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Sample records for high-current density nitrogen

  1. A Robust High Current Density Electron Gun

    NASA Astrophysics Data System (ADS)

    Mako, F.; Peter, W.; Shiloh, J.; Len, L. K.

    1996-11-01

    Proof-of-principle experiments are proposed to validate a new concept for a robust, high-current density Pierce electron gun (RPG) for use in klystrons and high brightness electron sources for accelerators. This rugged, long-life electron gun avoids the difficulties associated with plasma cathodes, thermionic emitters, and field emission cathodes. The RPG concept employs the emission of secondary electrons in a transmission mode as opposed to the conventional mode of reflection, i.e., electrons exit from the back face of a thin negative electron affinity (NEA) material, and in the same direction as the incident beam. Current amplification through one stage of a NEA material could be over 50 times. The amplification is accomplished in one or more stages consisting of one primary emitter and one or more secondary emitters. The primary emitter is a low current density robust emitter (e.g., thoriated tungsten). The secondary emitters are thin NEA electrodes which emit secondary electrons in the same direction as the incident beam. Specific application is targeted for a klystron gun to be used by SLAC with a cold cathode at 30-40 amps/cm^2 output from the secondary emission stage, a ~2 μs pulse length, and ~200 pulses/second.

  2. High current density cathode for electrorefining in molten electrolyte

    DOEpatents

    Li, Shelly X.

    2010-06-29

    A high current density cathode for electrorefining in a molten electrolyte for the continuous production and collection of loose dendritic or powdery deposits. The high current density cathode eliminates the requirement for mechanical scraping and electrochemical stripping of the deposits from the cathode in an anode/cathode module. The high current density cathode comprises a perforated electrical insulated material coating such that the current density is up to 3 A/cm.sup.2.

  3. High current density pulsed cathode experiments at SLAC

    SciTech Connect

    Koontz, R.; Fant, K.; Vlieks, A.

    1990-06-01

    A 1.9 microperveance beam diode has been constructed to test high current density cathodes for use in klystrons. Several standard and specially coated dispenser cathodes are being tested. Results of tests to date show average cathode current densities in excess of 25 amps/cm, and maximum electric field gradients of more than 450 kV/cm for pulses of the order of 1{mu}sec. 3 refs., 11 figs.

  4. Rf Gun with High-Current Density Field Emission Cathode

    SciTech Connect

    Jay L. Hirshfield

    2005-12-19

    High current-density field emission from an array of carbon nanotubes, with field-emission-transistor control, and with secondary electron channel multiplication in a ceramic facing structure, have been combined in a cold cathode for rf guns and diode guns. Electrodynamic and space-charge flow simulations were conducted to specify the cathode configuration and range of emission current density from the field emission cold cathode. Design of this cathode has been made for installation and testing in an existing S-band 2-1/2 cell rf gun. With emission control and modulation, and with current density in the range of 0.1-1 kA/cm2, this cathode could provide performance and long-life not enjoyed by other currently-available cathodes

  5. Ultra-high current density thin-film Si diode

    DOEpatents

    Wang, Qi [Littleton, CO

    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.

  6. 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.

  7. High current density stability of ohmic contacts to silicon carbide

    NASA Astrophysics Data System (ADS)

    Downey, Brian P.

    The materials properties of SiC, such as wide bandgap, high breakdown electric field, and good thermal conductivity, make it an appealing option for high temperature and high power applications. The replacement of Si devices with SiC components could lead to a reduction in device size, weight, complexity, and cooling requirements along with an increase in device efficiency. One area of concern under high temperature or high current operation is the stability of the ohmic contacts. Ohmic contact degradation can cause an increase in parasitic resistance, which can diminish device performance. While contact studies have primarily focused on the high temperature stability of ohmic contacts to SiC, different failure mechanisms may arise under high current density stressing due to the influence of electromigration. In addition, preferential degradation may occur at the anode or cathode due to the directionality of current flow, known as a polarity effect. The failure mechanisms of ohmic contacts to p-type SiC under high current density stressing are explored. Complementary materials characterization techniques were used to analyze contact degradation, particularly the use of cross-sections prepared by focused ion beam for imaging using field emission scanning electron microscopy and elemental analysis using Auger electron spectroscopy. Initially the degradation of commonly studied Ni and Al-based contacts was investigated under continuous DC current. The contact metallization included a bond pad consisting of a TiW diffusion barrier and thick Au overlayer. The Ni contacts were found to degrade due to the growth of voids within the ohmic contact layer, which were initially produced during the high temperature Ni/SiC ohmic contact anneal. The Al-based contacts degraded due to the movement of Al from the ohmic contact layer to the surface of the Au bond pad, and the movement of Au into the ohmic contact layer from the bond pad. The inequality of Al and Au fluxes generated

  8. High Current Density Scandate Cathodes for Future Vacuum Electronics Applications

    DTIC Science & Technology

    2008-05-30

    braze alloy . The structure was fired in a furnace at 16500 C for 15 minutes. The resultant structure was sectioned to determine if the scandium flowed...Density Cathodes for Future Vacuum Electronics Applications FA9550-07-C-0063 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION...Current Density Scandate Cathodes for Future Vacuum Electronics Applications USAF/AFRL Contract Number FA9550-07-C-0063 Final Report Calabazas Creek

  9. A high current density DC magnetohydrodynamic (MHD) micropump.

    PubMed

    Homsy, Alexandra; Koster, Sander; Eijkel, Jan C T; van den Berg, Albert; Lucklum, F; Verpoorte, E; de Rooij, Nico F

    2005-04-01

    This paper describes the working principle of a DC magnetohydrodynamic (MHD) micropump that can be operated at high DC current densities (J) in 75-microm-deep microfluidic channels without introducing gas bubbles into the pumping channel. The main design feature for current generation is a micromachined frit-like structure that connects the pumping channel to side reservoirs, where platinum electrodes are located. Current densities up to 4000 A m(-2) could be obtained without noticeable Joule heating in the system. The pump performance was studied as a function of current density and magnetic field intensity, as well as buffer ionic strength and pH. Bead velocities of up to 1 mm s(-1) (0.5 microL min(-1)) were observed in buffered solutions using a 0.4 T NdFeB permanent magnet, at an applied current density of 4000 A m(-2). This pump is intended for transport of electrolyte solutions having a relatively high ionic strength (0.5-1 M) in a DC magnetic field environment. The application of this pump for the study of biological samples in a miniaturized total analysis system (microTAS) with integrated NMR detection is foreseen. In the 7 T NMR environment, a minimum 16-fold increase in volumetric flow rate for a given applied current density is expected.

  10. A high current density plasma cathode electron gun

    SciTech Connect

    Fu Wenjie; Yan Yang; Li Wenxu; Li Xiaoyun; Wu Jianqiang

    2010-02-15

    The design, performance, and characteristics of a plasma cathode electron gun are presented. The plasma cathode is based on a hollow cathode direct current discharge, and the electron beam is accelerated by pulse voltage. By discharging at high gas pressure and operating at low gas pressure, both the maximum accelerating voltage and maximum emitting current could be increased. Utilizing argon, with the accelerating voltage up to 9 kV and gas pressure down to 52 mPa, the gun is able to generate an electron beam of about 4.7 A, and the corresponding emitting current density is about 600 A/cm{sup 2}.

  11. High current density, cryogenically cooled sliding electrical joint development

    SciTech Connect

    Murray, H.

    1986-09-01

    In the past two years, conceptual designs for fusion energy research devices have focussed on compact, high magnetic field configurations. The concept of sliding electrical joints in the large magnets allows a number of technical advantages including enhanced mechanical integrity, remote maintainability, and reduced project cost. The rationale for sliding electrical joints is presented. The conceptual configuration for this generation of experimental devices is highlghted by an approx. 20 T toroidal field magnet with a flat top conductor current of approx. 300 kA and a sliding electrical joint with a gross current density of approx. 0.6 kA/cm/sup 2/. A numerical model was used to map the conductor current distribution as a function of time and position in the conductor. A series of electrical joint arrangements were produced against the system code envelope constraints for a specific version of the Ignition Studies Project (ISP) which is designated as 1025.

  12. High current density contacts for photoconductive semiconductor switches

    SciTech Connect

    Baca, A.G.; Hjalmarson, H.P.; Loubriel, G.M.; McLaughlin, D.L.; Zutavern, F.J.

    1993-08-01

    The current densities implied by current filaments in GaAs photoconductive semiconductor switches (PCSS) are in excess of 1 MA/cm{sup 2}. As the lateral switches are tested repeatedly, damage accumulates at the contacts until electrical breakdown occurs across the surface of the insulating region. In order to improve the switch lifetime, the incorporation of n- and p-type ohmic contacts in lateral switches as well as surface geometry modifications have been investigated. By using p-type AuBe ohmic contacts at the anode and n-type AuGe ohmic contacts at the cathode, contact lifetime improvements of 5--10x were observed compared to switches with n-type contacts at both anode and cathode. Failure analysis on samples operated for 1--1,000 shots show that extensive damage still exists for at least one contact on all switches observed and that temperatures approaching 500{degrees}C are can be reached. However, the n-type AuGe cathode is often found to have no damage observable by scanning electron microscopy (SEM). The observed patterns of contact degradation indicate directions for future contact improvements in lateral switches.

  13. Thermionic cathode electron gun for high current densities

    NASA Astrophysics Data System (ADS)

    Herniter, Marc E.; Getty, Ward D.

    1987-08-01

    An electron gun using lanthanum hexaboride as a cathode material is being studied for use as a robust thermionic emitter at high cathode current densities. It has a standard planar cathode, Pierce-type electron gun design with a space-charge-limited perveance of 3.2 x 10 to the -6th A/V exp 3/2. Thus far it has been operated up to 36 kV in the space-charge-limited regime. The cathode is heated by electron bombardment and radiation from an auxiliary tungsten filament. The total heating requirement is found to be 202 W/sq cm of cathode area at a cathode temperature of 1626 C. These observations are found to be in reasonable agreement with a thermal steady-state power balance model. Beam current distribution measurements are made with a movable collector and Faraday cup, and are found to be in agreement with an electron-gun computer code. The cathode temperature distribution is also measured.

  14. High current density beamlets from RF Argon source for heavy ion fusion applications

    SciTech Connect

    Kwan, J.W.; Grote, D.P.; Westenskow, G.

    2003-08-01

    In a new approach to develop high current beams for heavy ion fusion, beam current at about 0.5 ampere per channel can be obtained by merging an array of high current density beamlets of 5 mA each. We have done computer simulations to study the transport of high current density beamlets and the emittance growth due to this merging process. In our RF multicusp source experiment, we have produced a cluster of 61 beamlets using minimum gas flow. The current density from a 0.25 cm diameter aperture reached 100 mA/cm{sup 2}. The normalized emittance of 0.02 {pi}-mm-mrad corresponds to an equivalent ion temperature of 2.4 eV. These results showed that the RF argon plasma source is suitable for producing high current density beamlets that can be merged to form a high current high brightness beam for HIF application.

  15. High Current Density Beamlets from an RF Argon Source for Heavy Ion Fusion Applications

    SciTech Connect

    Kwan, J W; Grote, D P; Westenskow, G A

    2003-09-04

    In a new approach to develop high current beams for heavy ion fusion, beam current at about 0.5 ampere per channel can be obtained by merging an array of high current density beamlets of 5 mA each. We have done computer simulations to study the transport of high current density beamlets and the emittance growth due to this merging process. In our RF multicusp source experiment, we have produced a cluster of 61 beamlets using minimum gas flow. The current density from a 0.25 cm diameter aperture reached 100 mA/cm{sup 2}. The normalized emittance of 0.02 {pi}-mm-mrad corresponds to an equivalent ion temperature of 2.4 eV. These results showed that the RF argon plasma source is suitable for producing high current density beamlets that can be merged to form a high current high brightness beam for HIF application.

  16. Current-confinement structure and extremely high current density in organic light-emitting transistors.

    PubMed

    Sawabe, Kosuke; Imakawa, Masaki; Nakano, Masaki; Yamao, Takeshi; Hotta, Shu; Iwasa, Yoshihiro; Takenobu, Taishi

    2012-12-04

    Extremely high current densities are realized in single-crystal ambipolar light-emitting transistors using an electron-injection buffer layer and a current-confinement structure via laser etching. Moreover, a linear increase in the luminance was observed at current densities of up to 1 kA cm(-2) , which is an efficiency-preservation improvement of three orders of magnitude over conventional organic light-emitting diodes (OLEDs) at high current densities.

  17. Quench protection and design of large high-current-density superconducting magnets

    SciTech Connect

    Green, M.A.

    1981-03-01

    Although most large superconducting magnets have been designed using the concept of cryostability, there is increased need for large magnets which operate at current densities above the cryostable limit (greater than 10/sup 8/ Am/sup -2/). Large high current density superconducting magnets are chosen for the following reasons: reduced mass, reduced coil thickness or size, and reduced cost. The design of large high current density, adiabatically stable, superconducting magnets requires a very different set of design rules than either large cryostable superconducting magnets or small self-protected high current density magnets. The problems associated with large high current density superconducting magnets fall into three categories; (a) quench protection, (b) stress and training, and (c) cryogenic design. The three categories must be considered simultaneously. The paper discusses quench protection and its implication for magnets of large stored energies (this includes strings of smaller magnets). Training and its relationship to quench protection and magnetic strain are discussed. Examples of magnets, built at the Lawrence Berkeley Laboratory and elsewhere using the design guidelines given in this report, are presented.

  18. Anodic Oxidation of Carbon Steel at High Current Densities and Investigation of Its Corrosion Behavior

    NASA Astrophysics Data System (ADS)

    Fattah-Alhosseini, Arash; Khan, Hamid Yazdani

    2017-02-01

    This work aims at studying the influence of high current densities on the anodization of carbon steel. Anodic protective coatings were prepared on carbon steel at current densities of 100, 125, and 150 A/dm2 followed by a final heat treatment. Coatings microstructures and morphologies were analyzed using X-ray diffraction (XRD) and scanning electron microscope (SEM). The corrosion resistance of the uncoated carbon steel substrate and the anodic coatings were evaluated in 3.5 wt pct NaCl solution through electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements. The results showed that the anodic oxide coatings which were prepared at higher current densities had thicker coatings as a result of a higher anodic forming voltage. Therefore, the anodized coatings showed better anti-corrosion properties compared to those obtained at lower current densities and the base metal.

  19. Highly efficient organic light-emitting devices beyond theoretical prediction under high current density.

    PubMed

    Tian, Miaomiao; Luo, Jinsong; Liu, Xingyuan

    2009-11-23

    We develop a simple method to improve external quantum efficiencies (EQEs) of OLEDs under a wide range of current density. An insulating inorganic ultrathin layer (LiF) was sandwiched between exciton formation layer and electron transporting layer. A maximal EQE of 5.9% in a DCM based fluorescent OLED, which far exceeds the theoretical upper limit of 3.7%, was obtained under the current density of 487 mA/cm(2) with a brightness maximum of 76740 cd/m(2). The similar electroluminescence properties were also obtained in a C545T based green OLED using this method. The overall enhancement of EQE, and the nonlinear enhancement of EQE at high current density in these devices are attributed to the effect of electrical field on excitons.

  20. Optimization of the epitaxial design of high current density resonant tunneling diodes for terahertz emitters

    NASA Astrophysics Data System (ADS)

    Baba, Razvan; Stevens, Benjamin J.; Mukai, Toshikazu; Hogg, Richard A.

    2016-02-01

    We discuss the numerical simulation of high current density InGaAs/AlAs/InP resonant tunneling diodes with a view to their optimization for application as THz emitters. We introduce a figure of merit based upon the ratio of maximum extractable THz power and the electrical power developed in the chip. The aim being to develop high efficiency emitters as output power is presently limited by catastrophic failure. A description of the interplay of key parameters follows, with constraints on strained layer epitaxy introduced. We propose an optimized structure utilizing thin barriers paired with a comparatively wide quantum well that satisfies strained layer epitaxy constraints.

  1. A study of (cold fusion) in deuterated titanium subjected to high-current densities

    SciTech Connect

    Campbell, R.B. ); Perkins, L.J. )

    1989-11-01

    In response to the startling announcement of fusion reactions occurring at room temperature by Fleischmann and Pons (F-P), the possible role of high-current densities in producing neutrons and excess heat in deuterated titanium maintained near ambient temperatures and pressures is examined. The apparatus used consists of a balanced resistive circuit containing a deuterated active element and a hydrogenated control element. The use of a simple electrical circuit (no electrolysis) with elements made of chemically stable TiD{sub x}, X = 0.9, removes the complications involved in distinguishing between heat released by chemical versus nuclear process in an electrolytic cell. In this paper, it is concluded that the large quantity of excess heat reported by Fleischmann and Pons is due to the presence of factors other than the current density.

  2. High current density and low turn-on field from aligned Cd(OH)2 nanosheets

    NASA Astrophysics Data System (ADS)

    Bagal, Vivekanand S.; Patil, Girish P.; Deore, Amol B.; Baviskar, Prashant K.; Suryawanshi, Sachin R.; More, Mahendra A.; Chavan, Padmakar G.

    2016-04-01

    High current density of 9.8 mA/cm2 was drawn at an applied field of 4.1 V/μm from aligned Cd(OH)2 nanosheets and low turn-on field of 1.4 V/μm was found for the emission current density of 10 μA/cm2. The aligned Cd(OH)2 nanosheets were synthesized by CBD technique on Cadmium foil. To the best of our knowledge this is the first report on the field emission studies of Cd(OH)2 nanosheets. Simple synthesis route coupled with superior field emission properties indicate the possible use of Cd(OH)2 nanosheets for micro/nanoelectronic devices.

  3. High-field, high-current-density, stable superconducting magnets for fusion machines

    SciTech Connect

    Lue, J.W.; Dresner, L.; Lubell, M.S.

    1989-01-01

    Designs for large fusion machines require high-performance superconducting magnets to reduce cost or increase machine performance. By employing force-flow cooling, cable-in-conduit conductor configuration, and NbTi superconductor, it is now possible to design superconducting magnets that operate a high fields (8-12 T) with high current densities (5-15 kA/cm/sup 2/ over the winding pack) in a stable manner. High current density leads to smaller, lighter, and thus less expensive coils. The force-flow cooling provides confined helium, full conductor insulation, and a rigid winding pack for better load distribution. The cable-in-conduit conductor configuration ensures a high stability margin for the magnet. The NbTi superconductor has reached a good engineering material standard. Its strain-insensitive critical parameters are particularly suitable for complex coil windings of a stellarator machine. The optimization procedure for such a conductor design, developed over the past decade, is summarized here. If desired a magnet built on the principles outlines in this paper can be extended to a field higher than the design value without degrading its stability by simply lowering the operating temperature below 4.2 K. 11 refs., 3 figs.

  4. Characterisation of high current density resonant tunneling diodes for THz emission using photoluminescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Jacobs, Kristof J. P.; Baba, Razvan; Stevens, Benjamin J.; Mukai, Toshikazu; Ohnishi, Dai; Hogg, Richard A.

    2016-03-01

    Resonant tunneling diodes (RTDs) provide high speed current oscillation which is applicable to THz generation when coupled to a suitably designed antenna. For this purpose, the InGaAs/AlAs/InP materials have been used, as this system offers high electron mobility, suitable band-offsets, and low resistance contacts. However for high current density operation (~MA/cm2) the epitaxial structure is challenging to characterize using conventional techniques as it consists of a single, very thin AlAs/InGaAs quantum well (QW). Here, we present a detailed low temperature photoluminescence spectroscopic study of high current density RTDs that allow the non-destructive mapping of a range of critical parameters for the device. We show how the doping level of the emitter/collector and contact layers in the RTD structure can be measured using the Moss-Burstein effect. For the full device structure, we show how emission from the QW may be identified, and detail how the emission changes with differing indium composition and well widths. We show that by studying nominally identical, un-doped structures, a type-II QW emission is observed, and explain the origin of the type-I emission in doped devices. This observation opens the way for a new characterization scheme where a "dummy" RTD active element is incorporated below the real RTD structure. This structure allows significantly greater control in the epitaxial process.

  5. Incorporation of Ca and P on anodized titanium surface: Effect of high current density.

    PubMed

    Laurindo, Carlos A H; Torres, Ricardo D; Mali, Sachin A; Gilbert, Jeremy L; Soares, Paulo

    2014-04-01

    This study systematically evaluated the surface and corrosion characteristics of commercially pure titanium (grade 2) modified by plasma electrolytic oxidation (PEO) with high current density. The anodization process was carried out galvanostatically (constant current density) using a solution containing calcium glycerophosphate (0.02mol/L) and calcium acetate (0.15mol/L). The current densities applied were 400, 700, 1000 and 1200mA/cm(2) for a period of 15s. Composition, crystalline structure, morphology, roughness, wettability and "in-vitro" bioactivity test in SBF of the anodized layer were evaluated by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, profilometry and contact angle measurements. Corrosion properties were evaluated by open circuit potential, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements. The results show that the TiO2 oxide layers present an increase of thickness, porosity, roughness, wettability, Ca/P ratio, and bioactivity, with the applied current density up to 1000mA/cm(2). Corrosion resistance also increases with applied current density. It is observed that for 1200mA/cm(2), there is a degradation of the oxide layer. In general, the results suggest that the anodized TiO2 layer with better properties is formed with an applied current of 1000mA/cm(2).

  6. Studies in High Current Density Ion Sources for Heavy Ion Fusion Applications

    SciTech Connect

    Chacon-Golcher, Edwin

    2002-06-01

    This dissertation develops diverse research on small (diameter ~ few mm), high current density (J ~ several tens of mA/cm2) heavy ion sources. The research has been developed in the context of a programmatic interest within the Heavy Ion Fusion (HIF) Program to explore alternative architectures in the beam injection systems that use the merging of small, bright beams. An ion gun was designed and built for these experiments. Results of average current density yield () at different operating conditions are presented for K+ and Cs+ contact ionization sources and potassium aluminum silicate sources. Maximum values for a K+ beam of ~90 mA/cm2 were observed in 2.3 μs pulses. Measurements of beam intensity profiles and emittances are included. Measurements of neutral particle desorption are presented at different operating conditions which lead to a better understanding of the underlying atomic diffusion processes that determine the lifetime of the emitter. Estimates of diffusion times consistent with measurements are presented, as well as estimates of maximum repetition rates achievable. Diverse studies performed on the composition and preparation of alkali aluminosilicate ion sources are also presented. In addition, this work includes preliminary work carried out exploring the viability of an argon plasma ion source and a bismuth metal vapor vacuum arc (MEVVA) ion source. For the former ion source, fast rise-times (~ 1 μs), high current densities (~ 100 mA/cm+) and low operating pressures (< 2 mtorr) were verified. For the latter, high but acceptable levels of beam emittance were measured (εn ≤ 0.006 π· mm · mrad) although measured currents differed from the desired ones (I ~ 5mA) by about a factor of 10.

  7. Crystallization of Ti33Cu67 metallic glass under high-current density electrical pulses

    PubMed Central

    2011-01-01

    We have studied the phase and structure evolution of the Ti33Cu67 amorphous alloy subjected to electrical pulses of high current density. By varying the pulse parameters, different stages of crystallization could be observed in the samples. Partial polymorphic nanocrystallization resulting in the formation of 5- to 8-nm crystallites of the TiCu2 intermetallic in the residual amorphous matrix occurred when the maximum current density reached 9.7·108 A m-2 and the pulse duration was 140 μs, though the calculated temperature increase due to Joule heating was not enough to reach the crystallization temperature of the alloy. Samples subjected to higher current densities and higher values of the evolved Joule heat per unit mass fully crystallized and contained the Ti2Cu3 and TiCu3 phases. A common feature of the crystallized ribbons was their non-uniform microstructure with regions that experienced local melting and rapid solidification. PACS: 81; 81.05.Bx; 81.05.Kf. PMID:21871070

  8. High Current Density, Long Life Cathodes for High Power RF Sources

    SciTech Connect

    Ives, Robert Lawrence; Collins, George; Falce, Lou; Schwartzkopf, Steve; Busbaher, Daniel

    2014-01-22

    This program was tasked with improving the quality and expanding applications for Controlled Porosity Reservoir (CPR) cathodes. Calabazas Creek Research, Inc. (CCR) initially developed CPR cathodes on a DOE-funded SBIR program to improve cathodes for magnetron injection guns. Subsequent funding was received from the Defense Advanced Research Projects Agency. The program developed design requirements for implementation of the technology into high current density cathodes for high frequency applications. During Phase I of this program, CCR was awarded the prestigious 2011 R&D100 award for this technology. Subsequently, the technology was presented at numerous technical conferences. A patent was issued for the technology in 2009. These cathodes are now marketed by Semicon Associates, Inc. in Lexington, KY. They are the world’s largest producer of cathodes for vacuum electron devices. During this program, CCR teamed with Semicon Associates, Inc. and Ron Witherspoon, Inc. to improve the fabrication processes and expand applications for the cathodes. Specific fabrications issues included the quality of the wire winding that provides the basic structure and the sintering to bond the wires into a robust, cohesive structure. The program also developed improved techniques for integrating the resulting material into cathodes for electron guns.

  9. Thermal instability induced by high current densities in high-Tc coated conductors

    NASA Astrophysics Data System (ADS)

    Maza, J.; Ferro, G.; Veira, J. A.; Vidal, F.

    2013-10-01

    By using a 1 ms pulse technique, the current-voltage curves (CVC) under zero-applied magnetic field have been measured in practical high-Tc superconducting wires based on coated (RE)BCO. The measurements extend up to the so-called supercritical current intensity, I*, at which superconductivity disappears accompanied by an abrupt jump in the voltage. The resulting CVC, including the temperature dependence of I*, were analysed at a quantitative level in terms of a thermal instability model proposed recently. An attractive aspect of our thermal instability approach is that in spite of the complexity of the coated layered structure, in its simpler formulation all the geometric and thermal variables are encapsulated into a single characteristic parameter r with units of thermal resistance. All the experimental results for I* from 76 to 86 K are quantitatively, within 2%, accounted for by the thermal instability analysis. Furthermore, the best-fit value of r is found to be quite consistent with the inner geometry and composition of the wires. Another remarkable result of our analysis is that the temperature T* reached by the wire at I*, i.e., the temperature triggering the thermal runaway, is less than one kelvin above the bath temperature. These results further support the universality of the thermal instability mechanism of superconductivity quenching by high current densities.

  10. Metal based gas diffusion layers for enhanced fuel cell performance at high current densities

    NASA Astrophysics Data System (ADS)

    Hussain, Nabeel; Van Steen, Eric; Tanaka, Shiro; Levecque, Pieter

    2017-01-01

    The gas diffusion layer strongly influences the performance and durability of polymer electrolyte fuel cells. A major drawback of current carbon fiber based GDLs is the non-controlled variation in porosity resulting in a random micro-structure. Moreover, when subjected to compression these materials show significant reduction in porosity and permeability leading to water management problems and mass transfer losses within the fuel cell. This study investigated the use of uniform perforated metal sheets as GDLs in conjunction with microchannel flowfields. A metal sheet design with a pitch of 110 μm and a hole diameter of 60 μm in combination with an MPL showed superior performance in the high current density region compared to a commercially available carbon paper based GDL in a single cell environment. Fuel cell testing with different oxidants (air, heliox and oxygen) indicate that the metal sheet offers both superior diffusion and reduced flooding in comparison to the carbon based GDL. The presence of the MPL has been found to be critical to the functionality of the metal sheet suggesting that the MPL design may represent an important optimisation parameter for further improvements in performance.

  11. Quasi-1D van der Waals materials as high current-density local interconnects (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Stolyarov, Maxim; Aytan, Ece; Bloodgood, Matthew; Salguero, Tina T.; Balandin, Alexander A.

    2016-09-01

    The continuous downscaling of interconnect dimensions in combination with the introduction of low-k dielectrics has increased the number of heat dissipation, integration and reliability challenges in modern electronics. As a result, there is a strong need for new materials that have high current-carrying capacity for applications as nanoscale interconnects. In this presentation, we show that quasi-one-dimensional (1D) van der Waals metals such as TaSe3 have excellent breakdown current density exceeding that of 5 MA/cm2. This value is above that currently achievable in conventional copper or aluminum wires. The quasi-1D van der Waals materials are characterized by strong bonds along one dimension and weak van der Waals bonds along two other dimensions. The material for this study was grown by the chemical vapor transport (CVT) method. Both mechanical and chemical exfoliation methods were used to fabricate nanowires with lateral dimensions below 100 nm. The dimensions of the quasi-1D nanowires were verified with scanning electron microscopy (SEM) and atomic force microscopy (AFM). The metal (Ti/Au) contacts for the electrical characterization were deposited using electron beam evaporation (EBE). The measurements were conducted on a number of prototype interconnects with multiple electric contacts to ensure reproducibility. The obtained results suggest that quasi-1D van der Waals metals present a feasible alternative to conventional copper interconnects in terms of the current-carrying capacity and the breakdown current-density. This work was supported, in part, by the SRC and DARPA through STARnet Center for Function Accelerated nanoMaterial Engineering (FAME).

  12. Effects of Neutral Density on Energetic Ions Produced Near High-Current Hollow Cathodes

    NASA Technical Reports Server (NTRS)

    Kameyama, Ikuya

    1997-01-01

    Energy distributions of ion current from high-current, xenon hollow cathodes, which are essential information to understand erosion phenomena observed in high-power ion thrusters, were obtained using an electrostatic energy analyzer (ESA). The effects of ambient pressure and external flow rate introduced immediately downstream of hollow cathode on ion currents with energies greater than that associated with the cathode-to-anode potential difference were investigated. The results were analyzed to determine the changes in the magnitudes of ion currents to the ESA at various energies. Either increasing the ambient pressure or adding external flow induces an increase in the distribution of ion currents with moderate energies (epsilon less than 25 to 35 eV) and a decrease in the distribution for high energies (epsilon greater than 25 to 35 eV). The magnitude of the current distribution increase in the moderate energy range is greater for a cathode equipped with a toroidal keeper than for one without a keeper, but the distribution in the high energy range does not seem to be affected by a keeper. An MHD model, which has been proposed to describe energetic-ion production mechanism in hollow cathode at high discharge currents, was developed to describe these effects. The results show, however, that this model involves no mechanism by which a significant increase of ion current could occur at any energy. It was found, on the other hand, that the potential-hill model of energetic ion production, which assumes existence of a local maximum of plasma potential, could explain combined increases in the currents of ions with moderate energies and decreases in high energy ions due to increased neutral atom density using a charge-exchange mechanism. The existing, simplified version of the potential-hill model, however, shows poor quantitative agreement with measured ion-current-energy-distribution changes induced by neutral density changes.

  13. High current density PQQ-dependent alcohol and aldehyde dehydrogenase bioanodes.

    PubMed

    Aquino Neto, Sidney; Hickey, David P; Milton, Ross D; De Andrade, Adalgisa R; Minteer, Shelley D

    2015-10-15

    In this paper, we explore the bioelectrooxidation of ethanol using pyrroloquinoline quinone (PQQ)-dependent alcohol and aldehyde dehydrogenase (ADH and AldDH) enzymes for biofuel cell applications. The bioanode architectures were designed with both direct electron transfer (DET) and mediated electron transfer (MET) mechanisms employing high surface area materials such as multi-walled carbon nanotubes (MWCNTs) and MWCNT-decorated gold nanoparticles, along with different immobilization techniques. Three different polymeric matrices were tested (tetrabutyl ammonium bromide (TBAB)-modified Nafion; octyl-modified linear polyethyleneimine (C8-LPEI); and cellulose) in the DET studies. The modified Nafion membrane provided the best electrical communication between enzymes and the electrode surface, with catalytic currents as high as 16.8 ± 2.1 µA cm(-2). Then, a series of ferrocene redox polymers were evaluated for MET. The redox polymer 1,1'-dimethylferrocene-modified linear polyethyleneimine (FcMe2-C3-LPEI) provided the best electrochemical response. Using this polymer, the electrochemical assays conducted in the presence of MWCNTs and MWCNTs-Au indicated a Jmax of 781 ± 59 µA cm(-2) and 925 ± 68 µA cm(-2), respectively. Overall, from the results obtained here, DET using the PQQ-dependent ADH and AldDH still lacks high current density, while the bioanodes that operate via MET employing ferrocene-modified LPEI redox polymers show efficient energy conversion capability in ethanol/air biofuel cells. Copyright © 2015 Elsevier B.V. All rights reserved.

  14. Liquid nitrogen cooled integrated power electronics module with high current carrying capability and lower on resistance

    NASA Astrophysics Data System (ADS)

    Ye, Hua; Lee, Changwoo; Simon, Randy W.; Haldar, Pradeep; Hennessy, Michael J.; Mueller, Eduard K.

    2006-11-01

    This letter presents the development of high-performance integrated cryogenic power modules, where both driver components and power metal-oxide semiconductor field-effect transistors are integrated in a single package, to be used in a 50kW prototype cryogenic inverter operating at liquid nitrogen temperature. The authors have demonstrated a compact high-voltage, cryogenic integrated power module that exhibited more than 14 times improvement in on-resistance and continuous current carrying capability exceeding 40A. The modules are designed to operate at liquid nitrogen temperature with extreme thermal cycling. The power electronic modules are necessary components that provide control and switching for second generation, yttrium barium copper oxide-based high temperature superconductor devices including cables, motors, and generators.

  15. High Current, High Density Arc Plasma as a New Source for WiPAL

    NASA Astrophysics Data System (ADS)

    Waleffe, Roger; Endrizzi, Doug; Myers, Rachel; Wallace, John; Clark, Mike; Forest, Cary; WiPAL Team

    2016-10-01

    The Wisconsin Plasma Astrophysics Lab (WiPAL) has installed a new array of nineteen plasma sources (plasma guns) on its 3 m diameter, spherical vacuum vessel. Each gun is a cylindrical, molybdenum, washer-stabilized, arc plasma source. During discharge, the guns are maintained at 1.2 kA across 100 V for 10 ms by the gun power supply establishing a high density plasma. Each plasma source is fired independently allowing for adjustable plasma parameters, with densities varying between 1018 -1019 m-3 and electron temperatures of 5-15 eV. Measurements were characterized using a 16 tip Langmuir probe. The plasma source will be used as a background plasma for the magnetized coaxial plasma gun (MCPG), the Terrestrial Reconnection Experiment (TREX), and as the plasma source for a magnetic mirror experiment. Temperature, density, and confinement results will be presented. This work is supported by the DoE and the NSF.

  16. Short-pulse high-current-density photoemission in high electric fields

    SciTech Connect

    Fischer, J.; Srinivasan-Rao, T.

    1987-01-01

    We present the experimental results of photoemission studies on thin wires of gold-coated tungsten, held at surface fields in the range of 10/sup 6/ to 3 x 10/sup 8/ V/m, and illuminated by 10 ps long, 4.66 eV photon laser pulses. The wire cathodes arranged coaxially in an anode experienced a surface-field enhancement of 10/sup 2/ to 10/sup 3/ over the applied voltage. We obtained current densities exceeding 10 kA/cm/sup 2/ from a 50 ..mu..m diameter wire, from a (50 x 400) ..mu..m/sup 2/ area, under partially space-change-limited conditions. The quantum efficiency for emission-limited cases was in the range of 10/sup -5/. For these cases results using 50 ..mu..m and 4 ..mu..m diameter wires indicated linear dependence of charge density with optical energy density. The emission also scaled linearly with the emitting area. For surface fields above 3 x 10/sup 7/ V/m, a twofold enhancement of emission was observed for a tenfold increase in the field. 7 refs., 9 figs.

  17. High current density electropolishing in the preparation of highly smooth substrate tapes for coated conductors

    DOEpatents

    Kreiskott, Sascha [Los Alamos, NM; Matias, Vladimir [Santa Fe, NM; Arendt, Paul N [Los Alamos, NM; Foltyn, Stephen R [Los Alamos, NM; Bronisz, Lawrence E [Los Alamos, NM

    2009-03-31

    A continuous process of forming a highly smooth surface on a metallic tape by passing a metallic tape having an initial roughness through an acid bath contained within a polishing section of an electropolishing unit over a pre-selected period of time, and, passing a mean surface current density of at least 0.18 amperes per square centimeter through the metallic tape during the period of time the metallic tape is in the acid bath whereby the roughness of the metallic tape is reduced. Such a highly smooth metallic tape can serve as a base substrate in subsequent formation of a superconductive coated conductor.

  18. Surface Lattice Resonances for Enhanced and Directional Electroluminescence at High Current Densities

    PubMed Central

    2016-01-01

    Hybrid photonic-plasmonic modes in periodic arrays of metallic nanostructures offer a promising trade-off between high-quality cavities and subdiffraction mode confinement. However, their application in electrically driven light-emitting devices is hindered by their sensitivity to the surrounding environment and to charge injecting metallic electrodes in particular. Here, we demonstrate that the planar structure of light-emitting field-effect transistor (LEFET) ensures undisturbed operation of the characteristic modes. We incorporate a square array of gold nanodisks into the charge transporting and emissive layer of a polymer LEFET in order to tailor directionality and emission efficiency via the Purcell effect and variation of the fractional local density of states in particular. Angle- and polarization-resolved spectra confirm that the enhanced electroluminescence correlates with the dispersion curves of the surface lattice resonances supported by these structures. These LEFETs reach current densities on the order of 10 kA/cm2, which may pave the way toward practical optoelectronic devices with tailored emission patterns and potentially electrically pumped plasmonic lasers. PMID:28042593

  19. Surface Lattice Resonances for Enhanced and Directional Electroluminescence at High Current Densities.

    PubMed

    Zakharko, Yuriy; Held, Martin; Graf, Arko; Rödlmeier, Tobias; Eckstein, Ralph; Hernandez-Sosa, Gerardo; Hähnlein, Bernd; Pezoldt, Jörg; Zaumseil, Jana

    2016-12-21

    Hybrid photonic-plasmonic modes in periodic arrays of metallic nanostructures offer a promising trade-off between high-quality cavities and subdiffraction mode confinement. However, their application in electrically driven light-emitting devices is hindered by their sensitivity to the surrounding environment and to charge injecting metallic electrodes in particular. Here, we demonstrate that the planar structure of light-emitting field-effect transistor (LEFET) ensures undisturbed operation of the characteristic modes. We incorporate a square array of gold nanodisks into the charge transporting and emissive layer of a polymer LEFET in order to tailor directionality and emission efficiency via the Purcell effect and variation of the fractional local density of states in particular. Angle- and polarization-resolved spectra confirm that the enhanced electroluminescence correlates with the dispersion curves of the surface lattice resonances supported by these structures. These LEFETs reach current densities on the order of 10 kA/cm(2), which may pave the way toward practical optoelectronic devices with tailored emission patterns and potentially electrically pumped plasmonic lasers.

  20. Electron density profile measurements at a self-focusing ion beam with high current density and low energy extracted through concave electrodes

    SciTech Connect

    Fujiwara, Y. Nakamiya, A.; Sakakita, H.; Hirano, Y.; Kiyama, S.; Koguchi, H.

    2014-02-15

    The self-focusing phenomenon has been observed in a high current density and low energy ion beam. In order to study the mechanism of this phenomenon, a special designed double probe to measure the electron density and temperature is installed into the chamber where the high current density ion beam is injected. Electron density profile is successfully measured without the influence of the ion beam components. Estimated electron temperature and density are ∼0.9 eV and ∼8 × 10{sup 8} cm{sup −3} at the center of ion beam cross section, respectively. It was found that a large amount of electrons are spontaneously accumulated in the ion beam line in the case of self-forcing state.

  1. High voltage and high current density vertical GaN power diodes

    SciTech Connect

    Fischer, A. J.; Dickerson, J. R.; Armstrong, A. M.; Moseley, M. W.; Crawford, M. H.; King, M. P.; Allerman, A. A.; Kaplar, R. J.; van Heukelom, M. S.; Wierer, J. J.

    2016-01-01

    We report on the realization of a GaN high voltage vertical p-n diode operating at > 3.9 kV breakdown with a specific on-resistance < 0.9 mΩ.cm2. Diodes achieved a forward current of 1 A for on-wafer, DC measurements, corresponding to a current density > 1.4 kA/cm2. An effective critical electric field of 3.9 MV/cm was estimated for the devices from analysis of the forward and reverse current-voltage characteristics. Furthermore this suggests that the fundamental limit to the GaN critical electric field is significantly greater than previously believed.

  2. Field Emission Study of Carbon Nanotubes: High Current Density from Nanotube Bundle Arrays

    NASA Technical Reports Server (NTRS)

    Bronikowski, Micheal J.; Manohara, Harish M.; Siegel, Peter H.; Hunt, Brian D.

    2004-01-01

    We have investigated the field emission behavior of lithographically patterned bundles of multiwalled carbon nanotubes arranged in a variety of array geometries. Such arrays of nanotube bundles are found to perform significantly better in field emission than arrays of isolated nanotubes or dense, continuous mats of nanotubes, with the field emission performance depending on the bundle diameter and inter-bundle spacing. Arrays of 2-micrometers diameter nanotube bundles spaced 5 micrometers apart (edge-to-edge spacing) produced the largest emission densities, routinely giving 1.5 to 1.8 A/cm(sup 2) at approximately 4 V/micrometer electric field, and greater than 6 A/cm(sup 2) at 20 V/micrometers.

  3. High voltage and high current density vertical GaN power diodes

    DOE PAGES

    Fischer, A. J.; Dickerson, J. R.; Armstrong, A. M.; ...

    2016-01-01

    We report on the realization of a GaN high voltage vertical p-n diode operating at > 3.9 kV breakdown with a specific on-resistance < 0.9 mΩ.cm2. Diodes achieved a forward current of 1 A for on-wafer, DC measurements, corresponding to a current density > 1.4 kA/cm2. An effective critical electric field of 3.9 MV/cm was estimated for the devices from analysis of the forward and reverse current-voltage characteristics. Furthermore this suggests that the fundamental limit to the GaN critical electric field is significantly greater than previously believed.

  4. Analysis of atomic thermospheric nitrogen density

    NASA Technical Reports Server (NTRS)

    Engebretson, M. J.

    1985-01-01

    A NASA grant provided support for a research project at Augsbury College, Minneapolis, Minnesota for the analysis of atomic nitrogen density data obtained by the Neutral Atmospheric Composition Spectrometer (NACS) on board the Dynamics Explorer-2 satellite. Initial funding was for an exploratory study of the feasibility of obtaining ambient densities of N from source densities of NO. Funding was continued under the Dynamics Explorer Guest Investigator Program when initial studies indicated probable success in obtaining such ambient densities. The major scientific focus of the later work was to be to characterize the behavior of N densities at high latitudes.

  5. First test of BNL electron beam ion source with high current density electron beam

    NASA Astrophysics Data System (ADS)

    Pikin, Alexander; Alessi, James G.; Beebe, Edward N.; Shornikov, Andrey; Mertzig, Robert; Wenander, Fredrik; Scrivens, Richard

    2015-01-01

    A new electron gun with electrostatic compression has been installed at the Electron Beam Ion Source (EBIS) Test Stand at BNL. This is a collaborative effort by BNL and CERN teams with a common goal to study an EBIS with electron beam current up to 10 A, current density up to 10,000 A/cm2 and energy more than 50 keV. Intensive and pure beams of heavy highly charged ions with mass-to-charge ratio < 4.5 are requested by many heavy ion research facilities including NASA Space Radiation Laboratory (NSRL) at BNL and HIE-ISOLDE at CERN. With a multiampere electron gun, the EBIS should be capable of delivering highly charged ions for both RHIC facility applications at BNL and for ISOLDE experiments at CERN. Details of the electron gun simulations and design, and the Test EBIS electrostatic and magnetostatic structures with the new electron gun are presented. The experimental results of the electron beam transmission are given.

  6. Photoelectrolysis of water at high current density - Use of ultraviolet laser excitation

    NASA Technical Reports Server (NTRS)

    Bocarsly, A. B.; Bolts, J. M.; Cummins, P. G.; Wrighton, M. S.

    1977-01-01

    The behavior of TiO2 and SrTiO3 photoanodes in cells for the photoelectrolysis of H2O has been investigated for high-intensity 351-,364-nm excitation from an Ar ion laser. Intensities up to 380 W/sq cm have been used. For TiO2 a small amount of surface decomposition is found after irradiation at high intensity, whereas SrTiO3 undergoes no detectable changes. Current-voltage properties for both electrodes are essentially independent of light intensity up to the level of 380 W/sq cm, and there is little if any change in quantum efficiency for electron flow. Photocurrent densities have been shown to exceed 5 A/sq cm for O2 evolution. Data show that the energy storage rate associated with the SrTiO3 photoelectrolysis can exceed 30 W/sq cm; this represents the highest demonstrated rate of sustained optical-to-chemical energy conversion.

  7. First test of BNL electron beam ion source with high current density electron beam

    SciTech Connect

    Pikin, Alexander Alessi, James G. Beebe, Edward N.; Shornikov, Andrey; Mertzig, Robert; Wenander, Fredrik; Scrivens, Richard

    2015-01-09

    A new electron gun with electrostatic compression has been installed at the Electron Beam Ion Source (EBIS) Test Stand at BNL. This is a collaborative effort by BNL and CERN teams with a common goal to study an EBIS with electron beam current up to 10 A, current density up to 10,000 A/cm{sup 2} and energy more than 50 keV. Intensive and pure beams of heavy highly charged ions with mass-to-charge ratio < 4.5 are requested by many heavy ion research facilities including NASA Space Radiation Laboratory (NSRL) at BNL and HIE-ISOLDE at CERN. With a multiampere electron gun, the EBIS should be capable of delivering highly charged ions for both RHIC facility applications at BNL and for ISOLDE experiments at CERN. Details of the electron gun simulations and design, and the Test EBIS electrostatic and magnetostatic structures with the new electron gun are presented. The experimental results of the electron beam transmission are given.

  8. Influence of High-Current-Density Impulses on the Compression Behavior: Experiments with Iron and a Nickel-Based Alloy

    NASA Astrophysics Data System (ADS)

    Demler, E.; Gerstein, G.; Dalinger, A.; Epishin, A.; Rodman, D.; Nürnberger, F.

    2017-01-01

    Difficulties of processing of high strength and/or brittle materials by plastic deformation, e.g., by forging, require to develop new industrial technologies. In particular, the feasible deformation rates are limited for low-ductile metallic materials. For this reason, processes were investigated to improve the deformability in which electrical impulses are to be applied to lower the yield strength. However, owing to the impulse duration and low current densities, concomitant effects always occur, e.g., as a result of Joule heating. Current developments in power electronics allow now to transmit high currents as short pulses. By reducing the impulse duration and increasing the current density, the plasticity of metallic materials can be correspondingly increased. Using the examples of polycrystalline iron and a single-crystal, nickel-based alloy (PWA 1480), current advances in the development of methods for forming materials by means of high-current-density impulses are demonstrated. For this purpose, appropriate specimens were loaded in compression and, using novel testing equipment, subjected to a current strength of 10 kA with an impulse duration of 2 ms. For a pre-defined strain, the test results show a significant decrease in the compressive stress during the compression test and a significant change in the dislocation distribution following the current impulse treatment.

  9. Influence of High-Current-Density Impulses on the Compression Behavior: Experiments with Iron and a Nickel-Based Alloy

    NASA Astrophysics Data System (ADS)

    Demler, E.; Gerstein, G.; Dalinger, A.; Epishin, A.; Rodman, D.; Nürnberger, F.

    2016-12-01

    Difficulties of processing of high strength and/or brittle materials by plastic deformation, e.g., by forging, require to develop new industrial technologies. In particular, the feasible deformation rates are limited for low-ductile metallic materials. For this reason, processes were investigated to improve the deformability in which electrical impulses are to be applied to lower the yield strength. However, owing to the impulse duration and low current densities, concomitant effects always occur, e.g., as a result of Joule heating. Current developments in power electronics allow now to transmit high currents as short pulses. By reducing the impulse duration and increasing the current density, the plasticity of metallic materials can be correspondingly increased. Using the examples of polycrystalline iron and a single-crystal, nickel-based alloy (PWA 1480), current advances in the development of methods for forming materials by means of high-current-density impulses are demonstrated. For this purpose, appropriate specimens were loaded in compression and, using novel testing equipment, subjected to a current strength of 10 kA with an impulse duration of 2 ms. For a pre-defined strain, the test results show a significant decrease in the compressive stress during the compression test and a significant change in the dislocation distribution following the current impulse treatment.

  10. Deep-blue efficient OLED based on NPB with little efficiency roll-off under high current density

    NASA Astrophysics Data System (ADS)

    Liu, Jian

    2017-03-01

    NPB usually is used as a hole-transport layer in OLED. In fact, it is a standard pure blue-emission material. However, its light-emitting efficiency in OLED is low due to emissive nature of organic material. Herein, a deep-blue OLDE based on NPB was fabricated. The light-emitting efficiency of the device demonstrates a moderate value, and efficiency roll-off is little under high current density. The device demonstrates that the electroplex's emission decreases with increasing electric field intensity.

  11. Fabrication and characterization of high current-density, submicron, NbN/MgO/NbN tunnel junctions

    NASA Technical Reports Server (NTRS)

    Stern, J. A.; Leduc, Henry G.; Judas, A. J.

    1992-01-01

    At near-millimeter wavelengths, heterodyne receivers based on SIS tunnel junctions are the most sensitive available. However, in order to scale these results to submillimeter wavelengths, certain device properties should be scaled. The tunnel-junction's current density should be increased to reduce the RC product. The device's area should be reduced to efficiently couple power from the antenna to the mixer. Finally, the superconductor used should have a large energy gap to minimize RF losses. Most SIS mixers use Nb or Pb-alloy tunnel junctions; the gap frequency for these materials is approximately 725 GHz. Above the gap frequency, these materials exhibit losses similar to those in a normal metal. The gap frequency in NbN films is as-large-as 1440 GHz. Therefore, we have developed a process to fabricate small area (down to 0.13 sq microns), high current density, NbN/MgO/NbN tunnel junctions.

  12. High current density ion beam obtained by a transition to a highly focused state in extremely low-energy region.

    PubMed

    Hirano, Y; Kiyama, S; Fujiwara, Y; Koguchi, H; Sakakita, H

    2015-11-01

    A high current density (≈3 mA/cm(2)) hydrogen ion beam source operating in an extremely low-energy region (E(ib) ≈ 150-200 eV) has been realized by using a transition to a highly focused state, where the beam is extracted from the ion source chamber through three concave electrodes with nominal focal lengths of ≈350 mm. The transition occurs when the beam energy exceeds a threshold value between 145 and 170 eV. Low-level hysteresis is observed in the transition when E(ib) is being reduced. The radial profiles of the ion beam current density and the low temperature ion current density can be obtained separately using a Faraday cup with a grid in front. The measured profiles confirm that more than a half of the extracted beam ions reaches the target plate with a good focusing profile with a full width at half maximum of ≈3 cm. Estimation of the particle balances in beam ions, the slow ions, and the electrons indicates the possibility that the secondary electron emission from the target plate and electron impact ionization of hydrogen may play roles as particle sources in this extremely low-energy beam after the compensation of beam ion space charge.

  13. High current density ion beam obtained by a transition to a highly focused state in extremely low-energy region

    SciTech Connect

    Hirano, Y. E-mail: hirano.yoichi@phys.cst.nihon-u.ac.jp; Kiyama, S.; Koguchi, H.; Fujiwara, Y.; Sakakita, H.

    2015-11-15

    A high current density (≈3 mA/cm{sup 2}) hydrogen ion beam source operating in an extremely low-energy region (E{sub ib} ≈ 150–200 eV) has been realized by using a transition to a highly focused state, where the beam is extracted from the ion source chamber through three concave electrodes with nominal focal lengths of ≈350 mm. The transition occurs when the beam energy exceeds a threshold value between 145 and 170 eV. Low-level hysteresis is observed in the transition when E{sub ib} is being reduced. The radial profiles of the ion beam current density and the low temperature ion current density can be obtained separately using a Faraday cup with a grid in front. The measured profiles confirm that more than a half of the extracted beam ions reaches the target plate with a good focusing profile with a full width at half maximum of ≈3 cm. Estimation of the particle balances in beam ions, the slow ions, and the electrons indicates the possibility that the secondary electron emission from the target plate and electron impact ionization of hydrogen may play roles as particle sources in this extremely low-energy beam after the compensation of beam ion space charge.

  14. Microstructural Evolution and Migration Mechanism Study in a Eutectic Sn-37Pb Lap Joint Under High Current Density

    NASA Astrophysics Data System (ADS)

    Zhang, Zhihao; Cao, Huijun; Yang, Haifeng; Xiao, Yong; Li, Mingyu; Yu, Yuxi; Yao, Shun

    2017-08-01

    The microstructural evolution in eutectic Sn-37Pb solder under high current density seriously threatens the reliability of solder interconnections, but atomic electromigration has often been confused with thermomigration. In this paper, after decoupling the effect of the non-uniform temperature distribution in a Cu/Sn-37Pb/Cu lap joint from the current stress, the microstructural evolution was investigated under an average current density of 1.84 × 104 A cm-2 for 0-24 h. The decomposition and recombination of the Pb-rich phase occurred at the cathode and the anode, respectively. The corresponding migration mechanism was proposed from the viewpoint of energy and was explained by the interactions among the potential energies of ripening, electron wind force, and back stress. Our study may be helpful for understanding the migration mechanism and reliability of eutectic two-phase solder joints and provides supporting data for interpreting the acceleration tests of Sn-37Pb solder joints under electromigration.

  15. Very High Current Density Nb/AlN/Nb Tunnel Junctions for Low-Noise Submillimeter Mixers

    NASA Technical Reports Server (NTRS)

    Kawamura, Jonathan; Miller, David; Chen, Jian; Zmuidzinas, Jonas; Bumble, Bruce; LeDuc, Henry G.; Stern, Jeff A.

    2000-01-01

    We have fabricated and tested submillimeter-wave superconductor-insulator-superconductor (SIS) mixers using very high current density Nb/AlN/Nb tunnel junctions (J(sub c) approximately equal 30 kA/sq cm) . The junctions have low resistance-area products (R(sub N)A approximately 5.6 Omega.sq micron), good subgap to normal resistance ratios R(sub sg)/R(sub N) approximately equal 10, and good run-to-run reproducibility. From Fourier transform spectrometer measurements, we infer that omega.R(sub N)C = 1 at 270 GHz. This is a factor of 2.5 improvement over what is generally available with Nb/AlO(x)/Nb junctions suitable for low-noise mixers. The AlN-barrier junctions are indeed capable of low-noise operation: we measure an uncorrected receiver noise temperature of T(sub RX) = 110 K (DSB) at 533 GHz for an unoptimized device. In addition to providing wider bandwidth operation at lower frequencies, the AlN-barrier junctions will considerably improve the performance of THz SIS mixers by reducing RF loss in the tuning circuits.

  16. A HIgh Current Density Low Cost Niobium 3 Tin Titanium Doped Conductor Utilizing A Novel Internal Tin Process

    SciTech Connect

    Bruce A Zeitlin

    2005-02-23

    An internal tin conductor has been developed using a Mono Element Internal Tin (MEIT) with an integral Nb barrier surrounding the Nb filaments. High current densities of 3000 A/mm2+ at 12 T and 1800 A/mm2 at 15 T have been achieved in conductors as small as 0.152 mm with the use of Nb7.5Ta filaments and Ti in the Sn core. In contrast, conductors with pure Nb and Ti in the Sn achieved 2700 A/mm2 at 12 T. Two internal fins, developed and patented on the project, were introduced into the filament array and reduced the effective filament diameter (Deff) by 38%. Additional fins will further reduce Deff The conductor was produced from 152.4 mm diameter billets to produce wire as small as 0.152 mm. The process promises be scaleable to 304 mm diameter billets yielding wire of 0.304 mm diameter. The MEIT process wire was easy to draw with relatively few breaks. The cost of this conductor in large production quantities based on the cost model presented could meet the 1.5 $/kilo amp meter(KAM) target of the HEP community

  17. Characterization and Performance of a High-Current-Density Ion Implanter with Magnetized Hollow-Cathode Plasma Source

    NASA Astrophysics Data System (ADS)

    Falkenstein, Zoran; Rej, Donald; Gavrilov, Nikolai

    1998-10-01

    In a collaboration between the Institute of Electrophysics (IEP) and the Los Alamos National Laboratory (LANL), the IEP has developed an industrial scalable, high-power, large-area ion source for the surface modification of materials. The plasma source of the ion beam source can be described as a pulsed glow discharge with a cold, hollow-cathode in a weak magnetic field. Extraction and focusing of positive ions by an acceleration and ion-optical plate system renders the generation of a homogeneous, large-area ion beam with an averaged total ion current of up to 50 mA at acceleration voltages of up to 50 kV. The principle set-up of the ion beam source as well as some electrical characteristics (gas discharge current and the extracted ion beam current) are presented for a lab-scale prototype. Measurements of the radial ion current density profiles within the ion beam for various discharge parameters, as well as results on surface modification by ion implantation of nitrogen into aluminum and chromium are presented. Finally, a comparison of the applied ion dose with the retained ion doses is given.

  18. Ti/Pd/Ag Contacts to n-Type GaAs for High Current Density Devices

    NASA Astrophysics Data System (ADS)

    Huo, Pengyun; Rey-Stolle, Ignacio

    2016-06-01

    The metallization stack Ti/Pd/Ag on n-type Si has been readily used in solar cells due to its low metal/semiconductor specific contact resistance, very high sheet conductance, bondability, long-term durability, and cost-effectiveness. In this study, the use of Ti/Pd/Ag metallization on n-type GaAs is examined, targeting electronic devices that need to handle high current densities and with grid-like contacts with limited surface coverage (i.e., solar cells, lasers, or light emitting diodes). Ti/Pd/Ag (50 nm/50 nm/1000 nm) metal layers were deposited on n-type GaAs by electron beam evaporation and the contact quality was assessed for different doping levels (from 1.3 × 1018 cm-3 to 1.6 × 1019 cm-3) and annealing temperatures (from 300°C to 750°C). The metal/semiconductor specific contact resistance, metal resistivity, and the morphology of the contacts were studied. The results show that samples doped in the range of 1018 cm-3 had Schottky-like I- V characteristics and only samples doped 1.6 × 1019 cm-3 exhibited ohmic behavior even before annealing. For the ohmic contacts, increasing annealing temperature causes a decrease in the specific contact resistance ( ρ c,Ti/Pd/Ag ~ 5 × 10-4 Ω cm2). In regard to the metal resistivity, Ti/Pd/Ag metallization presents a very good metal conductivity for samples treated below 500°C ( ρ M,Ti/Pd/Ag ~ 2.3 × 10-6 Ω cm); however, for samples treated at 750°C, metal resistivity is strongly degraded due to morphological degradation and contamination in the silver overlayer. As compared to the classic AuGe/Ni/Au metal system, the Ti/Pd/Ag system shows higher metal/semiconductor specific contact resistance and one order of magnitude lower metal resistivity.

  19. Growth and characterization of high current density, high-speed InAs/AlSb resonant tunneling diodes

    NASA Technical Reports Server (NTRS)

    Soderstrom, J. R.; Brown, E. R.; Parker, C. D.; Mahoney, L. J.; Yao, J. Y.

    1991-01-01

    InAs/AlSb double-barrier resonant tunneling diodes with peak current densities up to 370,000 A/sq cm and high peak-to-valley current ratios of 3.2 at room temperature have been fabricated. The peak current density is well-explained by a stationary-state transport model with the two-band envelope function approximation. The valley current density predicted by this model is less than the experimental value by a factor that is typical of the discrepancy found in other double-barrier structures. It is concluded that threading dislocations are largely inactive in the resonant tunneling process.

  20. Growth and characterization of high current density, high-speed InAs/AlSb resonant tunneling diodes

    NASA Technical Reports Server (NTRS)

    Soderstrom, J. R.; Brown, E. R.; Parker, C. D.; Mahoney, L. J.; Yao, J. Y.

    1991-01-01

    InAs/AlSb double-barrier resonant tunneling diodes with peak current densities up to 370,000 A/sq cm and high peak-to-valley current ratios of 3.2 at room temperature have been fabricated. The peak current density is well-explained by a stationary-state transport model with the two-band envelope function approximation. The valley current density predicted by this model is less than the experimental value by a factor that is typical of the discrepancy found in other double-barrier structures. It is concluded that threading dislocations are largely inactive in the resonant tunneling process.

  1. Enhanced leaf nitrogen status stabilizes omnivore population density.

    PubMed

    Liman, Anna-Sara; Dalin, Peter; Björkman, Christer

    2017-01-01

    Plant traits can mediate the strength of interactions between omnivorous predators and their prey through density effects and changes in the omnivores' trophic behavior. In this study, we explored the established assumption that enhanced nutrient status in host plants strengthens the buffering effect of plant feeding for omnivorous predators, i.e., prevents rapid negative population growth during prey density decline and thereby increases and stabilizes omnivore population density. We analyzed 13 years of field data on population densities of a heteropteran omnivore on Salix cinerea stands, arranged along a measured leaf nitrogen gradient and found a 195 % increase in omnivore population density and a 63 % decrease in population variability with an increase in leaf nitrogen status from 26 to 40 mgN × g(-1). We recreated the leaf nitrogen gradient in a greenhouse experiment and found, as expected, that increasing leaf nitrogen status enhanced omnivore performance but reduced per capita prey consumption. Feeding on high nitrogen status host plants can potentially decouple omnivore-prey population dynamics and allow omnivores to persist and function effectively at low prey densities to provide "background level" control of insect herbivores. This long-term effect is expected to outweigh the short-term effect on per capita prey consumption-resulting in a net increase in population predation rates with increasing leaf nitrogen status. Conservation biological control of insect pests that makes use of omnivore background control could, as a result, be manipulated via management of crop nitrogen status.

  2. Formation of Mosaic Silicon Oxide Structure during Metal-Assisted Electrochemical Etching of Silicon at High Current Density

    NASA Astrophysics Data System (ADS)

    Cao, Dao Tran; Anh, Cao Tuan; Ngan, Luong Truc Quynh

    2016-05-01

    We have used constant-current, metal-assisted electrochemical etching of silicon in HF/H2O2/ethanol electrolyte to fabricate porous silicon. We found that, at large enough current density, the sponge-like porous silicon structure is replaced by a mosaic structure, which includes islands of various shapes emerging between trenches that have been etched downward. Energy-dispersive x-ray analysis showed that the surface of the mosaic pieces was covered with silicon oxide, while little silicon oxide developed on the surface of trenches. We suggest that the appearance of the mosaic structure can be explained by the increase in the oxidation rate of silicon when the anodic current density increases, combined with no change in the dissolution rate of silicon oxide into the solution. Consequently, above a certain value of anodic current density, there is sufficient residual silicon oxide on the etched surface to create a continuous thin film. However, if the silicon oxide layer is too thick (e.g., due to too high anodic current density or too long etching time), it will become cracked (formation of mosaic pieces), likely due to differences in thermal expansion coefficient between the amorphous silicon oxide layer and crystalline silicon substrate. The oxide is cracked at locations with many defects, and the cracks reveal the silicon substrate. Therefore, at the locations where cracks occur, etching will go sideways and downward, creating trenches.

  3. Aging characteristics of blue InGaN micro-light emitting diodes at an extremely high current density of 3.5 kA cm-2

    NASA Astrophysics Data System (ADS)

    Tian, Pengfei; Althumali, Ahmad; Gu, Erdan; Watson, Ian M.; Dawson, Martin D.; Liu, Ran

    2016-04-01

    The aging characteristics of blue InGaN micro-light emitting diodes (micro-LEDs) with different sizes have been studied at an extremely high current density 3.5 kA cm-2 for emerging micro-LED applications including visible light communication (VLC), micro-LED pumped organic lasers and optogenetics. The light output power of micro-LEDs first increases and then decreases due to the competition of Mg activation in p-GaN layer and defect generation in the active region. The smaller micro-LEDs show less light output power degradation compared with larger micro-LEDs, which is attributed to the lower junction temperature of smaller micro-LEDs. It is found that the high current density without additional junction temperature cannot induce significant micro-LED degradation at room temperature but the combination of the high current density and high junction temperature leads to strong degradation. Furthermore, the cluster LEDs, composed of a micro-LED array, have been developed with both high light output power and less light output degradation for micro-LED applications in solid state lighting and VLC.

  4. Estimated global nitrogen deposition using NO2 column density

    USGS Publications Warehouse

    Lu, Xuehe; Jiang, Hong; Zhang, Xiuying; Liu, Jinxun; Zhang, Zhen; Jin, Jiaxin; Wang, Ying; Xu, Jianhui; Cheng, Miaomiao

    2013-01-01

    Global nitrogen deposition has increased over the past 100 years. Monitoring and simulation studies of nitrogen deposition have evaluated nitrogen deposition at both the global and regional scale. With the development of remote-sensing instruments, tropospheric NO2 column density retrieved from Global Ozone Monitoring Experiment (GOME) and Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) sensors now provides us with a new opportunity to understand changes in reactive nitrogen in the atmosphere. The concentration of NO2 in the atmosphere has a significant effect on atmospheric nitrogen deposition. According to the general nitrogen deposition calculation method, we use the principal component regression method to evaluate global nitrogen deposition based on global NO2 column density and meteorological data. From the accuracy of the simulation, about 70% of the land area of the Earth passed a significance test of regression. In addition, NO2 column density has a significant influence on regression results over 44% of global land. The simulated results show that global average nitrogen deposition was 0.34 g m−2 yr−1 from 1996 to 2009 and is increasing at about 1% per year. Our simulated results show that China, Europe, and the USA are the three hotspots of nitrogen deposition according to previous research findings. In this study, Southern Asia was found to be another hotspot of nitrogen deposition (about 1.58 g m−2 yr−1 and maintaining a high growth rate). As nitrogen deposition increases, the number of regions threatened by high nitrogen deposits is also increasing. With N emissions continuing to increase in the future, areas whose ecosystem is affected by high level nitrogen deposition will increase.

  5. A new latch-free LIGBT on SOI with very high current density and low drive voltage

    NASA Astrophysics Data System (ADS)

    Olsson, J.; Vestling, L.; Eklund, K.-H.

    2016-01-01

    A new latch-free LIGBT on SOI is presented. The new device combines advantages from both LDMOS as well as LIGBT technologies; high breakdown voltage, high drive current density, low control voltages, at the same time eliminating latch-up problems. The new LIGBT has the unique property of independent scaling of the input control device, i.e. LDMOS, and the output part of the device, i.e. the p-n-p part. This allows for additional freedom in designing and optimizing the device properties. Breakdown voltage of over 200 V, on-state current density over 3 A/mm, specific on-resistance below 190 mΩ mm2, and latch-free operation is demonstrated.

  6. Electrodeposition of hierarchically structured three-dimensional nickel–iron electrodes for efficient oxygen evolution at high current densities

    PubMed Central

    Lu, Xunyu; Zhao, Chuan

    2015-01-01

    Large-scale industrial application of electrolytic splitting of water has called for the development of oxygen evolution electrodes that are inexpensive, robust and can deliver large current density (>500 mA cm−2) at low applied potentials. Here we show that an efficient oxygen electrode can be developed by electrodepositing amorphous mesoporous nickel–iron composite nanosheets directly onto macroporous nickel foam substrates. The as-prepared oxygen electrode exhibits high catalytic activity towards water oxidation in alkaline solutions, which only requires an overpotential of 200 mV to initiate the reaction, and is capable of delivering current densities of 500 and 1,000 mA cm−2 at overpotentials of 240 and 270 mV, respectively. The electrode also shows prolonged stability against bulk water electrolysis at large current. Collectively, the as-prepared three-dimensional structured electrode is the most efficient oxygen evolution electrode in alkaline electrolytes reported to the best of our knowledge, and can potentially be applied for industrial scale water electrolysis. PMID:25776015

  7. Highly Stable Three-Dimensional Porous Nickel-Iron Nitride Nanosheets for Full Water Splitting at High Current Densities.

    PubMed

    Yan, Feng; Wang, Yue; Li, Kaiyue; Zhu, Chunling; Gao, Peng; Li, Chunyan; Zhang, Xitian; Chen, Yujin

    2017-07-26

    A noble-metal-free and highly efficient bifunctional catalyst for overall water splitting is greatly desirable to generate clean and sustainable energy carriers such as hydrogen, but enormous challenges remain. Herein, porous interconnected iron-nickel nitride nanosheets are designed and grown on carbon fiber cloth (FeNi-N/CFC); combining a facile electrodeposition method and in situ nitriding process. The as-synthesized FeNi-N/CFC, with a low mass loading of 0.25 mg cm(-2) , exhibits excellent catalytic activities for both the oxygen evolution reaction (OER) with 20 mA cm(-2) at an overpotential (η) of 232 mV and also the hydrogen evolution reaction (HER) with 10 mA cm(-2) at η=106 mV. As a bifunctional electrocatalyst for overall water splitting FeNi-N/CFC only requires a cell voltage of 1.55 V to drive a current density (j) of 10 mA cm(-2) and shows robust long-term durability at j>360 mA cm(-2) with a negligible change in current density over 60 h; revealing its promising application in commercial electrolyzers. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Power-Efficient, High-Current-Density, Long-Life Thermionic Cathode Developed for Microwave Amplifier Applications

    NASA Technical Reports Server (NTRS)

    Wintucky, Edwin G.

    2002-01-01

    A power-efficient, miniature, easily manufactured, reservoir-type barium-dispenser thermionic cathode has been developed that offers the significant advantages of simultaneous high electron-emission current density (>2 A/sq cm) and very long life (>100,000 hr of continuous operation) when compared with the commonly used impregnated-type barium-dispenser cathodes. Important applications of this cathode are a wide variety of microwave and millimeter-wave vacuum electronic devices, where high output power and reliability (long life) are essential. We also expect it to enable the practical development of higher purveyance electron guns for lower voltage and more reliable device operation. The low cathode heater power and reduced size and mass are expected to be particularly beneficial in traveling-wave-tube amplifiers (TWTA's) for space communications, where future NASA mission requirements include smaller onboard spacecraft systems, higher data transmission rates (high frequency and output power) and greater electrical efficiency.

  9. Coherent Interlayer Tunneling and Negative Differential Resistance with High Current Density in Double Bilayer Graphene-WSe2 Heterostructures.

    PubMed

    Burg, G William; Prasad, Nitin; Fallahazad, Babak; Valsaraj, Amithraj; Kim, Kyounghwan; Taniguchi, Takashi; Watanabe, Kenji; Wang, Qingxiao; Kim, Moon J; Register, Leonard F; Tutuc, Emanuel

    2017-06-14

    We demonstrate gate-tunable resonant tunneling and negative differential resistance between two rotationally aligned bilayer graphene sheets separated by bilayer WSe2. We observe large interlayer current densities of 2 and 2.5 μA/μm(2) and peak-to-valley ratios approaching 4 and 6 at room temperature and 1.5 K, respectively, values that are comparable to epitaxially grown resonant tunneling heterostructures. An excellent agreement between theoretical calculations using a Lorentzian spectral function for the two-dimensional (2D) quasiparticle states, and the experimental data indicates that the interlayer current stems primarily from energy and in-plane momentum conserving 2D-2D tunneling, with minimal contributions from inelastic or non-momentum-conserving tunneling. We demonstrate narrow tunneling resonances with intrinsic half-widths of 4 and 6 meV at 1.5 and 300 K, respectively.

  10. Parametric study of a high current-density EBIS Charge Breeder regarding Two Stream plasma Instability (TSI)

    NASA Astrophysics Data System (ADS)

    Shornikov, Andrey; Mertzig, Robert; Breitenfeldt, Martin; Lombardi, Alessandra; Wenander, Fredrik; Pikin, Alexander

    2016-06-01

    In this paper we report on our results from the design study of an advanced Electron Beam Ion Source (EBIS) based Charge Breeder (ECB). The ECB should fulfill the requirements of the HIE-ISOLDE upgrade, and if possible be adapted for ion injection into TSR@ISOLDE, as well as serve as an early prototype of a future EURISOL ECB. Fulfilling the HIE-ISOLDE/TSR@ISOLDE specifications requires simultaneous increase in electron beam energy, current and current density in order to provide the requested beams with proper charge state, high intensity and with a specified pulse repetition rate. We have carried out a study on the technical requirements of the ECB. The obtained parameters were optimized to comply with technical limitations arising from the electron beam technology and plasma physics in an ECB.

  11. High current ion source

    DOEpatents

    Brown, Ian G.; MacGill, Robert A.; Galvin, James E.

    1990-01-01

    An ion source utilizing a cathode and anode for producing an electric arc therebetween. The arc is sufficient to vaporize a portion of the cathode to form a plasma. The plasma leaves the generation region and expands through another regon. The density profile of the plasma may be flattened using a magnetic field formed within a vacuum chamber. Ions are extracted from the plasma to produce a high current broad on beam.

  12. Nanofiber-deposited porous platinum enables glucose fuel cell anodes with high current density in body fluids

    NASA Astrophysics Data System (ADS)

    Frei, Maxi; Erben, Johannes; Martin, Julian; Zengerle, Roland; Kerzenmacher, Sven

    2017-09-01

    The poisoning of platinum anodes by body-fluid constituents such as amino acids is currently the main hurdle preventing the application of abiotic glucose fuel cells as battery-independent power supply for medical implants. We present a novel anode material that enables continuous operation of glucose oxidation anodes in horse serum for at least 30 days at a current density of (7.2 ± 1.9) μA cm-2. The fabrication process is based on the electro-deposition of highly porous platinum onto a 3-dimensional carbon nanofiber support, leading to approximately 2-fold increased electrode roughness factors (up to 16500 ± 2300). The material's superior performance is not only related to its high specific surface area, but also to an improved catalytic activity and/or poisoning resistance. Presumably, this results from the micro- and nanostructure of the platinum deposits. This represents a major step forward in the development of implantable glucose fuel cells based on long-term stable platinum electrodes.

  13. Degradation of solid oxide cells during co-electrolysis of steam and carbon dioxide at high current densities

    NASA Astrophysics Data System (ADS)

    Tao, Youkun; Ebbesen, Sune Dalgaard; Mogensen, Mogens Bjerg

    2016-10-01

    In this work, the durability of Ni-YSZ based solid oxide cells was investigated during co-electrolysis of steam and carbon dioxide (45% H2O + 45% CO2 + 10% H2) at current density of -1.5 or -2.0 A cm-2. The cell consists of ∼300 μm Ni-YSZ support, ∼10 μm Ni-YSZ electrode, ∼10 μm YSZ electrolyte and ∼15 μm LSM-YSZ oxygen electrode. The gas conversion was 45% at -1.5 A cm-2 and 60% at -2.0 A cm-2, and the operating durations were up to 700 h. The detailed electrochemical analysis revealed significant increase of the ohmic resistance, oxide ion transport resistance in the Ni-YSZ composite electrodes and the electrochemical reaction resistance at the Ni-YSZ triple-phase boundaries. The performance degradation is mainly ascribed to the microstructural change in the Ni-YSZ electrode close to the YSZ electrolyte, including the percolation loss of Ni, the contact loss between Ni and YSZ electrolyte and the decomposition of YSZ close to Ni-YSZ|YSZ interface. The electrochemical performance and the microstructure of the oxygen electrode were found to be relatively stable.

  14. A novel BEM-LIGBT with high current density on thin SOI layer for 600 V HVIC

    NASA Astrophysics Data System (ADS)

    Zhu, Jing; Sun, Weifeng; Chen, Jian; Lu, Shengli; Zhang, Sen; Su, Wei

    2014-10-01

    A novel Body Effect Modulation Lateral Insulated Gate Bipolar Transistor (BEM-LIGBT) on the thin SOI layer featuring with a metal resistor connected with the body region and the n plus region without adding extra mask steps is experimentally proposed in this paper. In the proposed device structure, the electron current is the dominant component of the total current and it can be improved by increasing the resistance of the metal resistor, which is verified by the theoretical derivation and numerous TCAD simulations. The total current density of the proposed high voltage (above 690 V) BEM-LIGBT is increased by about 65% at VGE = 5 V, compared with the conventional structure on the same SOI layer. In addition, the BEM-LIGBT is successfully used in the level-shift circuit for 600 V high voltage gate drive integrated circuit (HVIC). The width of the dV/dt noise pulse in the circuit is decreased by about 45% by using the BEM-LIGBT.

  15. Suppression of external quantum efficiency roll-off of nanopatterned organic-light emitting diodes at high current densities

    SciTech Connect

    Kuwae, Hiroyuki; Kasahara, Takashi; Nitta, Atsushi; Yoshida, Kou; Inoue, Munetomo; Matsushima, Toshinori; Adachi, Chihaya; Shoji, Shuichi; Mizuno, Jun

    2015-10-21

    We developed organic light-emitting diodes (OLEDs) with nanopatterned current flow regions using electron-beam lithography with the aim of suppressing singlet–polaron annihilation (SPA). Nanopatterns composed of lines and circles were used in the current flow regions of nano-line and nano-dot OLEDs, respectively. Excitons partially escape from the current flow regions where SPA takes place. As such, current densities where external quantum efficiencies were half of their initial values (J{sub 0}) increased as line width and circle diameter were decreased to close to the exciton diffusion length. Circles were more efficient at enhancing exciton escape and increasing J{sub 0} than lines. The J{sub 0} increase in the nano-dot OLEDs containing nanopatterned circles with a diameter of 50 nm was approximately 41-fold that of a conventional OLED with a current flow region of 4 mm{sup 2}. The dependence of J{sub 0} on the size and shape of the nanopatterns was well explained by an SPA model that considered exciton diffusion. Nanopatterning of OLEDs is a feasible method of obtaining large J{sub 0}.

  16. Generation of High Current Densities by Pure Cultures of Anode-Respiring Geoalkalibacter spp. under Alkaline and Saline Conditions in Microbial Electrochemical Cells

    PubMed Central

    Badalamenti, Jonathan P.; Krajmalnik-Brown, Rosa; Torres, César I.

    2013-01-01

    ABSTRACT Anode-respiring bacteria (ARB) generate electric current in microbial electrochemical cells (MXCs) by channeling electrons from the oxidation of organic substrates to an electrode. Production of high current densities by monocultures in MXCs has resulted almost exclusively from the activity of Geobacter sulfurreducens, a neutrophilic freshwater Fe(III)-reducing bacterium and the highest-current-producing member documented for the Geobacteraceae family of the Deltaproteobacteria. Here we report high current densities generated by haloalkaliphilic Geoalkalibacter spp., thus broadening the capability for high anode respiration rates by including other genera within the Geobacteraceae. In this study, acetate-fed pure cultures of two related Geoalkalibacter spp. produced current densities of 5.0 to 8.3 and 2.4 to 3.3 A m−2 under alkaline (pH 9.3) and saline (1.7% NaCl) conditions, respectively. Chronoamperometric studies of halophilic Glk. subterraneus DSM 23483 and alkaliphilic Glk. ferrihydriticus DSM 17813 suggested that cells performed long-range electron transfer through electrode-attached biofilms and not through soluble electron shuttles. Glk. ferrihydriticus also oxidized ethanol directly to produce current, with maximum current densities of 5.7 to 7.1 A m−2 and coulombic efficiencies of 84 to 95%. Cyclic voltammetry (CV) elicited a sigmoidal response with characteristic onset, midpoint, and saturation potentials, while CV performed in the absence of an electron donor suggested the involvement of redox molecules in the biofilm that were limited by diffusion. These results matched those previously reported for actively respiring Gb. sulfurreducens biofilms producing similar current densities (~5 to 9 A m−2). PMID:23631915

  17. Efficiency roll-off suppression in organic light-emitting diodes using size-tunable bimetallic bowtie nanoantennas at high current densities

    NASA Astrophysics Data System (ADS)

    Zhao, Yukun; Yun, Feng; Huang, Yi; Wu, Zhaoxin; Li, Yufeng; Jiao, Bo; Feng, Lungang; Li, Sanfeng; Ding, Wen; Zhang, Ye

    2016-07-01

    Size-tunable bimetallic bowtie nanoantennas have been utilized to suppress the efficiency roll-off characteristics in organic light-emitting diodes (OLEDs) using both the numerical and experimental approaches. The resonant range can be widened by the strong dual-atomic couplings in bimetallic bowtie nanoantennas. Compared with the green OLED with conventional bowtie nanoantennas at a high current density of 800 mA/cm2, the measured efficiency roll-off ratio of the OLED with size-modulated bowtie nanoantennas is decreased from 53.2% to 41.8%, and the measured current efficiency is enhanced by 29.9%. When the size-modulated bowtie nanoantennas are utilized in blue phosphorescent OLEDs, the experimental roll-off ratio is suppressed from 43.6% to 25.9% at 250 mA/cm2, and the measured current efficiency is also enhanced significantly. It is proposed that the efficiency roll-off suppression is mainly related to the enhanced localized surface plasmon effect, which leads to a shorter radiative lifetime.

  18. High current density GaAs/Si rectifying heterojunction by defect free Epitaxial Lateral overgrowth on Tunnel Oxide from nano-seed

    NASA Astrophysics Data System (ADS)

    Renard, Charles; Molière, Timothée; Cherkashin, Nikolay; Alvarez, José; Vincent, Laetitia; Jaffré, Alexandre; Hallais, Géraldine; Connolly, James Patrick; Mencaraglia, Denis; Bouchier, Daniel

    2016-05-01

    Interest in the heteroepitaxy of GaAs on Si has never failed in the last years due to the potential for monolithic integration of GaAs-based devices with Si integrated circuits. But in spite of this effort, devices fabricated from them still use homo-epitaxy only. Here we present an epitaxial technique based on the epitaxial lateral overgrowth of micrometer scale GaAs crystals on a thin SiO2 layer from nanoscale Si seeds. This method permits the integration of high quality and defect-free crystalline GaAs on Si substrate and provides active GaAs/Si heterojunctions with efficient carrier transport through the thin SiO2 layer. The nucleation from small width openings avoids the emission of misfit dislocations and the formation of antiphase domains. With this method, we have experimentally demonstrated for the first time a monolithically integrated GaAs/Si diode with high current densities of 10 kA.cm‑2 for a forward bias of 3.7 V. This epitaxial technique paves the way to hybrid III–V/Si devices that are free from lattice-matching restrictions, and where silicon not only behaves as a substrate but also as an active medium.

  19. Non-destructive mapping of doping and structural composition of MOVPE-grown high current density resonant tunnelling diodes through photoluminescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Jacobs, K. J. P.; Stevens, B. J.; Mukai, T.; Ohnishi, D.; Hogg, R. A.

    2015-05-01

    We report on photoluminescence (PL) characterisation of metal-organic vapour phase epitaxy (MOVPE) grown high current density (~700 kA/cm2) InGaAs/AlAs/InP based resonant tunnelling diodes (RTDs) for terahertz emission. The PL mapping we describe allows important information about doping level and uniformity, ternary alloy composition and uniformity, and uniformity of quantum well thickness to be deduced. PL as a function of doping concentration is studied for InGaAs test layers at low temperatures and correlated to secondary-ion mass spectroscopy (SIMS) and electrochemical capacitance-voltage (eCV) profiling to provide non-destructive mapping of doping over the wafer. For the RTD structures, we utilise eCV as a selective etch tool to identify the origin of low temperature PL emission from the quantum well (QW) and the highly doped contact layers. PL mapping of the RTD wafer at low temperatures is shown to allow the assessment of variations in InGaAs alloy composition and QW thickness. Details of the growth process are discussed and confirmed using high resolution X-ray diffraction (HRXRD) crystallography. The rapid non-destructive characterisation and wafer mapping of these structures promises a route to future growth optimisation of such structures.

  20. High current density GaAs/Si rectifying heterojunction by defect free Epitaxial Lateral overgrowth on Tunnel Oxide from nano-seed

    PubMed Central

    Renard, Charles; Molière, Timothée; Cherkashin, Nikolay; Alvarez, José; Vincent, Laetitia; Jaffré, Alexandre; Hallais, Géraldine; Connolly, James Patrick; Mencaraglia, Denis; Bouchier, Daniel

    2016-01-01

    Interest in the heteroepitaxy of GaAs on Si has never failed in the last years due to the potential for monolithic integration of GaAs-based devices with Si integrated circuits. But in spite of this effort, devices fabricated from them still use homo-epitaxy only. Here we present an epitaxial technique based on the epitaxial lateral overgrowth of micrometer scale GaAs crystals on a thin SiO2 layer from nanoscale Si seeds. This method permits the integration of high quality and defect-free crystalline GaAs on Si substrate and provides active GaAs/Si heterojunctions with efficient carrier transport through the thin SiO2 layer. The nucleation from small width openings avoids the emission of misfit dislocations and the formation of antiphase domains. With this method, we have experimentally demonstrated for the first time a monolithically integrated GaAs/Si diode with high current densities of 10 kA.cm−2 for a forward bias of 3.7 V. This epitaxial technique paves the way to hybrid III–V/Si devices that are free from lattice-matching restrictions, and where silicon not only behaves as a substrate but also as an active medium. PMID:27142097

  1. High current density GaAs/Si rectifying heterojunction by defect free Epitaxial Lateral overgrowth on Tunnel Oxide from nano-seed.

    PubMed

    Renard, Charles; Molière, Timothée; Cherkashin, Nikolay; Alvarez, José; Vincent, Laetitia; Jaffré, Alexandre; Hallais, Géraldine; Connolly, James Patrick; Mencaraglia, Denis; Bouchier, Daniel

    2016-05-04

    Interest in the heteroepitaxy of GaAs on Si has never failed in the last years due to the potential for monolithic integration of GaAs-based devices with Si integrated circuits. But in spite of this effort, devices fabricated from them still use homo-epitaxy only. Here we present an epitaxial technique based on the epitaxial lateral overgrowth of micrometer scale GaAs crystals on a thin SiO2 layer from nanoscale Si seeds. This method permits the integration of high quality and defect-free crystalline GaAs on Si substrate and provides active GaAs/Si heterojunctions with efficient carrier transport through the thin SiO2 layer. The nucleation from small width openings avoids the emission of misfit dislocations and the formation of antiphase domains. With this method, we have experimentally demonstrated for the first time a monolithically integrated GaAs/Si diode with high current densities of 10 kA.cm(-2) for a forward bias of 3.7 V. This epitaxial technique paves the way to hybrid III-V/Si devices that are free from lattice-matching restrictions, and where silicon not only behaves as a substrate but also as an active medium.

  2. Efficiency roll-off suppression in organic light-emitting diodes using size-tunable bimetallic bowtie nanoantennas at high current densities

    SciTech Connect

    Zhao, Yukun; Yun, Feng Li, Yufeng; Feng, Lungang; Ding, Wen; Huang, Yi; Wu, Zhaoxin; Jiao, Bo; Li, Sanfeng; Zhang, Ye

    2016-07-04

    Size-tunable bimetallic bowtie nanoantennas have been utilized to suppress the efficiency roll-off characteristics in organic light-emitting diodes (OLEDs) using both the numerical and experimental approaches. The resonant range can be widened by the strong dual-atomic couplings in bimetallic bowtie nanoantennas. Compared with the green OLED with conventional bowtie nanoantennas at a high current density of 800 mA/cm{sup 2}, the measured efficiency roll-off ratio of the OLED with size-modulated bowtie nanoantennas is decreased from 53.2% to 41.8%, and the measured current efficiency is enhanced by 29.9%. When the size-modulated bowtie nanoantennas are utilized in blue phosphorescent OLEDs, the experimental roll-off ratio is suppressed from 43.6% to 25.9% at 250 mA/cm{sup 2}, and the measured current efficiency is also enhanced significantly. It is proposed that the efficiency roll-off suppression is mainly related to the enhanced localized surface plasmon effect, which leads to a shorter radiative lifetime.

  3. High current density and longtime stable field electron transfer from large-area densely arrayed graphene nanosheet-carbon nanotube hybrids.

    PubMed

    Deng, Jian-Hua; Cheng, Lin; Wang, Fan-Jie; Li, Guo-Zheng; Li, De-Jun; Cheng, Guo-An

    2014-12-10

    Achieving high current and longtime stable field emission from large area (larger than 1 mm(2)), densely arrayed emitters is of great importance in applications for vacuum electron sources. We report here the preparation of graphene nanosheet-carbon nanotube (GNS-CNT) hybrids by following a process of iron ion prebombardment on Si wafers, catalyst-free growth of GNSs on CNTs, and high-temperature annealing. Structural observations indicate that the iron ion prebombardment influences the growth of CNTs quite limitedly, and the self-assembled GNSs sparsely distributed on the tips of CNTs with their sharp edges unfolded outside. The field emission study indicates that the maximum emission current density (Jmax) is gradually promoted after these treatments, and the composition with GNSs is helpful for decreasing the operation fields of CNTs. An optimal Jmax up to 85.10 mA/cm(2) is achieved from a 4.65 mm(2) GNS-CNT sample, far larger than 7.41 mA/cm(2) for the as-grown CNTs. This great increase of Jmax is ascribed to the reinforced adhesion of GNS-CNT hybrids to substrates. We propose a rough calculation and find that this adhesion is promoted by 7.37 times after the three-step processing. We consider that both the ion prebombardment produced rough surface and the wrapping of CNT foot by catalyst residuals during thermal processing are responsible for this enhanced adhesion. Furthermore, the three-step prepared GNS-CNT hybrids present excellent field emission stability at high emission current densities (larger than 20 mA/cm(2)) after being perfectly aged.

  4. Improvement of III-nitride visible and ultraviolet light-emitting diode performance, including extraction efficiency, electrical efficiency, thermal management and efficiency maintenance at high current densities

    NASA Astrophysics Data System (ADS)

    Vampola, Kenneth

    In this work, highly efficient broad-area LEDs on bulk GaN substrates were developed and the fabrication process and device layout were optimized. This optimization relied in part on electrical, optical, thermal and recombination models. The peak external quantum efficiency of the 450 nm LEDs was over 68% when biased at 20 mA. The efficiency characteristic showed a typical droop curve, decreasing at high current densities. The cause of this droop is unknown. An exploratory experiment was conducted to characterize electron overflow and its role in efficiency droop. Novel device structures were developed, allowing direct measurement of overflow electrons in LED-like structures under electrical injection. In these test structures, electrons were observed in the p-type region of the LED only at current densities where efficiency droop was active. The onset of efficiency droop was preceded by the onset of electron overflow. However, the magnitude of the overflow current could not be measured and it is undetermined whether the dominant cause of efficiency droop is electron overflow or some other process such as Auger recombination. Calibration structures allowing measurement of the magnitude of the overflow are proposed. Work on deep-ultraviolet, 275 nm, LEDs is also presented. Demonstration of direct-wafer bonded LEDs to beta-Ga2O3 is presented. A SiC substrate removal process is discussed. LEDs fabricated by this flip-chip process exhibited up to 1.8 times greater power compared to LEDs fabricated by a standard process but suffered from increased forward voltage and premature failure. Further process development leading to electrically efficient operation is proposed.

  5. Density profile of nitrogen in cylindrical pores of MCM-41

    NASA Astrophysics Data System (ADS)

    Soper, Alan K.; Bowron, Daniel T.

    2017-09-01

    A straightforward approach using radiation scattering (X-ray or neutron) combined with atomistic modelling is used to accurately assess the pore dimensions in the porous silica, MCM-41. The method is used to calculate the density profile of nitrogen absorbed in this material at a variety of fractional pressures, p/p0, where p0 is the saturated vapour pressure, up to p/p0 = 0.36 at T = 87 K in the present instance. At this pressure two distinct layers of liquid nitrogen occur on the silica surface, with a relatively sharp gas-liquid interface. It is suggested surface tension effects at this interface strongly influence the growth of further layers.

  6. Sodium pentazolate: A nitrogen rich high energy density material

    NASA Astrophysics Data System (ADS)

    Steele, Brad A.; Oleynik, Ivan I.

    2016-01-01

    Sodium pentazolates NaN5 and Na2N5, new high energy density materials, are discovered during first principles crystal structure search for the compounds of varying amounts of elemental sodium and nitrogen. The pentazole anion (N5-) is stabilized in the condensed phase by sodium Na+ cations at pressures exceeding 20 GPa, and becomes metastable upon release of pressure. The sodium azide (NaN3) precursor is predicted to undergo a chemical transformation above 50 GPa into sodium pentazolates NaN5 and Na2N5. The calculated Raman spectrum of NaN5 is in agreement with the experimental Raman spectrum of a previously unidentified substance appearing upon compression and heating of NaN3.

  7. High Current Power Controller

    DTIC Science & Technology

    1981-04-01

    AFWAL-TR-81- 2016 U iui.N HIGH CURRENT Ŕ POWER CONTROLLER P. E. McCOLLUM Audwo ROCKWELL INTERNATIONAL AUTONETICS STRATEGIC SYSTEMS DIVISION 3370...personnel. During norm3l operation, HCP \\.s pose no hazard, bLt unde- certain operating conditions potential noaza-ds do exist. They are: (1) During

  8. SEMICONDUCTOR TECHNOLOGY: Influence of nitrogen dose on the charge density of nitrogen-implanted buried oxide in SOI wafers

    NASA Astrophysics Data System (ADS)

    Zhongshan, Zheng; Zhongli, Liu; Ning, Li; Guohua, Li; Enxia, Zhang

    2010-02-01

    To harden silicon-on-insulator (SOI) wafers fabricated using separation by implanted oxygen (SIMOX) to total-dose irradiation, the technique of nitrogen implantation into the buried oxide (BOX) layer of SIMOX wafers can be used. However, in this work, it has been found that all the nitrogen-implanted BOX layers reveal greater initial positive charge densities, which increased with increasing nitrogen implantation dose. Also, the results indicate that excessively large nitrogen implantation dose reduced the radiation tolerance of BOX for its high initial positive charge density. The bigger initial positive charge densities can be ascribed to the accumulation of implanted nitrogen near the Si-BOX interface after annealing. On the other hand, in our work, it has also been observed that, unlike nitrogen-implanted BOX, all the fluorine-implanted BOX layers show a negative charge density. To obtain the initial charge densities of the BOX layers, the tested samples were fabricated with a metal-BOX-silicon (MBS) structure based on SIMOX wafers for high-frequency capacitance-voltage (C-V) analysis.

  9. Optimization of a ribbon diode with magnetic insulation for increasing the current density in a high-current relativistic electron beam

    NASA Astrophysics Data System (ADS)

    Astrelin, V. T.; Arzhannikov, A. V.; Burdakov, A. V.; Sinitskii, S. L.; Stepanov, V. D.

    2009-05-01

    The geometry of the ribbon diode of the U-2 accelerator is optimized to increase both the current density and the total current of the relativistic electron beam for its subsequent injection into the plasma of a multimirror GOL-3 trap. Beam simulation in the diode was performed using the POISSON-2 applied software modified on the basis of the results obtained using the theory of a planar diode in an inclined magnetic field. As a result of the optimization, the diode geometry and the magnetic field configuration were found that should provide a factor of 1.5-2 increase in the current density in experiments with a small angular divergence of electron velocities.

  10. Achieving High Current Density of Perovskite Solar Cells by Modulating the Dominated Facets of Room-Temperature DC Magnetron Sputtered TiO2 Electron Extraction Layer.

    PubMed

    Huang, Aibin; Lei, Lei; Zhu, Jingting; Yu, Yu; Liu, Yan; Yang, Songwang; Bao, Shanhu; Cao, Xun; Jin, Ping

    2017-01-25

    The short circuit current density of perovskite solar cell (PSC) was boosted by modulating the dominated plane facets of TiO2 electron transport layer (ETL). Under optimized condition, TiO2 with dominant {001} facets showed (i) low incident light loss, (ii) highly smooth surface and excellent wettability for precursor solution, (iii) efficient electron extraction, and (iv) high conductivity in perovskite photovoltaic application. A current density of 24.19 mA cm(-2) was achieved as a value near the maximum limit. The power conversion efficiency was improved to 17.25%, which was the record value of PSCs with DC magnetron sputtered carrier transport layer. What is more, the room-temperature process had a great significance for the cost reduction and flexible application of PSCs.

  11. Average contact temperature and morphological details of the worn surface of copper based materials under high current density sliding against steel

    NASA Astrophysics Data System (ADS)

    Fadin, V. V.; Aleutdinova, M. I.; Kulikova, O. A.

    2016-11-01

    Dry sliding of copper and sintered composites of composition Cu-bearing steel against AISI steel 1045 under electric current of high contact density have been carried out. It is shown that the surface layer of copper and composites undergoes structural changes and tribolayer containing iron, copper and FeO oxide is formed. It is noted that the thin contact layer contains about 40 at % of oxygen and 40 at % Fe. Appearance of signs of a liquid phase is morphological feature of worn surface. It is established that contact temperature does not exceed 300°C. It allows claiming that melting of metals in tribolayer does not happen.

  12. Degradation Mechanisms of Magnesium Metal Anodes in Electrolytes Based on (CF3SO2)2N(-) at High Current Densities.

    PubMed

    Yoo, Hyun Deog; Han, Sang-Don; Bolotin, Igor L; Nolis, Gene M; Bayliss, Ryan D; Burrell, Anthony K; Vaughey, John T; Cabana, Jordi

    2017-09-19

    The energy density of rechargeable batteries utilizing metals as anodes surpasses that of Li ion batteries, which employ carbon instead. Among possible metals, magnesium represents a potential alternative to the conventional choice, lithium, in terms of storage density, safety, stability, and cost. However, a major obstacle for metal-based batteries is the identification of electrolytes that show reversible deposition/dissolution of the metal anode and support reversible intercalation of ions into a cathode. Traditional Grignard-based Mg electrolytes are excellent with respect to the reversible deposition of Mg, but their limited anodic stability and compatibility with oxide cathodes hinder their applicability in Mg batteries with higher voltage. Non-Grignard electrolytes, which consist of ethereal solutions of magnesium(II) bis(trifluoromethanesulfonyl)imide (Mg(TFSI)2), remain fairly stable near the potential of Mg deposition. The slight reactivity of these electrolytes toward Mg metal can be remedied by the addition of surface-protecting agents, such as MgCl2. Hence, ethereal solutions of Mg(TFSI)2 salt with MgCl2 as an additive have been suggested as a representative non-Grignard Mg electrolyte. In this work, the degradation mechanisms of a Mg metal anode in the TFSI-based electrolyte were studied using a current density of 1 mA cm(-2) and an areal capacity of ∼0.4 mAh cm(-2), which is close to those used in practical applications. The degradation mechanisms identified include the corrosion of Mg metal, which causes the loss of electronic pathways and mechanical integrity, the nonuniform deposition of Mg, and the decomposition of TFSI(-) anions. This study not only represents an assessment of the behavior of Mg metal anodes at practical current density and areal capacity but also details the outcomes of interfacial passivation, which was detected by simple cyclic voltammetry experiments. This study also points out the absolute absence of any passivation at

  13. Comparison of TALIF and catalytic probes for the determination of nitrogen atom density in a nitrogen plasma afterglow

    NASA Astrophysics Data System (ADS)

    Gaboriau, F.; Cvelbar, U.; Mozetic, M.; Erradi, A.; Rouffet, B.

    2009-03-01

    The density of neutral nitrogen atoms in a glass reactor was measured by two absolute methods: two-photon absorption laser induced fluorescence (TALIF) and catalytic probes. The source of N atoms was nitrogen plasma created in a quartz tube by surfatron microwave generator operating at 2.45 GHz and adjustable output power up to 300 W. The TALIF measurements were performed using a dye laser which was pumped by a YAG laser. At the exit of the dye laser, the beam frequency was doubled through a KDP crystal and then mixed in a BBO crystal. The wavelength of the output laser beam was chosen at 206.65 nm so two-photon absorption was suitable to excite nitrogen atoms from the ground state to the 5d 2D state. Absolute N density was determined by using calibration with krypton. Simultaneously, the N atom density was measured with a fiber optics catalytic probe (FOCP) with a well-activated iron catalytic tip. Measurements were performed by both methods at nitrogen flows between 0.2 and 2 l min-1, and discharge powers between 60 and 300 W. At rather high nitrogen flows, the N atom density increased monotonically with increasing discharge power, while at lower flow saturation was observed. TALIF showed somewhat higher values than FOCP which was attributed to the accuracy of both methods. The main advantage of TALIF is a broader detection range, while FOCP is an extremely simple and inexpensive technique.

  14. Nitrogen isotopic composition and density of the Archean atmosphere.

    PubMed

    Marty, Bernard; Zimmermann, Laurent; Pujol, Magali; Burgess, Ray; Philippot, Pascal

    2013-10-04

    Understanding the atmosphere's composition during the Archean eon is fundamental to unraveling ancient environmental conditions. We show from the analysis of nitrogen and argon isotopes in fluid inclusions trapped in 3.0- to 3.5-billion-year-old hydrothermal quartz that the partial pressure of N2 of the Archean atmosphere was lower than 1.1 bar, possibly as low as 0.5 bar, and had a nitrogen isotopic composition comparable to the present-day one. These results imply that dinitrogen did not play a significant role in the thermal budget of the ancient Earth and that the Archean partial pressure of CO2 was probably lower than 0.7 bar.

  15. Method for real-time measurement of nitrogen atom density in atmospheric pressure post-discharge flows

    NASA Astrophysics Data System (ADS)

    Oinuma, Gaku; Inanaga, Yasutaka; Noda, Seiji; Tanimura, Yasuhiro; Kuzumoto, Masaki; Tabata, Yoichiro; Watanabe, Kensuke

    2008-08-01

    A method has been developed for real-time measurement of nitrogen atom density in atmospheric pressure post-discharge flows. In this method, nitric oxide is supplied to the downstream of a nitrogen discharge as a reactant. Our chemical simulation has revealed that the injected nitric oxide is consumed mainly by reductive reaction with nitrogen atoms or oxidative reaction with oxygen atoms. The number density of atomic nitrogen is determined almost instantaneously through the measurement of nitric oxide and nitrogen dioxide densities with a gas analyser. The experimental verification was carried out with a dielectric barrier discharge unit as a nitrogen atom source, and the results showed good agreement with simulation predictions.

  16. Optimization of Nitrogen Rate and Planting Density for Improving Yield, Nitrogen Use Efficiency, and Lodging Resistance in Oilseed Rape

    PubMed Central

    Khan, Shahbaz; Anwar, Sumera; Kuai, Jie; Ullah, Sana; Fahad, Shah; Zhou, Guangsheng

    2017-01-01

    Yield and lodging related traits are essential for improving rapeseed production. The objective of the present study was to investigate the influence of plant density (D) and nitrogen (N) rates on morphological and physiological traits related to yield and lodging in rapeseed. We evaluated Huayouza 9 for two consecutive growing seasons (2014–2016) under three plant densities (LD, 10 plants m−2; MD, 30 plants m−2; HD, 60 plants m−2) and four N rates (0, 60, 120, and 180 kg ha−1). Experiment was laid out in split plot design using density as a main factor and N as sub-plot factor with three replications each. Seed yield was increased by increasing density and N rate, reaching a peak at HD with 180 kg N ha−1. The effect of N rate was consistently positive in increasing the plant height, pod area index, 1,000 seed weight, shoot and root dry weights, and root neck diameter, reaching a peak at 180 kg N ha−1. Plant height was decreased by increasing D, whereas the maximum radiation interception (~80%) and net photosynthetic rate were recorded at MD at highest N. Lodging resistance and nitrogen use efficiency significantly increased with increasing D from 10 to 30 plants m−2, and N rate up to 120 kg ha−1, further increase of D and N decreased lodging resistance and NUE. Hence, our study implies that planting density 30 plants m−2 can improve yield, nitrogen use efficiency, and enhance lodging resistance by improving crop canopy. PMID:28536581

  17. Creation of high density ensembles of nitrogen-vacancy centers in nitrogen-rich type Ib nanodiamonds.

    PubMed

    Su, Long-Jyun; Fang, Chia-Yi; Chang, Yu-Tang; Chen, Kuan-Ming; Yu, Yueh-Chung; Hsu, Jui-Hung; Chang, Huan-Cheng

    2013-08-09

    This work explores the possibility of increasing the density of negatively charged nitrogen-vacancy centers ([NV(-)]) in nanodiamonds using nitrogen-rich type Ib diamond powders as the starting material. The nanodiamonds (10-100 nm in diameter) were prepared by ball milling of microdiamonds, in which the density of neutral and atomically dispersed nitrogen atoms ([N(0)]) was measured by diffuse reflectance infrared Fourier transform spectroscopy. A systematic measurement of the fluorescence intensities and lifetimes of the crushed monocrystalline diamonds as a function of [N(0)] indicated that [NV(-)] increases nearly linearly with [N(0)] at 100-200 ppm. The trend, however, failed to continue for nanodiamonds with higher [N(0)] (up to 390 ppm) but poorer crystallinity. We attribute the result to a combined effect of fluorescence quenching as well as the lower conversion efficiency of vacancies to NV(-) due to the presence of more impurities and defects in these as-grown diamond crystallites. The principles and practice of fabricating brighter and smaller fluorescent nanodiamonds are discussed.

  18. Characterization of the nitrogen split interstitial defect in wurtzite aluminum nitride using density functional theory

    SciTech Connect

    Szállás, A.; Szász, K.; Gali, A.

    2014-09-21

    We carried out Heyd-Scuseria-Ernzerhof hybrid density functional theory plane wave supercell calculations in wurtzite aluminum nitride in order to characterize the geometry, formation energies, transition levels, and hyperfine tensors of the nitrogen split interstitial defect. The calculated hyperfine tensors may provide useful fingerprint of this defect for electron paramagnetic resonance measurement.

  19. Does nitrogen gas bubbled through a low density polymer gel dosimeter solution affect the polymerization process?

    PubMed Central

    Shahbazi-Gahrouei, Daryoush; Gholami, Mehrdad; Pourfallah, Tayyeb Allahverdi; Keshtkar, Mohammad

    2015-01-01

    Background: On account of the lower electron density in the lung tissue, the dose distribution in the lung cannot be verified with the existing polymer gel dosimeters. Thus, the aims of this study are to make a low density polymer gel dosimeter and investigate the effect of nitrogen gas bubbles on the R2 responses and its homogeneity. Materials and Methods: Two different types of low density polymer gel dosimeters were prepared according to a composition proposed by De Deene, with some modifications. In the first type, no nitrogen gas was perfused through the gel solution and water. In the second type, to expel the dissolved oxygen, nitrogen gas was perfused through the water and gel solution. The post-irradiation times in the gels were 24 and 5 hours, respectively, with and without perfusion of nitrogen gas through the water and gel solution. Results: In the first type of gel, there was a linear correlation between the doses and R2 responses from 0 to 12 Gy. The fabricated gel had a higher dynamic range than the other low density polymer gel dosimeter; but its background R2 response was higher. In the second type, no difference in R2 response was seen in the dose ranges from 0 to 18 Gy. Both gels had a mass density between 0.35 and 0.45 g.cm-3 and CT values of about -650 to -750 Hounsfield units. Conclusion: It appeared that reactions between gelatin-free radicals and monomers, due to an increase in the gel temperature during rotation in the household mixer, led to a higher R2-background response. In the second type of gel, it seemed that the collapse of the nitrogen bubbles was the main factor that affected the R2-responses. PMID:26015914

  20. High current-density anodic electro-dissolution in flow-injection systems for the determination of aluminium, copper and zinc in non-ferroalloys by flame atomic absorption spectrometry.

    PubMed

    Giacomozzi, C A; de Queiróz, R R; Souza, I G; Neto, J A

    1999-01-01

    An automatic procedure with a high current-density anodic electrodissolution unit (HDAE) is proposed for the determination of aluminium, copper and zinc in non-ferroalloys by flame atomic absorption spectrometry, based on the direct solid analysis. It consists of solenoid valve-based commutation in a flow-injection system for on-line sample electro-dissolution and calibration with one multi-element standard, an electrolytic cell equipped with two electrodes (a silver needle acts as cathode, and sample as anode), and an intelligent unit. The latter is assembled in a PC-compatible microcomputer for instrument control, and for data acquisition and processing. General management of the process is achieved by use of software written in Pascal. Electrolyte compositions, flow rates, commutation times, applied current and electrolysis time were investigated. A 0.5 mol l(-1) HN03 solution was elected as electrolyte and 300 A/cm(2) as the continuous current pulse.The performance of the proposed system was evaluated by analysing aluminium in Al-alloy samples, and copper/zinc in brass and bronze samples, respectively. The system handles about 50 samples per hour. Results are precise (R.S.D. < 2%) and in agreement with those obtained by ICP-AES and spectrophotometry at a 95% confidence level.

  1. Measurements of rotational and vibrational temperatures in a high density nitrogen negative corona discharge

    SciTech Connect

    Nur, M.; Hernandez-Avila, J.L.; Bonifaci, N.; Denat, A.

    1995-12-31

    Previous studies of the electrical conduction of nitrogen, using point-plane electrodes, have shown that corona discharges occur in all the range of density from low pressure gas to the liquid. Moreover, electrical and transport parameters are mainly a function of fluid density. At each density, above a threshold voltage V{sub o}, the electric current I is correlated to an emitted light current I{sub L} and I{sub L} is proportional to I. The spectral analysis of this emitted light can be used to evaluate the temperatures (electronic T{sub e}, rotational T{sub r} and vibrational T{sub v}) in the corona discharge. However, in corona discharge where temperatures are different from each other, these evaluated temperatures are only {open_quotes}effective{close_quotes} ones (i.e. not thermodynamic temperatures in the sense of equilibrium). The aim of our work is to investigate the processes of corona discharges in superdense fluids and, in particular, to determine corona temperatures as a function of nitrogen density (from 1.4 x 10{sup 20} up to 2 x 10{sup 21} cm{sup -3}). These temperatures are deduced from a comparison between computer generated synthetic spectra and experimental low-resolution spectra of the second positif system and the first negative system of nitrogen.

  2. Diurnal and semidiurnal nitrogen density and temperature variations from thermosphere probe measurements.

    NASA Technical Reports Server (NTRS)

    Newton, G. P.; Mayr, H. G.

    1973-01-01

    Amplitudes and phases for the diurnal and semidiurnal variations of thermospheric molecular nitrogen density and temperature are determined from data obtained by six rocket-launched thermosphere probes. The semidiurnal tide is significant for the lower thermosphere variations, where it could dominate in the N2 density at 140 km and in the temperature for altitudes between 170 and 200 km. At exospheric heights, the magnitudes of the semidiurnal modes in density and temperature are significantly smaller than those of the diurnal mode. The temperature phase is height-dependent in both diurnal and semidiurnal components below 200 km, thus contributing to phase differences between N2 density and temperature in both modes. No significant phase differences are apparent between N2 density and thermospheric temperature above 250 km.

  3. AuNx stabilization with interstitial nitrogen atoms: A Density Functional Theory Study

    NASA Astrophysics Data System (ADS)

    Quintero, J. H.; Gonzalez-Hernandez, R.; Ospina, R.; Mariño, A.

    2017-06-01

    Researchers have been studying 4d and 5d Series Transition Metal Nitrides lately as a result of the experimental production of AuN, PtN, CuN. In this paper, we used the Density Functional Theory (DFT) implementing a pseudopotential plane-wave method to study the incorporation of nitrogen atoms in the face-centered cube (fcc) lattice of gold (Au). First, we took the fcc structure of gold, and gradually located the nitrogen atoms in tetrahedral (TH) and octahedral (OH) interstitial sites. AuN stabilized in: 2OH (30%), 4OH and 4TH (50%), 4OH - 2TH (close to the wurtzite structure) and 6TH (60%). This leads us to think that AuN behaves like a Transition Metal Nitride since the nitrogen atoms look for tetrahedral sites.

  4. Comparison of Ti/Pd/Ag, Pd/Ti/Pd/Ag and Pd/Ge/Ti/Pd/Ag contacts to n-type GaAs for electronic devices handling high current densities

    NASA Astrophysics Data System (ADS)

    Huo, Pengyun; Galiana, Beatriz; Rey-Stolle, Ignacio

    2017-04-01

    In the quest for metal contacts for electronic devices handling high current densities, we report the results of Pd/Ti/Pd/Ag and Pd/Ge/Ti/Pd/Ag contacts to n-GaAs and compare them to Ti/Pd/Ag and AuGe/Ni/Au. These metal systems have been designed with the goal of producing an electrical contact with (a) low metal-semiconductor specific contact resistance, (b) very high sheet conductance, (c) good bondability, (d) long-term durability and (e) cost-effectiveness. The structure of the contacts consists of an interfacial layer (either Pd or Pd/Ge) intended to produce a low metal-semiconductor specific contact resistance; a diffusion barrier (Ti/Pd) and a thick top layer of Ag to provide the desired high sheet conductance, limited cost and good bondability. The results show that both systems can achieve very low metal resistivity (ρ M ˜ 2 × 10-6 Ω cm), reaching values close to that of pure bulk silver. This fact is attributed to the Ti/Pd bilayer acting as an efficient diffusion barrier, and thus the metal sheet resistance can be controlled by the thickness of the deposited silver layer. Moreover, the use of Pd as interfacial layer produces contacts with moderate specific contact resistance (ρ C ˜ 10-4 Ω cm2) whilst the use of Pd/Ge decreases the specific contact resistance to ρ C ˜ 1.5 × 10-7 Ω cm2, as a result of the formation of a Pd4(GaAs, Ge2) compound at the GaAs interface.

  5. Rotational Relaxation Analysis of Nitrogen in Low-Density Freejet Expansions

    NASA Technical Reports Server (NTRS)

    Gochberg, Lawrence A.; Haas, Brian L.

    1994-01-01

    The phenomena of rotational relaxation of nitrogen has been examined by numerous investigators over many years. One of the experiments which has been performed examines nonequilibrium flow in low-density free jet expansions. Data have been taken in such flows using a variety of techniques, including time-of-flight methods and electron beam fluorescence spectroscopy. The direct flow properties measured in these different investigations, such as density and translational, rotational and vibrational temperatures generally show reasonable agreement. However, this kind of correlation from experiment to experiment tends to be lost when these data are analyzed to obtain rotational relaxation time or collision number. The goal of such data analyses is to generate a succinct model for rotational relaxation in nitrogen which is essential for the computation of nonequilibrium rarefied flows. The objective of the present work is to process a large body of experimental data in a consistent manner to yield relaxation model parameters of the greatest utility for flow computations.

  6. Oso 7 measurements of atomic oxygen and molecular nitrogen densities in the earth's upper atmosphere

    NASA Technical Reports Server (NTRS)

    Modali, S. B.; Thomas, R. W. L.; Chapman, R. D.; Thomas, R. J.

    1976-01-01

    Densities of molecular nitrogen and monatomic oxygen are presented as a function of altitude for selected intervals of March-May 1972 Oso 7 satellite data. Results on atmospheric attenuation of solar extreme UV radiation at 200-400 A, at heights from 250 to 500 km, are of particular interest. Satellite sunrise measurements above 330 km are not consistent with the Jacchia (1971) atmospheric model, and may constitute evidence for dynamic phenomena occurring in the heated upper levels. Density and temperature variations are considered mainly responsible for the sunrise anomaly observed. Checks were made for possible errors in the satellite pointing system and other instrumental effects.

  7. Molecular dissociation and shock-induced cooling in fluid nitrogen at high densities and temperatures

    NASA Technical Reports Server (NTRS)

    Radousky, H. B.; Nellis, W. J.; Ross, M.; Hamilton, D. C.; Mitchell, A. C.

    1986-01-01

    Radiative temperatures and electrical conductivities were measured for fluid nitrogen compressed dynamically to pressures of 18-90 GPa, temperatures of 4000-14,000 K, and densities of 2-3 g/cu cm. The data show a continuous phase transition above 30 GPa shock pressure and confirm that (delta-P/delta-T)v is less than 0, as indicated previously by Hugoniot equation-of-state experiments. The first observation of shock-induced cooling is also reported. The data are interpreted in terms of molecular dissociation, and the concentration of dissociated molecules is calculated as a function of density and temperature.

  8. High-Energy Density and Superhard Nitrogen-Rich B-N Compounds

    NASA Astrophysics Data System (ADS)

    Li, Yinwei; Hao, Jian; Liu, Hanyu; Lu, Siyu; Tse, John S.

    2015-09-01

    The pressure-induced transformation of diatomic nitrogen into nonmolecular polymeric phases may produce potentially useful high-energy-density materials. We combine first-principles calculations with structure searching to predict a new class of nitrogen-rich boron nitrides with a stoichiometry of B3N5 that are stable or metastable relative to solid N2 and h -BN at ambient pressure. The most stable phase at ambient pressure has a layered structure (h -B3N5 ) containing hexagonal B3N3 layers sandwiched with intercalated freely rotating N2 molecules. At 15 GPa, a three-dimensional C 2 2 21 structure with single N-N bonds becomes the most stable. This pressure is much lower than that required for triple-to-single bond transformation in pure solid nitrogen (110 GPa). More importantly, C 2 2 21-B3N5 is metastable, and can be recovered under ambient conditions. Its energy density of ˜3.44 kJ /g makes it a potential high-energy-density material. In addition, stress-strain calculations estimate a Vicker's hardness of ˜4 4 GPa . Structure searching reveals a new clathrate sodalitelike BN structure that is metastable under ambient conditions.

  9. Predicting liquid densities of organic compounds: II, Nitrogen and sulfur compounds

    SciTech Connect

    Wood, G.O.; Weaver, T.B.

    1993-02-01

    Correlations of liquid densities have been extended to more classes of organic compounds. The products of liquid density and molecular weight at or near 20{degrees}C were previously found to be linear functions of the number and types of carbon atoms in the molecule. Cyclic carbon atoms contributed more to density than carbon atoms not part of a ring structure. Carbon atoms which occupy two rings have since been found to contribute even different increments. Additional databases of liquid densities have been set up for compounds with cyclic oxygen atoms, cyclic and noncyclic nitrogen atoms, and cyclic and noncyclic sulfur atoms. Correlation parameters have been obtained by fitting these data by least squares minimization.

  10. Adsorption of nitrogen oxides on graphene and graphene oxides: insights from density functional calculations.

    PubMed

    Tang, Shaobin; Cao, Zexing

    2011-01-28

    The interactions of nitrogen oxides NO(x) (x = 1,2,3) and N(2)O(4) with graphene and graphene oxides (GOs) were studied by the density functional theory. Optimized geometries, binding energies, and electronic structures of the gas molecule-adsorbed graphene and GO were determined on the basis of first-principles calculations. The adsorption of nitrogen oxides on GO is generally stronger than that on graphene due to the presence of the active defect sites, such as the hydroxyl and carbonyl functional groups and the carbon atom near these groups. These active defect sites increase the binding energies and enhance charge transfers from nitrogen oxides to GO, eventually leading to the chemisorption of gas molecules and the doping character transition from acceptor to donor for NO(2) and NO. The interaction of nitrogen oxides with GO with various functional groups can result in the formation of hydrogen bonds OH⋅⋅⋅O (N) between -OH and nitrogen oxides and new weak covalent bonds C⋅⋅⋅N and C⋅⋅⋅O, as well as the H abstraction to form nitrous acid- and nitric acidlike moieties. The spin-polarized density of states reveals a strong hybridization of frontier orbitals of NO(2) and NO(3) with the electronic states around the Fermi level of GO, and gives rise to the strong acceptor doping by these molecules and remarkable charge transfers from molecules to GO, compared to NO and N(2)O(4) adsorptions on GO. The calculated results show good agreement with experimental observations.

  11. High PRF high current switch

    DOEpatents

    Moran, Stuart L.; Hutcherson, R. Kenneth

    1990-03-27

    A triggerable, high voltage, high current, spark gap switch for use in pu power systems. The device comprises a pair of electrodes in a high pressure hydrogen environment that is triggered by introducing an arc between one electrode and a trigger pin. Unusually high repetition rates may be obtained by undervolting the switch, i.e., operating the trigger at voltages much below the self-breakdown voltage of the device.

  12. High current pulse transmission cable

    SciTech Connect

    Parsons, W.M.

    1990-09-28

    This invention is comprised of a transmission cable for carrying high current pulses in which an even numbered plurality of electrical conductors surrounds a central ground conductor. Each electrical conductor is connected so that it at any instant in time it will carry current of opposite polarity to the polarity carried by adjacent conductors. This arrangement cancels practically all of the external fields generated by current in the conductors.

  13. Experimental analysis of a nitrogen removal process simulation of wastewater land treatment under three different wheat planting densities.

    PubMed

    Wang, Hong-Qi; Chen, Jia-Jun; Tian, Kai-Ming; Lu, Yan

    2002-07-01

    Nitrogen contaminant transport, transformation and uptake simulation experiments were conducted in green house under three different planting density of winter wheat. They were Group A, planting density of 0.0208 plants/cm2, Group B, 0.1042 plants/cm2, and Group C, 0.1415 plants/cm2. The capacity and ratio of nitrogen removal were different on three kinds of conditions of wastewater land treatment. From analysis of wastewater treatment capacity, wastewater concentration and irrigation intensity for Group C were suitable and nitrogen quantity added was 2 times of that for Group B, 2.6 times for Group A while nitrogen residue was only 7.06%. Hence, wastewater irrigation and treatment design with purpose of waste water treatment should select the design with maximum capacity, optimal removal ratio and least residue in soil, which was closely related to crop planting density, crop growth status and also background nitrogen quantity in soil.

  14. Metastable Polymeric Nitrogen: The Ultimate Green High-Energy-Density Material

    NASA Astrophysics Data System (ADS)

    Ciezak, Jennifer

    2007-06-01

    High-energy-high-density materials offering increased stability, vulnerability, and environmental safety are being aggressively pursued to meet the requirements of the DoD Joint Visions and Future Force. Nearly two decades ago, it was proposed that polymeric nitrogen would exceed all of these requirements and possess nearly five times the energy of any conventional energetic material in use today. The present study details an investigation into nitrogen polymerization using a novel high-pressure approach utilizing sodium azide as the starting material. Due to the weaker bonding structure of the anionic azide chains in comparison to a N-N triple bond, one expects that the azide chains will create single-covalently bonded polymeric networks more easily than diatomic nitrogen. A polymeric form of sodium azide was synthesized at high pressures, but the material was not metastable at ambient conditions, which precluded performance testing. Quantum chemical calculations have indicated stabilization of the polymeric structure at ambient conditions may be possible with the addition of hydrogen. Vibrational spectroscopic characterization suggests that a meta-stable polymeric form of nitrogen has been synthesized under high-pressure using sodium azide/hydrogen as the starting materials. This material remains stable at ambient conditions upwards of two weeks depending on the storage conditions.

  15. 2D quasi-ordered nitrogen-enriched porous carbon nanohybrids for high energy density supercapacitors.

    PubMed

    Kan, Kan; Wang, Lei; Yu, Peng; Jiang, Baojiang; Shi, Keying; Fu, Honggang

    2016-05-21

    Two-dimensional (2D) quasi-ordered nitrogen-enriched porous carbon (QNPC) nanohybrids, with the characteristics of an ultrathin graphite nanosheet framework and thick quasi-ordered nitrogen-doped carbon cladding with a porous texture, have been synthesized via an in situ polymerization assembly method. In the synthesis, the expandable graphite (EG) is enlarged by an intermittent microwave method, and then aniline monomers are intercalated into the interlayers of the expanded EG with the assistance of a vacuum. Subsequently, the intercalated aniline monomers could assemble on the interlayer surface of the expanded EG, accompanied by the in situ polymerization from aniline monomers to polyaniline. Meanwhile, the expanded EG could be exfoliated to graphite nanosheets. By subsequent pyrolysis and activation processes, the QNPC nanohybrids could be prepared. As supercapacitor electrodes, a typical QNPC12-700 sample derived from the precursor containing an EG content of 12%, with a high level of nitrogen doping of 5.22 at%, offers a high specific capacitance of 305.7 F g(-1) (1 A g(-1)), excellent rate-capability and long-term stability. Notably, an extremely high energy density of 95.7 Wh kg(-1) at a power density of 449.7 W kg(-1) in an ionic liquid electrolyte can be achieved. The unique structural features and moderate heteroatom doping of the QNPC nanohybrids combines electrochemical double layer and faradaic capacitance contributions, which make these nanohybrids ideal candidates as electrode materials for high-performance energy storage devices.

  16. Electron beam flourescence measurements in low density free jets of heated nitrogen

    NASA Technical Reports Server (NTRS)

    Gochberg, L. A.; Hurlbut, F. C.

    1993-01-01

    Rotational temperatures have been measured in heated free jet expansions of low density nitrogen using the electron beam flourescence technique. Spectroscopic measurements of the (0,0) band of the first negative system of nitrogen revealed the rotational nonequilibrium behavior in the flow field upstream of and through the Mach disk, as well as the flow field farther downstream. These results are compared to free jet expansion data and computations regarding Mach disk location and terminal rotational temperature. Comparisons indicate a rotational relaxation-collision number of about 3. Both measurements and calculations show that these flow fields are generated from stagnation conditions of 240 to 475 Torr-mm and 700 to 1325 K. Results are also presented for shock thickness based on rotational temperature.

  17. Nitrogen uptake in riparian plant communities across a sharp ecological boundary of salmon density

    PubMed Central

    Mathewson, DD; Hocking, MD; Reimchen, TE

    2003-01-01

    Background Recent studies of anadromous salmon (Oncorhynchus spp.) on the Pacific Coast of North America indicate an important and previously unrecognized role of salmonid nutrients to terrestrial biota. However, the extent of this uptake by primary producers and consumers and the influences on community structure remain poorly described. We examine here the contribution of salmon nutrients to multiple taxa of riparian vegetation (Blechnum spicant, Menziesii ferruginea, Oplopanax horridus, Rubus spectabilis, Vaccinium alaskaense, V. parvifolium, Tsuga heterophylla) and measure foliar δ15N, total %N and plant community structure at two geographically separated watersheds in coastal British Columbia. To reduce potentially confounding effects of precipitation, substrate and other abiotic variables, we made comparisons across a sharp ecological boundary of salmon density that resulted from a waterfall barrier to salmon migration. Results δ15N and %N in foliage, and %cover of soil nitrogen indicators differed across the waterfall barrier to salmon at each watershed. δ15N values were enriched by 1.4‰ to 9.0‰ below the falls depending on species and watershed, providing a relative contribution of marine-derived nitrogen (MDN) to vegetation of 10% to 60%. %N in foliar tissues was slightly higher below the falls, with the majority of variance occurring between vegetation species. Community structure also differed with higher incidence of nitrogen-rich soil indicator species below the waterfalls. Conclusions Measures of δ15N, %N and vegetation cover indicate a consistent difference in the riparian community across a sharp ecological boundary of salmon density. The additional N source that salmon provide to nitrogen-limited habitats appears to have significant impacts on the N budget of riparian vegetation, which may increase primary productivity, and result in community shifts between sites with and without salmon access. This, in turn, may have cascading ecosystem

  18. Nitrogen uptake in riparian plant communities across a sharp ecological boundary of salmon density.

    PubMed

    Mathewson, D D; Hocking, M D; Reimchen, T E

    2003-05-03

    Recent studies of anadromous salmon (Oncorhynchus spp.) on the Pacific Coast of North America indicate an important and previously unrecognized role of salmonid nutrients to terrestrial biota. However, the extent of this uptake by primary producers and consumers and the influences on community structure remain poorly described. We examine here the contribution of salmon nutrients to multiple taxa of riparian vegetation (Blechnum spicant, Menziesii ferruginea, Oplopanax horridus, Rubus spectabilis, Vaccinium alaskaense, V. parvifolium, Tsuga heterophylla) and measure foliar delta15N, total %N and plant community structure at two geographically separated watersheds in coastal British Columbia. To reduce potentially confounding effects of precipitation, substrate and other abiotic variables, we made comparisons across a sharp ecological boundary of salmon density that resulted from a waterfall barrier to salmon migration. delta15N and %N in foliage, and %cover of soil nitrogen indicators differed across the waterfall barrier to salmon at each watershed. delta15N values were enriched by 1.4 per thousand to 9.0 per thousand below the falls depending on species and watershed, providing a relative contribution of marine-derived nitrogen (MDN) to vegetation of 10% to 60%. %N in foliar tissues was slightly higher below the falls, with the majority of variance occurring between vegetation species. Community structure also differed with higher incidence of nitrogen-rich soil indicator species below the waterfalls. Measures of delta15N, %N and vegetation cover indicate a consistent difference in the riparian community across a sharp ecological boundary of salmon density. The additional N source that salmon provide to nitrogen-limited habitats appears to have significant impacts on the N budget of riparian vegetation, which may increase primary productivity, and result in community shifts between sites with and without salmon access. This, in turn, may have cascading ecosystem

  19. Nitrogen

    USGS Publications Warehouse

    Apodaca, Lori E.

    2013-01-01

    The article presents an overview of the nitrogen chemical market as of July 2013, including the production of ammonia compounds. Industrial uses for ammonia include fertilizers, explosives, and plastics. Other topics include industrial capacity of U.S. ammonia producers CF Industries Holdings Inc., Koch Nitrogen Co., PCS Nitrogen, Inc., and Agrium Inc., the impact of natural gas prices on the nitrogen industry, and demand for corn crops for ethanol production.

  20. Simple, high current, antimony ion source.

    PubMed

    Sugiura, H

    1979-01-01

    A simple metal ion source capable of producing a continuous, uncontaminated, high current beam of Sb ions is presented. It produced a total ion current of 200 muA at 1 kV extraction voltage. A discharge occurred in the source at a pressure of 6x10(-4) Torr. The ion current extracted from the source increased with the 3/2 power of the extraction voltage. The perveance of the source and ion density in the plasma were 8x10(-9) and 1.8x10(11) cm(-3), respectively.

  1. Field-scale roles of density, temperature, nitrogen, and predation on aphid population dynamics.

    PubMed

    de Valpine, Perry; Rosenheim, Jay A

    2008-02-01

    Robust analyses of noisy, stage-structured, irregularly spaced, field-scale data incorporating multiple sources of variability and nonlinear dynamics remain very limited, hindering understanding of how small-scale studies relate to large-scale population dynamics. We used a novel, complementary Bayesian and frequentist state-space model analysis to ask how density, temperature, plant nitrogen, and predators affect cotton aphid (Aphis gossypii) population dynamics in weekly data from 18 field-years and whether estimated effects are consistent with small-scale studies. We found clear roles of density and temperature but not of plant nitrogen or predators, for which Bayesian and frequentist evidence differed. However, overall predictability of field-scale dynamics remained low. This study demonstrates stage-structured state-space model analysis incorporating bottom-up, top-down, and density-dependent effects for within-season (nearly continuous time), nonlinear population dynamics. The analysis combines Bayesian posterior evidence with maximum-likelihood estimation and frequentist hypothesis testing using average one-step-ahead residuals.

  2. Boosting Power Density of Microbial Fuel Cells with 3D Nitrogen-Doped Graphene Aerogel Electrode.

    PubMed

    Yang, Yang; Liu, Tianyu; Zhu, Xun; Zhang, Feng; Ye, Dingding; Liao, Qiang; Li, Yat

    2016-08-01

    A 3D nitrogen-doped graphene aerogel (N-GA) as an anode material for microbial fuel cells (MFCs) is reported. Electron microscopy images reveal that the N-GA possesses hierarchical porous structure that allows efficient diffusion of both bacterial cells and electron mediators in the interior space of 3D electrode, and thus, the colonization of bacterial communities. Electrochemical impedance spectroscopic measurements further show that nitrogen doping considerably reduces the charge transfer resistance and internal resistance of GA, which helps to enhance the MFC power density. Importantly, the dual-chamber milliliter-scale MFC with N-GA anode yields an outstanding volumetric power density of 225 ± 12 W m(-3) normalized to the total volume of the anodic chamber (750 ± 40 W m(-3) normalized to the volume of the anode). These power densities are the highest values report for milliliter-scale MFCs with similar chamber size (25 mL) under the similar measurement conditions. The 3D N-GA electrode shows great promise for improving the power generation of MFC devices.

  3. Electron number density measurements using laser-induced breakdown spectroscopy of ionized nitrogen spectral lines

    NASA Astrophysics Data System (ADS)

    EL Sherbini, Ashraf M.; Aboulfotouh, Abdelnasser M.; Parigger, Christian G.

    2016-11-01

    Spectrally broadened, singly ionized nitrogen emission lines are monitored to determine electron number densities in laser-induced plasma from aluminum, nano- and bulk-zinc monoxide, as well as hydrogen-rich plastic and wood targets. The optical emission spectra for N II at the average wavelength of 500.33 nm are recorded in standard ambient temperature and pressure environments. For time delays of 25 to 450 ns from the onset of the 1064-nm Nd:YAG radiation induced optical breakdown, the electron number densities in the range of 5.1 ±1 ×1019 to 0.22 ±0.04 ×1019 cm-3 are inferred from the continuum and the nitrogen spectral line analysis. In addition, the corresponding electron temperatures of 10.1 ±0.6 eV to 1 ±0.2 eV are determined from the calculated absolute spectral radiance values in the near infrared region. At the early stages of plasma emission, Balmer series hydrogen lines are embedded in free electron radiation yet the broadening of the N II lines yields reliable electron number density values.

  4. HIGH CURRENT COAXIAL PHOTOMULTIPLIER TUBE

    DOEpatents

    Glass, N.W.

    1960-01-19

    A medium-gain photomultiplier tube having high current output, fast rise- time, and matched output impedance was developed. The photomultiplier tube comprises an elongated cylindrical envelope, a cylindrical anode supported at the axis of the envelope, a plurality of elongated spaced opaque areas on the envelope, and a plurality of light admitting windows. A photo-cathode is supported adjacent to each of the windows, and a plurality of secondary emissive dynodes are arranged in two types of radial arrays which are alternately positioned to fill the annular space between the anode and the envelope. The dynodes are in an array being radially staggered with respect to the dynodes in the adjacent array, the dynodes each having a portion arranged at an angle with respect to the electron path, such that electrons emitted by each cathode undergo multiplication upon impingement on a dynode and redirected flight to the next adjacent dynode.

  5. High current capacity electrical connector

    DOEpatents

    Bettis, Edward S.; Watts, Harry L.

    1976-01-13

    An electrical connector is provided for coupling high current capacity electrical conductors such as copper busses or the like. The connector is arranged in a "sandwiched" configuration in which a conductor plate contacts the busses along major surfaces thereof clamped between two stainless steel backing plates. The conductor plate is provided with a plurality of contact buttons affixed therein in a spaced array such that the caps of the buttons extend above the conductor plate surface to contact the busses. When clamping bolts provided through openings in the sandwiched arrangement are tightened, Belleville springs provided under the rim of each button cap are compressed and resiliently force the caps into contact with the busses' contacting surfaces to maintain a predetermined electrical contact area provided by the button cap tops. The contact area does not change with changing thermal or mechanical stresses applied to the coupled conductors.

  6. Adsorption of atomic nitrogen and oxygen on [Formula: see text] surface: a density functional theory study.

    PubMed

    Breedon, M; Spencer, M J S; Yarovsky, I

    2009-04-08

    The adsorption of atomic nitrogen and oxygen on the ([Formula: see text]) crystal face of zinc oxide (ZnO) was studied. Binding energies, workfunction changes, vibrational frequencies, charge density differences and electron localization functions were calculated. It was elucidated that atomic oxygen binds more strongly than nitrogen, with the most stable [Formula: see text] structure exhibiting a binding energy of -2.47 eV, indicating chemisorption onto the surface. Surface reconstructions were observed for the most stable minima of both atomic species. Positive workfunction changes were calculated for both adsorbed oxygen and nitrogen if the adsorbate interacted with zinc atoms. Negative workfunction changes were calculated when the adsorbate interacted with both surface oxygen and zinc atoms. Interactions between the adsorbate and the surface zinc atoms resulted in ionic-type bonding, whereas interactions with oxygen atoms were more likely to result in the formation of covalent-type bonding. The positive workfunction changes correlate with an experimentally observed increase in resistance of ZnO conductometric sensor devices.

  7. 2D quasi-ordered nitrogen-enriched porous carbon nanohybrids for high energy density supercapacitors

    NASA Astrophysics Data System (ADS)

    Kan, Kan; Wang, Lei; Yu, Peng; Jiang, Baojiang; Shi, Keying; Fu, Honggang

    2016-05-01

    Two-dimensional (2D) quasi-ordered nitrogen-enriched porous carbon (QNPC) nanohybrids, with the characteristics of an ultrathin graphite nanosheet framework and thick quasi-ordered nitrogen-doped carbon cladding with a porous texture, have been synthesized via an in situ polymerization assembly method. In the synthesis, the expandable graphite (EG) is enlarged by an intermittent microwave method, and then aniline monomers are intercalated into the interlayers of the expanded EG with the assistance of a vacuum. Subsequently, the intercalated aniline monomers could assemble on the interlayer surface of the expanded EG, accompanied by the in situ polymerization from aniline monomers to polyaniline. Meanwhile, the expanded EG could be exfoliated to graphite nanosheets. By subsequent pyrolysis and activation processes, the QNPC nanohybrids could be prepared. As supercapacitor electrodes, a typical QNPC12-700 sample derived from the precursor containing an EG content of 12%, with a high level of nitrogen doping of 5.22 at%, offers a high specific capacitance of 305.7 F g-1 (1 A g-1), excellent rate-capability and long-term stability. Notably, an extremely high energy density of 95.7 Wh kg-1 at a power density of 449.7 W kg-1 in an ionic liquid electrolyte can be achieved. The unique structural features and moderate heteroatom doping of the QNPC nanohybrids combines electrochemical double layer and faradaic capacitance contributions, which make these nanohybrids ideal candidates as electrode materials for high-performance energy storage devices.Two-dimensional (2D) quasi-ordered nitrogen-enriched porous carbon (QNPC) nanohybrids, with the characteristics of an ultrathin graphite nanosheet framework and thick quasi-ordered nitrogen-doped carbon cladding with a porous texture, have been synthesized via an in situ polymerization assembly method. In the synthesis, the expandable graphite (EG) is enlarged by an intermittent microwave method, and then aniline monomers are

  8. Coordinated regulation of nitrogen supply mode and initial cell density for energy storage compounds production with economized nitrogen utilization in a marine microalga Isochrysis zhangjiangensis.

    PubMed

    Chi, Lei; Yao, Changhong; Cao, Xupeng; Xue, Song

    2016-01-01

    Lipids and carbohydrates are main energy storage compounds (ESC) of microalgae under stressed conditions and they are potential feedstock for biofuel production. Yet, the sustainable and commercially successful production of ESC in microalgae needs to consider nitrogen utilization efficiency. Here the impact of different initial cell densities (ICDs) on ESC accumulation in Isochrysis zhangjiangensis under two nitrogen supply modes (an initially equal concentration of nitrogen per-cell in the medium (N1) and an equal total concentration of nitrogen in the culture system (N2)) were investigated. The results demonstrated that the highest ESC yield (1.36gL(-1)) at N1, which included a maximal nitrogen supply in the cultivation system, and the highest ESC content (66.5%) and ESC productivity per mass of nitrogen (3.28gg(-1) (N) day(-1)) at N2, were all obtained under a high ICD of 8.0×10(6)cellsmL(-1). Therefore I. zhangjiangensis qualifies for ESC-enriched biomass production with economized nitrogen utilization.

  9. High current transistor pulse generator

    SciTech Connect

    Nesterov, V.; Cassel, R.

    1991-05-01

    A solid state pulse generator capable of delivering high current trapezoidally shaped pulses into an inductive load has been developed at SLAC. Energy stored in the capacitor bank of the pulse generator is switched to the load through a pair of Darlington transistors. A combination of diodes and Darlington transistors is used to obtain trapezoidal or triangular shaped current pulses into an inductive load and to recover the remaining energy in the same capacitor bank without reversing capacitor voltage. The transistors work in the switch mode, and the power losses are low. The rack mounted pulse generators presently used at SLAC contain a 660 microfarad storage capacitor bank and can deliver 400 amps at 800 volts into inductive loads up to 3 mH. The pulse generators are used in several different power systems, including pulse to pulse bipolar power supplies and in application with current pulses distributed into different inductive loads. The current amplitude and discharge time are controlled by the central computer system through a specially developed multichannel controller. Several years of operation with the pulse generators have proven their consistent performance and reliability. 8 figs.

  10. High current metal ion implantation

    NASA Astrophysics Data System (ADS)

    Brown, Ian G.

    1990-04-01

    This report summarizes the research and development that has been carried out at Lawrence Berkeley Laboratory to develop a novel kind of high current metal ion source for metallurgical surface modification application. In ion implantation, an energetic ion beam is injected into a solid surface with the result that the surface composition is changed. For the case when the surface is a metal, the tribological properties of the new metallurgical surface can be significantly improved over the unimplanted surface. Previously, however, very intense metal ion beams have not been available, and this has been an impedance to the development of the field. With the MEVVA (Metal Vapor Vacuum Arc) ion source, metal ion beam currents of very high intensity have become available. This report outlines the progress made under the funded program in the four areas addressed: development of the MEVVA ion source for ion implantation application; research on the ion beam characteristics and behavior; development of the ion implantation facility; metallurgical ion implantation research that was performed.

  11. High current transistor pulse generator

    SciTech Connect

    Nesterov, V.; Cassel, R.

    1991-05-01

    A solid state pulse generator capable of delivering high current trapezoidally shaped pulses into an inductive load has been developed at SLAC. Energy stored in the capacitor bank of the pulse generator is switched to the load through a pair of Darlington transistors. A combination of diodes and Darlington transistors is used to obtain trapezoidal or triangular shaped current pulses into an inductive load and to recover the remaining energy in the same capacitor bank without reversing capacitor voltage. The transistors work in the switch mode, and the power losses are low. The rack mounted pulse generators presently used at SLAC contain a 660 microfarad storage capacitor bank and can deliver 400 amps at 800 volts into inductive loads up to 3 mH. The pulse generators are used in several different power systems, including pulse to pulse bipolar power supplies and in application with current pulses distributed into different inductive loads. The current amplitude and discharge time are controlled by the central computer system through a specially developed multichannel controller. Several years of operation with the pulse generators have proven their consistent performance and reliability. 8 figs.

  12. Manipulating Crop Density to Optimize Nitrogen and Water Use: An Application of Precision Agroecology

    NASA Astrophysics Data System (ADS)

    Brown, T. T.; Huggins, D. R.; Smith, J. L.; Keller, C. K.; Kruger, C.

    2011-12-01

    Rising levels of reactive nitrogen (Nr) in the environment coupled with increasing population positions agriculture as a major contributor for supplying food and ecosystem services to the world. The concept of Precision Agroecology (PA) explicitly recognizes the importance of time and place by combining the principles of precision farming with ecology creating a framework that can lead to improvements in Nr use efficiency. In the Palouse region of the Pacific Northwest, USA, relationships between productivity, N dynamics and cycling, water availability, and environmental impacts result from intricate spatial and temporal variations in soil, ecosystem processes, and socioeconomic factors. Our research goal is to investigate N use efficiency (NUE) in the context of factors that regulate site-specific environmental and economic conditions and to develop the concept of PA for use in sustainable agroecosystems and science-based Nr policy. Nitrogen and plant density field trials with winter wheat (Triticum aestivum L.) were conducted at the Washington State University Cook Agronomy Farm near Pullman, WA under long-term no-tillage management in 2010 and 2011. Treatments were imposed across environmentally heterogeneous field conditions to assess soil, crop and environmental interactions. Microplots with a split N application using 15N-labeled fertilizer were established in 2011 to examine the impact of N timing on uptake of fertilizer and soil N throughout the growing season for two plant density treatments. Preliminary data show that plant density manipulation combined with precision N applications regulated water and N use and resulted in greater wheat yield with less seed and N inputs. These findings indicate that improvements to NUE and agroecosystem sustainability should consider landscape-scale patterns driving productivity (e.g., spatial and temporal dynamics of water availability and N transformations) and would benefit from policy incentives that promote a PA

  13. Density functional theory study of nitrogen atoms and molecules interacting with Fe(1 1 1) surfaces

    NASA Astrophysics Data System (ADS)

    Nosir, M. A.; Martin-Gondre, L.; Bocan, G. A.; Díez Muiño, R.

    2016-09-01

    We present Density functional theory (DFT) calculations for the investigation of the structural relaxation of Fe(1 1 1), as well as for the study of the interaction of nitrogen atoms and molecules with this surface. We perform spin polarized DFT calculations using VASP (Vienna Ab-initio Simulation Package) code. We use the supercell approach and up to 19 slab layers for the relaxation of the Fe(1 1 1) surface. We find a contraction of the first two interlayer distances with a relative value of Δ12 = - 7.8 % and Δ23 = - 21.7 % with respect to the bulk reference. The third interlayer distance is however expanded with a relative change of Δ34 = 9.7 % . Early experimental studies of the surface relaxation using Low Energy Electron Diffraction (LEED) and Medium Energy Ion Scattering (MEIS) showed contradictory results, even on the relaxation general trend. Our current theoretical results support the LEED conclusions and are consistent qualitatively with other recent theoretical calculations. In addition, we study the interaction energy of nitrogen atoms and molecules on the Fe(1 1 1) surface. The nitrogen atoms are adsorbed in the hollow site of the unit cell, with an adsorption energy consistent with the one found in previous studies. In addition, we find the three molecularly adsorbed states that are observed experimentally. Two of them correspond to the adsorbed molecule oriented normal to the surface and a third one corresponds to the molecule adsorbed parallel to the surface. We conclude that our results are accurate enough to be used to build a full six-dimensional potential energy surface for the N2 system.

  14. Molecular nitrogen and methane density retrievals from Cassini UVIS dayglow observations of Titan's upper atmosphere

    NASA Astrophysics Data System (ADS)

    Stevens, Michael H.; Evans, J. Scott; Lumpe, Jerry; Westlake, Joseph H.; Ajello, Joseph M.; Bradley, E. Todd; Esposito, Larry W.

    2015-02-01

    We retrieve number densities of molecular nitrogen (N2) and methane (CH4) from Titan's upper atmosphere using the UV dayglow. We use Cassini Ultraviolet Imaging Spectrograph (UVIS) limb observations from 800 to 1300 km of the N I 1493 Å and N II 1085 Å multiplets, both produced directly from photofragmentation of N2. UVIS N2 and CH4 densities are in agreement with measurements from Cassini's Ion Neutral Mass Spectrometer (INMS) from the same flyby if INMS densities are scaled up by a factor of 3.0 as reported in previous studies. Analysis of three Cassini flybys of Titan shows that (1) the CH4 homopause on Titan is between 900 and 1100 km, (2) upper atmospheric temperatures vary by less than 10 K over 6 h at the same geographic location and (3) from 1100 to 1700 local solar time temperatures also vary by less than 10 K. The capability of retrieving the global-scale composition from these data complements existing techniques and significantly advances the study of upper atmospheric variability at Titan and for any other atmosphere with a detectable UV dayglow.

  15. Absolute nitrogen atom density measurements by two-photon laser-induced fluorescence spectroscopy in atmospheric pressure dielectric barrier discharges of pure nitrogen

    SciTech Connect

    Es-Sebbar, Et-Touhami; Sarra-Bournet, Christian; Naude, Nicolas; Gherardi, Nicolas; Massines, Francoise

    2009-10-01

    In this paper, two-photon absorption laser induced fluorescence spectroscopy is used to follow the nitrogen atom density in flowing dielectric barrier discharges fed with pure nitrogen and operating at atmospheric pressure. Two different dielectric barrier discharge regimes are investigated: the Townsend regime, which is homogeneous although operating at atmospheric pressure, and the more common filamentary regime. In both regimes, densities as high as 3x10{sup 14}/cm{sup 3} are detected. However, the N atoms kinetic formation depends on the discharge regime. The saturation level is reached more rapidly with a filamentary discharge. For a given discharge regime, the N atom density depends strongly on the energy dissipated in the plasma between the gas inlet and the measurement position, whether the energy is varied by varying the position of the measurements, the gas flow, or the dissipated power. Experiments performed in the postdischarge show that the N atom decay cannot be simply attributed to three-body recombination of atomic nitrogen with nitrogen molecules, meaning that other mechanisms such as surface recombination or gas impurities play a role.

  16. Sonoran Desert winter annuals affected by density of red brome and soil nitrogen

    USGS Publications Warehouse

    Salo, L.F.; McPherson, G.R.; Williams, D.G.

    2005-01-01

    Red brome [Bromus madritensis subsp. rubens (L.) Husn.] is a Mediterranean winter annual grass that has invaded Southwestern USA deserts. This study evaluated interactions among 13 Sonoran Desert annual species at four densities of red brome from 0 to the equivalent of 1200 plants ma??2. We examined these interactions at low (3 I?g) and high (537 I?g NO3a?? g soila??1) nitrogen (N) to evaluate the relative effects of soil N level on survival and growth of native annuals and red brome. Red brome did not affect emergence or survival of native annuals, but significantly reduced growth of natives, raising concerns about effects of this exotic grass on the fecundity of these species. Differences in growth of red brome and of the three dominant non nitrogen-fixing native annuals at the two levels of soil N were similar. Total species biomass of red brome was reduced by 83% at low, compared to high, N levels, whereas that of the three native species was reduced by from 42 to 95%. Mean individual biomass of red brome was reduced by 87% at low, compared to high, N levels, whereas that of the three native species was reduced by from 72 to 89%.

  17. Nitrogen electrochemically reduced to ammonia with hematite: density-functional insights.

    PubMed

    Nguyen, Manh-Thuong; Seriani, Nicola; Gebauer, Ralph

    2015-06-14

    Licht et al. (Science, 2014, 345, 637) recently proposed a procedure to synthesize NH3 from N2 and by steam electrolysis in molten hydroxide suspensions of nano-Fe2O3. This highly exciting investigation undoubtedly boosts the hope of the CO2-free and low-cost ammonia industry. To provide insights at the atomistic level into the reduction process of N2, we have carried out a density-functional study on the electrochemical formation of NH3 molecules on hematite(0001) surfaces. By considering associative and dissociative mechanisms, we have identified a reaction path that requires an applied bias of -1.1 V to allow the proton transfer processes to occur downhill. The most energy-demanding step is the addition of the first proton to the adsorbed molecular nitrogen. The computed bias is in good agreement with experimental electrolysis potentials that activate the electric current.

  18. High density nitrogen-vacancy sensing surface created via He{sup +} ion implantation of {sup 12}C diamond

    SciTech Connect

    Kleinsasser, Ed E.; Stanfield, Matthew M.; Banks, Jannel K. Q.; Zhu, Zhouyang; Li, Wen-Di; Acosta, Victor M.; Watanabe, Hideyuki; Itoh, Kohei M.; Fu, Kai-Mei C.

    2016-05-16

    We present a promising method for creating high-density ensembles of nitrogen-vacancy centers with narrow spin-resonances for high-sensitivity magnetic imaging. Practically, narrow spin-resonance linewidths substantially reduce the optical and RF power requirements for ensemble-based sensing. The method combines isotope purified diamond growth, in situ nitrogen doping, and helium ion implantation to realize a 100 nm-thick sensing surface. The obtained 10{sup 17 }cm{sup −3} nitrogen-vacancy density is only a factor of 10 less than the highest densities reported to date, with an observed 200 kHz spin resonance linewidth over 10 times narrower.

  19. Nitrogen

    USGS Publications Warehouse

    Kramer, D.A.

    2006-01-01

    In 2005, ammonia was produced by 15 companies at 26 plants in 16 states in the United States. Of the total ammonia production capacity, 55% was centered in Louisiana, Oklahoma and Texas because of their large reserves of natural gas. US producers operated at 66% of their rated capacity. In descending order, Koch Nitrogen, Terra Industries, CF Industries, Agrium and PCS Nitrogen accounted for 81% of the US ammonia production capacity.

  20. Revising the slant column density retrieval of nitrogen dioxide observed by the Ozone Monitoring Instrument

    NASA Astrophysics Data System (ADS)

    Marchenko, S.; Krotkov, N. A.; Lamsal, L. N.; Celarier, E. A.; Swartz, W. H.; Bucsela, E. J.

    2015-06-01

    Nitrogen dioxide retrievals from the Aura/Ozone Monitoring Instrument (OMI) have been used extensively over the past decade, particularly in the study of tropospheric air quality. Recent comparisons of OMI NO2 with independent data sets and models suggested that the OMI values of slant column density (SCD) and stratospheric vertical column density (VCD) in both the NASA OMNO2 and Royal Netherlands Meteorological Institute DOMINO products are too large, by around 10-40%. We describe a substantially revised spectral fitting algorithm, optimized for the OMI visible light spectrometer channel. The most important changes comprise a flexible adjustment of the instrumental wavelength shifts combined with iterative removal of the ring spectral features; the multistep removal of instrumental noise; iterative, sequential estimates of SCDs of the trace gases in the 402-465 nm range. These changes reduce OMI SCD(NO2) by 10-35%, bringing them much closer to SCDs retrieved from independent measurements and models. The revised SCDs, submitted to the stratosphere-troposphere separation algorithm, give tropospheric VCDs ˜10-15% smaller in polluted regions, and up to ˜30% smaller in unpolluted areas. Although the revised algorithm has been optimized specifically for the OMI NO2 retrieval, our approach could be more broadly applicable.

  1. Electronic structure and spatial distribution of the spin density of shallow nitrogen donors in the SiC lattice

    NASA Astrophysics Data System (ADS)

    Muzafarova, M. V.; Il'in, I. V.; Anisimov, A. N.; Mokhov, E. N.; Soltamov, V. A.; Baranov, P. G.

    2016-12-01

    The discovery of unique magnetooptical properties of paramagnetic centers in silicon carbide, which make it possible to control spins of small arrays of centers of atomic sizes to single centers at room temperatures, using the techniques of optical detection of the magnetic resonance, posed a number of problems, among which one of the main ones is the creation of conditions under which spin relaxation effects are minimized. As studies of properties of spin nitrogen-vacancy centers in diamond showed, the main contribution to spin relaxation is made by the interaction with nitrogen donors, being a major impurity in diamond. A similar problem exists for silicon carbide, since nitrogen donors are also basic background impurities. The objective of this work is to study the spatial distribution of the spin density of nitrogen donors in two basic silicon carbide polytypes, i.e., 4 H-SiC and 6 H-SiC, to use this information for minimizing the interaction of nitrogen donors with paramagnetic centers in silicon carbide. The results of the study are analyzed by magnetic resonance methods; the spin density distribution on the nearest coordination spheres of nitrogen donors occupying carbon sites in silicon carbide is determined. It is concluded that paramagnetic centers in the 4 H-SiC polytype, including silicon vacancies, can be more stable to the interactions with unpaired donor electrons, since electrons are not localized on the coordination sphere closest to the paramagnetic center in this case.

  2. Nitrogen

    USGS Publications Warehouse

    Apodaca, L.E.

    2012-01-01

    Ammonia was produced by 12 companies at 27 plants in 15 states in the United States during 2011. Sixty-one percent of total U.S. ammonia production capacity was centered in Louisiana, Oklahoma and Texas because of those states' large reserves of natural gas, the dominant domestic feedstock. In 2011, U.S. producers operated at about 84 percent of their rated capacity (excluding plants that were idle for the entire year). Four companies — CF Industries Holdings Inc.; Koch Nitrogen Co.; PCS Nitrogen Inc. and Agrium Inc., in descending order — accounted for 77 percent of the total U.S. ammonia production capacity.

  3. High current regimes in RFX-mod

    NASA Astrophysics Data System (ADS)

    Valisa, M.; Bolzonella, T.; Buratti, P.; Carraro, L.; Cavazzana, R.; Dal Bello, S.; Martin, P.; Pasqualotto, R.; Sarff, J. S.; Spolaore, M.; Zanca, P.; Zanotto, L.; Agostini, M.; Alfier, A.; Antoni, V.; Apolloni, L.; Auriemma, F.; Barana, O.; Baruzzo, M.; Bettini, P.; Bonfiglio, D.; Bonomo, F.; Brombin, M.; Buffa, A.; Canton, A.; Cappello, S.; Cavinato, M.; Chitarin, G.; DeLorenzi, A.; DeMasi, G.; Escande, D. F.; Fassina, A.; Franz, P.; Gaio, E.; Gazza, E.; Giudicotti, L.; Gnesotto, F.; Gobbin, M.; Grando, L.; Guazzotto, L.; Guo, S. C.; Igochine, V.; Innocente, P.; Lorenzini, R.; Luchetta, A.; Manduchi, G.; Marchiori, G.; Marcuzzi, D.; Marrelli, L.; Martini, S.; Martines, E.; McCollam, K.; Milani, F.; Moresco, M.; Novello, L.; Ortolani, S.; Paccagnella, R.; Peruzzo, S.; Piovan, R.; Piron, L.; Pizzimenti, A.; Piovesan, P.; Pomaro, N.; Predebon, I.; Puiatti, M. E.; Rostagni, G.; Sattin, F.; Scarin, P.; Serianni, G.; Sonato, P.; Spada, E.; Soppelsa, A.; Spagnolo, S.; Spizzo, G.; Taliercio, C.; Terranova, D.; Toigo, V.; Vianello, N.; Yadikin, D.; Zaccaria, P.; Zaniol, B.; Zilli, E.; Zuin, M.

    2008-12-01

    Optimization of machine operation, including plasma position control, density control and especially feedback control on multiple magnetohydrodynamic modes, has led RFX-mod to operate reliably at 1.5 MA, the highest current ever achieved on a reversed field pinch (RFP). At high current and low density the magnetic topology spontaneously self-organizes in an Ohmical helical symmetry, with the new magnetic axis helically twisting around the geometrical axis of the torus. The separatrix of the island disappears leaving a wide and symmetric thermal structure with large gradients in the electron temperature profile. The new topology still displays an intermittent nature but its overall presence has reached 85% of the current flat-top period. The large gradients in the electron temperature profile appear to be marginal for the destabilization of ion temperature gradient modes on the assumption that ions and electrons have the same gradients. There are indications that higher currents could provide the conditions under which to prove the existence of a true helical equilibrium as the standard RFP configuration.

  4. Nitrogen

    USGS Publications Warehouse

    Kramer, D.A.

    2004-01-01

    Ammonia is the principal source of fixed nitrogen. It was produced by 17 companies at 34 plants in the United States during 2003. Fifty-three percent of U.S. ammonia production capacity was centered in Louisiana, Oklahoma and Texas because of their large reserves of natural gas, the dominant domestic feedstock.

  5. Nitrogen

    USGS Publications Warehouse

    Kramer, D.A.

    2007-01-01

    Ammonia was produced by 15 companies at 25 plants in 16 states in the United States during 2006. Fifty-seven percent of U.S. ammonia production capacity was centered in Louisiana, Oklahoma and Texas because of their large reserves of natural gas, the dominant domestic feedstock. In 2006, U.S. producers operated at about 72 percent of their rated capacity (excluding plants that were idle for the entire year). Five companies, Koch Nitrogen, Terra Industries, CF Industries, PCS Nitro-gen, and Agrium, in descending order, accounted for 79 percent U.S. ammonia production capacity. The United States was the world's fourth-ranked ammonia producer and consumer following China, India and Russia. Urea, ammonium nitrate, ammonium phosphates, nitric acid and ammonium sulfate were the major derivatives of ammonia in the United States, in descending order of importance.

  6. Nitrogen

    USGS Publications Warehouse

    Apodaca, L.E.

    2010-01-01

    Ammonia was produced by 13 companies at 23 plants in 16 states during 2009. Sixty percent of all U.S. ammonia production capacity was centered in Louisiana. Oklahoma and Texas because of those states' large reserves of natural gas, the dominant domestic feedstock. In 2009, U.S. producers operated at about 83 percent of their rated capacity (excluding plants that were idle for the entire year). Five companies — Koch Nitrogen Co.; Terra Industries Inc.; CF Industries Inc.; PCS Nitrogen Inc. and Agrium Inc., in descending order — accounted for 80 percent of the total U.S. ammonia production capacity. U.S. production was estimated to be 7.7 Mt (8.5 million st) of nitrogen (N) content in 2009 compared with 7.85 Mt (8.65 million st) of N content in 2008. Apparent consumption was estimated to have decreased to 12.1 Mt (13.3 million st) of N, a 10-percent decrease from 2008. The United States was the world's fourth-ranked ammonia producer and consumer following China, India and Russia. Urea, ammonium nitrate, ammonium phosphates, nitric acid and ammonium sulfate were the major derivatives of ammonia in the United States, in descending order of importance.

  7. Evidence for composition variations and impurity segregation at grain boundaries in high current-density polycrystalline K- and Co-doped BaFe{sub 2}As{sub 2} superconductors

    SciTech Connect

    Kim, Yoon-Jun; Weiss, Jeremy D.; Hellstrom, Eric E.; Larbalestier, David C.; Seidman, David N.

    2014-10-20

    Some polycrystalline forms of the K- and Co-doped BaFe{sub 2}As{sub 2} and SrFe{sub 2}As{sub 2} superconductors now have a critical current density (J{sub c}) within a factor of ∼5 of that required for real applications, even though it is known that some grain boundaries (GBs) block current, thus, raising the question of whether this blocking is intrinsic or extrinsically limited by artefacts amenable to improvement by better processing. Herein, we utilize atom-probe tomography (APT) to study the grain and GB composition in high J{sub c} K- and Co-doped BaFe{sub 2}As{sub 2} polycrystals. We find that all GBs studied show significant compositional variations on the scale of a few coherence lengths (ξ), as well as strong segregation of oxygen impurities, which we believe are largely introduced in the starting materials. Importantly, these findings demonstrate that APT enables quantitative analysis of the highest J{sub c} K-doped BaFe{sub 2}As{sub 2} samples, where analytical transmission electron microscopy (TEM) fails because of the great reactivity of thin TEM samples. The observations of major chemical perturbations at GBs make us cautiously optimistic that there is a large extrinsic component to the GB current blocking, which will be ameliorated by better processing, for which APT will likely be a crucial instrument.

  8. Analysis of Mexico City urban air pollution using nitrogen dioxide column density measurements from UV/Visible spectroscopy

    NASA Astrophysics Data System (ADS)

    Garcia Payne, D. G.; Grutter, M.; Melamed, M. L.

    2010-12-01

    The differential optical absorption spectroscopy method (DOAS) was used to get column densities of nitrogen dioxide (NO2) from the analysis of zenith sky UV/visible spectra. Since the optical path length provides critical information in interpreting NO2 column densities, in conjunction with NO2 column densities, the oxygen dimer (O4) column density was retrieved to give insight into the optical path length. We report observations of year round NO2 and O4 column densities (from august 2009 to september 2010) from which the mean seasonal levels and the daily evolution, as well as the occurrence of elevated pollution episodes are examined. Surface nitric oxide (NO) and NO2 from the local monitoring network, as well as wind data and the vertical aerosol density from continuous Lidar measurements are used in the analysis to investigate specific events in the context of local emissions from vehicular traffic, photochemical production and transport from industrial emissions. The NO2 column density measurements will enhance the understanding Mexico City urban air pollution. Recent research has begun to unravel the complexity of the air pollution problem in Mexico City and its effects not only locally but on a regional and global scale as well.

  9. Gamma-resonance Contraband Detection using a high current tandem accelerator

    SciTech Connect

    Milton, B. F.; Beis, J.; Dale, D.; Rogers, J.; Ruegg, R.; Debiak, T.; Kamykowski, E.; Melnychuk, S.; Rathke, J.; Sredniawski, J.

    1999-04-26

    TRIUMF and Northrop Grumman have developed a new system for the detection of concealed explosives and drugs. This Contraband Detection System (CDS) is based on the resonant absorption by {sup 14}N of gammas produced using {sup 13}C(p,{gamma}){sup 14}N. The chosen reaction uses protons at 1.75 MeV and the gammas have an energy of 9.17 MeV. By measuring both the resonant and the non-resonant absorption using detectors with good spatial resolution, and applying standard tomographic techniques, we are able to produce 3D images of both the nitrogen partial density and the total density. The images together may be utilized with considerable confidence to determine if small amounts of nitrogen based explosives, heroin or cocaine are present in the interrogated containers. Practical Gamma Resonant Absorption (GRA) scanning requires an intense source of protons. However this proton source must also be very stable, have low energy spread, and have good spatial definition. These demands suggested a tandem as the accelerator of choice. We have therefore constructed a 2 MeV H{sup -} tandem optimized for high current (10 mA) operation, while minimizing the overall size of the accelerator. This has required several special innovations which will be presented in the paper. We will also present initial commissioning results.

  10. Importance of network density of nanotube: Effect on nitrogen dioxide gas sensing by solid state resistive sensor

    SciTech Connect

    Mishra, Prabhash; Grachyova, D. V.; Moskalenko, A. S.; Shcherbak, M. A.; Pavelyev, V. S.

    2016-04-13

    Dispersion of single-walled carbon nanotubes (SWCNTs) is an established fact, however, its effect on toxic gas sensing for the development of solid state resistive sensor was not well reported. In this report, the dispersion quality of SWCNTs has been investigated and improved, and this well-dispersed SWCNTs network was used for sensor fabrication to monitor nitrogen dioxide gas. Ultraviolet (UV)-visible spectroscopic studies shows the strength of SWNTs dispersion and scanning electron microscopy (SEM) imaging provides the morphological properties of the sensor device. In this gas sensor device, two sets of resistive type sensors were fabricated that consisting of a pair of interdigitated electrodes (IDEs) using dielectrophoresis technique with different SWCNTs network density. With low-density SWCNTs networks, this fabricated sensor exhibits a high response for nitrogen dioxide sensing. The sensing of nitrogen dioxide is mainly due to charge transfer from absorbed molecules to sidewalls of nanotube and tube-tube screening acting a major role for the transport properties of charge carriers.

  11. Importance of network density of nanotube: Effect on nitrogen dioxide gas sensing by solid state resistive sensor

    NASA Astrophysics Data System (ADS)

    Mishra, Prabhash; Grachyova, D. V.; Moskalenko, A. S.; Shcherbak, M. A.; Pavelyev, V. S.

    2016-04-01

    Dispersion of single-walled carbon nanotubes (SWCNTs) is an established fact, however, its effect on toxic gas sensing for the development of solid state resistive sensor was not well reported. In this report, the dispersion quality of SWCNTs has been investigated and improved, and this well-dispersed SWCNTs network was used for sensor fabrication to monitor nitrogen dioxide gas. Ultraviolet (UV)-visible spectroscopic studies shows the strength of SWNTs dispersion and scanning electron microscopy (SEM) imaging provides the morphological properties of the sensor device. In this gas sensor device, two sets of resistive type sensors were fabricated that consisting of a pair of interdigitated electrodes (IDEs) using dielectrophoresis technique with different SWCNTs network density. With low-density SWCNTs networks, this fabricated sensor exhibits a high response for nitrogen dioxide sensing. The sensing of nitrogen dioxide is mainly due to charge transfer from absorbed molecules to sidewalls of nanotube and tube-tube screening acting a major role for the transport properties of charge carriers.

  12. Diet density during the first week of life: Effects on energy and nitrogen balance characteristics of broiler chickens.

    PubMed

    Lamot, D M; Sapkota, D; Wijtten, P J A; van den Anker, I; Heetkamp, M J W; Kemp, B; van den Brand, H

    2017-07-01

    This study aimed to determine effects of diet density on growth performance, energy balance, and nitrogen (N) balance characteristics of broiler chickens during the first wk of life. Effects of diet density were studied using a dose-response design consisting of 5 dietary fat levels (3.5, 7.0, 10.5, 14.0, and 17.5%). The relative difference in dietary energy level was used to increase amino acid levels, mineral levels, and the premix inclusion level at the same ratio. Chickens were housed in open-circuit climate respiration chambers from d 0 to 7 after hatch. Body weight was measured on d 0 and 7, whereas feed intake was determined daily. For calculation of energy balances, O2 and CO2 exchange were measured continuously and all excreta from d 0 to 7 was collected and analyzed at d 7. Average daily gain (ADG) and average daily feed intake (ADFI) decreased linearly (P = 0.047 and P < 0.001, respectively), whereas gain to feed ratio increased (P < 0.001) with increasing diet density. Gross energy (GE) intake and metabolizable energy (ME) intake were not affected by diet density, but the ratio between ME and GE intake decreased linearly with increasing diet density (P = 0.006). Fat, N, and GE efficiencies (expressed as gain per unit of nutrient intake), heat production, and respiratory exchange ratio (CO2 to O2 ratio) decreased linearly (P < 0.001) as diet density increased. Energy retention, N intake, and N retention were not affected by diet density. We conclude that a higher diet density in the first wk of life of broiler chickens did not affect protein and fat retention, whereas the ME to GE ratio decreased linearly with increased diet density. This suggests that diet density appears to affect digestibility rather than utilization of nutrients. © 2017 Poultry Science Association Inc.

  13. Nitrogen Concentration and Load Patterns in Four Headwater Streams With a Gradient in Onsite Wastewater Treatment System Density

    NASA Astrophysics Data System (ADS)

    Radcliffe, D. E.

    2016-12-01

    In previous work where we measured nitrogen (N) concentrations in 24 small watersheds in Metropolitan Atlanta under base flow conditions, we found that most of the base-flow N originated from onsite wastewater treatment systems (OWTS) in watersheds with a high density of OWTS and from agriculture in watersheds with a low density of OWTS. However, the fraction of the total annual N load represented by the base-flow N concentrations could not be estimated because N concentrations were not sampled during storm events and there were no continuous measurements of stream flow. Our objective in this study was to determine the fraction of the total annual N load represented by base-flow N in four headwater streams with a gradient in OWTS density. The four streams selected from our original study had OWTS densities ranging from 20-230 systems km-2. From October 2012 to April 2014, stream discharge was measured at 15-min intervals and storm-flow and base-flow samples were collected using automated samplers. Nitrate (NO3-) concentrations were higher in base-flow than in storm-flow in three of the four streams, indicating a groundwater source of NO3-. TN loads were highest for the stream with the lowest OWTS density and the stream with the highest OWTS density. We attribute this to the effect of agriculture in the low density watershed and OWTS in the high density watershed. N loads at the extremes in OWTS densities in our study were comparable to high loads cited in the literature for pastures and suburban areas on OWTS. In the watershed with the highest OWTS density, base flow NO3- loads accounted for about 35% the total N loads. This indicates the important effect of OWTS on stream N loads.

  14. Optimized nested Markov chain Monte Carlo sampling: application to the liquid nitrogen Hugoniot using density functional theory

    SciTech Connect

    Shaw, Milton Sam; Coe, Joshua D; Sewell, Thomas D

    2009-01-01

    An optimized version of the Nested Markov Chain Monte Carlo sampling method is applied to the calculation of the Hugoniot for liquid nitrogen. The 'full' system of interest is calculated using density functional theory (DFT) with a 6-31 G* basis set for the configurational energies. The 'reference' system is given by a model potential fit to the anisotropic pair interaction of two nitrogen molecules from DFT calculations. The EOS is sampled in the isobaric-isothermal (NPT) ensemble with a trial move constructed from many Monte Carlo steps in the reference system. The trial move is then accepted with a probability chosen to give the full system distribution. The P's and T's of the reference and full systems are chosen separately to optimize the computational time required to produce the full system EOS. The method is numerically very efficient and predicts a Hugoniot in excellent agreement with experimental data.

  15. Numerical investigation on boiling flow of liquid nitrogen in a vertical tube using bubble number density approach

    NASA Astrophysics Data System (ADS)

    Shao, Xuefeng; Li, Xiangdong; Wang, Rongshun

    2016-04-01

    An average bubble number density (ABND) model was formulated and numerically resolved for the subcooled flow boiling of liquid nitrogen. The effects of bubble coalescence and breakup were taken into account. Some new closure correlations describing bubble nucleation and departure on the heating surface were selected as well. For the purpose of comparison, flow boiling of liquid nitrogen was also numerically simulated using a modified two-fluid model. The results show that the simulations performed by using the ABND model achieve encouraging improvement in accuracy in predicting heat flux and wall temperature of a vertical tube. Moreover, the influence of the bubble coalescence and breakup is shown to be great on predicting overall pressure beyond the transition point.

  16. HIGH CURRENT SUPERCONDUCTING CAVITIES AT RHIC.

    SciTech Connect

    CALAGA,R.BEN-ZVI,I.ZHAO,Y.ET AL.

    2004-07-05

    A five-cell high current superconducting cavity for the electron cooling project at RHIC is under fabrication. Higher order modes (HOMs), one of main limiting factors for high current energy-recovery operation, are under investigation. Calculations of HOMs using time-domain methods in Mafia will be discussed and compared to calculations in the frequency domain. Beam breakup thresholds determined from numerical codes for the five-cell cavity will be presented. A possible motivation towards a 2 x 2 superstructure using the current five-cell design will also be discussed.

  17. Response of Soil Bulk Density and Mineral Nitrogen to Harvesting and Cultural Treatments

    Treesearch

    Minyi Zhou; Mason C. Carter; Thomas J. Dean

    1998-01-01

    The interactive effects of harvest intensity, site preparation, and fertilization on soil compaction and nitrogen mineralization were examined in a loblolly pine (Pinus taeda L.) stand growing on a sandy, well-drained soil in eastern Texas. The experimental design was 2 by 2 by 2 factorial, consisting of two harvesting treatments (mechanical whole-...

  18. Heat extraction from targets in high current electron beams

    NASA Astrophysics Data System (ADS)

    Bubb, Ernest; Altemus, Rosemary; McCarthy, James; Biron, Don

    1982-12-01

    Various aspects of heat extraction from targets in high current electron beams are examined, among which are the dependences on boundary temperature, beam current density, and convective effects from an ambient gaseous environment. The design of a cooling system which extracts heat by forcing hydrogen (or helium) gas at a pressure of several Torr at near sonic velocities across a target surface is described. Boundary layer theory calculations and empirical measurements of the average heat transfer coefficient for the system are presented.

  19. Stand Density Effects on Biomass Allocation Patterns and Subsequent Soil Nitrogen Demand

    Treesearch

    Christopher A. Dicus; Thomas J. Dean

    1998-01-01

    Growth and yield data from a loblolly pine plantation in southeastern Louisiana were obtained yearly from 1993 to 1996 on numbered trees within two stands initially planted on a 1.22- by 1.22-meter spacing, and two stands planted on a 2.44- by 2.44-meter spacing. Using allometric equations derived from a 1994 on-site destructive harvest, cited nitrogen...

  20. DC negative corona discharge characteristics in high density nitrogen in point-plane configuration

    SciTech Connect

    Hernandez-Avila, H.L.; Nur, M.; Bonifaci, N.; Denat, A.

    1995-12-31

    Some investigations of corona discharges in pure nitrogen have been published but they were devoted to a range of low or medium pressure (P{<=}0.1 MPa). This paper deals with the behaviour of corona discharges in negative point-plane configuration in very pure nitrogen under high-pressure (from 0.5 MPa to 10 MPa). The first one, called the low current region appears immediately after the threshold voltage V{sub o} is reached. For higher voltages (V>V{sub o}), a high continuous glow current region is obtained. In addition with these two discharge regions, we can sometimes observe one intermediate region which looks like to a Trichel-like pulse regime. Consequently, in this non electronegative gas, several modes of current discharge can be distinguished on the current-voltage characteristics. In the same conditions in high pressure air - a weakly electronegative gas - only one mode of current discharge controlled by negative ions can be observed. Some assumptions about the physical mechanisms leading to these phenomena in nitrogen are discussed.

  1. High Current Ion Source Development for Heavy Ion Fusion

    SciTech Connect

    Westenskow, G A; Grote, D P; Kwan, J W

    2003-09-04

    We are developing high-current-density high-brightness sources for Heavy Ion Fusion applications. Heavy ion driven inertial fusion requires beams of high brightness in order to achieve high power density at the target for high target gain. At present, there are no existing ion source types that can readily meet all the driver HIF requirements, though sources exist which are adequate for present experiments and which with further development may achieve driver requirements. Our two major efforts have been on alumino-silicate sources and RF plasma sources. Experiments being performed on a 10-cm alumino-silicate source are described. To obtain a compact system for a HIF driver we are studying RF plasma sources where low current beamlets are combined to produce a high current beam. A 80-kV 20-{micro}s source has produced up to 5 mA of Ar{sup +} in a single beamlet. The extraction current density was 100 mA/cm{sup 2}. We present measurements of the extracted current density as a function of RF power and gas pressure, current density uniformity, emittance, and energy dispersion (due to charge exchange).

  2. Chemical sputtering of graphite by low temperature nitrogen plasmas at various substrate temperatures and ion flux densities

    SciTech Connect

    Bystrov, K.; Morgan, T. W.; Tanyeli, I.; De Temmerman, G.; Sanden, M. C. M. van de

    2013-10-07

    We report measurements of chemical sputtering yields of graphite exposed to low temperature nitrogen plasmas. The influence of surface temperature and incoming ion energy on the sputtering yields has been investigated in two distinct ion flux density regimes. Sputtering yields grow consistently with increasing temperatures in experiments with low flux density (Γ{sub i}≈10{sup 20} m{sup −2}s{sup −1}−10{sup 21} m{sup −2}s{sup −1}) and high flux density (Γ{sub i}≈10{sup 23} m{sup −2}s{sup −1}). Moreover, empirical fitting of the data suggests that the temperature of 670 °C is optimal for chemical sputtering at high flux density. Negative biasing of the samples was used to vary the ion energy in the low flux density regime. The sputtering yield in this case increases from 0.07 atoms/ion for E{sub i} = 1.5 eV to 0.19 atoms/ion for E{sub i} = 35 eV. After taking into account the dependence of the yields on temperature and ion energy, we evidenced a flux dependence of sputtering, similar to that found for chemical sputtering of carbon by hydrogen.

  3. A high plant density reduces the ability of maize to use soil nitrogen.

    PubMed

    Yan, Peng; Pan, Junxiao; Zhang, Wenjie; Shi, Junfang; Chen, Xinping; Cui, Zhenling

    2017-01-01

    Understanding the physiological changes associated with high grain yield and high N use efficiency (NUE) is important when increasing the plant density and N rate to develop optimal agronomic management. We tested the hypothesis that high plant densities resulting in crowding stress reduce the ability of plants to use the N supply post-silking, thus decreasing the grain yield and NUE. In 2013 and 2014, a field experiment, with five N-application rates and three plant densities (6.0, 7.5, and 9.0 plants m-2), was conducted in the North China Plain (NCP). The calculated maximum grain yield and agronomic use efficiency (AEN) at a density of 7.5 plants m-2 were 12.4 Mg ha-1 and 39.3 kg kg-1, respectively, which were significantly higher than the values obtained at densities of 6.0 (11.3 Mg ha-1 and 30.2 kg kg-1) and 9.0 plant m-2 (11.7 Mg ha-1 and 27.8 kg kg-1). A high plant density of 9.0 plants m-2 decreased the post-silking N accumulation, leaf N concentration and net photosynthesis, which reduced the post-silking dry matter production, resulting in a low yield and NUE. Although a relatively low grain yield was observed at a density of 9.0 plants m-2, the optimal N rate increased from 150 to 186 kg N ha-1 at a density of 7.5 plants m-2. These results indicate that high plant densities with crowding stress reduce the ability of plants to use soil N during the post-silking period, and high rate of N fertilizer was needed to increase grain yield. We conclude that selecting the appropriate plant density combined with optimal N management could increase grain yields and the NUE in the NCP.

  4. A high plant density reduces the ability of maize to use soil nitrogen

    PubMed Central

    Yan, Peng; Pan, Junxiao; Zhang, Wenjie; Shi, Junfang; Chen, Xinping; Cui, Zhenling

    2017-01-01

    Understanding the physiological changes associated with high grain yield and high N use efficiency (NUE) is important when increasing the plant density and N rate to develop optimal agronomic management. We tested the hypothesis that high plant densities resulting in crowding stress reduce the ability of plants to use the N supply post-silking, thus decreasing the grain yield and NUE. In 2013 and 2014, a field experiment, with five N-application rates and three plant densities (6.0, 7.5, and 9.0 plants m–2), was conducted in the North China Plain (NCP). The calculated maximum grain yield and agronomic use efficiency (AEN) at a density of 7.5 plants m–2 were 12.4 Mg ha–1 and 39.3 kg kg–1, respectively, which were significantly higher than the values obtained at densities of 6.0 (11.3 Mg ha–1 and 30.2 kg kg–1) and 9.0 plant m–2 (11.7 Mg ha–1 and 27.8 kg kg–1). A high plant density of 9.0 plants m–2 decreased the post-silking N accumulation, leaf N concentration and net photosynthesis, which reduced the post-silking dry matter production, resulting in a low yield and NUE. Although a relatively low grain yield was observed at a density of 9.0 plants m–2, the optimal N rate increased from 150 to 186 kg N ha-1 at a density of 7.5 plants m–2. These results indicate that high plant densities with crowding stress reduce the ability of plants to use soil N during the post-silking period, and high rate of N fertilizer was needed to increase grain yield. We conclude that selecting the appropriate plant density combined with optimal N management could increase grain yields and the NUE in the NCP. PMID:28234970

  5. Increased nitrogen deposition did not affect the composition and turnover of plant and microbial biomarkers in forest soil density fractions

    NASA Astrophysics Data System (ADS)

    Griepentrog, Marco; Bodé, Samuel; Boeckx, Pascal; Hagedorn, Frank; Wiesenberg, Guido L. B.; Schmidt, Michael W. I.

    2013-04-01

    Increased atmospheric nitrogen (N) deposition and elevated CO2 concentrations affect many forests and their ecosystem functions, including organic matter cycling in soils, the largest carbon pool of terrestrial ecosystems. However, it is still not clear how, and what the underlying mechanisms are. Specific molecules of plant and microbial origin (biomarkers) might respond differently to N deposition, depending on their internal N content. Microbial cell-wall-constituents with high-N content like amino sugars are reliable biomarkers to distinguish between fungal- and bacterial-derived organic residues. Individual lipids are plant-specific biomarkers that lack N in their molecular structure. Here, we tested the effects of elevated CO2 and increased N deposition on the dynamics of plant and microbial biomarkers by studying their composition and turnover in forest soil density fractions. Furthermore, we tested the hypothesis that these biomarkers respond differently to increased N deposition, depending on their internal N content. We used soil samples from a 4-year elevated CO2 and N deposition experiment in model forest ecosystems (open-top chambers), that were fumigated with ambient and 13C-depleted CO2 and treated with two levels of 15N-labeled fertilizer. Bulk soil was separated into free light fraction, occluded light fraction and heavy fraction by density fractionation and ultrasonic dispersion. The heavy fraction was further particle-size fractionated with 20 μm as a cut-off. We determined carbon and N concentrations and their isotopic compositions (δ13C, δ15N) within bulk soil and density fractions. Therein, we extracted and quantified individual amino sugars and lipids and conducted compound-specific stable-isotope-analysis using GC- and LC-IRMS. Results show that amino sugars were mainly stabilized in association with soil minerals. Especially bacterial amino sugars were preferentially associated with soil minerals, exemplified by a consistent decrease

  6. Phytofiltration of arsenic-contaminated groundwater using Pteris vittata L.: effect of plant density and nitrogen and phosphorus levels.

    PubMed

    Natarajan, Seenivasan; Stamps, Robert H; Saha, Uttam K; Ma, Lena Q

    2008-01-01

    This field-scale hydroponic experiment investigated the effects of plant density and nutrient levels on arsenic (As) removal by the As-hyperaccumulator Pteris vittata L. (Chinese brake fern). All ferns were grown in plastic tanks containing 30 L of As-contaminated groundwater (130 microg x L(-1) As) collected from South Florida. The treatments consisted of four plant densities (zero, one, two, or four plants per 30 L), two nitrogen (N) concentrations (50% or 100% of 0.25-strength Hoagland solution [HS]), and two phosphorous (P) concentrations (15% and 30% of 0.25 strength HS). While low P was more effective than high P for plant As removal initially, N levels showed little effect. At 15% P, it took 3 wk for the ferns at a plant density of four to reduce As to less than 10 microg L(-1) (USEPA and WHO standard), whereas it took 4-6 wk at plant densities of one or two. For reused ferns, established plants with more extensive roots than "first-time" ferns, a low plant density of one plant/30 L was more effective, reducing As in water to less than 10 microg L(-1) in 8 h. This translates to an As removal rate of 400 microg h(-l) plant(-1), which is the highest rate reported to date. Arsenic-concentration in tanks with no plants as a control remained high throughout the experiment. Using more established ferns supplemented with dilute nutrients (0.25 HS with 25% N and 15% P) with optimized plant density (one plant per 30 L) reduced interplant competition and secondary contamination from nutrients, and can be recommended for phytofiltration of As-contaminated groundwater. This study demonstrated that P. vittata is effective in remediating As-contaminated groundwater to meet recommended standards.

  7. HIGH CURRENT RADIO FREQUENCY ION SOURCE

    DOEpatents

    Abdelaziz, M.E.

    1963-04-01

    This patent relates to a high current radio frequency ion source. A cylindrical plasma container has a coil disposed around the exterior surface thereof along the longitudinal axis. Means are provided for the injection of an unionized gas into the container and for applying a radio frequency signal to the coil whereby a radio frequency field is generated within the container parallel to the longitudinal axis thereof to ionize the injected gas. Cathode and anode means are provided for extracting transverse to the radio frequency field from an area midway between the ends of the container along the longitudinal axis thereof the ions created by said radio frequency field. (AEC)

  8. Optimum Leaf Removal Increases Nitrogen Accumulation in Kernels of Maize Grown at High Density

    PubMed Central

    Liu, Tiening; Huang, Rundong; Cai, Tie; Han, Qingfang; Dong, Shuting

    2017-01-01

    Increasing plant density is one of the main approaches of achieving higher yields for modern maize crop. However, there exists leaf redundancy for high-density maize, and leaves of the upper canopy shade more competent leaves at the middle strata. In a two-year field experiments, Jinhai5, a semi-compact corn cultivar, was grown at a density of 105,000 plants ha−1 grown until 3 days after silking (3DAS), when plants were subjected to removal of the uppermost two leaves (S2), four leaves (S4) or six leaves (S6), with no leaf removal as control (S0). We evaluated the effects of leaf removal on N remobilization, photosynthetic capacity of the remaining leaves for N uptake, and N accumulation in kernels. Our present results concluded that, under high plant density, excising the uppermost two leaves promoted N remobilization from vegetative organs to kernels and enhanced photosynthetic capacity for N uptake, leading to an increased N accumulation in kernels (19.6% higher than control). However, four or six uppermost leaves removal reduced N remobilization from stem and photosynthesis for poor N uptake, resulting in 37.5 and 50.2% significantly reduced N accumulation in kernels, respectively. PMID:28084467

  9. Optimum Leaf Removal Increases Nitrogen Accumulation in Kernels of Maize Grown at High Density.

    PubMed

    Liu, Tiening; Huang, Rundong; Cai, Tie; Han, Qingfang; Dong, Shuting

    2017-01-13

    Increasing plant density is one of the main approaches of achieving higher yields for modern maize crop. However, there exists leaf redundancy for high-density maize, and leaves of the upper canopy shade more competent leaves at the middle strata. In a two-year field experiments, Jinhai5, a semi-compact corn cultivar, was grown at a density of 105,000 plants ha(-1) grown until 3 days after silking (3DAS), when plants were subjected to removal of the uppermost two leaves (S2), four leaves (S4) or six leaves (S6), with no leaf removal as control (S0). We evaluated the effects of leaf removal on N remobilization, photosynthetic capacity of the remaining leaves for N uptake, and N accumulation in kernels. Our present results concluded that, under high plant density, excising the uppermost two leaves promoted N remobilization from vegetative organs to kernels and enhanced photosynthetic capacity for N uptake, leading to an increased N accumulation in kernels (19.6% higher than control). However, four or six uppermost leaves removal reduced N remobilization from stem and photosynthesis for poor N uptake, resulting in 37.5 and 50.2% significantly reduced N accumulation in kernels, respectively.

  10. Development and Characterization of Diamond Film and Compound Metal Surface High Current Photocathodes

    NASA Astrophysics Data System (ADS)

    Shurter, R. P.; Moir, D. C.; Shurter, R. P.; Moir, D. C.

    1997-05-01

    High current photocathodes operating in vacuum environments as high as 10-5 torr are being developed at Los Alamos for use in a new generation of linear induction accelerators. We report high quantum efficiencies and high current densities in wide bandgap semiconductor and compound metal surface thermally augmented photocathode materials illuminated by ultraviolet laser radiation.

  11. Optimising yield and resource utilisation of summer maize under the conditions of increasing density and reducing nitrogen fertilization.

    PubMed

    Wei, Shanshan; Wang, Xiangyu; Zhu, Qicen; Jiang, Dong; Dong, Shuting

    2017-10-05

    The inefficient use of resources always poses risks of maize (Zea mays L.) yield reduction in China. We performed this research to monitor the effects of increasing plant density and reducing nitrogen (N) rate on radiation-use efficiency (RUE), N efficiency traits, grain yield (GY) and their inter-relationships. Besides, whether GY and resource-use efficiency can both be maximized was examined. Hence, a 2-year field experiment was conducted using a widely grown variety "Denghai 618" in Shandong, China. Treatments contained two different plant densities [67,500 (D1) and 97,500 (D2) plant ha(-1)] and three N levels [0 (N-2), 180 (N-1), 360 (Nck) kg ha(-1)], set D1Nck as control. Significant increases in grain yield, biomass, RUE, above-ground N uptake (AGN) and N efficiency were observed when density increased from D1 to D2. Declining N application was accompanied by reductions in yield, RUE and AGN especially under high density, yet an obvious improvement in N recovery efficiency (NRE), agronomic N efficiency and N partial factor productivity. The increased GY was positive related with population biomass (r = 0.895**), RUE (r = 0.769**) and AGN (r = 0.923**), whereas it has no significant correlation with N efficiency. In this study, D2Nck obtained 18.8, 17.9, 24.8 and 29.7% higher grain yield, RUE, AGN and NRE respectively, compared to control, optimizing both yield and the efficiencies of radiation and N use. Furthermore, higher yield and RUE with more desirable N efficiency may be possible via optimizing density and N rate combination.

  12. Energetics and optical properties of nitrogen impurities in SrTi O3 from hybrid density-functional calculations

    NASA Astrophysics Data System (ADS)

    Reunchan, Pakpoom; Umezawa, Naoto; Janotti, Anderson; T-Thienprasert, Jiraroj; Limpijumnong, Sukit

    2017-05-01

    Semiconductor photocatalysts that can produce hydrogen from water splitting are of great interest. Among the various possibilities, nitrogen (N)-doped SrTi O3 is a promising candidate for hydrogen evolution under visible-light irradiation. In this study, hybrid density-functional calculations are employed to investigate the stability and impact of nitrogen impurities on the electronic and optical properties in SrTi O3 . We find that the substitutional N on O site (NO) is a deep acceptor in SrTi O3 . Moreover, NO predominates over other N-related defects under equilibrium growth conditions in n -type SrTi O3 . Our results reveal that NO gives rise to visible-light absorption in agreement with experimental observations. In addition, we find that hydrogen can bind to NO, forming NO-Hi complex which leads to a blueshift in the optical absorption. Other N configurations can also contribute to optical absorption in the visible range. The vibration frequencies of different N configurations are provided to support identification using vibrational spectroscopy techniques.

  13. Nitrogen-doped carbon spheres: A new high-energy-density and long-life pseudo-capacitive electrode material for electrochemical flow capacitor.

    PubMed

    Hou, Shujin; Wang, Miao; Xu, Xingtao; Li, Yandong; Li, Yanjiang; Lu, Ting; Pan, Likun

    2017-04-01

    One of the most challenging issues in developing electrochemical flow capacitor (EFC) technology is the design and synthesis of active electrode materials with high energy density and long cycle life. However, in practical cases, the energy density and cycle ability obtained currently cannot meet the practical need. In this work, we propose a new active material, nitrogen-doped carbon spheres (NCSs), as flowable electrodes for EFC application. The NCSs were prepared via one-pot hydrothermal synthesis in the presence of resorcinol/formaldehyde as carbon precursors and melamine as nitrogen precursor, followed by carbonization in nitrogen flow at various temperatures. The results of EFC experiments demonstrate that NCSs obtained at 800°C exhibit a high energy density of 13.5Whkg(-1) and an excellent cycle ability, indicating the superiority of NCSs for EFC application.

  14. High current high accuracy IGBT pulse generator

    SciTech Connect

    Nesterov, V.V.; Donaldson, A.R.

    1995-05-01

    A solid state pulse generator capable of delivering high current triangular or trapezoidal pulses into an inductive load has been developed at SLAC. Energy stored in a capacitor bank of the pulse generator is switched to the load through a pair of insulated gate bipolar transistors (IGBT). The circuit can then recover the remaining energy and transfer it back to the capacitor bank without reversing the capacitor voltage. A third IGBT device is employed to control the initial charge to the capacitor bank, a command charging technique, and to compensate for pulse to pulse power losses. The rack mounted pulse generator contains a 525 {mu}F capacitor bank. It can deliver 500 A at 900V into inductive loads up to 3 mH. The current amplitude and discharge time are controlled to 0.02% accuracy by a precision controller through the SLAC central computer system. This pulse generator drives a series pair of extraction dipoles.

  15. High-current, high-frequency capacitors

    NASA Astrophysics Data System (ADS)

    Renz, D. D.

    1983-06-01

    The NASA Lewis high-current, high-frequency capacitor development program was conducted under a contract with Maxwell Laboratories, Inc., San Diego, California. The program was started to develop power components for space power systems. One of the components lacking was a high-power, high-frequency capacitor. Some of the technology developed in this program may be directly usable in an all-electric airplane. The materials used in the capacitor included the following: the film is polypropylene, the impregnant is monoisopropyl biphenyl, the conductive epoxy is Emerson and Cuming Stycast 2850 KT, the foil is aluminum, the case is stainless steel (304), and the electrode is a modified copper-ceramic.

  16. High-current, high-frequency capacitors

    NASA Technical Reports Server (NTRS)

    Renz, D. D.

    1983-01-01

    The NASA Lewis high-current, high-frequency capacitor development program was conducted under a contract with Maxwell Laboratories, Inc., San Diego, California. The program was started to develop power components for space power systems. One of the components lacking was a high-power, high-frequency capacitor. Some of the technology developed in this program may be directly usable in an all-electric airplane. The materials used in the capacitor included the following: the film is polypropylene, the impregnant is monoisopropyl biphenyl, the conductive epoxy is Emerson and Cuming Stycast 2850 KT, the foil is aluminum, the case is stainless steel (304), and the electrode is a modified copper-ceramic.

  17. Dancing with Energetic Nitrogen Atoms: Versatile N-Functionalization Strategies for N-Heterocyclic Frameworks in High Energy Density Materials.

    PubMed

    Yin, Ping; Zhang, Qinghua; Shreeve, Jean'ne M

    2016-01-19

    Nitrogen-rich heterocycles represent a unique class of energetic frameworks featuring high heats of formation and high nitrogen content, which have generated considerable research interest in the field of high energy density materials (HEDMs). Although traditional C-functionalization methodology of aromatic hydrocarbons has been fully established, studies on N-functionalization strategies of nitrogen-containing heterocycles still have great potential to be exploited by virtue of forming diverse N-X bonds (X = C, N, O, B, halogen, etc.), which are capable of regulating energy performance and the stability of the resulting energetic compounds. In this sense, versatile N-functionalization of N-heterocyclic frameworks offers a flexible strategy to meet the requirements of developing new-generation HEDMs. In this Account, the role of strategic N-functionalization in designing new energetic frameworks, including the formation of N-C, N-N, N-O, N-B and N-halogen bonds, is emphasized. In the family of N-functionalized HEDMs, energetic derivatives, by virtue of forming N-C bonds, are the most widely used type due to the good nucleophilic capacity of most heterocyclic backbones. Although introduction of carbon tends to decrease energetic performance, significant improvement in material sensitivity makes this strategy attractive for safety concerns. More importantly, most "explosophores" can be readily introduced into the N-C linkage, thus providing a promising route to various HEDMs. Formation of additional N-N bonds typically gives rise to higher heats of formation, implying the potential enhancement in detonation performance. In many cases, the increased hydrogen bonding interactions within N-N functionalized heterocycles also improve thermal stability accordingly. Introduction of a single N,N'-azo bridge into several azole moieties leads to an extended nitrogen chain, demonstrating a new strategy for designing high-nitrogen compounds. The strategy of N-O functionalization

  18. Acousto-optic measurements of tropospheric nitrogen dioxide column density by solar spectroscopy

    NASA Astrophysics Data System (ADS)

    Cheng, A. Y. S.; Chan, M. H.

    2005-09-01

    Measurements of column densities of atmospheric gases can be achieved by a solar spectroscopic method that uses differential optical absorption spectroscopy. Because of the scintillation of sunlight intensity in the atmosphere, the variation in intensity will introduce a low-frequency modification of the measured solar spectrum. A spectral capturing-type CCD spectrometer takes milliseconds to capture a solar spectrum, and the effect of sunlight scintillation is negligible. In contrast, without scintillation correction, a scanning-type spectrometer spending minutes to obtain a complete solar spectrum will introduce some amount of errors. We demonstrate an intensity-compensation technique in a scanning-type spectrometer, based on a solid-state acousto-optic tunable filter, for solar spectroscopic measurements.

  19. Acousto-optic measurements of tropospheric nitrogen dioxide column density by solar spectroscopy.

    PubMed

    Cheng, A Y S; Chan, M H

    2005-09-10

    Measurements of column densities of atmospheric gases can be achieved by a solar spectroscopic method that uses differential optical absorption spectroscopy. Because of the scintillation of sunlight intensity in the atmosphere, the variation in intensity will introduce a low-frequency modification of the measured solar spectrum. A spectral capturing-type CCD spectrometer takes milliseconds to capture a solar spectrum, and the effect of sunlight scintillation is negligible. In contrast, without scintillation correction, a scanning-type spectrometer spending minutes to obtain a complete solar spectrum will introduce some amount of errors. We demonstrate an intensity-compensation technique in a scanning-type spectrometer, based on a solid-state acousto-optic tunable filter, for solar spectroscopic measurements.

  20. Correlation of white female breast cancer incidence trends with nitrogen dioxide emission levels and motor vehicle density patterns.

    PubMed

    Chen, Fan; Bina, William F

    2012-02-01

    The long-term trend of female breast cancer incidence rates in the United States and some European countries demonstrates a similar pattern: an increasing trend in the last century followed by a declining trend in this century. The well-known risk factors cannot explain this trend. We compared the breast cancer incidence trends obtained from SEER data with the trend of nitrogen dioxides (NOx) emission and monitoring data as well as motor vehicle density data. The upward followed by downward trend of NOx is similar to the breast cancer incidence trend but with an offset of 20 years earlier. Motor vehicles are the major source of NOx emissions. The geographic distribution of motor vehicles density in 1970 in the observed US counties is positively correlated with breast cancer incidence rates (R(2) 0.8418, the correlation coefficient = 0.9175) in 1980-1995. Because both the time trend and geographic pattern are associated with breast cancer incidence rates, further studies on the relationship between breast cancer and air pollution are needed.

  1. High-current electron gun with a planar magnetron integrated with an explosive-emission cathode

    NASA Astrophysics Data System (ADS)

    Kiziridi, P. P.; Ozur, G. E.

    2017-05-01

    A new high-current electron gun with plasma anode and explosive-emission cathode integrated with planar pulsed powered magnetron is described. Five hundred twelve copper wires 1 mm in diameter and 15 mm in height serve as emitters. These emitters are installed on stainless steel disc (substrate) with 3-mm distance between them. Magnetron discharge plasma provides increased ion density on the periphery of plasma anode formed by high-current Penning discharge ignited within several milliseconds after starting of the magnetron discharge. The increased on the periphery ion density improves the uniformity of high-current electron beam produced in such an electron gun.

  2. High-current carbon-epoxy capillary cathode

    NASA Astrophysics Data System (ADS)

    Gleizer, J. Z.; Queller, T.; Bliokh, Yu.; Yatom, S.; Vekselman, V.; Krasik, Ya. E.; Bernshtam, V.

    2012-07-01

    The results of experiments on the reproducible generation of an electron beam having a high current density of up to 300 A/cm2 and a satisfactorily uniform cross-sectional distribution of current density in a ˜200 kV, ˜450 ns vacuum diode with a carbon-epoxy capillary cathode are presented. It was found that the source of the electrons is the plasma formed as a result of flashover inside the capillaries. It is shown that the plasma formation occurs at an electric field ≤15 kV/cm and that the cathode sustains thousands of pulses without degradation in its emission properties. Time- and space-resolved visible light observation and spectroscopy analyses were used to determine the cathode plasma's density, temperature, and expansion velocity. It was found that the density of the cathode plasma decreases rapidly in relation to the distance from the cathode. In addition, it was found that the main reason for the short-circuiting of the accelerating gap is the formation and expansion of the anode plasma. Finally, it was shown that when an external guiding magnetic field is present, the injection of the electron beam into the drift space with a current amplitude exceeding its critical value changes the radial distribution of the current density of the electron beam because the inner electrons are reflected from the virtual cathode.

  3. Comparative planetary nitrogen atmospheres: Density and thermal structures of Pluto and Triton

    NASA Astrophysics Data System (ADS)

    Strobel, Darrell F.; Zhu, Xun

    2017-07-01

    Both atmospheres of Pluto and Neptune's largest satellite Triton have cold surfaces with surface gravitational accelerations and atmospheric surface pressures of comparable magnitude. To study their atmospheres we have updated Zhu et al. (2014) model for Pluto's atmosphere by adopting Voigt line profiles in the radiation module with the latest spectral database and extended the model to Triton's atmosphere by including additional parameterized heating due to the magnetospheric electron transport and energy deposition. The CH4 mixing ratio profiles play central roles in differentiating the atmospheres of Pluto and Triton. On Pluto the surface CH4 mole fraction is in the range of 0.3-0.8%, sufficiently high to ensure that it is well mixed in the lower atmosphere and not subject to photochemical destruction. Near the exobase CH4 attains comparable density to N2 due to gravitational diffusive separation and escapes at 500 times the N2 rate (= 1 × 1023 N2 s-1). In Triton's atmosphere, the surface CH4 mole fraction is on the order of 0.015%, sufficiently low to ensure that it is photochemically destroyed irreversibly in the lower atmosphere and that N2 remains the major species, even at the exobase. With solar EUV power only, Triton's upper thermosphere is too cold and magnetospheric heating, approximately comparable to the solar EUV power, is needed to bring the N2 tangential column number density in the 500-800 km range up to values derived from the Voyager 2 UVS observations (Broadfoot et al., 1989). Due to their cold exobase temperatures relative to the gravitational potential energy wells that N2 resides in, atmospheric escape from Triton and Pluto is not dominated by N2 Jeans escape but by CH4 from Pluto and H, C, N and H2 from Triton. The atmospheric thermal structure near the exobase is sensitive to the atmospheric escape rate only when it is significantly greater than 2 × 1027 amu s-1, above which enhanced Jeans escape and larger radial velocity adiabatically

  4. Thermal Performance of Low Layer Density Multilayer Insu1ation Using Liquid Nitrogen

    NASA Technical Reports Server (NTRS)

    Johnson, Wesley L.; Fesmire, James E.

    2011-01-01

    In order to support long duration cryogenic propellant storage, the Cryogenic Fluid Management (CFM) Project of the Exploration Technology Development Program (ETDP) is investigating the long duration storage propertie$ of liquid methane on the lunar surface. The Methane Lunar Surface Thermal Control (MLSTC) testing is using a tank of the approximate dimensions of the Altair ascent tanks inside of a vacuum chamber to simulate the environment in low earth orbit and on the lunar surface. The thermal performance testing of multilayer insulation (MLI) coupons that are fabricated identically to the tank applied insulation is necessary to understand the performance of the blankets and to be able to predict the performance of the insulation prior to testing. This coupon testing was completed in Cryostat-100 at the Cryogenics Test Laboratory. The results showed the properties of the insulation as a function of layer density, number of layers, and warm boundary temperature. These results aid in the understanding of the performance parameters o fMLI and help to complete the body of literature on the topic.

  5. Computer automation of high current ion implanters

    NASA Astrophysics Data System (ADS)

    Woodard, Ollie; Lindsey, Paul; Cecil, Joseph; Pipe, Robert

    1985-01-01

    Complete computer automation of a high current ion implanter has been achieved. Special design considerations were necessary for automation including the development of a simplified ion source, a simplified beam transport control function, and a computer aided real-time feedback dosimetry control system. A special, versatile software architecture was also necessary to allow protected operation by unskilled operators, as well as diagnostic and maintenance modes accessible only to qualified personnel. Integral mounting of the DEC LSI-11 computer in the implanter frame provided additional challenges regarding EMI control and the electrical isolation required. The end result is a system in which all pertinent functions of the implanter are computer monitored and controlled continuously, allowing for automatic set-up, operation, on-line fault detection and diagnostics, with recovery software to correct many transient problems as they occur. This paper will discuss both general and specific solutions to the design problems encountered, and will review the system performance from a user point of view.

  6. Manipulating Planting Density and Nitrogen Fertilizer Application to Improve Yield and Reduce Environmental Impact in Chinese Maize Production.

    PubMed

    Xu, Cailong; Huang, Shoubing; Tian, Beijing; Ren, Jianhong; Meng, Qingfeng; Wang, Pu

    2017-01-01

    Relatively low nitrogen (N) efficiency and heavy environmental costs caused by excessive N fertilizer applications with outdated fertilization techniques are current cultivation production problems with maize among smallholders in North China Plain. Although many studies have examined agronomical strategies for improving yields and N use, the integrated effects of these measures and the associated environmental costs are not well understood. We conducted a 2-year field study with two densities (67,500 plants ha(-1), which was similar to local farmers' practices, and 90,000 plants ha(-1)) and three N rates (0, 180, and 360 kg ha(-1), the rate local farmers' commonly apply) to test the integrated effects for maize production at Wuqiao experimental station in North China Plain. The higher planting density produced significant increases in grain yield (GY), N use efficiency (NUE), agronomic N efficiency (AEN), and N partial productivity (PFPN) by 6.6, 3.9, 24.7, and 8.8%, respectively; in addition, N2O emission and greenhouse gas intensity decreased by 7.3 and 4.3%, respectively. With a lower N application rate, from 360 to 180 kg ha(-1), GY was unchanged, and NUE, AEN, and PFPN all significantly increased by 6.2, 96.0, and 98.7%, respectively; in addition, N2O emission and greenhouse gas intensity decreased by 61.5 and 46.2%, respectively. The optimized N rate (180 kg N ha(-1)) for the 90,000 plants ha(-1) treatment achieved the highest yield with only 50% of the N fertilizer input commonly employed by local farmers' (360 kg N ha(-1)), which contributed to the increased N-uptake and N-transfer capacity. Therefore, our study demonstrated that agronomical methods such as increasing planting density with reasonable N application could be useful to obtain higher GY along with efficient N management to help lower environmental costs of maize production.

  7. Picosecond-TALIF and VUV absorption measurements of absolute atomic nitrogen densities from an RF atmospheric pressure plasma jet with He/O2/N2 gas mixtures

    NASA Astrophysics Data System (ADS)

    West, Andrew; Niemi, Kari; Schröter, Sandra; Bredin, Jerome; Gans, Timo; Wagenaars, Erik

    2015-09-01

    Reactive Oxygen and Nitrogen species (RONS) from RF atmospheric pressure plasma jets (APPJs) are important in biomedical applications as well as industrial plasma processing such as surface modification. Atomic oxygen has been well studied, whereas, despite its importance in the plasma chemistry, atomic nitrogen has been somewhat neglected due to its difficulty of measurement. We present absolute densities of atomic nitrogen in APPJs operating with He/O2/N2 gas mixtures in open air, using picosecond Two-photon Absorption Laser Induced Fluorescence (ps-TALIF) and vacuum ultra-violet (VUV) absorption spectroscopy. In order to apply the TALIF technique in complex, He/O2/N2 mixtures, we needed to directly measure the collisional quenching effects using picosecond pulse widths (32ps). Traditional calculated quenching corrections, used in nanosecond TALIF, are inadequate due to a lack of quenching data for complex mixtures. Absolute values for the densities were found by calibrating against a known density of Krypton. The VUV absorption experiments were conducted on the DESIRS synchrotron beamline using a unique VUV Fourier-transform spectrometer. Atomic nitrogen densities were on the order of 1020 m-3 with good agreement between TALIF and VUV absorption. UK EPSRC grant EP/K018388/1.

  8. Achromatic beam transport of High Current Injector

    NASA Astrophysics Data System (ADS)

    Kumar, Sarvesh; Mandal, A.

    2016-02-01

    The high current injector (HCI) provides intense ion beams of high charge state using a high temperature superconducting ECR ion source. The ion beam is accelerated upto a final energy of 1.8 MeV/u due to an electrostatic potential, a radio frequency quadrupole (RFQ) and a drift tube linac (DTL). The ion beam has to be transported to superconducting LINAC which is around 50 m away from DTL. This section is termed as high energy beam transport section (HEBT) and is used to match the beam both in transverse and longitudinal phase space to the entrance of LINAC. The HEBT section is made up of four 90 deg. achromatic bends and interconnecting magnetic quadrupole triplets. Two RF bunchers have been used for longitudinal phase matching to the LINAC. The ion optical design of HEBT section has been simulated using different beam dynamics codes like TRACEWIN, GICOSY and TRACE 3D. The field computation code OPERA 3D has been utilized for hardware design of all the magnets. All the dipole and quadrupole magnets have been field mapped and their test results such as edge angles measurements, homogeneity and harmonic analysis etc. are reported. The whole design of HEBT section has been performed such that the most of the beam optical components share same hardware design and there is ample space for beam diagnostics as per geometry of the building. Many combination of achromatic bends have been simulated to transport the beam in HEBT section but finally the four 90 deg. achromatic bend configuration is found to be the best satisfying all the geometrical constraints with simplified beam tuning process in real time.

  9. The effects of nitrogen starter fertilizer and plant density on yield, yield components and oil and protein content of soybean (Glycine max L. Merr).

    PubMed

    Boroomandan, P; Khoramivafa, M; Haghi, Y; Ebrahimi, A

    2009-02-15

    Effects of nitrogen starter fertilizer and plant density on yield and oil and protein content of soybean (Glycine max L. Merr) are not well understood, because nitrogen starter fertilizer and plant density has been tested separately. Two years field experiment was conducted to evaluate effects of these factors on yield, yield components, oil and protein content in 2006 and 2007 in Kermanshah, Iran. The experiment was conducted on soybean (var. Williams) as a split-plot based on randomized complete blocks design with three replications. Nitrogen starter fertilizer treatments were arranged in three rates (0, 40, 80 kg ha(-1)) as main plots and plant density as sub plots arranged with three levels (15, 30, 45 plant m(-2)). Based on similarity treatments and experimental designs, the results of analysis of combined variance and mean comparisons showed significant (528.4 kg ha(-1) yield increase as density increased from 30 to 45 plant m(-2) and nitrogen starter fertilizer increased from 0 to 40 kg ha(-1) in two years. Analysis of correlation showed a positive significant correlation between yield and number of seed per plant (r = 0.724), number of pods and yield (r = 0.463), thousand seed weight and yield (r = 0.437). A linear regression was found between yield and number of seed per plant, number of pods and thousand seed weight (yield = 37.58 + 0.73x1-0.14x2 + 0.7x3; r2 = 0.56); p < 0.01). Seed protein was unaffected by plant densities, but nitrogen application changed it. Dissimilarly, oil content has a diverse respond to treatments. This experiment showed density of 45 plant m(-2) and application of nitrogen starter fertilizer 40 kg ha(-1) are optimum and increase grain yield under condition of our experiment. We suggest to conduct some experiments for understanding of linear relationship for number of pod for understanding of linear relationship for number of pod for levels of nitrogen starter and quadratic relationship for number of seed for levels of density.

  10. High-Current Betatron, Phase I.

    DTIC Science & Technology

    1982-04-16

    Errors in the vertical (Betatron) magnetic field result in tb’ driven resonances that must be crossed during acceleration. The amplitude growth of...case, the self field depends here only on the line density, which does not change as the instability develops. It is thus necessary to cross this...Experimental arrangements of equipment ....... 1-6 3 Magnetic field (top trace) and electrostatic oscillation (middle). Sweep: 50 Vis/div. The bottom

  11. High-current plasmas switching devices

    NASA Astrophysics Data System (ADS)

    Mustafaev, Aleksandr; Grabovskiy, Artiom; Murillo, Oscar; Soukhomlinov, Vladimir

    2016-10-01

    Nowadays, the level of development of spatial and earthly nuclear energetic lays down big requirements: total control possibility of current density with a stable work of the instrument in extreme conditions with a big radiation level and temperatures of 1000 K. Among the ways of solving this problem the application of key elements with binary cesium-barium plasmas are available. The results of the investigation on electro-kinetic parameters of plasma Knudsen Cs-Ba key element with big current densities are presented in this work: >The phenomenon of spontaneous current breakage, which has a big influence on the efficiency of the grid extinction, was investigated; >Unique regimes of effective grid extinction, in which the rise of modulated power is realized with a declining of the energetic cost of controlling the current of the key element, were found; >Record energetic parameters for the binary key element were obtained: at an anode potential of 50 V, stable frequencies modulation at 1-10 kHz, the electric power density of 5 kW/cm2 and the efficiency more than 95%.

  12. Characterization of a high current pulsed arc using optical emission spectroscopy

    NASA Astrophysics Data System (ADS)

    Sousa Martins, R.; Zaepffel, C.; Chemartin, L.; Lalande, Ph; Soufiani, A.

    2016-10-01

    In this paper, we present the investigation realized on an experimental setup that simulates an arc column subjected to the transient phase of a lightning current waveform in laboratory conditions. Optical emission spectroscopy is employed to assess space- and time-resolved properties of this high current pulsed arc. Different current peak levels are utilised in this work, ranging from 10 kA to 100 kA, with a peak time around 15 µs. Ionic lines of nitrogen and oxygen are used to determine the radial profiles of temperature and electron density of the arc channel over time from 2 µs to 36 µs. A combination of 192 N II and O II lines is considered in the calculation of the bound-bound contribution of the absorption coefficient of the plasma channel. Calculations of the optical thickness showed that self-absorption of these ionic lines in the arc column is important. To obtain temperature and electron density profiles in the arc, we solved the radiative transfer equation across the channel under an axisymmetric assumption and considering the channel formed by uniform concentric layers. For the 100 kA current peak level, the temperature reaches more than 38 000 K and the electron density reaches 5  ×  1018 cm-3. The pressure inside the channel is calculated using the air plasma composition at local thermodynamic equilibrium, and reaches 45 bar. The results are discussed and utilised to estimate the electrical conductivity of the arc channel.

  13. Modeling ion-induced electrons in the High Current Experiment

    SciTech Connect

    Stoltz, P.H.; Verboncoeur, J.P.; Cohen, R.H.; Molvik, A.W.; Vay, J.-L.; Veitzer, S.A.

    2006-05-15

    A primary concern for high current ion accelerators is contaminant electrons. These electrons can interfere with the beam ions, causing emittance growth and beam loss. Numerical simulation is a main tool for understanding the interaction of the ion beam with the contaminant electrons, but these simulations then require accurate models of electron generation. These models include ion-induced electron emission from ions hitting the beam pipe walls or diagnostics. However, major codes for modeling ion beam transport are written in different programming languages and used on different computing platforms. For electron generation models to be maximally useful, researchers should be able to use them easily from many languages and platforms. A model of ion-induced electrons including the electron energy distribution is presented here, including a discussion of how to use the Babel software tool to make these models available in multiple languages and how to use the GNU Autotools to make them available on multiple platforms. An application to simulation of the end region of the High Current Experiment is shown. These simulations show formation of a virtual cathode with a potential energy well of amplitude 12.0 eV, approximately six times the most probable energy of the ion-induced electrons. Oscillations of the virtual cathode could lead to possible longitudinal and transverse modulation of the density of the electrons moving out of the virtual cathode.

  14. Modeling ion-induced electrons in the High Current Experimenta)

    NASA Astrophysics Data System (ADS)

    Stoltz, P. H.; Verboncoeur, J. P.; Cohen, R. H.; Molvik, A. W.; Vay, J.-L.; Veitzer, S. A.

    2006-05-01

    A primary concern for high current ion accelerators is contaminant electrons. These electrons can interfere with the beam ions, causing emittance growth and beam loss. Numerical simulation is a main tool for understanding the interaction of the ion beam with the contaminant electrons, but these simulations then require accurate models of electron generation. These models include ion-induced electron emission from ions hitting the beam pipe walls or diagnostics. However, major codes for modeling ion beam transport are written in different programming languages and used on different computing platforms. For electron generation models to be maximally useful, researchers should be able to use them easily from many languages and platforms. A model of ion-induced electrons including the electron energy distribution is presented here, including a discussion of how to use the Babel software tool to make these models available in multiple languages and how to use the GNU Autotools to make them available on multiple platforms. An application to simulation of the end region of the High Current Experiment is shown. These simulations show formation of a virtual cathode with a potential energy well of amplitude 12.0eV, approximately six times the most probable energy of the ion-induced electrons. Oscillations of the virtual cathode could lead to possible longitudinal and transverse modulation of the density of the electrons moving out of the virtual cathode.

  15. Tropospheric Nitrogen Dioxide Column Density Trends Seen from the 10-year Record of OMI Measurements over East Asia

    NASA Astrophysics Data System (ADS)

    Irie, H.; Muto, T.; Itahashi, S.; Kurokawa, J. I.

    2015-12-01

    The Ozone Monitoring Instrument (OMI) aboard the Aura satellite recorded the 10-year (2005-2014) of tropospheric nitrogen dioxide (NO2) vertical column density (VCD) data. The data set taken over East Asia was analyzed to estimate linear trends on national and grid bases for two periods of 2005-2011 and 2011-2014. The most striking features are leveling-off or decreasing trends seen in NO2 VCDs over China for 2011-2014 after continuous increases for 2005-2011. In particular, a significant reduction by ~14% occurred from 2013 through 2014, attaining to the level of 2009. The grid-basis trend analysis implies that the turnaround seen in the trends occurred on a province or larger spatial scale and was likely due mainly to the technical improvement such as the widespread use of de-NOx units. Another prominent features are seen in Japan, where NO2 VCDs decreased at a rate of ~4% per year from 2005 to 2011. The rate was almost unchanged between the two periods 2005-2011 and 2011-2014, while the significant power substitution of thermal power generation for the nuclear power generation took place in Japan after 2011, when a massive earthquake occurred off the Pacific coast of northern Japan. This reflects a less contribution of NOx emissions from the power plant sector than that from the transport sector in the Pacific Belt Zone lying over metropolitan areas.

  16. Local density of electromagnetic states in plasmonic nanotapers: spatial resolution limits with nitrogen-vacancy centers in diamond nanospheres.

    PubMed

    Salas-Montiel, Rafael; Berthel, Martin; Beltrán-Madrigal, Josslyn; Huant, Serge; Drezet, Aurélien; Blaize, Sylvain

    2017-03-21

    One of the most explored single quantum emitters for the development of nanoscale fluorescence lifetime imaging is the nitrogen-vacancy (NV) color center in diamond. Indeed, a NV center does not experience fluorescence bleaching and blinking at room temperature. Furthermore, its optical properties are preserved when embedded into nanodiamond hosts. This letter focuses on the modeling of the local density of states (LDOS) in a plasmonic nanofocusing structure with NV center acting as local illumination sources. Numerical calculations of the LDOS near such nanostructure were done with a classical electric dipole radiation placed inside a diamond sphere as well as near-field optical fluorescence lifetime imaging of the structure. We found that Purcell factors higher than 10 can be reached with diamond nanospheres of radius less than 5 nm and at a distance of less than 20 nm from the surface of the structure. Although the spatial resolution of the experiment is limited by the size of the nanodiamond, our work supports the analysis and interpretation of single NV color center in nanodiamond as a probe for scanning near-field optical microscopy.

  17. Local density of electromagnetic states in plasmonic nanotapers: spatial resolution limits with nitrogen-vacancy centers in diamond nanospheres

    NASA Astrophysics Data System (ADS)

    Salas-Montiel, Rafael; Berthel, Martin; Beltran-Madrigal, Josslyn; Huant, Serge; Drezet, Aurélien; Blaize, Sylvain

    2017-05-01

    One of the most explored single quantum emitters for the development of nanoscale fluorescence lifetime imaging is the nitrogen-vacancy (NV) color center in diamond. An NV center does not experience fluorescence bleaching or blinking at room temperature. Furthermore, its optical properties are preserved when embedded into nanodiamond hosts. This paper focuses on the modeling of the local density of states (LDOS) in a plasmonic nanofocusing structure with an NV center acting as local illumination sources. Numerical calculations of the LDOS near such a nanostructure were done with a classical electric dipole radiation placed inside a diamond sphere as well as near-field optical fluorescence lifetime imaging of the structure. We found that Purcell factors higher than ten can be reached with diamond nanospheres of radius less than 5 nm and at a distance of less than 20 nm from the surface of the structure. Although the spatial resolution of the experiment is limited by the size of the nanodiamond, our work supports the analysis and interpretation of a single NV color center in a nanodiamond as a probe for scanning near-field optical microscopy.

  18. Nested Markov chain Monte Carlo sampling of a density functional theory potential: equilibrium thermodynamics of dense fluid nitrogen.

    PubMed

    Coe, Joshua D; Sewell, Thomas D; Shaw, M Sam

    2009-08-21

    An optimized variant of the nested Markov chain Monte Carlo [n(MC)(2)] method [J. Chem. Phys. 130, 164104 (2009)] is applied to fluid N(2). In this implementation of n(MC)(2), isothermal-isobaric (NPT) ensemble sampling on the basis of a pair potential (the "reference" system) is used to enhance the efficiency of sampling based on Perdew-Burke-Ernzerhof density functional theory with a 6-31G(*) basis set (PBE6-31G(*), the "full" system). A long sequence of Monte Carlo steps taken in the reference system is converted into a trial step taken in the full system; for a good choice of reference potential, these trial steps have a high probability of acceptance. Using decorrelated samples drawn from the reference distribution, the pressure and temperature of the full system are varied such that its distribution overlaps maximally with that of the reference system. Optimized pressures and temperatures then serve as input parameters for n(MC)(2) sampling of dense fluid N(2) over a wide range of thermodynamic conditions. The simulation results are combined to construct the Hugoniot of nitrogen fluid, yielding predictions in excellent agreement with experiment.

  19. A nitrogen doped low-dislocation density free-standing single crystal diamond plate fabricated by a lift-off process

    SciTech Connect

    Mokuno, Yoshiaki Kato, Yukako; Tsubouchi, Nobuteru; Chayahara, Akiyoshi; Yamada, Hideaki; Shikata, Shinichi

    2014-06-23

    A nitrogen-doped single crystal diamond plate with a low dislocation density is fabricated by chemical vapor deposition (CVD) from a high pressure high temperature synthetic type IIa seed substrate by ion implantation and lift-off processes. To avoid sub-surface damage, the seed surface was subjected to deep ion beam etching. In addition, we introduced a nitrogen flow during the CVD step to grow low-strain diamond at a relatively high growth rate. This resulted in a plate with low birefringence and a dislocation density as low as 400 cm{sup −2}, which is the lowest reported value for a lift-off plate. Reproducing this lift-off process may allow mass-production of single crystal CVD diamond plates with low dislocation density and consistent quality.

  20. Method for making a high current fiber brush collector

    NASA Astrophysics Data System (ADS)

    Scuro, S. J.

    1986-05-01

    An axial-type homopolar motor having high density, high current fiber brush collectors affording efficient, low contact resistance and low operating temperatures is discussed. The collectors include a ring of concentric row of brushes in equally spaced beveled holes soldered in place using a fixture for heating the ring to just below the solder melting point at a soldering iron for the local application of additional heat at each brush. Prior to soldering, an oxide film is formed on the surfaces of the brushes and ring, and the bevels are burnished to form a wetting surface. Flux applied with the solder at each bevel removes to an effective soldering depth the oxide film on the brushes and the holes.

  1. Drift distance survey in DPIS for high current beam production

    SciTech Connect

    Kanesue,T.; Okamura, M.; Kondo, K.; Tamura, J.; Kashiwagi, H.; Zhang, Z.

    2009-09-20

    In a laser ion source, plasma drift distance is one of the most important design parameters. Ion current density and beam pulse width are defined by plasma drift distance between laser target and beam extraction position. In direct plasma injection scheme (DPIS), which uses a laser ion source and Radio Frequency Quadrupole (RFQ) linac, we can apply relatively higher electric field at the beam extraction due to the unique shape of a positively biased electrode. However, when we aim at very high current acceleration like several tens of mA, we observed mismatched beam extraction conditions. We tested three different ion current at ion extraction region by changing plasma drift distance to study better extraction condition. In this experiment, C{sup 6+} beam was accelerated. We confirmed that the matching condition can be improved by controlling plasma drift distance.

  2. Design of a proof of principle high current transport experiment

    SciTech Connect

    Lund, S.M.; Bangerter, R.O.; Barnard, J.J.; Celata, C.M.; Faltens, A.; Friedman, A.; Kwan, J.W.; Lee, E.P.; Seidl, P.A.

    2000-01-15

    Preliminary designs of an intense heavy-ion beam transport experiment to test issues for Heavy Ion Fusion (HIF) are presented. This transport channel will represent a single high current density beam at full driver scale and will evaluate practical issues such as aperture filling factors, electrons, halo, imperfect vacuum, etc., that cannot be fully tested using scaled experiments. Various machine configurations are evaluated in the context of the range of physics and technology issues that can be explored in a manner relevant to a full scale driver. it is anticipated that results from this experiment will allow confident construction of next generation ''Integrated Research Experiments'' leading to a full scale driver for energy production.

  3. Energetic ion production in high current hollow cathodes

    NASA Astrophysics Data System (ADS)

    Foster, John; Kovach, Yao; Arthur, Neil; Viges, Eric; Davis, Chris

    2015-09-01

    High power Hall and gridded ion thrusters are being considered as a propulsion option supporting human operations (cargo or tug) to Mars. These engines utilize hollow cathodes for plasma production and beam neutralization. It has now been well documented that these cathodes produce energetic ions when operated at high current densities. Such ions are observed with peak energies approaching 100 eV. Because these ions can drive erosion of the cathode assembly, they represent a credible failure mode. An understanding of energetic ion production and approaches to mitigation is therefore desired. Presented here are data documenting the presence of energetic ions for both a barium oxide and a lanthanum hexaboride cathode as measured using a retarding potential analyzer. Also presented are energetic ion mitigation approaches, which are designed to eliminate the ion energy transfer mechanism. NASA SBIR Contract NNX15CP62P.

  4. Space charge templates for high-current beam modeling

    SciTech Connect

    Vorobiev, Leonid G.; /Fermilab

    2008-07-01

    A computational method to evaluate space charge potential and gradients of charged particle beam in the presence of conducting boundaries, has been introduced. The three-dimensional (3D) field of the beam can be derived as a convolution of macro Green's functions (template fields), satisfying the same boundary conditions, as the original beam. Numerical experiments gave a confidence that space charge effects can be modeled by templates with enough accuracy and generality within dramatically faster computational times than standard combination: a grid density + Poisson solvers, realized in the most of Particle in Cell codes. The achieved rapidity may significantly broaden the high-current beam design space, making the optimization in automatic mode possible, which so far was only feasible for simplest self-field formulations such as rms envelope equations. The template technique may be used as a standalone program, or as an optional field solver in existing beam dynamics codes both in one-passage structures and in rings.

  5. High current LiSOCl2 batteries

    NASA Astrophysics Data System (ADS)

    Debiccari, Daniel J.

    The paper describes cell construction, performance, and safety aspects of two high-rate active Li/SOCl2 batteries designed to operate at current densities as high as 26 mA/sq cm in pulse modes of 20 millisec to several minutes. Both cell designs employ a flat-plate arrangement of electrodes, a cyanoacrylate-coated anode, a bonded carbon/copper cathode, and a 1.6 M electrolyte. The major differences of the two designs are the size of the cell and the method of anode attachment. The two batteries were shown to provide over 10 times the mission life of the Ni-Cd batteries; thus, they will eliminate the logistic problems associated with the recharge requirements of the latter. In addition, a replacement of the Ni-Cd battery types with lighter Li-thionyl chloride batteries will significantly reduce battery weight and increase its capacity.

  6. A high-current pulsed cathodic vacuum arc plasma source

    NASA Astrophysics Data System (ADS)

    Oates, T. W. H.; Pigott, J.; Mckenzie, D. R.; Bilek, M. M. M.

    2003-11-01

    Cathodic vacuum arcs (CVAs) are well established as a method for producing metal plasmas for thin film deposition and as a source of metal ions. Fundamental differences exist between direct current (dc) and pulsed CVAs. We present here results of our investigations into the design and construction of a high-current center-triggered pulsed CVA. Power supply design based on electrolytic capacitors is discussed and optimized based on obtaining the most effective utilization of the cathode material. Anode configuration is also discussed with respect to the optimization of the electron collection capability. Type I and II cathode spots are observed and discussed with respect to cathode surface contamination. An unfiltered deposition rate of 1.7 nm per pulse, at a distance of 100 mm from the source, has been demonstrated. Instantaneous plasma densities in excess of 1×1019 m-3 are observed after magnetic filtering. Time averaged densities an order of magnitude greater than common dc arc densities have been demonstrated, limited by pulse repetition rate and filter efficiency.

  7. Metal-Organic Coordination Polymer to Prepare Density Controllable and High Nitrogen-Doped Content Carbon/Graphene for High Performance Supercapacitors.

    PubMed

    Luo, Jinwei; Zhong, Wenbin; Zou, Yubo; Xiong, Changlun; Yang, Wantai

    2017-01-11

    Design and preparation of carbon-based electrode material with high nitrogen-doping ratio and appropriate density attract much interest for supercapacitors in practical application. Herein, three porous carbon/graphene (NCGCu, NCGFe, and NCGZn) with high doping ratio of nitrogen have been prepared via directly pyrolysis of graphene oxide (GO)/metal-organic coordination polymer (MOCP) composites, which were formed by reacting 4,4'-bipyridine (BPD) with CuCl2, FeCl3, and ZnCl2, respectively. As-prepared NCGCu, NCGFe and NCGZn showed high nitrogen doping ratio of 10.68, 12.99, and 11.21 at. %; and high density of 1.52, 0.84, and 1.15 g cm(-3), respectively. When as-prepared samples were used as supercapacitor electrodes, NCGCu, NCGFe and NCGZn exhibited high gravimetric specific capacitances of 369, 298.5, 309.5 F g(-1), corresponding to high volumetric specific capacitances of 560.9, 250.7, 355.9 F cm(-3) at a current density of 0.5 A g(-1), as well as good cycling stability, nearly 100% of the capacitance retained after 1000 cycles even at a large current density of 10 A g(-1). It is expected that the provided novel strategy can be used to develop electrode materials in high performance energy conversion/storage devices.

  8. Fermentation with Aspergillus awamori enhanced contents of amino nitrogen and total phenolics as well as the low-density lipoprotein oxidation inhibitory activity of black soybeans.

    PubMed

    Chen, Yu-Fei; Lee, Shiow-Ling; Chou, Cheng-Chun

    2011-04-27

    A solid fermentation was performed on black soybeans with Aspergillus awamori. The effects of fermentation on the contents of total phenolics and amino nitrogen and on the inhibitory effect on low-density lipoprotein (LDL) oxidation of black soybeans were examined. Results revealed that fermentation significantly enhanced the LDL oxidation inhibitory activity and total phenolics and amino nitrogen contents of black soybeans. The increased content of amino nitrogen was closely related to the enhanced LDL oxidation inhibitory activity of fermented black soybeans and its water extract. Fermentation temperature and length affected the LDL oxidation inhibitory effect exerted by the prepared fermented black soybeans. The A. awamori-fermented black soybean prepared at 30 °C for 3 days exhibited the highest inhibitory effect on LDL oxidation. The bioactive principles related to the inhibitory effect on LDL oxidation in black soybeans, regardless of fermentation, could be most efficiently extracted with water rather than 80% methanol or 80% ethanol.

  9. Bacterial-cellulose-derived carbon nanofiber@MnO₂ and nitrogen-doped carbon nanofiber electrode materials: an asymmetric supercapacitor with high energy and power density.

    PubMed

    Chen, Li-Feng; Huang, Zhi-Hong; Liang, Hai-Wei; Guan, Qing-Fang; Yu, Shu-Hong

    2013-09-14

    A new kind of high-performance asymmetric supercapacitor is designed with pyrolyzed bacterial cellulose (p-BC)-coated MnO₂ as a positive electrode material and nitrogen-doped p-BC as a negative electrode material via an easy, efficient, large-scale, and green fabrication approach. The optimal asymmetric device possesses an excellent supercapacitive behavior with quite high energy and power density.

  10. TOPICAL REVIEW: Optical emission spectroscopy in low-temperature plasmas containing argon and nitrogen: determination of the electron temperature and density by the line-ratio method

    NASA Astrophysics Data System (ADS)

    Zhu, Xi-Ming; Pu, Yi-Kang

    2010-10-01

    This article reviews a variety of methods to obtain the electron temperature and density by the emission line ratios for low-temperature plasmas containing argon or nitrogen gas. Based on the collisional-radiative model of excited particles, the underlying principle of each of these methods is described, along with the criterion on how to select an appropriate line-ratio method according to the discharge conditions. Limitations on the application of each line-ratio technique are also discussed.

  11. New progress of high current gasdynamic ion source (invited).

    PubMed

    Skalyga, V; Izotov, I; Golubev, S; Sidorov, A; Razin, S; Vodopyanov, A; Tarvainen, O; Koivisto, H; Kalvas, T

    2016-02-01

    The experimental and theoretical research carried out at the Institute of Applied Physics resulted in development of a new type of electron cyclotron resonance ion sources (ECRISs)-the gasdynamic ECRIS. The gasdynamic ECRIS features a confinement mechanism in a magnetic trap that is different from Geller's ECRIS confinement, i.e., the quasi-gasdynamic one similar to that in fusion mirror traps. Experimental studies of gasdynamic ECRIS were performed at Simple Mirror Ion Source (SMIS) 37 facility. The plasma was created by 37.5 and 75 GHz gyrotron radiation with power up to 100 kW. High frequency microwaves allowed to create and sustain plasma with significant density (up to 8 × 10(13) cm(-3)) and to maintain the main advantages of conventional ECRIS such as high ionization degree and low ion energy. Reaching such high plasma density relies on the fact that the critical density grows with the microwave frequency squared. High microwave power provided the average electron energy on a level of 50-300 eV enough for efficient ionization even at neutral gas pressure range of 10(-4)-10(-3) mbar. Gasdynamic ECRIS has demonstrated a good performance producing high current (100-300 mA) multi-charged ion beams with moderate average charge (Z = 4-5 for argon). Gasdynamic ECRIS has appeared to be especially effective in low emittance hydrogen and deuterium beams formation. Proton beams with current up to 500 emA and RMS emittance below 0.07 π ⋅ mm ⋅ mrad have been demonstrated in recent experiments.

  12. New progress of high current gasdynamic ion source (invited)

    SciTech Connect

    Skalyga, V. Sidorov, A.; Vodopyanov, A.; Izotov, I.; Golubev, S.; Razin, S.; Tarvainen, O.; Koivisto, H.; Kalvas, T.

    2016-02-15

    The experimental and theoretical research carried out at the Institute of Applied Physics resulted in development of a new type of electron cyclotron resonance ion sources (ECRISs)—the gasdynamic ECRIS. The gasdynamic ECRIS features a confinement mechanism in a magnetic trap that is different from Geller’s ECRIS confinement, i.e., the quasi-gasdynamic one similar to that in fusion mirror traps. Experimental studies of gasdynamic ECRIS were performed at Simple Mirror Ion Source (SMIS) 37 facility. The plasma was created by 37.5 and 75 GHz gyrotron radiation with power up to 100 kW. High frequency microwaves allowed to create and sustain plasma with significant density (up to 8 × 10{sup 13} cm{sup −3}) and to maintain the main advantages of conventional ECRIS such as high ionization degree and low ion energy. Reaching such high plasma density relies on the fact that the critical density grows with the microwave frequency squared. High microwave power provided the average electron energy on a level of 50-300 eV enough for efficient ionization even at neutral gas pressure range of 10{sup −4}–10{sup −3} mbar. Gasdynamic ECRIS has demonstrated a good performance producing high current (100-300 mA) multi-charged ion beams with moderate average charge (Z = 4-5 for argon). Gasdynamic ECRIS has appeared to be especially effective in low emittance hydrogen and deuterium beams formation. Proton beams with current up to 500 emA and RMS emittance below 0.07 π ⋅ mm ⋅ mrad have been demonstrated in recent experiments.

  13. New progress of high current gasdynamic ion source (invited)

    NASA Astrophysics Data System (ADS)

    Skalyga, V.; Izotov, I.; Golubev, S.; Sidorov, A.; Razin, S.; Vodopyanov, A.; Tarvainen, O.; Koivisto, H.; Kalvas, T.

    2016-02-01

    The experimental and theoretical research carried out at the Institute of Applied Physics resulted in development of a new type of electron cyclotron resonance ion sources (ECRISs)—the gasdynamic ECRIS. The gasdynamic ECRIS features a confinement mechanism in a magnetic trap that is different from Geller's ECRIS confinement, i.e., the quasi-gasdynamic one similar to that in fusion mirror traps. Experimental studies of gasdynamic ECRIS were performed at Simple Mirror Ion Source (SMIS) 37 facility. The plasma was created by 37.5 and 75 GHz gyrotron radiation with power up to 100 kW. High frequency microwaves allowed to create and sustain plasma with significant density (up to 8 × 1013 cm-3) and to maintain the main advantages of conventional ECRIS such as high ionization degree and low ion energy. Reaching such high plasma density relies on the fact that the critical density grows with the microwave frequency squared. High microwave power provided the average electron energy on a level of 50-300 eV enough for efficient ionization even at neutral gas pressure range of 10-4-10-3 mbar. Gasdynamic ECRIS has demonstrated a good performance producing high current (100-300 mA) multi-charged ion beams with moderate average charge (Z = 4-5 for argon). Gasdynamic ECRIS has appeared to be especially effective in low emittance hydrogen and deuterium beams formation. Proton beams with current up to 500 emA and RMS emittance below 0.07 π ṡ mm ṡ mrad have been demonstrated in recent experiments.

  14. Stable superconducting magnet. [high current levels below critical temperature

    NASA Technical Reports Server (NTRS)

    Boom, R. W. (Inventor)

    1967-01-01

    Operation of a superconducting magnet is considered. A method is described for; (1) obtaining a relatively high current in a superconducting magnet positioned in a bath of a gas refrigerant; (2) operating a superconducting magnet at a relatively high current level without training; and (3) operating a superconducting magnet containing a plurality of turns of a niobium zirconium wire at a relatively high current level without training.

  15. Ionization front in a high-current gas dischargea)

    NASA Astrophysics Data System (ADS)

    Choueiri, Edgar Y.; Randolph, Thomas M.

    2007-03-01

    Spectroscopic measurements of ion/neutral density ratio profiles are made inside the high-current, low-pressure discharge of a coaxial magnetoplasmadynamic thruster and show the existence of a thin ionization front, upstream in the discharge, that effectively ionizes the incoming gas to ionization levels above 50%. The measurements allow an estimate of the width of this ionization front to be on the order of a few millimeters. Due to the known existence of microturbulence in the plasma, which can produce suprathermal electrons, an explanation of the measurements based on the existence of a suprathermal tail in the electron energy distribution function is sought. A theoretical model for the width of the ionization front is combined with a multilevel excitation model for argon and shows that a Maxwellian electron distribution function cannot account for the small length scale of the ionization front, and that the latter is more consistent with an electron distribution function having a suprathermal population, the magnitude of which is estimated by comparing the model to the experiments.

  16. Ionization front in a high-current gas discharge

    NASA Astrophysics Data System (ADS)

    Choueiri, Edgar Y.; Randolph, Thomas M.

    2007-02-01

    Spectroscopic measurements of ion/neutral density ratio profiles are made inside the high-current, low-pressure discharge of a coaxial magnetoplasmadynamic thruster and show the existence of a thin ionization front, upstream in the discharge, that effectively ionizes the incoming gas to ionization levels above 50%. The measurements allow an estimate of the width of this ionization front to be on the order of a few millimeters. Due to the known existence of microturbulence in the plasma, which can produce suprathermal electrons, an explanation of the measurements based on the existence of a suprathermal tail in the electron energy distribution function is sought. A theoretical model for the width of the ionization front is combined with a multilevel excitation model for argon and shows that a Maxwellian electron distribution function cannot account for the small length scale of the ionization front, and that the latter is more consistent with an electron distribution function having a suprathermal population, the magnitude of which is estimated by comparing the model to the experiments.

  17. X-Pinch in High-Current Diode

    NASA Astrophysics Data System (ADS)

    Bryunetkin, B. A.; Faenov, A. Ya.; Ivanenkov, G. V.; Khakhalin, S. Ya.; Mingaleev, A. R.; Pikuz, S. A.; Romanova, V. M.; Shelkovenko, T. A.; Skobelev, I. Yu.

    1994-03-01

    The review of X-pinch investigations in high current diode of BIN facility (250 kA, 100 ns) is presented. The main purposes were to investigate pinch forming processes and hot dense plasma properties. X-pinch is also considered as a source for multiple charged ions spectroscopy and for X-ray optics testing. The set of diagnostics applied in these experiments allowed us to investigate the pinch forming processes in different configurations of crossed wires loads. High spectral and space resolved measurements of plasma radiation in 1-200 Å range, absolute energy measurements and electron beam registration were provided. Plasma parameters were obtained from relative intensities and shapes of multiple charged ions spectral lines. Electron density of plasma with the temperature Te = 0.2-1 keV variated from 1023 cm-3 in hot spot to 1018 cm-3 during plasma expansion. In recombining plasma, an inversion of Al He-like ions levels population was registrated. Total radiation output of 0.5 mm pinch reached hundreds Joules in 2-100 Å range during 100 ns.

  18. Dynamics of a high-current relativistic electron beam

    SciTech Connect

    Strelkov, P. S.; Tarakanov, V. P.; Ivanov, I. E. Shumeiko, D. V.

    2015-06-15

    The dynamics of a high-current relativistic electron beam is studied experimentally and by numerical simulation. The beam is formed in a magnetically insulated diode with a transverse-blade explosive-emission cathode. It is found experimentally that the radius of a 500-keV beam with a current of 2 kA and duration of 500 ns decreases with time during the beam current pulse. The same effect was observed in numerical simulations. This effect is explained by a change in the shape of the cathode plasma during the current pulse, which, according to calculations, leads to a change in the beam parameters, such as the electron pitch angle and the spread over the longitudinal electron momentum. These parameters are hard to measure experimentally; however, the time evolution of the radial profile of the beam current density, which can be measured reliably, coincides with the simulation results. This allows one to expect that the behavior of the other beam parameters also agrees with numerical simulations.

  19. Within and Between Canopy Variabilit of Foliar Nitrogen Concentration for Loblolly and Slash Pine Stands Planted at Different Densities

    Treesearch

    Rodney E. Will; Greg Barron-Gafford; Robert O. Teskey; Barry D. Shiver

    2004-01-01

    Mid-summer foliar nitrogen concentrations (N) were measured at three canopy positions (upper, middle, lower), two foliage ages per canopy position (current-year and 1-year-old), and two flushes per age class (first flush and second flush) in 4-year-old loblolly (Pinus taeda L.) and slash pine (Pinus elliottii Engelm.) stands...

  20. To study of different level of nitrogen manure and density on yield and yield component of variety of K.S.C 704 in dry region of sistan

    SciTech Connect

    Dahmardeh, M.; Forghani, F.; Khammari, E.

    2008-01-30

    Out of three grain of the world, Corn is one of the best, About 7 to 10 thousand years ago in south of Mexico corn become domesticated. In the year 1995 culfivation of corn in the world was 130 mil/ha, and to Total production of the world of corn is 507 M/Tons. Average yield of corn in the year 1995 Among Producer countries was 7.78 To 7.60 t/ha in fance and united state was state was 2.36 To 2.20 t/ha, but in Brazil and Mexico Production of corn was different. With this regards, special manner has been arranged for the suitable cultivation or suitable density plants in one heactar on cultivation variety of K.S.C 704 corn. Also suitable level of Nitrogen manure, this Protect in climatic condition of Sistan region done, sith complete block design with 3 replication. Experiment has been selected as split plot, the main plot with 4 different concentration level such as (200-250-3500 and 350 Kg/ha) and sub plot density with 3 different level such as 111000,83000 and 66000 plan/ha respectively. From stage growth up to harvesting of corn in this reache having Data for each treat. ment, After harvesting Analysis of variance and companion of Average of each treatment has been done by DunKan method. Results has been shown, Measurment of characteristics (yield component) seed yield effected different density level of manure, with increasing of manure weight of one thousand seed yield and also in high density showed high significant differente amoung each other. These are with suitable climatic condition of sistan region if enough water will be available ed using Amount of 350 ks/ha Nitrogen manure and with density 111000 plants/ha we can product suitable seed yield Biological yield.

  1. A density functional theory for Lennard-Jones fluids in cylindrical pores and its applications to adsorption of nitrogen on MCM-41 materials.

    PubMed

    Peng, Bo; Yu, Yang-Xin

    2008-11-04

    A density functional theory (DFT) constructed from the modified fundamental-measure theory and the modified Benedict-Webb-Rubin equation of state is presented. The Helmholtz free energy functional due to attractive interaction is expressed as a functional of attractive weighted-density in which the weight function is a mean-field-like type. An obvious advantage of the present theory is that it reproduces accurate bulk properties such as chemical potential, bulk pressure, vapor-liquid interfacial tension, and so forth when compared with molecular simulations and experiments with the same set of molecular parameters. Capabilities of the present DFT are demonstrated by its applicability to adsorption of argon and nitrogen on, respectively, a model cylindrical pore and mesoporous MCM-41 materials. Comparison of the theoretical results of argon in the model cylindrical pore with those from the newly published molecular simulations indicates that the present DFT predicts accurate average densities in the pore, slightly overestimates the pore pressure, and correctly describes the effect of the fluid-pore wall interaction on average densities and pressures in the pore. Application to adsorption of nitrogen on MCM-41 at 77.4 K shows that the present DFT predicts density profiles and adsorption isotherms in good agreement with those from molecular simulations and experiments. In contrast, the hysteresis loop of adsorption calculated from the mean-field theory shifts toward the low pressure region because a low bulk saturated pressure is produced from the mean-field equation of state. The present DFT offers a good way to describe the adsorption isotherms of porous materials as a function of temperature and pressure.

  2. To study of different level of nitrogen manure and density on yield and yield component of variety of K.S.C 704 in dry region of sistan

    NASA Astrophysics Data System (ADS)

    Dahmardeh, M.; Forghani, F.; Khammari, E.

    2008-01-01

    Out of three grain of the world, Corn is one of the best, About 7 to 10 thousand years ago in south of Mexico corn become domesticated. In the year 1995 culfivation of corn in the world was 130 mil/ha, and to Total production of the world of corn is 507 M/Tons. Average yield of corn in the year 1995 Among Producer countries was 7.78 To 7.60 t/ha in fance and united state was state was 2.36 To 2.20 t/ha, but in Brazil and Mexico Production of corn was different. With this regards, special manner has been arranged for the suitable cultivation or suitable density plants in one heactar on cultivation variety of K.S.C 704 corn. Also suitable level of Nitrogen manure, this Protect in climatic condition of Sistan region done, sith complete block design with 3 replication. Experiment has been selected as split plot, the main plot with 4 different concentration level such as (200-250-3500 and 350 Kg/ha) and sub plot density with 3 different level such as 111000,83000 and 66000 plan/ha respectively. From stage growth up to harvesting of corn in this reache having Data for each treat. ment, After harvesting Analysis of variance and companion of Average of each treatment has been done by DunKan method. Results has been shown, Measurment of characteristics (yield component) seed yield effected different density level of manure, with increasing of manure weight of one thousand seed yield and also in high density showed high significant differente amoung each other. These are with suitable climatic condition of sistan region if enough water will be available ed using Amount of 350 ks/ha Nitrogen manure and with density 111000 plants/ha we can product suitable seed yield Biological yield.

  3. Electrical and hydrodynamic characterization of a high current pulsed arc

    NASA Astrophysics Data System (ADS)

    Sousa Martins, R.; Chemartin, L.; Zaepffel, C.; Lalande, Ph; Soufiani, A.

    2016-05-01

    High current pulsed arcs are of significant industrial interest and, aiming to reduce time and cost, there is progressively more and more need for computation tools that describe and predict the behaviour of these arcs. These simulation codes need inputs and validations by experimental databases, but accurate data is missing for this category of electric discharges. The principal lack of understanding is with respect to the transient phase of the current, which can reach thousands of amperes in a few microseconds. In this paper, we present the work realized on an experimental setup that simulates in the laboratory an arc column subjected to five levels of high pulsed current, ranging from 10 kA to 100 kA, with the last one corresponding to the standard lightning current waveform used in aircraft certification processes. This device was instrumented by high speed video cameras to assess the characteristic sizes of the arc channel and to characterize the shock wave generated by the arc expansion. The arc channel radius was measured over time during the axisymmetric phase and reached 3.2 cm. The position and velocity of the shock wave was determined during the first 140 μs. The background-oriented schlieren method was used to study the shock wave and a model for the light deflection inside the shock wave was developed. The mass density profile of the shock wave was estimated and showed good agreement with Rankine-Hugoniot relations at the wave front. Electrical measurements were also used to estimate the time-dependent resistance and conductivity of the arc for times lasting up to 50 μs.

  4. The high current transport experiment for heavy ion inertial fusion

    SciTech Connect

    Prost, L.R.; Baca, D.; Bieniosek, F.M.; Celata, C.M.; Faltens, A.; Henestroza, E.; Kwan, J.W.; Leitner, M.; Seidl, P.A.; Waldron, W.L.; Cohen, R.; Friedman, A.; Grote, D.; Lund, S.M.; Molvik, A.W.; Morse, E.

    2004-05-01

    The High Current Experiment (HCX) at Lawrence Berkeley National Laboratory is part of the US program to explore heavy-ion beam transport at a scale representative of the low-energy end of an induction linac driver for fusion energy production. The primary mission of this experiment is to investigate aperture fill factors acceptable for the transport of space-charge-dominated heavy-ion beams at high intensity (line charge density {approx} 0.2 {micro}C/m) over long pulse durations (4 {micro}s) in alternating gradient focusing lattices of electrostatic or magnetic quadrupoles. This experiment is testing transport issues resulting from nonlinear space-charge effects and collective modes, beam centroid alignment and steering, envelope matching, image charges and focusing field nonlinearities, halo and, electron and gas cloud effects. We present the results for a coasting 1 MeV K{sup +} ion beam transported through ten electrostatic quadrupoles. The measurements cover two different fill factor studies (60% and 80% of the clear aperture radius) for which the transverse phase-space of the beam was characterized in detail, along with beam energy measurements and the first halo measurements. Electrostatic quadrupole transport at high beam fill factor ({approx}80%) is achieved with acceptable emittance growth and beam loss, even though the initial beam distribution is not ideal (but the emittance is low) nor in thermal equilibrium. We achieved good envelope control, and rematching may only be needed every ten lattice periods (at 80% fill factor) in a longer lattice of similar design. We also show that understanding and controlling the time dependence of the envelope parameters is critical to achieving high fill factors, notably because of the injector and matching section dynamics.

  5. Understanding the interplay of carbon and nitrogen supply for ectoines production and metabolic overflow in high density cultures of Chromohalobacter salexigens.

    PubMed

    Salar-García, María J; Bernal, Vicente; Pastor, José M; Salvador, Manuel; Argandoña, Montserrat; Nieto, Joaquín J; Vargas, Carmen; Cánovas, Manuel

    2017-02-08

    The halophilic bacterium Chromohalobacter salexigens has been proposed as promising cell factory for the production of the compatible solutes ectoine and hydroxyectoine. This bacterium has evolved metabolic adaptations to efficiently grow under high salt concentrations by accumulating ectoines as compatible solutes. However, metabolic overflow, which is a major drawback for the efficient conversion of biological feedstocks, occurs as a result of metabolic unbalances during growth and ectoines production. Optimal production of ectoines is conditioned by the interplay of carbon and nitrogen metabolisms. In this work, we set out to determine how nitrogen supply affects the production of ectoines. Chromohalobacter salexigens was challenged to grow in media with unbalanced carbon/nitrogen ratio. In C. salexigens, overflow metabolism and ectoines production are a function of medium composition. At low ammonium conditions, the growth rate decreased importantly, up to 80%. Shifts in overflow metabolism were observed when changing the C/N ratio in the culture medium. (13)C-NMR analysis of ectoines labelling revealed a high metabolic rigidity, with almost constant flux ratios in all conditions assayed. Unbalanced C/N ratio led to pyruvate accumulation, especially upon N-limitation. Analysis of an ect (-) mutant demonstrated the link between metabolic overflow and ectoine biosynthesis. Under non ectoine synthesizing conditions, glucose uptake and metabolic overflow decreased importantly. Finally, in fed-batch cultures, biomass yield was affected by the feeding scheme chosen. High growth (up to 42.4 g L(-1)) and volumetric ectoine yields (up to 4.21 g L(-1)) were obtained by minimizing metabolite overflow and nutrient accumulation in high density cultures in a low nitrogen fed-batch culture. Moreover, the yield coefficient calculated for the transformation of glucose into biomass was 30% higher in fed-batch than in the batch culture, demonstrating that the metabolic

  6. Reactive spark plasma sintering of MgB2 in nitrogen atmosphere for the enhancement of the high-field critical current density

    NASA Astrophysics Data System (ADS)

    Badica, P.; Burdusel, M.; Popa, S.; Pasuk, I.; Ivan, I.; Borodianska, H.; Vasylkiv, O.; Kuncser, A.; Ionescu, A. M.; Miu, L.; Aldica, G.

    2016-10-01

    High density bulks (97%-99%) of MgB2 were prepared by spark plasma sintering (SPS) in nitrogen (N2) atmosphere for different heating rates (10, 20 and 100 °C min-1) and compared with reference samples processed in vacuum and Ar. N2 reacts with MgB2 and forms MgB9N along the MgB2 grain boundaries. The high-field critical current density is enhanced for the sample processed in N2 with a heating rate of 100 °C min-1. At 2-35 K, this sample shows the strongest contribution of the grain boundary pinning (GBP). All samples are in the point pinning (PP) limit and by increasing temperature the GBP contribution decreases.

  7. Inter-Comparison of Nitrogen Dioxide Column Densities Retrieved by Ground-Based Max-Doas Under Different Instrumental Conditions Over Mainz

    NASA Astrophysics Data System (ADS)

    Bruchkouski, I.; Dziomin, V.; Ortega, I.; Volkamer, R.; Krasouski, A.

    2013-12-01

    This study is dedicated to the instrumental differences between ground-based MAX-DOAS measurement devices. Our MAX-DOAS instrument, which has been developed at the National Ozone Monitoring Research & Education Center of the Belarusian State University for the purpose of nitrogen dioxide and other atmospheric trace gases monitoring over Belarus, features a rotating mirror and a telescope directly connected to the spectrometer with a two-dimensional CCD detector. Using a mirror instead of an optical fibre makes it possible to change the field of view of the telescope, and the whole instrument is rather compact and all its components are placed outdoors in the open air. However, this makes it quite difficult to ensure a top-quality thermostabilization. In the course of the MAX-DOAS campaign, which took place in the Max Planck Institute for Chemistry in Mainz, Germany in summer of 2013, we had a great opportunity to compare our instrument with other devices of different types. In the present study we make a comparison of nitrogen dioxide slant column densities (SCDs) during several days obtained by our instrument with that measured by the device from the Department of Chemistry and Biochemistry, University of Colorado (Boulder), which has a thermostabilization level of about 0.01 degrees Celsius. We investigate the influence of the spectrometer parts thermostabilization on nitrogen dioxide SCDs retrieval. Furthermore, it was possible to modify the telescope field of view for our instrument from 0.005 to 1.3 degrees, so we performed nitrogen dioxide SCDs retrieval for different fields of view at the same angle of elevation. We analyze these measurement results and obtain an optimal field of view with the aim to achieve the highest possible signal to noise ratio.

  8. [Effect of grass barrier-combined filter strips on the reduction of nitrogen and phosphorus concentration under concentrated flow of varying densities].

    PubMed

    Du, Qin; Wang, Jin-ye; Li, Hai-fang

    2015-09-01

    Vegetative barrier-combined filter strips are defined as grass barriers set up before filter strips. They could make concentrated water flow disperse, which exerts the function of grass barriers (i.e., existence of grass barriers improves the performance of filter strips in the purification of pollutants). In this regards, grass barriers are generally considered to be effective in the purification of pollutants when the density of concentrated flow is low, whereas little was known about this effect with an increasing density of concentrated flow. In this study, we constructed Miscanthus floridulus barrier before Vitex negundo filter strip with three densities of concentrated flow (low: one concentrated flow channel; middle: three channels; high: five channels). The aim of work was to identify the effect of M. floridulus combined V. negundo filter strips in reducing nitrogen and phosphorus concentration under three concentrated water flow levels. Our results showed that the combined filter strips had a higher performance in the reduction in the total N, NH(4+)-N, NO(3-)-N and total P compared to those in the V. negundo (P < 0.05), regardless of the water flow level. There was no significant difference in the reduction of total N, NH(4+)-N, NO(3-)-N and total P among three water flow levels (P > 0.05). We concluded that M. floridulus combined V. negundo filter strips could improve the reduction of nutrients, which couldn' t be influenced by varying density of concentrated flow level.

  9. Non-equilibrium vibrational and electron energy distribution functions in mtorr, high-electron-density nitrogen discharges and afterglows

    NASA Astrophysics Data System (ADS)

    Capitelli, M.; Colonna, G.; D’Ammando, G.; Laricchiuta, A.; Pietanza, L. D.

    2017-03-01

    Non-equilibrium vibrational distributions (vdf) and non-equilibrium electron energy distribution functions (eedf) in a nitrogen plasma at low pressure (mtorr) have been calculated by using a time-dependent plasma physics model coupled to the Boltzmann equation and heavy particle kinetics. Different case studies have been selected showing the non-equilibrium character of both vdf and eedf under discharge and post-discharge conditions in the presence of large concentrations of electrons. Particular attention is devoted to the electron-molecule resonant vibrational excitation cross sections acting in the whole vibrational ladder. The results in the post-discharge conditions show the interplay of superelastic vibrational and electronic collisions in forming structures in the eedf. The link between the present results in the mtorr afterglow regime with the existing eedf in the torr and atmospheric regimes is discussed.

  10. New Pulsed Power Technology for High Current Accelerators

    SciTech Connect

    Caporaso, G J

    2002-06-27

    Recent advances in solid-state modulators now permit the design of a new class of high current accelerators. These new accelerators will be able to operate in burst mode at frequencies of several MHz with unprecedented flexibility and precision in pulse format. These new modulators can drive accelerators to high average powers that far exceed those of any other technology and can be used to enable precision beam manipulations. New insulator technology combined with novel pulse forming lines and switching may enable the construction of a new type of high gradient, high current accelerator. Recent developments in these areas will be reviewed.

  11. Surface modification of structural materials by low-energy high-current pulsed electron beam treatment

    SciTech Connect

    Panin, A. V. E-mail: kms@ms.tsc.ru; Kazachenok, M. S. E-mail: kms@ms.tsc.ru; Sinyakova, E. A.; Borodovitsina, O. M.; Ivanov, Yu. F.; Leontieva-Smirnova, M. V.

    2014-11-14

    Microstructure formation in surface layers of pure titanium and ferritic-martensitic steel subjected to electron beam treatment is studied. It is shown that low energy high-current pulsed electron beam irradiation leads to the martensite structure within the surface layer of pure titanium. Contrary, the columnar ferrite grains grow during solidification of ferritic-martensitic steel. The effect of electron beam energy density on the surface morphology and microstructure of the irradiated metals is demonstrated.

  12. Inter-comparison of nitrogen dioxide column densities retrieved by ground-based MAX-DOAS and Pandora, and space borne OMI measurements over Seoul

    NASA Astrophysics Data System (ADS)

    Yun, S.; Lee, H.; Kim, J.; Jeong, U.; Herman, J. R.

    2013-12-01

    It is important to understand spatial and temporal characteristics of nitrogen dioxide (NO2) which affects atmospheric chemistry with respect to aerosol and ozone formation. In this present study, we used Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) and Pandora to investigate vertical information of NO2. The measurements took place from August to October in 2013 in Seoul, one of the largest megacities in Northeast Asia. Slant column densities (SCDs) of NO2 at each elevation angle (EA) were derived using the MAX-DOAS technique that utilizes scattered sunlight at multiple EAs as a light source. Vertical distributions of tropospheric NO2 were retrieved utilizing measured SCDs and those simulated with Trace gas RAdiative Transfer Monte Carlo Y(I)mplementation (TRACY) with inputs of aerosol optical properties from sunphotometer and Micro Pulse LIDAR (MPL) measurements. On the other hand, Pandora, which uses direct sunlight as a light source, was used to obtain total NO2 column densities for the same measurement period. Tropospheric and total NO2 column densities retrieved using those two ground based instruments were compared with those obtained from Ozone Monitoring Instrument (OMI) data.

  13. Ecosystem respiration, vegetation development and soil nitrogen in relation to breeding density of seagulls on a pristine volcanic island, Surtsey, Iceland

    NASA Astrophysics Data System (ADS)

    Sigurdsson, B. D.; Magnusson, B.

    2009-08-01

    Since its birth in 1963 by volcanic eruption in the North Atlantic Ocean off Iceland, Surtsey has been a unique natural laboratory on how organisms colonize volcanic islands and form ecosystems with contrasting structure and function. In July, 2004, ecosystem respiration rate, soil properties and surface cover of vascular plants were measured on 21 plots distributed among the main plant communities found 40 years after the primary succession started. The plots could be divided into two groups, inside and outside seagull (Larus sp.) colonies found on the island. Vegetation cover of the plots was strongly related to the density of seagull nests within and around them. The occurrence of seagull nests and increased vegetation also coincided with significant increase in ecosystem respiration, soil carbon and nitrogen, and with significantly lower soil pH and soil temperatures. The ecosystem respiration was high inside the gull colonies, similar to the highest fluxes measured in drained wetlands or agricultural fields in Iceland. The most important factor for vegetation succession and ecosystem function on Surtsey seems to be the amount of nitrogen, which was mainly brought in by the seagulls.

  14. ASRDI oxygen technology survey. Volume 5: Density and liquid level measurement instrumentation for the cryogenic fluids oxygen, hydrogen, and nitrogen

    NASA Technical Reports Server (NTRS)

    Roder, H. M.

    1974-01-01

    Information is presented on instrumentation for density measurement, liquid level measurement, quantity gauging, and phase measurement. Coverage of existing information directly concerned with oxygen was given primary emphasis. A description of the physical principle of measurement for each instrumentation type is included. The basic materials of construction are listed if available from the source document for each instrument discussed. Cleaning requirements, procedures, and verification techniques are included.

  15. Absolute atomic oxygen and nitrogen densities in radio-frequency driven atmospheric pressure cold plasmas: Synchrotron vacuum ultra-violet high-resolution Fourier-transform absorption measurements

    SciTech Connect

    Niemi, K.; O'Connell, D.; Gans, T.; Oliveira, N. de; Joyeux, D.; Nahon, L.; Booth, J. P.

    2013-07-15

    Reactive atomic species play a key role in emerging cold atmospheric pressure plasma applications, in particular, in plasma medicine. Absolute densities of atomic oxygen and atomic nitrogen were measured in a radio-frequency driven non-equilibrium plasma operated at atmospheric pressure using vacuum ultra-violet (VUV) absorption spectroscopy. The experiment was conducted on the DESIRS synchrotron beamline using a unique VUV Fourier-transform spectrometer. Measurements were carried out in plasmas operated in helium with air-like N{sub 2}/O{sub 2} (4:1) admixtures. A maximum in the O-atom concentration of (9.1 {+-} 0.7) Multiplication-Sign 10{sup 20} m{sup -3} was found at admixtures of 0.35 vol. %, while the N-atom concentration exhibits a maximum of (5.7 {+-} 0.4) Multiplication-Sign 10{sup 19} m{sup -3} at 0.1 vol. %.

  16. The role of termites in an equatorial rain forest ecosystem of West Malaysia : I. Population density, biomass, carbon, nitrogen and calorific content and respiration rate.

    PubMed

    Matsumoto, Tadao

    1976-06-01

    1. Density of nests, population number, biomass, nitrogen and carbon content, calorific content and respiration rate of termites were studied at Pasoh Forest, West Malaysia mainly with four dominant species of epigeous nest builders, Macrotermes carbonarius, Dicuspiditermes nemorosus type-a, type-b and Homallotermes foraminifer, to reveal their role in the ecosystem. 2. The density of nests or mounds was 15-41/ha in M. carbonarius, 60-110/ha in the two types of D. nemorosus and 85-165/ha in H. foraminifer. 3. The population number per nest or mound was about 88,000 in M. carbonarius, 45,000 in D. nemorosus type-a, 47,000 in D. nemorosus type-b and 13,000 in H. foraminifer. The population number per hectare was about 1.8x10(6) for M. carbonarius, 4.3x10(6) for D. nemorosus type-a, 5.2x10(6) for D. nemorosus type-b and 2.1x10(6) for H. foraminifer. 4. The ratio in number of workers to soldiers was 6.4 for M. carbonarius, 19.0 for D. nemorosus type-a, 23.1 for D. nemorosus type-b and 8.9 for H. foraminifer. The ratio in number of adults (workers plus soldiers) to larvae was 1.4 for M. carbonarius, 0.59 for D. nemorosus type-a, 1.76 for D. nemorosus type-b and 3.84 for H. foraminifer. 5. The number of adults per nest of D. nemorosus type-a, type-b and H. foraminifer was linearly correlated with the weight of nest on the log-log coordinates. 6. The ratio of dry body weight to live weight was 0.24-0.30 for workers, 0.19-0.29 for soldiers and 0.15-0.22 for larvae. 7. The ash content of termite body was 26-66% for workers, 2-24% for soldiers and 1-4% for larvae. 8. The carbon content ranged from 45% to 66% of ash-free dry weight and the nitrogen content from 5.6% to 12.6%. 9. The mean calorific value of termite body was 5.3 gcal/mg in workers and soldiers on an ash-free weight basis, but was greater in nymphs and winged reproductives in the nest (6.7-6.9 gcal/mg) owing probably to their large fat storage. 10. The relation of CO2 evolution rate to temperature in these

  17. A Nitrogen-Doped Carbon Catalyst for Electrochemical CO2 Conversion to CO with High Selectivity and Current Density.

    PubMed

    Jhong, Huei-Ru Molly; Tornow, Claire E; Smid, Bretislav; Gewirth, Andrew A; Lyth, Stephen M; Kenis, Paul J A

    2017-03-22

    We report characterization of a non-precious metal-free catalyst for the electrochemical reduction of CO2 to CO; namely, a pyrolyzed carbon nitride and multiwall carbon nanotube composite. This catalyst exhibits a high selectivity for production of CO over H2 (approximately 98 % CO and 2 % H2 ), as well as high activity in an electrochemical flow cell. The CO partial current density at intermediate cathode potentials (V=-1.46 V vs. Ag/AgCl) is up to 3.5× higher than state-of-the-art Ag nanoparticle-based catalysts, and the maximum current density is 90 mA cm(-2) . The mass activity and energy efficiency (up to 48 %) were also higher than the Ag nanoparticle reference. Moving away from precious metal catalysts without sacrificing activity or selectivity may significantly enhance the prospects of electrochemical CO2 reduction as an approach to reduce atmospheric CO2 emissions or as a method for load-leveling in relation to the use of intermittent renewable energy sources.

  18. High-current fast electron beam propagation in a dielectric target.

    PubMed

    Klimo, Ondrej; Tikhonchuk, V T; Debayle, A

    2007-01-01

    Recent experiments demonstrate an efficient transformation of high intensity laser pulse into a relativistic electron beam with a very high current density exceeding 10(12) A cm(-2). The propagation of such a beam inside the target is possible if its current is neutralized. This phenomenon is not well understood, especially in dielectric targets. In this paper, we study the propagation of high current density electron beam in a plastic target using a particle-in-cell simulation code. The code includes both ionization of the plastic and collisions of newborn electrons. The numerical results are compared with a relatively simple analytical model and a reasonable agreement is found. The temporal evolution of the beam velocity distribution, the spatial density profile, and the propagation velocity of the ionization front are analyzed and their dependencies on the beam density and energy are discussed. The beam energy losses are mainly due to the target ionization induced by the self-generated electric field and the return current. For the highest beam density, a two-stream instability is observed to develop in the plasma behind the ionization front and it contributes to the beam energy losses.

  19. A Double-Pole High Voltage High Current Switch

    DTIC Science & Technology

    2005-12-01

    NAVAL POSTGRADUATE SCHOOL MONTEREY, CALIFORNIA THESIS Approved for public release; distribution is unlimited A DOUBLE- POLE HIGH...December 2005 3. REPORT TYPE AND DATES COVERED Master’s Thesis 4. TITLE AND SUBTITLE: A Double- Pole High Voltage High Current Switch 6. AUTHOR(S...to divert heavy charged particles, e.g. Cu+. 15. NUMBER OF PAGES 68 14. SUBJECT TERMS Double- Pole , Pulse Forming Inductive Network, PFIN

  20. Application of RF Superconductivity to High Current Linac

    SciTech Connect

    Chan K.C.D.

    1998-09-13

    In 1997, the authors initiated a development program in Los Alamos for high-current superconducting proton-linac technology to build prototypes components of this linac to demonstrate the feasibility. The authors are building 700-MHz niobium cavities with elliptical shapes, as well as power couplers to transfer high RF power to these cavities. The cavities and power couplers will be integrated in cryostats as linac cryomodules. In this paper, they describe the linac design and the status of the development program.

  1. High-current, fast-switching transistor development

    NASA Technical Reports Server (NTRS)

    Hower, P. L.

    1981-01-01

    The design, wafer-processing techniques, and various measurements which include forward safe operating area, dc characteristics, and switching times are described for a larger-diameter (33) transistor. An improved base contact for equalizing the base-emitter voltage at high currents was developed along with an improved emitter contact preform which increases the silicon area available for current conduction. The electrical performance achieved is consistent with the proposed optimum design.

  2. Large area polycrystalline diamond films as high current photocathodes for linear induction accelerators

    SciTech Connect

    Shurter, R.P.; Moir, D.C.; Devlin, D.J.; Springer, R.W.

    1997-08-01

    Investigations are underway at Los Alamos to develop a new generation of high current, low source temperature photo cathodes able to operate in vacuum environments with pressures above 10e-6 torr without poisoning or degradation of emission properties. Polycrystalline diamond films are emerging as the ideal material for these photocathodes. Robustness, high quantum efficiency and high thermal conductivity are fundamental necessary attributes that are found in diamond. The high electron/hole mobility in the boron doped diamond lattice and the ability to create a negative electron affinity surface through downward band bending allow for high current density emission with quantum efficiencies of 0.5% when illuminated by a ArF laser. We report the results to date toward the development of a four kiloampere photocathode with a source temperature below 5eV for the DARHT linear induction Accelerator

  3. Landscape Soil Respiration Fluxes are Related to Leaf Area Index, Stand Height and Density, and Soil Nitrogen in Rocky Mountain Subalpine Forests

    NASA Astrophysics Data System (ADS)

    Berryman, E.; Bradford, J. B.; Hawbaker, T. J.; Birdsey, R.; Ryan, M. G.

    2015-12-01

    There is a recent multi-agency push for accurate assessments of terrestrial carbon stocks and fluxes in the United States. Assessing the state of the carbon cycle in the US requires estimates of stocks and fluxes at large spatial scales. Such assessments are difficult, especially for soil respiration, which dominates ecosystem respiration and is notoriously highly variable over space and time. Here, we report three consecutive years of measurement of soil respiration fluxes in three 1 km2 subalpine forest landscapes: Fraser Experimental Forest (Colorado), Glacier Lakes Ecosystems Experimental Site ("GLEES", Wyoming), and Niwot Ridge (Colorado). Plots were established following the protocol of the US Forest Service's Forest Inventory and Analysis (FIA) Program. Clusters of plots were distributed across the landscape in a 0.25 km grid pattern. From 2004 through 2006, measurements of soil respiration were made once monthly during the growing season and twice during snowpack coverage for each year. Annual cumulative soil respiration was 6.10 (+/- 0.21) Mg ha-1y-1 for Fraser, 6.55 (+/- 0.27) Mg ha-1y-1 for GLEES, and 6.97 (+/- 0.20) Mg ha-1y-1 for Niwot. Variability in annual cumulative soil respiration varied by less than 20% among the three subalpine forests, despite differences in terrain, climate, disturbance history and anthropogenic nitrogen deposition. We quantified the relationship between respiration fluxes and commonly-measured forest properties and found that soil respiration was nonlinearly related to leaf area index, peaking around 2.5 m2m-2 then slowly declining. Annual litterfall (FA) was subtracted from soil respiration (FR) to calculate total belowground carbon flux (TBCF), which declined with increasing tree height, density and soil nitrogen. This landscape analysis of soil respiration confirmed experimentally-derived principles governing carbon fluxes in forests: as trees age and get taller, and in high-fertility areas, carbon flux to roots declines

  4. The Optimal Lateral Root Branching Density for Maize Depends on Nitrogen and Phosphorus Availability1[C][W][OPEN

    PubMed Central

    Postma, Johannes Auke; Dathe, Annette; Lynch, Jonathan Paul

    2014-01-01

    Observed phenotypic variation in the lateral root branching density (LRBD) in maize (Zea mays) is large (1–41 cm−1 major axis [i.e. brace, crown, seminal, and primary roots]), suggesting that LRBD has varying utility and tradeoffs in specific environments. Using the functional-structural plant model SimRoot, we simulated the three-dimensional development of maize root architectures with varying LRBD and quantified nitrate and phosphorus uptake, root competition, and whole-plant carbon balances in soils varying in the availability of these nutrients. Sparsely spaced (less than 7 branches cm−1), long laterals were optimal for nitrate acquisition, while densely spaced (more than 9 branches cm−1), short laterals were optimal for phosphorus acquisition. The nitrate results are mostly explained by the strong competition between lateral roots for nitrate, which causes increasing LRBD to decrease the uptake per unit root length, while the carbon budgets of the plant do not permit greater total root length (i.e. individual roots in the high-LRBD plants stay shorter). Competition and carbon limitations for growth play less of a role for phosphorus uptake, and consequently increasing LRBD results in greater root length and uptake. We conclude that the optimal LRBD depends on the relative availability of nitrate (a mobile soil resource) and phosphorus (an immobile soil resource) and is greater in environments with greater carbon fixation. The median LRBD reported in several field screens was 6 branches cm−1, suggesting that most genotypes have an LRBD that balances the acquisition of both nutrients. LRBD merits additional investigation as a potential breeding target for greater nutrient acquisition. PMID:24850860

  5. Spectroscopic density and temperature measurements and modelling of a discharge plasma for neutralized ion-beam transport

    NASA Astrophysics Data System (ADS)

    Niemann, C.; Rosmej, F. B.; Tauschwitz, A.; Neff, S.; Penache, D.; Birkner, R.; Constantin, C.; Knobloch, R.; Presura, R.; Hoffmann, D. H. H.; Yu, S. S.; Lee, R. W.

    2003-09-01

    High-current discharge channels are ideally suited for the focusing and transport of intense charged particle beams. The azimuthal magnetic field provides a strong focusing force, which acts symmetrically towards the discharge axis. A sufficiently dense and hot plasma can also neutralize the beam current and space charge of very intense ion beams, relevant to a number of future applications. In this paper we present experiments on high-current discharge channels designed for the transport of heavy ion beams. A spectroscopic method is introduced, which allows us to determine both the plasma temperature and density in hydrogen-nitrogen plasmas, from comparisons of the measurements with computer calculations. The temperature is derived from a comparison of experimentally obtained relative nitrogen-line intensities with a collisional radiative rate modelling of the nitrogen plasma. The electron density is determined by a detailed line shape analysis of the Stark-broadened hydrogen Balmer lines.

  6. Astro-E2 Magnesium Diboride High Current Leads

    NASA Technical Reports Server (NTRS)

    Panek, J. S.; Tuttle, J. G.; Riall, S.; Mustafi, S.; Gray, A.; Edmonds, R.; Marrero, V.

    2003-01-01

    The recent discovery of superconducting properties in MgB_2 and rapid development of small diameter steel-clad wires has opened up the possibility of enhancing the design of the baseline Astro-E2 high current lead assembly. Replacing YBCO filaments with MgB_2 wires and modifying the heat sink location can give much higher margins against quench from temperature oscillations of the 4 K heat sink, although wih some overall thermal penalty. The design and performance of a new lead assembly during flight qualification is discussed, with emphasis on thermal, structural, and electrical test results.

  7. Development of RF linac for high-current applications

    SciTech Connect

    Chan, K.C.D.; Lawrence, G.P.; Schneider, J.D.

    1997-12-31

    High-current proton linacs are promising sources of neutrons for material processing and research applications. Recently, a linac design that makes use of a combination of normal-conducting (NC) and superconducting (SC) linac technologies has been proposed for the US Accelerator Production of Tritium Project. As a result, a multi-year engineering development and demonstration (ED and D) program is underway. In this paper, the authors will describe the design and merits of the NC/SC hybrid approach. The scope, technology issues, and present status of the ED and D Program, and the participation of industry will also be described.

  8. Pulsed High-Current Experiments at IPP ASci CR Prague

    SciTech Connect

    Kolacek, K.; Schmidt, J.; Prukner, V.; Frolov, O.; Straus, J.; Bohacek, V.; Martinkova, M.

    2006-01-05

    The aim of our first high current capillary discharge was to reach amplified spontaneous emission on neon-like argon ({lambda} = 46.9 nm). This was finally accomplished. Our new capillary discharge experiment has larger transverse dimensions, four-channel laser-triggered spark gap, and free optical access to both capillary ends. At present it is electrically tested. In this apparatus the capillary can be replaced by a device with exploding wire in water locally compressed by focused cylindrical converging shock wave (for soft X-ray lasing at shorter wavelength). This part is also at present tested.

  9. Pulsed High-Current Experiments at IPP ASci CR Prague

    NASA Astrophysics Data System (ADS)

    Kolacek, K.; Schmidt, J.; Prukner, V.; Frolov, O.; Straus, J.; Bohacek, V.; Martinkova, M.

    2006-01-01

    The aim of our first high current capillary discharge was to reach amplified spontaneous emission on neon-like argon (λ = 46.9 nm). This was finally accomplished. Our new capillary discharge experiment has larger transverse dimensions, four-channel laser-triggered spark gap, and free optical access to both capillary ends. At present it is electrically tested. In this apparatus the capillary can be replaced by a device with exploding wire in water locally compressed by focused cylindrical converging shock wave (for soft X-ray lasing at shorter wavelength). This part is also at present tested.

  10. High Current Cathode Thermal Behavior, Part II: Theory

    NASA Technical Reports Server (NTRS)

    Goodfellow, K. D.; Polk, J. E.

    1993-01-01

    Cathode erosion is one of the life limiting mechanisms for several classes of electric thrusters. Since cathode erosion is strongly dependent on the cathode temperature, a quantitative understanding of the effects of cathode operation on the cathode temperature is required. The development of a cathode/plasma interaction model for determining the heat loads to the cathode as function of the various free stream plasma parameters is presented. This model is combined with a cathode thermal model in order to provide a complete and integrated picture of high current cathode operation.

  11. High Current Ion Sources and Injectors for Heavy Ion Fusion

    SciTech Connect

    Kwan, Joe W.

    2005-02-15

    Heavy ion beam driven inertial fusion requires short ion beam pulses with high current and high brightness. Depending on the beam current and the number of beams in the driver system, the injector can use a large diameter surface ionization source or merge an array of small beamlets from a plasma source. In this paper, we review the scaling laws that govern the injector design and the various ion source options including the contact ionizer, the aluminosilicate source, the multicusp plasma source, and the MEVVA source.

  12. Astro-E2 Magnesium Diboride High Current Leads

    NASA Technical Reports Server (NTRS)

    Panek, J. S.; Tuttle, J. G.; Riall, S.; Mustafi, S.; Gray, A.; Edmonds, R.; Marrero, V.

    2003-01-01

    The recent discovery of superconducting properties in MgB_2 and rapid development of small diameter steel-clad wires has opened up the possibility of enhancing the design of the baseline Astro-E2 high current lead assembly. Replacing YBCO filaments with MgB_2 wires and modifying the heat sink location can give much higher margins against quench from temperature oscillations of the 4 K heat sink, although wih some overall thermal penalty. The design and performance of a new lead assembly during flight qualification is discussed, with emphasis on thermal, structural, and electrical test results.

  13. Broad-beam, high current, metal ion implantation facility

    SciTech Connect

    Brown, I.G.; Dickinson, M.R.; Galvin, J.E.; Godechot, X.; MacGill, R.A.

    1990-07-01

    We have developed a high current metal ion implantation facility with which high current beams of virtually all the solid metals of the Periodic Table can be produced. The facility makes use of a metal vapor vacuum arc ion source which is operated in a pulsed mode, with pulse width 0.25 ms and repetition rate up to 100 pps. Beam extraction voltage is up to 100 kV, corresponding to an ion energy of up to several hundred keV because of the ion charge state multiplicity; beam current is up to several Amperes peak and around 10 mA time averaged delivered onto target. Implantation is done in a broad-beam mode, with a direct line-of-sight from ion source to target. Here we describe the facility and some of the implants that have been carried out using it, including the seeding' of silicon wafers prior to CVD with titanium, palladium or tungsten, the formation of buried iridium silicide layers, and actinide (uranium and thorium) doping of III-V compounds. 16 refs., 6 figs.

  14. Energetic neutral contamination in modern high-current implanters

    NASA Astrophysics Data System (ADS)

    Cherekdjian, S.; Weisenberger, W.

    1991-04-01

    The presence of energetic neutrals in a high-current, high-energy implant can result in nonuniformities on a silicon wafer. A larger concern is when the energetic neutrals are not of the desired energy. This is a major consideration when designing ion implanters with pre- and post-acceleration stages. This paper investigates the levels of pre-accelerated boron neutrals present in a 180 kV boron implant. The machines investigated were a Nova 20A and an Applied Materials PI9000. A comparison of their vacuum systems and their ability to cope with photoresist batches and argon backfill are presented. Silicon wafers were mapped by four-point probe resistivity measurements and the levels of pre-accelerated neutrals were quantified by spreading resistance profiles (SRPs). It is clearly demonstrated that good uniformity on a bare silicon wafer is not an indicator of a clean ion beam. Even though it is well understood that this problem is vacuum-related, modern high-current implanters are still being built and marketed with improper vacuum isolation and insufficient pumping capability.

  15. High current pulse testing for ground rod integrity

    NASA Technical Reports Server (NTRS)

    Walko, Lawrence C.

    1991-01-01

    A test technique was developed to assess various grounding system concepts used for mobile facilities. The test technique involves applying a high current pulse to the grounding system with the proper waveshape and magnitude to simulate a lightning return stroke. Of concern were the step voltages present along the ground near the point of lightning strike. Step voltage is equated to how fast the current pulse is dissipated by the grounding system. The applied current pulse was produced by a high current capacitor bank with a total energy content of 80 kilojoules. A series of pulse tests were performed on two types of mobile facility grounding systems. One system consisted of an array of four 10 foot copper clad steel ground rods connected by 1/0 gauge wire. The other system was an array of 10 inch long tapered ground rods, strung on stainless steel cable. The focus here is on the pulse test technique used and its relevance to actual lightning strike conditions.

  16. RF Input Power Couplers for High Current SRF Applications

    SciTech Connect

    Khan, V. F.; Anders, W.; Burrill, Andrew; Knobloch, Jens; Kugeler, Oliver; Neumann, Axel; Wang, Haipeng

    2014-12-01

    High current SRF technology is being explored in present day accelerator science. The bERLinPro project is presently being built at HZB to address the challenges involved in high current SRF machines with the goal of generating and accelerating a 100 mA electron beam to 50 MeV in continuous wave (cw) mode at 1.3 GHz. One of the main challenges in this project is that of handling the high input RF power required for the photo-injector as well as booster cavities where there is no energy recovery process. A high power co-axial input power coupler is being developed to be used for the photo-injector and booster cavities at the nominal beam current. The coupler is based on the KEK–cERL design and has been modified to minimise the penetration of the coupler tip in the beam pipe without compromising on beam-power coupling (Qext ~105). Herein we report on the RF design of the high power (115 kW per coupler, dual couplers per cavity) bERLinPro (BP) coupler along with initial results on thermal calculations. We summarise the RF conditioning of the TTF-III couplers (modified for cw operation) performed in the past at BESSY/HZB. A similar conditioning is envisaged in the near future for the low current SRF photo-injector and the bERLinPro main linac cryomodule.

  17. Developing High Brightness and High Current Beams for HIF Injectors

    SciTech Connect

    Ahle, L; Kwan, J W

    2002-05-10

    The US Heavy Ion Fusion Virtual National Laboratory is continuing research into ion sources and injectors that simultaneously provide high current (0.5-1.0 Amps) and high brightness (normalized emittance better than 1.0 {pi}-mm-mr). The central issue of focus is whether to carry on the traditional approach of large surface ionization sources or to adopt a multi-aperture approach that transports many smaller ''beamlets'' separately at low energies before allowing them to merge. For the large surface source, the recent commissioning of the 2-MeV injector for the High Current experiment has increased our understanding of the beam quality limitations for these sources. We have also improved our techniques for fabricating large diameter aluminosilicate sources to improve lifetime and emission uniformity. For the multi-aperture approach we are continuing to study the feasibility of small surface sources and a RF induced plasma source in preparation for beamlet merging experiments, while continuing to run computer simulations for better understanding of this alternate concept. Experiments into both architectures will be performed on a newly commissioned ion source test stand at LLNL called the STS-500. This stand test provides a platform for testing a variety of ion sources and accelerating structures with 500 kV, 17-microsecond pulses. Recent progress in these areas will be discussed as well as plans for future experiments.

  18. Developing high brightness and high current beams for HIF injectors

    SciTech Connect

    Ahle, Larry; Grote, Dave; Kwan, Joe

    2002-05-24

    The US Heavy Ion Fusion Virtual National Laboratory is continuing research into ion sources and injectors that simultaneously provide high current (0.5-1.0 Amps) and high brightness (normalized emittance better than 1.0 {pi}-mm-mr). The central issue of focus is whether to continue pursuing the traditional approach of large surface ionization sources or to adopt a multiaperture approach that transports many smaller ''beamlets'' separately at low energies before allowing them to merge. For the large surface source concept, the recent commissioning of the 2-MeV injector for the High Current eXperiment has increased our understanding of the beam quality limitations for these sources. We have also improved our techniques for fabricating large diameter aluminosilicate sources to improve lifetime and emission uniformity. For the multiaperture approach, we are continuing to study the feasibility of small surface sources and a RF induced plasma source in preparation for beamlet merging experiments, while continuing to run computer simulations for better understanding of this alternate concept. Experiments into both architectures will be performed on a newly commissioned ion source test stand at LLNL called STS-500. This stand test provides a platform for testing a variety of ion sources and accelerating structures with 500 kV, 17-microsecond pulses. Recent progress in these areas will be discussed as well as plans for future experiments.

  19. Density functional investigation of mercury and arsenic adsorption on nitrogen doped graphene decorated with palladium clusters: A promising heavy metal sensing material in farmland

    NASA Astrophysics Data System (ADS)

    Zhao, Chunjiang; Wu, Huarui

    2017-03-01

    Density functional theory calculations are carried out to study the adsorption of mercury and arsenic on Pdn (n = 1-6) supported on pyridine-like nitrogen doped graphene (PNG). Owing to the promising sensitivity in trace amounts of atoms or molecules, PNG can be acted as micro-sensor for sensing heavy metals in agriculture soils. Through the analyses of structural and electronic properties of pristine PNG and Pd atom decorated PNG, we find that the most favorable adsorption site for Pd atom is the vacancy site. The analyses of structural and electronic properties reveal that the Pd atom or clusters can enhance the reactivity for Hg and AsH3 adsorption on PNG. The adsorption ability of Hg on Pdn decorated PNG is found to be related to the d-band center (εd) of the Pdn, in which the closer εd of Pdn to the Fermi level, the higher adsorption strength for Hg on Pdn decorated PNG. Moreover, the charge transfer between Pdn and arsenic may constitute arsenic adsorption on Pdn decorated PNG. Further design of highly efficient carbon based sorbents for heavy metals removal should be focused on tailoring εd of adsorbed metals.

  20. Characterizing the Interaction of Pt and PtRu Clusters with Boron-Doped, Nitrogen-Doped, and Activated Carbon: Density Functional Theory Calculations and Parameterization

    SciTech Connect

    Acharya, Chethan K.; Sullivan, Daniel I.; Turner, C. H.

    2008-09-04

    Previous density functional theory calculations of Pt and PtRu clusters on carbon supports have shown that the adsorption energies of these metal clusters increase substantially with substitutional boron defects in the carbon lattice. Here, the stability of metal clusters is further probed with substitutional nitrogen defects and surface functional groups. Also, the dynamics of Pt and Ru atoms on pure and boron-doped carbon are studied as a function of temperature using ab initio molecular dynamics (AIMD) simulations. Although the time scale accessible is limited, the AIMD simulations show reduced mobility on the boron-doped surface. In order to calculate additional dynamic properties of the systems, such as diffusion coefficients, the motion of the metal clusters should be studied for much longer periods of time, which can be accomplished by performing classical molecular dynamics (MD) simulations. Thus, we have parametrized our electronic structure calculations to an analytical Lennard-Jones (LJ) potential function, which will enable much longer time and length scales to be simulated in future investigations.

  1. [Effects of increased planting density with reduced nitrogen fertilizer application on rice yield, N use efficiency and greenhouse gas emission in Northeast China].

    PubMed

    Zhu, Xiang-cheng; Zhang, Zhen-ping; Zhang, Jun; Deng, Ai-xing; Zhang, Wei-jian

    2016-02-01

    The traditional rice growing practice has to change to save resource and protect environment, and it' s necessary to develop new technology in rice cultivation. Therefore, a two-year field experiment of Japonica rice (Liaoxing 1) was conducted in Northeast China in 2012 and 2013 to investigate the integrated effects of dense planting with less basal nitrogen (N) and unchanged top-dressing N (IR) on rice yield, N use efficiency (NUE) and greenhouse gas emissions. Compared with traditional practice (CK), we increased the rice seedling density by 33.3% and reduced the basal N rate by 20%. The results showed that the average N agronomy efficiency and partial factor productivity were improved by 49.6% (P<0.05) and 20.4% (P<0.05), respectively, while the area and yield-scaled greenhouse gas emissions were reduced by 9.9% and 12.7% (P<0.05), respectively. Although IR cropping mode decreased panicle number and biomass production, it significantly enhanced rice seed setting rate and harvest index, resulting in an unchanged or even highei yield. NH4+-N and NO3(-)-N concentrations in rice rhizosphere soil were reduced, resulting in an increment of N recovery efficiency. Generally, proper dense planting with less basal N applicatior could be a good approach for the trade-off between rice yield, NUE and greenhouse gas emission.

  2. High-Current-Density Thermionic Cathodes and the Generation of High-Voltage Electron Beams

    DTIC Science & Technology

    1989-04-30

    pulsing results, up to 140 kV was applied across this length of boron nitride without surface flashover . The anode face plate is made of stainless steel...current distribution over the cathode surface and correlation with thermionic-emission theory , 3. sign and testing of an electron-gun diode with an...aperture across the cathode surface by moving the anode transversely. The arrangement is shown in Figure 5. The sampled cathode current (0.16 percent of

  3. High-Current Density, High-Brightness Electron Beams from Large-Area Lanthanum Hexaboride Cathodes.

    DTIC Science & Technology

    1987-12-13

    Clarendon, Oxford, 1977), Chaps. 4.3-4.4. 15. Claude Lejeune and Jean Aubert, in Applied Charged Particle Optics, edited by A. Septier (Academic, New...Applications Intl. Corp. 1710 Goodridge Drive McLean, VA 22102 Dr. Charles C. Damm Lawrence Livermore National Laboratory P.O. Box 808 Livermore, CA 94550

  4. DARPA Advanced High Current Density Cathodes for Defense Applications: Development Phase

    DTIC Science & Technology

    1993-03-01

    Relevant approximations are applied to these exact solutions in order to extract the general thermodynamic properties without the need for the full...understanding that has been developed in terms of the properties of the advanced cathode materials, the fabrication and optimization processing, and the design...demonstrated that the parameters a and P3 are not constants, and that when a simple account of realistic material properties is included, the variation of a and

  5. High-current-density, high brightness cathodes for free electron laser applications

    SciTech Connect

    Green, M.C. . Palo Alto Microwave Tube Div.)

    1987-06-01

    This report discusses the following topics: brightness and emittance of electron beams and cathodes; general requirements for cathodes in high brightness electron guns; candidate cathode types; plasma and field emission cathodes; true field emission cathodes; oxide cathodes; lanthanum hexaborides cathodes; laser driven thermionic cathodes; laser driven photocathodes; impregnated porous tungsten dispenser cathodes; and choice of best performing cathode types.

  6. Relativistic performance analysis of a high current density magnetron injection gun

    SciTech Connect

    Barnett, L. R.; Luhmann, N. C. Jr.; Chiu, C. C.; Chu, K. R.

    2009-09-15

    Electron beam quality is essential to the performance of millimeter-wave gyroamplifiers, particularly the gyrotron traveling-wave tube amplifier, which is extremely sensitive to the electron velocity spread and emission uniformity. As one moves up in power and frequency, the quality of the electron beam becomes even more critical. One aspect of the electron beam formation technology which has received relatively little attention has been the performance analysis of the electron beam itself. In this study, a 100 kV, 8 A magnetron injection gun with a calculated perpendicular-to-parallel velocity ratio of 1.4 and axial velocity spread of 3.5% has been designed, tested, and analyzed. It is shown that the equipment precision and a fully relativistic data analysis model afford sufficient resolution to allow a verification of the theoretical predictions as well as a quantitative inference to the surface roughness of the cathode used.

  7. High Current Systems for HyperV and PLX Plasma Railguns

    NASA Astrophysics Data System (ADS)

    Brockington, S.; Case, A.; Messer, S.; Elton, R.; Witherspoon, F. D.

    2011-10-01

    HyperV is developing gas fed, pulsed, plasma railgun accelerators for PLX and other high momentum plasma applications. The present 2.5 cm square-bore plasma railgun forms plasma armatures from high density neutral gas (argon), preionizes it electrothermally, and accelerates the armature with 30 cm long parallel-plate railgun electrodes driven by a pulse forming network (PFN). Recent experiments have successfully formed and accelerated plasma armatures of ~4 mg at 40 km/s, with PFN currents of ~400 kA. In order to further increase railgun performance to the PLX design goal of 8 mg at 50 km/s, the PFN was upgraded to support currents of up to ~750 kA. A high voltage, high current linear array spark-gap switch and flexible, low-inductance transmission line were designed and constructed to handle the increased current load. We will describe these systems and present initial performance data from high current operation of the plasma rail gun from spectroscopy, interferometry, and imaging systems as well as pressure, magnetic field, and optical diagnostics. High current performance of railgun bore materials for electrodes and insulators will also be discussed as well as plans for upcoming experimentation with advanced materials. Supported by the U.S. DOE Joint Program in HEDLP.

  8. High pressure, high current, low inductance, high reliability sealed terminals

    DOEpatents

    Hsu, John S [Oak Ridge, TN; McKeever, John W [Oak Ridge, TN

    2010-03-23

    The invention is a terminal assembly having a casing with at least one delivery tapered-cone conductor and at least one return tapered-cone conductor routed there-through. The delivery and return tapered-cone conductors are electrically isolated from each other and positioned in the annuluses of ordered concentric cones at an off-normal angle. The tapered cone conductor service can be AC phase conductors and DC link conductors. The center core has at least one service conduit of gate signal leads, diagnostic signal wires, and refrigerant tubing routed there-through. A seal material is in direct contact with the casing inner surface, the tapered-cone conductors, and the service conduits thereby hermetically filling the interstitial space in the casing interior core and center core. The assembly provides simultaneous high-current, high-pressure, low-inductance, and high-reliability service.

  9. A High-Current, Stable Nonaqueous Organic Redox Flow Battery

    SciTech Connect

    Wei, Xiaoliang; Duan, Wentao; Huang, Jinhua; Zhang, Lu; Li, Bin; Reed, David; Xu, Wu; Sprenkle, Vincent; Wang, Wei

    2016-10-14

    Nonaqueous redox flow batteries are promising in pursuit of high-energy storage systems owing to the broad voltage window, but currently are facing key challenges such as poor cycling stability and lack of suitable membranes. Here we report a new nonaqueous all-organic flow chemistry that demonstrates an outstanding cell cycling stability primarily because of high chemical persistency of the organic radical redox species and their good compatibility with the supporting electrolyte. A feasibility study shows that Daramic® and Celgard® porous separators can lead to high cell conductivity in flow cells thus producing remarkable cell efficiency and material utilization even at high current operations. This result suggests that the thickness and pore size are the key performance-determining factors for porous separators. With the greatly improved flow cell performance, this new flow system largely addresses the above mentioned challenges and the findings may greatly expedite the development of durable nonaqueous flow batteries.

  10. Advanced electromagnetic design of cavities for high current accelerators

    SciTech Connect

    Krawczyk, F.L.

    1995-05-01

    For high-current accelerators such as those proposed for transmutation technologies or spallation sources, preconstruction numerical modeling has a high importance. Non axisymmetric cavities require a full 3-D modeling. A complex analysis of structures beyond tuning and the calculation of Q and shunt impedance is required and also the interaction with the mechanical properties of the structures has to be taken into account. This paper reports on recent work done at LANL for proposed beam funnels, a new normal-conducting medium-energy structure (CCDTL) and superconducting cavities for medium energy. The electromagnetic calculations have been done with MAFIA, Rel 3.2, the thermal and stress analysis results reported come from the ABAQUS engineering code.

  11. Survey of Digital Feedback Systems in High Current Storage Rings

    SciTech Connect

    Teytelman, Dmitry

    2003-06-06

    In the last decade demand for brightness in synchrotron light sources and luminosity in circular colliders led to construction of multiple high current storage rings. Many of these new machines require feedback systems to achieve design stored beam currents. In the same time frame the rapid advances in the technology of digital signal processing allowed the implementation of these complex feedback systems. In this paper I concentrate on three applications of feedback to storage rings: orbit control in light sources, coupled-bunch instability control, and low-level RF control. Each of these applications is challenging in areas of processing bandwidth, algorithm complexity, and control of time-varying beam and system dynamics. I will review existing implementations as well as comment on promising future directions.

  12. Interdigitated back contact solar cell with high-current collection

    NASA Astrophysics Data System (ADS)

    Garner, C. M.; Nasby, R. D.; Sexton, F. W.; Rodriguez, J. L.; Norwood, D. P.

    Internal current collection efficiencies greater than 90% and energy conversion efficiencies of 18 % at 30 suns were measured on a laboratory version of the interdigitated back contact (IBC) solar cell. A phosphorous gettering diffusion was performed on the front surface and then etched off to achieve these high current collection efficiencies. Thermal oxides were grown on the front and back of the cell to passivate the silicon surfaces. Although the internal collection efficiencies of the cell were high, series resistance caused the fill factor (FF) to decrease at concentrations above 30 suns. Dark current measurements on cells with a new grid spacing indicate that the series resistance is much lower than in the previous cell design. It is suggested that this should result in higher efficiencies at high concentration.

  13. Extremely High Current, High-Brightness Energy Recovery Linac

    SciTech Connect

    I. Ben-Zvi; D.S. Barton; D.B. Beavis; M. Blaskiewicz; J.M. Brennan; A. Burrill; R. Calaga; P. Cameron; X.Y. Chang; R. Connolly; D.M. Gassner; J.G. Grimes; H. Hahn; A. Hershcovitch; H.-C. Hseuh; P.D.J. Johnson; D. Kayran; J. Kewisch; R.F. Lambiase; V. Litvinenko; G.T. McIntyre; W. Meng; T.C.N. Nehring; T. Nicoletti; B. Oerter; D. Pate; J. Rank; T. Rao; T. Roser; T. Russo; J. Scaduto; Z. Segalov; K. Smith; N.W.W. Williams; K.-C. Wu; V. Yakimenko; K. Yip; A. Zaltsman; Y. Zhao; H. Bluem; A. Burger; M.D. Cole; A.J. Favale; D. Holmes; J. Rathke; T. Schultheiss; A.M.M. Todd; J.R. Delayen; L. W. Funk; P. Kneisel; H.L. Phillips; J.P. Preble

    2005-05-16

    Next generation ERL light-sources, high-energy electron coolers, high-power Free-Electron Lasers, powerful Compton X-ray sources and many other accelerators were made possible by the emerging technology of high-power, high-brightness electron beams. In order to get the anticipated performance level of ampere-class currents, many technological barriers are yet to be broken. BNL's Collider-Accelerator Department is pursuing some of these technologies for its electron cooling of RHIC application, as well as a possible future electron-hadron collider. We will describe work on CW, high-current and high-brightness electron beams. This will include a description of a superconducting, laser-photocathode RF gun and an accelerator cavity capable of producing low emittance (about 1 micron rms normalized) one nano-Coulomb bunches at currents of the order of one ampere average.

  14. Fast high-temperature superconductor switch for high current applications

    SciTech Connect

    Solovyov, VF; Li, Q

    2013-07-15

    Reversible operation of a high current superconductor switch based on the quench of high-resistance second generation high temperature superconducting wire is demonstrated. The quench is induced by a burst of an ac field generated by an inductively coupled radio-frequency coil. The switch makes a superconducting-to-normal transition within 5 ms and also has a rapid recovery to the superconducting state. The device has potential applications as an active current limiter or as a storage switch for superconducting magnetic energy storage systems. Operation in a full flux penetration/flow regime can effectively minimize the detrimental effects of the intrinsic conductor non-uniformity. (C) 2013 AIP Publishing LLC.

  15. New HOM coupler design for high current SRF cavity

    SciTech Connect

    Xu, W.; Ben-Zvi, I.; Belomestnykh, S.; Hahn, H.; Johnson, E.

    2011-03-28

    Damping higher order modes (HOMs) significantly to avoid beam instability is a challenge for the high current Energy Recovery Linac-based eRHIC at BNL. To avoid the overheating effect and high tuning sensitivity, current, a new band-stop HOM coupler is being designed at BNL. The new HOM coupler has a bandwidth of tens of MHz to reject the fundamental mode, which will avoid overheating due to fundamental frequency shifting because of cooling down. In addition, the S21 parameter of the band-pass filter is nearly flat from first higher order mode to 5 times the fundamental frequency. The simulation results showed that the new couplers effectively damp HOMs for the eRHIC cavity with enlarged beam tube diameter and 2 120{sup o} HOM couplers at each side of cavity. This paper presents the design of HOM coupler, HOM damping capacity for eRHIC cavity and prototype test results.

  16. High current beam transport with multiple beam arrays

    SciTech Connect

    Kim, C.H.

    1985-05-01

    Highlights of recent experimental and theoretical research progress on the high current beam transport of single and multiple beams by the Heavy Ion Fusion Accelerator Research (HIFAR) group at the Lawrence Berkeley Laboratory (LBL) are presented. In the single beam transport experiment (SBTE), stability boundaries and the emittance growth of a space charge dominated beam in a long quadrupole transport channel were measured and compared with theory and computer simulations. Also, a multiple beam ion induction linac (MBE-4) is being constructed at LBL which will permit study of multiple beam transport arrays, and acceleration and bunch length compression of individually focused beamlets. Various design considerations of MBE-4 regarding scaling laws, nonlinear effects, misalignments, and transverse and longitudinal space charge effects are summarized. Some aspects of longitudinal beam dynamics including schemes to generate the accelerating voltage waveforms and to amplify beam current are also discussed.

  17. PENETRATION AND DEFECT FORMATION IN HIGH CURRENT ARC WELDING

    SciTech Connect

    MENDEZ,P.F.; EAGAR, T.W.

    2003-01-01

    The work performed during the three previous years can be roughly divided into two main categories: (1) development of advanced modeling techniques; and (2) modeling of arc welding process. The work in the first category comprised the development of the Order of Magnitude Scaling (OMS) technique, which is complementary to numerical modeling techniques such as finite elements, but it provides approximate formulas instead of just numerical results. Borrowing concepts from OMS, another modeling technique based on empirical data was also developed. During this stage special software was also developed. The second category comprised the application of OMS to the three main subsystems of arc welding: the weld pool, the arc, and the electrode. For each of these subsystems they found scaling laws and regimes. With this knowledge, they analyzed the generation of weld pool defects during high current arc welding, proposed a mechanistic description of the process, and possible solutions.

  18. Heavy-Ion Injector for the High Current Experiment

    NASA Astrophysics Data System (ADS)

    Bieniosek, F. M.; Henestroza, E.; Kwan, J. W.; Prost, L.; Seidl, P.

    2001-10-01

    We report on progress in development of the Heavy-Ion Injector at LBNL, which is being prepared for use as an injector for the High Current Experiment (HCX). It is composed of a 10-cm-diameter surface ionization source, an extraction diode, and an electrostatic quadrupole (ESQ) accelerator, with a typical operating current of 0.6 A of potassium ions at 1.8 MeV, and a beam pulse length of 4.5 microsecs. We have improved the Injector equipment and diagnostics, and have characterized the source emission and radial beam profiles at the diode and ESQ regions. We find improved agreement with EGUN predictions, and improved compatibility with the downstream matching section. Plans are to attach the matching section and the initial ESQ transport section of HCX. Results will be presented and compared with EGUN and WARP simulations.

  19. Nitrogen segregation in nanocarbons.

    PubMed

    Ewels, C P; Erbahar, D; Wagner, Ph; Rocquefelte, X; Arenal, R; Pochet, P; Rayson, M; Scardamaglia, M; Bittencourt, C; Briddon, P

    2014-01-01

    We explore the behaviour of nitrogen doping in carbon nanomaterials, notably graphene, nanotubes, and carbon thin films. This is initially via a brief review of the literature, followed by a series of atomistic density functional calculations. We show that at low concentrations, substitutional nitrogen doping in the sp(2)-C graphenic basal plane is favoured, however once the nitrogen concentration reaches a critical threshold there is a transition towards the formation of the more thermodynamically-favoured nitrogen terminated 'zigzag' type edges. These can occur either via formation of finite patches (polycyclic aromatic azacarbons), strips of sp(2) carbon with zigzag nitrogen edges, or internal nitrogen-terminated hole edges within graphenic planes. This transition to edge formation is especially favoured when the nitrogen can be partially functionalised with, e.g. hydrogen. By comparison with available literature results, notably from electron energy loss spectroscopy and X-ray spectroscopy, the current results suggest that much of the nitrogen believed to be incorporated into carbon nanoobjects is instead likely to be present terminating the edges of carbonaceous impurities attached to nanoobject's surface. By comparison to nitrogen-doped tetrahedrally amorphous carbon, we suggest that this transition at around 10-20% nitrogen concentration and above towards sp(2) coordination via internal nitrogen-terminated edge formation may be a general property of nitrogen-doped carbon materials.

  20. Superior Cathode Performance of Nitrogen-Doped Graphene Frameworks for Lithium Ion Batteries.

    PubMed

    Xiong, Dongbin; Li, Xifei; Bai, Zhimin; Shan, Hui; Fan, Linlin; Wu, Chunxia; Li, Dejun; Lu, Shigang

    2017-03-14

    Development of alternative cathode materials is of highly desirable for sustainable and cost-efficient lithium-ion batteries (LIBs) in energy storage fields. In this study, for the first time, we report tunable nitrogen-doped graphene with active functional groups for cathode utilization of LIBs. When employed as cathode materials, the functionalized graphene frameworks with a nitrogen content of 9.26 at% retain a reversible capacity of 344 mAh g(-1) after 200 cycles at a current density of 50 mA g(-1). More surprisingly, when conducted at a high current density of 1 A g(-1), this cathode delivers a high reversible capacity of 146 mAh g(-1) after 1000 cycles. Our current research demonstrates the effective significance of nitrogen doping on enhancing cathode performance of functionalized graphene for LIBs.

  1. Gyrotron-driven high current ECR ion source for boron-neutron capture therapy neutron generator

    NASA Astrophysics Data System (ADS)

    Skalyga, V.; Izotov, I.; Golubev, S.; Razin, S.; Sidorov, A.; Maslennikova, A.; Volovecky, A.; Kalvas, T.; Koivisto, H.; Tarvainen, O.

    2014-12-01

    Boron-neutron capture therapy (BNCT) is a perspective treatment method for radiation resistant tumors. Unfortunately its development is strongly held back by a several physical and medical problems. Neutron sources for BNCT currently are limited to nuclear reactors and accelerators. For wide spread of BNCT investigations more compact and cheap neutron source would be much more preferable. In present paper an approach for compact D-D neutron generator creation based on a high current ECR ion source is suggested. Results on dense proton beams production are presented. A possibility of ion beams formation with current density up to 600 mA/cm2 is demonstrated. Estimations based on obtained experimental results show that neutron target bombarded by such deuteron beams would theoretically yield a neutron flux density up to 6·1010 cm-2/s. Thus, neutron generator based on a high-current deuteron ECR source with a powerful plasma heating by gyrotron radiation could fulfill the BNCT requirements significantly lower price, smaller size and ease of operation in comparison with existing reactors and accelerators.

  2. Maize Varieties Released in Different Eras Have Similar Root Length Density Distributions in the Soil, Which Are Negatively Correlated with Local Concentrations of Soil Mineral Nitrogen

    PubMed Central

    Ning, Peng; Li, Sa; White, Philip J.; Li, Chunjian

    2015-01-01

    Larger, and deeper, root systems of new maize varieties, compared to older varieties, are thought to have enabled improved acquisition of soil resources and, consequently, greater grain yields. To compare the spatial distributions of the root systems of new and old maize varieties and their relationships with spatial variations in soil concentrations of available nitrogen (N), phosphorus (P) and potassium (K), two years of field experiments were performed using six Chinese maize varieties released in different eras. Vertical distributions of roots, and available N, P and K in the 0–60 cm soil profile were determined in excavated soil monoliths at silking and maturity. The results demonstrated that new maize varieties had larger root dry weight, higher grain yield and greater nutrient accumulation than older varieties. All varieties had similar total root length and vertical root distribution at silking, but newer varieties maintained greater total root length and had more roots in the 30–60 cm soil layers at maturity. The spatial variation of soil mineral N (Nmin) in each soil horizon was larger than that of Olsen-P and ammonium-acetate-extractable K, and was inversely correlated with root length density (RLD), especially in the 0–20 cm soil layer. It was concluded that greater acquisition of mineral nutrients and higher yields of newer varieties were associated with greater total root length at maturity. The negative relationship between RLD and soil Nmin at harvest for all varieties suggests the importance of the spatial distribution of the root system for N uptake by maize. PMID:25799291

  3. A conceptual model of the controlling factors of soil organic carbon and nitrogen densities in a permafrost-affected region on the eastern Qinghai-Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Wu, Xiaodong; Fang, Hongbing; Zhao, Yonghua; Smoak, Joseph M.; Li, Wangping; Shi, Wei; Sheng, Yu; Zhao, Lin; Ding, Yongjian

    2017-07-01

    Many investigations of the preservation of soil organic carbon (SOC) in permafrost regions have examined roles of geomorphology, pedogenesis, vegetation cover, and permafrost within particular regions. However, it is difficult to disentangle the effects of multiple factors on the SOC in permafrost regions due to the heterogeneity in environmental conditions. Based on data from 73 soil study sites in permafrost regions of the eastern Qinghai-Tibetan Plateau, we developed a simple conceptual model, which relates SOC to topography, vegetation, and pedogenesis. We summarized the dominant factors and their controls on SOC using 31 measured soil physiochemical variables. Soil texture explains approximately 60% of the variations in the SOC stocks for the upper 0-2 m soil. Soil particle size closely correlates to soil moisture, which is an important determinant of SOC. Soil salinity and cations are important factors as well and can explain about 10% of the variations in SOC. The SOC and total nitrogen (TN) stocks for the 1-2 m depths have larger uncertainties than those of upper 1 m soil layer. The vegetation, pH, and bulk density mainly affects SOC and TN stocks for the upper 1 m soil layers, while the active layer thickness and soil particle size have greater influence on SOC and TN stocks for the 1-2 m soils. Our results suggest that the soil particle size is the most important controller of SOC pools, and the stocks of SOC and TN are strongly effected by soil development processes in the permafrost regions of the eastern Qinghai-Tibetan Plateau.

  4. Maize varieties released in different eras have similar root length density distributions in the soil, which are negatively correlated with local concentrations of soil mineral nitrogen.

    PubMed

    Ning, Peng; Li, Sa; White, Philip J; Li, Chunjian

    2015-01-01

    Larger, and deeper, root systems of new maize varieties, compared to older varieties, are thought to have enabled improved acquisition of soil resources and, consequently, greater grain yields. To compare the spatial distributions of the root systems of new and old maize varieties and their relationships with spatial variations in soil concentrations of available nitrogen (N), phosphorus (P) and potassium (K), two years of field experiments were performed using six Chinese maize varieties released in different eras. Vertical distributions of roots, and available N, P and K in the 0-60 cm soil profile were determined in excavated soil monoliths at silking and maturity. The results demonstrated that new maize varieties had larger root dry weight, higher grain yield and greater nutrient accumulation than older varieties. All varieties had similar total root length and vertical root distribution at silking, but newer varieties maintained greater total root length and had more roots in the 30-60 cm soil layers at maturity. The spatial variation of soil mineral N (Nmin) in each soil horizon was larger than that of Olsen-P and ammonium-acetate-extractable K, and was inversely correlated with root length density (RLD), especially in the 0-20 cm soil layer. It was concluded that greater acquisition of mineral nutrients and higher yields of newer varieties were associated with greater total root length at maturity. The negative relationship between RLD and soil Nmin at harvest for all varieties suggests the importance of the spatial distribution of the root system for N uptake by maize.

  5. Economic values of growth and feed efficiency for fish farming in recirculating aquaculture system with density and nitrogen output limitations: a case study with African catfish (Clarias gariepinus).

    PubMed

    Besson, M; Komen, H; Aubin, J; de Boer, I J M; Poelman, M; Quillet, E; Vancoillie, C; Vandeputte, M; van Arendonk, J A M

    2014-12-01

    In fish farming, economic values (EV) of breeding goal traits are lacking, even though they are key parameters when defining selection objectives. The aim of this study was to develop a bioeconomic model to estimate EV of 2 traits representing production performances in fish farming: the thermal growth coefficient (TGC) and the feed conversion ratio (FCR). This approach was applied to a farm producing African catfish (Clarias gariepinus) in a recirculating aquaculture system (RAS). In the RAS, 2 factors could limit production level: the nitrogen treatment capacity of the biofilter or the fish density in rearing tanks at harvest. Profit calculation includes revenue from fish sales, cost of juveniles, cost of feed, cost of waste water treatment, and fixed costs. In the reference scenario, profit was modeled to zero. EV were calculated as the difference in profit per kilogram of fish between the current population mean for both traits (µt) and the next generation of selective breeding (µt+Δt) for either TGC or FCR. EV of TGC and FCR were calculated for three generations of hypothetical selection on either TGC or FCR (respectively 6.8% and 7.6% improvement per generation). The results show that changes in TGC and FCR can affect both the number of fish that can be stocked (number of batches per year and number of fish per batch) and the factor limiting production. The EV of TGC and FCR vary and depend on the limiting factors. When dissolved NH3-N is the limiting factor for both µt and µt+Δt, increasing TGC decreases the number of fish that can be stocked but increases the number of batches that can be grown. As a result, profit remains constant and EVTGC is zero. Increasing FCR, however, increases the number of fish stocked and the ratio of fish produced per kilogram of feed consumed ("economic efficiency"). The EVFCR is 0.14 €/kg of fish, and profit per kilogram of fish increases by about 10%. When density is the limiting factor for both µt and µt+Δt, the

  6. High average power, high current pulsed accelerator technology

    SciTech Connect

    Neau, E.L.

    1995-05-01

    Which current pulsed accelerator technology was developed during the late 60`s through the late 80`s to satisfy the needs of various military related applications such as effects simulators, particle beam devices, free electron lasers, and as drivers for Inertial Confinement Fusion devices. The emphasis in these devices is to achieve very high peak power levels, with pulse lengths on the order of a few 10`s of nanoseconds, peak currents of up to 10`s of MA, and accelerating potentials of up to 10`s of MV. New which average power systems, incorporating thermal management techniques, are enabling the potential use of high peak power technology in a number of diverse industrial application areas such as materials processing, food processing, stack gas cleanup, and the destruction of organic contaminants. These systems employ semiconductor and saturable magnetic switches to achieve short pulse durations that can then be added to efficiently give MV accelerating, potentials while delivering average power levels of a few 100`s of kilowatts to perhaps many megawatts. The Repetitive High Energy Puled Power project is developing short-pulse, high current accelerator technology capable of generating beams with kJ`s of energy per pulse delivered to areas of 1000 cm{sup 2} or more using ions, electrons, or x-rays. Modular technology is employed to meet the needs of a variety of applications requiring from 100`s of kV to MV`s and from 10`s to 100`s of kA. Modest repetition rates, up to a few 100`s of pulses per second (PPS), allow these machines to deliver average currents on the order of a few 100`s of mA. The design and operation of the second generation 300 kW RHEPP-II machine, now being brought on-line to operate at 2.5 MV, 25 kA, and 100 PPS will be described in detail as one example of the new high average power, high current pulsed accelerator technology.

  7. A neutron diagnostic for high current deuterium beams

    SciTech Connect

    Rebai, M.; Perelli Cippo, E.; Cavenago, M.; Dalla Palma, M.; Pasqualotto, R.; Tollin, M.; Croci, G.; Gervasini, G.; Ghezzi, F.; Grosso, G.; Tardocchi, M.; Murtas, F.; Gorini, G.

    2012-02-15

    A neutron diagnostic for high current deuterium beams is proposed for installation on the spectral shear interferometry for direct electric field reconstruction (SPIDER, Source for Production of Ion of Deuterium Extracted from RF plasma) test beam facility. The proposed detection system is called Close-contact Neutron Emission Surface Mapping (CNESM). The diagnostic aims at providing the map of the neutron emission on the beam dump surface by placing a detector in close contact, right behind the dump. CNESM uses gas electron multiplier detectors equipped with a cathode that also serves as neutron-proton converter foil. The cathode is made of a thin polythene film and an aluminium film; it is designed for detection of neutrons of energy >2.2 MeV with an incidence angle < 45 deg. CNESM was designed on the basis of simulations of the different steps from the deuteron beam interaction with the beam dump to the neutron detection in the nGEM. Neutron scattering was simulated with the MCNPX code. CNESM on SPIDER is a first step towards the application of this diagnostic technique to the MITICA beam test facility, where it will be used to resolve the horizontal profile of the beam intensity.

  8. High current rf (HCRF) linac program. Final report

    SciTech Connect

    Not Available

    1992-11-01

    The High Current Radio Frequency (HCRF) Accelerator program began as an effort funded by the Strategic Defense Initiative Office (SDIO) through the Office of Naval Research (ONR). The three options carried a negotiated total of $3,731,115 so that the total negotiated amount was $3,950,340. SDIO only provided $600,000 for the effort, and only one of the three options was exercised. An additional $310,000 was provided by DARPA, the Office of Naval Technology (ONT) and the Naval Ocean System Center (NOSC) for a collaborative effort to explore an RF technology application in naval surveillance (ultra-wideband radar), an activity covered by the HCRF statement of work. Technical work on the HCRF program consisted of in-depth technology studies and experimental support on the naval radar task. The overall goal of the HCRF program was to develop an fundamentally new technology for compact (high gradient) electron accelerators that can efficiently drive high gain, single pass FEL amplifiers producing output radiation at a wavelength of approximately one micron or less in a pulsed format for boost phase and mid-course SDIO missions. SDIO mission requirements dictated that the accelerator technology goals be consistent with a laser system that can produce greater than ten megawatts of average optical power during a 200 second battle from a space platform placed in orbit with a single heavy lift booster.

  9. Some Physical and Engineering Aspects of High Current EBIS

    SciTech Connect

    Pikin, A; Prelec, K.

    1999-05-21

    Some applications of an Electron Beam Ion Source (EBIS) require intensities of highly charged ions significantly greater than those which have been achieved in present EBIS sources. For example, the ion source for the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) must be capable of generating 3 x 10{sup 9} ions of Au{sup 35+} or 2 x 10{sup 9} ions of U{sup 45+} per pulse. In this case, if the fraction of ions of interest is 20% of the total ion space charge, the total extracted charge is {approximately} 5 x 10{sup 11}. It is also desirable to extract these ions in a 10 {micro}s pulse to allow single turn injection into the first synchrotrons. Requirements for an EBIS which could meet the needs of the LHC at CERN are similar ({approximately} 1.5 x 10{sup 9} ions of Pb{sup 54+} in 5.5 {micro}s). This charge yield is about an order of magnitude greater than that achieved in existing EBIS sources, and is what is meant here by high current. This also implies, then, an EBIS with a high electron beam current.

  10. A high current, short pulse electron source for wakefield accelerators

    SciTech Connect

    Ho, Ching-Hung

    1992-12-31

    Design studies for the generation of a high current, short pulse electron source for the Argonne Wakefield Accelerator are presented. An L-band laser photocathode rf gun cavity is designed using the computer code URMEL to maximize the electric field on the cathode surface for fixed frequency and rf input power. A new technique using a curved incoming laser wavefront to minimize the space charge effect near the photocathode is studied. A preaccelerator with large iris to minimize wakefield effects is used to boost the drive beam to a useful energy of around 20 MeV for wakefield acceleration experiments. Focusing in the photocathode gun and the preaccelerator is accomplished with solenoids. Beam dynamics simulations throughout the preaccelerator are performed using particle simulation codes TBCI-SF and PARMELA. An example providing a useful set of operation parameters for the Argonne Wakefield Accelerator is given. The effects of the sagitta of the curved beam and laser amplitude and timing jitter effects are discussed. Measurement results of low rf power level bench tests and a high power test for the gun cavity are presented and discussed.

  11. Mevva development for the new GSI high-current injector

    SciTech Connect

    Wolf, B.H.; Emig, H.; Spaedtke, P.

    1996-08-01

    To increase the intensity of the heavy ion synchrotron SIS for heavy elements by a factor of {approximately}50, a new prestripper accelerator is planned for Unilac and the heavy ion synchrotron SIS. It is designed to accept ions with mass/charge {le} 65 and an injection energy of 2.2 keV/u. A vacuum arc ion source with a strong axial magnetic field will deliver 15 mA of U{sup 4+} as heaviest element at a repetition rate of 1 Hz and a pulse length of 300 {mu}s. The investigation of the Mevva ion source with pulsed magnetic field of several kGauss have shown that ion currents of 8 mA U{sup 4+} can be measured at the authors test bench after 5m of transport and charge analysis (transmission at the test bench 25% only). The noise on the extracted ion beam was already {le}25%, a value similar to the Pig ion source in the sputter mode, but efficient high current beam transport probably requests further improvements.

  12. A Superconducting transformer system for high current cable testing

    SciTech Connect

    Godeke, A.; Dietderich, D. R.; Joseph, J. M.; Lizarazo, J.; Prestemon, S. O.; Miller, G.; Weijers, H. W.

    2010-02-15

    This article describes the development of a direct-current (dc) superconducting transformer system for the high current test of superconducting cables. The transformer consists of a core-free 10 464 turn primary solenoid which is enclosed by a 6.5 turn secondary. The transformer is designed to deliver a 50 kA dc secondary current at a dc primary current of about 50 A. The secondary current is measured inductively using two toroidal-wound Rogowski coils. The Rogowski coil signal is digitally integrated, resulting in a voltage signal that is proportional to the secondary current. This voltage signal is used to control the secondary current using a feedback loop which automatically compensates for resistive losses in the splices to the superconducting cable samples that are connected to the secondary. The system has been commissioned up to 28 kA secondary current. The reproducibility in the secondary current measurement is better than 0.05% for the relevant current range up to 25 kA. The drift in the secondary current, which results from drift in the digital integrator, is estimated to be below 0.5 A/min. The system's performance is further demonstrated through a voltage-current measurement on a superconducting cable sample at 11 T background magnetic field. The superconducting transformer system enables fast, high resolution, economic, and safe tests of the critical current of superconducting cable samples.

  13. A superconducting transformer system for high current cable testing.

    PubMed

    Godeke, A; Dietderich, D R; Joseph, J M; Lizarazo, J; Prestemon, S O; Miller, G; Weijers, H W

    2010-03-01

    This article describes the development of a direct-current (dc) superconducting transformer system for the high current test of superconducting cables. The transformer consists of a core-free 10,464 turn primary solenoid which is enclosed by a 6.5 turn secondary. The transformer is designed to deliver a 50 kA dc secondary current at a dc primary current of about 50 A. The secondary current is measured inductively using two toroidal-wound Rogowski coils. The Rogowski coil signal is digitally integrated, resulting in a voltage signal that is proportional to the secondary current. This voltage signal is used to control the secondary current using a feedback loop which automatically compensates for resistive losses in the splices to the superconducting cable samples that are connected to the secondary. The system has been commissioned up to 28 kA secondary current. The reproducibility in the secondary current measurement is better than 0.05% for the relevant current range up to 25 kA. The drift in the secondary current, which results from drift in the digital integrator, is estimated to be below 0.5 A/min. The system's performance is further demonstrated through a voltage-current measurement on a superconducting cable sample at 11 T background magnetic field. The superconducting transformer system enables fast, high resolution, economic, and safe tests of the critical current of superconducting cable samples.

  14. High-Current Energy-Recovering Electron Linacs

    SciTech Connect

    Nikolitsa Merminga; David Douglas; Geoffrey Krafft

    2003-12-01

    The use of energy recovery provides a potentially powerful new paradigm for generation of the charged particle beams used in synchrotron radiation sources, high-energy electron cooling devices, electron-ion colliders, and other applications in photon science and nuclear and high-energy physics. Energy-recovering electron linear accelerators (called energy-recovering linacs, or ERLs) share many characteristics with ordinary linacs, as their six-dimensional beam phase space is largely determined by electron source properties. However, in common with classic storage rings, ERLs possess a high average-current-carrying capability enabled by the energy recovery process, and thus promise similar efficiencies. The authors discuss the concept of energy recovery and its technical challenges and describe the Jefferson Lab (JLab) Infrared Demonstration Free-Electron Laser (IR Demo FEL), originally driven by a 3548-MeV, 5-mA superconducting radiofrequency (srf) ERL, which provided the most substantial demonstration of energy recovery to date: a beam of 250 kW average power. They present an overview of envisioned ERL applications and a development path to achieving the required performance. They use experimental data obtained at the JLab IR Demo FEL and recent experimental results from CEBAF-ERL GeV-scale, comparatively low-current energy-recovery demonstration at JLab to evaluate the feasibility of the new applications of high-current ERLs, as well as ERLs' limitations and ultimate performance.

  15. High Current Cathodes Fabricated by KrF Laser Ablation

    SciTech Connect

    Gilgenbach, Ronald M.; Lau, Y. Y.; Jones, M. C.; Johnston, M. D.; Jordan, N. M.; Hoff, B. W.

    2010-10-08

    In this paper we review several high power laser ablation techniques that have been utilized to fabricate high current (1-80 kA) electron beam cathodes for accelerators and microwave sources: 1) Projection Ablation Lithography (PAL) cathodes, 2) Ablation Line Focus (ALF) cathodes, and 3) Metal-Oxide-Junction (MOJ) cathodes. Laser-ablative micromachining techniques (PAL and ALF) have been utilized to generate micron-scale features on metal substrates that provide electric field (beta) enhancement for Fowler-Nordheim emission and plasma cathodes. Since these laser-ablated patterns are directly, laser-written on the substrate metal they exhibit much higher thermal conductivity for higher current capability and increased damage thresholds. Metal-Oxide-Junction (MOJ) cathodes exploit the triple-point electron emission that occurs at the interface between metal, insulator and vacuum.The ablation laser is a KrF excimer laser with a pulse energy of 600 mJ and pulselength of 20 ns. Cathode experiments were performed on the MELBA-C accelerator: V = -300 kV, pulselength = 0.5 microsecond. Data will be presented for PAL, ALF and MOJ cathodes.

  16. Anode jet in a high-current vacuum arc

    NASA Astrophysics Data System (ADS)

    Popov, S. A.; Schneider, A. V.; Batrakov, A. V.; Sandolache, G.; Rowe, S. W.; Markov, A. B.; Zyul'kova, L. A.

    2012-07-01

    A stable intense jet with a clear-cut bright sheath has been detected on the anode of a 10-ms-long high-current vacuum arc with a current amplitude of 15 kA. The jet is adjacent to the hot spot of a molten metal on the anode surface. The primary light of the jet is emitted by neutrals. The sheath of the jet is surrounded by an ion-induced diffuse glow. The anode jet arises from interaction between the cathode and anode plasmas. Because of this, the size of the jet inversely depends on the current of the arc and the jet becomes observable only by the end of the current pulse. This object (anode jet with a bright sheath) is well reproducible when the arc is initiated between copper-chromium electrodes. In the case of pure copper electrodes, such objects occur randomly and appear at long projections of the molten metal, where heat release is hampered, and at large drops moving in the interelectrode gap. This means that the anode evaporation intensity is crucial for the appearance of bright-sheath jets.

  17. The MEVVA ion source for high current metal ion implantation

    NASA Astrophysics Data System (ADS)

    Brown, Ian; Washburn, Jack

    The MEVVA (Metal Vapor Vacuum Arc) ion source is a new kind of source which can produce high current beams of metal ions. Beams of a wide range of elements have been produced, spanning the periodic table from lithium up to and including uranium. The source extraction voltage is up to 60 kV, and we are increasing this up to 120 kV. A total ion beam current of over 1 A has been extracted from the present embodiment of the concept, and this is not an inherent limit. The ion charge state distribution varies with cathode material and are current, and beams like Li +, Co +.2+.3+ and U 3+.4+.5+.6+ for example, are typical; thus the implantation energy can be up to several hundred kV without additional acceleration. The ion source has potential applications for ion implantation and ion beam mixing for achievement of improved corrosion resistance or wear resistance in metals or surface modification of ceramic materials and semiconductors. Here we outline the source and its performance, and describe some very preliminary implantation work using this source.

  18. Los Alamos high-current proton storage ring

    NASA Astrophysics Data System (ADS)

    Lawrence, G. P.; Hardekopf, R. A.; Jason, A. J.; Clout, P. N.; Sawyer, G. A.

    1985-05-01

    The Proton Storage Ring (PSR), whose installation was recently completed at Los Alamos, is a fast-cycling high-current accumulator designed to produce intense 800 MeV proton pulses for driving a spallation neutron source. The ring converts long beam pulses from the LAMPF linear accelerator into short bunches well matched to requirements of a high-resolution neutron-scattering materials science program. The initial performance goal for this program is to provide 100-(MU)A average current at the neutron production target within a 12-Hz pulse rate. Operation at 20 (MU)A is scheduled for September 1985, with full intensity within the next year. The storage ring was originally designed to function in a second mode in which six 1-ns bunches are accumulated and separately extracted every LAMPF macropulse. Implementation of this mode, which would serve a fast-neutron nuclear-physics program, was deferred in favor of initial concentration on the neutron-scattering program. The PSR design and status is summarized. Unique machine features include high peak current, two-step charge-stripping injection, a low-impedance buncher amplifier to counter beam-loading, and a high-repetition-rate strip-line extraction kicker.

  19. Characterization of a High Current, Long Life Hollow Cathode

    NASA Technical Reports Server (NTRS)

    VanNoord, Jonathan L.; Kamhawi, Hani; McEwen, Heather K.

    2006-01-01

    The advent of higher power spacecraft makes it desirable to use higher power electric propulsion thrusters such as ion thrusters or Hall thrusters. Higher power thrusters require cathodes that are capable of producing higher currents. One application of these higher power spacecraft is deep-space missions that require tens of thousands of hours of operation. This paper presents the approach used to design a high current, long life hollow cathode assembly for that application, along with test results from the corresponding hollow cathode. The design approach used for the candidate hollow cathode was to reduce the temperature gradient in the insert, yielding a lower peak temperature and allowing current to be produced more uniformly along the insert. The lower temperatures result in a hollow cathode with increased life. The hollow cathode designed was successfully operated at currents from 10 to 60 A with flow rates of 5 to 19 sccm with a maximum orifice temperature measured of 1100 C. Data including discharge voltage, keeper voltage, discharge current, flow rates, and orifice plate temperatures are presented.

  20. A high current, short pulse electron source for wakefield accelerators

    SciTech Connect

    Ho, Ching-Hung.

    1992-01-01

    Design studies for the generation of a high current, short pulse electron source for the Argonne Wakefield Accelerator are presented. An L-band laser photocathode rf gun cavity is designed using the computer code URMEL to maximize the electric field on the cathode surface for fixed frequency and rf input power. A new technique using a curved incoming laser wavefront to minimize the space charge effect near the photocathode is studied. A preaccelerator with large iris to minimize wakefield effects is used to boost the drive beam to a useful energy of around 20 MeV for wakefield acceleration experiments. Focusing in the photocathode gun and the preaccelerator is accomplished with solenoids. Beam dynamics simulations throughout the preaccelerator are performed using particle simulation codes TBCI-SF and PARMELA. An example providing a useful set of operation parameters for the Argonne Wakefield Accelerator is given. The effects of the sagitta of the curved beam and laser amplitude and timing jitter effects are discussed. Measurement results of low rf power level bench tests and a high power test for the gun cavity are presented and discussed.

  1. Robust, easily shaped, and epoxy-free carbon-fiber-aluminum cathodes for generating high-current electron beams

    NASA Astrophysics Data System (ADS)

    Liu, Lie; Li, Limin; Wen, Jianchun; Wan, Hong

    2009-02-01

    This paper presents the construction of carbon-fiber-aluminum (CFA) cathode by squeezing casting and its applications for generating high-current electron beams to drive high-power microwave sources. The fabrication process avoided using epoxy, a volatile deteriorating the vacuum system. These cathodes had a higher hardness than conventional aluminum, facilitating machining. After surface treatment, carbon fibers became the dominator determining emission property. A multineedle CFA cathode was utilized in a triode virtual cathode oscillator (vircator), powered by a ˜450 kV, ˜400 ns pulse. It was found that 300-400 MW, ˜250 ns microwave was radiated at a dominant frequency of 2.6 GHz. Further, this cathode can endure high-current-density emission without detectable degradation in performance as the pulse shot proceeded, showing the robust nature of carbon fibers as explosive emitters. Overall, this new class of cold cathodes offers a potential prospect of developing high-current electron beam sources.

  2. Robust, easily shaped, and epoxy-free carbon-fiber-aluminum cathodes for generating high-current electron beams.

    PubMed

    Liu, Lie; Li, Limin; Wen, Jianchun; Wan, Hong

    2009-02-01

    This paper presents the construction of carbon-fiber-aluminum (CFA) cathode by squeezing casting and its applications for generating high-current electron beams to drive high-power microwave sources. The fabrication process avoided using epoxy, a volatile deteriorating the vacuum system. These cathodes had a higher hardness than conventional aluminum, facilitating machining. After surface treatment, carbon fibers became the dominator determining emission property. A multineedle CFA cathode was utilized in a triode virtual cathode oscillator (vircator), powered by a approximately 450 kV, approximately 400 ns pulse. It was found that 300-400 MW, approximately 250 ns microwave was radiated at a dominant frequency of 2.6 GHz. Further, this cathode can endure high-current-density emission without detectable degradation in performance as the pulse shot proceeded, showing the robust nature of carbon fibers as explosive emitters. Overall, this new class of cold cathodes offers a potential prospect of developing high-current electron beam sources.

  3. Neutron generator for BNCT based on high current ECR ion source with gyrotron plasma heating.

    PubMed

    Skalyga, V; Izotov, I; Golubev, S; Razin, S; Sidorov, A; Maslennikova, A; Volovecky, A; Kalvas, T; Koivisto, H; Tarvainen, O

    2015-12-01

    BNCT development nowadays is constrained by a progress in neutron sources design. Creation of a cheap and compact intense neutron source would significantly simplify trial treatments avoiding use of expensive and complicated nuclear reactors and accelerators. D-D or D-T neutron generator is one of alternative types of such sources for. A so-called high current quasi-gasdynamic ECR ion source with plasma heating by millimeter wave gyrotron radiation is suggested to be used in a scheme of D-D neutron generator in the present work. Ion source of that type was developed in the Institute of Applied Physics of Russian Academy of Sciences (Nizhny Novgorod, Russia). It can produce deuteron ion beams with current density up to 700-800 mA/cm(2). Generation of the neutron flux with density at the level of 7-8·10(10) s(-1) cm(-2) at the target surface could be obtained in case of TiD2 target bombardment with deuteron beam accelerated to 100 keV. Estimations show that it is enough for formation of epithermal neutron flux with density higher than 10(9) s(-1) cm(-2) suitable for BNCT. Important advantage of described approach is absence of Tritium in the scheme. First experiments performed in pulsed regime with 300 mA, 45 kV deuteron beam directed to D2O target demonstrated 10(9) s(-1) neutron flux. This value corresponds to theoretical estimations and proofs prospects of neutron generator development based on high current quasi-gasdynamic ECR ion source. Copyright © 2015 Elsevier Ltd. All rights reserved.

  4. HIGH-CURRENT COLD CATHODE FIELD EMISSION ARRAY FOR ELECTRON LENS APPLICATION

    SciTech Connect

    Hirshfield, Jay L

    2012-12-28

    During Phase I, the following goals were achieved: (1) design and fabrication of a novel, nano-dimensional CNT field emitter assembly for high current density application, with high durability; (2) fabrication of a ceramic based micro channel plate (MCP) and characterization of its secondary electron emission; and (3) characterizing the CNT/MCP cathode for high field emission and durability. As a result of these achievements, a relatively high current density of ~ 1.2 A/cm2 from a CNT cathode and single channel MCP were measured. The emission current was also extremely stable with a peak-to-peak variation of only 1.8%. The emission current could be further enhanced to meet requirements for electron lens applications by increasing the number of MCP channels. A calculation for maximum possible current density with a 1200 channel/cm2 MCP, placed over a cathode with 1200 uniformly functioning CNTs, would be ~1.46 kA/cm2, neglecting space charge limitations. Clearly this level of emission is far greater than what is needed for the electron lens application, but it does offer a highly comforting margin to account for sub-standard emitters and/or to allow the lesser challenge of building a cathode with fewer channels/cm2. A satisfactory goal for the electron lens application would be a controllable emission of 2-4 mA per channel in an ensemble of 800-1200 uniformly-functioning channels/cm2, and a cathode with overall area of about 1 cm2.

  5. Studies in High Current Beam Propagation at Reduced Pressures.

    DTIC Science & Technology

    1985-01-31

    43 3.2.2 Beam-Driven Chemistry in the Low-Density Regime..... 44 3.2.3 Non-Local, Non-Ohmic Conductivity Model ............. 45... chemistry processes (especially recombina- tion), and the role of radiative cooling in determining the onset of Spitzer conduction. Progress in...represent the cynamics of the two lower-energy groups, and a detailed air- chemistry reaction scheme also modifies the population of the low-energy group

  6. Compact high current generator for x-ray radiography

    NASA Astrophysics Data System (ADS)

    Kharlov, A. V.; Kovalchuk, B. M.; Zorin, V. B.

    2006-12-01

    We report here a design of the portable high current generator, which can be used for a row of experiments and applications, including, but not limited to, X pinch, plasma focus, vacuum spark, etc. The X generator consists of the capacitor bank, multigap spark switch, load chamber, and built-in high voltage triggering generator. The capacitor bank consists of 12 General Atomics 35404 type capacitors (20nF, 25nH, 0.2Ω, 100kV). It stores ˜0.8kJ at 80kV charging voltage. Each three capacitors are commuted to a load by the multigap spark switch, which is able to commute by eight parallel channels. Switches operate in ambient air at atmospheric pressure. At 76kV charging voltage the generator provides ˜260kA with 120ns rise time and 5nH inductive load and ˜220kA with 145ns rise time and 10nH. Delay of output pulse relative to high voltage triggering pulse is ˜65ns with 5ns jitter. The dimensions of the generator are 1240×1240×225mm3 and the weight is ˜250kg, and only one high voltage power supply is required as additional equipment for the generator. The generator with a pumping system is placed on area about 0.5m2. Operation and handling are very simple, because no oil nor purified gases are required for the generator. The X generator has been successfully employed for experiments on the Ni X pinch load. X-ray pulse duration (full width at half maximum above 1keV) was about 5ns. Radiation yield Wr⩾500mJ was observed in the 1.2-1.5KeV range and Wr⩾20mJ in the 3-5keV energy range, which is comparable to results, obtained on the nanosecond accelerators. Clearly resolved images of 6μm wire indicate micron level size of hot spot. These results demonstrate possibility of this generator for application for x-ray backlighting.

  7. Electron trapping in high-current ion beam pipes

    SciTech Connect

    Herrmannsfeldt, W.B.

    2000-03-01

    The space charge voltage depression in a drifting heavy ion beam during the final stages of current pulse compression can be hundreds of kilovolts. For example, a 1kA beam of ions at beta = v/c = 0.4 would have a beam center-to-edge potential difference of 75kV. With suitable clearance from beam edge to the beam pipe, this amount is typically increased by a factor of 2 to 3 by the (1 + 2 ln(b/a)) term that accounts for the ratio of pipe radius to beam radius. Such high voltages, and resulting high electric fields at the pipe wall, will result in electrons being pulled into the beam pipe. These electrons which are emitted from the grounded beam pipe, will pass through the ion beam at high velocity and then turn around without (usually) striking the wall and continue to pass through the beam on repeated oscillations. It is possible to control the longitudinal motion of these trapped electrons by suitably varying the pipe size while considering the beam diameter. A segment of the beam pipe that has a larger diameter will result in a potential well that traps the electrons longitudinally. In a constant current scenario in a uniform pipe, the electrons will drift in the direction of the beam. However, the head and especially the tail of the ion beam will have a dramatic effect on the electrons, causing them to be pulled into the ion beam. These complex processes will continue until the ion beam passes through an optical element such as a beam transport magnet that will effectively block the motion of the electron clouds following the ions. In this paper, the authors will show examples of how electrons can be trapped and controlled by varying the conditions determining their emission and confinement. Ray tracing simulations using the EGN2[1] computer code will be used to model the electron trajectories in the presence of a high current heavy ion beam. The self magnetic field of the ion beam, while not sufficient to affect the ions themselves significantly, has a strong

  8. Nanocrystalline graphite: Promising material for high current field emission cathodes

    SciTech Connect

    Krivchenko, V. A.; Pilevsky, A. A.; Rakhimov, A. T.; Seleznev, B. V.; Suetin, N. V.; Timofeyev, M. A.; Bespalov, A. V.; Golikova, O. L.

    2010-01-15

    Electron field emission properties of nanocrystalline graphite (NCG) films, grown by plasma enhanced chemical vapor deposition method on conductive Si substrates without using of any catalyst, were investigated. Current-voltage characteristics were measured in pulse-periodic regime. It was shown that grown NCG films can operate at field emission current density up to 10 A/cm{sup 2}. It was found that NCG films contain, along with the normally oriented to the substrate nanoflakes, carbon whiskers consisted of graphene nanoribbons and nanowires with length considerably higher than of the nanoflakes.

  9. Development and fabrication of low ON resistance high current vertical VMOS power FETs

    NASA Technical Reports Server (NTRS)

    Kay, S.

    1979-01-01

    The design of a VMOS Power FET exhibiting low ON resistance, high current as well as high breakdown voltage and fast switching speeds is described. The design which is based on a 1st-order device model, features a novel polysilicon-gate structure and fieldplated groove termination to achieve high packing density and high breakdown voltage, respectively. One test chip, named VNTKI, can block 180 V at an ON resistence of 2.5 ohm. A 150 mil x 200 mil (.19 sq cm) experimental chip has demonstrated a breakdown voltage of 200v, an ON resistance of 0.12 ohm, a switching time of less than 100 ns, and a pulse drain - current of 50 A with 10 V gate drive.

  10. High-Current Pulsed Electron Treatment of Hypoeutectic Al-10Si Alloy

    NASA Astrophysics Data System (ADS)

    Diankun, Lu; Bo, Gao; Guanglin, Zhu; Jike, Lv; Liang, Hu

    2017-01-01

    This paper reports, for the first time, an analysis of the effect of high-current pulsed electron beam (HCPEB) on a hypoeutectic Al-10Si alloy. The Al-10Si alloy was treated by HCPEB in order to see the potential of this fairly recent technique in modifying its wear resistance. For the beam energy density of 3 J/cm2 used in the present work, the melting mode was operative and led to the formation of a "wavy" surface and the absence of mass primary Si phase and eutectic microstructure. The surface nanocrystallization of primary and eutectic Si phases led to the increase in macro-hardness of the top surface layer, and the wear resistance was drastically improved with a factor of 4.

  11. New methods for high current fast ion beam production by laser-driven acceleration.

    PubMed

    Margarone, D; Krasa, J; Prokupek, J; Velyhan, A; Torrisi, L; Picciotto, A; Giuffrida, L; Gammino, S; Cirrone, P; Cutroneo, M; Romano, F; Serra, E; Mangione, A; Rosinski, M; Parys, P; Ryc, L; Limpouch, J; Laska, L; Jungwirth, K; Ullschmied, J; Mocek, T; Korn, G; Rus, B

    2012-02-01

    An overview of the last experimental campaigns on laser-driven ion acceleration performed at the PALS facility in Prague is given. Both the 2 TW, sub-nanosecond iodine laser system and the 20 TW, femtosecond Ti:sapphire laser, recently installed at PALS, are used along our experiments performed in the intensity range 10(16)-10(19) W∕cm(2). The main goal of our studies was to generate high energy, high current ion streams at relatively low laser intensities. The discussed experimental investigations show promising results in terms of maximum ion energy and current density, which make the laser-accelerated ion beams a candidate for new-generation ion sources to be employed in medicine, nuclear physics, matter physics, and industry.

  12. High current gain 4H-SiC bipolar junction transistor

    NASA Astrophysics Data System (ADS)

    Yourun, Zhang; Jinfei, Shi; Ying, Liu; Chengchun, Sun; Fei, Guo; Bo, Zhang

    2016-04-01

    A novel 4H-SiC BJT of high current gain with a suppressing surface traps effect has been proposed. It is effective to improve the current gain due to the lower electrons density in the surface region by extending the emitter metal to overlap the passivation layer on the extrinsic base surface. The electrons trapped in the extrinsic base surface induce the degeneration of SiC BJTs device performance. By modulating the electron recombination rate, the novel structure can increase the current gain to 63.2% compared with conventional ones with the compatible process technology. Optimized sizes are an overlapped metal length of 4 μm, as well as an oxide layer thickness of 50 nm. Project supported by the National Natural Science Foundation of China (Nos. 61306093, 61401075).

  13. Optimization of Superconducting Focusing Quadrupoles for the HighCurrent Experiment

    SciTech Connect

    Sabbi, GianLuca; Gourlay, Steve; Gung, Chen-yu; Hafalia, Ray; Lietzke, Alan; Martovetski, Nicolai; Mattafirri, Sara; Meinke, Rainer; Minervini, Joseph; Schultz, Joel; Seidl, Peter

    2005-09-16

    The Heavy Ion Fusion (HIF) program is progressing through a series of physics and technology demonstrations leading to an inertial fusion power plant. The High Current Experiment (HCX) at Lawrence Berkeley National Laboratory is exploring the physics of intense beams with high line-charge density. Superconducting focusing quadrupoles have been developed for the HCX magnetic transport studies. A baseline design was selected following several pre-series models. Optimization of the baseline design led to the development of a first prototype that achieved a conductor-limited gradient of 132 T/m in a 70 mm bore, without training, with measured field errors at the 0.1% level. Based on these results, the magnet geometry and fabrication procedures were adjusted to improve the field quality. These modifications were implemented in a second prototype. In this paper, the optimized design is presented and comparisons between the design harmonics and magnetic measurements performed on the new prototype are discussed.

  14. New methods for high current fast ion beam production by laser-driven accelerationa)

    NASA Astrophysics Data System (ADS)

    Margarone, D.; Krasa, J.; Prokupek, J.; Velyhan, A.; Torrisi, L.; Picciotto, A.; Giuffrida, L.; Gammino, S.; Cirrone, P.; Cutroneo, M.; Romano, F.; Serra, E.; Mangione, A.; Rosinski, M.; Parys, P.; Ryc, L.; Limpouch, J.; Laska, L.; Jungwirth, K.; Ullschmied, J.; Mocek, T.; Korn, G.; Rus, B.

    2012-02-01

    An overview of the last experimental campaigns on laser-driven ion acceleration performed at the PALS facility in Prague is given. Both the 2 TW, sub-nanosecond iodine laser system and the 20 TW, femtosecond Ti:sapphire laser, recently installed at PALS, are used along our experiments performed in the intensity range 1016-1019 W/cm2. The main goal of our studies was to generate high energy, high current ion streams at relatively low laser intensities. The discussed experimental investigations show promising results in terms of maximum ion energy and current density, which make the laser-accelerated ion beams a candidate for new-generation ion sources to be employed in medicine, nuclear physics, matter physics, and industry.

  15. Drift distance survey in direct plasma injection scheme for high current beam production

    SciTech Connect

    Kanesue, T.; Okamura, M.; Kondo, K.; Tamura, J.; Kashiwagi, H.; Zhang, Z.

    2010-02-15

    In a laser ion source, plasma drift distance is one of the most important design parameters. Ion current density and beam pulse width are defined by plasma drift distance between a laser target and beam extraction position. In direct plasma injection scheme, which uses a laser ion source and a radio frequency quadrupole linac, we can apply relatively higher electric field at beam extraction due to the unique shape of a positively biased electrode. However, when we aim at very high current acceleration such as several tens of milliamperes, we observed mismatched beam extraction conditions. We tested three different ion current at ion extraction region by changing plasma drift distance to study better extraction condition. In this experiment, C{sup 6+} beam was accelerated. We confirmed that matching condition can be improved by controlling plasma drift distance.

  16. Application of optical emission spectroscopy to high current proton sources

    NASA Astrophysics Data System (ADS)

    Castro, G.; Mazzaglia, M.; Nicolosi, D.; Mascali, D.; Reitano, R.; Zaniol, B.; Celona, L.; Leonardi, O.; Leone, F.; Naselli, E.; Neri, L.; Torrisi, G.; Gammino, S.

    2017-07-01

    Optical Emission Spectroscopy (OES) represents a very reliable technique to carry out non-invasive measurements of plasma density and plasma temperature in the range of tens of eV. With respect to other diagnostics, it also can characterize the different populations of neutrals and ionized particles constituting the plasma. At INFN-LNS, OES techniques have been developed and applied to characterize the plasma generated by the Flexible Plasma Trap, an ion source used as "testbench" of the proton source built for European Spallation Source. This work presents the characterization of the parameters of a hydrogen plasma in different conditions of neutral pressure, microwave power and magnetic field profile, along with perspectives for further upgrades of the OES diagnostics system.

  17. Conformal Invariance in Driven Diffusive Systems at High Currents

    NASA Astrophysics Data System (ADS)

    Karevski, D.; Schütz, G. M.

    2017-01-01

    We consider space-time correlations in driven diffusive systems which undergo a fluctuation into a regime with an atypically large current or dynamical activity. For a single conserved mass we show that the spatiotemporal density correlations in one space dimension are fully determined by conformal field theory with central charge c =1 , corresponding to a ballistic universality class with dynamical exponent z =1 . The full phase diagram for general atypical behavior exhibits the conformally invariant regime and, for atypically low current or activity, a region of phase separation. The phase transition line between these two regimes corresponds to typical behavior and the dynamics belongs to the Kardar-Parisi-Zhang universality class with dynamical exponent z =3 /2 , except for a diffusive point with z =2 . The exact universal dynamical structure function is obtained in explicit form from the one-dimensional asymmetric simple exclusion process with periodic and open boundaries in the limit of maximal current.

  18. Conformal Invariance in Driven Diffusive Systems at High Currents.

    PubMed

    Karevski, D; Schütz, G M

    2017-01-20

    We consider space-time correlations in driven diffusive systems which undergo a fluctuation into a regime with an atypically large current or dynamical activity. For a single conserved mass we show that the spatiotemporal density correlations in one space dimension are fully determined by conformal field theory with central charge c=1, corresponding to a ballistic universality class with dynamical exponent z=1. The full phase diagram for general atypical behavior exhibits the conformally invariant regime and, for atypically low current or activity, a region of phase separation. The phase transition line between these two regimes corresponds to typical behavior and the dynamics belongs to the Kardar-Parisi-Zhang universality class with dynamical exponent z=3/2, except for a diffusive point with z=2. The exact universal dynamical structure function is obtained in explicit form from the one-dimensional asymmetric simple exclusion process with periodic and open boundaries in the limit of maximal current.

  19. Advanced Sulfur Cathode Enabled by Highly Crumpled Nitrogen-Doped Graphene Sheets for High-Energy-Density Lithium-Sulfur Batteries.

    PubMed

    Song, Jiangxuan; Yu, Zhaoxin; Gordin, Mikhail L; Wang, Donghai

    2016-02-10

    Herein, we report a synthesis of highly crumpled nitrogen-doped graphene sheets with ultrahigh pore volume (5.4 cm(3)/g) via a simple thermally induced expansion strategy in absence of any templates. The wrinkled graphene sheets are interwoven rather than stacked, enabling rich nitrogen-containing active sites. Benefiting from the unique pore structure and nitrogen-doping induced strong polysulfide adsorption ability, lithium-sulfur battery cells using these wrinkled graphene sheets as both sulfur host and interlayer achieved a high capacity of ∼1000 mAh/g and exceptional cycling stability even at high sulfur content (≥80 wt %) and sulfur loading (5 mg sulfur/cm(2)). The high specific capacity together with the high sulfur loading push the areal capacity of sulfur cathodes to ∼5 mAh/cm(2), which is outstanding compared to other recently developed sulfur cathodes and ideal for practical applications.

  20. Effects of Sediment Nitrogen Availability and Plant Density on Interactions Between the Growth of Hydrilla Verticillata and Potamogeton Americanus. Aquatic Plant Control Research Program.

    DTIC Science & Technology

    1991-12-01

    fractions. Suppression coefficients for each species were calculated to summarize competitive effects in mixtures relative to grow*.h of plants alone...11 4 Discussion Responses to Density A long-standing criticism of plant competition experiments has been the use of a single initial plant density... competitive superiority may be more sensitive than others to initial plant density (for review, see Rousch et al. 1989). However, initial plant density

  1. Surface composite nanostructures of AZ91 magnesium alloy induced by high current pulsed electron beam treatment

    NASA Astrophysics Data System (ADS)

    Li, M. C.; Hao, S. Z.; Wen, H.; Huang, R. F.

    2014-06-01

    High current pulsed electron beam (HCPEB) treatment was conducted on an AZ91 cast magnesium alloy with accelerating voltage 27 kV, energy density 3 J/cm2 and pulse duration 2.5 μs. The surface microstructure was characterized by optical microscope (OM), X-ray diffraction (XRD), scanning electron microscope (SEM) equipped with energy dispersive spectrometer (EDS), and transmission electron microscope (TEM). The surface corrosion property was tested with electrochemical method in 3.5 wt.% NaCl solution. It is found that after 1 pulse of HCPEB treatment, the initial eutectic α phase and Mg17Al12 particles started to dissolve in the surface modified layer of depth ∼15 μm. When using 15 HCPEB pulses, the Al content in surface layer increased noticeably, and the phase structure was modified as composite nanostructures consisted of nano-grained Mg3.1Al0.9 domains surrounded by network of Mg17Al12 phase. The HCPEB treated samples showed an improved corrosion resistance with cathodic current density decreased by two orders of magnitude as compared to the initial AZ91 alloy.

  2. Simulative research on the expansion of cathode plasma in high-current electron beam diode

    SciTech Connect

    Xu Qifu; Liu Lie

    2012-09-15

    The expansion of cathode plasma has long been recognized as a limiting factor in the impedance lifetime of high-current electron beam diode. Realistic modeling of such plasma is of great necessity in order to discuss the dynamics of cathode plasma. Using the method of particle-in-cell, the expansion of cathode plasma is simulated in this paper by a scaled-down diode model. It is found that the formation of cathode plasma increases the current density in the diode. This consequently leads to the decrease of the potential at plasma front. Once the current density has been increased to a certain value, the potential at plasma front would then be equal to or lower than the plasma potential. Then the ions would move towards the anode, and the expansion of cathode plasma is thereby formed. Different factors affecting the plasma expansion velocity are discussed in this paper. It is shown that the decrease of proton genatation rate has the benefit of reducing the plasma expansion velocity.

  3. High yield neutron generator based on a high-current gasdynamic electron cyclotron resonance ion source

    SciTech Connect

    Skalyga, V.; Sidorov, A.; Izotov, I.; Golubev, S.; Razin, S.; Strelkov, A.; Tarvainen, O.; Koivisto, H.; Kalvas, T.

    2015-09-07

    In present paper, an approach for high yield compact D-D neutron generator based on a high current gasdynamic electron cyclotron resonance ion source is suggested. Results on dense pulsed deuteron beam production with current up to 500 mA and current density up to 750 mA/cm{sup 2} are demonstrated. Neutron yield from D{sub 2}O and TiD{sub 2} targets was measured in case of its bombardment by pulsed 300 mA D{sup +} beam with 45 keV energy. Neutron yield density at target surface of 10{sup 9} s{sup −1} cm{sup −2} was detected with a system of two {sup 3}He proportional counters. Estimations based on obtained experimental results show that neutron yield from a high quality TiD{sub 2} target bombarded by D{sup +} beam demonstrated in present work accelerated to 100 keV could reach 6 × 10{sup 10} s{sup −1} cm{sup −2}. It is discussed that compact neutron generator with such characteristics could be perspective for a number of applications like boron neutron capture therapy, security systems based on neutron scanning, and neutronography.

  4. Efficient and durable hydrogen evolution electrocatalyst based on nonmetallic nitrogen doped hexagonal carbon

    NASA Astrophysics Data System (ADS)

    Liu, Yanming; Yu, Hongtao; Quan, Xie; Chen, Shuo; Zhao, Huimin; Zhang, Yaobin

    2014-10-01

    The feasibility of renewable energy technology, hydrogen production by water electrolysis, depends on the design of efficient and durable electrocatalyst composed of earth-abundant elements. Herein, a highly active and stable nonmetallic electrocatalyst, nitrogen doped hexagonal carbon (NHC), was developed for hydrogen production. It exhibited high activity for hydrogen evolution with a low overpotential of only 65 mV, an apparent exchange current density of 5.7 × 10-2 mA cm-2 and a high hydrogen production rate of 20.8 mL cm-2 h-1 at -0.35 V. The superior hydrogen evolution activity of NHC stemmed from the intrinsic electrocatalytic property of hexagonal nanodiamond, the rapid charge transfer and abundance of electrocatalytic sites after nitrogen doping. Moreover, NHC was stable in a corrosive acidic solution during electrolysis under high current density.

  5. Response of Growth and Density of a Population of Geukensia demissa to Land-Derived Nitrogen Loading, in Waquoit Bay, Massachusetts

    NASA Astrophysics Data System (ADS)

    Evgenidou, A.; Valiela, I.

    2002-07-01

    Nutrient enrichment is a widespread phenomenon affecting coastal waters, including salt marshes. As land-derived nitrogen loading in estuarine waters increases, chlorophyll concentrations in the water also increase. We hypothesized that such increases might increase growth of the food-limited population of Geukensia demissa, which is a dominant component of salt marshes. To test this, we conducted a regional scale experiment in three estuaries of Waquoit Bay, Massachusetts that receive different nitrogen loading rates. A stable isotope experiment on mussel tissues and on particulate organic matter (POM) showed that mussels within an estuary fed on POM characteristic of that estuary, demonstrating the direct linkage between POM and mussels within an estuary. In addition, we measured age-specific shell growth rates of mussel populations using two different methods: indirectly, shell growth of mussels indicated by internal shell-lines was measured by fitting the data to the von Bertalanffy equation, and directly, mussels were transplanted from one estuary to the other two, and their actual shell growth rates after 80 days were measured. Growth rates of mussels in the Waquoit Bay estuaries varied with age of the mussel, tidal elevation, and with mean concentration of chlorophyll in the water. Mussels grew best in the lower intertidal zone, at the marsh banks. Young mussels grew faster than older mussels. Growth rates increased in response to presumed greater food supply across the estuaries, only for younger mussels. The significant differences we found among the mussels from different estuaries indicate a response to higher concentrations of food particles available in estuaries subject to higher nitrogen loads.

  6. A general approach for fabrication of nitrogen-doped graphene sheets and its application in supercapacitors.

    PubMed

    Wang, Dewei; Min, Yonggang; Yu, Youhai; Peng, Bo

    2014-03-01

    In this paper, a general and efficient strategy has been developed to produce nitrogen-doped graphene sheets (NGs) based on hard and soft acids and bases (HSAB) theory. Under hydrothermal conditions, any salt with amphiprotic character have a strong tendency to hydrolysis, it is possible to provide reducing agent and nitrogen source simultaneously. It is worth noting that, NGs can be prepared under hydrothermal conditions by using some common ammonium salts with hard acid-soft base pairs as nitrogen-doping agents. The morphology, structure and composition of the as-prepared NGs were studied in detail. The results demonstrated that large amount of nitrogen was incorporated into the nanocarbon frameworks at the same time as the graphene oxide (GO) sheets were reduced. The electrochemical behavior of the synthesized NGs as supercapacitor electrodes was evaluated in a symmetric two-electrode cell configuration with 1M H2SO4 as the electrolytes. It was found that the nitrogen groups making the as-prepared NGs exhibited remarkably enhanced electrochemical performance when used as electrode materials in supercapacitors. The supercapacitor based on the NGs exhibited a high specific capacitance of 242 F g(-1) at a current density of 1 A g(-1), and remains a relatively high capacitance even at a high current density. This work will put forward to understand and optimize heteroatom-doped graphene in energy storage systems.

  7. Effect of stocking density on performance, diet selection, total-tract digestion, and nitrogen balance among heifers grazing cool-season annual forages.

    PubMed

    Brunsvig, B R; Smart, A J; Bailey, E A; Wright, C L; Grings, E E; Brake, D W

    2017-08-01

    Grazing annual cool-season forages after oat grain harvest in South Dakota may allow an opportunity to increase efficient use of tillable land. However, data are limited regarding effects of stocking density on diet selection, nutrient digestion, performance, and N retention by cattle grazing annual cool-season forage. Heifers were blocked by initial BW (261 ± 11.7 kg) and randomly assigned to 1 of 12 paddocks (1.1 ha) to graze a mixture of grass and brassica for 48 d. Each paddock contained 3, 4, or 5 heifers to achieve 4 replicates of each stocking density treatment. Ruminally cannulated heifers were used to measure diet and nutrient intake. Effects of stocking density on diet and nutrient selection were measured after 2, 24, and 46 d of grazing, and BW was measured at the beginning, middle, and end of the experiment as the average of d 1 and 2, d 22 and 23, and d 47 and 48 BW, respectively. Measures of DMI and DM, OM, NDF, and ADF digestion were collected from d 18 to 23. Increased stocking density increased intake of brassica relative to grass on d 24 (quadratic, = 0.02), but increased stocking density decreased (linear, ≤ 0.01) intake of brassica compared with grass on d 48 (stocking density × time, < 0.01). Increased stocking density increased DM (quadratic, < 0.01), OM (quadratic, = 0.01), and NDF (quadratic, = 0.05) digestion, and stocking density tended to increase DMI (quadratic, = 0.07). Additionally, increased stocking density quadratically increased ( = 0.05) N retention but did not affect overall BW gains. Increased stocking density did, however, contribute to linearly decreased ( = 0.05) BW gains from d 1 to 22 of grazing, but BW gains during the latter half of the experiment were greater than BW gains from d 1 to 22. Ruminal concentration of acetate:propionate was least on d 24 of grazing, and ruminal nitrate concentration tended to linearly decrease ( = 0.06) with greater amounts of time on pasture. Ruminal liquid and particulate fill and

  8. Indicators: Nitrogen

    EPA Pesticide Factsheets

    Nitrogen, like phosphorus, is a critical nutrient required for all life. Nitrogen can occur in rivers and streams, lakes, and coastal waters in several forms including ammonia (NH3), nitrates (NO3), and nitrites (NO2).

  9. Langmuir probe diagnostics of plasma in high current electron cyclotron resonance proton ion source

    SciTech Connect

    Roychowdhury, P.; Kewlani, H.; Mishra, L.; Mittal, K. C.; Patil, D. S.

    2013-07-15

    A high current Electron Cyclotron Resonance (ECR) proton ion source has been developed for low energy high intensity proton accelerator at Bhabha Atomic Research Centre. Langmuir probe diagnostics of the plasma generated in this proton ion source is performed using Langmuir probe. The diagnostics of plasma in the ion source is important as it determines beam parameters of the ion source, i.e., beam current, emittance, and available species. The plasma parameter measurement in the ion source is performed in continuously working and pulsed mode using hydrogen as plasma generation gas. The measurement is performed in the ECR zone for operating pressure and microwave power range of 10{sup −4}–10{sup −3} mbar and 400–1000 W. An automated Langmuir probe diagnostics unit with data acquisition system is developed to measure these parameters. The diagnostics studies indicate that the plasma density and plasma electron temperature measured are in the range 5.6 × 10{sup 10} cm{sup −3} to 3.8 × 10{sup 11} cm{sup −3} and 4–14 eV, respectively. Using this plasma, ion beam current of tens of mA is extracted. The variations of plasma parameters with microwave power, gas pressure, and radial location of the probe have been studied.

  10. Design and characterization of the annular cathode high current pulsed electron beam source for circular components

    NASA Astrophysics Data System (ADS)

    Jiang, Wei; Wang, Langping; Wang, Xiaofeng

    2016-08-01

    In order to irradiate circular components with high current pulsed electron beam (HCPEB), an annular cathode based on carbon fiber bunches was designed and fabricated. Using an acceleration voltage of 25 kV, the maximum pulsed irradiation current and energy of this annular cathode can reach 7.9 kA and 300 J, respectively. The irradiation current density distribution of the annular cathode HCPEB source measured along the circumferential direction shows that the annular cathode has good emission uniformity. In addition, four 9310 steel substrates fixed uniformly along the circumferential direction of a metal ring substrate were irradiated by this annular cathode HCPEB source. The surface and cross-section morphologies of the irradiated samples were characterized by scanning electron microscopy (SEM). SEM images of the surface reveal that crater and surface undulation have been formed, which hints that the irradiation energy of the HCPEB process is large enough for surface modification of 9310 steel. Meanwhile, SEM cross-section images exhibit that remelted layers with a thickness of about 5.4 μm have been obtained in all samples, which proves that a good practical irradiation uniformity can be achieved by this annular cathode HCPEB source.

  11. High-Current Gain Two-Dimensional MoS₂-Base Hot-Electron Transistors.

    PubMed

    Torres, Carlos M; Lan, Yann-Wen; Zeng, Caifu; Chen, Jyun-Hong; Kou, Xufeng; Navabi, Aryan; Tang, Jianshi; Montazeri, Mohammad; Adleman, James R; Lerner, Mitchell B; Zhong, Yuan-Liang; Li, Lain-Jong; Chen, Chii-Dong; Wang, Kang L

    2015-12-09

    The vertical transport of nonequilibrium charge carriers through semiconductor heterostructures has led to milestones in electronics with the development of the hot-electron transistor. Recently, significant advances have been made with atomically sharp heterostructures implementing various two-dimensional materials. Although graphene-base hot-electron transistors show great promise for electronic switching at high frequencies, they are limited by their low current gain. Here we show that, by choosing MoS2 and HfO2 for the filter barrier interface and using a noncrystalline semiconductor such as ITO for the collector, we can achieve an unprecedentedly high-current gain (α ∼ 0.95) in our hot-electron transistors operating at room temperature. Furthermore, the current gain can be tuned over 2 orders of magnitude with the collector-base voltage albeit this feature currently presents a drawback in the transistor performance metrics such as poor output resistance and poor intrinsic voltage gain. We anticipate our transistors will pave the way toward the realization of novel flexible 2D material-based high-density, low-energy, and high-frequency hot-carrier electronic applications.

  12. High current metal ion implantation to synthesize some conducting metal-silicides

    SciTech Connect

    Liu, B. X.; Gao, K. Y.

    1999-06-10

    High current metal-ion implantation by a metal vapor vacuum arc ion source was conducted to synthesize some conducting metal-silicides. It was found that C54-TiSi{sub 2}, ZrSi{sub 2}, NiSi{sub 2}, CoSi{sub 2}, {beta}-FeSi{sub 2}, NbSi{sub 2} and TaSi{sub 2} layers on Si wafers with good electric properties could be obtained directly after implantation. In comparison, the formation of some other silicides like {alpha}-FeSi{sub 2}, NbSi{sub 2}, TaSi{sub 2}, tetragonal-WSi{sub 2} and tetragonal-MoSi{sub 2} required an additional post-annealing to improve their crystallinity and thus their electric properties. Interestingly, the NiSi{sub 2} layers of superior electric properties were obtained at a selected Ni-ion current density of 35 {mu}A/cm{sup 2}. At this current, a beam heating raised the Si wafer to a specific temperature of 380 deg. C, at which the size difference between NiSi{sub 2} and Si lattices was nil. The resistivity of the NiSi{sub 2} layers so obtained was much lower than that of the Ni-disilicide formed by solid-state reaction at >750 deg. C. The formation mechanism of the above metal-silicides and the associated electric properties will also be discussed.

  13. Comparison of Electron Cloud Simulation and Experiments in the High-Current Experiment

    SciTech Connect

    Cohen, R H; Friedman, A; Covo, M K; Lund, S M; Molvik, A W; Bieniosek, F M; Seidl, P A; Vay, J; Stoltz, P; Veitzer, S

    2004-11-11

    Contaminating clouds of electrons are a common concern for accelerators of positive-charged particles, but there are some unique aspects of heavy-ion accelerators for fusion and high-energy density physics which make modeling such clouds especially challenging. In particular, self-consistent electron and ion simulation is required, including a particle advance scheme which can follow electrons in regions where electrons are strongly, weakly, and un-magnetized. We describe our approach to such self-consistency, and in particular a scheme for interpolating between full-orbit (Boris) and drift-kinetic particle pushes that enables electron time steps long compared to the typical gyro period in the magnets. We present tests and applications: simulation of electron clouds produced by three different kinds of sources indicates the sensitivity of the cloud shape to the nature of the source; first-of-a-kind self-consistent simulation of electron-cloud experiments on the High-Current Experiment (HCX) at LBNL, in which the machine can be flooded with electrons released by impact of the ion beam on an end plate, demonstrate the ability to reproduce key features of the ion-beam phase space; and simulation of a two-stream instability of thin beams in a magnetic field demonstrate the ability of the large-timestep mover to accurately calculate the instability.

  14. Evaluation of conductor stresses in a pulsed high-current toroidal transformer

    SciTech Connect

    Turchi, Peter J; Rousculp, Chritopher L; Reass, William A; Oro, David M; Merrill, Frank E; Greigo, Jeffery R; Reinovsky, Robert E

    2009-01-01

    The Precision, High-Energy Density, Liner Implosion Experiment (PHELIX) pulsed power driver is currently under development at Los Alamos National Laboratory. When operational PHELIX will provide 5-10 MAmps of peak current with pulse rise-time of {approx} 5-10 ms. Crucial to the performance of PHELIX is a multi-turn primary, single-turn secondary, current step-up toroidal transformer, R{sub major} {approx} 30 cm, R{sub minor} {approx} 10 cm. The transformer lifetime should exceed 100 shots. Therefore it is essential that the design be robust enough to survive the magnetic stresses produced by high currents. In order to evaluate their design, two methods have been utilized. First, an analytical evaluation has been performed. By identifying the magnetic forces as J{sub 1}{sup 2}/2 {del}L{sub 1} + J{sub 1}J{sub 2}{del}M{sub 12}, where J{sub 1} and J{sub 2} are currents in two circuits, coupled by mutual inductance M{sub 12} and L{sub 1} is the self-inductance of the circuit carrying current J{sub 1}, analytical estimates of stress can be obtained. These results are then compared to a computational MHD model of the same system and to a full finite-element, electromagnetic simulation.

  15. Probe characterization of high-current driven metal plasma in a vacuum-arc rail gun

    NASA Astrophysics Data System (ADS)

    Vijayan, T.; Roychowdhury, P.; Venkatramani, N.

    2004-10-01

    The characteristics of metal plasma launched by high-current electric arc in a vacuum-arc rail gun are determined by employing electrical and magnetic probes. These measurements are validated by results from theoretical simulations. The arc coupled nonlinear circuit equations are solved simultaneously with the Newtonian arc motion and revealed the undercritically damped behavior of the arc current identical to the arc-current signal recorded by the Rogowski magnetic probe. Similarly the arc velocity and displacement derived from the signatures of B-dot probes are shown to concur closely with the results of J ×B propulsion from simulation. The heating of plasma is formulated in a three-electron population regime with direct arc energy coupling through magnetohydrodynamic, ion-acoustic, Coulomb, and neutral interactions. This results in high temperature (Te) of hundreds of eV in the arc as revealed by the simulation. Hence Te of the rapidly cooling and equilibrating plasma that emerged from the muzzle is high around 80-90eV, which is confirmed by Langmuir electric probe measurements. Density ne of this metal plasma is shown to be in the range 4×1021-6×1021m-3 and includes multiple ion charge states. The exit velocity of the plasma measured by a pair of Langmuir probes is close to 2.2×106cm/s and matched well with the arc velocity determined by the B-dot probes and the results from simulation.

  16. High current pulsed electron beam treatment of AZ31 Mg alloy

    SciTech Connect

    Gao Bo; Hao Shengzhi; Zou Jianxin; Grosdidier, Thierry; Jiang Limin; Zhou Jiyang; Dong Chuang

    2005-11-15

    This paper reports, for the first time, an analysis of the effect of High Current Pulsed Electron Beam (HCPEB) on a Mg alloy. The AZ31 alloy was HCPEB treated in order to see the potential of this fairly recent technique in modifying its wear resistance. For the 2.5 J/cm{sup 2} beam energy density used in the present work, the evaporation mode was operative and led to the formation of a ''wavy'' surface and the absence of eruptive microcraters. The selective evaporation of Mg over Al led to an Al-rich melted surface layer and precipitation hardening from the over saturated solid solution. Due to the increase in hardness of the top surface layer, the friction coefficient values were lowered by more than 20% after the HCPEB treatments, and the wear resistance was drastically (by a factor of 6) improved. The microhardness of the HCPEB samples was also increased significantly down to a depth of about 500 {mu}m, far exceeding the heat-affected zone (about 40 {mu}m). This is due to the effect of the propagation of the shockwave associated with this HCPEB treatment.

  17. A Novel High-Density Phase and Amorphization of Nitrogen-Rich 1H-Tetrazole (CH2N4) under High Pressure

    PubMed Central

    Li, Wenbo; Huang, Xiaoli; Bao, Kuo; Zhao, Zhonglong; Huang, Yanping; Wang, Lu; Wu, Gang; Zhou, Bo; Duan, Defang; Li, Fangfei; Zhou, Qiang; Liu, Bingbing; Cui, Tian

    2017-01-01

    The high-pressure behaviors of nitrogen-rich 1H-tetrazole (CH2N4) have been investigated by in situ synchrotron X-ray diffraction (XRD) and Raman scattering up to 75 GPa. A first crystalline-to-crystalline phase transition is observed and identified above ~3 GPa with a large volume collapse (∼18% at 4.4 GPa) from phase I to phase II. The new phase II forms a dimer-like structure, belonging to P1 space group. Then, a crystalline-to-amorphous phase transition takes place over a large pressure range of 13.8 to 50 GPa, which is accompanied by an interphase region approaching paracrystalline state. When decompression from 75 GPa to ambient conditions, the final product keeps an irreversible amorphous state. Our ultraviolet (UV) absorption spectrum suggests the final product exhibits an increase in molecular conjugation. PMID:28218236

  18. A Novel High-Density Phase and Amorphization of Nitrogen-Rich 1H-Tetrazole (CH2N4) under High Pressure

    NASA Astrophysics Data System (ADS)

    Li, Wenbo; Huang, Xiaoli; Bao, Kuo; Zhao, Zhonglong; Huang, Yanping; Wang, Lu; Wu, Gang; Zhou, Bo; Duan, Defang; Li, Fangfei; Zhou, Qiang; Liu, Bingbing; Cui, Tian

    2017-02-01

    The high-pressure behaviors of nitrogen-rich 1H-tetrazole (CH2N4) have been investigated by in situ synchrotron X-ray diffraction (XRD) and Raman scattering up to 75 GPa. A first crystalline-to-crystalline phase transition is observed and identified above ~3 GPa with a large volume collapse (∼18% at 4.4 GPa) from phase I to phase II. The new phase II forms a dimer-like structure, belonging to P1 space group. Then, a crystalline-to-amorphous phase transition takes place over a large pressure range of 13.8 to 50 GPa, which is accompanied by an interphase region approaching paracrystalline state. When decompression from 75 GPa to ambient conditions, the final product keeps an irreversible amorphous state. Our ultraviolet (UV) absorption spectrum suggests the final product exhibits an increase in molecular conjugation.

  19. Radiation damage in single crystal CVD diamond material investigated with a high current relativistic 197Au beam

    NASA Astrophysics Data System (ADS)

    Pietraszko, J.; Galatyuk, T.; Grilj, V.; Koenig, W.; Spataro, S.; Träger, M.

    2014-11-01

    Single-crystal Chemical Vapor Deposition (ScCVD) diamond based prototype detectors have been constructed for the high intensity heavy ion experiments HADES and CBM at the future FAIR facility at GSI Darmstadt. Their properties have been studied with a high current density beam (about 2-3×106/s/mm2) of 1.25A GeV Au69+197 ions. Details of the design, the intrinsic properties of the detectors and their performance after irradiation with such a beam are reported.

  20. Modeling of the anode surface deformation in high-current vacuum arcs with AMF contacts

    NASA Astrophysics Data System (ADS)

    Huang, Xiaolong; Wang, Lijun; Deng, Jie; Jia, Shenli; Qin, Kang; Shi, Zongqian

    2016-02-01

    A high-current vacuum arc subjected to an axial magnetic field is maintained in a diffuse status. With an increase in arc current, the energy carried by the arc column to the anode becomes larger and finally leads to the anode temperature exceeding the melting point of the anode material. When the anode melting pool is formed, and the rotational plasma of the arc column delivers its momentum to the melting pool, the anode melting pool starts to rotate and also flow outwards along the radial direction, which has been photographed by some researchers using high-speed cameras. In this paper, the anode temperature and melting status is calculated using the melting and solidification model. The swirl flow of the anode melting pool and deformation of the anode is calculated using the magneto-hydrodynamic (MHD) model with the volume of fraction (VOF) method. All the models are transient 2D axial-rotational symmetric models. The influence of the impaction force of the arc plasma, electromagnetic force, viscosity force, and surface tension of the liquid metal are all considered in the model. The heat flux density injected into the anode and the arc pressure are obtained from the 3D numerical simulation of the high-current vacuum arc using the MHD model, which gives more realistic parameters for the anode simulation. Simulation results show that the depth of the anode melting pool increases with an increase in the arc current. Some droplets sputter out from the anode surface, which is caused by the inertial centrifugal force of the rotational melting pool and strong plasma pressure. Compared with the previous anode melting model without consideration of anode deformation, when the deformation and swirl flow of the anode melting pool are considered, the anode temperature is relatively lower, and just a little more than the melting point of Cu. This is because of liquid droplets sputtering out of the anode surface taking much of the energy away from the anode surface. The

  1. An investigation of hydrogen-bonding effects on the nitrogen and hydrogen electric field gradient and chemical shielding tensors in the 9-methyladenine real crystalline structure: a density functional theory study.

    PubMed

    Mirzaei, Mahmoud; Hadipour, Nasser L

    2006-04-13

    Hydrogen-bonding effects in the real crystalline structure of 9-methyladenine, 9-MA, were studied using calculated electric field gradient, EFG, and chemical shielding, CS, tensors for nitrogen and hydrogen nuclei via density functional theory. The calculations were carried out at the B3LYP and B3PW91 levels with the 6-311++G basis set via the Gaussian 98 package. Nuclear quadrupole coupling constants, C(Q), and asymmetry parameters, eta(Q), are reported for (14)N and (2)H. The chemical shielding anisotropy, Deltasigma, and chemical shielding isotropy, sigma(iso), are also reported for (15)N and (1)H. The difference between the calculated parameters of the monomer and heptameric layer-like cluster 9-MA shows how much H-bonding interactions affect the EFG and CS tensors of each nucleus. This result indicates that N(10) (imino nitrogen) has a major role in H-bonding interactions, whereas that of N(9) is negligible. There is good agreement between the present calculated parameters and reported experimental data. Although some discrepancies were observed, this could be attributed to the different conditions which were applied for calculation and the experiments.

  2. The structure and properties of boron carbide ceramics modified by high-current pulsed electron-beam

    SciTech Connect

    Ivanov, Yuri; Tolkachev, Oleg Petyukevich, Maria Polisadova, Valentina; Teresov, Anton; Ivanova, Olga Ikonnikova, Irina

    2016-01-15

    The present work is devoted to numerical simulation of temperature fields and the analysis of structural and strength properties of the samples surface layer of boron carbide ceramics treated by the high-current pulsed electron-beam of the submillisecond duration. The samples made of sintered boron carbide ceramics are used in these investigations. The problem of calculating the temperature field is reduced to solving the thermal conductivity equation. The electron beam density ranges between 8…30 J/cm{sup 2}, while the pulse durations are 100…200 μs in numerical modelling. The results of modelling the temperature field allowed ascertaining the threshold parameters of the electron beam, such as energy density and pulse duration. The electron beam irradiation is accompanied by the structural modification of the surface layer of boron carbide ceramics either in the single-phase (liquid or solid) or two-phase (solid-liquid) states. The sample surface of boron carbide ceramics is treated under the two-phase state (solid-liquid) conditions of the structural modification. The surface layer is modified by the high-current pulsed electron-beam produced by SOLO installation at the Institute of High Current Electronics of the Siberian Branch of the Russian Academy of Sciences, Tomsk, Russia. The elemental composition and the defect structure of the modified surface layer are analyzed by the optical instrument, scanning electron and transmission electron microscopes. Mechanical properties of the modified layer are determined measuring its hardness and crack resistance. Research results show that the melting and subsequent rapid solidification of the surface layer lead to such phenomena as fragmentation due to a crack network, grain size reduction, formation of the sub-grained structure due to mechanical twinning, and increase of hardness and crack resistance.

  3. The structure and properties of boron carbide ceramics modified by high-current pulsed electron-beam

    NASA Astrophysics Data System (ADS)

    Ivanov, Yuri; Tolkachev, Oleg; Petyukevich, Maria; Teresov, Anton; Ivanova, Olga; Ikonnikova, Irina; Polisadova, Valentina

    2016-01-01

    The present work is devoted to numerical simulation of temperature fields and the analysis of structural and strength properties of the samples surface layer of boron carbide ceramics treated by the high-current pulsed electron-beam of the submillisecond duration. The samples made of sintered boron carbide ceramics are used in these investigations. The problem of calculating the temperature field is reduced to solving the thermal conductivity equation. The electron beam density ranges between 8…30 J/cm2, while the pulse durations are 100…200 μs in numerical modelling. The results of modelling the temperature field allowed ascertaining the threshold parameters of the electron beam, such as energy density and pulse duration. The electron beam irradiation is accompanied by the structural modification of the surface layer of boron carbide ceramics either in the single-phase (liquid or solid) or two-phase (solid-liquid) states. The sample surface of boron carbide ceramics is treated under the two-phase state (solid-liquid) conditions of the structural modification. The surface layer is modified by the high-current pulsed electron-beam produced by SOLO installation at the Institute of High Current Electronics of the Siberian Branch of the Russian Academy of Sciences, Tomsk, Russia. The elemental composition and the defect structure of the modified surface layer are analyzed by the optical instrument, scanning electron and transmission electron microscopes. Mechanical properties of the modified layer are determined measuring its hardness and crack resistance. Research results show that the melting and subsequent rapid solidification of the surface layer lead to such phenomena as fragmentation due to a crack network, grain size reduction, formation of the sub-grained structure due to mechanical twinning, and increase of hardness and crack resistance.

  4. Specific and efficient electrochemical selection of Geoalkalibacter subterraneus and Desulfuromonas acetoxidans in high current-producing biofilms.

    PubMed

    Pierra, Mélanie; Carmona-Martínez, Alessandro A; Trably, Eric; Godon, Jean-Jacques; Bernet, Nicolas

    2015-12-01

    Two different saline sediments were used to inoculate potentiostatically controlled reactors (a type of microbial bioelectrochemical system, BES) operated in saline conditions (35 gNaCl l(-1)). Reactors were fed with acetate or a mixture of acetate and butyrate at two pH values: 7.0 or 5.5. Electroactive biofilm formation lag-phase, maximum current density production and coulombic efficiency were used to evaluate the overall performance of reactors. High current densities up to 8.5 A m(-2) were obtained using well-defined planar graphite electrodes. Additionally, biofilm microbial communities were characterized by CE-SSCP and 454 pyrosequencing. As a result of this procedure, two anode-respiring bacteria (ARB) always dominated the anodic biofilms: Geoalkalibacter subterraneus and/or Desulfuromonas acetoxidans. This suggests that a strong electrochemically driven selection process imposed by the applied potential occurs in the BES system. Moreover, the emergence of Glk. subterraneus in anodic biofilms significantly contributes to broaden the spectrum of high current producing microorganisms electrochemically isolated from environmental samples.

  5. A high-current electron gun for the electron beam ion trap at the National Superconducting Cyclotron Laboratory

    SciTech Connect

    Schwarz, S. Baumann, T. M.; Kittimanapun, K.; Lapierre, A.; Snyder, A.

    2014-02-15

    The Electron Beam Ion Trap (EBIT) in NSCL’s reaccelerator ReA uses continuous ion injection and accumulation. In order to maximize capture efficiency and minimize breeding time into high charge states, the EBIT requires a high-current/high current-density electron beam. A new electron gun insert based on a concave Ba-dispenser cathode has been designed and built to increase the current transmitted through the EBIT’s superconducting magnet. With the new insert, stable EBIT operating conditions with 0.8 A of electron beam have been established. The design of the electron gun is presented together with calculated and measured perveance data. In order to assess the experimental compression of the electron beam, a pinhole CCD camera has been set up to measure the electron beam radius. The camera observes X-rays emitted from highly charged ions, excited by the electron beam. Initial tests with this camera setup will be presented. They indicate that a current density of 640 A/cm{sup 2} has been reached when the EBIT magnet was operated at 4 T.

  6. A high-current electron gun for the electron beam ion trap at the National Superconducting Cyclotron Laboratory

    NASA Astrophysics Data System (ADS)

    Schwarz, S.; Baumann, T. M.; Kittimanapun, K.; Lapierre, A.; Snyder, A.

    2014-02-01

    The Electron Beam Ion Trap (EBIT) in NSCL's reaccelerator ReA uses continuous ion injection and accumulation. In order to maximize capture efficiency and minimize breeding time into high charge states, the EBIT requires a high-current/high current-density electron beam. A new electron gun insert based on a concave Ba-dispenser cathode has been designed and built to increase the current transmitted through the EBIT's superconducting magnet. With the new insert, stable EBIT operating conditions with 0.8 A of electron beam have been established. The design of the electron gun is presented together with calculated and measured perveance data. In order to assess the experimental compression of the electron beam, a pinhole CCD camera has been set up to measure the electron beam radius. The camera observes X-rays emitted from highly charged ions, excited by the electron beam. Initial tests with this camera setup will be presented. They indicate that a current density of 640 A/cm2 has been reached when the EBIT magnet was operated at 4 T.

  7. Time and space resolved spectroscopic investigation during anode plume formation in a high-current vacuum arc

    NASA Astrophysics Data System (ADS)

    Khakpour, A.; Methling, R.; Uhrlandt, D.; Franke, St.; Gortschakow, S.; Popov, S.; Batrakov, A.; Weltmann, K. D.

    2017-05-01

    This paper presents time and space resolved results of spectroscopic measurements during the formation of an anode plume in the late current pulse phase of a high-current vacuum arc. The formation of the anode plume is investigated systematically based on the occurrence of high-current anode spots, depending on gap distance and current for AC 100 Hz and CuCr7525 butt contacts with a diameter of 10 mm. The anode plume is observed after the extinction of anode spot type 2 in which both the anode and cathode are active. It is concluded from the spatial profiles of the atomic and ionic radiation, parallel and perpendicular to anode surface, that the inner part of the plume is dominated by Cu I radiation, whereas a halo of light emitted by Cu II covers the plume. The radiation intensity of Cu III lines is quite low across the whole anode plume. Upper level excited state densities corresponding to Cu I lines at 510.55, 515.32, 521.82, 578.21 nm are determined. The temporal evolution of the resulting excitation temperature in the centre of the plume varies from 8500 K to 6000 K at 500 µs to 100 µs before current zero, respectively. The density calculated for Cu I at position in the plume is in the range of 1-5  ×  1019 m-3.

  8. Field Testing of High Current Electrokinetic Nanoparticle Treatment for Corrosion Mitigation in Reinforced Concrete

    NASA Technical Reports Server (NTRS)

    Cardenas, Henry; Alexander, Joshua; Kupwade-Patil, Kunal; Calle, Luz marina

    2010-01-01

    Electrokinetic Nanoparticle (EN) treatment was used as a rapid repair measure to mitigate chloride induced corrosion of reinforced concrete in the field. EN treatment uses an electric field to transport positively charged nanoparticles to the reinforcement through the concrete capillary pores. Cylindrical reinforced concrete specimens were batched with 4.5 wt % salt content (based on cement mass). Three distinct electrokinetic treatments were conducted using high current density (up to 5 A/m2) to form a chloride penetration barrier that was established in 5 days, as opposed to the traditional 6-8 weeks, generally required for electrochemical chloride extraction (ECE). These treatments included basic EN treatment, EN with additional calcium treatment, and basic ECE treatment. Field exposures were conducted at the NASA Beachside Corrosion Test Site, Kennedy Space Center, Florida, USA. The specimens were subjected to sea water immersion at the test site as a posttreatment exposure. Following a 30-day post-treatment exposure period, the specimens were subjected to indirect tensile testing to evaluate treatment impact. The EN treated specimens exhibited 60% and 30% increases in tensile strength as compared to the untreated controls and ECE treated specimens respectively. The surfaces of the reinforcement bars of the control specimens were 67% covered by corrosion products. In contrast, the EN treated specimens exhibited corrosion coverage of only 4%. Scanning electron microscopy (SEM) revealed a dense concrete microstructure adjacent to the bars of the treated specimens as compared to the control and ECE specimens. Energy dispersive spectroscopic (EDS) analysis of the polished EN treated specimens showed a reduction in chloride content by a factor of 20 adjacent to the bars. This study demonstrated that EN treatment was successful in forming a chloride penetration barrier rapidly. This work also showed that the chloride barrier was effective when samples were exposed to

  9. Nitrogen Index

    USDA-ARS?s Scientific Manuscript database

    There is a need to improve the management of nitrogen inputs to agricultural systems because they increase the potential for losses of reactive nitrogen to the environment, resulting in negative impacts to water and air resources. There is a need to reduce nitrate leaching, emissions of N2O from agr...

  10. Generation of high-current electron beam in a wide-aperture open discharge

    NASA Astrophysics Data System (ADS)

    Bokhan, P. A.; Zakrevsky, Dm. E.; Gugin, P. P.

    2011-10-01

    In the present study, it was examined generation of nanosecond-duration electron-beam (EB) pulses by a wide-aperture open discharge burning in helium or in a mixture of helium with nitrogen and water vapor. In the experiments, a discharge cell with coaxial electrode geometry, permitting radial injection of the electron beam into operating lasing medium, was used, with the cathode having radius 2.5 cm and length 12 cm. It was shown possible to achieve an efficient generation of a high-intensity electron beam (EB pulse power ˜250 MW and EB pulse energy up to 4 J) in the kiloampere range of discharge currents (up to 26 kA at ˜12 kV discharge voltage). The current-voltage characteristics of the discharge proved to be independent of the working-gas pressure. The existence of an unstable dynamic state of EB, conditioned by the presence of an uncompensated space charge accumulated in the discharge cell due to the exponential growth of the current in time during discharge initiation and the hyperbolic growth of current density in the direction towards the tube axis, was revealed. The obtained pulsed electron beam was used to excite the self-terminated laser on He 21P10-21S0 transition. The oscillations developing in the discharge cell at high discharge currents put limit to the pumping energy and emissive power of the laser excited with the radially converging electron beam.

  11. Field electron emission enhancement in lithium implanted and annealed nitrogen-incorporated nanocrystalline diamond films

    NASA Astrophysics Data System (ADS)

    Sankaran, K. J.; Srinivasu, K.; Yeh, C. J.; Thomas, J. P.; Drijkoningen, S.; Pobedinskas, P.; Sundaravel, B.; Leou, K. C.; Leung, K. T.; Van Bael, M. K.; Schreck, M.; Lin, I. N.; Haenen, K.

    2017-06-01

    The field electron emission (FEE) properties of nitrogen-incorporated nanocrystalline diamond films were enhanced due to Li-ion implantation/annealing processes. Li-ion implantation mainly induced the formation of electron trap centers inside diamond grains, whereas post-annealing healed the defects and converted the a-C phase into nanographite, forming conduction channels for effective transport of electrons. This resulted in a high electrical conductivity of 11.0 S/cm and enhanced FEE performance with a low turn-on field of 10.6 V/μm, a high current density of 25.5 mA/cm2 (at 23.2 V/μm), and a high lifetime stability of 1,090 min for nitrogen incorporated nanocrystalline diamond films.

  12. The stability and electronic structures of Si/O/Al/P atom doped (5,0)boron nitrogen nanotubes with Stone-Wales defects: Density functional theory studies

    NASA Astrophysics Data System (ADS)

    Li, KeJing; Ye, JinQian; Zhang, Juan; Wang, XiYuan; Shao, QingYi

    2017-03-01

    Using density functional theory, we have investigated Si/O/Al/P atoms doped (5,0)BNNTs with SW defects. We have mainly found that Si/O/Al/P have improved the stability of (5,0)BNNTs with SW defects. In view of Mulliken charge, we have thought Si/O/Al/P atoms have donated electrons (charge +e state or charge -e state) to nanotubes, contributing BNNTs with SW defects to stable. Meanwhile, from the aspect of energy band structure and DOS, we have further explained the reason. We have considerred that stability of doped structures has related to hybridization between doped atom and BNNTs. The stability has changed with changing the degree of hybridization. Moreover, B atom can play a crucial role in the insertion of Si/O/Al/P atom into (5,0)BNNTs with SW defects.

  13. Electron density change of atmospheric-pressure plasmas in helium flow depending on the oxygen/nitrogen ratio of the surrounding atmosphere

    NASA Astrophysics Data System (ADS)

    Tomita, Kentaro; Urabe, Keiichiro; Shirai, Naoki; Sato, Yuta; Hassaballa, Safwat; Bolouki, Nima; Yoneda, Munehiro; Shimizu, Takahiro; Uchino, Kiichiro

    2016-06-01

    Laser Thomson scattering was applied to an atmospheric-pressure plasma produced in a helium (He) gas flow for measuring the spatial profiles of electron density (n e) and electron temperature (T e). Aside from the He core flow, the shielding gas flow of N2 or synthesized air (\\text{N}2:\\text{O}2 = 4:1) surrounding the He flow was introduced to evaluate the effect of ambient gas components on the plasma parameters, eliminating the effect of ambient humidity. The n e at the discharge center was 2.7 × 1021 m-3 for plasma generated with N2/O2 shielding gas, 50% higher than that generated with N2 shielding.

  14. Reactivity of boron- and nitrogen-doped carbon nanotubes functionalized by (Pt, Eu) atoms toward O2 and CO: A density functional study

    NASA Astrophysics Data System (ADS)

    Abdel Aal, S.

    2016-01-01

    The adsorption behavior and electronic properties of CO and O2 molecules at the supported Pt and Eu atoms on (5,5) armchair SWCNT have been systematically investigated within density functional theory (DFT). Fundamental aspects such as adsorption energy, natural bond orbital (NBO), charge transfer, frontier orbitals and the projected density of states (PDOS) are elucidated to analyze the adsorption properties of CO and O2 molecules. The results reveal that B- and N-doping CNTs can enhance the binding strength and catalytic activity of Pt (Eu) anchored on the doped-CNT, where boron-doping is more effective. The electronic structures of supported metal are strongly influenced by the presence of gases. After adsorption of CO and O2, the changes in binding energy, charge transfer and conductance may lead to the different response in the metal-doped CNT-based sensors. It is expected that these results could provide helpful information for the design and fabrication of the CO and O2 sensing devices. The high catalytic activity of Pt supported at doped-CNT toward the interaction with CO and O2 may be attributed to the electronic resonance particularly among Pt-5d, CO-2π* and O2-2π* antibonding orbitals. In contrast to the supported Eu at doped-CNT, the Eu atom becomes more positively charged, which leads to weaken the CO adsorption and promote the O2 adsorption, consequently enhancing the activity for CO oxidation and alleviating the CO poisoning of the europium catalysts. A notable orbital hybridization and electrostatic interaction between these two species in adsorption process being an evidence of strong interaction. The electronic structure of O2 adsorbed on Eu-doped CNT resembles that of O2-, therefore the transferred charge weakens the O-O bonds and facilitates the dissociation process, which is the precondition for the oxygen reduction reaction (ORR).

  15. Yield and seed oil content response of dwarf, rapid-cycling Brassica to nitrogen treatments, planting density, and carbon dioxide enrichment

    NASA Technical Reports Server (NTRS)

    Frick, J.; Nielsen, S. S.; Mitchell, C. A.

    1994-01-01

    Effects of N level (15 to 30 mM), time of N increase (14 to 28 days after planting), and planting density (1163 to 2093 plants/m2) were determined for crop yield responses of dwarf, rapid-cycling brassica (Brassica napus L., CrGC 5-2, Genome: ACaacc). Crops were grown in solid-matrix hydroponic systems and under controlled-environment conditions, including nonsupplemented (ambient) or elevated CO2 concentrations (998 +/- 12 micromoles mol-1). The highest seed yield rate obtained (4.4 g m-2 day-1) occurred with the lowest N level (15 mM) applied at the latest treatment time (day 28). In all trials, CO2 enrichment reduced seed yield rate and harvest index by delaying the onset of flowering and senescence and stimulating vegetative shoot growth. The highest shoot biomass accumulation rate (55.5 g m-2 day-1) occurred with the highest N level (30 mM) applied at the earliest time (day 14). Seed oil content was not significantly affected by CO2 enrichment. Maximum seed oil content (30% to 34%, dry weight basis) was obtained using the lowest N level (15 mM) initiated at the latest treatment time (day 28). In general, an increase in seed oil content was accompanied by a decrease in seed protein. Seed carbohydrate, moisture, and ash contents did not vary significantly in response to experimental treatments. Effects of N level and time of N increase were consistently significant for most crop responses. Planting density was significant only under elevated CO2 conditions.

  16. Yield and seed oil content response of dwarf, rapid-cycling Brassica to nitrogen treatments, planting density, and carbon dioxide enrichment.

    PubMed

    Frick, J; Nielsen, S S; Mitchell, C A

    1994-11-01

    Effects of N level (15 to 30 mM), time of N increase (14 to 28 days after planting), and planting density (1163 to 2093 plants/m2) were determined for crop yield responses of dwarf, rapid-cycling brassica (Brassica napus L., CrGC 5-2, Genome: ACaacc). Crops were grown in solid-matrix hydroponic systems and under controlled-environment conditions, including nonsupplemented (ambient) or elevated CO2 concentrations (998 +/- 12 micromoles mol-1). The highest seed yield rate obtained (4.4 g m-2 day-1) occurred with the lowest N level (15 mM) applied at the latest treatment time (day 28). In all trials, CO2 enrichment reduced seed yield rate and harvest index by delaying the onset of flowering and senescence and stimulating vegetative shoot growth. The highest shoot biomass accumulation rate (55.5 g m-2 day-1) occurred with the highest N level (30 mM) applied at the earliest time (day 14). Seed oil content was not significantly affected by CO2 enrichment. Maximum seed oil content (30% to 34%, dry weight basis) was obtained using the lowest N level (15 mM) initiated at the latest treatment time (day 28). In general, an increase in seed oil content was accompanied by a decrease in seed protein. Seed carbohydrate, moisture, and ash contents did not vary significantly in response to experimental treatments. Effects of N level and time of N increase were consistently significant for most crop responses. Planting density was significant only under elevated CO2 conditions.

  17. Yield and seed oil content response of dwarf, rapid-cycling Brassica to nitrogen treatments, planting density, and carbon dioxide enrichment

    NASA Technical Reports Server (NTRS)

    Frick, J.; Nielsen, S. S.; Mitchell, C. A.

    1994-01-01

    Effects of N level (15 to 30 mM), time of N increase (14 to 28 days after planting), and planting density (1163 to 2093 plants/m2) were determined for crop yield responses of dwarf, rapid-cycling brassica (Brassica napus L., CrGC 5-2, Genome: ACaacc). Crops were grown in solid-matrix hydroponic systems and under controlled-environment conditions, including nonsupplemented (ambient) or elevated CO2 concentrations (998 +/- 12 micromoles mol-1). The highest seed yield rate obtained (4.4 g m-2 day-1) occurred with the lowest N level (15 mM) applied at the latest treatment time (day 28). In all trials, CO2 enrichment reduced seed yield rate and harvest index by delaying the onset of flowering and senescence and stimulating vegetative shoot growth. The highest shoot biomass accumulation rate (55.5 g m-2 day-1) occurred with the highest N level (30 mM) applied at the earliest time (day 14). Seed oil content was not significantly affected by CO2 enrichment. Maximum seed oil content (30% to 34%, dry weight basis) was obtained using the lowest N level (15 mM) initiated at the latest treatment time (day 28). In general, an increase in seed oil content was accompanied by a decrease in seed protein. Seed carbohydrate, moisture, and ash contents did not vary significantly in response to experimental treatments. Effects of N level and time of N increase were consistently significant for most crop responses. Planting density was significant only under elevated CO2 conditions.

  18. An experimental investigation of cathode erosion in high current magnetoplasmadynamic arc discharges

    NASA Astrophysics Data System (ADS)

    Codron, Douglas A.

    Since the early to mid 1960's, laboratory studies have demonstrated the unique ability of magnetoplasmadynamic (MPD) thrusters to deliver an exceptionally high level of specific impulse and thrust at large power processing densities. These intrinsic advantages are why MPD thrusters have been identified as a prime candidate for future long duration space missions, including piloted Mars, Mars cargo, lunar cargo, and other missions beyond low Earth orbit (LEO). The large total impulse requirements inherent of the long duration space missions demand the thruster to operate for a significant fraction of the mission burn time while requiring the cathodes to operate at 50 to 10,000 kW for 2,000 to 10,000 hours. The high current levels lead to high operational temperatures and a corresponding steady depletion of the cathode material by evaporation. This mechanism has been identified as the life-limiting component of MPD thrusters. In this research, utilizing subscale geometries, time dependent cathode axial temperature profiles under varying current levels (20 to 60 A) and argon gas mass flow rates (450 to 640 sccm) for both pure and thoriated solid tungsten cathodes were measured by means of both optical pyrometry and charged-coupled (CCD) camera imaging. Thoriated tungsten cathode axial temperature profiles were compared against those of pure tungsten to demonstrate the large temperature reducing effect lowered work function imparts by encouraging increased thermionic electron emission from the cathode surface. Also, Langmuir probing was employed to measure the electron temperature, electron density, and plasma potential near the "active zone" (the surface area of the cathode responsible for approximately 70% of the emitted current) in order to characterize the plasma environment and verify future model predictions. The time changing surface microstructure and elemental composition of the thoriated tungsten cathodes were analyzed using a scanning electron microscope

  19. Influence of pulse line switch inductance on output characteristics of high-current nanosecond accelerators

    NASA Astrophysics Data System (ADS)

    Mashchenko, A. I.; Vintizenko, I. I.

    2016-06-01

    Various types of high-current nanosecond accelerators are simulated numerically using an equivalent circuit representation. The influence of pulse forming line switch inductance on the amplitude and waveform of output voltage and current pulses is analyzed.

  20. Nitrogen-enriched, double-shelled carbon/layered double hydroxide hollow microspheres for excellent electrochemical performance

    NASA Astrophysics Data System (ADS)

    Xu, Jie; He, Fei; Gai, Shili; Zhang, Shenghuan; Li, Lei; Yang, Piaoping

    2014-08-01

    A unique, double-shelled, hollow, carbon-based composite with enriched nitrogen has been prepared through a facile and versatile synthetic strategy. The hierarchical composite employs the nitrogen-enriched carbon hollow sphere as an interior shell and intercrossed Ni/Al layered double hydroxide (LDH) nanosheets as an exterior shell. The obtained N-C@LDH hollow microspheres (HMS) have high nitrogen enrichment, large specific surface area (337 m2 g-1), and uniform and open mesoporous structure. Taking advantage of these characteristics, the composite exhibits obviously superior capacitive behavior, including high specific capacitance, excellent rate capability and good cycling stability, compared with nitrogen-free carbon@LDH composite and hollow LDH without carbon shell. The composite displays high specific capacitance of 1711.51 F g-1 at a current density of 1 A g-1. In particular, the high specific capacitance can be kept to 997.3 F g-1 at a high current density of 10 A g-1, which still retains 94.97% of the initial specific capacitance after 500 cycles at this high current density. This N-enriched, hollow carbon/LDH composite can be expected to be a promising electrode material for electrochemical capacitors due to its high electrochemical performance.A unique, double-shelled, hollow, carbon-based composite with enriched nitrogen has been prepared through a facile and versatile synthetic strategy. The hierarchical composite employs the nitrogen-enriched carbon hollow sphere as an interior shell and intercrossed Ni/Al layered double hydroxide (LDH) nanosheets as an exterior shell. The obtained N-C@LDH hollow microspheres (HMS) have high nitrogen enrichment, large specific surface area (337 m2 g-1), and uniform and open mesoporous structure. Taking advantage of these characteristics, the composite exhibits obviously superior capacitive behavior, including high specific capacitance, excellent rate capability and good cycling stability, compared with nitrogen

  1. High-voltage, high-current, solid-state closing switch

    DOEpatents

    Focia, Ronald Jeffrey

    2017-08-22

    A high-voltage, high-current, solid-state closing switch uses a field-effect transistor (e.g., a MOSFET) to trigger a high-voltage stack of thyristors. The switch can have a high hold-off voltage, high current carrying capacity, and high time-rate-of-change of current, di/dt. The fast closing switch can be used in pulsed power applications.

  2. Caballero: A High Current Flux Compressor System for 100 MJ Solid Liner Experiments

    DTIC Science & Technology

    1997-06-01

    Caballero : A High Current Flux Compressor System For 100 MJ Solid Liner Experiments" R. E. Reinovsky, I.R. Lindemuth, E. A Lopez J.H. Goforth, S. P...currently valid OMB control number. 1. REPORT DATE JUN 1997 2. REPORT TYPE N/A 3. DATES COVERED - 4. TITLE AND SUBTITLE Caballero : A High Current...To initially explore the performance of the Disk Explosive Magnetic Generator (DEMG), a system ( Caballero -40) was designed with a module diameter of

  3. Self-assembled, aligned ZnO nanorod buffer layers for high-current-density, inverted organic photovoltaics.

    PubMed

    Rao, Arun D; Karalatti, Suresh; Thomas, Tiju; Ramamurthy, Praveen C

    2014-10-08

    Two different soft-chemical, self-assembly-based solution approaches are employed to grow zinc oxide (ZnO) nanorods with controlled texture. The methods used involve seeding and growth on a substrate. Nanorods with various aspect ratios (1-5) and diameters (15-65 nm) are grown. Obtaining highly oriented rods is determined by the way the substrate is mounted within the chemical bath. Furthermore, a preheat and centrifugation step is essential for the optimization of the growth solution. In the best samples, we obtain ZnO nanorods that are almost entirely oriented in the (002) direction; this is desirable since electron mobility of ZnO is highest along this crystallographic axis. When used as the buffer layer of inverted organic photovoltaics (I-OPVs), these one-dimensional (1D) nanostructures offer: (a) direct paths for charge transport and (b) high interfacial area for electron collection. The morphological, structural, and optical properties of ZnO nanorods are studied using scanning electron microscopy, X-ray diffraction, and ultraviolet-visible light (UV-vis) absorption spectroscopy. Furthermore, the surface chemical features of ZnO films are studied using X-ray photoelectron spectroscopy and contact angle measurements. Using as-grown ZnO, inverted OPVs are fabricated and characterized. For improving device performance, the ZnO nanorods are subjected to UV-ozone irradiation. UV-ozone treated ZnO nanorods show: (i) improvement in optical transmission, (ii) increased wetting of active organic components, and (iii) increased concentration of Zn-O surface bonds. These observations correlate well with improved device performance. The devices fabricated using these optimized buffer layers have an efficiency of ∼3.2% and a fill factor of 0.50; this is comparable to the best I-OPVs reported that use a P3HT-PCBM active layer.

  4. Development of superconductors for applications in high-field, high-current-density magnets for fusion research

    SciTech Connect

    Summers, L.T.; Miller, J.R.

    1986-09-26

    The development of large-bore, high-field magnets for fusion energy applications requires a system approach to both magnet and conductor design. At Lawrence Livermore National Laboratory (LLNL), the criteria used to choose superconductors include: strain tolerance, radiation tolerance, heat removal, stability, fabricability, and cost. We report on the performance of industrially produced, prototype, Ti-modified Nb/sub 3/Sn wires developed with LLNL support. Wire performance characteristics evaluated include critical current as a function of magnetic field, temperature, and applied strain. Tests were performed to determine how this performance translates to the performance of a cable-in-conduit conductor system using this wire. An alternative to Nb/sub 3/Sn superconductors is NbN, which is strain and radiation insensitive. We report preliminary efforts to produce multifilamentary NbN conductors by liquid-metal infiltration of NbN-coated, high-strength fibers. In addition, we discuss the fabrication of multifilamentary NbN conductors and their possible impact on magnet design.

  5. Photoelectrolysis of water at high current density - Use of laser light excitation of semiconductor-based photoelectrochemical cells

    NASA Technical Reports Server (NTRS)

    Wrighton, M. S.; Bocarsley, A. B.; Bolts, J. M.

    1978-01-01

    In the present paper, some results are given for UV laser light irradiation of the photoanode (SnO2, SrTiO3, or TiO2) in a cell for the light-driven electrolysis of H2O, at radiation intensities of up to 380 W/sq cm. The properties of the anode material are found to be independent of light intensity. Conversion of UV light to stored chemical energy in the form of 2H2/O2 from H2O was driven at a rate of up to 30 W/sq cm. High O2 evolution rates at the irradiated anodes without changes in the current-voltage curves are attributed to the excess oxidizing power associated with photogenerated holes. A test for this sort of hypothesis for H2 evolution at p-type materials is proposed.

  6. Photoelectrolysis of water at high current density - Use of laser light excitation of semiconductor-based photoelectrochemical cells

    NASA Technical Reports Server (NTRS)

    Wrighton, M. S.; Bocarsley, A. B.; Bolts, J. M.

    1978-01-01

    In the present paper, some results are given for UV laser light irradiation of the photoanode (SnO2, SrTiO3, or TiO2) in a cell for the light-driven electrolysis of H2O, at radiation intensities of up to 380 W/sq cm. The properties of the anode material are found to be independent of light intensity. Conversion of UV light to stored chemical energy in the form of 2H2/O2 from H2O was driven at a rate of up to 30 W/sq cm. High O2 evolution rates at the irradiated anodes without changes in the current-voltage curves are attributed to the excess oxidizing power associated with photogenerated holes. A test for this sort of hypothesis for H2 evolution at p-type materials is proposed.

  7. Leaf conductance in relation to rate of CO/sub 2/ assimilation. I. Influence of nitrogen nutrition, phosphorus nutrition, photon flux density, and ambient partial pressure of CO/sub 2/ during ontogeny. [Zea mays

    SciTech Connect

    Wong, S.C.; Cowan, I.R.; Farquhar, G.D.

    1985-01-01

    Plants of Zea mays were grown with different concentrations of nitrate (0.6, 4, 12, and 24 millimolar) and phosphate (0.04, 0.13, 0.53, and 1.33 millimolar) supplied to the roots, photon flux densities (0.04, 0.13, 0.53, and 1.33 millimolar) supplied to the roots, photon flux densities (0.12, 0.5, and 2 millimoles per square meter per second), and ambient partial pressures of CO/sub 2/ (305 and 610 microbars). Differences in mineral nutrition and irradiance led to a large variation in rate of CO/sub 2/ assimilation per unit leaf area (A, 11 to 58 micromoles per square meter per second) when measured under standard conditions. The variation was shown, with the plants that had received different amounts of nitrate, to be related to variations in the nitrogen and chlorophyll contents, and phosphoenolpyruvate and ribulose-1,5-bisphosphate carboxylase activities per unit leaf area. Irrespective of growth treatment, A and leaf conductance to CO/sub 2/ transfer (g), measured under standard conditions were in almost constant proportion, implying that intercellular partial pressure of CO/sub 2/ (p/sub i/), was almost constant at 95 microbars. The same proportionality was maintained as A and g increased in an initially nitrogen-deficient plant that had been supplied with abundant nitrate. It was shown that p/sub i/ measured at a given ambient partial pressure was not affected by the ambient partial pressure at which the plants had been grown, although it was different when measured at different ambient partial pressures. This suggests that the close coupling between A and g in these experiments is not associated with sensitivity of stomata to change in p/sub i/. Similar, though less comprehensive, experiments were done with Gosypium hirsutum, and yielded similar conclusions, except that the proportionality between A and g at normal ambient partial pressure of CO/sub 2/ implied p/sub i/ approx. = 200 microbars. 11 references, 6 figures, 1 table.

  8. Research of transportation efficiency of low-energy high- current electron beam in plasma channel in external magnetic field

    NASA Astrophysics Data System (ADS)

    Vagin, E. S.; Grigoriev, V. P.

    2015-11-01

    Effective high current (5-20 kA) and low energy (tens of keV) electrons beam transportation is possible only with almost complete charging neutralization. It is also necessary to use quite high current neutralization for elimination beam self-pinching effect. The research is based on the self-consistent mathematical model that takes into account beam and plasma particles dynamic, current and charge neutralization of electron beam and examines the transportation of electron beam into a chamber with low-pressure plasma in magnetic field. A numerical study was conducted using particle in cell (PIC) method. The study was performed with various system parameters: rise time and magnitude of the beam current, gas pressure and plasma density and geometry of the system. Regularities of local virtual cathode field generated by the beam in the plasma channel, as well as ranges of parameters that let transportation beam with minimal losses, depending on the external magnetic field were determined through a series of numerical studies. In addition, the assessment of the impact of the plasma ion mobility during the transition period and during steady beam was performed.

  9. High energy density electrochemical cell

    NASA Technical Reports Server (NTRS)

    Byrne, J. J.; Williams, D. L.

    1970-01-01

    Primary cell has an anode of lithium, a cathode containing dihaloisocyanuric acid, and a nonaqueous electrolyte comprised of a solution of lithium perchlorate in methyl formate. It produces an energy density of 213 watt hrs/lb and can achieve a high current density.

  10. High-Current Experiments for Accelerator-Based Neutron Capture Therapy Applications

    SciTech Connect

    Gierga, D.P.; Klinkowstein, R.E.; Hughey, B.H.; Shefer, R.E.; Yanch, J.C.; Blackburn, B.W.

    1999-06-06

    Several accelerator-based neutron capture therapy applications are under development. These applications include boron neutron capture therapy for glioblastoma multiform and boron neutron capture synovectomy (BNCS) for rheumatoid arthritis. These modalities use accelerator-based charged-particle reactions to create a suitable neutron source. Neutrons are produced using a high-current, 2-MV terminal tandem accelerator. For these applications to be feasible, high accelerator beam currents must be routinely achievable. An effort was undertaken to explore the operating regime of the accelerator in the milliampere range. In preparation for high-current operation of the accelerator, computer simulations of charged-particle beam optics were performed to establish high-current operating conditions. Herein we describe high beam current simulations and high beam current operation of the accelerator.

  11. Densities and temperatures in the polar thermosphere

    NASA Technical Reports Server (NTRS)

    Gardner, L. J.

    1977-01-01

    The atomic oxygen density at 120 km, the 630 nm airglow temperature, the helium density at 300 km and the molecular nitrogen density near 400 km were examined as functions of geomagnetic latitude, geomagnetic time, season and magnetic activity level. The long-term averages of these quantities were examined so as to provide a baseline of these thermospheric parameters from which future studies may be made for comparison. The hours around magnetic noon are characterized by low temperatures, high 0 and He densities, and median nitrogen densities. The pre-midnight hours exhibit high temperatures, high He density, low nitrogen density and median 0 densities. The post-midnight sector shows low 0 and He densities, median temperatures and high nitrogen densities. These results are compared to recent models and observations and are discussed with respect to their causes due to divergence of the wind field and energy deposition in the thermosphere.

  12. Wear resistance improvement of a commercially pure titanium by high current pulsed electron beam treatment

    NASA Astrophysics Data System (ADS)

    Zhang, Xiangdong; Wang, Xiaoying; Li, Fangfang; Xiao, Hong

    2017-03-01

    A commercially pure titanium was selected as target material and treated by high current pulsed electron beam. The phase and structure changes occurring in the modified surface layers were observed with optical microscopy, scanning electron microscope, and transmission electron microscope. The increase in the wear resistance was observed for the pure titanium samples after pulsed electron beam surface melting. The mechanism for wear resistance modification was discussed. The results indicated that the presence of ultrafine martensite and defects in the treated surface layer were key factors for the improvement of the wear properties of pure titanium treated by high current pulsed beam treatment.

  13. SRRC/ANL high current l-band single cell photocathode rf gun.

    SciTech Connect

    Ho, C. H.

    1998-07-16

    A high current L-band photocathode rf gun is under development at SRRC (Synchrotron Radiation Research Center, Taiwan) in collaboration with ANL (Argonne National Laboratory, USA). The goal is to produce up to 100 nC charge with the surface field gradient of over 90 MV/m at the center of the photocathode. In this report, they present the detailed design and initial test results. If successful, this gun will be used as the future AWA (Argonne Wakefield Accelerator)[1] high current gun.

  14. Low-temperature preparation of GaN-SiO2 interfaces with low defect density. II. Remote plasma-assisted oxidation of GaN and nitrogen incorporation

    NASA Astrophysics Data System (ADS)

    Bae, Choelhwyi; Lucovsky, Gerald

    2004-11-01

    Low-temperature remote plasma-assisted oxidation and nitridation processes for interface formation and passivation have been extended from Si and SiC to GaN. The initial oxidation kinetics and chemical composition of thin interfacial oxide were determined from analysis of on-line Auger electron spectroscopy features associated with Ga, N, and O. The plasma-assisted oxidation process is self-limiting with power-law kinetics similar to those for the plasma-assisted oxidation of Si and SiC. Oxidation using O2/He plasma forms nearly pure GaOx, and oxidation using 1% N2O in N2 forms GaOxNy with small nitrogen content, ~4-7 at. %. The interface and dielectric layer quality was investigated using fabricated GaN metal-oxide-semiconductor capacitors. The lowest density of interface states was achieved with a two-step plasma-assisted oxidation and nitridation process before SiO2 deposition.

  15. Melting line of polymeric nitrogen

    NASA Astrophysics Data System (ADS)

    Yakub, L. N.

    2013-05-01

    We made an attempt to predict location of the melting line of polymeric nitrogen using two equations for Helmholtz free energy: proposed earlier for cubic gauche-structure and developed recently for liquid polymerized nitrogen. The P-T relation, orthobaric densities and latent heat of melting were determined using a standard double tangent construction. The estimated melting temperature decreases with increasing pressure, alike the temperature of molecular-nonmolecular transition in solid. We discuss the possibility of a triple point (solid-molecular fluid-polymeric fluid) at ˜80 GPa and observed maximum of melting temperature of nitrogen.

  16. High current electric arcs above the In-Ga-Sn eutectic alloy

    NASA Astrophysics Data System (ADS)

    Klementyeva, I. B.; Pinchuk, M. E.

    2016-11-01

    The results of investigations of high-current dc and ac arc discharges of atmospheric pressure emerging above the free surface of liquid metal (In-Ga-Sn eutectic alloy) are presented in the paper. The mechanism of the arc formation due to pinch-effect is discussed here.

  17. Nitrogen dioxide

    Integrated Risk Information System (IRIS)

    Nitrogen dioxide ; CASRN 10102 - 44 - 0 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogeni

  18. Spatial and Time Dynamics of Non-Linear Vortices in Plasma Lens for High-Current Ion Beam Focusing

    NASA Astrophysics Data System (ADS)

    Goncharov, Alexei A.; Maslov, Vasyl I.; Onishchenko, Ivan N.; Tretyakov, Vitalij N.

    2002-11-01

    It is known from numerical simulation (see, for example, [1]) and from experiments (see, for example, [2]), that an electron density bunches as discrete vortices are long - living structures in vacuum. However, in laboratory experiments [2] it has been shown that the vortices are changed faster, when they are submersed in electrons, distributed around them. The charged plasma lens intended for a focussing of high-current ion beams, has the same crossed configuration of a radial electrical and longitudinal magnetic field [3], as only electron plasma. In this lens the vortical turbulence is excited [3]. The vortex - bunch and vortex - hole are rotated in the inverse directions in system of their rest. The instability development in initially homogeneous plasma causes that the vortices are excited by pairs. Namely, if the vortex - bunch of electrons is generated, near the vortex - hole of electrons is also generated. It is shown, that in nonuniform plasma the vortices behave is various in time. Namely, the vortex - bunch goes to area of larger electron density, and the vortex - hole goes to area of smaller electron density. The speed of the vortex - hole is less than speed of the vortex - bunch. It is shown, that the electron vortices, generated in the plasma lens, can result in to formation of spiral distribution of electron density. The physical mechanism of coalescence of electron vortices - bunches is proposed. 1.Driscoll C.F. et al. Plasma Phys. Contr. Fus. Res. 3 (1989) 507. 2.Kiwamoto Y. et al. Non-neutral plasma physics. Princeton. 1999. P. 99-105. 3.Goncharov A. et al. Plasma Phys. Rep. 20 (1994) 499.

  19. Trial manufacture of liquid nitrogen cooling High Temperature Superconductivity Motor

    NASA Astrophysics Data System (ADS)

    Sugimoto, H.; Nishikawa, T.; Tsuda, T.; Hondou, Y.; Akita, Y.; Takeda, T.; Okazaki, T.; Ohashi, S.; Yoshida, Y.

    2006-06-01

    We present a new high temperature superconductivity (HTS) synchronous motor using the liquid nitrogen as the refrigerant in this paper. This motor is designed to be used as the propulsion motor in ship. Because we use the liquid nitrogen as the refrigerant, it is possible to simplify the cooling equipments in the motor. And in our design, we apply the axial flux type of motor to simplify the cryostat of the HTS wires used to make the field coils. Here, the fields using the bismuth HTS wire for the HTS coils are fixed. Moreover, the cores used in the fields are separated from cryostat, and the armature applies the core-less structure. According to various the electromagnetic field analysis results, the new motor was designed and produced. The diameter of the motor is 650mm, and the width of the motor is 360mm. The motor's rated output is 8.8kW at 100rpm, while the overload output is 44kW, and the maximum efficiency is 97.7%. Also, in order to further miniaturize the motor, other magnetic field analysis have been done when the high-current-density type HTS wire was used and the permendur was used instead of magnetic steel plates. In this case, the motor's rated output is 12kW, and the overload output is 60kW.

  20. Atomic nitrogen measurements in the upper thermosphere

    NASA Technical Reports Server (NTRS)

    Mauersberger, K.; Engebretson, M. J.; Potter, W. E.; Kayser, D. C.; Nier, A. O.

    1977-01-01

    The open source neutral mass spectrometer on board the Atmosphere Explorer satellites measures, besides other neutral constituents, atomic nitrogen densities in the upper thermosphere. Atomic nitrogen combines with atomic oxygen on the walls of the mass spectrometer ion source to form NO. From the measured NO concentration atomic nitrogen is deduced. Studies of the diurnal variation show that the maximum atomic nitrogen densities occur near 1600 local solar time (LST) and minimum densities near 0400 LST. The diurnal amplitude at 300 km is about a factor of 8, which is lower than predicted in present models. Atomic nitrogen also exhibits a pronounced seasonal variation with an amplitude similar to that of the diurnal variation; summer values are considerably higher than winter ones.

  1. Investigations of a high current linear aperture radial multichannel pseudospark switch.

    PubMed

    Lamba, R P; Pathania, V; Meena, B L; Rahaman, H; Pal, U N; Prakash, Ram

    2015-10-01

    In this paper, a high current linear aperture radial multichannel Pseudospark switch (LARM-PSS) is reported which has been analyzed for its high current characteristics. In order to enhance hold-off voltage and support hollow cathode effect for the ignition of the discharge in this configuration, the field penetration analysis through circular and linear apertures of the electrodes has been carried out. The linear apertures in the electrodes increase the current handling capacity than that of circular aperture electrodes without significant compromise of the hold-off capacity. The developed LARM-PSS switch is capable to hold voltage up to 25 kV at gas pressure between 10 and 50 Pa for hydrogen. The switch has been operated using a 800 nF capacitor bank and conducted an effective charge up to 1.5 C with peak switch current ∼20 kA at applied voltage 19 kV.

  2. Status of high current ion source operation at the GSI accelerator facility.

    PubMed

    Hollinger, R; Galonska, M; Gutermuth, B; Heymach, F; Krichbaum, H; Leible, K-D; Ochs, K; Schäffer, P; Schäffer, S; Spädtke, P; Stork, M; Wesp, A; Mayr, R

    2008-02-01

    Vacuum arc ion sources, Penning ion sources, and filament driven multicusp ion sources are used for the production of high current ion beams of a variety of metallic and gaseous ions at the GSI accelerator facility. For accelerator operation, the ion sources have to provide a stable beam over a long period of time with an energy of 2.2 keV/u and a maximum mass over charge ratio of 65. The status of beam time operation at the high current injector is presented here giving an outline on important ion source data, such as ion beam current, ion beam spectrum, transversal emittance, life time, duty factor, and transmission along the low energy beam transport section.

  3. Status of high current ion source operation at the GSI accelerator facility

    SciTech Connect

    Hollinger, R.; Galonska, M.; Gutermuth, B.; Heymach, F.; Krichbaum, H.; Leible, K.-D.; Ochs, K.; Schaeffer, P.; Schaeffer, S.; Spaedtke, P.; Stork, M.; Wesp, A.; Mayr, R.

    2008-02-15

    Vacuum arc ion sources, Penning ion sources, and filament driven multicusp ion sources are used for the production of high current ion beams of a variety of metallic and gaseous ions at the GSI accelerator facility. For accelerator operation, the ion sources have to provide a stable beam over a long period of time with an energy of 2.2 keV/u and a maximum mass over charge ratio of 65. The status of beam time operation at the high current injector is presented here giving an outline on important ion source data, such as ion beam current, ion beam spectrum, transversal emittance, life time, duty factor, and transmission along the low energy beam transport section.

  4. MIDOT: A novel probe for monitoring high-current flat transmission lines

    NASA Astrophysics Data System (ADS)

    Omar, K.; Novac, B. M.; Graneau, N.; Senior, P.; Smith, I. R.; Sinclair, M.

    2016-12-01

    A novel inductive probe, termed MIDOT, was developed for monitoring high-current flat transmission lines. While being inexpensive the probe does not require calibration, is resistant to both shock waves and temperature variations, and it is easy to manufacture and mount. It generates strong output signals that are relatively easy to interpret and has a detection region limited to a pre-defined part of the transmission line. The theoretical background related to the MIDOT probes, together with their practical implementation in both preliminary experimentation and high-current tests, is also presented in the paper. The novel probe can be used to benchmark existing 2D numerical codes used in calculating the current distribution inside the conductors of a transmission line but can also easily detect an early movement of a transmission line component. The probe can also find other applications, such as locating the position of a pulsed current flowing through a thin wire.

  5. Status of high current ion source operation at the GSI accelerator facilitya)

    NASA Astrophysics Data System (ADS)

    Hollinger, R.; Galonska, M.; Gutermuth, B.; Heymach, F.; Krichbaum, H.; Leible, K.-D.; Ochs, K.; Schäffer, P.; Schäffer, S.; Spädtke, P.; Stork, M.; Wesp, A.; Mayr, R.

    2008-02-01

    Vacuum arc ion sources, Penning ion sources, and filament driven multicusp ion sources are used for the production of high current ion beams of a variety of metallic and gaseous ions at the GSI accelerator facility. For accelerator operation, the ion sources have to provide a stable beam over a long period of time with an energy of 2.2keV/u and a maximum mass over charge ratio of 65. The status of beam time operation at the high current injector is presented here giving an outline on important ion source data, such as ion beam current, ion beam spectrum, transversal emittance, life time, duty factor, and transmission along the low energy beam transport section.

  6. Investigations of a high current linear aperture radial multichannel pseudospark switch

    NASA Astrophysics Data System (ADS)

    Lamba, R. P.; Pathania, V.; Meena, B. L.; Rahaman, H.; Pal, U. N.; Prakash, Ram

    2015-10-01

    In this paper, a high current linear aperture radial multichannel Pseudospark switch (LARM-PSS) is reported which has been analyzed for its high current characteristics. In order to enhance hold-off voltage and support hollow cathode effect for the ignition of the discharge in this configuration, the field penetration analysis through circular and linear apertures of the electrodes has been carried out. The linear apertures in the electrodes increase the current handling capacity than that of circular aperture electrodes without significant compromise of the hold-off capacity. The developed LARM-PSS switch is capable to hold voltage up to 25 kV at gas pressure between 10 and 50 Pa for hydrogen. The switch has been operated using a 800 nF capacitor bank and conducted an effective charge up to 1.5 C with peak switch current ˜20 kA at applied voltage 19 kV.

  7. A High-Gradient CW R Photo-Cathode Electron Gun for High Current Injectors

    SciTech Connect

    Robert Rimmer

    2005-05-01

    The paper describes the analysis and preliminary design of a high-gradient photo-cathode RF gun optimized for high current CW operation. The gun cell shape is optimized to provide maximum acceleration for the newly emitted beam while minimizing wall losses in the structure. The design is intended for use in future high-current high-power CW FELs but the shape optimization for low wall losses may be advantageous for other applications such as XFELs or Linear Colliders using high peak power low duty factor guns where pulse heating is a limitation. The concept allows for DC bias on the photocathode in order to repel ions and improve cathode lifetime.

  8. Progress on the high-current 704 MHz superconducting RF cavity at BNL

    SciTech Connect

    Xu W.; Astefanous, C.; Belomestnykh, S.; Ben-Zvi, I.; et al

    2012-05-20

    The 704 MHz high current superconducting cavity has been designed with consideration of both performance of fundamental mode and damping of higher order modes. A copper prototype cavity was fabricated by AES and delivered to BNL. RF measurements were carried out on this prototype cavity, including fundamental pass-band and HOM spectrum measurements, HOM studies using bead-pull setup, prototyping of antenna-type HOM couplers. The measurements show that the cavity has very good damping for the higher-order modes, which was one of the main goals for the high current cavity design. 3D cavity models were simulated with Omega3P code developed by SLAC to compare with the measurements. The paper describes the cavity design, RF measurement setups and results for the copper prototype. The progress with the niobium cavity fabrication will also be described.

  9. Enhanced D-T supershot performance at high current using extensive lithium conditioning in TFTR

    SciTech Connect

    Mansfield, D.K.; Strachan, J.D.; Bell, M.G.; Scott, S.D.; Budny, R.; Bell, R.E.; Bitter, M.; Darrow, D.S.; Fredrickson, E.; Grek, B.

    1995-05-01

    A substantial improvement in supershot fusion plasma performance has been realized by combining the enhanced confinement due to tritium fueling with the enhanced confinement due to extensive Li conditioning of the TFTR limiter. This combination has resulted in not only significantly higher global energy confinement times than had previously been obtained in high current supershots, but also the highest ratio of central fusion output power to input power observed to date.

  10. Longitudinal and Transverse Instabilities in a High Current Modified Betatron Electron Accelerator.

    DTIC Science & Technology

    1984-05-17

    Conlinuod) image charges and currents on the toroidal chamber walls. The electron ring, which is assumed to have an energy spread, is taken to be located...We find an unstable hybrid mode of oscillation which is a coupled azimuthal and longitudinal mode and exists at beam energies below the transition... energy . The negative mass/kink instability associated with an ultra high current (I - 10 kA) modified beta- tron electron accelerator is analyzed and

  11. New computer control system for the high current ion implanter PR-80

    NASA Astrophysics Data System (ADS)

    Sunouchi, T.; Sasaki, M.; Sato, S.; Harada, M.

    1989-02-01

    For a current semiconductor fabrication line, an ion implanter should have the versatility to handle different types of process menus and it should be FA compatible. An optical loopway linked microprocessor control system has been developed for our high current ion implanter. The system is compatible with SECS-II, and its preventive maintenance program is a powerful tool for efficient operation of the implanter.

  12. Conversion of high explosive chemical energy into energy of powerful nanosecond high-current pulses

    NASA Astrophysics Data System (ADS)

    Gorbachev, K. V.; Mikhaylov, V. M.; Nesterov, E. V.; Stroganov, V. A.; Chernykh, E. V.

    2015-01-01

    This study is a contribution into the development of physicotechnical foundations for generation of powerful nanosecond high-current pulses on the basis of explosively driven magnetic flux compression generators. This problem is solved by using inductive storage of energy for matching comparatively low-voltage explosively driven magnetic flux compression generators and high-impedance loads; short forming lines and vacuum diodes. Experimental data of charging of forming lines are given.

  13. A mechanical connector design for high-current, high-coulomb pulsed power systems

    SciTech Connect

    Susoeff, A.R.; Hawke, R.S.; Leighton, K.S.

    1992-02-25

    A technique to make reliable high-current, high-coulomb electrical contact was developed for transmitting power into railguns. The method uses spring loaded removable connectors that are installed independently from the launcher. The simple rod-type design and absence of fastener holes allow maximum utilization of material mechanical properties. Repeated experiments with 9.5-mm diameter connectors demonstrated reliable pulsed charge transfer of 200 coulombs at currents of over 400kA. 20 refs.

  14. Influence of the Thomson effect on the pulse heating of high-current electrical contacts

    NASA Astrophysics Data System (ADS)

    Merkushev, A. G.; Pavleino, M. A.; Pavleino, O. M.; Pavlov, V. A.

    2014-09-01

    Pulse heating of high-current contacts is notable for the presence of considerable temperature gradients in the contact area, which cause the Thomson effect—the appearance of thermoelectric currents. The amount of this effect against conventional Joule heat release is quantitatively estimated. Pulse heating of electrical contacts is numerically simulated with the use of the Comsol program package. It is demonstrated that thermoelectric currents make a negligible contribution to heating in the case of copper contacts.

  15. High-power Čerenkov microwave oscillators utilizing High-Current nanosecond Electron beams

    NASA Astrophysics Data System (ADS)

    Korovin, S. D.; Polevin, S. D.; Rostov, V. V.

    1996-12-01

    A short review is given of results obtained at the Institute of High-Current Electronics of the Siberian Branch of the Russian Academy of Sciences on generating high-power microwave radiation. Most of the research was devoted to a study of stimulated Čerenkov radiation from relativistic electron beams. It is shown that the efficiency of a relativistic 3-cm backward wave tube with a nonuniform coupling resistance can reach 35%. High-frequency radiation was discovered in the emission spectrum of the Čerenkov oscillators and it was shown that the nature of the radiation was associated with the stimulated scattering of low-frequency radiation by the relativistic electrons. Radiation with a power of 500 MW was obtained in the 8-mm wavelength range using a two-beam Čerenkov oscillator. High-current pulse-periodic nanosecond accelerators with a charging device utilizing a Tesla transformer were used in the experiments. The possibility was demonstrated of generating high-power microwave radiation with a pulse-repetition frequency of up to 100 Hz. An average power of ˜500 W was achieved from the relativistic oscillators. A relativistic backward wave tube with a high-current electron beam was used to make a prototype nanosecond radar device. Some of the results presented were obtained jointly with the Russian Academy of Sciences Institute of Applied Physics. Questions concerning multiwave Čerenkov interaction are not considered in this paper.

  16. Beam Dynamics Aspects of High Current Beams in a Superconducting Proton Linac

    NASA Astrophysics Data System (ADS)

    Bellomo, Giovanni; Pagani, Carlo; Pierini, Paolo

    1997-05-01

    High current CW proton linac accelerators have been recently proposed for nuclear waste transmutation and concurrent energy production. In most of the designs the high energy part (100 MeV up to 1-2 GeV) of the linac employs low frequency superconducting structures (352-700 MHz). Here we present beam dynamics issues for the high current (10-50 mA) beams in the superconducting section of such an accelerator, based on 352 MHz β-graded, LEP style cavities, as proposed at Linac 96(C. Pagani, G. Bellomo, P. Pierini, ``A High Current Proton Linac with 352 MHz SC Cavities'', Proceedings of the XVIII Int. Linear Acc. Conf., eds. C. Hill, M. Vretenar, CERN 96-07, 15 November 1996). In particular, smooth beam propagation along the linac has been reached with decreasing phase advances along the linac, and the design has been updated to match the beam dynamics results. Mismatching oscillations are discussed, as they are considered to cause beam halo and, consequently, beam losses.

  17. A new method of rapid power measurement for MW-scale high-current particle beams

    NASA Astrophysics Data System (ADS)

    Xu, Yongjian; Hu, Chundong; Xie, Yuanlai; Liu, Zhimin; Xie, Yahong; Liu, Sheng; Liang, Lizheng; Jiang, Caichao; Sheng, Peng; Yu, Ling

    2015-09-01

    MW-scale high current particle beams are widely applied for plasma heating in the magnetic confinement fusion devices, in which beam power is an important indicator for efficient heating. Generally, power measurement of MW-scale high current particle beam adopts water flow calorimetry (WFC). Limited by the principles of WFC, the beam power given by WFC is an averaged value. In this article a new method of beam power for MW-scale high-current particle beams is introduced: (1) the temperature data of thermocouples embedded in the beam stopping elements were obtained using high data acquire system, (2) the surface heat flux of the beam stopping elements are calculated using heat transfer, (3) the relationships between positions and heat flux were acquired using numerical simulation, (4) the real-time power deposited on the beam stopping elements can be calculated using surface integral. The principle of measurement was described in detail and applied to the EAST neutral beam injector for demonstration. The result is compared with that measured by WFC. Comparison of the results shows good accuracy and applicability of this measuring method.

  18. The high current, fast, 100ns, Linear Transformer Driver (LTD) developmental project at Sandia National Laboratories.

    SciTech Connect

    Ward, Kevin S.; Long, Finis W.; Sinebryukhov, Vadim A. , Tomsk, Russia); Kim, Alexandre A. , Tomsk, RUSSIA); Wakeland, Peter Eric; McKee, G. Randall; Woodworth, Joseph Ray; McDaniel, Dillon Heirman; Fowler, William E.; Mazarakis, Michael Gerrassimos; Porter, John Larry, Jr.; Struve, Kenneth William; Stygar, William A.; LeChien, Keith R.; Matzen, Maurice Keith

    2010-04-01

    Sandia National Laboratories, Albuquerque, N.M., USA, in collaboration with the High Current Electronic Institute (HCEI), Tomsk, Russia, is developing a new paradigm in pulsed power technology: the Linear Transformer Driver (LTD) technology. This technological approach can provide very compact devices that can deliver very fast high current and high voltage pulses straight out of the cavity with out any complicated pulse forming and pulse compression network. Through multistage inductively insulated voltage adders, the output pulse, increased in voltage amplitude, can be applied directly to the load. The load may be a vacuum electron diode, a z-pinch wire array, a gas puff, a liner, an isentropic compression load (ICE) to study material behavior under very high magnetic fields, or a fusion energy (IFE) target. This is because the output pulse rise time and width can be easily tailored to the specific application needs. In this paper we briefly summarize the developmental work done in Sandia and HCEI during the last few years, and describe our new MYKONOS Sandia High Current LTD Laboratory.

  19. High Current Systems for HyperV and PLX Plasma Railguns

    NASA Astrophysics Data System (ADS)

    Brockington, Samuel; Case, Andrew; Messer, Sarah; Bomgardner, Richard; Wu, Linchun; Elton, Raymond; Witherspoon, F. Douglas

    2010-11-01

    HyperV has been developing coaxial pulsed, plasma railgun accelerators for PLX and other high momentum plasma experiments. The full scale HyperV coaxial gun accelerates plasma armatures using a contoured electrode gap designed to mitigate the blow-by instability. Previous experiments with the full scale gun successfully formed and accelerated annular plasma armatures, but were limited to currents of up to only ˜400 kA. In order to increase full scale gun performance to the design goal of 200 μg at 200 km/s, the pulse forming networks required upgrading to support currents up to ˜1 MA. A high voltage, high current field-effect sparkgap switch and low inductance transmission line were designed and constructed to handle the increased current pulse. We will describe these systems and present initial test data from high current operation of the full-scale coax gun along with plans for future testing. Similar high current accelerator banks, switches, and TM lines will also be required to power PLX railguns which are planned to operate at 8000 μg at 50 km/s. The design of that experiment may require the capacitor banks to be located as much as 10 feet from the gun. We discuss the available options for low inductance connections for these systems.

  20. Transportation of high-current ion and electron beams in the accelerator drift gap in the presence of an additional electron background

    NASA Astrophysics Data System (ADS)

    Karas', V. I.; Kornilov, E. A.; Manuilenko, O. V.; Tarakanov, V. P.; Fedorovskaya, O. V.

    2015-12-01

    The dynamics of a high-current ion beam propagating in the drift gap of a linear induction accelerator with collective focusing is studied using 3D numerical simulations in the framework of the full system of the Vlasov-Maxwell equations (code KARAT). The ion beam is neutralized by a comoving electron beam in the current density and, partially, in space charge, since the velocities of electrons and ions differ substantially. The dynamics of the high-current ion beam is investigated for different versions of additional neutralization of its space charge. It is established that, for a given configuration of the magnetic field and in the presence of a specially programmed injection of additional electrons from the boundary opposite to the ion injection boundary, the angular divergence of the ion beam almost vanishes, whereas the current of the ion beam at the exit from the accelerator drift gap changes insignificantly and the beam remains almost monoenergetic.

  1. Transportation of high-current ion and electron beams in the accelerator drift gap in the presence of an additional electron background

    SciTech Connect

    Karas’, V. I. Kornilov, E. A.; Manuilenko, O. V.; Tarakanov, V. P.; Fedorovskaya, O. V.

    2015-12-15

    The dynamics of a high-current ion beam propagating in the drift gap of a linear induction accelerator with collective focusing is studied using 3D numerical simulations in the framework of the full system of the Vlasov–Maxwell equations (code KARAT). The ion beam is neutralized by a comoving electron beam in the current density and, partially, in space charge, since the velocities of electrons and ions differ substantially. The dynamics of the high-current ion beam is investigated for different versions of additional neutralization of its space charge. It is established that, for a given configuration of the magnetic field and in the presence of a specially programmed injection of additional electrons from the boundary opposite to the ion injection boundary, the angular divergence of the ion beam almost vanishes, whereas the current of the ion beam at the exit from the accelerator drift gap changes insignificantly and the beam remains almost monoenergetic.

  2. Vertical distribution of vibrational energy of molecular nitrogen in a stable auroral red arc and its effect on ionospheric electron densities. Ph.D. Thesis - Catholic Univ. of Am.

    NASA Technical Reports Server (NTRS)

    Newton, G. P.

    1973-01-01

    Previous solutions of the problem of the distribution of vibrationally excited molecular nitrogen in the thermosphere have either assumed a Boltzmann distribution and considered diffusion as one of the loss processes or solved for the energy level populations and neglected diffusion. Both of the previous approaches are combined by solving the time dependent continuity equations, including the diffusion process, for the first six energy levels of molecular nitrogen for conditions in the thermosphere corresponding to a stable auroral red arc. The primary source of molecular nitrogen excitation was subexcitation, and inelastic collisions between thermal electrons and molecular nitrogen. The reaction rates for this process were calculated from published cross section calculations. The loss processes for vibrational energy were electron and atomic oxygen quenching and vibrational energy exchange. The coupled sets of nonlinear, partial differential equations were solved numerically by employing finite difference equations.

  3. Acceleration and stability of a high-current ion beam in induction fields

    NASA Astrophysics Data System (ADS)

    Karas', V. I.; Manuilenko, O. V.; Tarakanov, V. P.; Federovskaya, O. V.

    2013-03-01

    A one-dimensional nonlinear analytic theory of the filamentation instability of a high-current ion beam is formulated. The results of 2.5-dimensional numerical particle-in-cell simulations of acceleration and stability of an annular compensated ion beam (CIB) in a linear induction particle accelerator are presented. It is shown that additional transverse injection of electron beams in magnetically insulated gaps (cusps) improves the quality of the ion-beam distribution function and provides uniform beam acceleration along the accelerator. The CIB filamentation instability in both the presence and the absence of an external magnetic field is considered.

  4. Acceleration and stability of a high-current ion beam in induction fields

    SciTech Connect

    Karas', V. I.; Manuilenko, O. V.; Tarakanov, V. P.; Federovskaya, O. V.

    2013-03-15

    A one-dimensional nonlinear analytic theory of the filamentation instability of a high-current ion beam is formulated. The results of 2.5-dimensional numerical particle-in-cell simulations of acceleration and stability of an annular compensated ion beam (CIB) in a linear induction particle accelerator are presented. It is shown that additional transverse injection of electron beams in magnetically insulated gaps (cusps) improves the quality of the ion-beam distribution function and provides uniform beam acceleration along the accelerator. The CIB filamentation instability in both the presence and the absence of an external magnetic field is considered.

  5. Methods of high current magnetic field generator for transcranial magnetic stimulation application

    SciTech Connect

    Bouda, N. R. Pritchard, J.; Weber, R. J.; Mina, M.

    2015-05-07

    This paper describes the design procedures and underlying concepts of a novel High Current Magnetic Field Generator (HCMFG) with adjustable pulse width for transcranial magnetic stimulation applications. This is achieved by utilizing two different switching devices, the MOSFET and insulated gate bipolar transistor (IGBT). Results indicate that currents as high as ±1200 A can be generated with inputs of +/−20 V. Special attention to tradeoffs between field generators utilizing IGBT circuits (HCMFG{sub 1}) and MOSFET circuits (HCMFG{sub 2}) was considered. The theory of operation, design, experimental results, and electronic setup are presented and analyzed.

  6. Coherent Effects of High Current Beam in Project-X Linac

    SciTech Connect

    Sukhanov, A.; Lunin, A.; Yakovlev, V.; Gonin, I.; Khabiboulline, T.; Saini, A.; Solyak, N.; Yostrikov, A.

    2012-09-01

    Resonance excitation of longitudinal high order modes in superconducting RF structures of Project-X continuous wave linac is studied. We analyze regimes of operation of the linac with high beam current, which can be used to provide an intense muon source for the future Neutrino Factory or Muon Collider, and also important for the Accelerator-Driven Subcritical systems. We calculate power loss and associated heat load to the cryogenic system. Longitudinal emittance growth is estimated. We consider an alternative design of the elliptical cavity for the high energy part of the linac, which is more suitable for high current operation.

  7. Coherent Effects of High Current Beam in Project-X Linac

    SciTech Connect

    Sukhanov, Alexander; Yakovlev, Vyacheslav; Gonin, Ivan; Khabiboulline, Timergali; Lunin, Andrei; Saini, Arun; Solyak, Nikolay; Vostrikov, Alexander

    2013-04-01

    Resonance excitation of longitudinal high order modes in superconducting RF structures of Project-X continuous wave linac is studied. We analyze regimes of operation of the linac with high beam current, which can be used to provide an intense muon source for the future Neutrino Factory or Muon Collider, and also important for the Accelerator-Driven Subcritical systems. We calculate power loss and associated heat load to the cryogenic system. Longitudinal emittance growth is estimated. We consider an alternative design of the elliptical cavity for the high energy part of the linac, which is more suitable for high current operation.

  8. ACCELERATORS: Design and simulation of a beam position monitor for the high current proton linac

    NASA Astrophysics Data System (ADS)

    Ruan, Yu-Fang; Xu, Tao-Guang; Fu, Shi-Nian

    2009-03-01

    In this paper, the 2-D electrostatic field software, POISSON, is used to calculate the characteristic impedance of a BPM (beam position monitor) for a high current proton linac. Furthermore, the time-domain 3-D module of MAFIA with a beam microbunch at a varying offset from the axis is used to compute the induced voltage on the electrodes as a function of time. Finally, the effect of low β beams on the induced voltage, the sensitivity and the signal dynamic range of the BPM are discussed.

  9. Beamline considerations for a compact, high current, high power linear RF electron accelerator

    SciTech Connect

    Marder, B.

    1987-06-01

    A design for a compact, high current, high power linear electron accelerator using an rf power source is investigated. It consists of adjacent cavities into which rf power is injected and through which electron pulses pass. The source is assumed to be capable of delivering sufficient rf power to the desired location at the proper phase. Beamline issues such as cavity loading, energy extraction, longitudinal and transverse pulse focusing, and beam breakup are considered. A device which, given the required source, can deliver beam parameters comparable to existing induction accelerators but which is more than an order of magnitude smaller appears feasible.

  10. Efficiency of pulse high-current generator energy transfer into plasma liner energy

    NASA Astrophysics Data System (ADS)

    Oreshkin, V. I.

    2013-08-01

    The efficiency of capacitor-bank energy transfer from a high-current pulse generator into kinetic energy of a plasma liner has been analyzed. The analysis was performed using a model including the circuit equations and equations of the cylindrical shell motion. High efficiency of the energy transfer into kinetic energy of the liner is shown to be achieved only by a low-inductance generator. We considered an "ideal" liner load in which the load current is close to zero in the final of the shell compression. This load provides a high (up to 80%) efficiency of energy transfer and higher stability when compressing the liner.

  11. High current Cu3P liquid metal ion source using a novel extractor configuration

    NASA Astrophysics Data System (ADS)

    Higuchi-Rusli, R. H.; Corelli, J. C.

    1987-12-01

    It has been found that by utilizing a sharp needle for the extractor electrode in close proximity to the source tip wetted with Cu3P liquid alloy, a large increase (factor ˜300) in ion current is observed in comparison to standard liquid metal ion sources (LMIS's). In standard previously used LMIS's the extractor electrode was a flat plane with a circular hole centered on the source needle tip. This new high current source has important applications in focused and broad ion beam deposition systems.

  12. Methods of high current magnetic field generator for transcranial magnetic stimulation application

    NASA Astrophysics Data System (ADS)

    Bouda, N. R.; Pritchard, J.; Weber, R. J.; Mina, M.

    2015-05-01

    This paper describes the design procedures and underlying concepts of a novel High Current Magnetic Field Generator (HCMFG) with adjustable pulse width for transcranial magnetic stimulation applications. This is achieved by utilizing two different switching devices, the MOSFET and insulated gate bipolar transistor (IGBT). Results indicate that currents as high as ±1200 A can be generated with inputs of +/-20 V. Special attention to tradeoffs between field generators utilizing IGBT circuits (HCMFG1) and MOSFET circuits (HCMFG2) was considered. The theory of operation, design, experimental results, and electronic setup are presented and analyzed.

  13. Productivity Improvement for the SHX--SEN's Single-Wafer High-Current Ion Implanter

    SciTech Connect

    Ninomiya, Shiro; Ochi, Akihiro; Kimura, Yasuhiko; Yumiyama, Toshio; Kudo, Tetsuya; Kurose, Takeshi; Kariya, Hiroyuki; Tsukihara, Mitsukuni; Ishikawa, Koji; Ueno, Kazuyoshi

    2011-01-07

    Equipment productivity is a critical issue for device fabrication. For ion implantation, productivity is determined both by ion current at the wafer and by utilization efficiency of the ion beam. Such improvements not only result in higher fabrication efficiency but also reduce consumption of both electrical power and process gases. For high-current ion implanters, reduction of implant area is a key factor to increase efficiency. SEN has developed the SAVING system (Scanning Area Variation Implantation with Narrower Geometrical pattern) to address this opportunity. In this paper, three variations of the SAVING system are introduced along with discussion of their effects on fab productivity.

  14. Modelling of a high-current magnetron discharge in a plasma electron emitter

    NASA Astrophysics Data System (ADS)

    Udovichenko, S. Yu; Kostrin, D. K.; Lisenkov, A. A.

    2017-07-01

    An analytical model of a high-current form of a low-pressure glow discharge in an inverted cylindrical magnetron, which performs the function of plasma electron emitter, is shown. Were found conditions of the discharge self-sustaining, allowing to estimate the voltage of the discharge and determine the critical value of the magnetic field and residual gas pressure below which the existence of this type of discharge is impossible. A comparison of the calculated discharge characteristics with experimental data obtained on the setup for studying the emission properties of the magnetron discharge was carried out.

  15. High-current lanthanum-hexaboride electron emitter for a quasi-stationary arc plasma generator

    SciTech Connect

    Davydenko, V. I. Ivanov, A. A. Shul’zhenko, G. I.

    2015-11-15

    A high-current electron emitter on the basis of lanthanum hexaboride is developed for quasi-stationary arc plasma generators of ion sources. The emitter consists of a set of LaB{sub 6} washers interleaved with washers made of thermally extended graphite. The emitter is heated by the current flowing through the graphite washers. The thermal regime of emitter operation during plasma generation is considered. The emitter has been successfully used in the ion sources of the diagnostic injectors of fast hydrogen atomic beams.

  16. Sparking limits, cavity loading, and beam breakup instability associated with high-current rf linacs

    SciTech Connect

    Faehl, R.J.; Lemons, D.S.; Thode, L.E.

    1982-01-01

    The limitations on high-current rf linacs due to gap sparking, cavity loading, and the beam breakup instability are studied. It appears possible to achieve cavity accelerating gradients as high as 35 MV/m without sparking. Furthermore, a linear analysis, as well as self-consistent particle simulations of a multipulsed 10 kA beam, indicated that only a negligible small fraction of energy is radiated into nonfundamental cavity modes. Finally, the beam breakup instability is analyzed and found to be able to magnify initial radial perturbations by a factor of no more than about 20 during the beam transit time through a 1 GeV accelerator.

  17. Nitrogen related shallow thermal donors in silicon

    NASA Astrophysics Data System (ADS)

    Fujita, N.; Jones, R.; Öberg, S.; Briddon, P. R.

    2007-07-01

    In this letter, the authors investigate the electrical properties of nitrogen related shallow thermal donor (STD) candidates and their concentrations under different doping conditions by means of density functional theory. Experimentally, the existence of STDs containing one nitrogen atom and both even and odd numbers of oxygen atoms has been proposed. However, so far first principles studies have not presented a candidate for the latter. Here, they show that the NO defect possesses a shallow donor level. Adding one or two more oxygen atoms results in the donor level to become shallower. The fraction of shallow nitrogen related donors to N dimers increases in material with low concentration of nitrogen.

  18. Infrared gas phase study on plasma-polymer interactions in high-current diffuse dielectric barrier discharge

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Welzel, S.; Starostin, S. A.; van de Sanden, M. C. M.; Engeln, R.; de Vries, H. W.

    2017-06-01

    A roll-to-roll high-current diffuse dielectric barrier discharge at atmospheric pressure was operated in air and Ar/N2/O2 gas mixtures. The exhaust gas from the discharge was studied using a high-resolution Fourier-transform infrared spectrometer in the range from 3000 to 750 cm-1 to unravel the plasma-polymer interactions. The absorption features of HxNyOz, COx, and HCOOH (formic acid) were identified, and the relative densities were deduced by fitting the absorption bands of the detected molecules. Strong interactions between plasma and polymer (Polyethylene-2,6-naphthalate, or PEN) in precursor-free oxygen-containing gas mixtures were observed as evidenced by a high COx production. The presence of HCOOH in the gas effluent, formed through plasma-chemical synthesis of COx, turns out to be a sensitive indicator for etching. By adding tetraethylorthosilicate precursor in the plasma, dramatic changes in the COx production were measured, and two distinct deposition regimes were identified. At high precursor flows, a good agreement with the precursor combustion and the COx production was observed, whereas at low precursor flows an etching-deposition regime transpires, and the COx production is dominated by polymer etching.

  19. An analysis of the anomalous high-current cathode emission in pseudospark and back-of-the-cathode lighted thyratron switches

    NASA Astrophysics Data System (ADS)

    Hartmann, W.; Dominic, V.; Kirkman, G. F.; Gundersen, M. A.

    1989-06-01

    An analysis of the anomalously large cathode emission recently observed in the superdense glow of pseudospark and back-lighted thyratrons is presented. These switches are low-pressure (27 PaH2) glow-discharge pulsed-power devices. After operating at peak discharge currents of 6 to 8 kA and pulse durations of 0.5 to 1 microsec., the surface surrounding the cathode hole was found to have been homogeneously melted within a radius of approx. 4 mm indicating that the discharge is a superdense glow discharge, not an arc, with a cross-sectional area on the order of 1 sq cm. This conclusion is also supported by streak camera measurements. The current density at the cathode surface under these conditions is 5 to 10 kA/sq cm, several orders of magnitude larger than that of thermionic cathodes in common thyratrons. This high-current density is explained by intense cathode heating from a high-current density ion beam produced in the cathode fall during the initial stage of current buildup. The surface heating resulting from this beam yields a significant field-enhanced thermionic emission of electrons.

  20. An analysis of the anomalous high-current cathode emission in pseudospark and back-of-the-cathode lighted thyratron switches

    NASA Astrophysics Data System (ADS)

    Hartmann, W.; Dominic, V.; Kirkman, G. F.; Gundersen, M. A.

    1989-06-01

    An analysis of the anomalously large cathode emission recently observed in the superdense glow of pseudospark and back-lighted thyratrons is presented. These switches are low-pressure (27 Pa H2) glow-discharge pulsed-power devices. After operating at peak discharge currents of 6-8 kA and pulse durations of 0.5-1 μs, the surface surrounding the cathode hole was found to have been homogeneously melted within a radius of ≊4 mm indicating that the discharge is a superdense glow discharge, not an arc, with a cross-sectional area on the order of 1 cm2. This conclusion is also supported by streak camera measurements. The current density at the cathode surface under these conditions is 5-10 kA/cm2, several orders of magnitude larger than that of thermionic cathodes in common thyratrons. This high-current density is explained by intense cathode heating from a high-current density ion ``beam'' produced in the cathode fall during the initial stage of current buildup. The surface heating resulting from this ``beam'' yields a significant field-enhanced thermionic emission of electrons.

  1. Development and Testing of High Current Hollow Cathodes for High Power Hall Thrusters

    NASA Technical Reports Server (NTRS)

    Kamhawi, Hani; Van Noord, Jonathan

    2012-01-01

    NASA's Office of the Chief Technologist In-Space Propulsion project is sponsoring the testing and development of high power Hall thrusters for implementation in NASA missions. As part of the project, NASA Glenn Research Center is developing and testing new high current hollow cathode assemblies that can meet and exceed the required discharge current and life-time requirements of high power Hall thrusters. This paper presents test results of three high current hollow cathode configurations. Test results indicated that two novel emitter configurations were able to attain lower peak emitter temperatures compared to state-of-the-art emitter configurations. One hollow cathode configuration attained a cathode orifice plate tip temperature of 1132 degC at a discharge current of 100 A. More specifically, test and analysis results indicated that a novel emitter configuration had minimal temperature gradient along its length. Future work will include cathode wear tests, and internal emitter temperature and plasma properties measurements along with detailed physics based modeling.

  2. Nuclear microprobe performance in high-current proton beam mode for micro-PIXE

    NASA Astrophysics Data System (ADS)

    Vavpetič, P.; Kelemen, M.; Jenčič, B.; Pelicon, P.

    2017-08-01

    The performance of a nuclear microprobe is dominantly determined by the brightness of the injected ion beam. At Jožef Stefan Institute (JSI), negative hydrogen ion beams are created in a multicusp ion source and injected into a 2 MV tandetron accelerator. The output characteristics of the multicusp ion source were tuned in order to obtain matching proton beam intensities for the ion accelerator and for the object slits as well. For the optimal focusing of the proton beam in a high-current mode (I > 100 pA) to the sub-micrometer dimensions, dedicated thin nanostructures with sharp edges have been manufactured. Set of nanostructures was micromachined by focused ion beam (FIB) at film reference material, produced by Institute for Reference Materials and Measurements (IRMM) and constituted of 57 μg/cm2 of titanium on vitreous carbon substrate. The proton beam profiles were measured by beam scans across the nanostructures over long measuring times, indicating eventual slow drifts of the sample from a reference beam direction. Overall, proton beam dimensions of 600 nm were obtained, demonstrating appropriate stability for micro-PIXE (micro-Particle Induced X-ray Emission) at sub-micrometer resolution for elemental analysis of biological tissue samples prepared in a freeze-dried state or in a frozen-hydrated state. The resulting performance required for micro-PIXE analysis in a high current mode with a 3 MeV proton beam is presented.

  3. R & D on Very-High-Current Superconducting Proton Linac, Final Report

    SciTech Connect

    Ben-Zvi, Ilan

    2013-03-31

    The aim of this R&D project was to develop a superconducting cavity for a very-­ high-current proton accelerator. The particular application motivating the proposal was a LHC upgrade called the Superconducting Proton Linac, or SPL. Under the grant awarded to Stony Brook University the cavity was designed, a prototype copper cavity, followed by the niobium cavity, were built. A new set of HOM dampers was developed. The cavity has outstanding RF performance parameters – low surface fields, low power loss and all HOMs are fully damped. In fact, it is a “universal cavity” in the sense that it is suited for the acceleration of high-­current protons and well as high current electrons. Its damping of HOM modes is so good that it can see service in a multi-pass linac or an Energy Recovery Linac in addition to the easier service in a single-pass linac. Extensive measurements were made on the cavities and couplers, with the exception of the cold test of the niobium cavity. At the time of this report the cavity has been chemically processed and is ready for vertical testing which will be carried out shortly.

  4. Progress and future developments of high current ion source for neutral beam injector in the ASIPP

    NASA Astrophysics Data System (ADS)

    Hu, Chundong; Xie, Yahong; Xie, Yuanlai; Liu, Sheng; Liu, Zhimin; Xu, Yongjian; Liang, Lizhen; Sheng, Peng; Jiang, Caichao

    2015-04-01

    A high current hot cathode bucket ion source, which based on the US long pulse ion source is developed in Institute of Plasma Physics, Chinese Academy of Sciences. The ion source consists of a bucket plasma generator with multi-pole cusp fields and a set of tetrode accelerator with slit apertures. So far, four ion sources are developed and conditioned on the ion source test bed. 4 MW hydrogen beam with beam energy of 80 keV is extracted. In Aug. 2013, EAST NBI 1 with two ion source installed on the EAST, and achieved H-mode plasma with NBI injection for the first time. In order to achieve stable long pulse operation of high current ion source and negative ion source research, the RF ion source with 200 mm diameter and 120 mm depth driver is designed and developed. The first RF plasma generated with 2 kW power of 1 MHz frequency. More of the RF plasma tests and negative source relative research need to do in the future.

  5. Aperture Test for Internal Target Operation in the JLAB High-current ERL

    SciTech Connect

    Zhang, Shukui

    2013-06-01

    A high current beam transmission test has been successfully completed at the JLAB FEL Facility, culminating in very low-loss transmission of a high current CW beam through a small aperture. The purpose of this test was to determine if an ERL is capable of meeting the stringent requirements imposed by the use of a 1018/cm3 internal gas target proposed for the DarkLight experiment*. Minimal beamline modifications were made to create a machine configuration that is substantially different from those used in routine UV or IR FEL operation. A sustained (8 hour) high power beam run was performed, with clean transmission through a 2 mm transverse aperture of 127 mm length simulating the target configuration. A beam size of 50 um (rms) was measured near the center of the aperture. Experimental data from a week-long test run consistently exhibited beam loss of only a few ppm on the aperture while running 4.5 mA current at 100 MeV -- or nearly 0.5 MW beam power. This surpassed the users? expectation and demonstrated a unique capability of an ERL for this type of experiments. This report presents a summary of the experiment, a brief overview of our activities, and outlines future plans.

  6. REVIEW OF VARIOUS APPROACHES TO ADDRESS HIGH CURRENTS IN SRF ELECTRON LINACS.

    SciTech Connect

    BEN-ZVI, I.

    2005-07-10

    The combination of high-brightness electron sources and high-current SRF Energy Recovery Linacs (ERL) leads to a new emerging technology: High-power, high-brightness electron beams. This technology enables extremely high average power Free-Electron Lasers, a new generation of extreme brightness light sources, electron coolers of high-energy hadron storage rings, polarized electron-hadron colliders of very high luminosity, compact Thomson scattering X-ray sources, terahertz radiation generators and much more. What is typical for many of these applications is the need for very high current, defined here as over 100 mA average current, and high brightness, which is charge dependant, but needs to be in the range of between sub micron up to perhaps 50 microns, usually the lower--the better. Suffice it to say that while there are a number of projects aiming at this level of performance, none is anywhere near it. This work will review the problems associated with the achievement of such performance and the various approaches taken in a number of laboratories around the world to address the issues.

  7. Progress and future developments of high current ion source for neutral beam injector in the ASIPP

    SciTech Connect

    Hu, Chundong; Xie, Yahong Xie, Yuanlai; Liu, Sheng; Liu, Zhimin; Xu, Yongjian; Liang, Lizhen; Sheng, Peng; Jiang, Caichao

    2015-04-08

    A high current hot cathode bucket ion source, which based on the US long pulse ion source is developed in Institute of Plasma Physics, Chinese Academy of Sciences. The ion source consists of a bucket plasma generator with multi-pole cusp fields and a set of tetrode accelerator with slit apertures. So far, four ion sources are developed and conditioned on the ion source test bed. 4 MW hydrogen beam with beam energy of 80 keV is extracted. In Aug. 2013, EAST NBI 1 with two ion source installed on the EAST, and achieved H-mode plasma with NBI injection for the first time. In order to achieve stable long pulse operation of high current ion source and negative ion source research, the RF ion source with 200 mm diameter and 120 mm depth driver is designed and developed. The first RF plasma generated with 2 kW power of 1 MHz frequency. More of the RF plasma tests and negative source relative research need to do in the future.

  8. Design and study of a high-current 5-cell superconducting rf cavity.

    SciTech Connect

    Liu, Z.; Nassiri, A.; Waldschmidt, G. )

    2010-01-01

    The Advanced Photon Source (APS) at Argonne National Laboratory is considering the development of a superconducting linac-based fourth-generation hard X-ray source to meet future scientific needs of the hard X-ray user community. This work specifically focuses on the design of an optimized 5-cell superconducting radio-frequency structure well suited for a high-energy, high-beam-current energy recovery linac. The cavity design parameters are based on the APS storage ring nominal 7 GeV and 100 mA beam operation. A high-current 5-cell cw superconducting cavity operating at 1.4 GHz has been designed. In order to achieve a high current, the accelerating cavity shape has been optimized and large end-cell beam pipes have been adopted. The beam break-up threshold of the cavity has been estimated using the code TDBBU, which predicts a high threshold beam current for a 7 GeV energy recovery linac model. A copper prototype cavity has been fabricated that uses half-cell modules, initially assembled by clamping the cells together.

  9. Theoretical and experimental study of a high-current vacuum arc in a uniform axial magnetic field

    NASA Astrophysics Data System (ADS)

    Morimiya, Osami

    1992-01-01

    Measurements of the electron temperature, floating potential, plasma density, and average plasma pressure in a magnetically confined high-current vacuum arc are described. A 40-mm-diam, 30-mm-long arc was initiated between OFCu copper electrodes in a uniform axial magnetic field by triggering the gap. The crest values of the arc current ranged from 3 to 20 kA. The electron temperature by Langmuir probe measurement was Te= 2.5-3.0 eV with a uniform space distribution and was independent of the arc current. The space distribution of the ion density was parabolic in the radial direction and with a zero derivative in the axial direction. The average plasma pressure by paramagnetic measurement increased with the square of the arc current. The experiment showed that the arc column could be considered as an infinitely long column in which the plasma parameters have zero axial derivatives. Theoretical analysis has been carried out under the following assumptions. An infinitely long cylindrical and fully ionized steady-state plasma in which all quantities varied in the r direction only was considered. The anisotropy factor σ∥/σ⊥ for electrical conductivities was taken into account in the theoretical analysis, where σ∥ and σ⊥ were electrical conductivities parallel to the magnetic field and perpendicular to it, respectively. The plasma parameters determined from the experiments and theoretical analysis agreed closely with each other when the factor σ∥/σ⊥ was equal to ˜2, which is the theoretical upper limit in a high magnetic field. Constant temperature characteristics independent of the arc current have been found to be clearly seen by using line radiation as the dominant power loss in the power balance equation.

  10. Stacking fault expansion from basal plane dislocations converted into threading edge dislocations in 4H-SiC epilayers under high current stress

    NASA Astrophysics Data System (ADS)

    Konishi, Kazuya; Yamamoto, Shigehisa; Nakata, Shuhei; Nakamura, Yu; Nakanishi, Yosuke; Tanaka, Takanori; Mitani, Yoichiro; Tomita, Nobuyuki; Toyoda, Yoshihiko; Yamakawa, Satoshi

    2013-07-01

    We evaluate the stacking faults (SFs) expansion from basal plane dislocations (BPDs) converted into threading edge dislocations (TEDs) under the current stress to the pn devices and analyzed the nucleation site of the SF by combined polishing, chemical etching in molten KOH, photoluminescence imaging, Focus ion beam, transmission electron microscopy, and Time-of-Flight secondary ion mass spectrometer techniques. It was found that the formation of SFs occurs upon the current stress levels of 400 A/cm2 where the diode area is not including BPDs in the drift layer after the high current stress, and the high current stress increases the SFs expansion density. It was also found the dependence of the junction temperature. The estimated activation energy for the expansion of SFs is Ea = 0.46 eV. The SF extends from the conversion point of the BPD into the TED within buffer layer. Even though BPDs converted into TEDs within the high doped buffer layer, SFs expand under high current stress.

  11. Ternary nitrogen-doped graphene/nickel ferrite/polyaniline nanocomposites for high-performance supercapacitors

    NASA Astrophysics Data System (ADS)

    Wang, Wenjuan; Hao, Qingli; Lei, Wu; Xia, Xifeng; Wang, Xin

    2014-12-01

    The electrochemical property of graphene can be significantly enhanced due to the incorporating of heteroatoms into graphene. In this article, the ternary nitrogen-doped graphene/nickel ferrite/polyaniline (NGNP) nanocomposite is synthesized by a facile two-step approach and its electrochemical properties as electrodes for supercapacitors are studied by various electrochemical measurements. The specific capacitance of NGNP is 645.0 F g-1 at 1 mV s-1 and 667.0 F g-1 at 0.1 A g-1 in a three- and two-electrode system, respectively, much higher than other binary electrodes. In a two-electrode symmetric system, the energy density of the NGNP electrode is 92.7 W h kg-1 at a power density of 110.8 W kg-1, moreover, that of the supercapacitor based on NGNP can also reach 23.2 W h kg-1 at a power density of 27.7 W kg-1. In addition, the capacitance loses only 5% after repeating test for 5000 cycles, and about 10% after 10,000 cycles at a high current density 5 A g-1. The results demonstrate the novel ternary NGNP electrode produced by the current economical method will gain promising applications in supercapacitors and other devices by virtue of its outstanding characteristics (high specific capacitance, high power and energy density, excellent cycle life).

  12. Device for plasma confinement and heating by high currents and nonclassical plasma transport properties

    DOEpatents

    Coppi, B.; Montgomery, D.B.

    1973-12-11

    A toroidal plasma containment device having means for inducing high total plasma currents and current densities and at the same time emhanced plasma heating, strong magnetic confinement, high energy density containment, magnetic modulation, microwaveinduced heating, and diagnostic accessibility is described. (Official Gazette)

  13. Influence of nitrogen admixture to argon on the ion energy distribution in reactive high power pulsed magnetron sputtering of chromium

    NASA Astrophysics Data System (ADS)

    Breilmann, W.; Maszl, C.; Hecimovic, A.; von Keudell, A.

    2017-04-01

    Reactive high power impulse magnetron sputtering (HiPIMS) of metals is of paramount importance for the deposition of various oxides, nitrides and carbides. The addition of a reactive gas such as nitrogen to an argon HiPIMS plasma with a metal target allows the formation of the corresponding metal nitride on the substrate. The addition of a reactive gas introduces new dynamics into the plasma process, such as hysteresis, target poisoning and the rarefaction of two different plasma gases. We investigate the dynamics for the deposition of chromium nitride by a reactive HiPIMS plasma using energy- and time-resolved ion mass spectrometry, fast camera measurements and temporal and spatially resolved optical emission spectroscopy. It is shown that the addition of nitrogen to the argon plasma gas significantly changes the appearance of the localized ionization zones, the so-called spokes, in HiPIMS plasmas. In addition, a very strong modulation of the metal ion flux within each HiPIMS pulse is observed, with the metal ion flux being strongly suppressed and the nitrogen molecular ion flux being strongly enhanced in the high current phase of the pulse. This behavior is explained by a stronger return effect of the sputtered metal ions in the dense plasma above the racetrack. This is best observed in a pure nitrogen plasma, because the ionization zones are mostly confined, implying a very high local plasma density and consequently also an efficient scattering process.

  14. Nitrogen-doped hierarchically porous carbon spheres as efficient metal-free electrocatalysts for an oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Liu, You-Lin; Shi, Cheng-Xiang; Xu, Xue-Yan; Sun, Ping-Chuan; Chen, Tie-Hong

    2015-06-01

    Using hierarchically mesoporous silica spheres as a hard template and methyl violet as carbon and nitrogen source, nitrogen-doped hierarchically porous carbon spheres (N-HCS) are successfully prepared via a nanocasting method. The nitrogen-doped carbon spheres obtained after carbonization at 1000 °C (N-HCS-1000) exhibit a hierarchically micro-meso-macroporous structure with a relatively high surface area (BET) of 1413 m2 g-1 and a notably large pore volume of 2.96 cm3 g-1. In an oxygen reduction reaction (ORR) in alkaline media, the N-HCS-1000 material exhibits excellent activity with high current density, and its onset potential is notably close to that of the commercial Pt/C catalyst. The efficient catalytic activity of this catalyst could be attributed to the high electrical conductivity of the nitrogen-doped carbon matrix as well as the hierarchically porous framework. This catalyst also exhibits better methanol crossover resistance and higher stability than the commercial Pt/C catalyst.

  15. Development of an all-permanent-magnet microwave ion source equipped with multicusp magnetic fields for high current proton beam production.

    PubMed

    Tanaka, M; Hara, S; Seki, T; Iga, T

    2008-02-01

    An all-permanent-magnet (APM) microwave hydrogen ion source was developed to reduce the size and to simplify structure of a conventional solenoid coil microwave ion source developed for reliability improvement of high current proton linac application systems. The difficulty in developing the APM source was sensitive dependence of the source performance on axial magnetic field in the microwave discharge chamber. It was difficult to produce high current proton beam stably without precise tuning of the magnetic field using solenoid coils. We lowered the sensitivity using multicusp magnetic fields for plasma confinement at the discharge chamber sidewall of the source. This enabled stable high current proton beam production with the APM microwave ion source with no tuning coil. The water cooling and the power supply for the coils are not necessary for the APM source, which leads to better reliability and system simplification. The outer diameter of the APM source was around 300 mm, which was 20% lower than the coil source. The APM source produced a maximum hydrogen ion beam current of 65 mA (high current density of 330 mA/cm(2), proton ratio of 87%, and beam energy of 30 keV) with a 5 mm diameter extraction aperture, pulse width of 400 micros, and 20 Hz repetition rate at 1.3 kW microwave power. This performance is almost the same as the best performances of the conventional coil sources. The extracted ion beams were focused with electrostatic five-grid lens to match beam to acceptance of radio-frequency quadrupole linacs. The maximum focused beam current through the orifice (5 mm radius) and the lens was 36 mA and the 90% focused beam half-width was 1-2 mm.

  16. Development of an all-permanent-magnet microwave ion source equipped with multicusp magnetic fields for high current proton beam productiona)

    NASA Astrophysics Data System (ADS)

    Tanaka, M.; Hara, S.; Seki, T.; Iga, T.

    2008-02-01

    An all-permanent-magnet (APM) microwave hydrogen ion source was developed to reduce the size and to simplify structure of a conventional solenoid coil microwave ion source developed for reliability improvement of high current proton linac application systems. The difficulty in developing the APM source was sensitive dependence of the source performance on axial magnetic field in the microwave discharge chamber. It was difficult to produce high current proton beam stably without precise tuning of the magnetic field using solenoid coils. We lowered the sensitivity using multicusp magnetic fields for plasma confinement at the discharge chamber sidewall of the source. This enabled stable high current proton beam production with the APM microwave ion source with no tuning coil. The water cooling and the power supply for the coils are not necessary for the APM source, which leads to better reliability and system simplification. The outer diameter of the APM source was around 300mm, which was 20% lower than the coil source. The APM source produced a maximum hydrogen ion beam current of 65mA (high current density of 330mA/cm2, proton ratio of 87%, and beam energy of 30keV) with a 5mm diameter extraction aperture, pulse width of 400μs, and 20Hz repetition rate at 1.3kW microwave power. This performance is almost the same as the best performances of the conventional coil sources. The extracted ion beams were focused with electrostatic five-grid lens to match beam to acceptance of radio-frequency quadrupole linacs. The maximum focused beam current through the orifice (5mm radius) and the lens was 36mA and the 90% focused beam half-width was 1-2mm.

  17. Optimal conditions for high current proton irradiations at the university of Wisconsin's ion beam laboratory

    NASA Astrophysics Data System (ADS)

    Wetteland, C. J.; Field, K. G.; Eiden, T. J.; Gerczak, T. J.; Maier, B. R.; Albakri, O.; Sridharan, K.; Allen, T. R.

    2013-04-01

    The National Electrostatics Corporation's (NEC) Toroidal Volume Ion Source (TORVIS) source is known for exceptionally high proton currents with minimal service downtime as compared to traditional sputter sources. It has been possible to obtain over 150μA of proton current from the source, with over 70μA on the target stage. However, beam fluxes above ˜1×1017/m2-s may have many undesirable effects, especially for insulators. This may include high temperature gradients at the surface, sputtering, surface discharge, cracking or even disintegration of the sample. A series of experiments were conducted to examine the role of high current fluxes in a suite of ceramics and insulating materials. Results will show the optimal proton irradiation conditions and target mounting strategies needed to minimize unwanted macro-scale damage, while developing a procedure for conducting preliminary radiation experiments.

  18. Evidence for large-area superemission into a high-current glow discharge

    NASA Astrophysics Data System (ADS)

    Hartmann, W.; Dominic, V.; Kirkman, G. F.; Gundersen, M. A.

    1988-10-01

    This letter presents evidence for large-area (≊1 cm2) cathode superemission (˜10 000 A/cm2) into a high-current glow discharge in a pseudospark or back lighted thyratron switch. Cathodes studied with a scannning electron microscope following operation at 6-8 kA, ≊1 μs pulse length, and 105 pulses in a low-pressure H2 discharge show evidence of melting of a thin surface layer within a radius of ˜4 mm, indicating that the discharge is a superdense glow with a cross-sectional area of the order of 1 cm2, rather than an arc. Further supporting evidence is provided by streak camera data. An ion beam present during the avalanche phase of the discharge is responsible for heating the cathode surface resulting in a significant field-enhanced thermionic emission.

  19. Plasma Emission Characteristics from a High Current Hollow Cathode in an Ion Thruster Discharge Chamber

    NASA Technical Reports Server (NTRS)

    Foster, John E.; Patterson, Michael J.

    2002-01-01

    The presence of energetic ions produced by a hollow cathodes operating at high emission currents (greater than 5A) has been documented in the literature. In order to further elucidate these findings, an investigation of a high current cathode operating in an ion thruster discharge chamber has been undertaken. Using Langmuir probes, a low energy charged particle analyzer and emission spectroscopy, the behavior of the near-cathode plasma and the emitted ion energy distribution was characterized. The presence of energetic ions was confirmed. It was observed that these ions had energies in excess of the discharge voltage and thus cannot be simply explained by ions falling out of plasma through a potential difference of this order. Additionally, evidence provided by Langmuir probes suggests the existence of a double layer essentially separating the hollow cathode plasma column from the main discharge. The radial potential difference associated with this double layer was measured to be of order the ionization potential.

  20. Enabling cost-effective high-current burst-mode operation in superconducting accelerators

    DOE PAGES

    Sheffield, Richard L.

    2015-06-01

    Superconducting (SC) accelerators are very efficient for CW or long-pulse operation, and normal conducting (NC) accelerators are cost effective for short-pulse operation. The addition of a short NC linac section to a SC linac can correct for the energy droop that occurs when pulsed high-current operation is required that exceeds the capability of the klystrons to replenish the cavity RF fields due to the long field fill-times of SC structures, or a requirement to support a broad range of beam currents results in variable beam loading. This paper describes the implementation of this technique to enable microseconds of high beam-current,more » 90 mA or more, in a 12 GeV SC long-pulse accelerator designed for the MaRIE 42-keV XFEL proposed for Los Alamos National Laboratory.« less

  1. A new high current laboratory and pulsed homopolar generator power supply at the University of Texas

    NASA Astrophysics Data System (ADS)

    Floyd, J. E.; Aanstoos, T. A.

    1984-03-01

    The University of Texas at Austin is constructing a facility for research in pulse power technology for the Center for Electromechanics at the Balcones Research Center. The facility, designed to support high-current experiments, will be powered by six homopolar generators, each rated at 10 MJ and arranged to allow matching the requirements of resistive and inductive loads at various voltage and current combinations. Topics covered include the high bay, the power supply configuration and parameters, the speed and field control, and the magnetic circuit. Also considered are the removable air-cooled brushes, the water-cooled field coils, the hydraulic motor sizing and direct coupling, the low-impedance removable field coils, and the hydrostatic bearing design.

  2. High ion charge states in a high-current, short-pulse, vacuum ARC ion sources

    SciTech Connect

    Anders, A.; Brown, I.; MacGill, R.; Dickinson, M.

    1996-08-01

    Ions of the cathode material are formed at vacuum arc cathode spots and extracted by a grid system. The ion charge states (typically 1-4) depend on the cathode material and only little on the discharge current as long as the current is low. Here the authors report on experiments with short pulses (several {mu}s) and high currents (several kA); this regime of operation is thus approaching a more vacuum spark-like regime. Mean ion charge states of up to 6.2 for tungsten and 3.7 for titanium have been measured, with the corresponding maximum charge states of up to 8+ and 6+, respectively. The results are discussed in terms of Saha calculations and freezing of the charge state distribution.

  3. Electromagnetic Modeling of Cavities and Power Couplers for Sc = High-Current Proton Accelerators

    NASA Astrophysics Data System (ADS)

    Krawczyk, Frank

    1998-04-01

    Newly proposed accelerator applications such as Accelerator Transmutation of Waste (ATW) or Accelerator Production of Tritium (APT) require high-current, high-power proton accelerators. The Los Alamos National Laboratory design of an APT facility, which can easily be adopted to other applications, proposes a linear accelerator with superconducting rf-cavities for particle acceleration. The required high power levels demand a careful design of the rf-components such as cavities and power couplers. Most of the computational work requires state-of-the-art modeling software that can give fields, rf-losses and beam-interaction quantities in 2D and 3D models. This contribution presents the modeling techniques and results of our work with the MAFIA electromagnetic simulator.

  4. The GSI 36 MHz high-current IH-type RFQ and HIIF-relevant extensions

    NASA Astrophysics Data System (ADS)

    Ratzinger, U.; Kaspar, K.; Malwitz, E.; Minaev, S.; Tiede, R.

    The GSI High-Current Injector linac for ions with mass to charge ratios up to 65 and beam intensities up to 16 mA is under construction and will deliver beam in 1999. The first section of that linac is a 36 MHz RFQ cavity with a total length of 9.2 m and an energy range from 2.2 to 120 keV/u. It will be the first RFQ in H110-mode operation. The advantages of that RF structure for the acceleration of very heavy ion beams are outlined. MAFIA calculations are compared with the results from bead pull measurements of the completed cavity. Possible extensions of that type of RF structure towards a multibeam cavity are discussed.

  5. Switch contact device for interrupting high current, high voltage, AC and DC circuits

    DOEpatents

    Via, Lester C.; Witherspoon, F. Douglas; Ryan, John M.

    2005-01-04

    A high voltage switch contact structure capable of interrupting high voltage, high current AC and DC circuits. The contact structure confines the arc created when contacts open to the thin area between two insulating surfaces in intimate contact. This forces the arc into the shape of a thin sheet which loses heat energy far more rapidly than an arc column having a circular cross-section. These high heat losses require a dramatic increase in the voltage required to maintain the arc, thus extinguishing it when the required voltage exceeds the available voltage. The arc extinguishing process with this invention is not dependent on the occurrence of a current zero crossing and, consequently, is capable of rapidly interrupting both AC and DC circuits. The contact structure achieves its high performance without the use of sulfur hexafluoride.

  6. A high-current microwave ion source with permanent magnet and its beam emittance measurement

    SciTech Connect

    Yao Zeen; Tan Xinjian; Du Hongxin; Luo Ben; Liu Zhanwen

    2008-07-15

    The progress of a 2.45 GHz high-current microwave ion source with permanent magnet for T(d,n){sup 4}He reaction neutron generator is reported in this paper. At 600 W microwave power and 22 kV extraction voltage, 90 mA peak hydrogen ion beam is extracted from a single aperture of 6 mm diameter. The beam emittance is measured using a simplified pepper-pot method. The (x,x{sup '}) emittance and the (y,y{sup '}) emittance for 14 keV hydrogen ion beam are 55.3{pi} and 58.2{pi} mm mrad, respectively. The normalized emittances are 0.302{pi} and 0.317{pi} mm mrad, respectively.

  7. Magnetoresistance between oxidized Co-rich particles grown by high current electrochemical deposition

    NASA Astrophysics Data System (ADS)

    Plaza, M.; Perez, L.; Sanchez, M. C.; Fernández-Pacheco, A.; De Teresa, J. M.

    2009-12-01

    In this work, we present Co-rich particles which have been successfully grown by high current electroplating. This technique produces particles with a Co-Cu core surrounded by an oxidized shell. This shell has two consequences: on the one hand, it electrically isolates the magnetic core and acts as a tunnel barrier; on the other hand, the ferromagnetic/antiferromagnetic structure causes an exchange bias coupling when cooling the particles in the presence of magnetic field. We also present magnetoresistance measurements up to 9 T. At low field, direct tunnelling between magnetic cores through the insulating layer properly explains the experimental observations, but, at high field, a linear contribution dominates the MR. The latter behaviour can be understood by assuming second-order tunnelling.

  8. Beam physics design strategy for a high-current rf linac

    SciTech Connect

    Reiser, M.

    1995-10-01

    The high average beam power of an rf linac system for transmutation of nuclear waste puts very stringent requirements on beam quality and beam control. Fractional beam losses along the accelerator must be kept at extremely low levels to assure {open_quotes}hands-on{close_quotes} maintenance. Hence, halo formation and large-amplitude tails in the particle distribution due to beam mismatch and equipartitioning effects must be avoided. This implies that the beam should ideally be in near-perfect thermal equilibrium from injection to full energy - in contrast to existing rf linacs in which the transverse temperature, T {sub {perpendicular}}, is higher than the longitudinal temperature, T{sub {parallel}}. The physics and parameter scaling for such a system will be reviewed using the results of recent work on high-intensity bunched beams. A design strategy for a high-current rf linac with equilibrated beam will be proposed.

  9. A diagnostic system for electrical faults in a high current discharge plasma setup.

    PubMed

    Nigam, S; Aneesh, K; Navathe, C P; Gupta, P D

    2011-02-01

    A diagnostic system to detect electrical faults inside a coaxial high current discharge device is presented here. This technique utilizes two biconical antennas picking up electromagnetic radiation from the discharge device, a voltage divider sensing input voltage, and a Rogowski coil measuring the main discharge current. A computer program then analyses frequency components in these signals and provides information as to whether the discharge event was normal or any breakdown fault occurred inside the coaxial device. The diagnostic system is developed for a 450 kV and 50 kA capillary discharge plasma setup. For the setup various possible faults are analyzed by electrical simulation, followed by experimental results. In the case of normal discharge through the capillary load the dominant frequency is ∼4 MHz. Under faulty conditions, the peak in magnitude versus frequency plot of the antenna signal changes according to the fault position which involves different paths causing variation in the equivalent circuit elements.

  10. Update on the high-current injector for the Stanford Linear collider

    SciTech Connect

    James, M.B.; Clendenin, J.E.; Ecklund, S.D.; Miller, R.H.; Sheppard, J.C.; Sinclair, C.K.; Sodja, J.

    1983-03-01

    The high current injector has become operational. There are two crucial areas where improvements must be made to meet collider specifications: while the injector can produce up to 10/sup 11/ e/sup -/ in a single S-band bucket, initially much of this charge was captured in a low energy tail and was this not suitable for transport through the accelerator and injection into the damping ring. Pulse to pulse position jitter has been observed, resulting in transverse wake field which increases beam emittance. The problems described above contribute to substantial current loss during transport from the injector (40 MeV) to the SLC damping ring (1.2 GeV). Experimental studies are continuing with the aim of understanding and improving beam characteristics including bunch length, pulse to pulse stability and emittance. The present status of these studies is reported.

  11. Superconducting Accelerating Structure for High-Current Cyclotrons for Accelerator-Driven Subcritical Fission

    NASA Astrophysics Data System (ADS)

    Pogue, Nathaniel; McIntyre, Peter; Sattarov, Akhdiyor

    2011-10-01

    An accelerator driven molten salt fission core is being designed to provide reliable power by subcritical nuclear fission for the next few millennia. Fission is driven by proton beams from a flux-coupled stack of three high-current cyclotrons. A key innovation in attaining the needed beam current and efficiency is a superconducting Niobium rf accelerating cavity that can accelerate bunches in the 200 orbits uniformly. The unique design allows for several cavities to be stacked, and also provides uniform acceleration and eliminates higher order modes in the cyclotron. The design and properties of the superconducting cavity will increase the efficiency of the cyclotron and the overall energy amplification from the molten salt core by an order of magnitude compared to conventional designs.

  12. Mechanisms of microstructure formations in M50 steel melted layer by high current pulsed electron beam

    NASA Astrophysics Data System (ADS)

    Tang, Guangze; Xu, Fangjun; Fan, Guohua; Ma, Xinxin; Wang, Liqin

    2012-10-01

    In the present paper, surface melting of the M50 steel was carried out by high current pulsed electron beam (HCPEB). The microstructure evolution in the melted layer was observed using TEM. It is confirmed that the dissolution of the carbides and the diffusion of alloy elements play a determining role on the microstructure evolution. After one pulse irradiation, a mixture of twinned martensite and irregular cellular domains of austenite is observed in the melted layer due to the insufficient diffusion of alloy elements around initial carbides. The zone around initial carbides with high alloy elements content keeps as residual austenite, the zone with low alloy elements content transform into twinned martensite. When the irradiation number increases to 30 pulses, the alloy elements will diffuse into the whole melted layer. And the melted layer consists completely of cellular austenite grains with a diameter of about 150 nm. The boundary between austenite grains is amorphous structure with little higher alloy elements content.

  13. Plasma Emission Characteristics From a High Current Hollow Cathode in an Ion Thruster Discharge Chamber

    NASA Astrophysics Data System (ADS)

    Foster, John E.; Patterson, Michael J.

    2002-11-01

    The presence of energetic ions produced by a hollow cathodes operating at high emission currents (greater than 5A) has been documented in the literature. In order to further elucidate these findings, an investigation of a high current cathode operating in an ion thruster discharge chamber has been undertaken. Using Langmuir probes, a low energy charged particle analyzer and emission spectroscopy, the behavior of the near-cathode plasma and the emitted ion energy distribution was characterized. The presence of energetic ions was confirmed. It was observed that these ions had energies in excess of the discharge voltage and thus cannot be simply explained by ions falling out of plasma through a potential difference of this order. Additionally, evidence provided by Langmuir probes suggests the existence of a double layer essentially separating the hollow cathode plasma column from the main discharge. The radial potential difference associated with this double layer was measured to be of order the ionization potential.

  14. Electro-mechanical properties of composite materials for high-current contact applications

    NASA Astrophysics Data System (ADS)

    Jaćimović, J.; Felberbaum, L.; Giannini, E.; Teyssier, J.

    2014-03-01

    We report a detailed study that compares various composite materials (CM): Ag/ZnO, Ag/SnO2, Ag/C, Ag/WC, Ag/WC-C and Ag/Ni used in high-current dc circuit breaker applications. Their structural, mechanical, electrical and wetting properties were investigated. In parallel, switching operation tests on the same compounds were performed on commercial high-speed circuit breakers under real conditions (30 kA-900 V). A correlation between the microscopic variables and switching performances of the CMs was established. Materials like Ag/WC and Ag/WC-C were found to be unsuitable for the reliable functionality of the device. In contrast, Ag/C and Ag/SnO2 materials with high electrical and high thermal conductivity revealed remarkably good behaviour during switching operation tests.

  15. Mathematical modeling of SF{sub 6} puffer circuit breakers. 1: High current region

    SciTech Connect

    Park, K.Y.; Fang, M.T.C.

    1996-04-01

    A mathematical arc model based on the integral method has been developed to study the arc behavior of SF{sub 6} puffer circuit breakers during high current region. The interaction between the compression chamber and the arc interrupter plays a critical role in determining the arc behavior. Computations have been carried out for the puffer circuit breaker of Noeske et al. The aerodynamic behavior and electrical characteristics of the puffer circuit breaker have been investigated. In addition, the pressure rise in the compression chamber and arc voltage have been computed and the results compared with the available experimental results of Noeske et al. Special attention has been paid to the presence of the shock.

  16. Transport and Measurements of High-Current Electron Beams from X pinches

    SciTech Connect

    Agafonov, Alexey V.; Mingaleev, Albert R.; Romanova, Vera M.; Tarakanov, Vladimir P.; Shelkovenko, Tatiana A.; Pikuz, Sergey A.; Blesener, Isaac C.; Kusse, Bruce R.; Hammer, David A.

    2009-01-21

    Generation of electron beams is an unavoidable property of X-pinches and other pulsed-power-driven pinches of different geometry. Some issues concerning high-current electron beam transport from the X pinch to the diagnostic system and measurements of the beam current by Faraday cups with different geometry's are discussed. Of particular interest is the partially neutralized nature of the beam propagating from the X-pinch to a diagnostic system. Two scenarios of electron beam propagation from X-pinch to Faraday cup are analyzed by means of computer simulation using the PIC-code KARAT. The first is longitudinal neutralization by ions extracted from plasma at an output window of the X-pinch diode; the second is the beam transport through a plasma background between the diode and a diagnostic system.

  17. Microstructure Analysis of HPb59-1 Brass Induced by High Current Pulsed Electron Beam

    NASA Astrophysics Data System (ADS)

    Lyu, Jike; Gao, Bo; Hu, Liang; Lu, Shuaidan; Tu, Ganfeng

    2016-08-01

    In this paper, the effects of high current pulsed electron beam (HCPEB) on the microstructure evolution of casting HPb59-1 (Cu 57.1 mass%, Pb 1.7 mass% and Zn balance) alloy were investigated. The results showed a "wavy" surface which was formed with Pb element existing in the forms of stacking block and microparticles on the top surface layer after treatment. Nanocrystalline structures including Pb grains and two phases (α and β) were formed on the top remelted layer and their sizes were all less than 100 nm. The disordered β phase was generated in the surface layer after HCPEB treatment, which is beneficial for the improvement of surface properties. Meanwhile, there was a large residual stress on the alloy surface, along with the appearance of microcracks, and the preferred orientations of grains also changed.

  18. Enabling cost-effective high-current burst-mode operation in superconducting accelerators

    SciTech Connect

    Sheffield, Richard L.

    2015-06-01

    Superconducting (SC) accelerators are very efficient for CW or long-pulse operation, and normal conducting (NC) accelerators are cost effective for short-pulse operation. The addition of a short NC linac section to a SC linac can correct for the energy droop that occurs when pulsed high-current operation is required that exceeds the capability of the klystrons to replenish the cavity RF fields due to the long field fill-times of SC structures, or a requirement to support a broad range of beam currents results in variable beam loading. This paper describes the implementation of this technique to enable microseconds of high beam-current, 90 mA or more, in a 12 GeV SC long-pulse accelerator designed for the MaRIE 42-keV XFEL proposed for Los Alamos National Laboratory.

  19. Optimal conditions for high current proton irradiations at the university of Wisconsin's ion beam laboratory

    SciTech Connect

    Wetteland, C. J.; Field, K. G.; Gerczak, T. J.; Eiden, T. J.; Maier, B. R.; Albakri, O.; Sridharan, K.; Allen, T. R.

    2013-04-19

    The National Electrostatics Corporation's (NEC) Toroidal Volume Ion Source (TORVIS) source is known for exceptionally high proton currents with minimal service downtime as compared to traditional sputter sources. It has been possible to obtain over 150{mu}A of proton current from the source, with over 70{mu}A on the target stage. However, beam fluxes above {approx}1 Multiplication-Sign 10{sup 17}/m2-s may have many undesirable effects, especially for insulators. This may include high temperature gradients at the surface, sputtering, surface discharge, cracking or even disintegration of the sample. A series of experiments were conducted to examine the role of high current fluxes in a suite of ceramics and insulating materials. Results will show the optimal proton irradiation conditions and target mounting strategies needed to minimize unwanted macro-scale damage, while developing a procedure for conducting preliminary radiation experiments.

  20. Beam extraction and high stability operation of high current electron cyclotron resonance proton ion source

    SciTech Connect

    Roychowdhury, P. Mishra, L.; Kewlani, H.; Mittal, K. C.; Patil, D. S.

    2014-03-15

    A high current electron cyclotron resonance proton ion source is designed and developed for the low energy high intensity proton accelerator at Bhabha Atomic Research Centre. The plasma discharge in the ion source is stabilized by minimizing the reflected microwave power using four stub auto tuner and magnetic field. The optimization of extraction geometry is performed using PBGUNS code by varying the aperture, shape, accelerating gap, and the potential on the electrodes. While operating the source, it was found that the two layered microwave window (6 mm quartz plate and 2 mm boron nitride plate) was damaged (a fine hole was drilled) by the back-streaming electrons after continuous operation of the source for 3 h at beam current of 20–40 mA. The microwave window was then shifted from the line of sight of the back-streaming electrons and located after the water-cooled H-plane bend. In this configuration the stable operation of the high current ion source for several hours is achieved. The ion beam is extracted from the source by biasing plasma electrode, puller electrode, and ground electrode to +10 to +50 kV, −2 to −4 kV, and 0 kV, respectively. The total ion beam current of 30–40 mA is recorded on Faraday cup at 40 keV of beam energy at 600–1000 W of microwave power, 800–1000 G axial magnetic field and (1.2–3.9) × 10{sup −3} mbar of neutral hydrogen gas pressure in the plasma chamber. The dependence of beam current on extraction voltage, microwave power, and gas pressure is investigated in the range of operation of the ion source.

  1. Beam extraction and high stability operation of high current electron cyclotron resonance proton ion source

    NASA Astrophysics Data System (ADS)

    Roychowdhury, P.; Mishra, L.; Kewlani, H.; Patil, D. S.; Mittal, K. C.

    2014-03-01

    A high current electron cyclotron resonance proton ion source is designed and developed for the low energy high intensity proton accelerator at Bhabha Atomic Research Centre. The plasma discharge in the ion source is stabilized by minimizing the reflected microwave power using four stub auto tuner and magnetic field. The optimization of extraction geometry is performed using PBGUNS code by varying the aperture, shape, accelerating gap, and the potential on the electrodes. While operating the source, it was found that the two layered microwave window (6 mm quartz plate and 2 mm boron nitride plate) was damaged (a fine hole was drilled) by the back-streaming electrons after continuous operation of the source for 3 h at beam current of 20-40 mA. The microwave window was then shifted from the line of sight of the back-streaming electrons and located after the water-cooled H-plane bend. In this configuration the stable operation of the high current ion source for several hours is achieved. The ion beam is extracted from the source by biasing plasma electrode, puller electrode, and ground electrode to +10 to +50 kV, -2 to -4 kV, and 0 kV, respectively. The total ion beam current of 30-40 mA is recorded on Faraday cup at 40 keV of beam energy at 600-1000 W of microwave power, 800-1000 G axial magnetic field and (1.2-3.9) × 10-3 mbar of neutral hydrogen gas pressure in the plasma chamber. The dependence of beam current on extraction voltage, microwave power, and gas pressure is investigated in the range of operation of the ion source.

  2. Beam extraction and high stability operation of high current electron cyclotron resonance proton ion source.

    PubMed

    Roychowdhury, P; Mishra, L; Kewlani, H; Patil, D S; Mittal, K C

    2014-03-01

    A high current electron cyclotron resonance proton ion source is designed and developed for the low energy high intensity proton accelerator at Bhabha Atomic Research Centre. The plasma discharge in the ion source is stabilized by minimizing the reflected microwave power using four stub auto tuner and magnetic field. The optimization of extraction geometry is performed using PBGUNS code by varying the aperture, shape, accelerating gap, and the potential on the electrodes. While operating the source, it was found that the two layered microwave window (6 mm quartz plate and 2 mm boron nitride plate) was damaged (a fine hole was drilled) by the back-streaming electrons after continuous operation of the source for 3 h at beam current of 20-40 mA. The microwave window was then shifted from the line of sight of the back-streaming electrons and located after the water-cooled H-plane bend. In this configuration the stable operation of the high current ion source for several hours is achieved. The ion beam is extracted from the source by biasing plasma electrode, puller electrode, and ground electrode to +10 to +50 kV, -2 to -4 kV, and 0 kV, respectively. The total ion beam current of 30-40 mA is recorded on Faraday cup at 40 keV of beam energy at 600-1000 W of microwave power, 800-1000 G axial magnetic field and (1.2-3.9) × 10(-3) mbar of neutral hydrogen gas pressure in the plasma chamber. The dependence of beam current on extraction voltage, microwave power, and gas pressure is investigated in the range of operation of the ion source.

  3. Magnetron sputtering system for coatings deposition with activation of working gas mixture by low-energy high-current electron beam

    NASA Astrophysics Data System (ADS)

    Gavrilov, N. V.; Kamenetskikh, A. S.; Men'shakov, A. I.; Bureyev, O. A.

    2015-11-01

    For the purposes of efficient decomposition and ionization of the gaseous mixtures in a system for coatings deposition using reactive magnetron sputtering, a low-energy (100-200 eV) high-current electron beam is generated by a grid-stabilized plasma electron source. The electron source utilizes both continuous (up to 20 A) and pulse-periodic mode of discharge with a self-heated hollow cathode (10-100 A; 0.2 ms; 10-1000 Hz). The conditions for initiation and stable burning of the high-current pulse discharge are studied along with the stable generation of a low-energy electron beam within the gas pressure range of 0.01 - 1 Pa. It is shown that the use of the electron beam with controllable parameters results in reduction of the threshold values both for the pressure of gaseous mixture and for the fluxes of molecular gases. Using such a beam also provides a wide range (0.1-10) of the flux density ratios of ions and sputtered atoms over the coating surface, enables an increase in the maximum pulse density of ion current from plasma up to 0.1 A, ensures an excellent adhesion, optimizes the coating structure, and imparts improved properties to the superhard nanocomposite coatings of (Ti,Al)N/a-Si3N4 and TiC/-a-C:H. Mass-spectrometric measurements of the beam-generated plasma composition proved to demonstrate a twofold increase in the average concentration of N+ ions in the Ar-N2 plasma generated by the high-current (100 A) pulsed electron beam, as compared to the dc electron beam.

  4. Formation of microcraters and hierarchically-organized surface structures in TiNi shape memory alloy irradiated with a low-energy, high-current electron beam

    SciTech Connect

    Meisner, L. L. Meisner, S. N.; Markov, A. B. Ozur, G. E. Yakovlev, E. V.; Rotshtein, V. P.; Gudimova, E. Yu.

    2015-10-27

    The regularities of surface cratering in TiNi alloy irradiated with a low-energy, high-current electron beam (LEHCEB) in dependence on energy density and number of pulses are studied. LEHCEB processing of TiNi samples was carried out using RITM-SP facility. Energy density E{sub s} was varied from 1 to 5 J/cm{sup 2}, pulse duration was 2.5–3.0 μs, the number of pulses n = 1–128. The dominant role of non-metallic inclusions [mainly, TiC(O)] in the nucleation of microcraters was found. It was revealed that at small number of pulses (n = 2), an increase in energy density leads both to increasing average diameter and density of microcraters. An increase in the number of pulses leads to a monotonic decrease in density of microcraters, and, therefore, that of the proportion of the area occupied by microcraters, as well as a decrease in the surface roughness. The multiple LEHCEB melting of TiNi alloy in crater-free modes enables to form quasi-periodical, hierarchically-organized microsized surface structures.

  5. Characterization of Prototype Superconducting Magnetic Quadrupolesfor the High Current Transport Experiment

    SciTech Connect

    Lund, Steven M.; Sabbi, GianLuca; Seidl, Peter

    2001-02-22

    Later phases of the High Current Transport Experiment (HCX) at LBNL will employ superconducting magnetic quadrupole lenses to focus an intense, heavy-ion beam over approximately 50 lattice periods (100 quadrupoles). Here they present a characterization of a baseline quadrupole design suitable for transporting a single, low-energy ({approx} 2 MeV), high-current ({approx} 800 mA) heavy-ion (K{sup +}) beam that will be provided from an existing injector and beam matching section. For optimal performance in this application, a compact quadrupole magnet providing high focusing strength and high field quality is required. The reference parameters that they have chosen take into account magnet development work by AML, LLNL, and MIT and result in a transport lattice well matched to programmatic needs with a lattice period of approximately 50 cm. The goal of this note is to introduce a common framework where the magnetic performance of different designs can be compared. In that regard, they try to avoid the details of an earlier parameter note [1] where provisions for tweaks in magnet excitation, cryostat assembly, etc. were discussed in fairly general terms. This note is not intended to be a final specification for the HCX quadrupoles to be constructed or to be the sole basis on which competing magnet designs will be compared. Other aspects such as prototype test results, economic considerations, and attractiveness within the context of ultimate applications in multi-beam drivers for heavy-ion fusion (i.e, compatibility with magnet arrays, etc.) will all factor in the selection of the appropriate design option. This note is organized as follows. Magnet characterizations including geometric and conductor parameters are given in Sec II. Performance parameters to be reported that quantify the magnet properties are outlined in Sec III. Supporting information is included in appendices. A reference coordinate system to be employed in field calculations is defined in Appendix A

  6. Integrating a Machine Protection System for High-Current Free Electron Lasers and Energy Recovery Linacs

    SciTech Connect

    Trent Allison; James Coleman; Richard Evans; Al Grippo; Kevin Jordan

    2002-09-01

    A fully integrated Machine Protection System (MPS) is critical to efficient commissioning and safe operation of all high-current accelerators. The MPS needs to monitor the status of all devices that could enter the beam path, the beam loss monitors (BLMs), magnet settings, beam dump status, etc. This information is then presented to the electron source controller, which must limit the beam power or shut down the beam completely. The MPS for the energy recovery linac (ERL) at the Jefferson Lab Free Electron Laser [1] generates eight different power limits, or beam modes, which are passed to the drive laser pulse controller (DLPC) (photocathode source controller). These range from no beam to nearly 2 megawatts of electron beam power. Automatic masking is used for the BLMs during low-power modes when one might be using beam viewers. The system also reviews the setup for the two different beamlines, the IR path or the UV path, and will allow or disallow operations based on magnet settings and valve positions. This paper will describe the approach taken for the JLab 10-kW FEL. Additional details can be found on our website http://laser.jlab.org [2].

  7. A superconducting quadrupole array for transport of multiple high current beams

    SciTech Connect

    Faltens, A.; Shuman, D.

    1999-11-01

    We present a conceptual design of a superconducting quadrupole magnet array for the side-by-side transport of multiple high current particle beams in induction linear accelerators. The magnetic design uses a modified cosine 20 current distribution inside a square cell boundary. Each interior magnet's neighbors serve as the return flux paths and the poles are placed as close as possible to each other to facilitate this. No iron is present in the basic 2-D magnetic design; it will work at any current level without correction windings. Special 1/8th quadrupoles are used along the transverse periphery of the array to contain and channel flux back into the array, making every channel look as part of an infinite array. This design provides a fixed dimension array boundary equal to the quadrupole radius that can be used for arrays of any number of quadrupole channels, at any field level. More importantly, the design provides magnetic field separation between the array and the induction cores which may be surrounding it. Flux linkage between these two components can seriously affect the operation of both of them.

  8. Deformation of contact surfaces in a vacuum interrupter after high-current interruptions

    NASA Astrophysics Data System (ADS)

    Wang, Haoran; Wang, Zhenxing; Zhou, Zhipeng; Jiang, Yanjun; Wang, Jianhua; Geng, Yingsan; Liu, Zhiyuan

    2016-08-01

    In a high-current interruption, the contact surface in a vacuum interrupter might be severely damaged by constricted vacuum arcs causing a molten area on it. As a result, a protrusion will be initiated by a transient recovery voltage after current zero, enhancing the local electric field and making breakdowns occur easier. The objective of this paper is to simulate the deformation process on the molten area under a high electric field by adopting the finite element method. A time-dependent Electrohydrodynamic model was established, and the liquid-gas interface was tracked by the level-set method. From the results, the liquid metal can be deformed to a Taylor cone if the applied electric field is above a critical value. This value is correlated to the initial geometry of the liquid metal, which increases as the size of the liquid metal decreases. Moreover, the buildup time of a Taylor cone obeys the power law t = k × E-3, where E is the initial electric field and k is a coefficient related to the material property, indicating a temporal self-similar characteristic. In addition, the influence of temperature has little impact on the deformation but has great impact on electron emission. Finally, the possible reason to initiate a delayed breakdown is associated with the deformation. The breakdown does not occur immediately when the voltage is just applied upon the gap but is postponed to several milliseconds later when the tip is formed on the liquid metal.

  9. High Current ESD Test of Advanced Triple Junction Solar Array Coupon

    NASA Technical Reports Server (NTRS)

    Wright, Kenneth H., Jr.; Schneider, Todd A.; Vaughn, Jason A.; Hoang, Bao; Wong, Frankie

    2014-01-01

    Testing was conducted on an Advanced Triple Junction (ATJ) coupon that was part of a risk reduction effort in the development of a high-powered solar array design by Space Systems Loral, LLC (SSL). The ATJ coupon was a small, 4-cell, two-string configuration of flight-type design that has served as the basic test coupon design used in previous SSL environmental aging campaigns. The objective of the present test was to evaluate the performance of the coupon after being subjected to induced electrostatic discharge (ESD) testing at two string voltages (100 V, 150 V) and four string currents (1.65 A, 2.0 A, 2.475 A, and 3.3 A). An ESD test circuit, unique to SSL solar array design, was built that simulates the effect of missing cells and strings in a full solar panel with special primary arc flashover circuitry. A total of 73 primary arcs were obtained that included 7 temporary sustained arcs (TSA) events. The durations of the TSAs ranged from 50 micro-seconds to 2.75 milli-seconds. All TSAs occurred at a string voltage of 150 V. Post-ESD functional testing showed that no degradation occurred due to the TSA events. These test results point to a robust design for application to a high-current, high-power mission.

  10. High current multicharged metal ion source using high power gyrotron heating of vacuum arc plasma.

    PubMed

    Vodopyanov, A V; Golubev, S V; Khizhnyak, V I; Mansfeld, D A; Nikolaev, A G; Oks, E M; Savkin, K P; Vizir, A V; Yushkov, G Yu

    2008-02-01

    A high current, multi charged, metal ion source using electron heating of vacuum arc plasma by high power gyrotron radiation has been developed. The plasma is confined in a simple mirror trap with peak magnetic field in the plug up to 2.5 T, mirror ratio of 3-5, and length variable from 15 to 20 cm. Plasma formed by a cathodic vacuum arc is injected into the trap either (i) axially using a compact vacuum arc plasma gun located on axis outside the mirror trap region or (ii) radially using four plasma guns surrounding the trap at midplane. Microwave heating of the mirror-confined, vacuum arc plasma is accomplished by gyrotron microwave radiation of frequency 75 GHz, power up to 200 kW, and pulse duration up to 150 micros, leading to additional stripping of metal ions by electron impact. Pulsed beams of platinum ions with charge state up to 10+, a mean charge state over 6+, and total (all charge states) beam current of a few hundred milliamperes have been formed.

  11. A cookbook for building a high-current dimpled H– magnetron source for accelerators

    DOE PAGES

    Bollinger, Daniel S.; Karns, Patrick R.; Tan, Cheng -Yang

    2015-10-30

    A high-current (>50 mA) dimpled H– magnetron source has been built at Fermilab for supplying H– beam to the entire accelerator complex. Despite many decades of expertise with slit H– magnetron sources at Fermilab, we were faced with many challenges from the dimpled H– magnetron source, which needed to be overcome in order to make it operational. Dimpled H– sources for high-energy physics are not new: Brookhaven National Laboratory has operated a dimpled H- source for more than two decades. However, the transference of that experience to Fermilab took about two years because a cookbook for building this type ofmore » source did not exist and seemingly innocuous or undocumented choices had a huge impact on the success or failure for this type of source. Moreover, it is the goal of this paper to document the reasons for these choices and to present a cookbook for building and operating dimpled H– magnetron sources.« less

  12. NOx Removal by Pulsed High Current Electron Beam in Combination with Photocatalyst

    NASA Astrophysics Data System (ADS)

    Nakagawa, Yoshiro; Mannami, Atushi; Natsuno, Hideshi; Nishikata, Satoshi

    2002-03-01

    A new flue gas treatment device using a pulsed high current electron beam in combination with a photocatalyst (TiO2) was investigated. When the pulsed electron beam (100 keV, 120 A, 1 μs and 4.7 J/pulse) was injected into the gas chamber with a TiO2 sheet on the inner wall, NOx in a 5% oxygen mixed NO (=200 ppm)/N2 gas was removed with the energy efficiency of removal as high as 1010 nmol/J at a removal ratio of 83%, in which the amount of NOx removed in 10 min without any radiation, about 25% of the initial NO concentration, was not included in the energy efficiency calculation. The concentration of NO2 was below about 3 ppm in this process, which was a significant characteristic of NOx removal in this device. When the flowing 4% oxygen mixed NO (=200 ppm)/N2 gas at a flow rate 1.4 L/min was irradiated by successive pulses of the electron beam, the energy efficiency of removal of 864 nmol/J at the removal ratio of 41% was obtained.

  13. Development and fabrication of a high current, fast recovery power diode

    NASA Technical Reports Server (NTRS)

    Berman, A. H.; Balodis, V.; Devance, D. C.; Gaugh, C. E.; Karlsson, E. A.

    1983-01-01

    A high voltage (VR = 1200 V), high current (IF = 150 A), fast recovery ( 700 ns) and low forward voltage drop ( 1.5 V) silicon rectifier was designed and the process developed for its fabrication. For maximum purity, uniformity and material characteristic stability, neutron transmutation n-type doped float zone silicon is used. The design features a hexagonal chip for maximum area utilization of space available in the DO-8 diode package, PIN diffused junction structure with deep diffused D(+) anode and a shallow high concentration n(+) cathode. With the high temperature glass passivated positive bevel mesa junction termination, the achieved blocking voltage is close to the theoretical limit of the starting material. Gold diffusion is used to control the lifetime and the resulting effect on switching speed and forward voltage tradeoff. For solder reflow assembly, trimetal (Al-Ti-Ni) contacts are used. The required major device electrical characteristics were achieved. Due to the tradeoff nature of forward voltage drop and reverse recovery time, a compromise was reached for these values.

  14. High current SRF cavity design for SPL and eRHIC

    SciTech Connect

    Xu, W.; Ben-Zvi, I.; Belomenstnykh, S.; Calaga, R.; Hahn, H.; Johnson, E.; Kewisch, J.

    2011-03-28

    A high current five-cell Nb superconducting cavity, called BNL3 cavity, was optimized and designed for the SPL and eRHIC. For the fundamental mode, the optimization process aimed at maximizing the R/Q of the fundamental mode and the geometry factor G under an acceptable RF field ratio level of B{sub peak}/E{sub acc} and E{sub peak}/E{sub acc}. For higher order modes, the optimization is to lower (R/Q)Q{sub ext} for dipole and quadrupole modes to suppress the beam-break-up (BBU). To extract the HOM power out of the cavity, the BNL3 cavity employs a larger beam pipe, allowing the propagation of HOMs, but not the fundamental mode. Six HOM couplers (three at each end) are used to extract large HOM power. To avoid the cross-talk between cavities, tapers are employed between the cavities. This paper presents the design of the BNL3 cavity, end groups and BBU simulation results.

  15. STUDY OF HIGHER ORDER MODES IN HIGH CURRENT MULTICELL SRF CAVITIES.

    SciTech Connect

    CALAGA,R.BEN-ZVI,I.ZHAO,Y.WANG,D.SEKUTOWICZ,J.WU,G.

    2003-09-08

    The electron cooling project for RHIC luminosity upgrade and future projects such as eRHIC (electron-ion collider) demand cavities operating at high average current and high bunch charge in CW energy recovery mode. This paper describes the investigation of Higher Order Modes (HOMs) in such a cavity. This work is part of an ongoing effort to develop a 5-cell superconducting cavity for such high current and high bunch charge energy-recovery superconducting linac. The frequency of the cavity is 703.75 MHz with an iris of 17cm and two ferrite absorbers for HOM damping. The main focus of this paper is to identify and investigate possible trapped HOM modes that might result in multibunch instabilities. Detailed MAFIA calculations were performed using the e-module for different end cell geometries. Results from these calculations will be presented. Beam breakup results using TDBBU due to dipole HOM's will also be presented. A beam breakup threshold of above 1.8 A was calculated.

  16. Hybrid monitor for both beam position and tilt of pulsed high-current beams

    SciTech Connect

    Pang, J. He, X.; Ma, C.; Zhao, L.; Li, Q.; Dai, Z.

    2014-09-15

    A Hybrid beam monitor, integrated with both azimuthal and axial B-dot probes, was designed for simultaneous measurement of both beam position and beam angle for pulsed high-current beams at the same location in beam pipe. The output signals of axial B-dot probes were found to be mixed with signals caused by transverse position deviation. In order to eliminate the unwanted signals, an elimination method was developed and its feasibility tested on a 50-Ω coaxial line test stand. By this method, a waveform, shape-like to that of input current and proportional to the tilt angle, was simulated and processed by following integration step to achieve the tilt angle. The tests showed that the measurement error of displacement and tilt angle less than 0.3 mm and 1.5 mrad, respectively. The latter error could be reduced with improved probes by reducing the inductance of the axial B-dot probe, but the improvement reached a limit due to some unknown systemic mechanism.

  17. Rare Earth Metal Silicides Synthesized by High Current Metal Ion Implantation

    NASA Astrophysics Data System (ADS)

    Cheng, X. Q.; Wang, R. S.; Tang, X. J.; Liu, B. X.

    2003-08-01

    The YSi2, LaSi2, CeSi2, PrSi2, NdSi2, SmSi2, GdSi2, TbSi2, DySi2, and ErSi2 layers were formed on Si wafers by respective high current metal-ion implantation using a metal vacuum vapor arc (MEVVA) ion source and the formation temperature was considerable lower than the critical temperatures (300-350°C) required for the rare earth metal silicides by solid-state reaction. It was found that the crystalline structures could be improved with increasing slightly the formation temperature as well as the implantation dose. Concerning the growth kinetics, in some cases, fractal patterns were observed on Si surfaces and the branches of the fractals consisted of the grains of respective precipitated silicides. Interestingly, the fractal dimension increased with formation temperature and eventually approached to a value of 2.0, corresponding to a continuous layer, which was required in practical application. The formation mechanism as well as the growth kinetics was discussed in terms of the far-from-equilibrium process involved in the MEVVA ion implantation.

  18. Model of convection mass transfer in titanium alloy at low energy high current electron beam action

    NASA Astrophysics Data System (ADS)

    Sarychev, V. D.; Granovskii, A. Yu; Nevskii, S. A.; Konovalov, S. V.; Gromov, V. E.

    2017-01-01

    The convection mixing model is proposed for low-energy high-current electron beam treatment of titanium alloys, pre-processed by heterogeneous plasma flows generated via explosion of carbon tape and powder TiB2. The model is based on the assumption vortices in the molten layer are formed due to the treatment by concentrated energy flows. These vortices evolve as the result of thermocapillary convection, arising because of the temperature gradient. The calculation of temperature gradient and penetration depth required solution of the heat problem with taking into account the surface evaporation. However, instead of the direct heat source the boundary conditions in phase transitions were changed in the thermal conductivity equation, assuming the evaporated material takes part in the heat exchange. The data on the penetration depth and temperature distribution are used for the thermocapillary model. The thermocapillary model embraces Navier-Stocks and convection heat transfer equations, as well as the boundary conditions with the outflow of evaporated material included. The solution of these equations by finite elements methods pointed at formation of a multi-vortices structure when electron-beam treatment and its expansion over new zones of material. As the result, strengthening particles are found at the depth exceeding manifold their penetration depth in terms of the diffusion mechanism.

  19. Current halo structures in high-current plasma experiments: {theta}-pinch

    SciTech Connect

    Matveev, Yu. V.

    2007-03-15

    Experimental data elucidating mechanisms for halo formation in {theta}-pinch discharges are presented and discussed. The experiments were performed with different gases (H{sub 2}, D{sub 2}, He, and Ar) in a theta-pinch device with a porcelain vacuum chamber and an excitation coil 15 cm in diameter and 30 cm in length. The stored energy, the current in the excitation coil, and the current half-period were W = 10 kJ, I = 400 kA, and T/2 = 14 {mu}s, respectively. It is found that the plasma rings (halos) surrounding the pinch core arise as a result of coaxial pinch stratification due to both the excitation of closed currents (inductons) inside the pinch and the radial convergence of the plasma current sheaths produced after the explosion of T-layers formed near the wall in the initial stage of the discharge. It is concluded that halo structures observed in pinches, tokamaks, and other high-current devices used in controlled fusion research have the same nature.

  20. Comparison of Electron Cloud Simulation and Experiments in the High-Current Experiment

    SciTech Connect

    Cohen, R; Friedman, A; Covo, M K; Lund, S; Molvik, A; Bieniosek, F; Seidl, P; Vay, J; Verboncoeur, J; Stoltz, P; Veitzer, S

    2004-10-07

    A set of experiments has been performed on the High-Current Experiment (HCX) facility at LBNL, in which the ion beam is allowed to collide with an end plate and thereby induce a copious supply of desorbed electrons. Through the use of combinations of biased and grounded electrodes positioned in between and downstream of the quadrupole magnets, the flow of electrons upstream into the magnets can be turned on or off. Properties of the resultant ion beam are measured under each condition. The experiment is modeled via a full three-dimensional, two species (electron and ion) particle simulation, as well as via reduced simulations (ions with appropriately chosen model electron cloud distributions, and a high-resolution simulation of the region adjacent to the end plate). The three-dimensional simulations are the first of their kind and the first to make use of a timestep-acceleration scheme that allows the electrons to be advanced with a timestep that is not small compared to the highest electron cyclotron period. The simulations reproduce qualitative aspects of the experiments, illustrate some unanticipated physical effects, and serve as an important demonstration of a developing simulation capability.

  1. Comparison of electron cloud simulation and experiments in the high-current experiment

    SciTech Connect

    Cohen, R.H.; Friedman, A.; Covo, M. Kireeff; Lund, S.M.; Molvik, A.W.; Bieniosek, F.M.; Seidl, P.A.; Vay, J.-L.; Verboncoeur, J.; Stoltz, P.; Veitzer, S.

    2004-08-27

    A set of experiments has been performed on the High-Current Experiment (HCX) facility at LBNL, in which the ion beam is allowed to collide with an end plate and thereby induce a copious supply of desorbed electrons. Through the use of combinations of biased and grounded electrodes positioned in between and downstream of the quadrupole magnets, the flow of electrons upstream into the magnets can be turned on or off. Properties of the resultant ion beam are measured under each condition. The experiment is modeled via a full three-dimensional, two species (electron and ion) particle simulation, as well as via reduced simulations (ions with appropriately chosen model electron cloud distributions, and a high-resolution simulation of the region adjacent to the end plate). The three-dimensional simulations are the first of their kind and the first to make use of a timestep-acceleration scheme that allows the electrons to be advanced with a timestep that is not small compared to the highest electron cyclotron period. The simulations reproduce qualitative aspects of the experiments, illustrate some unanticipated physical effects, and serve as an important demonstration of a developing simulation capability.

  2. A strong-focusing 800 MeV cyclotron for high-current applications

    NASA Astrophysics Data System (ADS)

    Pogue, N.; Assadi, S.; Badgley, K.; Comeaux, J.; Kellams, J.; McInturff, A.; McIntyre, P.; Sattarov, A.

    2013-04-01

    A superconducting strong-focusing cyclotron (SFC) is being developed for high-current applications. It incorporates four innovations. Superconducting quarter-wave cavities are used to provide >20 MV/turn acceleration. The orbit separation is thereby opened so that bunch-bunch interactions between successive orbits are eliminated. Quadrapole focusing channels are incorporated within the sectors so that alternating-gradient strong-focusing transport is maintained throughout. Dipole windings on the inner and outer orbits provide enhanced control for injection and extraction of bunches. Finally each sector magnet is configured as a flux-coupled stack of independent apertures, so that any desired number of independent cyclotrons can be integrated within a common footprint. Preliminary simulations indicate that each SFC should be capable of accelerating 10 mA CW to 800 MeV with very low loss and >50% energy efficiency. A primary motivation for SFC is as a proton driver for accelerator-driven subcritical fission in a molten salt core. The cores are fueled solely with the transuranics from spent nuclear fuel from a conventional nuclear power plant. The beams from one SFC stack would destroy all of the transuranics and long-lived fission products that are produced by a GWe reactor [1]. This capability offers the opportunity to close the nuclear fuel cycle and provide a path to green nuclear energy.

  3. A high-current rail-type gas switch with preionization by an additional corona discharge

    NASA Astrophysics Data System (ADS)

    Antipov, E. I.; Belozerov, O. S.; Krastelev, E. G.

    2016-12-01

    The characteristics of a high-current rail-type gas switch with preionization of the gas (air) in a spark gap by an additional corona discharge are investigated. The experiments were performed in a voltage range of 10-45 kV using a two-electrode switch consisting of two cylindrical electrodes with a diameter of 22 mm and a length of 100 mm and a set of laterally located corona-discharge needles. The requirements for the position and size of the needles are defined for which a corona discharge is ignited before a breakdown of the main gap and does not change to a sparking form, and the entire length of the rail electrodes is efficiently used. The fulfillment of these requirements ensures stable operation of the switch with a small variation of the pulse breakdown voltage, which is not more than 1% for a fixed voltage-pulse rise time in the range from 150 ns to 3.5 μs. A short delay time of the switch breakdown makes it possible to control the two-electrode switch by an overvoltage pulse of nanosecond duration.

  4. Magnetic field measurements of quadrupoles in the High-Current Experiment

    NASA Astrophysics Data System (ADS)

    Seidl, P. A.; Kireeff Covo, M.; Baca, D.; Faltens, A.; Molvik, A. W.; Ritchie, G.; Sabbi, G.; Shuman, D.

    2005-05-01

    The High-Current Experiment (HCX) at Lawrence Berkeley National Laboratory is part of the US program to explore heavy-ion beam transport at a scale representative of the low-energy end of an induction linac driver for fusion energy production. Four pulsed magnetic quadrupoles are being used to study gas and electron effects with a 0.2 A, 1-MeV K + beam. The magnets, originally designed and built for a prototype pulsed magnetic quadrupole array, have an elliptical beam tube (6×10 cm) and iron yoke. The magnet coil and field length are ≈31 cm, and operating gradients are 10-40 T/m. To establish that the field quality of the prototype quadrupoles is satisfactory for the experiments, a 1-cm pickup loop was used to measure the flux Br( θ) at the magnet mid-plane and also at the lead and return ends. A longer probe was used to measure the integrated flux of B θ( θ) along the magnet. The field quality appears satisfactory for the short transport experiments through these quadrupoles.

  5. A high-current rail-type gas switch with preionization by an additional corona discharge

    SciTech Connect

    Antipov, E. I.; Belozerov, O. S.; Krastelev, E. G.

    2016-12-15

    The characteristics of a high-current rail-type gas switch with preionization of the gas (air) in a spark gap by an additional corona discharge are investigated. The experiments were performed in a voltage range of 10–45 kV using a two-electrode switch consisting of two cylindrical electrodes with a diameter of 22 mm and a length of 100 mm and a set of laterally located corona-discharge needles. The requirements for the position and size of the needles are defined for which a corona discharge is ignited before a breakdown of the main gap and does not change to a sparking form, and the entire length of the rail electrodes is efficiently used. The fulfillment of these requirements ensures stable operation of the switch with a small variation of the pulse breakdown voltage, which is not more than 1% for a fixed voltage-pulse rise time in the range from 150 ns to 3.5 μs. A short delay time of the switch breakdown makes it possible to control the two-electrode switch by an overvoltage pulse of nanosecond duration.

  6. Detection and clearing of trapped ions in the high current Cornell photoinjector

    NASA Astrophysics Data System (ADS)

    Full, S.; Bartnik, A.; Bazarov, I. V.; Dobbins, J.; Dunham, B.; Hoffstaetter, G. H.

    2016-03-01

    We have recently performed experiments to test the effectiveness of three ion-clearing strategies in the Cornell high intensity photoinjector: DC clearing electrodes, bunch gaps, and beam shaking. The photoinjector reaches a new regime of linac beam parameters where high continuous wave beam currents lead to ion trapping. Therefore ion mitigation strategies must be evaluated for this machine and other similar future high current linacs. We have developed several techniques to directly measure the residual trapped ions. Our two primary indicators of successful clearing are the amount of ion current removed by a DC clearing electrode, and the absence of bremsstrahlung radiation generated by beam-ion interactions. Measurements were taken for an electron beam with an energy of 5 MeV and continuous wave beam currents in the range of 1-20 mA. Several theoretical models have been developed to explain our data. Using them, we are able to estimate the clearing electrode voltage required for maximum ion clearing, the creation and clearing rates of the ions while employing bunch gaps, and the sinusoidal shaking frequency necessary for clearing via beam shaking. In all cases, we achieve a maximum ion clearing of at least 70% or higher, and in some cases our data is consistent with full ion clearing.

  7. Field Emission Properties of Carbon Nanotube Fibers and Sheets for a High Current Electron Source

    NASA Astrophysics Data System (ADS)

    Christy, Larry

    Field emission (FE) properties of carbon nanotube (CNT) fibers from Rice University and the University of Cambridge have been studied for use within a high current electron source for a directed energy weapon. Upon reviewing the performance of these two prevalent CNT fibers, cathodes were designed with CNT fibers from the University of Cincinnati Nanoworld Laboratory. Cathodes composed of a single CNT fiber, an array of three CNT fibers, and a nonwoven CNT sheet were investigated for FE properties; the goal was to design a cathode with emission current in excess of 10 mA. Once the design phase was complete, the cathode samples were fabricated, characterized, and then analyzed to determine FE properties. Electrical conductivity of the CNT fibers was characterized with a 4-probe technique. FE characteristics were measured in an ultra-high vacuum chamber at Wright-Patterson Air Force Base. The arrayed CNT fiber and the enhanced nonwoven CNT sheet emitter design demonstrated the most promising FE properties. Future work will include further analysis and cathode design using this nonwoven CNT sheet material to increase peak current performance during electron emission.

  8. Deformation of contact surfaces in a vacuum interrupter after high-current interruptions

    SciTech Connect

    Wang, Haoran; Wang, Zhenxing Zhou, Zhipeng; Jiang, Yanjun; Wang, Jianhua; Geng, Yingsan; Liu, Zhiyuan

    2016-08-07

    In a high-current interruption, the contact surface in a vacuum interrupter might be severely damaged by constricted vacuum arcs causing a molten area on it. As a result, a protrusion will be initiated by a transient recovery voltage after current zero, enhancing the local electric field and making breakdowns occur easier. The objective of this paper is to simulate the deformation process on the molten area under a high electric field by adopting the finite element method. A time-dependent Electrohydrodynamic model was established, and the liquid-gas interface was tracked by the level-set method. From the results, the liquid metal can be deformed to a Taylor cone if the applied electric field is above a critical value. This value is correlated to the initial geometry of the liquid metal, which increases as the size of the liquid metal decreases. Moreover, the buildup time of a Taylor cone obeys the power law t = k × E{sup −3}, where E is the initial electric field and k is a coefficient related to the material property, indicating a temporal self-similar characteristic. In addition, the influence of temperature has little impact on the deformation but has great impact on electron emission. Finally, the possible reason to initiate a delayed breakdown is associated with the deformation. The breakdown does not occur immediately when the voltage is just applied upon the gap but is postponed to several milliseconds later when the tip is formed on the liquid metal.

  9. Investigation of various equations of state for high current, pulsed power load modeling

    NASA Astrophysics Data System (ADS)

    Luginsland, John; Parkinson, Roland; Rigby, Fred; Toepfer, Alan

    2002-08-01

    A number of technologies utilize the increasing availability of modern pulsed power systems to produce high currents to resistively drive solid, metallic loads into the plasma state. Examples include ablation plasma deposition, circuit breakers, fuses, exploding and imploding wires, and high velocity jet disruption. One important feature in any computational model of these phenomena is the equation of state (EOS). The equations of state used in these models are typically as varied as the range of applications. In this work, using a segmented wire experiment performed at the Army Research Laboratory [1] as a benchmark, we investigate three equations of state [2-4]. We assess the merits of the EOS for both their physical accuracy and easy of use computationally. Finally, we comment on the availability of the information necessary to build the EOS, given the wide variety of materials that are used in this applied field. [1] C.E. Hollandsworth et al., J. Appl. Phys., vol. 84, no. 9, 4992-5000, 1998. [2] SESAME tables, LANL T-1 Division, Equation of State and Strength of Materials. [3] Zhukov, Demidov, and Ryabenko, Fiz. Metal. Metalloved., vol. 57, no. 2, 224-229, 1984. [4] Chittenden et al., Laser and Particle Beams, vol. 19, issue 3, 323-343, 2001, and references therein.

  10. Sharp burnout failure observed in high current-carrying double-walled carbon nanotube fibers

    NASA Astrophysics Data System (ADS)

    Song, Li; Toth, Geza; Wei, Jinquan; Liu, Zheng; Gao, Wei; Ci, Lijie; Vajtai, Robert; Endo, Morinobu; Ajayan, Pulickel M.

    2012-01-01

    We report on the current-carrying capability and the high-current-induced thermal burnout failure modes of 5-20 µm diameter double-walled carbon nanotube (DWNT) fibers made by an improved dry-spinning method. It is found that the electrical conductivity and maximum current-carrying capability for these DWNT fibers can reach up to 5.9 × 105 S m - 1 and over 1 × 105 A cm - 2 in air. In comparison, we observed that standard carbon fiber tended to be oxidized and burnt out into cheese-like morphology when the maximum current was reached, while DWNT fiber showed a much slower breakdown behavior due to the gradual burnout in individual nanotubes. The electron microscopy observations further confirmed that the failure process of DWNT fibers occurs at localized positions, and while the individual nanotubes burn they also get aligned due to local high temperature and electrostatic field. In addition a finite element model was constructed to gain better understanding of the failure behavior of DWNT fibers.

  11. Design of conduction cooling system for a high current HTS DC reactor

    NASA Astrophysics Data System (ADS)

    Dao, Van Quan; Kim, Taekue; Le Tat, Thang; Sung, Haejin; Choi, Jongho; Kim, Kwangmin; Hwang, Chul-Sang; Park, Minwon; Yu, In-Keun

    2017-07-01

    A DC reactor using a high temperature superconducting (HTS) magnet reduces the reactor’s size, weight, flux leakage, and electrical losses. An HTS magnet needs cryogenic cooling to achieve and maintain its superconducting state. There are two methods for doing this: one is pool boiling and the other is conduction cooling. The conduction cooling method is more effective than the pool boiling method in terms of smaller size and lighter weight. This paper discusses a design of conduction cooling system for a high current, high temperature superconducting DC reactor. Dimensions of the conduction cooling system parts including HTS magnets, bobbin structures, current leads, support bars, and thermal exchangers were calculated and drawn using a 3D CAD program. A finite element method model was built for determining the optimal design parameters and analyzing the thermo-mechanical characteristics. The operating current and inductance of the reactor magnet were 1,500 A, 400 mH, respectively. The thermal load of the HTS DC reactor was analyzed for determining the cooling capacity of the cryo-cooler. The study results can be effectively utilized for the design and fabrication of a commercial HTS DC reactor.

  12. Laser nitriding of iron: Nitrogen profiles and phases

    NASA Astrophysics Data System (ADS)

    Illgner, C.; Schaaf, P.; Lieb, K. P.; Schubert, E.; Queitsch, R.; Bergmann, H.-W.

    1995-07-01

    Armco iron samples were surface nitrided by irradiating them with pulses of an excimer laser in a nitrogen atmosphere. The resulting nitrogen depth profiles measured by Resonant Nuclear Reaction Analysis (RNRA) and the phase formation determined by Conversion Electron Mössbauer Spectroscopy (CEMS) were investigated as functions of energy density and the number of pulses. The nitrogen content of the samples was found to be independent of the number of pulses in a layer of 50 nm from the surface and to increase in depths exceeding 150 nm. The phase composition did not change with the number of pulses. The nitrogen content can be related to an enhanced nitrogen solubility based on high temperatures and high pressures due to the laser-induced plasma above the sample. With increasing pulse energy density, the phase composition changes towards phases with higher nitrogen contents. Nitrogen diffusion seems to be the limiting factor for the nitriding process.

  13. Excitation of atomic nitrogen by electron impact

    NASA Technical Reports Server (NTRS)

    Stone, E. J.; Zipf, E. C.

    1972-01-01

    Absolute cross sections were measured for the excitation of the N I(1134, 1164, 1168, 1200, 1243, and 1743 A) multiplets by electron impact on atomic nitrogen. The presence of vibrationally excited molecular nitrogen in the discharged gas was confirmed, and its effect on the measurements is discussed. The ratio of the oscillator strengths of the 1200 and 1134 A resonance transitions is presented, as well as the branching ratio for the N I(1311/1164 A) multiplets. Striking differences in the distribution of intensity between the spectra of atomic nitrogen and molecular nitrogen excited by energetic electrons suggest an optical method for measuring the density of atomic nitrogen in the upper atmosphere.

  14. High Current ESD Test of Advanced Triple Junction Solar Array Coupon

    NASA Technical Reports Server (NTRS)

    Wright, K. H.; Schneider, T. A.; Vaughn, J. A.; Hoang, B.; Wong, F.

    2014-01-01

    A test was conducted on an Advanced Triple Junction (ATJ) coupon that was part of a risk reduction effort in the development of a high-powered solar array design by SSL. The ATJ coupon was a small, 4-cell, two-string configuration that has served as the basic test coupon design used in previous SSL environmental aging campaigns. The coupon has many attributes of the flight design; e.g., substrate structure with graphite face sheets, integrated by-pass diodes, cell interconnects, RTV grout, wire routing, etc. The objective of the present test was to evaluate the performance of the coupon after being subjected to induced electrostatic discharge testing at two string voltages (100 V, 150 V) and four array current (1.65 A, 2.0 A, 2.475 A, and 3.3 A). An ESD test circuit, unique to SSL solar array design, was built that simulates the effect of missing cells and strings in a full solar panel with special primary arc flashover circuitry. A total of 73 primary arcs were obtained that included 7 temporary sustained arcs (TSA) events. The durations of the TSAs ranged from 50 µs to 2.9 ms. All TSAs occurred at a string voltage of 150 V. Post-test Large Area Pulsed Solar Simulator (LAPSS), Dark I-V, and By-Pass Diode tests showed that no degradation occurred due to the TSA events. In addition, the post-test insulation resistance measured was > 50 G-ohms between cells and substrate. These test results indicate a robust design for application to a high-current, high-power mission application.

  15. High Current ESD Test of Advanced Triple Junction Solar Array Coupon

    NASA Technical Reports Server (NTRS)

    Wright, Kenneth H., Jr.; Schneider, Todd A.; Vaughn, Jason A.; Hoang, Bao; Wong, Frankie

    2015-01-01

    A test was conducted on an Advanced Triple Junction (ATJ) coupon that was part of a risk reduction effort in the development of a high-powered solar array design by SSL. The ATJ coupon was a small, 4-cell, two-string configuration that has served as the basic test coupon design used in previous SSL environmental aging campaigns. The coupon has many attributes of the flight design; e.g., substrate structure with graphite face sheets, integrated by-pass diodes, cell interconnects, RTV grout, wire routing, etc. The objective of the present test was to evaluate the performance of the coupon after being subjected to induced electrostatic discharge testing at two string voltages (100 V, 150 V) and four array current (1.65 A, 2.0 A, 2.475 A, and 3.3 A). An ESD test circuit, unique to SSL solar array design, was built that simulates the effect of missing cells and strings in a full solar panel with special primary arc flashover circuitry. A total of 73 primary arcs were obtained that included 7 temporary sustained arcs (TSA) events. The durations of the TSAs ranged from 50 micros to 2.9 ms. All TSAs occurred at a string voltage of 150 V. Post-test Large Area Pulsed Solar Simulator (LAPSS), Dark I-V, and By-Pass Diode tests showed that no degradation occurred due to the TSA events. In addition, the post-test insulation resistance measured was > 50 G-ohms between cells and substrate. These test results indicate a robust design for application to a high-current, high-power mission application.

  16. High Current ESD Test of Advanced Triple Junction Solar Array Coupon

    NASA Technical Reports Server (NTRS)

    Wright, Kenneth H., Jr.; Schneider, Todd A.; Vaughn, Jason A.; Hoang, Bao; Wong, Frankie

    2014-01-01

    Testing was conducted on an Advanced Triple Junction (ATJ) coupon that was part of a risk reduction effort in the development of a high-powered solar array design by Space Systems/Loral, LLC (SSL). The ATJ coupon was a small, 4-cell, two-string configuration that has served as the basic test coupon design used in previous SSL environmental aging campaigns. The coupon has many attributes of the flight design; e.g., substrate structure with graphite face sheets, integrated by-pass diodes, cell interconnects, RTV grout, wire routing, etc. The objective of the present test was to evaluate the performance of the coupon after being subjected to induced electrostatic discharge (ESD) testing at two string voltages (100 V, 150 V) and four array currents (1.65 A, 2.0 A, 2.475 A, and 3.3 A). An ESD test circuit, unique to SSL solar array design, was built that simulates the effect of missing cells and strings in a full solar panel with special primary arc flashover circuitry. A total of 73 primary arcs were obtained that included 7 temporary sustained arcs (TSA) events. The durations of the TSAs ranged from 50 micro-seconds to 2.75 milli-seconds. All TSAs occurred at a string voltage of 150 V. Post-test Large Area Pulsed Solar Simulator (LAPSS), Dark I-V, and By-Pass Diode tests showed that no degradation occurred due to the TSA events. In addition, the post-test insulation resistance measured was > 50 G-ohms between cells and substrate. These test results indicate a robust design for application to a high-current, high-power mission.

  17. A time-resolved imaging and electrical study on a high current atmospheric pressure spark discharge

    NASA Astrophysics Data System (ADS)

    Palomares, J. M.; Kohut, A.; Galbács, G.; Engeln, R.; Geretovszky, Zs.

    2015-12-01

    We present a time-resolved imaging and electrical study of an atmospheric pressure spark discharge. The conditions of the present study are those used for nanoparticle generation in spark discharge generator setups. The oscillatory bipolar spark discharge was generated between two identical Cu electrodes in different configurations (cylindrical flat-end or tipped-end geometries, electrode gap from 0.5 to 4 mm), in a controlled co-axial N2 flow, and was supplied by a high voltage capacitor. Imaging data with nanosecond time resolution were collected using an intensified CCD camera. This data were used to study the time evolution of plasma morphology, total light emission intensity, and the rate of plasma expansion. High voltage and high current probes were employed to collect electrical data about the discharge. The electrical data recorded allowed, among others, the calculation of the equivalent resistance and inductance of the circuit, estimations for the energy dissipated in the spark gap. By combining imaging and electrical data, observations could be made about the correlation of the evolution of total emitted light and the dissipated power. It was also observed that the distribution of light emission of the plasma in the spark gap is uneven, as it exhibits a "hot spot" with an oscillating position in the axial direction, in correlation with the high voltage waveform. The initial expansion rate of the cylindrical plasma front was found to be supersonic; thus, the discharge releases a strong shockwave. Finally, the results on equivalent resistance and channel expansion are comparable to those of unipolar arcs. This shows the spark discharge has a similar behavior to the arc regime during the conductive phase and until the current oscillations stop.

  18. THE POTENTIAL FOR NEUTRINO PHYSICS AT MUON COLLIDERS AND DEDICATED HIGH CURRENT MUON STORAGE RINGS

    SciTech Connect

    BIGI,I.; BOLTON,T.; FORMAGGIO,J.; HARRIS,D.; MORFIN,J.; SPENTZOURIS,P.; YU,J.; KAYSER,B.; KING,B.J.; MCFARLAND,K.; PETROV,A.; SCHELLMAN,H.; VELASCO,M.; SHROCK,R.

    2000-05-11

    Conceptual design studies are underway for both muon colliders and high-current non-colliding muon storage rings that have the potential to become the first true neutrino factories. Muon decays in long straight sections of the storage rings would produce uniquely intense and precisely characterized two-component neutrino beams--muon neutrinos plus electron antineutrinos from negative muon decays and electron neutrinos plus muon antineutrinos from positive muons. This article presents a long-term overview of the prospects for these facilities to greatly extend the capabilities for accelerator-based neutrino physics studies for both high rate and long baseline neutrino experiments. As the first major physics topic, recent experimental results involving neutrino oscillations have motivated a vigorous design effort towards dedicated neutrino factories that would store muon beams of energies 50 GeV or below. These facilities hold the promise of neutrino oscillation experiments with baselines up to intercontinental distances and utilizing well understood beams that contain, for the first time, a substantial component of multi-GeV electron-flavored neutrinos. In deference to the active and fast-moving nature of neutrino oscillation studies, the discussion of long baseline physics at neutrino factories has been limited to a concise general overview of the relevant theory, detector technologies, beam properties, experimental goals and potential physics capabilities. The remainder of the article is devoted to the complementary high rate neutrino experiments that would study neutrino-nucleon and neutrino-electron scattering and would be performed at high performance detectors placed as close as is practical to the neutrino production straight section of muon storage rings in order to exploit beams with transverse dimensions as small as a few tens of centimeters.

  19. Optimization of BSCCO/Ag-tapes for high current and for AC-applications

    NASA Astrophysics Data System (ADS)

    Haessler, W.; Rodig, Ch.; Schubert, M.; Trinks, H. P.; Haas, V.; Holzapfel, B.; Leghissa, M.; Fischer, B.

    2002-08-01

    For improving the application possibilities of (Bi,Pb) 2Sr 2Ca 2Cu 3O x/Ag-tapes in cables or transformers it is necessary to increase the overall critical current density and to develop tapes with low AC-losses. For enhancing the overall critical current density je, the filling factor of the tapes was increased from 28% to 38%, and the thermo-mechanical treatment (TMT) process was optimised. Due to the large number of parameters of the TMT process (at least temperature, oxygen partial pressure and dwell time of three different treatment steps, if the temperature ramps, and the parameters of the intermediate rolling procedures are kept constant) the application of the method of design of experiments can be very useful. The number of experiments can be reduced and the method gives additional information about the process, especially the statistical significance of the process parameters and about interactions between different parameters. As a result of these investigations je could be enhanced to 10 kA cm -2 ( Ic=90 A). Twisted tapes have been developed in order to reduce the AC-losses. The influence of twist pitch on the critical current density and the AC-losses has been studied. In twisted tapes with a twist pitch of 10 mm AC-losses as low as 0.45 mW A -1 m -1 (0.1 T∥, 50 Hz) and overall current densities up to je=4.5 kA cm -2 were measured.

  20. Dissociation and excitation coefficients of nitrogen molecules and nitrogen monoxide generation

    SciTech Connect

    Uhm, Han S.; Na, Young H.; Choi, Eun H.; Cho, Guangsup

    2013-08-15

    The excitation coefficient α{sub N2} is calculated for the excited metastable level of N{sub 2}(A{sub 3}Σ{sub u}{sup +}) in nitrogen molecules. In addition, the dissociation coefficient of nitrogen molecules is investigated by making use of the Boltzmann distribution of the electrons in atmospheric plasmas. The excitation and electron-impact dissociation coefficients of nitrogen molecules are analytically expressed in terms of the electron temperature T{sub e} for evaluations of the reactive oxygen and nitrogen species in atmospheric plasmas. As an application example of these coefficients, the nitrogen monoxide generation through a microwave torch is carried out for a development of medical tool. The nitrogen monoxide concentration from a microwave plasma-torch can be easily controlled by the nitrogen flow rate, mole fraction of the oxygen gas, and the microwave power. A simple analytic expression of the nitrogen monoxide concentration is obtained in terms of the oxygen molecular density and gas flow rate. The experimental data agree remarkably well with the theoretical results from the analytical expression. A microwave nitrogen-torch can easily provide an appropriate nitrogen monoxide concentration for the wound healings.