with hexagonal spoiling. A time-varying gradient spoiler scheme that works with RF spoiling, called "hexagonal spoiling," has been presented and found to offer improved spoiling over the traditional constant spoiling gradient. Magn Reson Med 77:1231-1237, 2017. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine.

Ultra-high performance fiber-reinforced concrete (UHPFRC) for infrastructure rehabilitation Volume II : behavior of ultra-high strength concrete bridge deck panels compared to conventional stay-in-place deck panels

DOT National Transportation Integrated Search

2017-08-01

The remarkable features of ultra-high performance concrete (UHPC) have been reported. Its application in bridge construction has been an active research area in recent years, attributed to its higher compressive strength, higher ductility and reduced...

Long range surface plasmon resonance with ultra-high penetration depth for self-referenced sensing and ultra-low detection limit using diverging beam approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Isaacs, Sivan, E-mail: sivan.isaacs@gmail.com; Abdulhalim, Ibrahim; NEW CREATE Programme, School of Materials Science and Engineering, 1 CREATE Way, Research Wing, #02-06/08, Singapore 138602

2015-05-11

Using an insulator-metal-insulator structure with dielectric having refractive index (RI) larger than the analyte, long range surface plasmon (SP) resonance exhibiting ultra-high penetration depth is demonstrated for sensing applications of large bioentities at wavelengths in the visible range. Based on the diverging beam approach in Kretschmann-Raether configuration, one of the SP resonances is shown to shift in response to changes in the analyte RI while the other is fixed; thus, it can be used as a built in reference. The combination of the high sensitivity, high penetration depth and self-reference using the diverging beam approach in which a dark linemore » is detected of the high sensitivity, high penetration depth, self-reference, and the diverging beam approach in which a dark line is detected using large number of camera pixels with a smart algorithm for sub-pixel resolution, a sensor with ultra-low detection limit is demonstrated suitable for large bioentities.« less

Imprinting high-gradient topographical structures onto optical surfaces using magnetorheological finishing: Manufacturing corrective optical elements for high-power laser applications

DOE PAGES

Menapace, Joseph A.; Ehrmann, Paul E.; Bayramian, Andrew J.; ...

2016-03-15

Corrective optical elements form an important part of high-precision optical systems. We have developed a method to manufacture high-gradient corrective optical elements for high-power laser systems using deterministic magnetorheological finishing (MRF) imprinting technology. Several process factors need to be considered for polishing ultraprecise topographical structures onto optical surfaces using MRF. They include proper selection of MRF removal function and wheel sizes, detailed MRF tool and interferometry alignment, and optimized MRF polishing schedules. Dependable interferometry also is a key factor in high-gradient component manufacture. A wavefront attenuating cell, which enables reliable measurement of gradients beyond what is attainable using conventional interferometry,more » is discussed. The results of MRF imprinting a 23 μm deep structure containing gradients over 1.6 μm / mm onto a fused-silica window are presented as an example of the technique’s capabilities. As a result, this high-gradient element serves as a thermal correction plate in the high-repetition-rate advanced petawatt laser system currently being built at Lawrence Livermore National Laboratory.« less

Comparison of ultra-high performance supercritical fluid chromatography and ultra-high performance liquid chromatography for the separation of spirostanol saponins.

PubMed

Zhu, Ling-Ling; Zhao, Yang; Xu, Yong-Wei; Sun, Qing-Long; Sun, Xin-Guang; Kang, Li-Ping; Yan, Ren-Yi; Zhang, Jie; Liu, Chao; Ma, Bai-Ping

2016-02-20

Spirostanol saponins are important active components of some herb medicines, and their isolation and purification are crucial for the research and development of traditional Chinese medicines. We aimed to compare the separation of spirostanol saponins by ultra-high performance supercritical fluid chromatography (UHPSFC) and ultra-high performance liquid chromatography (UHPLC). Four groups of spirostanol saponins were separated respectively by UHPSFC and UHPLC. After optimization, UHPSFC was performed with a HSS C18 SB column or a Diol column and with methanol as the co-solvent. A BEH C18 column and mobile phase containing water (with 0.1% formic acid) and acetonitrile were used in UHPLC. We found that UHPSFC could be performed automatically and quickly. It is effective in separating the spirostanol saponins which share the same aglycone and vary in sugar chains, and is very sensitive to the number and the position of hydroxyl groups in aglycones. However, the resolution of spirostanol saponins with different aglycones and the same sugar moiety by UHPSFC was not ideal and could be resolved by UHPLC instead. UHPLC is good at differentiating the variation in aglycones, and is influenced by double bonds in aglycones. Therefore, UHPLC and UHPSFC are complementary in separating spirostanol saponins. Considering the naturally produced spirostanol saponins in herb medicines are different both in aglycones and in sugar chains, a better separation can be achieved by combination of UHPLC and UHPSFC. UHPSFC is a powerful technique for improving the resolution when UHPLC cannot resolve a mixture of spirostanol saponins and vice versa. Copyright © 2015 Elsevier B.V. All rights reserved.

Ultra-high cooling rate utilizing thin film evaporation

NASA Astrophysics Data System (ADS)

Su, Fengmin; Ma, Hongbin; Han, Xu; Chen, Hsiu-hung; Tian, Bohan

2012-09-01

This research introduces a cell cryopreservation method, which utilizes thin film evaporation and provides an ultra-high cooling rate. The microstructured surface forming the thin film evaporation was fabricated from copper microparticles with an average diameter of 50 μm. Experimental results showed that a cooling rate of approximately 5×104 °C/min was achieved in a temperature range from 10 °C to -187 °C. The current investigation will give birth to a cell cryopreservation method through vitrification with relatively low concentrations of cryoprotectants.

SU-F-J-45: Sparing Normal Tissue with Ultra-High Dose Rate in Radiation Therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feng, Y

Purpose: To spare normal tissue by reducing the location uncertainty of a moving target, we proposed an ultra-high dose rate system and evaluated. Methods: High energy electrons generated with a linear accelerator were injected into a storage ring to be accumulated. The number of the electrons in the ring was determined based on the prescribed radiation dose. The dose was delivered within a millisecond, when an online imaging system found that the target was in the position that was consistent with that in a treatment plan. In such a short time period, the displacement of the target was negligible. Themore » margin added to the clinical target volume (CTV) could be reduced that was evaluated by comparing of volumes between CTV and ITV in 14 cases of lung stereotactic body radiation therapy (SBRT) treatments. A design of the ultra-high dose rate system was evaluated based clinical needs and the recent developments of low energy (a few MeV) electron storage ring. Results: This design of ultra-high dose rate system was feasible based on the techniques currently available. The reduction of a target volume was significant by reducing the margin that accounted the motion of the target. ∼50% volume reduction of the internal target volume (ITV) could be achieved in lung SBRT treatments. Conclusion: With this innovation of ultra-high dose rate system, the margin of target is able to be significantly reduced. It will reduce treatment time of gating and allow precisely specified gating window to improve the accuracy of dose delivering.« less

Rapid brain MRI acquisition techniques at ultra-high fields

PubMed Central

Setsompop, Kawin; Feinberg, David A.; Polimeni, Jonathan R.

2017-01-01

Ultra-high-field MRI provides large increases in signal-to-noise ratio as well as enhancement of several contrast mechanisms in both structural and functional imaging. Combined, these gains result in a substantial boost in contrast-to-noise ratio that can be exploited for higher spatial resolution imaging to extract finer-scale information about the brain. With increased spatial resolution, however, is a concurrent increased image encoding burden that can cause unacceptably long scan times for structural imaging and slow temporal sampling of the hemodynamic response in functional MRI—particularly when whole-brain imaging is desired. To address this issue, new directions of imaging technology development—such as the move from conventional 2D slice-by-slice imaging to more efficient Simultaneous MultiSlice (SMS) or MultiBand imaging (which can be viewed as “pseudo-3D” encoding) as well as full 3D imaging—have provided dramatic improvements in acquisition speed. Such imaging paradigms provide higher SNR efficiency as well as improved encoding efficiency. Moreover, SMS and 3D imaging can make better use of coil sensitivity information in multi-channel receiver arrays used for parallel imaging acquisitions through controlled aliasing in multiple spatial directions. This has enabled unprecedented acceleration factors of an order of magnitude or higher in these imaging acquisition schemes, with low image artifact levels and high SNR. Here we review the latest developments of SMS and 3D imaging methods and related technologies at ultra-high field for rapid high-resolution functional and structural imaging of the brain. PMID:26835884

Live Ultra-High Definition from the International Space Station

NASA Technical Reports Server (NTRS)

Grubbs, Rodney; George, Sandy

2017-01-01

The first ever live downlink of Ultra-High Definition (UHD) video from the International Space Station (ISS) was the highlight of a 'Super Session' at the National Association of Broadcasters (NAB) in April 2017. The Ultra-High Definition video downlink from the ISS all the way to the Las Vegas Convention Center required considerable planning, pushed the limits of conventional video distribution from a space-craft, and was the first use of High Efficiency Video Coding (HEVC) from a space-craft. The live event at NAB will serve as a pathfinder for more routine downlinks of UHD as well as use of HEVC for conventional HD downlinks to save bandwidth. HEVC may also enable live Virtual Reality video downlinks from the ISS. This paper will describe the overall work flow and routing of the UHD video, how audio was synchronized even though the video and audio were received many seconds apart from each other, and how the demonstration paves the way for not only more efficient video distribution from the ISS, but also serves as a pathfinder for more complex video distribution from deep space. The paper will also describe how a 'live' event was staged when the UHD coming from the ISS had a latency of 10+ seconds. Finally, the paper will discuss how NASA is leveraging commercial technologies for use on-orbit vs. creating technology as was required during the Apollo Moon Program and early space age.

Demonstration of Current Profile Shaping using Double Dog-Leg Emittance Exchange Beam Line at Argonne Wakefield Accelerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ha, Gwanghui; Cho, Moo-Hyun; Conde, Manoel

Emittance exchange (EEX) based longitudinal current profile shaping is the one of the promising current profile shaping technique. This method can generate high quality arbitrary current profiles under the ideal conditions. The double dog-leg EEX beam line was recently installed at the Argonne Wakefield Accelerator (AWA) to explore the shaping capability and confirm the quality of this method. To demonstrate the arbitrary current profile generation, several different transverse masks are applied to generate different final current profiles. The phase space slopes and the charge of incoming beam are varied to observe and suppress the aberrations on the ideal profile. Wemore » present current profile shaping results, aberrations on the shaped profile, and its suppression.« less

Laser Wakefield Acceleration Experiments Using HERCULES Laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matsuoka, T.; McGuffey, C.; Dollar, F.

2009-07-25

Laser wakefield acceleration (LWFA) in a supersonic gas-jet using a self-guided laser pulse was studied by changing laser power and plasma electron density. The recently upgraded HERCULES laser facility equipped with wavefront correction enables a peak intensity of 6.1x10{sup 19} W/cm{sup 2} at laser power of 80 TW to be delivered to the gas-jet using F/10 focusing optics. We found that electron beam charge was increased significantly with an increase of laser power from 30 TW to 80 TW and showed density threshold behavior at a fixed laser power. We also studied the influence of laser focusing conditions by changingmore » the f-number of the optics to F/15 and found an increase in density threshold for electron production compared to the F/10 configuration. The analysis of different phenomena such as betatron motion of electrons, side scattering of the laser pulse for different focusing conditions, the influence of plasma density down ramp on LWFA are shown.« less

A Novel Study Connecting Ultra-High Energy Cosmic Rays, Neutrinos, and Gamma-Rays

NASA Astrophysics Data System (ADS)

Coenders, Stefan; Resconi, Elisa; Padovani, Paolo; Giommi, Paolo; Caccianiga, Lorenzo

We present a novel study connecting ultra-high energy cosmic rays, neutrinos, and gamma-rays with the objective to identify common counterparts of the three astrophysical messengers. In the test presented here, we first identify potential hadronic sources by filtering gamma-ray emitters that are in spatial coincidence with IceCube neutrinos. Subsequently, these objects are correlated against ultra-high energy cosmic rays detected by the Pierre Auger Observatory and the Telescope Array, scanning in gamma-ray flux and angular separation between sources and cosmic rays. A maximal excess of 80 cosmic rays (41.9 expected) is observed for the second catalog of hard Fermi-LAT objects of blazars of the high synchrotron peak type. This corresponds to a deviation from the null-hypothesis of 2.94σ . No excess is observed for objects not in spatial connection with neutrinos. The gamma-ray sources that make up the excess are blazars of the high synchrotron peak type.

On the properties of synchrotron-like X-ray emission from laser wakefield accelerated electron beams

NASA Astrophysics Data System (ADS)

McGuffey, C.; Schumaker, W.; Matsuoka, T.; Chvykov, V.; Dollar, F.; Kalintchenko, G.; Kneip, S.; Najmudin, Z.; Mangles, S. P. D.; Vargas, M.; Yanovsky, V.; Maksimchuk, A.; Thomas, A. G. R.; Krushelnick, K.

2018-04-01

The electric and magnetic fields responsible for electron acceleration in a Laser Wakefield Accelerator (LWFA) also cause electrons to radiate x-ray photons. Such x-ray pulses have several desirable properties including short duration and being well collimated with tunable high energy. We measure the scaling of this x-ray source experimentally up to laser powers greater than 100 TW. An increase in laser power allows electron trapping at a lower density as well as with an increased trapped charge. These effects resulted in an x-ray fluence that was measured to increase non-linearly with laser power. The fluence of x-rays was also compared with that produced from K-α emission resulting from a solid target interaction for the same energy laser pulse. The flux was shown to be comparable, but the LWFA x-rays had a significantly smaller source size. This indicates that such a source may be useful as a backlighter for probing high energy density plasmas with ultrafast temporal resolution.

A Manganin Thin Film Ultra-High Pressure Sensor for Microscale Detonation Pressure Measurement

PubMed Central

Zhang, Guodong; Zhao, Yulong; Zhao, Yun; Wang, Xinchen; Ren, Wei; Li, Hui; Zhao, You

2018-01-01

With the development of energetic materials (EMs) and microelectromechanical systems (MEMS) initiating explosive devices, the measurement of detonation pressure generated by EMs in the microscale has become a pressing need. This paper develops a manganin thin film ultra-high pressure sensor based on MEMS technology for measuring the output pressure from micro-detonator. A reliable coefficient is proposed for designing the sensor’s sensitive element better. The sensor employs sandwich structure: the substrate uses a 0.5 mm thick alumina ceramic, the manganin sensitive element with a size of 0.2 mm × 0.1 mm × 2 μm and copper electrodes of 2 μm thick are sputtered sequentially on the substrate, and a 25 μm thick insulating layer of polyimide is wrapped on the sensitive element. The static test shows that the piezoresistive coefficient of manganin thin film is 0.0125 GPa−1. The dynamic experiment indicates that the detonation pressure of micro-detonator is 12.66 GPa, and the response time of the sensor is 37 ns. In a word, the sensor developed in this study is suitable for measuring ultra-high pressure in microscale and has a shorter response time than that of foil-like manganin gauges. Simultaneously, this study could be beneficial to research on ultra-high-pressure sensors with smaller size. PMID:29494519

Quality evaluation of Semen Cassiae (Cassia obtusifolia L.) by using ultra-high performance liquid chromatography coupled with mass spectrometry.

PubMed

Zhang, Wei-Dong; Wang, Ying; Wang, Qing; Yang, Wan-Jun; Gu, Yi; Wang, Rong; Song, Xiao-Mei; Wang, Xiao-Juan

2012-08-01

A sensitive and reliable ultra-high performance liquid chromatography-electrospray ionization-tandem mass spectrometry has been developed and partially validated to evaluate the quality of Semen Cassiae (Cassia obtusifolia L.) through simultaneous determination of 11 anthraquinones and two naphtha-γ-pyrone compounds. The analysis was achieved on a Poroshell 120 EC-C(18) column (100 mm × 2.1 mm, 2.7 μm; Agilent, Palo Alto, CA, USA) with gradient elution using a mobile phase that consisted of acetonitrile-water (30 mM ammonium acetate) at a flow rate of 0.4 mL/min. For quantitative analysis, all calibration curves showed perfect linear regression (r(2) > 0.99) within the testing range. This method was also validated with respect to precision and accuracy, and was successfully applied to quantify the 13 components in nine batches of Semen Cassiae samples from different areas. The performance of developed method was compared with that of conventional high-performance liquid chromatography method. The significant advantages of the former include high-speed chromatographic separation, four times faster than high-performance liquid chromatography with conventional columns, and great enhancement in sensitivity. This developed method provided a new basis for overall assessment on quality of Semen Cassiae. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ultra-High Temperature Materials Characterization for Space and Missile Applications

NASA Technical Reports Server (NTRS)

Rogers, Jan; Hyers, Robert

2007-01-01

Numerous advanced space and missile technologies including propulsion systems require operations at high temperatures. Some very high-temperature materials are being developed to meet these needs, including refractory metal alloys, carbides, borides, and silicides. System design requires data for materials properties at operating temperatures. Materials property data are not available at the desired operating temperatures for many materials of interest. The objective of this work is to provide important physical property data at ultra-high temperatures. The MSFC Electrostatic Levitation (ESL) facility can provide measurements of thermophysical properties which include: creep strength, emissivity, density and thermal expansion. ESL uses electrostatic fields to position samples between electrodes during processing and characterization experiments. Samples float between the electrodes during studies and are free from any contact with a container or test apparatus. This provides a high purity environment for the study of high-temperature, reactive materials. ESL can be used to process a wide variety of materials including metals, alloys, ceramics, glasses and semiconductors. A system for the determination of total hemispherical emissivity is being developed for the MSFC ESL facility by AZ Technology Inc. The instrument has been designed to provide emissivity measurements for samples during ESL experiments over the temperature range 700-3400K. A novel non-contact technique for the determination of high-temperature creep strength has been developed. Data from selected ESL-based characterization studies will be presented. The ESL technique could advance space and missile technologies by advancing the knowledge base and the technology readiness level for ultra-high temperature materials. Applications include non-eroding nozzle materials and lightweight, high-temperature alloys for turbines and structures.

Kinome expression profiling of human neuroblastoma tumors identifies potential drug targets for ultra high-risk patients.

PubMed

Russo, Roberta; Cimmino, Flora; Pezone, Lucia; Manna, Francesco; Avitabile, Marianna; Langella, Concetta; Koster, Jan; Casale, Fiorina; Raia, Maddalena; Viola, Giampietro; Fischer, Matthias; Iolascon, Achille; Capasso, Mario

2017-10-01

Neuroblastoma (NBL) accounts for >7% of malignancies in patients younger than 15 years. Low- and intermediate-risk patients exhibit excellent or good prognosis after treatment, whereas for high-risk (HR) patients, the estimated 5-year survival rates is still <40%. The ability to stratify HR patients that will not respond to standard treatment strategies is critical for informed treatment decisions. In this study, we have generated a specific kinome gene signature, named Kinome-27, which is able to identify a subset of HR-NBL tumors, named ultra-HR NBL, with highly aggressive clinical behavior that not adequately respond to standard treatments. We have demonstrated that NBL cell lines expressing the same kinome signature of ultra-HR tumors (ultra-HR-like cell lines) may be selectively targeted by the use of two drugs [suberoylanilide hydroxamic acid (SAHA) and Radicicol], and that the synergic combination of these drugs is able to block the ultra-HR-like cells in G2/M phase of cell cycle. The use of our signature in clinical practice will allow identifying patients with negative outcome, which would benefit from new and more personalized treatments. Preclinical in vivo studies are needed to consolidate the SAHA and Radicicol treatment in ultra-HR NBL patients. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Ultra-high resolution and high-brightness AMOLED

NASA Astrophysics Data System (ADS)

Wacyk, Ihor; Ghosh, Amal; Prache, Olivier; Draper, Russ; Fellowes, Dave

2012-06-01

As part of its continuing effort to improve both the resolution and optical performance of AMOLED microdisplays, eMagin has recently developed an SXGA (1280×3×1024) microdisplay under a US Army RDECOM CERDEC NVESD contract that combines the world's smallest OLED pixel pitch with an ultra-high brightness green OLED emitter. This development is aimed at next-generation HMD systems with "see-through" and daylight imaging requirements. The OLED pixel array is built on a 0.18-micron CMOS backplane and contains over 4 million individually addressable pixels with a pixel pitch of 2.7 × 8.1 microns, resulting in an active area of 0.52 inches diagonal. Using both spatial and temporal enhancement, the display can provide over 10-bits of gray-level control for high dynamic range applications. The new pixel design also enables the future implementation of a full-color QSXGA (2560 × RGB × 2048) microdisplay in an active area of only 1.05 inch diagonal. A low-power serialized low-voltage-differential-signaling (LVDS) interface is integrated into the display for use as a remote video link for tethered systems. The new SXGA backplane has been combined with the high-brightness green OLED device developed by eMagin under an NVESD contract. This OLED device has produced an output brightness of more than 8000fL with all pixels on; lifetime measurements are currently underway and will presented at the meeting. This paper will describe the operational features and first optical and electrical test results of the new SXGA demonstrator microdisplay.

Metallicity gradient of the thick disc progenitor at high redshift

NASA Astrophysics Data System (ADS)

Kawata, Daisuke; Allende Prieto, Carlos; Brook, Chris B.; Casagrande, Luca; Ciucă, Ioana; Gibson, Brad K.; Grand, Robert J. J.; Hayden, Michael R.; Hunt, Jason A. S.

2018-01-01

We have developed a novel Markov Chain Monte Carlo chemical 'painting' technique to explore possible radial and vertical metallicity gradients for the thick disc progenitor. In our analysis, we match an N-body simulation to the data from the Apache Point Observatory Galactic Evolution Experiment survey. We assume that the thick disc has a constant scaleheight and has completed its formation at an early epoch, after which time radial mixing of its stars has taken place. Under these assumptions, we find that the initial radial metallicity gradient of the thick disc progenitor should not be negative, but either flat or even positive, to explain the current negative vertical metallicity gradient of the thick disc. Our study suggests that the thick disc was built-up in an inside-out and upside-down fashion, and older, smaller and thicker populations are more metal poor. In this case, star-forming discs at different epochs of the thick disc formation are allowed to have different radial metallicity gradients, including a negative one, which helps to explain a variety of slopes observed in high-redshift disc galaxies. This scenario helps to explain the positive slope of the metallicity-rotation velocity relation observed for the Galactic thick disc. On the other hand, radial mixing flattens the slope of an existing gradient.

Rapid determination of the various native forms of vitamin B6 and B2 in cow's milk using ultra-high performance liquid chromatography.

PubMed

Schmidt, A; Schreiner, M G; Mayer, H K

2017-06-02

As the formation of pyridoxal phosphate, the active cofactor of vitamin B 6 , is dependent on riboflavin 5-phosphate, we propose a fast and simple ultra-high performance liquid chromatography method for the simultaneous determination of the native B 6 vitamers pyridoxal, pyridoxine, pyridoxamine, their mono phosphorus esters and 4-pyridoxic acid as well as vitamin B 2 as riboflavin and its phosphorus ester riboflavin 5-phosphate in milk. Separation was achieved under 6.0min by reversed-phase and pH gradient elution. Sample preparation was optimized regarding various acids and pH levels. Changes in those parameters led to significant deviations of sample matrix breakdown efficiency. The optimized method was then validated regarding specificity, accuracy, precision, linearity, range, detection and quantification limits. As the method performed satisfactory, is was used to study commercial liquid cow's milk (n=31), regarding effects of the employed preservation technique (pasteurization, extended shelf-life, ultra-high temperature) on the composition and content of B 6 and B 2 vitamers. In cow's milk, vitamin B 6 mostly consists of pyridoxal and its phosphate ester, with pyridoxal phosphate being the bulk component. The catabolite of the vitamin B 6 metabolism, 4-pyridoxic acid was present in significant amounts in all studied samples, with up to 2.69μmolL -1 . Vitamin B 2 was present as riboflavin and its phosphate ester up to 12.86μmolL -1 . Copyright © 2017 Elsevier B.V. All rights reserved.

Ultra-high temperature tensile properties of ODS steel claddings under severe accident conditions

NASA Astrophysics Data System (ADS)

Yano, Y.; Tanno, T.; Oka, H.; Ohtsuka, S.; Inoue, T.; Kato, S.; Furukawa, T.; Uwaba, T.; Kaito, T.; Ukai, S.; Oono, N.; Kimura, A.; Hayashi, S.; Torimaru, T.

2017-04-01

Ultra-high temperature ring tensile tests were performed to investigate the tensile behavior of oxide dispersion strengthened (ODS) steel claddings and wrapper materials under severe accident conditions with temperatures ranging from room temperature to 1400 °C which is close to the melting point of core materials. The experimental results showed that the tensile strength of 9Cr-ODS steel claddings was highest in the core materials at ultra-high temperatures of 900-1200 °C, but there was significant degradation in the tensile strength of 9Cr-ODS steel claddings above 1200 °C. This degradation was attributed to grain boundary sliding deformation with γ/δ transformation, which is associated with reduced ductility. By contrast, the tensile strength of recrystallized 12Cr-ODS and FeCrAl-ODS steel claddings retained its high value above 1200 °C, unlike the other tested materials.

Ultra-high current density thin-film Si diode

DOEpatents

Wang; Qi

2008-04-22

A combination of a thin-film .mu.c-Si and a-Si:H containing diode structure characterized by an ultra-high current density that exceeds 1000 A/cm.sup.2, comprising: a substrate; a bottom metal layer disposed on the substrate; an n-layer of .mu.c-Si deposited the bottom metal layer; an i-layer of .mu.c-Si deposited on the n-layer; a buffer layer of a-Si:H deposited on the i-layer, a p-layer of .mu.c-Si deposited on the buffer layer; and a top metal layer deposited on the p-layer.

Wide band cryogenic ultra-high vacuum microwave absorber

DOEpatents

Campisi, I.E.

1992-05-12

An absorber waveguide assembly for absorbing higher order modes of microwave energy under cryogenic ultra-high vacuum conditions, that absorbs wide-band multi-mode energy. The absorber is of a special triangular shape, made from flat tiles of silicon carbide and aluminum nitride. The leading sharp end of the absorber is located in a corner of the waveguide and tapers to a larger cross-sectional area whose center is located approximately in the center of the wave guide. The absorber is relatively short, being of less height than the maximum width of the waveguide. 11 figs.

Wide band cryogenic ultra-high vacuum microwave absorber

DOEpatents

Campisi, Isidoro E.

1992-01-01

An absorber wave guide assembly for absorbing higher order modes of microwave energy under cryogenic ultra-high vacuum conditions, that absorbs wide-band multi-mode energy. The absorber is of a special triangular shape, made from flat tiles of silicon carbide and aluminum nitride. The leading sharp end of the absorber is located in a corner of the wave guide and tapers to a larger cross-sectional area whose center is located approximately in the center of the wave guide. The absorber is relatively short, being of less height than the maximum width of the wave guide.

Plasma Wakefield Acceleration and FACET - Facilities for Accelerator Science and Experimental Test Beams at SLAC

ScienceCinema

Seryi, Andrei

2017-12-22

Plasma wakefield acceleration is one of the most promising approaches to advancing accelerator technology. This approach offers a potential 1,000-fold or more increase in acceleration over a given distance, compared to existing accelerators.  FACET, enabled by the Recovery Act funds, will study plasma acceleration, using short, intense pulses of electrons and positrons. In this lecture, the physics of plasma acceleration and features of FACET will be presented.  

Ultra high-definition video: convergence toward 100Gbps and beyond for digital A/V connectivity with fiber optics

NASA Astrophysics Data System (ADS)

Parekh, Devang; Nguyen, Nguyen X.

2018-02-01

The recent advent of Ultra-high-definition television (also known as Ultra HD television, Ultra HD, UHDTV, UHD and Super Hi-Vision) has accelerated a demand for a Fiber-in-the-Premises video communication (VCOM) solution that converges toward 100Gbps and Beyond. Hybrid Active-Optical-Cables (AOC) is a holistic connectivity platform well suited for this "The Last Yard" connectivity; as it combines both copper and fiber optics to deliver a high data-rate and power transmission needed. While technically feasible yet challenging to manufacture, hybrid-AOC could be a holygrail fiber-optics solution that dwarfs the volume of both telecom and datacom connection in the foreseeable future.

A Novel Femtosecond-gated, High-resolution, Frequency-shifted Shearing Interferometry Technique for Probing Pre-plasma Expansion in Ultra-intense Laser Experiments

DTIC Science & Technology

2014-07-17

frequency-shifted shearing interferometry technique for probing pre-plasma expansion in ultra-intense laser experimentsa) Ultra-intense laser -matter...interaction experiments (>1018 W/cm2) with dense targets are highly sensitive to the effect of laser “noise” (in the form of pre-pulses) preceding the...interferometry technique for probing pre- plasma expansion in ultra-intense laser experimentsa) Report Title Ultra-intense laser -matter interaction

Ultra-high resolution spectral domain optical coherence tomography using supercontinuum light source

NASA Astrophysics Data System (ADS)

Lim, Yiheng; Yatagai, Toyohiko; Otani, Yukitoshi

2016-04-01

An ultra-high resolution spectral domain optical coherence tomography (SD-OCT) was developed using a cost-effective supercontinuum laser. A spectral filter consists of a dispersive prism, a cylindrical lens and a right-angle prism was built to transmit the wavelengths in range 680-940 nm to the OCT system. The SD-OCT has achieved 1.9 μm axial resolution and the sensitivity was estimated to be 91.5 dB. A zero-crossing fringes matching method which maps the wavelengths to the pixel indices of the spectrometer was proposed for the OCT spectral calibration. A double sided foam tape as a static sample and the tip of a middle finger as a biological sample were measured by the OCT. The adhesive and the internal structure of the foam of the tape were successfully visualized in three dimensions. Sweat ducts was clearly observed in the OCT images at very high resolution. To the best of our knowledge, this is the first demonstration of ultra-high resolution visualization of sweat duct by OCT.

Fracture Mechanisms of Zirconium Diboride Ultra-High Temperature Ceramics under Pulse Loading

NASA Astrophysics Data System (ADS)

Skripnyak, Vladimir V.; Bragov, Anatolii M.; Skripnyak, Vladimir A.; Lomunov, Andrei K.; Skripnyak, Evgeniya G.; Vaganova, Irina K.

2015-06-01

Mechanisms of failure in ultra-high temperature ceramics (UHTC) based on zirconium diboride under pulse loading were studied experimentally by the method of SHPB and theoretically using the multiscale simulation method. The obtained experimental and numerical data are evidence of the quasi-brittle fracture character of nanostructured zirconium diboride ceramics under compression and tension at high strain rates and the room temperatures. Damage of nanostructured porous zirconium diboride -based UHTC can be formed under stress pulse amplitude below the Hugoniot elastic limit. Fracture of nanostructured ultra-high temperature ceramics under pulse and shock-wave loadings is provided by fast processes of intercrystalline brittle fracture and relatively slow processes of quasi-brittle failure via growth and coalescence of microcracks. A decrease of the shear strength can be caused by nano-voids clusters in vicinity of triple junctions between ceramic matrix grains and ultrafine-grained ceramics. This research was supported by grants from ``The Tomsk State University Academic D.I. Mendeleev Fund Program'' and also N. I. Lobachevski State University of Nizhny Novgorod (Grant of post graduate mobility).

Plasmonic metamaterial for electromagnetically induced transparency analogue and ultra-high figure of merit sensor

PubMed Central

Wu, Dong; Liu, Yumin; Yu, Li; Yu, Zhongyuan; Chen, Lei; Li, Ruifang; Ma, Rui; Liu, Chang; Zhang, Jinqiannan; Ye, Han

2017-01-01

In this work, using finite-difference time-domain method, we propose and numerically demonstrate a novel way to achieve electromagnetically induced transparency (EIT) phenomenon in the reflection spectrum by stacking two different types of coupling effect among different elements of the designed metamaterial. Compared with the conventional EIT-like analogues coming from only one type of coupling effect between bright and dark meta-atoms on the same plane, to our knowledge the novel approach is the first to realize the optically active and precise control of the wavelength position of EIT-like phenomenon using optical metamaterials. An on-to-off dynamic control of the EIT-like phenomenon also can be achieved by changing the refractive index of the dielectric substrate via adjusting an optical pump pulse. Furthermore, in near infrared region, the metamaterial structure can be operated as an ultra-high resolution refractive index sensor with an ultra-high figure of merit (FOM) reaching 3200, which remarkably improve the FOM value of plasmonic refractive index sensors. The novel approach realizing EIT-like spectral shape with easy adjustment to the working wavelengths will open up new avenues for future research and practical application of active plasmonic switch, ultra-high resolution sensors and active slow-light devices. PMID:28332629

A Novel Method for Electroplating Ultra-High-Strength Glassy Metals

NASA Technical Reports Server (NTRS)

Ramsey, Brian; Engelhaupt, Darell; Six, N. Frank (Technical Monitor)

2002-01-01

A novel method for electroplating ultra-high-strength glassy metals, nickel-phosphorous and nickel-cobalt-phosphorous, has been developed at NASA Marshall Space Flight Center, cooperatively with the University of Alabama in Huntsville. Traditionally, thin coatings of these metals are achieved via electroless deposition. Benefits of the new electrolytic process include thick, low-stress deposits, free standing shapes, lower plating temperature, low maintenance, and safer operation with substantially lower cost.

Fast Spectroscopic Imaging and Field Compensation Using Frequency Modulation at Ultra-High-Field

NASA Astrophysics Data System (ADS)

Jang, Albert Woo Ju

The high energy phosphates (HEP) in the myocardium, which are critical to understanding the cardiac function in both normal and pathophysiologic states, can be assessed non-invasively in vivo using phosphorus-31 (31P) spectroscopy. Compared to proton, for the same volume and magnetic field strength, the available signal-to-noise (SNR) ratio of the HEP metabolites is orders of magnitude lower mainly due to its intrinsically low concentration. Hence, cardiac spectroscopy greatly benefits when performed at ultra-high-fields (UHF, ≥ 7 T), both in terms of increased SNR and increased spectroscopic resolution. However, at ultra-high-field strengths, complications arise from the RF transmit wavelength becoming comparable or smaller than the field-of-view (FOV), thus exhibiting wave-like behavior. Furthermore, even with the spectroscopic resolution afforded at UHF, measuring myocardial inorganic phosphate (Pi) is still a challenge and has been a major barrier in extracting the ATP turnover rate. Recently, an indirect way of extracting the ATP hydrolysis rate forgoing direct measurement of Pi was established. In this work, we combine this method with the T1 nom method to monitor the transmural distribution of forward creatine kinase reaction (kf,CK) and ATP hydrolysis rate (kr,ATPase) of the myocardium, effectively reducing data acquisition time by up to an order of magnitude. In addition, a new class of 2D FM pulses and multidimensional adiabatic pulses are presented, which can compensate for B1 inhomogeneity through its spatiotemporal properties. These pulses should be valuable for spectroscopic applications at ultra-high-fields.

Enhancing ultra-high CPV passive cooling using least-material finned heat sinks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Micheli, Leonardo, E-mail: lm409@exeter.ac.uk; Mallick, Tapas K., E-mail: T.K.Mallick@exeter.ac.uk; Fernandez, Eduardo F., E-mail: E.Fernandez-Fernandez2@exeter.ac.uk

2015-09-28

Ultra-high concentrating photovoltaic (CPV) systems aim to increase the cost-competiveness of CPV by increasing the concentrations over 2000 suns. In this work, the design of a heat sink for ultra-high concentrating photovoltaic (CPV) applications is presented. For the first time, the least-material approach, widely used in electronics to maximize the thermal dissipation while minimizing the weight of the heat sink, has been applied in CPV. This method has the potential to further decrease the cost of this technology and to keep the multijunction cell within the operative temperature range. The designing procedure is described in the paper and the resultsmore » of a thermal simulation are shown to prove the reliability of the solution. A prediction of the costs is also reported: a cost of 0.151$/W{sub p} is expected for a passive least-material heat sink developed for 4000x applications.« less

Durability and smart condition assessment of ultra-high performance concrete in cold climates.

DOT National Transportation Integrated Search

2016-12-31

The goals of this study were to develop ecological ultra-high performance concrete (UHPC) with local materials and supplementary cementitious materials and to evaluate the long-term performance of UHPC in cold climates using effective mechanical test...

Ultra-Gradient Test Cavity for Testing SRF Wafer Samples

DOE Office of Scientific and Technical Information (OSTI.GOV)

N.J. Pogue, P.M. McIntyre, A.I. Sattarov, C. Reece

2010-11-01

A 1.3 GHz test cavity has been designed to test wafer samples of superconducting materials. This mushroom shaped cavity, operating in TE01 mode, creates a unique distribution of surface fields. The surface magnetic field on the sample wafer is 3.75 times greater than elsewhere on the Niobium cavity surface. This field design is made possible through dielectrically loading the cavity by locating a hemisphere of ultra-pure sapphire just above the sample wafer. The sapphire pulls the fields away from the walls so the maximum field the Nb surface sees is 25% of the surface field on the sample. In thismore » manner, it should be possible to drive the sample wafer well beyond the BCS limit for Niobium while still maintaining a respectable Q. The sapphire's purity must be tested for its loss tangent and dielectric constant to finalize the design of the mushroom test cavity. A sapphire loaded CEBAF cavity has been constructed and tested. The results on the dielectric constant and loss tangent will be presented« less

A fast and sensitive method for the separation of carotenoids using ultra-high performance supercritical fluid chromatography-mass spectrometry.

PubMed

Jumaah, Firas; Plaza, Merichel; Abrahamsson, Victor; Turner, Charlotta; Sandahl, Margareta

2016-08-01

In this study, a rapid and sensitive ultra-high performance supercritical fluid chromatography-mass spectrometry (UHPSFC-MS) method has been developed and partially validated for the separation of carotenoids within less than 6 min. Six columns of orthogonal selectivity were examined, and the best separation was obtained by using a 1-aminoanthracene (1-AA) column. The length of polyene chain as well as the number of hydroxyl groups in the structure of the studied carotenoids determines their differences in the physiochemical properties and thus the separation that is achieved on this column. All of the investigated carotenoids were baseline separated with resolution values greater than 1.5. The effects of gradient program, back pressure, and column temperature were studied with respect to chromatographic properties such as retention and selectivity. Electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) were compared in both positive and negative mode, using both direct infusion and hyphenated with UHPSFC. The ESI in positive mode provided the highest response. The coefficient of determination (R (2)) for all calibration curves were greater than 0.998. Limit of detection (LOD) was in the range of 2.6 and 25.2 ng/mL for α-carotene and astaxanthin, respectively, whereas limit of quantification (LOQ) was in the range of 7.8 and 58.0 ng/mL for α-carotene and astaxanthin, respectively. Repeatability and intermediate precision of the developed UHPSFC-MS method were determined and found to be RSD < 3 % and RSD < 6 %, respectively. The method was applied in order to determine carotenoids in supercritical fluid extracts of microalgae and rosehip. Graphical Abstract Ultra-high performance supercritical fluid chromatography-a rapid separation method for the analysis of carotenoids in rosehip and microalgae samples.

[Screening and confirmation of 24 hormones in cosmetics by ultra high performance liquid chromatography-linear ion trap/orbitrap high resolution mass spectrometry].

PubMed

Li, Zhaoyong; Wang, Fengmei; Niu, Zengyuan; Luo, Xin; Zhang, Gang; Chen, Junhui

2014-05-01

A method of ultra high performance liquid chromatography-linear ion trap/orbitrap high resolution mass spectrometry (UPLC-LTQ/Orbitrap MS) was established to screen and confirm 24 hormones in cosmetics. Various cosmetic samples were extracted with methanol. The extract was loaded onto a Waters ACQUITY UPLC BEH C18 column (50 mm x 2.1 mm, 1.7 microm) using a gradient elution of acetonitrile/water containing 0.1% (v/v) formic acid for the separation. The accurate mass of quasi-molecular ion was acquired by full scanning of electrostatic field orbitrap. The rapid screening was carried out by the accurate mass of quasi-molecular ion. The confirmation analysis for targeted compounds was performed with the retention time and qualitative fragments obtained by data dependent scan mode. Under the optimal conditions, the 24 hormones were routinely detected with mass accuracy error below 3 x 10(-6) (3 ppm), and good linearities were obtained in their respective linear ranges with correlation coefficients higher than 0.99. The LODs (S/N = 3) of the 24 compounds were < or = 10 microg/kg, which can meet the requirements for the actual screening of cosmetic samples. The developed method was applied to screen the hormones in 50 cosmetic samples. The results demonstrate that the method is a useful tool for the rapid screening and identification of the hormones in cosmetics.

Nanoporous membrane device for ultra high heat flux thermal management

NASA Astrophysics Data System (ADS)

Hanks, Daniel F.; Lu, Zhengmao; Sircar, Jay; Salamon, Todd R.; Antao, Dion S.; Bagnall, Kevin R.; Barabadi, Banafsheh; Wang, Evelyn N.

2018-02-01

High power density electronics are severely limited by current thermal management solutions which are unable to dissipate the necessary heat flux while maintaining safe junction temperatures for reliable operation. We designed, fabricated, and experimentally characterized a microfluidic device for ultra-high heat flux dissipation using evaporation from a nanoporous silicon membrane. With 100 nm diameter pores, the membrane can generate high capillary pressure even with low surface tension fluids such as pentane and R245fa. The suspended ultra-thin membrane structure facilitates efficient liquid transport with minimal viscous pressure losses. We fabricated the membrane in silicon using interference lithography and reactive ion etching and then bonded it to a high permeability silicon microchannel array to create a biporous wick which achieves high capillary pressure with enhanced permeability. The back side consisted of a thin film platinum heater and resistive temperature sensors to emulate the heat dissipation in transistors and measure the temperature, respectively. We experimentally characterized the devices in pure vapor-ambient conditions in an environmental chamber. Accordingly, we demonstrated heat fluxes of 665 ± 74 W/cm2 using pentane over an area of 0.172 mm × 10 mm with a temperature rise of 28.5 ± 1.8 K from the heated substrate to ambient vapor. This heat flux, which is normalized by the evaporation area, is the highest reported to date in the pure evaporation regime, that is, without nucleate boiling. The experimental results are in good agreement with a high fidelity model which captures heat conduction in the suspended membrane structure as well as non-equilibrium and sub-continuum effects at the liquid-vapor interface. This work suggests that evaporative membrane-based approaches can be promising towards realizing an efficient, high flux thermal management strategy over large areas for high-performance electronics.

Interpersonal sensitivity and functioning impairment in youth at ultra-high risk for psychosis.

PubMed

Masillo, A; Valmaggia, L R; Saba, R; Brandizzi, M; Lindau, J F; Solfanelli, A; Curto, M; Narilli, F; Telesforo, L; Kotzalidis, G D; Di Pietro, D; D'Alema, M; Girardi, P; Fiori Nastro, P

2016-01-01

A personality trait that often elicits poor and uneasy interpersonal relationships is interpersonal sensitivity. The aim of the present study was to explore the relationship between interpersonal sensitivity and psychosocial functioning in individuals at ultra-high risk for psychosis as compared to help-seeking individuals who screened negative for an ultra-high risk of psychosis. A total sample of 147 adolescents and young adult who were help seeking for emerging mental health problems participated in the study. The sample was divided into two groups: 39 individuals who met criteria for an ultra-high-risk mental state (UHR), and 108 (NS). The whole sample completed the Interpersonal Sensitivity Measure (IPSM) and the Global Functioning: Social and Role Scale (GF:SS; GF:RS). Mediation analysis was used to explore whether attenuated negative symptoms mediated the relationship between interpersonal sensitivity and social functioning. Individuals with UHR state showed higher IPSM scores and lower GF:SS and GF:RS scores than NS participants. A statistically negative significant correlation between two IPSM subscales (Interpersonal Awareness and Timidity) and GF:SS was found in both groups. Our results also suggest that the relationship between the aforementioned aspects of interpersonal sensitivity and social functioning was not mediated by negative prodromal symptoms. This study suggests that some aspects of interpersonal sensitivity were associated with low level of social functioning. Assessing and treating interpersonal sensitivity may be a promising therapeutic target to improve social functioning in young help-seeking individuals.

High-gradient compact linear accelerator

DOEpatents

Carder, B.M.

1998-05-26

A high-gradient linear accelerator comprises a solid-state stack in a vacuum of five sets of disc-shaped Blumlein modules each having a center hole through which particles are sequentially accelerated. Each Blumlein module is a sandwich of two outer conductive plates that bracket an inner conductive plate positioned between two dielectric plates with different thicknesses and dielectric constants. A third dielectric core in the shape of a hollow cylinder forms a casing down the series of center holes, and it has a dielectric constant different that the two dielectric plates that sandwich the inner conductive plate. In operation, all the inner conductive plates are charged to the same DC potential relative to the outer conductive plates. Next, all the inner conductive plates are simultaneously shorted to the outer conductive plates at the outer diameters. The signal short will propagate to the inner diameters at two different rates in each Blumlein module. A faster wave propagates quicker to the third dielectric core across the dielectric plates with the closer spacing and lower dielectric constant. When the faster wave reaches the inner extents of the outer and inner conductive plates, it reflects back outward and reverses the field in that segment of the dielectric core. All the field segments in the dielectric core are then in unipolar agreement until the slower wave finally propagates to the third dielectric core across the dielectric plates with the wider spacing and higher dielectric constant. During such unipolar agreement, particles in the core are accelerated with gradients that exceed twenty megavolts per meter. 10 figs.

High-gradient compact linear accelerator

DOEpatents

Carder, Bruce M.

1998-01-01

A high-gradient linear accelerator comprises a solid-state stack in a vacuum of five sets of disc-shaped Blumlein modules each having a center hole through which particles are sequentially accelerated. Each Blumlein module is a sandwich of two outer conductive plates that bracket an inner conductive plate positioned between two dielectric plates with different thicknesses and dielectric constants. A third dielectric core in the shape of a hollow cylinder forms a casing down the series of center holes, and it has a dielectric constant different that the two dielectric plates that sandwich the inner conductive plate. In operation, all the inner conductive plates are charged to the same DC potential relative to the outer conductive plates. Next, all the inner conductive plates are simultaneously shorted to the outer conductive plates at the outer diameters. The signal short will propagate to the inner diameters at two different rates in each Blumlein module. A faster wave propagates quicker to the third dielectric core across the dielectric plates with the closer spacing and lower dielectric constant. When the faster wave reaches the inner extents of the outer and inner conductive plates, it reflects back outward and reverses the field in that segment of the dielectric core. All the field segments in the dielectric core are then in unipolar agreement until the slower wave finally propagates to the third dielectric core across the dielectric plates with the wider spacing and higher dielectric constant. During such unipolar agreement, particles in the core are accelerated with gradients that exceed twenty megavolts per meter.

Design and evaluation of a single-span bridge using ultra-high performance concrete.

DOT National Transportation Integrated Search

2009-09-01

"Research presented herein describes an application of a newly developed material called Ultra-High Performance Concrete (UHPC) to a : single-span bridge. The two primary objectives of this research were to develop a shear design procedure for possib...

Design and evaluation of a single-span bridge using ultra-high performance concrete.

DOT National Transportation Integrated Search

2009-09-01

Research presented herein describes an application of a newly developed material called Ultra-High Performance Concrete (UHPC) to a : single-span bridge. The two primary objectives of this research were to develop a shear design procedure for possibl...

Characterization of the punching shear capacity of thin ultra-high performance concrete slabs.

DOT National Transportation Integrated Search

2005-01-01

Ultra-high performance concrete (UHPC) is a relatively new type of concrete that exhibits mechanical properties that are far superior to those of conventional concrete and in some cases rival those of steel. The main characteristics that distinguish ...

Case study: dairies utilizing ultra-high stock density grazing in the northeast

USDA-ARS?s Scientific Manuscript database

Ultra-high stock density (UHSD) grazing (also loosely referred to as ‘mob grazing’) has attracted a lot of attention and press in the forage industry. Numerous anecdotal articles can be found in trade magazines that promote the perceived benefits of UHSD grazing. However, there is little credible re...

Rapid extraction and determination of 25 bioactive constituents in Alpinia oxyphylla using microwave extraction with ultra high performance liquid chromatography with tandem mass spectrometry.

PubMed

Sun, Zhi; Kong, Xiangzhen; Zuo, Lihua; Kang, Jian; Hou, Lei; Zhang, Xiaojian

2016-02-01

A novel and rapid microwave extraction and ultra high performance liquid chromatography with tandem mass spectrometry method was developed and validated for the simultaneous determination of 25 bioactive constituents (including two new constituents) in Fructus Alpinia oxyphylla. The optimized conditions of the microwave extraction was a microwave power of 300 W, extraction temperature of 80°C, solvent-to-solid ratio of 30 mL/g and extraction time of 8 min. Separation was achieved on a Waters ACQUITY UPLC(®) HSS C18 column (2.1 mm× 50 mm, 1.8 μm) using gradient elution with a mobile phase consisting of acetonitrile and 1 mM ammonium acetate at a flow rate of 0.2 mL/min. This is the first report of the simultaneous determination of 25 bioactive constituents in Fructus Alpinia oxyphylla by ultra high performance liquid chromatography with tandem mass spectrometry. The method was validated with good linearity, acceptable precision and accuracy. The validated method was successfully applied to determine the contents of 25 bioactive constituents in Fructus Alpinia oxyphylla from different sources and the analysis results were classified by hierarchical cluster analysis, which indicated the effect of different cultivation regions on the contents of constituents. This study provides powerful and practical guidance in the quality control of Alpinia oxyphylla and lays the foundation for further research of Alpinia oxyphylla. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Approaches for springback reduction when forming ultra high-strength sheet metals

NASA Astrophysics Data System (ADS)

Radonjic, R.; Liewald, M.

2016-11-01

Nowadays, the automotive industry is challenged constantly by increasing environmental regulations and the continuous enhancement of standards with regard to passenger's safety (NCAP, Part 1). In order to fulfil the aforementioned requirements, the use of ultra high-strength steels in research and industrial applications is of high interest. When forming such materials, the main problem results from the large amount of springback which occurs after the release of the part. This paper shows the applicability of several approaches for the reduction of springback amount by forming of one hat channel shaped component. A novel approach for springack reduction which is based on forming with an alternating blank draw-in is presented as well. In this investigation an ultra high-strength steel of the grade DP 980 was used. The part's measurements were taken at significant cross-sections in order to provide a qualitative comparison between the reference geometry and the part's released shape. The obtained results were analysed and used in order to quantify the success of particular approaches for springback reduction. When taking a curved hat channel shaped component as an example, the results achieved in the investigations showed that it is possible to reduce part shape deviations significantly when using DP 980 as workpiece material.

Study on Structural and Dielectric Properties of Ultra-Low-Fire Integratable Dielectric Film for High-Frequency and Microwave Application

NASA Astrophysics Data System (ADS)

Qu, Sheng; Zhang, Jihua; Wu, Kaituo; Wang, Lei; Chen, Hongwei

2018-03-01

In this study, ultra-low-fire ceramic composites of Zn2Te3O8-30 wt.%TiTe3O8 (ZTT) were prepared by a solid-state reaction method. Densified at 600°C, the best microwave dielectric properties at 8.5 GHz were measured with the ɛ r , tan δ, Q × f, and τ f as 25.6, 1.5 × 10-4, 56191 GHz and 1.66 ppm/°C, respectively. Thin films of ultra-low-fire ZTT were prepared by a radio-frequency magnetron sputtering method. ZTT films which deposited on Au/NiCr/SiO2/Si (100) substrates at 200°C showed good adhesion. From ultra-low-fire ceramic to ultra-low-fire ZTT thin films, the latter maintained all the good high-frequency dielectric properties of the former: high dielectric constant ( ɛ r ˜ 25) and low dissipation factor (tan δ < 5×10-3), low leakage current density (˜ 10-9 A/cm2) and ultra low processing temperature. These excellent properties of the ultra-low-fire ZTT thin film make it possible to be integrated in MMIC and be applied in the research of GaN and GaAs MOSFET devices.

Collaborative Research on the Ultra High Bypass Ratio Engine Cycle to Reduce Noise, Emissions and Fuel Consumption

NASA Technical Reports Server (NTRS)

Hughes, Christopher

2008-01-01

A pictorial history of NASA development of advanced engine technologies for reducing environmental emissions and increasing performance from the 1970s to present is presented. The goals of the Subsonic Fixed Wing Program portion of the NASA Fundamental Aeronautics Program are addressed, along with the areas of investigation currently being pursued by the Ultra High Bypass Partnership Element of the Subsonic Fixed Wing Program to meet the goals. Ultra High Bypass cycle research collaboration successes with Pratt & Whitney are presented.

Ultra High Strain Rate Nanoindentation Testing.

PubMed

Sudharshan Phani, Pardhasaradhi; Oliver, Warren Carl

2017-06-17

Strain rate dependence of indentation hardness has been widely used to study time-dependent plasticity. However, the currently available techniques limit the range of strain rates that can be achieved during indentation testing. Recent advances in electronics have enabled nanomechanical measurements with very low noise levels (sub nanometer) at fast time constants (20 µs) and high data acquisition rates (100 KHz). These capabilities open the doors for a wide range of ultra-fast nanomechanical testing, for instance, indentation testing at very high strain rates. With an accurate dynamic model and an instrument with fast time constants, step load tests can be performed which enable access to indentation strain rates approaching ballistic levels (i.e., 4000 1/s). A novel indentation based testing technique involving a combination of step load and constant load and hold tests that enables measurement of strain rate dependence of hardness spanning over seven orders of magnitude in strain rate is presented. A simple analysis is used to calculate the equivalent uniaxial response from indentation data and compared to the conventional uniaxial data for commercial purity aluminum. Excellent agreement is found between the indentation and uniaxial data over several orders of magnitude of strain rate.

Demonstration of passive plasma lensing of a laser wakefield accelerated electron bunch

DOE PAGES

Kuschel, S.; Hollatz, D.; Heinemann, T.; ...

2016-07-20

We report on the first demonstration of passive all-optical plasma lensing using a two-stage setup. An intense femtosecond laser accelerates electrons in a laser wakefield accelerator (LWFA) to 100 MeV over millimeter length scales. By adding a second gas target behind the initial LWFA stage we introduce a robust and independently tunable plasma lens. We observe a density dependent reduction of the LWFA electron beam divergence from an initial value of 2.3 mrad, down to 1.4 mrad (rms), when the plasma lens is in operation. Such a plasma lens provides a simple and compact approach for divergence reduction well matchedmore » to the mm-scale length of the LWFA accelerator. The focusing forces are provided solely by the plasma and driven by the bunch itself only, making this a highly useful and conceptually new approach to electron beam focusing. Possible applications of this lens are not limited to laser plasma accelerators. Since no active driver is needed the passive plasma lens is also suited for high repetition rate focusing of electron bunches. As a result, its understanding is also required for modeling the evolution of the driving particle bunch in particle driven wake field acceleration.« less

The suitability of using dissolved gases to determine groundwater discharge to high gradient streams

USGS Publications Warehouse

Gleeson, Tom; Manning, Andrew H.; Popp, Andrea; Zane, Mathew; Clark, Jordan F.

2018-01-01

Determining groundwater discharge to streams using dissolved gases is known to be useful over a wide range of streamflow rates but the suitability of dissolved gas methods to determine discharge rates in high gradient mountain streams has not been sufficiently tested, even though headwater streams are critical as ecological habitats and water resources. The aim of this study is to test the suitability of using dissolved gases to determine groundwater discharge rates to high gradient streams by field experiments in a well-characterized, high gradient mountain stream and a literature review. At a reach scale (550 m) we combined stream and groundwater radon activity measurements with an in-stream SF6 tracer test. By means of numerical modeling we determined gas exchange velocities and derived very low groundwater discharge rates (∼15% of streamflow). These groundwater discharge rates are below the uncertainty range of physical streamflow measurements and consistent with temperature, specific conductance and streamflow measured at multiple locations along the reach. At a watershed-scale (4 km), we measured CFC-12 and δ18O concentrations and determined gas exchange velocities and groundwater discharge rates with the same numerical model. The groundwater discharge rates along the 4 km stream reach were highly variable, but were consistent with the values derived in the detailed study reach. Additionally, we synthesized literature values of gas exchange velocities for different stream gradients which show an empirical relationship that will be valuable in planning future dissolved gas studies on streams with various gradients. In sum, we show that multiple dissolved gas tracers can be used to determine groundwater discharge to high gradient mountain streams from reach to watershed scales.

The suitability of using dissolved gases to determine groundwater discharge to high gradient streams

NASA Astrophysics Data System (ADS)

Gleeson, Tom; Manning, Andrew H.; Popp, Andrea; Zane, Matthew; Clark, Jordan F.

2018-02-01

Determining groundwater discharge to streams using dissolved gases is known to be useful over a wide range of streamflow rates but the suitability of dissolved gas methods to determine discharge rates in high gradient mountain streams has not been sufficiently tested, even though headwater streams are critical as ecological habitats and water resources. The aim of this study is to test the suitability of using dissolved gases to determine groundwater discharge rates to high gradient streams by field experiments in a well-characterized, high gradient mountain stream and a literature review. At a reach scale (550 m) we combined stream and groundwater radon activity measurements with an in-stream SF6 tracer test. By means of numerical modeling we determined gas exchange velocities and derived very low groundwater discharge rates (∼15% of streamflow). These groundwater discharge rates are below the uncertainty range of physical streamflow measurements and consistent with temperature, specific conductance and streamflow measured at multiple locations along the reach. At a watershed-scale (4 km), we measured CFC-12 and δ18O concentrations and determined gas exchange velocities and groundwater discharge rates with the same numerical model. The groundwater discharge rates along the 4 km stream reach were highly variable, but were consistent with the values derived in the detailed study reach. Additionally, we synthesized literature values of gas exchange velocities for different stream gradients which show an empirical relationship that will be valuable in planning future dissolved gas studies on streams with various gradients. In sum, we show that multiple dissolved gas tracers can be used to determine groundwater discharge to high gradient mountain streams from reach to watershed scales.

In vivo imaging of cortical pathology in multiple sclerosis using ultra-high field MRI

PubMed Central

Mainero, C; Benner, T; Radding, A; van der Kouwe, A; Jensen, R; Rosen, B R.; Kinkel, R P.

2009-01-01

Objective: We used ultra-high field MRI to visualize cortical lesion types described by neuropathology in 16 patients with multiple sclerosis (MS) compared with 8 age-matched controls; to characterize the contrast properties of cortical lesions including T2*, T2, T1, and phase images; and to investigate the relationship between cortical lesion types and clinical data. Methods: We collected, on a 7-T scanner, 2-dimensional fast low-angle shot (FLASH)-T2*-weighted spoiled gradient-echo, T2-weighted turbo spin-echo (TSE) images (0.33 × 033 × 1 mm3), and a 3-dimensional magnetization-prepared rapid gradient echo. Results: Overall, 199 cortical lesions were detected in patients on both FLASH-T2* and T2-TSE scans. Seven-tesla MRI allowed for characterization of cortical plaques into type I (leukocortical), type II (intracortical), and type III/IV (subpial extending partly or completely through the cortical width) lesions as described histopathologically. Types III and IV were the most frequent type of cortical plaques (50.2%), followed by type I (36.2%) and type II (13.6%) lesions. Each lesion type was more frequent in secondary progressive than in relapsing–remitting MS. This difference, however, was significant only for type III/IV lesions. T2*-weighted images showed the highest, while phase images showed the lowest, contrast-to-noise ratio for all cortical lesion types. In patients, the number of type III/IV lesions was associated with greater disability (p < 0.02 by Spearman test) and older age (p < 0.04 by Spearman test). Conclusions: Seven-tesla MRI detected different histologic cortical lesion types in our small multiple sclerosis (MS) sample, suggesting, if validated in a larger population, that it may prove a valuable tool to assess the contribution of cortical MS pathology to clinical disability. GLOSSARY ANOVA = analysis of variance; BN = background noise; CNR = contrast-to-noise ratio; DIR = double-inversion recovery; EDSS = Expanded Disability Status

Qualitative and Quantitative Analysis of Volatile Components of Zhengtian Pills Using Gas Chromatography Mass Spectrometry and Ultra-High Performance Liquid Chromatography.

PubMed

Liu, Cui-Ting; Zhang, Min; Yan, Ping; Liu, Hai-Chan; Liu, Xing-Yun; Zhan, Ruo-Ting

2016-01-01

Zhengtian pills (ZTPs) are traditional Chinese medicine (TCM) which have been commonly used to treat headaches. Volatile components of ZTPs extracted by ethyl acetate with an ultrasonic method were analyzed by gas chromatography mass spectrometry (GC-MS). Twenty-two components were identified, accounting for 78.884% of the total components of volatile oil. The three main volatile components including protocatechuic acid, ferulic acid, and ligustilide were simultaneously determined using ultra-high performance liquid chromatography coupled with diode array detection (UHPLC-DAD). Baseline separation was achieved on an XB-C18 column with linear gradient elution of methanol-0.2% acetic acid aqueous solution. The UHPLC-DAD method provided good linearity (R (2) ≥ 0.9992), precision (RSD < 3%), accuracy (100.68-102.69%), and robustness. The UHPLC-DAD/GC-MS method was successfully utilized to analyze volatile components, protocatechuic acid, ferulic acid, and ligustilide, in 13 batches of ZTPs, which is suitable for discrimination and quality assessment of ZTPs.

Study of ultra-low emittance design for Spear3 using longitudinal gradient dipole

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, M. -H.; Huang, X.; Safranek, J.

2015-09-24

Since its 2003 construction, the SPEAR3 synchrotron light source at SLAC has continuously improved its performance by raising beam current, top-off injection, and smaller emittance. This makes SPEAR3 one of the most productive light sources in the world. Now to further enhance the performance of SPEAR3, we are looking into the possibility of converting SPEAR3 to an ultra-low emittance storage ring within its site constraint.

3-D phononic crystals with ultra-wide band gaps

PubMed Central

Lu, Yan; Yang, Yang; Guest, James K.; Srivastava, Ankit

2017-01-01

In this paper gradient based topology optimization (TO) is used to discover 3-D phononic structures that exhibit ultra-wide normalized all-angle all-mode band gaps. The challenging computational task of repeated 3-D phononic band-structure evaluations is accomplished by a combination of a fast mixed variational eigenvalue solver and distributed Graphic Processing Unit (GPU) parallel computations. The TO algorithm utilizes the material distribution-based approach and a gradient-based optimizer. The design sensitivity for the mixed variational eigenvalue problem is derived using the adjoint method and is implemented through highly efficient vectorization techniques. We present optimized results for two-material simple cubic (SC), body centered cubic (BCC), and face centered cubic (FCC) crystal structures and show that in each of these cases different initial designs converge to single inclusion network topologies within their corresponding primitive cells. The optimized results show that large phononic stop bands for bulk wave propagation can be achieved at lower than close packed spherical configurations leading to lighter unit cells. For tungsten carbide - epoxy crystals we identify all angle all mode normalized stop bands exceeding 100%, which is larger than what is possible with only spherical inclusions. PMID:28233812

3-D phononic crystals with ultra-wide band gaps.

PubMed

Lu, Yan; Yang, Yang; Guest, James K; Srivastava, Ankit

2017-02-24

In this paper gradient based topology optimization (TO) is used to discover 3-D phononic structures that exhibit ultra-wide normalized all-angle all-mode band gaps. The challenging computational task of repeated 3-D phononic band-structure evaluations is accomplished by a combination of a fast mixed variational eigenvalue solver and distributed Graphic Processing Unit (GPU) parallel computations. The TO algorithm utilizes the material distribution-based approach and a gradient-based optimizer. The design sensitivity for the mixed variational eigenvalue problem is derived using the adjoint method and is implemented through highly efficient vectorization techniques. We present optimized results for two-material simple cubic (SC), body centered cubic (BCC), and face centered cubic (FCC) crystal structures and show that in each of these cases different initial designs converge to single inclusion network topologies within their corresponding primitive cells. The optimized results show that large phononic stop bands for bulk wave propagation can be achieved at lower than close packed spherical configurations leading to lighter unit cells. For tungsten carbide - epoxy crystals we identify all angle all mode normalized stop bands exceeding 100%, which is larger than what is possible with only spherical inclusions.

Measuring the Non-Line-of-Sight Ultra-High-Frequency Channel in Mountainous Terrain: A Spread-Spectrum, Portable Channel Sounder

DTIC Science & Technology

2018-03-01

ER D C/ CR RE L TR -1 8- 3 ERDC 6.1 Basic Research Measuring the Non-Line-of-Sight Ultra- High - Frequency Channel in Mountainous Terrain... High - Frequency Channel in Mountainous Terrain A Spread-Spectrum, Portable Channel Sounder Samuel S. Streeter and Daniel J. Breton U.S. Army...spread-spectrum, portable channel sounder specifically designed to meas- ure the non-line-of-sight, ultra- high -frequency channel in mountainous terrain

World's first telepathology experiments employing WINDS ultra-high-speed internet satellite, nicknamed “KIZUNA”

PubMed Central

Sawai, Takashi; Uzuki, Miwa; Miura, Yasuhiro; Kamataki, Akihisa; Matsumura, Tsubasa; Saito, Kenji; Kurose, Akira; Osamura, Yoshiyuki R.; Yoshimi, Naoki; Kanno, Hiroyuki; Moriya, Takuya; Ishida, Yoji; Satoh, Yohichi; Nakao, Masahiro; Ogawa, Emiko; Matsuo, Satoshi; Kasai, Hiroyuki; Kumagai, Kazuhiro; Motoda, Toshihiro; Hopson, Nathan

2013-01-01

Background: Recent advances in information technology have allowed the development of a telepathology system involving high-speed transfer of high-volume histological figures via fiber optic landlines. However, at present there are geographical limits to landlines. The Japan Aerospace Exploration Agency (JAXA) has developed the “Kizuna” ultra-high speed internet satellite and has pursued its various applications. In this study we experimented with telepathology in collaboration with JAXA using Kizuna. To measure the functionality of the Wideband InterNet working engineering test and Demonstration Satellite (WINDS) ultra-high speed internet satellite in remote pathological diagnosis and consultation, we examined the adequate data transfer speed and stability to conduct telepathology (both diagnosis and conferencing) with functionality, and ease similar or equal to telepathology using fiber-optic landlines. Materials and Methods: We performed experiments for 2 years. In year 1, we tested the usability of the WINDS for telepathology with real-time video and virtual slide systems. These are state-of-the-art technologies requiring massive volumes of data transfer. In year 2, we tested the usability of the WINDS for three-way teleconferencing with virtual slides. Facilities in Iwate (northern Japan), Tokyo, and Okinawa were connected via the WINDS and voice conferenced while remotely examining and manipulating virtual slides. Results: Network function parameters measured using ping and Iperf were within acceptable limits. However; stage movement, zoom, and conversation suffered a lag of approximately 0.8 s when using real-time video, and a delay of 60-90 s was experienced when accessing the first virtual slide in a session. No significant lag or inconvenience was experienced during diagnosis and conferencing, and the results were satisfactory. Our hypothesis was confirmed for both remote diagnosis using real-time video and virtual slide systems, and also for

Ultra-high-pressure liquid chromatography-tandem mass spectrometry for the analysis of six resorcylic acid lactones in bovine milk.

PubMed

Xia, Xi; Li, Xiaowei; Ding, Shuangyang; Zhang, Suxia; Jiang, Haiyang; Li, Jiancheng; Shen, Jianzhong

2009-03-20

This work reports a rapid, reliable and sensitive multi-residue method for the simultaneous determination of six resorcylic acid lactones in bovine milk by ultra-high-pressure liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). The resorcylic acid lactones were extracted, purified, and concentrated from milk samples in one step using a solid-phase extraction (SPE) cartridge that contained a polymeric mixed-mode anion-exchange sorbent. The analysis was performed on a Waters Acquity BEH C(18) column utilizing a gradient elution profile. Each LC run was completed in 3.5 min. The analytes were detected by multiple reaction monitoring (MRM) using electrospray ionization (ESI) negative mode. Mean recoveries from fortified samples ranged from 92.6% to 112.5%, with relative standard deviations lower than 11.4%. Using 5 mL bovine milk, the limits of detection and quantification for resorcylic acid lactones were in the ranges of 0.01-0.05 and 0.05-0.2 microg/L, respectively. The application of this newly developed method was demonstrated by analyzing bovine milk samples from markets.

Development of ultra-high temperature material characterization capabilities using digital image correlation analysis

NASA Astrophysics Data System (ADS)

Cline, Julia Elaine

2011-12-01

Ultra-high temperature deformation measurements are required to characterize the thermo-mechanical response of material systems for thermal protection systems for aerospace applications. The use of conventional surface-contacting strain measurement techniques is not practical in elevated temperature conditions. Technological advancements in digital imaging provide impetus to measure full-field displacement and determine strain fields with sub-pixel accuracy by image processing. In this work, an Instron electromechanical axial testing machine with a custom-designed high temperature gripping mechanism is used to apply quasi-static tensile loads to graphite specimens heated to 2000°F (1093°C). Specimen heating via Joule effect is achieved and maintained with a custom-designed temperature control system. Images are captured at monotonically increasing load levels throughout the test duration using an 18 megapixel Canon EOS Rebel T2i digital camera with a modified Schneider Kreutznach telecentric lens and a combination of blue light illumination and narrow band-pass filter system. Images are processed using an open-source Matlab-based digital image correlation (DIC) code. Validation of source code is performed using Mathematica generated images with specified known displacement fields in order to gain confidence in accurate software tracking capabilities. Room temperature results are compared with extensometer readings. Ultra-high temperature strain measurements for graphite are obtained at low load levels, demonstrating the potential for non-contacting digital image correlation techniques to accurately determine full-field strain measurements at ultra-high temperature. Recommendations are given to improve the experimental set-up to achieve displacement field measurements accurate to 1/10 pixel and strain field accuracy of less than 2%.

Fabrication of high gradient insulators by stack compression

DOEpatents

Harris, John Richardson; Sanders, Dave; Hawkins, Steven Anthony; Norona, Marcelo

2014-04-29

Individual layers of a high gradient insulator (HGI) are first pre-cut to their final dimensions. The pre-cut layers are then stacked to form an assembly that is subsequently pressed into an HGI unit with the desired dimension. The individual layers are stacked, and alignment is maintained, using a sacrificial alignment tube that is removed after the stack is hot pressed. The HGI's are used as high voltage vacuum insulators in energy storage and transmission structures or devices, e.g. in particle accelerators and pulsed power systems.

What predicts performance in ultra-triathlon races? – a comparison between Ironman distance triathlon and ultra-triathlon

PubMed Central

Knechtle, Beat; Zingg, Matthias Alexander; Rosemann, Thomas; Stiefel, Michael; Rüst, Christoph Alexander

2015-01-01

Objective This narrative review summarizes recent intentions to find potential predictor variables for ultra-triathlon race performance (ie, triathlon races longer than the Ironman distance covering 3.8 km swimming, 180 km cycling, and 42.195 km running). Results from studies on ultra-triathletes were compared to results on studies on Ironman triathletes. Methods A literature search was performed in PubMed using the terms “ultra”, “triathlon”, and “performance” for the aspects of “ultra-triathlon”, and “Ironman”, “triathlon”, and “performance” for the aspects of “Ironman triathlon”. All resulting papers were searched for related citations. Results for ultra-triathlons were compared to results for Ironman-distance triathlons to find potential differences. Results Athletes competing in Ironman and ultra-triathlon differed in anthropometric and training characteristics, where both Ironmen and ultra-triathletes profited from low body fat, but ultra-triathletes relied more on training volume, whereas speed during training was related to Ironman race time. The most important predictive variables for a fast race time in an ultra-triathlon from Double Iron (ie, 7.6 km swimming, 360 km cycling, and 84.4 km running) and longer were male sex, low body fat, age of 35–40 years, extensive previous experience, a fast time in cycling and running but not in swimming, and origins in Central Europe. Conclusion Any athlete intending to compete in an ultra-triathlon should be aware that low body fat and high training volumes are highly predictive for overall race time. Little is known about the physiological characteristics of these athletes and about female ultra-triathletes. Future studies need to investigate anthropometric and training characteristics of female ultra-triathletes and what motivates women to compete in these races. Future studies need to correlate physiological characteristics such as maximum oxygen uptake (VO2max) with ultra

Activation of the E1 Ultra High Pressure Propulsion Test Facility at Stennis Space Center

NASA Technical Reports Server (NTRS)

Messer, Bradley; Messer, Elisabeth; Sewell, Dale; Sass, Jared; Lott, Jeff; Dutreix, Lionel, III

2001-01-01

After a decade of construction and a year of activation the El Ultra High Pressure Propulsion Test Facility at NASA's Stennis Space Center is fully operational. The El UHP Propulsion Test Facility is a multi-cell, multi-purpose component and engine test facility . The facility is capable of delivering cryogenic propellants at low, high, and ultra high pressures with flow rates ranging from a few pounds per second up to two thousand pounds per second. Facility activation is defined as a series of tasks required to transition between completion of construction and facility operational readiness. Activating the El UHP Propulsion Test Facility involved independent system checkouts, propellant system leak checks, fluid and gas sampling, gaseous system blow downs, pressurization and vent system checkouts, valve stability testing, valve tuning cryogenic cold flows, and functional readiness tests.

Ultra-High Density Single Nanometer-Scale Anodic Alumina Nanofibers Fabricated by Pyrophosphoric Acid Anodizing

NASA Astrophysics Data System (ADS)

Kikuchi, Tatsuya; Nishinaga, Osamu; Nakajima, Daiki; Kawashima, Jun; Natsui, Shungo; Sakaguchi, Norihito; Suzuki, Ryosuke O.

2014-12-01

Anodic oxide fabricated by anodizing has been widely used for nanostructural engineering, but the nanomorphology is limited to only two oxides: anodic barrier and porous oxides. Therefore, the discovery of an additional anodic oxide with a unique nanofeature would expand the applicability of anodizing. Here we demonstrate the fabrication of a third-generation anodic oxide, specifically, anodic alumina nanofibers, by anodizing in a new electrolyte, pyrophosphoric acid. Ultra-high density single nanometer-scale anodic alumina nanofibers (1010 nanofibers/cm2) consisting of an amorphous, pure aluminum oxide were successfully fabricated via pyrophosphoric acid anodizing. The nanomorphologies of the anodic nanofibers can be controlled by the electrochemical conditions. Anodic tungsten oxide nanofibers can also be fabricated by pyrophosphoric acid anodizing. The aluminum surface covered by the anodic alumina nanofibers exhibited ultra-fast superhydrophilic behavior, with a contact angle of less than 1°, within 1 second. Such ultra-narrow nanofibers can be used for various nanoapplications including catalysts, wettability control, and electronic devices.

Ultra-High Density Single Nanometer-Scale Anodic Alumina Nanofibers Fabricated by Pyrophosphoric Acid Anodizing

PubMed Central

Kikuchi, Tatsuya; Nishinaga, Osamu; Nakajima, Daiki; Kawashima, Jun; Natsui, Shungo; Sakaguchi, Norihito; Suzuki, Ryosuke O.

2014-01-01

Anodic oxide fabricated by anodizing has been widely used for nanostructural engineering, but the nanomorphology is limited to only two oxides: anodic barrier and porous oxides. Therefore, the discovery of an additional anodic oxide with a unique nanofeature would expand the applicability of anodizing. Here we demonstrate the fabrication of a third-generation anodic oxide, specifically, anodic alumina nanofibers, by anodizing in a new electrolyte, pyrophosphoric acid. Ultra-high density single nanometer-scale anodic alumina nanofibers (1010 nanofibers/cm2) consisting of an amorphous, pure aluminum oxide were successfully fabricated via pyrophosphoric acid anodizing. The nanomorphologies of the anodic nanofibers can be controlled by the electrochemical conditions. Anodic tungsten oxide nanofibers can also be fabricated by pyrophosphoric acid anodizing. The aluminum surface covered by the anodic alumina nanofibers exhibited ultra-fast superhydrophilic behavior, with a contact angle of less than 1°, within 1 second. Such ultra-narrow nanofibers can be used for various nanoapplications including catalysts, wettability control, and electronic devices. PMID:25491282

Ultra-high Q terahertz whispering-gallery modes in a silicon resonator

NASA Astrophysics Data System (ADS)

Vogt, Dominik Walter; Leonhardt, Rainer

2018-05-01

We report on the first experimental demonstration of terahertz (THz) whispering-gallery modes (WGMs) with an ultra-high quality factor of 1.5 × 104 at 0.62 THz. The WGMs are observed in a high resistivity float zone silicon spherical resonator coupled to a sub-wavelength silica waveguide. A detailed analysis of the coherent continuous wave THz spectroscopy measurements combined with a numerical model based on Mie-Debye-Aden-Kerker theory allows us to unambiguously identify the observed higher order radial THz WGMs.

Ultra-high vacuum surface analysis study of rhodopsin incorporation into supported lipid bilayers.

PubMed

Michel, Roger; Subramaniam, Varuni; McArthur, Sally L; Bondurant, Bruce; D'Ambruoso, Gemma D; Hall, Henry K; Brown, Michael F; Ross, Eric E; Saavedra, S Scott; Castner, David G

2008-05-06

Planar supported lipid bilayers that are stable under ambient atmospheric and ultra-high-vacuum conditions were prepared by cross-linking polymerization of bis-sorbylphosphatidylcholine (bis-SorbPC). X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were employed to investigate bilayers that were cross-linked using either redox-initiated radical polymerization or ultraviolet photopolymerization. The redox method yields a more structurally intact bilayer; however, the UV method is more compatible with incorporation of transmembrane proteins. UV polymerization was therefore used to prepare cross-linked bilayers with incorporated bovine rhodopsin, a light-activated, G-protein-coupled receptor (GPCR). A previous study (Subramaniam, V.; Alves, I. D.; Salgado, G. F. J.; Lau, P. W.; Wysocki, R. J.; Salamon, Z.; Tollin, G.; Hruby, V. J.; Brown, M. F.; Saavedra, S. S. J. Am. Chem. Soc. 2005, 127, 5320-5321) showed that rhodopsin retains photoactivity after incorporation into UV-polymerized bis-SorbPC, but did not address how the protein is associated with the bilayer. In this study, we show that rhodopsin is retained in supported bilayers of poly(bis-SorbPC) under ultra-high-vacuum conditions, on the basis of the increase in the XPS nitrogen concentration and the presence of characteristic amino acid peaks in the ToF-SIMS data. Angle-resolved XPS data show that the protein is inserted into the bilayer, rather than adsorbed on the bilayer surface. This is the first study to demonstrate the use of ultra-high-vacuum techniques for structural studies of supported proteolipid bilayers.

Mechanisms of high-gradient microwave breakdown on metal surfaces in high power microwave source

NASA Astrophysics Data System (ADS)

Xie, Jialing; Chen, Changhua; Chang, Chao; Wu, Cheng; Huo, Yankun

2017-12-01

A breakdown cavity was designed to study the high-gradient microwave breakdown on a metal surface. The breakdown cavity can be distinguished into an electron emission boundary and a bombardment boundary as there is an evident difference in amplitude of the electric field between the two planes in the cavity. Breakdown tracks on the cavity were studied with an electron scanning microscope. The tracks on the electron emission boundary with the higher electric field were eroded; a component analysis indicates that these tracks contain an emission boundary material. On the bombardment boundary with a lower electric field, two kinds of tracks exist: an erosion track containing a bombardment boundary material and a sputtered track containing an emission boundary material. From these tracks, the mechanisms of high-gradient microwave breakdown on a metal surface have been analyzed.

Effects of high-gradient magnetic fields on living cell machinery

NASA Astrophysics Data System (ADS)

Zablotskii, V.; Lunov, O.; Kubinova, S.; Polyakova, T.; Sykova, E.; Dejneka, A.

2016-12-01

A general interest in biomagnetic effects is related to fundamental studies of the influence of magnetic fields on living objects on the cellular and whole organism levels. Emerging technologies offer new directions for the use of high-gradient magnetic fields to control cell machinery and to understand the intracellular biological processes of the emerging field of nanomedicine. In this review we aim at highlighting recent advances made in identifying fundamental mechanisms by which magnetic gradient forces act on cell fate specification and cell differentiation. The review also provides an analysis of the currently available magnetic systems capable of generating magnetic fields with spatial gradients of up to 10 MT m-1, with the focus on their suitability for use in cell therapy. Relationships between experimental factors and underlying biophysical mechanisms and assumptions that would ultimately lead to a deeper understanding of cell machinery and the development of more predictive models for the evaluation of the effects of magnetic fields on cells, tissue and organisms are comprehensively discussed.

Ultra-high performance concrete : a state-of-the-art report for the bridge community.

DOT National Transportation Integrated Search

2013-06-01

"The term Ultra-High Performance Concrete (UHPC) refers to a relatively new class of advanced cementitious : composite materials whose mechanical and durability properties far surpass those of conventional concrete. This : class of concrete has been ...

Ultra High Definition Video from the International Space Station (Reel 1)

NASA Image and Video Library

2015-06-15

The view of life in space is getting a major boost with the introduction of 4K Ultra High-Definition (UHD) video, providing an unprecedented look at what it's like to live and work aboard the International Space Station. This important new capability will allow researchers to acquire high resolution - high frame rate video to provide new insight into the vast array of experiments taking place every day. It will also bestow the most breathtaking views of planet Earth and space station activities ever acquired for consumption by those still dreaming of making the trip to outer space.

"Ultra High Dilution 1994" revisited 2015--the state of follow-up research.

PubMed

Endler, P Christian; Schulte, Jurgen; Stock-Schroeer, Beate; Stephen, Saundra

2015-10-01

The "Ultra High Dilution 1994" project was an endeavour to take stock of the findings and theories on homeopathic extreme dilutions that were under research at the time in areas of biology, biophysics, physics and medicine. The project finally materialized into an anthology assembling contributions of leading scientists in the field. Over the following two decades, it became widely quoted within the homeopathic community and also known in other research communities. The aim of the present project was to re-visit and review the 1994 studies from the perspective of 2015. The original authors from 1994 or close laboratory colleagues were asked to contribute papers covering their research efforts and learnings in the period from 1994 up to 2015. These contributions were edited and cross-referenced, and a selection of further contributions was added. About a dozen contributions reported on follow-up experiments and studies, including further developments in theory. Only few of the models that had seemed promising in 1994 had not been followed up later. Most models presented in the original publication had meanwhile been submitted to intra-laboratory, multicentre or independent scrutiny. The results of the follow-up research seemed to have rewarded the efforts. Furthermore, contributions were provided on new models that had been inspired by the original ones or that may be candidates for further in-depth ultra high dilution (UHD) research. The project "Ultra High Dilution 1994 revisited 2015" is the latest output of what might be considered the "buena vista social club" of homeopathy research. However, it presents new developments and results of the older, established experimental models as well as a general survey of the state of UHD research. Copyright © 2015 The Faculty of Homeopathy. Published by Elsevier Ltd. All rights reserved.

UltraNet Target Parameters. Chapter 1

NASA Technical Reports Server (NTRS)

Kislitzin, Katherine T.; Blaylock, Bruce T. (Technical Monitor)

1992-01-01

The UltraNet is a high speed network capable of rates up to one gigabit per second. It is a hub based network with four optical fiber links connecting each hub. Each link can carry up to 256 megabits of data, and the hub backplane is capable of one gigabit aggregate throughput. Host connections to the hub may be fiber, coax, or channel based. Bus based machines have adapter boards that connect to transceivers in the hub, while channel based machines use a personality module in the hub. One way that the UltraNet achieves its high transfer rates is by off-loading the protocol processing from the hosts to special purpose protocol engines in the UltraNet hubs. In addition, every hub has a PC connected to it by StarLAN for network management purposes. Although there is hub resident and PC resident UltraNet software, this document treats only the host resident UltraNet software.

Coupling temporal and spatial gradient information in high-density unstructured Lagrangian measurements

NASA Astrophysics Data System (ADS)

Wong, Jaime G.; Rosi, Giuseppe A.; Rouhi, Amirreza; Rival, David E.

2017-10-01

Particle tracking velocimetry (PTV) produces high-quality temporal information that is often neglected when computing spatial gradients. A method is presented here to utilize this temporal information in order to improve the estimation of spatial gradients for spatially unstructured Lagrangian data sets. Starting with an initial guess, this method penalizes any gradient estimate where the substantial derivative of vorticity along a pathline is not equal to the local vortex stretching/tilting. Furthermore, given an initial guess, this method can proceed on an individual pathline without any further reference to neighbouring pathlines. The equivalence of the substantial derivative and vortex stretching/tilting is based on the vorticity transport equation, where viscous diffusion is neglected. By minimizing the residual of the vorticity-transport equation, the proposed method is first tested to reduce error and noise on a synthetic Taylor-Green vortex field dissipating in time. Furthermore, when the proposed method is applied to high-density experimental data collected with `Shake-the-Box' PTV, noise within the spatial gradients is significantly reduced. In the particular test case investigated here of an accelerating circular plate captured during a single run, the method acts to delineate the shear layer and vortex core, as well as resolve the Kelvin-Helmholtz instabilities, which were previously unidentifiable without the use of ensemble averaging. The proposed method shows promise for improving PTV measurements that require robust spatial gradients while retaining the unstructured Lagrangian perspective.

Tailored electron bunches with smooth current profiles for enhanced transformer ratios in beam-driven acceleration

DOE PAGES

Lemery, F.; Piot, P.

2015-08-03

Collinear high-gradient O(GV/m) beam-driven wakefield methods for charged-particle acceleration could be critical to the realization of compact, cost-efficient, accelerators, e.g., in support of TeV-scale lepton colliders or multiple-user free-electron laser facilities. To make these options viable, the high accelerating fields need to be complemented with large transformer ratios >2, a parameter characterizing the efficiency of the energy transfer between a wakefield-exciting “drive” bunch to an accelerated “witness” bunch. While several potential current distributions have been discussed, their practical realization appears challenging due to their often discontinuous nature. In this paper we propose several alternative continuously differentiable (smooth) current profiles whichmore » support enhanced transformer ratios. We especially demonstrate that one of the devised shapes can be implemented in a photo-emission electron source by properly shaping the photocathode-laser pulse. We finally discuss a possible superconducting linear-accelerator concept that could produce shaped drive bunches at high-repetition rates to drive a dielectric-wakefield accelerator with accelerating fields on the order of ~60 MV/m and a transformer ratio ~5 consistent with a recently proposed multiuser free-electron laser facility.« less

Tailored electron bunches with smooth current profiles for enhanced transformer ratios in beam-driven acceleration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lemery, F.; Piot, P.

Collinear high-gradient O(GV/m) beam-driven wakefield methods for charged-particle acceleration could be critical to the realization of compact, cost-efficient, accelerators, e.g., in support of TeV-scale lepton colliders or multiple-user free-electron laser facilities. To make these options viable, the high accelerating fields need to be complemented with large transformer ratios >2, a parameter characterizing the efficiency of the energy transfer between a wakefield-exciting “drive” bunch to an accelerated “witness” bunch. While several potential current distributions have been discussed, their practical realization appears challenging due to their often discontinuous nature. In this paper we propose several alternative continuously differentiable (smooth) current profiles whichmore » support enhanced transformer ratios. We especially demonstrate that one of the devised shapes can be implemented in a photo-emission electron source by properly shaping the photocathode-laser pulse. We finally discuss a possible superconducting linear-accelerator concept that could produce shaped drive bunches at high-repetition rates to drive a dielectric-wakefield accelerator with accelerating fields on the order of ~60 MV/m and a transformer ratio ~5 consistent with a recently proposed multiuser free-electron laser facility.« less

Fatigue Properties of the Ultra-High Strength Steel TM210A

PubMed Central

Kang, Xia; Zhao, Gui-ping

2017-01-01

This paper presents the results of an experiment to investigate the high cycle fatigue properties of the ultra-high strength steel TM210A. A constant amplitude rotating bending fatigue experiment was performed at room temperature at stress ratio R = −1. In order to evaluate the notch effect, the fatigue experiment was carried out upon two sets of specimens, smooth and notched, respectively. In the experiment, the rotating bending fatigue life was tested using the group method, and the rotating bending fatigue limit was tested using the staircase method at 1 × 107 cycles. A double weighted least square method was then used to fit the stress-life (S–N) curve. The S–N curves of the two sets of specimens were obtained and the morphologies of the fractures of the two sets of specimens were observed with scanning electron microscopy (SEM). The results showed that the fatigue limit of the smooth specimen for rotating bending fatigue was 615 MPa; the ratio of the fatigue limit to tensile strength was 0.29, and the cracks initiated at the surface of the smooth specimen; while the fatigue limit of the notched specimen for rotating bending fatigue was 363 MPa, and the cracks initiated at the edge of the notch. The fatigue notch sensitivity index of the ultra-high strength maraging steel TM210A was 0.69. PMID:28891934

Exploiting multi-scale parallelism for large scale numerical modelling of laser wakefield accelerators

NASA Astrophysics Data System (ADS)

Fonseca, R. A.; Vieira, J.; Fiuza, F.; Davidson, A.; Tsung, F. S.; Mori, W. B.; Silva, L. O.

2013-12-01

A new generation of laser wakefield accelerators (LWFA), supported by the extreme accelerating fields generated in the interaction of PW-Class lasers and underdense targets, promises the production of high quality electron beams in short distances for multiple applications. Achieving this goal will rely heavily on numerical modelling to further understand the underlying physics and identify optimal regimes, but large scale modelling of these scenarios is computationally heavy and requires the efficient use of state-of-the-art petascale supercomputing systems. We discuss the main difficulties involved in running these simulations and the new developments implemented in the OSIRIS framework to address these issues, ranging from multi-dimensional dynamic load balancing and hybrid distributed/shared memory parallelism to the vectorization of the PIC algorithm. We present the results of the OASCR Joule Metric program on the issue of large scale modelling of LWFA, demonstrating speedups of over 1 order of magnitude on the same hardware. Finally, scalability to over ˜106 cores and sustained performance over ˜2 P Flops is demonstrated, opening the way for large scale modelling of LWFA scenarios.

Ultra-weak FBG and its refractive index distribution in the drawing optical fiber.

PubMed

Guo, Huiyong; Liu, Fang; Yuan, Yinquan; Yu, Haihu; Yang, Minghong

2015-02-23

For the online writing of ultra-weak fiber Bragg gratings (FBGs) in the drawing optical fibers, the effects of the intensity profile, pulse fluctuation and pulse width of the excimer laser, as well as the transverse and longitudinal vibrations of the optical fiber have been investigated. Firstly, using Lorentz-Loren equation, Gladstone-Dale mixing rule and continuity equation, we have derived the refractive index (RI) fluctuation along the optical fiber and the RI distribution in the FBG, they are linear with the gradient of longitudinal vibration velocity. Then, we have prepared huge amounts of ultra-weak FBGs in the non-moving optical fiber and obtained their reflection spectra, the measured reflection spectra shows that the intensity profile and pulse fluctuation of the excimer laser, as well as the transverse vibration of the optical fiber are little responsible for the inconsistency of ultra-weak FBGs. Finally, the effect of the longitudinal vibration of the optical fiber on the inconsistency of ultra-weak FBGs has been discussed, and the vibration equations of the drawing optical fiber are given in the appendix.

Stunning Aurora Borealis from Space - Ultra-High Definition 4K

NASA Image and Video Library

2016-04-17

NASA Television’s newest offering, NASA TV UHD, brings ultra-high definition video to a new level with the kind of imagery only the world’s leader in space exploration could provide. Harmonic produced this show exclusively for NASA TV UHD, using time-lapses shot from the International Space Station, showing both the Aurora Borealis and Aurora Australis phenomena that occur when electrically charged electrons and protons in the Earth's magnetic field collide with neutral atoms in the upper atmosphere.

Ultra-high polarity ceramics induced extrinsic high permittivity of polymers contributing to high permittivity of 2-2 series composites

NASA Astrophysics Data System (ADS)

Feng, Yefeng; Zhang, Jianxiong; Hu, Jianbing; Peng, Cheng; He, Renqi

2018-01-01

Induced polarization at interface has been confirmed to have significant impact on the dielectric properties of 2-2 series composites bearing Si-based semi-conductor sheet and polymer layer. By compositing, the significantly elevated high permittivity in Si-based semi-conductor sheet should be responsible for the obtained high permittivity in composites. In that case, interface interaction could include two aspects namely a strong electrostatic force from high polarity polymeric layer and a newborn high polarity induced in Si-based ceramic sheet. In this work, this class of interface induced polarization was successfully extended into another 2-2 series composite system made up of ultra-high polarity ceramic sheet and high polarity polymer layer. By compositing, the greatly improved high permittivity in high polarity polymer layer was confirmed to strongly contribute to the high permittivity achieved in composites. In this case, interface interaction should consist of a rather large electrostatic force from ultra-high polarity ceramic sheet with ionic crystal structure and an enhanced high polarity induced in polymer layer based on a large polarizability of high polarity covalent dipoles in polymer. The dielectric and conductive properties of four designed 2-2 series composites and their components have been detailedly investigated. Increasing of polymer inborn polarity would lead to a significant elevating of polymer overall polarity in composite. Decline of inherent polarities in two components would result in a mild improving of polymer total polarity in composite. Introducing of non-polarity polymeric layer would give rise to a hardly unaltered polymer overall polarity in composite. The best 2-2 composite could possess a permittivity of ˜463 at 100 Hz 25.7 times of the original permittivity of polymer in it. This work might offer a facile route for achieving the promising composite dielectrics by constructing the 2-2 series samples from two high polarity

Ultra high energy events in ECHOS series and primary energy spectrum

NASA Technical Reports Server (NTRS)

Capdevielle, J. N.; Iwai, J.; Ogata, T.

1985-01-01

The compilation of ultra high energy jets suggests at present the existence of a bump in primary energy spectrum (with the standard concept of high energy collisions). The pseudo-rapidity distribution exhibits some typical anomalies, more than the (P sub t) behavior, which are (may be) the fingerprints of quark gluon plasma transition. The next results of Emulsion Chamber on Supersonic (ECHOS) will be in both cases determinant to confirm those tendancies, as well as an important effort of the cosmic ray community to develop in that sense a flying emulsion chamber experiment.

O-Ring sealing arrangements for ultra-high vacuum systems

DOEpatents

Kim, Chang-Kyo; Flaherty, Robert

1981-01-01

An all metal reusable O-ring sealing arrangement for sealing two concentric tubes in an ultra-high vacuum system. An O-ring of a heat recoverable alloy such as Nitinol is concentrically positioned between protruding sealing rings of the concentric tubes. The O-ring is installed between the tubes while in a stressed martensitic state and is made to undergo a thermally induced transformation to an austenitic state. During the transformation the O-ring expands outwardly and contracts inwardly toward a previously sized austenitic configuration, thereby sealing against the protruding sealing rings of the concentric tubes.

Lipid and glycolipid isomer analyses using ultra-high resolution ion mobility spectrometry separations

DOE PAGES

Wojcik, Roza; Webb, Ian K.; Deng, Liulin; ...

2017-01-18

Understanding the biological mechanisms related to lipids and glycolipids is challenging due to the vast number of possible isomers. Mass spectrometry (MS) measurements are currently the dominant approach for studying and providing detailed information on lipid and glycolipid structures. However, difficulties in distinguishing many structural isomers (e.g. distinct acyl chain positions, double bond locations, as well as glycan isomers) inhibit the understanding of their biological roles. Here we utilized ultra-high resolution ion mobility spectrometry (IMS) separations based upon the use of traveling waves in a serpentine long path length multi-pass Structures for Lossless Manipulations (SLIM) to enhance isomer resolution. Themore » multi-pass arrangement allowed separations ranging from ~16 m (1 pass) to ~470 m (32 passes) to be investigated for the distinction of lipids and glycolipids with extremely small structural differences. Lastly, these ultra-high resolution SLIM IMS-MS analyses provide a foundation for exploring and better understanding isomer specific biological and disease processes.« less

High power radiators of ultra-short electromagnetic quasi-unipolar pulses

NASA Astrophysics Data System (ADS)

Fedorov, V. M.; Ostashev, V. E.; Tarakanov, V. P.; Ul'yanov, A. V.

2017-05-01

Results of creation, operation, and diagnostics of the high power radiators for ultra-short length electromagnetic pulses (USEMPs) with a quasi-unipolar profile, which have been developed in our laboratory, are presented. The radiating module contains: the ultra-wideband (UWB) antenna array, the exciting high voltage pulse semiconductor generator (a pulser), the power source and the control unit. The principles of antenna array with a high efficiency aperture about 0.9 were developed using joint four TEM-horns with shielding electrodes in every TEM-horn. Sizes of the antenna apertures were (16-60) cm. The pulsers produced by “FID Technology” company had the following parameters: 50 Ohm connector impedance, unipolar pulses voltages (10-100) kV, the rise-time (0.04-0.15) ns, and the width (0.2-1) ns. The modules radiate the USEMPs of (0.1-10) GHz spectrum, their repetition rate is (1-100) kHz, and the effective potential is E*R = (20-400) kV, producing the peak E-field into the far-zone of R-distance. Parameters of the USEMP waves were measured by a calibrated sensor with the following characteristics: the sensitivity 0.32V/(kV/m), the rise-time 0.03 ns, the duration up to 7 ns. The measurements were in agreement with the simulation results, which were obtained using the 3-D code “KARAT”. The USEMP waves with amplitudes (1-10) kV/m and the pulse repetition rate (0.5-100) kHz were successfully used to examine various electronic devices for an electromagnetic immunity.

Ultra High Quality Factor Microtoroid for Chemical and Biomedical Sensing Applications

DTIC Science & Technology

2013-08-01

PERFORMING ORGANIZATION NAMES AND ADDRESSES U.S. Army Research Office P.O. Box 12211 Research Triangle Park, NC 27709-2211 15. SUBJECT TERMS resonator...PERFORMING ORGANIZATION REPORT NUMBER 19a. NAME OF RESPONSIBLE PERSON 19b. TELEPHONE NUMBER Lan Yang 314-935-9543 3. DATES COVERED (From - To...change. By using this ultra high-Q WGM resonator, radius >75nm polystyrene nanoparticle are detected in aquatic environment. In addition to polystyrene

Design, construction, and field testing of an ultra high performance concrete pi-girder bridge.

DOT National Transportation Integrated Search

2011-01-01

The Jakway Park Bridge in Buchanan County, Iowa is the first bridge constructed with a new prestesssed girder system composed of : precast Ultra-High Performance Concrete (UHPC). These girders employ an integral deck to facilitate construction and ar...

Design optimization of ultra-high concentrator photovoltaic system using two-stage non-imaging solar concentrator

NASA Astrophysics Data System (ADS)

Wong, C.-W.; Yew, T.-K.; Chong, K.-K.; Tan, W.-C.; Tan, M.-H.; Lim, B.-H.

2017-11-01

This paper presents a systematic approach for optimizing the design of ultra-high concentrator photovoltaic (UHCPV) system comprised of non-imaging dish concentrator (primary optical element) and crossed compound parabolic concentrator (secondary optical element). The optimization process includes the design of primary and secondary optics by considering the focal distance, spillage losses and rim angle of the dish concentrator. The imperfection factors, i.e. mirror reflectivity of 93%, lens’ optical efficiency of 85%, circumsolar ratio of 0.2 and mirror surface slope error of 2 mrad, were considered in the simulation to avoid the overestimation of output power. The proposed UHCPV system is capable of attaining effective ultra-high solar concentration ratio of 1475 suns and DC system efficiency of 31.8%.

Radiation cross-linking in ultra-high molecular weight polyethylene for orthopaedic applications

NASA Astrophysics Data System (ADS)

Oral, Ebru; Muratoglu, Orhun K.

2007-12-01

The motivation for radiation cross-linking of ultra-high molecular weight polyethylene (UHMWPE) is to increase its wear resistance to be used as bearing surfaces for total joint arthroplasty. However, radiation also leaves behind long-lived residual free radicals in this polymer, the reactions of which can detrimentally affect mechanical properties. In this review, we focus on the radiation cross-linking and oxidative stability of first and second generation highly cross-linked UHMWPEs developed in our laboratory.

Analytic model of electron self-injection in a plasma wakefield accelerator in the strongly nonlinear bubble regime

NASA Astrophysics Data System (ADS)

Yi, Sunghwan; Khudik, Vladimir; Shvets, Gennady

2012-10-01

We study self-injection into a plasma wakefield accelerator in the blowout (or bubble) regime, where the bubble evolves due to background density inhomogeneities. To explore trapping, we generalize an analytic model for the wakefields inside the bubble [1] to derive expressions for the fields outside. With this extended model, we show that a return current in the bubble sheath layer plays an important role in determining the trapped electron trajectories. We explore an injection mechanism where bubble growth due to a background density downramp causes reduction of the electron Hamiltonian in the co-moving frame, trapping the particle in the dynamically deepening potential well [2]. Model calculations agree quantitatively with PIC simulations on the bubble expansion rate required for trapping, as well as the range of impact parameters for which electrons are trapped. This is an improvement over our previous work [3] using a simplified spherical bubble model, which ignored the fields outside of the bubble and hence overestimated the expansion rate required for trapping. [4pt] [1] W. Lu et al., Phys. Plasmas 13, 056709 (2006).[0pt] [2] S. Kalmykov et al., Phys. Rev. Lett 103, 135004 (2009).[0pt] [3] S.A. Yi et al., Plasma Phys. Contr. Fus. 53, 014012 (2011).

FFT-impedance spectroscopy analysis of the growth of magnetic metal nanowires in ultra-high aspect ratio InP membranes

NASA Astrophysics Data System (ADS)

Gerngross, M.-D.; Carstensen, J.; Föll, H.; Adelung, R.

2016-01-01

This paper reports on the characterization of the electrochemical growth process of magnetic nanowires in ultra-high-aspect ratio InP membranes via in situ fast Fourier transform impedance spectroscopy in a typical frequency range from 75 Hz to 18.5 kHz. The measured impedance data from the Ni, Co, and FeCo can be very well fitted using the same electric equivalent circuit consisting of a series resistance in serial connection to an RC-element and a Maxwell element. The impedance data clearly indicate the similarities in the growth behavior of Ni, Co and FeCo nanowires in ultra-high aspect ratio InP membranes—the beneficial impact of boric acid on the metal deposition in ultra-high aspect ratio membranes and the diffusion limitation of boric acid, as well as differences such as passivation or side reactions.

Quantitation of phlorizin and phloretin using an ultra high performance liquid chromatography-electrospray ionization tandem mass spectrometric method.

PubMed

Lijia, Xu; Guo, Jianru; Chen, QianQian; Baoping, Jiang; Zhang, Wei

2014-06-01

A sensitive and selective ultra high performance liquid chromatography-tandem mass spectrometric (UHPLC-MS/MS) method for the determination of phlorizin and phloretin in human plasma has been firstly developed. Samples were prepared after protein precipitation and analyzed on a C18 column interfaced with a triple quadrupole tandem mass spectrometer. Negative electrospray ionization was employed as the ionization source. The mobile phase consisted of acetonitrile-water (0.02% formic acid), using a gradient procedure. The analytes and internal standard dihydroquercetin were both detected by use of multiple reaction monitoring mode. The method was linear in the concentration range of 2.5-1000.0 ng/mL. The lower limit of quantification (LLOQ) was 2.5 ng/mL. The intra- and inter-day relative standard deviation across three validation runs over the entire concentration range was less than 9.2%. The accuracy determined at three concentrations was within ± 7.3% in terms of relative error. The total run time was 12.0 min. This assay offers advantages in terms of expediency, and suitability for the analysis of phlorizin and phloretin in various biological fluids. Copyright © 2014 Elsevier B.V. All rights reserved.

Harmonics generation of a terahertz wakefield free-electron laser from a dielectric loaded waveguide excited by a direct current electron beam.

PubMed

Li, Weiwei; Lu, Yalin; He, Zhigang; Jia, Qika; Wang, Lin

2016-06-01

We propose to generate high-power terahertz (THz) radiation from a cylindrical dielectric loaded waveguide (DLW) excited by a direct-current electron beam with the harmonics generation method. The DLW supports a discrete set of modes that can be excited by an electron beam passing through the structure. The interaction of these modes with the co-propagating electron beam results in micro-bunching and the coherent enhancement of the wakefield radiation, which is dominated by the fundamental mode. By properly choosing the parameters of DLW and beam energy, the high order modes can be the harmonics of the fundamental one; thus, high frequency radiation corresponding to the high order modes will benefit from the dominating bunching process at the fundamental eigenfrequency and can also be coherently excited. With the proposed method, high power THz radiation can be obtained with an easily achievable electron beam and a large DLW structure.

Design of ultra high performance concrete as an overlay in pavements and bridge decks.

DOT National Transportation Integrated Search

2014-08-01

The main objective of this research was to develop ultra-high performance concrete (UHPC) as a reliable, economic, low carbon foot : print and durable concrete overlay material that can offer shorter traffic closures due to faster construction. The U...

Spheromaks and how plasmas may explain the ultra high energy cosmic ray mystery

NASA Astrophysics Data System (ADS)

Fowler, T. Kenneth; Li, Hui

2016-10-01

> eV or more, finally ejected as ultra high energy cosmic rays (UHECRs) long regarded as one of the mysteries of astrophysics. The acceleration is mainly due to the drift cyclotron loss cone kinetic instability known from plasma research. Experiments and simulations are suggested to verify the acceleration process.

Direct Laser Acceleration in Laser Wakefield Accelerators

NASA Astrophysics Data System (ADS)

Shaw, J. L.; Froula, D. H.; Marsh, K. A.; Joshi, C.; Lemos, N.

2017-10-01

The direct laser acceleration (DLA) of electrons in a laser wakefield accelerator (LWFA) has been investigated. We show that when there is a significant overlap between the drive laser and the trapped electrons in a LWFA cavity, the accelerating electrons can gain energy from the DLA mechanism in addition to LWFA. The properties of the electron beams produced in a LWFA, where the electrons are injected by ionization injection, have been investigated using particle-in-cell (PIC) code simulations. Particle tracking was used to demonstrate the presence of DLA in LWFA. Further PIC simulations comparing LWFA with and without DLA show that the presence of DLA can lead to electron beams that have maximum energies that exceed the estimates given by the theory for the ideal blowout regime. The magnitude of the contribution of DLA to the energy gained by the electron was found to be on the order of the LWFA contribution. The presence of DLA in a LWFA can also lead to enhanced betatron oscillation amplitudes and increased divergence in the direction of the laser polarization. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

Ultra-high vacuum compatible preparation chain for intermetallic compounds

NASA Astrophysics Data System (ADS)

Bauer, A.; Benka, G.; Regnat, A.; Franz, C.; Pfleiderer, C.

2016-11-01

We report the development of a versatile material preparation chain for intermetallic compounds, which focuses on the realization of a high-purity growth environment. The preparation chain comprises an argon glovebox, an inductively heated horizontal cold boat furnace, an arc melting furnace, an inductively heated rod casting furnace, an optically heated floating-zone furnace, a resistively heated annealing furnace, and an inductively heated annealing furnace. The cold boat furnace and the arc melting furnace may be loaded from the glovebox by means of a load-lock permitting to synthesize compounds starting with air-sensitive elements while handling the constituents exclusively in an inert gas atmosphere. All furnaces are all-metal sealed, bakeable, and may be pumped to ultra-high vacuum. We find that the latter represents an important prerequisite for handling compounds with high vapor pressure under high-purity argon atmosphere. We illustrate the operational aspects of the preparation chain in terms of the single-crystal growth of the heavy-fermion compound CeNi2Ge2.

Supernova 2010ev: A reddened high velocity gradient type Ia supernova

NASA Astrophysics Data System (ADS)

Gutiérrez, Claudia P.; González-Gaitán, Santiago; Folatelli, Gastón; Pignata, Giuliano; Anderson, Joseph P.; Hamuy, Mario; Morrell, Nidia; Stritzinger, Maximilian; Taubenberger, Stefan; Bufano, Filomena; Olivares E., Felipe; Haislip, Joshua B.; Reichart, Daniel E.

2016-05-01

Aims: We present and study the spectroscopic and photometric evolution of the type Ia supernova (SN Ia) 2010ev. Methods: We obtain and analyze multiband optical light curves and optical/near-infrared spectroscopy at low and medium resolution spanning -7 days to +300 days from the B-band maximum. Results: A photometric analysis shows that SN 2010ev is a SN Ia of normal brightness with a light-curve shape of Δm15(B) = 1.12 ± 0.02 and a stretch s = 0.94 ± 0.01 suffering significant reddening. From photometric and spectroscopic analysis, we deduce a color excess of E(B - V) = 0.25 ± 0.05 and a reddening law of Rv = 1.54 ± 0.65. Spectroscopically, SN 2010ev belongs to the broad-line SN Ia group, showing stronger than average Si IIλ6355 absorption features. We also find that SN 2010ev is a high velocity gradient SN with v˙Si = 164 ± 7 km s-1 d-1. The photometric and spectral comparison with other supernovae shows that SN 2010ev has similar colors and velocities to SN 2002bo and SN 2002dj. The analysis of the nebular spectra indicates that the [Fe II]λ7155 and [Ni II]λ7378 lines are redshifted, as expected for a high velocity gradient supernova. All these common intrinsic and extrinsic properties of the high velocity gradient (HVG) group are different from the low velocity gradient (LVG) normal SN Ia population and suggest significant variety in SN Ia explosions. This paper includes data gathered with the Du Pont Telescope at Las Campanas Observatory, Chile; and the Gemini Observatory, Cerro Pachon, Chile (Gemini Program GS-2010A-Q-14). Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile (ESO Programme 085.D-0577).

Enhancing thermal reliability of fiber-optic sensors for bio-inspired applications at ultra-high temperatures

NASA Astrophysics Data System (ADS)

Kang, Donghoon; Kim, Heon-Young; Kim, Dae-Hyun

2014-07-01

The rapid growth of bio-(inspired) sensors has led to an improvement in modern healthcare and human-robot systems in recent years. Higher levels of reliability and better flexibility, essential features of these sensors, are very much required in many application fields (e.g. applications at ultra-high temperatures). Fiber-optic sensors, and fiber Bragg grating (FBG) sensors in particular, are being widely studied as suitable sensors for improved structural health monitoring (SHM) due to their many merits. To enhance the thermal reliability of FBG sensors, thermal sensitivity, generally expressed as αf + ξf and considered a constant, should be investigated more precisely. For this purpose, the governing equation of FBG sensors is modified using differential derivatives between the wavelength shift and the temperature change in this study. Through a thermal test ranging from RT to 900 °C, the thermal sensitivity of FBG sensors is successfully examined and this guarantees thermal reliability of FBG sensors at ultra-high temperatures. In detail, αf + ξf has a non-linear dependence on temperature and varies from 6.0 × 10-6 °C-1 (20 °C) to 10.6 × 10-6 °C-1 (650 °C). Also, FBGs should be carefully used for applications at ultra-high temperatures due to signal disappearance near 900 °C.

High-speed microwave photonic switch for millimeter-wave ultra-wideband signal generation.

PubMed

Wang, Li Xian; Li, Wei; Zheng, Jian Yu; Wang, Hui; Liu, Jian Guo; Zhu, Ning Hua

2013-02-15

We propose a scheme for generating millimeter-wave (MMW) ultra-wideband (UWB) signal that is free from low-frequency components and a residual local oscillator. The system consists of two cascaded polarization modulators and is equivalent to a high-speed microwave photonic switch, which truncates a sinusoidal MMW into short pulses. The polarity switchability of the generated MMW-UWB pulse is also demonstrated.

Development of High-Gradient Dielectric Laser-Driven Particle Accelerator Structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Byer, Robert L.

2013-11-07

The thrust of Stanford's program is to conduct research on high-gradient dielectric accelerator structures driven with high repetition-rate, tabletop infrared lasers. The close collaboration between Stanford and SLAC (Stanford Linear Accelerator Center) is critical to the success of this project, because it provides a unique environment where prototype dielectric accelerator structures can be rapidly fabricated and tested with a relativistic electron beam.

Experimental signatures of direct-laser-acceleration-assisted laser wakefield acceleration

NASA Astrophysics Data System (ADS)

Shaw, J. L.; Lemos, N.; Marsh, K. A.; Froula, D. H.; Joshi, C.

2018-04-01

The direct laser acceleration (DLA) of electrons in a laser wakefield accelerator (LWFA) operating in the forced or quasi-blowout regimes has been investigated through experiment and simulation. When there is a significant overlap between the trapped electrons and the drive laser in a LWFA cavity, the resulting electrons can gain energy from both the LWFA and the DLA mechanisms. Experimental work investigates the properties of the electron beams produced in a LWFA with ionization injection by dispersing those beams in the direction perpendicular to the laser polarization. These electron beams show certain spectral features that are characteristic of DLA. These characteristic features are reproduced using particle-in-cell simulations, where particle tracking was used to elucidate the roles of LWFA and DLA to the energy gain of the electrons in this experimental regime and to demonstrate that such spectral features are definitive signatures of the presence of DLA in LWFA.

Application of Magnetic Suspension and Balance Systems to Ultra-High Reynolds Number Facilities

NASA Technical Reports Server (NTRS)

Britcher, Colin P.

1996-01-01

The current status of wind tunnel magnetic suspension and balance system development is briefly reviewed. Technical work currently underway at NASA Langley Research Center is detailed, where it relates to the ultra-high Reynolds number application. The application itself is addressed, concluded to be quite feasible, and broad design recommendations given.

Neutrinos, ultra-high-energy cosmic rays and fundamental physics

NASA Astrophysics Data System (ADS)

Ellis, John

2001-05-01

In the first lecture, aspects of neutrino physics beyond the Standard Model are emphasized, including the emerging default options for atmospheric and solar neutrino oscillations, namely νμ-->ντ and νe-->νμ,τ respectively, and the need to check them, the prospects opened up by the successful starts of SNO and K2K and the opportunities for future long-baseline neutrino experiments. In the second lecture, it is discussed how cosmic rays may provide opportunities for probing fundamental physics. For example, ultra-high-energy cosmic rays might originate from the decays of metastable heavy particles, and astrophysical γ rays can be used to test models of quantum gravity. Both scenarios offer ways to avoid the GZK cut-off, and might best be probed using high-energy astrophysical neutrinos. .

High Efficient Ultra-Thin Flat Optics Based on Dielectric Metasurfaces

NASA Astrophysics Data System (ADS)

Ozdemir, Aytekin

Metasurfaces which emerged as two-dimensional counterparts of metamaterials, facilitate the realization of arbitrary phase distributions using large arrays with subwavelength and ultra-thin features. Even if metasurfaces are ultra-thin, they still effectively manipulate the phase, amplitude, and polarization of light in transmission or reflection mode. In contrast, conventional optical components are bulky, and they lose their functionality at sub-wavelength scales, which requires conceptually new types of nanoscale optical devices. On the other hand, as the optical systems shrink in size day by day, conventional bulky optical components will have tighter alignment and fabrication tolerances. Since metasurfaces can be fabricated lithographically, alignment can be done during lithographic fabrication, thus eliminating the need for post-fabrication alignments. In this work, various types of metasurface applications are thoroughly investigated for robust wavefront engineering with enhanced characteristics in terms of broad bandwidth, high efficiency and active tunability, while beneficial for application. Plasmonic metasurfaces are not compatible with the CMOS process flow, and, additionally their high absorption and ohmic loss is problematic in transmission based applications. Dielectric metasurfaces, however, offer a strong magnetic response at optical frequencies, and thus they can offer great opportunities for interacting not only with the electric component of a light field, but also with its magnetic component. They show great potential to enable practical device functionalities at optical frequencies, which motivates us to explore them one step further on wavefront engineering and imaging sensor platforms. Therefore, we proposed an efficient ultra-thin flat metalens at near-infrared regime constituted by silicon nanodisks which can support both electric and magnetic dipolar Mie-type resonances. These two dipole resonances can be overlapped at the same frequency

Modification of Existing Prestressed Girder Cross-Sections for the Optimal Structural Use of Ultra-High Performance Concrete

DOT National Transportation Integrated Search

2008-10-22

Ultra High Performance Concrete (UHPC) is a class of cementitious materials that share similar characteristics including very large compressive strengths, tensile strength greater than conventional concrete and high durability. The material consists ...

H.sub.2O doped WO.sub.3, ultra-fast, high-sensitivity hydrogen sensors

DOEpatents

Liu, Ping [Denver, CO; Tracy, C Edwin [Golden, CO; Pitts, J Roland [Lakewood, CO; Lee, Se-Hee [Lakewood, CO

2011-03-22

An ultra-fast response, high sensitivity structure for optical detection of low concentrations of hydrogen gas, comprising: a substrate; a water-doped WO.sub.3 layer coated on the substrate; and a palladium layer coated on the water-doped WO.sub.3 layer.

Asymmetric Uncertainty Expression for High Gradient Aerodynamics

NASA Technical Reports Server (NTRS)

Pinier, Jeremy T

2012-01-01

When the physics of the flow around an aircraft changes very abruptly either in time or space (e.g., flow separation/reattachment, boundary layer transition, unsteadiness, shocks, etc), the measurements that are performed in a simulated environment like a wind tunnel test or a computational simulation will most likely incorrectly predict the exact location of where (or when) the change in physics happens. There are many reasons for this, includ- ing the error introduced by simulating a real system at a smaller scale and at non-ideal conditions, or the error due to turbulence models in a computational simulation. The un- certainty analysis principles that have been developed and are being implemented today do not fully account for uncertainty in the knowledge of the location of abrupt physics changes or sharp gradients, leading to a potentially underestimated uncertainty in those areas. To address this problem, a new asymmetric aerodynamic uncertainty expression containing an extra term to account for a phase-uncertainty, the magnitude of which is emphasized in the high-gradient aerodynamic regions is proposed in this paper. Additionally, based on previous work, a method for dispersing aerodynamic data within asymmetric uncer- tainty bounds in a more realistic way has been developed for use within Monte Carlo-type analyses.

Ultra high energy electrons powered by pulsar rotation.

PubMed

Mahajan, Swadesh; Machabeli, George; Osmanov, Zaza; Chkheidze, Nino

2013-01-01

A new mechanism of particle acceleration, driven by the rotational slow down of the Crab pulsar, is explored. The rotation, through the time dependent centrifugal force, can efficiently excite unstable Langmuir waves in the electron-positron (hereafter e(±)) plasma of the star magnetosphere. These waves, then, Landau damp on electrons accelerating them in the process. The net transfer of energy is optimal when the wave growth and the Landau damping times are comparable and are both very short compared to the star rotation time. We show, by detailed calculations, that these are precisely the conditions for the parameters of the Crab pulsar. This highly efficient route for energy transfer allows the electrons in the primary beam to be catapulted to multiple TeV (~ 100 TeV) and even PeV energy domain. It is expected that the proposed mechanism may, unravel the puzzle of the origin of ultra high energy cosmic ray electrons.

Cavity resonance absorption in ultra-high bandwidth CRT deflection structure by a resistive load

DOEpatents

Dunham, M.E.; Hudson, C.L.

1993-05-11

An improved ultra-high bandwidth helical coil deflection structure for a cathode ray tube is described comprising a first metal member having a bore therein, the metal walls of which form a first ground plane; a second metal member coaxially mounted in the bore of the first metal member and forming a second ground plane; a helical deflection coil coaxially mounted within the bore between the two ground planes; and a resistive load disposed in one end of the bore and electrically connected to the first and second ground planes, the resistive load having an impedance substantially equal to the characteristic impedance of the coaxial line formed by the two coaxial ground planes to inhibit cavity resonance in the structure within the ultra-high bandwidth of operation. Preferably, the resistive load comprises a carbon film on a surface of an end plug in one end of the bore.

Cavity resonance absorption in ultra-high bandwidth CRT deflection structure by a resistive load

DOEpatents

Dunham, Mark E.; Hudson, Charles L.

1993-01-01

An improved ultra-high bandwidth helical coil deflection structure for a hode ray tube is described comprising a first metal member having a bore therein, the metal walls of which form a first ground plane; a second metal member coaxially mounted in the bore of the first metal member and forming a second ground plane; a helical deflection coil coaxially mounted within the bore between the two ground planes; and a resistive load disposed in one end of the bore and electrically connected to the first and second ground planes, the resistive load having an impedance substantially equal to the characteristic impedance of the coaxial line formed by the two coaxial ground planes to inhibit cavity resonance in the structure within the ultra-high bandwidth of operation. Preferably, the resistive load comprises a carbon film on a surface of an end plug in one end of the bore.

Development of a highly sensitive methodology for quantitative determination of fexofenadine in a microdose study by multiple injection method using ultra-high performance liquid chromatography with tandem mass spectrometry.

PubMed

Tanaka, Yukari; Yoshikawa, Yutaka; Yasui, Hiroyuki

2012-01-01

An ultra high-sensitivity method for quantifying fexofenadine concentration in rat plasma samples by multiple injection method (MIM) was developed for a microdose study. In this study, MIM involved continuous injections of multiple samples containing the single compound into a column of the ultra-HPLC (UHPLC) system, and then, temporary trapping of the analyte at the column head. This was followed by elution of the compound from the column and detection by mass spectrometer. Fexofenadine, used as a model compound in this study, was extracted from the plasma samples by a protein precipitation method. Chromatographic separation was achieved on a reversed-phase C18 column by using a gradient method with 0.1% formic acid and 0.1% formic acid in acetonitrile as the mobile phase. The analyte was quantified in the positive-ion electrospray ionization mode using selected reaction monitoring. In this study, the analytical time per fexofenadine sample was approximately 2 min according to the UHPLC system. The method exhibited the linear dynamic ranges of 5-5000 pg/mL for fexofenadine in rat plasma. The intra-day precisions were from 3.2 to 8.7% and the accuracy range was 95.2-99.3%. The inter-day precisions and accuracies ranged from 3.5 to 8.4% and from 98.6 to 102.6%, respectively. The validated MIM was successfully applied to a microdose study in the rats that received oral administration of 100 µg/kg fexofenadine. We suggest that this method might be beneficial for the quantification of fexofenadine concentrations in a microdose clinical study.

Weld Metallurgy and Mechanical Properties of High Manganese Ultra-high Strength Steel Dissimilar Welds

NASA Astrophysics Data System (ADS)

Dahmen, Martin; Lindner, Stefan; Monfort, Damien; Petring, Dirk

The increasing demand for ultra-high strength steels in vehicle manufacturing leads to the application of new alloys. This poses a challenge on joining especially by fusion welding. A stainless high manganese steel sheet with excellent strength and deformation properties stands in the centre of the development. Similar and dissimilar welds with a metastable austenitic steel and a hot formed martensitic stainless steel were performed. An investigation of the mixing effects on the local microstructure and the hardness delivers the metallurgical features of the welds. Despite of carbon contents above 0.4 wt.% none of the welds have shown cracks. Mechanical properties drawn from tensile tests deliver high breaking forces enabling a high stiffness of the joints. The results show the potential for the application of laser beam welding for joining in assembly of structural parts.

Blazar 3C 66A: Another extragalactic source of ultra-high-energy gamma-ray photons

NASA Astrophysics Data System (ADS)

Neshpor, Yu. I.; Stepanyan, A. A.; Kalekin, O. P.; Fomin, V. P.; Chalenko, N. N.; Shitov, V. G.

1998-03-01

he observations of the object 3C 66A which were carried out with the GT-48 gamma-ray telescope at the Crimean Astrophysical Observatory in November-December 1996 revealed a flux of ultra-high-energy (>10^12 eV) gamma-ray photons from this blazar. According to preliminary estimates, the photon flux is (31) 10^11 photons cm^-2 s^-1. The blazar 3C 66A is the third extragalactic object from which a flux of ultra- high-energy gamma-ray photons was detected. Fluxes of gamma-ray photons were previously detected from the galaxies Mk 421 and Mk 501 at the Whipple observatory. This result provides further evidence that active processes proceed in blazars which are accompanied by the generation of cosmic rays responsible for the emission of gamma-ray photons.

A broadband high-transmission gradient phase discontinuity metasurface